Student Abstracts: Physics

1-D Simulations of Metallic Foams Heated by Ion Beam Energy Deposition. ALEX ZYLSTRA (Pomona College, Claremont, CA, 91711) JOHN BARNARD (Lawrence Berkeley National Laboratory, Berkley, CA, 94720)

One dimensional simulations of various initial average density aluminum foams (modeled as slabs of solid metal separated by low density regions) heated by volumetric energy deposition have been conducted with a Lagrangian hydrodynamics code, DISH (Deeply Simplified Hydrodynamics by R. More), using a van der Waals equation of state (EOS). The resulting behavior has been described to facilitate the design of future warm dense matter (WDM) experiments. Deposition in the simulations ranges from 15 to 30 kJ/g total energy and from 0.075 to 0.9 ns total pulse length, resulting in temperatures from 1 to 4 eV. The peak temperature reached in the foam was found to be greater than linearly dependent on the energy deposition, increasing with increasing density to a peak at approximately 75% solid initial average density and decreasing rapidly with increasing density beyond that peak, and essentially independent of the pulse length for pulse lengths shorter than the macro hydro time, approximately 1 ns. The peak pressure increases rapidly with increasing density, increases with increasing energy, and is roughly independent of the pulse length for lengths on the order of the macro hydro time. For pulse lengths of approximately the hydro time for one slab of the foam (~0.1 ns) an increase in the maximum pressure is observed. The expansion velocity is proportional to the density for pulses on the order of the hydro time of one slab of the foam; for longer pulses a dramatic increase in the expansion velocity is observed at approximately 75% solid density initial. We find that the homogenization time of the foam increases with increasing pulse length, and the remaining inhomogeneities in the homogenized foam decrease with increasing density. These results will help future experiments examine the equation of state in the WDM regime.

3 Inch Double GEM for X-Ray Fluorescent Detector. DERREK ANDERSON and JAMEL GRAY (Southern University, Baton Rouge, LA, 70813) DR. D. PETER SIDDONS (Brookhaven National Laboratory, Upton, NY, 11973)

Two 3-inch diameter gas electron multipliers (GEM) are used to build a high gain X-Ray gas detector for Extended X-Ray Absorption Fine Structures (EXAFS). The X-Ray ionizes the gas and the electrons are drifted towards the first GEM. The strong electric field in the GEM multiplies electrons by impact ionization. The second stage GEM further amplifies the electrons by the same process. The advantage of the double GEM is to provide two stages of electron amplification. This improves the signal magnitude without the introduction of noise. The charge collected from the second GEM is connected to a Keithley Amplifier. We have tested the Double GEM to detect dilute amounts of Mn and Fe in an arbitrary tree leaf.

A Comparative Study of GEM Foils from Tech Etch and CERN. JONATHAN HERSTOFF (Muhlenberg College, Allentown, PA, 18104) CRAIG WOODY (Brookhaven National Laboratory, Upton, NY, 11973)

Gas Electron Multipliers (GEMs) were originally developed at CERN and are now being used in applications such as charged particle tracking. They consist of a thin polyimide foil which is copper clad on both sides and contain a large number of small holes extending through the foil. When high voltage is applied across the copper electrodes, a large electric field is developed inside the holes, which is used to produce gas gain. Different methods of manufacturing these GEMs can potentially be determinative of how the GEMs behave under high voltage. In this study, a company called Tech Etch produced three different batches of foils, each using a different chemical etching method. Although the measurements of gain versus time were varied widely from foil to foil, contrary to what was expected, there does appear to be a correlation between the size of the holes and the performance of the GEM. In general, foils with holes that have a larger polyimide area exposed tended to exhibit poorer gain stability than those with less exposed polyimide.

A Systematic Study of the Effect of Magnetized Oxygen on a Photon Beam. ALISHIA FERRELL (Florida A & M University, Tallahassee, FL, 32307) DR. CAROL Y. SCARLETT (Brookhaven National Laboratory, Upton, NY, 11973)

A systematic study of the effects of oxygen oscillation on a laser beam propagating through an electromagnetic field (EMF) was deemed necessary due to the physical set up of the main experiment concerning space time curvature. The control or "shunt" measurements for the main experiment were made by propagating the laser outside of a vacuum chamber along side a super conducting magnet. However, this caused the beam to travel extremely close to the lead wires. This raised the question, "Was the oxygen movement being created by EMF deviating the laser beam enough to corrupt the control data". In order to see if the oxygen was significantly changing the data a systematic study had to be done. To perform this systematic study a 514 nm helium neon laser generator, several focusing and defocusing optical lenses, a quad cell photo-receiver, and a quadrapole magnet capable of oscillating its current were used. After doing a number of calibrations on the photo receiver we were able to ramp a 10 Amp electromagnetic field using alternating current through a quadrapole on the averages of events given. While the light was hitting the photo-receiver data was being collected from a data acquisition system. Once the data was done being colleted it was converted into text files. With these numbers a FORTRAN program was created using fast Fourier transforms (fft), which showed that there was a bit of movement in the X direction which caused a noticeable signal. Further studies must be done so that we can insure that this signal that we see is not just by coincidence.

A Systematic Study of the Effect of Magnetized Oxygen on a Photon Beam. JOSEPH HEARD (Community College of Philadelphia, Philadelphia, Pa, 19130) CAROL SCARLETT (Brookhaven National Laboratory, Upton, NY, 11973)

A systematic study of the effect of oxygen oscillation due to a paramagnetic effect has on a laser beam propagating through a electromagnetic field (EMF) was deemed necessary due to the physical set up of the experiment concerning space time curvature. The control or "shunt" measurements for the main experiment were taken by propagating the laser outside of the vacuum chamber along the side. However, this caused the beam to travel extremely close to the lead wires of the super conducting electromagnet. This raised the question, "was the oxygen movement being created by EMF of the lead wires deviating the laser beam enough to corrupt the control data." To perform a systematic study of this concern we used a 514 nm helium neon laser generator, several focusing and defocusing optical lenses, a quad cell photo receiver, and a Quadra-pole magnet capable of oscillating current. Also, FORTRAN computer programs containing FFT’s were used to accomplish the Fourier analysis necessary for data analysis. The systematic study was conducted by propagating the laser through an EMF field ramped at 80 MHz. Then different amounts of oxygen were exposed to the field. The photo receiver then tracked the laser beam movement. The results were then analyzed to see if the oxygen oscillation was visible in the data. We observed a large peak in the "x" (horizontal) direction. This might indicate that the signal seen may be partially due to magnetized oxygen. However, further studies must be conducted before conclusive results can be reached. Future studies would include: varying the type of magnet, adjusting the percentage of gaseous oxygen flowing through the magnet, and changing the position of the magnet in relation to the photon beam.

A Systematic Study of the Effect of Magnetized Oxygen on a Photon Beam. RACHAEL MILLINGS (Suffolk County Community College, Selden, NY, 11784) DR. CAROL SCARLETT (Brookhaven National Laboratory, Upton, NY, 11973)

When light is propagated through a ramped magnetic field into a photoreceiver in the presence of air, there exists a possibility that the observed laser beam deviation is due to the paramagnetic behavior of gaseous oxygen in the air. If the signal observed is not negligible, then the deviation cannot be used as a shunt for beam deviation due to light propagated in a vacuum. The purpose of this systematic study is to determine the significance of gaseous oxygen's magnetic susceptibility relative to the observed beam deviation. A photon beam from a 514 nm HeNe laser generator was propagated through a defocusing lens and a focusing lens to focus the beam; two mirrors were then used to reflect the beam through a quadrupole magnet and into a photoreceiver. As an alternating electric current of 10 amperes was directed through the magnet, the amount of light entering the photoreceiver was measured using a data acquisition system to interface with the photoreceiver and a computer. After the data was converted into text files, a programming language, FORTRAN, was used to write a code that analyzed the data by the method of fast Fourier transforms. On a graph of the amplitude of the light as a function of time, a signal was observed at the same frequency as that at which the current in the magnet was alternating, as expected. While the signal was relatively large, future studies must be conducted to yield conclusive results. This systematic study is part of a larger experiment researching the space-time curvature of light passing through a magnetic field in a vacuum as a possible validation of physical theory which postulates the existence of gravity in the absence of mass.

Analysis of Beta-Decay of 51,52K. EMILY JACKSON (Knox College, Galesburg, IL, 61401) MICHAEL CARPENTER (Argonne National Laboratory, Argonne, IL, 60439)

The beta decay of ^51,52K has been analyzed from data taken at TRIUMF (TRI-University Meson Facility) in Vancouver, Canada. The high purity Ge detectors were calibrated with respect to energy and efficiency using standard calibration sources (¹⁵²Eu, ¹³³Ba, and ⁵⁷Co). The peaks in the beta decay spectra from the two K isotopes were identified and the energy and intensity were fitted. These results were compared to a table of energy and intensity published in a paper by F. Perrot et al. to check for consistency: they were found to agree with the published results. From another data set obtained at the ATLAS accelerator at Argonne with the Gammasphere array, the level scheme for ⁵²Ti was established and expanded a great deal in comparison to the known level scheme. Any further research into the neutron-rich nuclei will require a more powerful accelerator than the accelerator used in this experiment in addition to a radioactive beam.

Analysis of Consistency in Channel Pedestal Readings for the Track Imaging Cerenkov Experiment (TrICE) Camera as a Function of Temperature and Time. ANA CHACHIAN (Florida International University, Miami, FL, 33199) KAREN BYRUM (Argonne National Laboratory, Argonne, IL, 60439)

Track Imaging Cerenkov Experiment (TrICE) is a telescope prototype on site at Argonne National Laboratory. Its camera is composed of an array of 16 high definition multi-anode photomultiplier tubes (MAPMTs) that give an angular pixel spacing (0.08deg) better than most existing Cerenkov shower detecting telescopes (~0.15deg). The TrICE telescope is a testbed for the development of a next-generation gamma-ray telescope. TrICE has been observing cosmic rays since earlier this year. The stability of the TrICE camera performance was analyzed through the study of background noise pedestals recorded by its channels to determine if these are constant under the background sky. The method involved generating histograms that compared the pedestal signals for each channel over different days, times, and temperatures, using a C++ interfaced with Root macro. The results of this analysis concluded that the pedestal means were constant over a variety of conditions and are therefore reliable to reproduce accurate Cerenkov signals. The result of this analysis is the first step in understanding the data taken by the camera. Further steps to this end include research of each channel’s gain as a function of these pedestal fluctuations.

Analysis of Nuclear Semi-Inclusive Deep Inelastic Scattering Events for Charged Pions Using FORTRAN. BRYAN RAMSON (Howard University, Washington, DC, 20059) KAWTAR HAFIDI (Argonne National Laboratory, Argonne, IL, 60439)

Because of the nature of the strong interaction, it is impossible to directly observe free quarks. Therefore their fundamental properties must be studied through the results of deep-inelastic scattering of electrons off stationary nuclei. The Continuous Electron Beam Accelerator (CEBA) at the Thomas Jefferson National Accelerator Facility (JLab) provides an electron beam of sufficient energy (5.014 GeV) to study such reactions. The electron beam was used on targets of deuterium, carbon, iron, and lead. Particles produced in the reactions were detected by the CEBA Large Acceptance Spectrometer (CLAS) and analysis of the data is being conducted through collaboration of teams from JLab and Argonne National Laboratory. One area of analysis is the production of pions in the nuclear medium and the relationship that their production have with the properties of quark propagation in the nuclear medium. The analysis was not completed.

Analysis of the Particle Identification Capabilities of the Proposed Helical Orbit Spectrometer (HELIOS). ZACHARY GRELEWICZ (University of Chicago, Chicago, IL, 60637) DR. BIRGER BACK (Argonne National Laboratory, Argonne, IL, 60439)

In order to study nuclear reactions involving short lived nuclei, inverse kinematic reactions must be used. Therefore, a novel spectrometer, HELIOS, has been designed to optimize the detection of particles in inverse kinematic reactions. In principle, the cyclotron period of an ejectile traveling along a helical orbit in a uniform magnetic field corresponds to a unique charge-to-mass ratio. However, if the ejectile is intercepted before completing a full period, the extended geometry of the detector may be used to determine not only a charge-to-mass ratio, but a unique mass. Using the Geant4 toolkit provided by the European Organization for Nuclear Research (CERN), as well as analytical techniques, the data collected by the detector from proton, deuteron, triton, helium-3, and alpha particle ejectiles were simulated. Then a program for identifying particles based on time-of-flight, energy of impact, and distance traveled along the axis of the detector, as well as an analysis of the characteristics of unidentifiable particles, was developed using the C++ programming language, with visualizations provided by CERN's ROOT system. It was found that successful particle identification depends most strongly on the lab angle of the ejected particles, with different lab angle ranges and acceptances for the five particles. Most particles may be identified by their location in the phase space, with few areas of phase space containing overlapping particles.

Analysis of the CDF II Data in Search of the Higgs Boson Decaying to Two Photons. CALLIE DEMAY (University of Illinois, Urbana-Champaign, IL, 61820) CRAIG GROUP (Fermi National Accelerator Laboratory, Batavia, IL, 60510)

Although the Standard Model is unbelievably accurate, the one fundamental aspect needed to complete the model, a massive particle called the Higgs Boson, has not yet been discovered. In this investigation, we searched for a non-Standard Model, fermiophobic Higgs, which would decay to two photons. This decay mode is predicted to have a very small branching fraction according to the Standard Model; however, some models predict a higher branching fraction. We initially optimized selection criteria in order to become as sensitive as possible to the signal region. Using the 2fb^-1 of data provided by Fermilab’s Tevatron and collected by the Collider Detector at Fermilab (CDF) experiment, we were unable to see a signal for the Higgs; therefore, the focus of our research shifted to placing a limit on the cross section for the Higgs in the fermiophobic model. We were able to place a lower limit of 99 GeV on the mass of the fermiophobic Higgs. This limit is currently the best in the world for a hadron collider. The previous limits at Fermilab included one by CDF at 82 GeV, and one by DZero at about 90 GeV. However, the world’s best limit of 109.7 GeV was placed by the Large Electron-Positron Collider (LEP) in Switzerland. Although we were not able to find a Higgs signal, the techniques used to improve sensitivity to photon events will be useful in the next generation of collider experiments, which will be more sensitive to the small branching fraction of diphoton events.

Analysis of the Directivity of a Defective R-F (Radio- Frequency) Coupler Using a Network Analyzer. ZEPHRA BELL (Southern University and A & M College, Baton Rouge, LA, 70807) DR. TERRENCE REESE (Fermi National Accelerator Laboratory, Batavia, IL, 60510)

The R-F couplers that we tested were used in a project called HINS at Fermi National Accelerator Laboratory ( Fermilab). HINS stands for High Intensity Neutrino Sources. These couplers are arranged in a transmission line at Fermilab. The couplers are crucial for the transfer of power in an R-F cavity. However, one of the couplers in the transmission line seemed to be defective. The high power signal down the "line" in the reflected power was too low from that in the forward port. It was measured to be only 13 dB when it should have been 60 dB. Therefore, initially, three different methods were used to test the defective coupler: 1) The connector cables attenuation was measured. Connector cables are used to attach the port of the coupler to other pieces of the R-F cavity. The cable attenuation and the reflection load were good. This meant that the coupler did not have power flowing through faulty cables. 2) Low power in the switch was generated. This still reflected a low signal of 13 dB. 3) Finally, the coupler was physically removed and tested directly. It still reflected a low signal of 13 dB. Hence, the coupler was brought to our team to see if we could determine the defects of the coupler through rigorous testing of the ports and internal modifications.

Analysis of X-Ray Spectra Emitted from the VENUS ECR Ion Source. JANILEE BENITEZ (California State University, East Bay, Hayward, CA, 94542) DANIELA LEITNER (Lawrence Berkeley National Laboratory, Berkley, CA, 94720)

The Versatile Electron Cyclotron resonance ion source for NUclear Science, VENUS, produces its record breaking ion beam currents and high charge state distributions because it uses strong magnetic fields to confine the plasma and high microwave frequencies to heat it. The magnetic fields are produced using liquid helium cooled superconducting coils. While in operation, VENUS produces significant quantities of bremsstrahlung, in the form of x-rays, through two processes: 1) electron-ion collisions within the plasma, and 2) electrons are lost from the plasma and collide with the plasma chamber wall and release energy. The energy lost by electron collisions with the chamber wall presents a significant heat load on the cryostat needed to keep the coils superconducting. In order for VENUS to reach its maximum operating potential at 10kW of 28GHz microwave heating frequency, the heat load posed by the emitted bremsstrahlung must be understood. A code has been written, using the Python programming language, to analyze the recorded bremsstrahlung spectra. The code outputs a spectral temperature and total integrated count number corresponding to each spectra. Bremsstrahlung spectra are analyzed and compared by varying two parameters: 1) the heating frequency, 18 and 28GHz, and 2) the magnetic field gradient, 44% and 70%, at the electron resonant zone.

Application to Determine and Control Twiss Parameters of the SNS Accelerator Beam. JENS VON DER LINDEN (University of Pennsylvania, Philadelphia, PA, 19104) SARAH COUSINEAU (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

The accelerator ion beam at the Spallation Neutron Source (SNS) is repeatedly focused and defocused by a series of quadruple magnets as it travels to the target to create neutrons by means of spallation. Physicists are interested in characterizing the accelerator beam in order to understand and improve the focusing and transport of the beam. Wire scans are employed to measure the traverse density profile of the beam. With a minimum of 3 distinct wire scans, the ion beam Twiss parameters, which characterize the phase space properties of the beam, can be determined. In this project, a Graphical User Interface (GUI) Application was developed in JAVA to automate the determination of Twiss parameters from the wire scan data files and to determine how quadruples should be varied to change the Twiss parameters at multiple arbitrary locations. The software is coded within the XAL framework, an existing JAVA library developed at the SNS accelerator which is used for all GUI-based physics software applications. A major contribution of the JAVA GUI developed in this project is that it is generally applicable to any area of the accelerator containing a minimum of 3 wire scanners. Existing applications were tied to specific parts of the accelerator. Twiss results can be saved and compared through graphing and averaging. As the SNS is a high intensity accelerator which requires strict control over the beam losses, it is very important that the beam in the accelerator be transported according to the optimum design configuration. Any deviation from the optimum transport configuration can lead to beam loss that can limit the obtainable beam power in the accelerator. This application will aid in measuring the beam state at any point in the accelerator, and will subsequently allow a user to make adjustments to the beam state in order to restore the optimum configuration and ensure well controlled beam transport.

Assembly of a Time-Correalted Single Photon Counting Experimental Setup. SEAN SWEETNAM (Carleton College, Northfield, MN, 55057) RANDY ELLINGSON (National Renewable Energy Laboratory, Golden, CO, 89401)

Recent developments in nanotechnology have created materials capable of improving the efficiency of solar cells, provided the basic photophysics involved are well understood. To properly characterize and understand the charge carrier processes which occur in nanomaterials, it is necessary to use very fast light gathering techniques, with time resolutions as small as tens of picoseconds. Time-Correlated Single Photon Counting (TCSPC) is such a technique, capable of providing sufficiently fast time resolution to resolve important process in materials by utilizing fast response mechanisms of detectors and electronic components, and by using efficient trigger timing. TCSPC also extends the range of observable photoluminescence with its long wavelength and low power detection capabilities. The goal of the work discussed in this paper is to develop a TCSPC system unique in its time resolution and range of detection. In this paper the principles and components of TCSPC are described, and the preparation of a TCSPC experimental setup is discussed, in particular noting the systematic errors encountered and their solutions. The system was run with a Tsunami Ti:Sapphire laser operating at 864-868 nm with a Si Avalanche Photodiode (APD) detector, yielding a time resolution of less than 800 ps. Emission lifetime measurements of 3.6 nm diameter PbS quantum dots with this setup yield a lifetime greater than 1300 ns; this value varied for different emission wavelengths 965-1030 nm. Because the time resolution is more than three orders of magnitude shorter than the lifetime of PbS quantum dots, it is concluded that the system is sufficiently fast for typical carrier lifetime characterization. Further development of the system will be necessary to improve the time resolution and infrared capabilities of the system; in particular the inclusion of an InGaAs APD in the system will decrease the time resolution, and increase the detection range to as far as 1600 nm. A flexible setup permitting fast switches between the InGaAs and Si detectors will increase the usefulness of the setup by increasing the full range of sensitivity to 400-1600 nm. Further experimentation will be necessary to determine the cause of the emission lifetime variation associated with emission wavelength.

Automation of the Vacuum System along the Advanced Penning Trap Beam Line. LAYRA REZA (University of Texas at El Paso, El Paso, TX, 79968) GUY SAVARD, PHD (Argonne National Laboratory, Argonne, IL, 60439)

A key component in the Canadian Penning Trap (CPT) mass spectrometer, located in the Argonne Tandem-Linear Accelerator System, is an Advanced Penning Trap (APT) filled with gas, the purpose of which is to purify an ion sample before mass measurements. The APT is one of few components where gas is required; however, high precision mass measurements must take place in an ultra high vacuum (UHV) environment, including the APT, to avoid contamination of the ions. An UHV environment is required continuously, even when operators are not present. Then, the goal of the project is to have complete automation of the APT beam line in a way that is fast and error free. The achievement of high vacuum involves a vacuum system composed of ion and thermocouple gauges, mechanical and turbomolecular pumps and pneumatic and solenoid valves. These components can be automated with the use of a Programmable Logic Controller (PLC). To achieve automation in the APT experimental setup, several steps need to be completed. First, a procedure for the safe operation of all the components has been created, a detailed list of components has been constructed, and the missing parts have been ordered. Moreover, a program in ladder logic mode has been written to control the system and avoid both operator and instrumental errors that might damage the system or its components. The project will continue until all new components are installed and wired into the PLC.

Building X-ray Diffraction Calibration Software. JOSHUA LANDE (Marlboro College, Marlboro, VT, 05344) SAMUEL WEBB (Stanford Linear Accelerator Center, Stanford, CA, 94025)

CMOS Monolithic Pixel Sensors with in-pixel CDS and fast readout for the ILC Vertex Tracker. TERRI SCOTT (New York University, New York City, NY, 10003) MARCO BATTAGLIA (Lawrence Berkeley National Laboratory, Berkley, CA, 94720)

The International Linear Collider (ILC) Vertex Tracker requires detectors of new design in order to meet its physics requirements in terms of material, accuracy and readout speed. The detectors must be sufficiently thin, in order that incident particles may pass through several layers of sensors without substantial scattering. Readout should be fast enough that occupancy caused by machine-induced background does not spoil the track pattern recognition. Monolithic silicon pixel sensors provide a solution to these constraints due to their high resolution and ability to be thinned to several tens of micrometers. One detector currently under testing is the LDRD2 chip, designed and developed at the Lawrence Berkeley National Laboratory. The detector features 20 x 20 µm pixels with in-pixel charge storage for correlated double sampling, a technique by which the difference is taken between a reference and the pixel signal voltage. Half of the chip utilizes 5 x 5 µm diodes, and 3 x 3 µm diodes in the second half. To characterize its performance, lab tests were conducted using a pulsed laser and a Fe55 x-ray source. In particular, the chip was readout at several frequencies to determine the effect of the readout speed and the charge integration time on efficiency and noise. It was found that the LDRD2 chip responds to both laser pulses and incident x-rays at readout frequencies up to the highest design frequency of 25MHz. This work is part of an ongoing R&D program at LBNL which will continue to investigate the LDRD2 and further generations of pixel sensors.

Coarsening of Superconducting Froths. ANDREW FIDLER (Albion College, Albion, MI, 49224) RUSLAN PROZOROV (Ames Laboratory, Ames, IA, 50011)

The structure and dynamics of foams and froths has been a subject of intense interest due to the desire to understand the behavior of complex systems, when topological complexity prohibits exact derivations based on minimum energy arguments. Though exact solutions have proven unattainable, general laws that govern the overall structural evolution have been developed. This is particularity true in the case of two-dimensional foams consisting of arrays of polygonal shaped cells with three edges per vertex. The mathematics for describing the cellular evolution in this system has proven to be surprisingly simple in form, and it applies only to the system as a whole. This gives a hope that, while the behavior of individual cells may be difficult to analyze, the overall system can be described by relatively simple rules. Using magneto-optical imaging, it was recently demonstrated that the intermediate state in superconducting lead exhibits patterns that appears to be very similar to soap foams. While visually alike, physically these systems are quite different. In conventional foams the foaming agent is always some form of matter, while in the intermediate state in lead the structure is characterized by superconducting and normal state regions. In this project, we have investigated these analogies and seen whether the general equations mentioned above apply equally as well to magnetic superconducting foams. It has been determined that laws describing foam evolution, such as von Neumann's law, work remarkably well for superconducting froth, but some parameters are different when compared to conventional foams. The biggest difference between these two systems is the agent that provides the foaming in superconducting lead, the superconducting region, decreasing as the field evolves, whereas in conventional soaps the amount of the foaming agent is constant. Nevertheless, the statistics of the polygons and structural dependence on the applied magnetic field and temperature have proven to be analogous to time. Topological transformations of the cells have also proven to be identical to conventional foams. This new type of superconducting foam could prove to help greatly to the insight into the general physics of foams, since the structure can be controlled to a greater extent by reversible manipulation of magnetic field and temperature, which is impossible in case of conventional foams where time cannot be reversed.

Coil Configurations Study for Bi-2212 Subscale Magnets. CHRISTOPHER ENGLISH (Texas A&M University, College Station, TX, 77841) HELENE FELICE (Lawrence Berkeley National Laboratory, Berkley, CA, 94720)

The Superconducting Magnet Group at Lawrence Berkeley National Laboratory is developing subscale magnets consisting of Bi-2212 (Bi₂-St₂-Ca-Cu₂O_x) racetrack coils as part of its subscale program. Several configurations are being considered: the stand-alone racetrack, subscale common coil, subscale dipole, and subscale hybrid dipole. In order to prepare for the assembly and testing of these magnets, a study has been carried out to determine the short sample current (I_ss) and the Lorentz forces for each configuration. OPERA 3D has been used to determine the field distributions on the coils. The maximum field on the conductor determined the load line of each subscale magnet. The intersection of these load lines with the engineering critical current density versus magnetic field curve (J_EC(B)) for Bi-2212 round wire subsequently determined the Iss. The results show little variation in the Iss of each configuration due to the small slope of the J_CE(B) in the field range of 5-10 T. The Lorentz forces, also determined with OPERA 3D, have been analyzed by defining the magnetic pressure on the coils. Results from the analysis show that a possible testing sequence for the subscale program could be the stand-alone racetrack, subscale common coil, subscale dipole, and finally the subscale hybrid dipole, in order of increasing magnetic pressure. Future simulations for hybrid dipoles based on varying the current in the Nb3Sn from the current in the Bi-2212 coil are recommended.

Computational Development of H- Ion Sources for the Spallation Neutron Source. JUSTIN CARMICHAEL (Worcester Polytechnic Institute, Worcester, MA, 1609) ROBERT F. WELTON (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

The US Spallation Neutron Source (SNS) requires a high power H- ion source in order to achieve the desired neutron flux. Over the next several years, the SNS will require substantially higher average H- beam current than can be produced from conventional H- ion sources including our baseline source. H- currents of 70-100 mA with an RMS emittance of 0.20-0.35 mm mrad and a ~7% duty-factor will be needed for the SNS power upgrade project. Presently, external antenna sources, based on Al2O3 plasma chambers, have been developed which have been shown to produce beam currents of 25-35 mA with a duty-factor of 2-3%. Computer simulations employing the Finite Element Method (FEM) with coupled fluid dynamic, heat transfer, and thermal stress and deformation capabilities have been performed to investigate the design of the plasma chambers operating at higher duty-factors. These simulations show that a plasma chamber made from AlN can be designed to meet the full duty-factor requirement. In order to meet the beam current requirements, efforts are being made to (i) increase source plasma density by using magnetic confinement and (ii) improve the efficiency of ion extraction from the plasma. Towards these ends simulations are being performed using LORENTZ for magnetic field modeling and COSMOS for thermal analysis of the electron dumping electrode. An AlN plasma chamber, a solenoid confinement magnet and an electron dumping electrode have been designed. It is anticipated that substantially greater beam currents can be achieved with these improvements to the ion source.

Concept to Employ Magnetohydrodynamic Conversion in a Two Gigawatt Inertial Fusion Energy Direct Drive Power Reactor. BRETT ANDERSON (St. Olaf College, Northfield, MN, 55057) CHARLES GENTILE (Princeton Plasma Physics Laboratory, Princeton, NJ, 8543)

A two gigawatt Inertial Fusion Energy (IFE) direct drive power reactor, currently in conceptual design, injects deuterium-tritium targets into the reactor chamber at the rate of five hertz and uniformly illuminates each target with ultraviolet laser light, resulting in detonation. The conceptual design of this IFE reactor may provide an opportunity to directly harness the power in the post detonation ion fields. This can be accomplished by utilizing a magnetic cusp field to guide the ions into collectors located in the equatorial and polar regions of the reactor. The shaped ion fields resulting from this magnetic intervention configuration pose a distinct challenge, as their intensity may have the potential to damage certain areas within the ion collectors. One method of addressing this challenge is to employ magnetohydrodynamic (MHD) conversion to transform the internal energy of the ion fields directly into electrical energy, a process that would also attenuate the strength of the fields. In order to analyze the potential of MHD conversion in IFE, previous work on MHD conversion in other applications is examined in the context of this proposed IFE reactor configuration. Other conversion techniques are also investigated, including Compact Fusion Advanced Rankine II (CFARII) MHD conversion, radio frequency (RF) particle deceleration, and direct conversion. Analysis reveals that MHD conversion may be a promising solution depending on the intensity of the ion fields. However, a number of engineering and operational concerns need to be addressed; for example, the materials need to be able to withstand extreme conditions. In addition, some elements of the other methods for energy conversion could be incorporated into an MHD conversion design. The next logical step in the development of this aspect of the IFE reactor would be a scaled experimental test facility where material tests and methods can be advanced. This work is in support of efforts to develop an efficient, economical, and clean fusion energy source.

Conceptual Design for a 2 GW Inertial Fusion Energy Direct-Drive Power Reactor Employing a Mechanical Vacuum Pumping System. KELSEY TRESEMER (George Fox University, Newberg, Oregon, 97132) CHARLES GENTILE (Princeton Plasma Physics Laboratory, Princeton, NJ, 8543)

Presented is a conceptual design for a 2 gigawatt Inertial Fusion Energy (IFE) direct-drive power reactor. The reactor operates at 5 Hz, consuming approximately 450,000 tritium-deuterium targets/day, injected at speeds greater than 100 m/s into the target chamber and uniformly illuminated by laser light, leading to detonation. Resulting post-detonation ions are directed away from the first wall of the target chamber and into equatorial and polar caches using a magnetically-induced cusp field. The reactor is designed to breed and recycle fuel through the use of breeder blankets and a fuel recovery system. To minimize target-particle interference, the chamber will be kept at less than 0.5 millitorr through the use of turbomolecular pumps (TMPs) and corresponding mechanical backing pumps. Initially, these pumps were dry-bearing TMPs, however an investigation was performed comparing bearing-based TMP’s to magnetically-levitated TMPs, revealing other vacuum pump options. All pumps were evaluated based on a wide range of specifications, the most crucial being the maximum hydrogen pumping speed, greatest mean time between failure (MTBF), and the least amount of oil (if any) present in the vacuum system. Information collected from journal articles, industry, and operational TMP experience in other fusion related venues indicate that the employment of magnetically-levitated TMP’s appears to be a superior vacuum pumping solution in the IFE environment. Thus, as a direct result of this research, magnetically levitated TMPs will be adopted into the IFE reactor design.

Construction and Commissioning of a Micro-Mott Polarimeter for Photocathode Research and Development. APRIL COOK (Monmouth College, Monmouth, IL, 61462) MARCY STUTZMAN (Thomas Jefferson National Accelerator Facility, Newport News, VA, 23606)

Thomas Jefferson National Accelerator Facility uses polarized electrons to further the understanding of the atomic nucleus. The polarized source produces electrons by directing laser light onto a specially prepared gallium arsenide (GaAs) photocathode. During the course of this project, an off-beamline micro-Mott polarimeter has been built and commissioned within the Source Lab for photocathode research and development. A polarimeter measures the polarization, or spin direction, of electrons. The micro-Mott runs at 30 keV and can be used directly in the Source Lab, off of the main accelerator beamline. Construction of the Mott system began with a polarized source, which consists of a vacuum chamber complete with a cesiator and nitrogen triflouride (NF3) to activate the photocathode, residual gas analyzer (RGA), ultra-high vacuum pumps, an electrostatic deflector to bend the electron beam 90 degrees, and electrostatic lenses. The polarimeter is housed in an adjacent vacuum chamber. The circularly polarized laser light enters the polarized source, hits the GaAs photocathode, and liberates polarized electrons. The original longitudinally-polarized electrons are transformed into transversely-polarized electrons by the electrostatic bend. They are then directed onto a gold target inside the Mott and scattered for data analysis. The polarized source has been commissioned, achieving photoemission from the activated GaAs crystal, and the electrostatic optics have been tuned to direct the electrons onto the gold target. Nearly ten percent of the electrons from the photocathode reach the target, giving adequate current for polarization measurement. The micro-Mott polarimeter will aid in photocathode research and pre-qualification of material for use in the injector.

Construction of a Monitoring System for the Solenoidal Tracker At RHIC (STAR) Forward Meson Spectrometer (FMS). SHAWN PEREZ (State University of New York at Stony Brook, Stony Brook, NY, 11794) LES BLAND (Brookhaven National Laboratory, Upton, NY, 11973)

The Forward Meson Spectrometer (FMS) at Brookhaven National Lab, consists of a matrix of lead-glass bars viewed by photomultiplier tubes that surround the colliding beam axis. The FMS detects the two photons associated with the decay of a p⁰ meson, or other photons, electrons or positrons produced in the collisions. The pseudo rapidity -ln(tan(/2) dependence of particle production can be analyzed to explore parton distributions within the proton. We are currently designing an LED light pulsing system which will be used to monitor the performance of these 1264 lead-glass detectors. Using Very High Speed Integrated Circuit (VHSIC) Hardware Description Language (VHDL) to program the Field Programmable Gate Array (FPGA) via the Xilinx ISE WebPack development environment, the goal is to have the LED Panel mimic events generated from the proton–proton collisions by pulsing different patterns of light with amplitude control into the FMS. The aspect of this project that I have been assisting with is the PC Board design, which integrates the electronic components with the necessary circuitry and mechanics for the monitoring system to function. The software required for this design are Microsoft Office Visio 2007 to generate the block diagram of the processes between the electronics, Cadence OrCAD Capture Schematic to represent the systems circuitry, and PADS – PCB 2007 which is the PC board layout tool manufactured by Mentor Graphics. The LED monitoring system once completed, will provide a means of testing the FMS and monitoring its performance during RHIC operations.

Cosmic Ray Studies. MARGE BARDEEN (University of Illinois, Urbana, IL, 60137) MICHAEL BARDEEN (Fermi National Accelerator Laboratory, Batavia, IL, 60510)

I am writing this memorandum to suggest we segue into a slightly different direction for the QuarkNet evaluation. Based on last year’s Review, we are charged with collecting “metrics.” The issue, as I see it, is that the review recommendations are based on an unrealistic view of QuarkNet and that the current goals do not fit what the program has evolved into.

Definition of a Twelve-Point Polygonal SAA Boundary for the GLAST Mission. SABRA DJOMEHRI (University of California, Santa Cruz, Santa Cruz, CA, 94024) MARKUS ACKERMANN (Stanford Linear Accelerator Center, Stanford, CA, 94025)

Density Measurements of a 3He Target Cell. SARA MOHON (College of William and Mary, Williamsburg, VA, 23186) JIAN-PING CHEN (Thomas Jefferson National Accelerator Facility, Newport News, VA, 23606)

The discovery and study of elementary particles in nature has always been attractive to scientists. The spin structure of a neutron is one such popular study and typically involves collisions between a high energy electron beam and a neutron target. At the Thomas Jefferson National Accelerator Facility (TJNAF) in Virginia, glass cells full of Helium-3 (³He) serve as effective polarized neutron targets in its particle accelerator. A nucleus of ³He has two protons and one neutron. Typically, ninety percent of a ³He sample has two protons with opposite spins so that the overall spin of the nucleus is determined by the spin of the neutron. Before experiments can begin, characteristics of the cell must be measured and determined including its ³He density. The purpose of this project was to describe how to measure the density of ³He target cells. A laser and optics setup was used to measure how much laser light the ³He would absorb within the target cell at certain frequencies and temperatures. At each temperature, the data was curve-fitted using Root, and statistically analyzed to give a density measurement. As expected, the wider the absorption, the larger the density of ³He within the cell. Also, the density of the cell was larger at higher temperatures. These density measurements will be used to calculate the cell’s maximum polarization, correct data measurements from the particle accelerator experiment, and help further investigate the spin structure of the neutron. In the future, improvements concerning cell alignment in the oven should be made to provide more accurate results.

Designing an LED Monitoring System for the FMS. JONATHAN LANGDON (State University of New York at Stony Brook, Stony Brook, NY, 11794) LES BLAND (Brookhaven National Laboratory, Upton, NY, 11973)

The Forward Meson Spectrometer (FMS) at Brookhaven National Laboratory’s STAR Experiment is composed of lead glass cells which are used to detect photons produced in high energy collisions of gold nuclei or protons. In past iterations of the FMS, panels of fiber optics were used to provide light from light emitting diodes (LEDs) as a calibration signal. This test signal could be observed as an event distribution within the data, far removed from other physical events. For the FMS, the goal is to create a more comprehensive and adaptable LED testing system. Unlike previous iterations, the goal is provide variable light sources to cell clusters allowing for patterns of light to be used instead of simply pulses of light. This would provide a means for proofing the functionality of the FMS’s triggering system. To accomplish this, a type of microchip, known as a Field Programmable Gate Array (FPGA), will be installed to control the LED output. FPGAs are also known as programmable logic chips, since one can use a computer to define its behavior after it has been implemented. Making use of an FPGA development kit in conjunction with an "integrated software environment" (ISE), known as Xilinx ISE Webpack, a functioning system for controlling the light panels has been developed. However, in addition to the hardware aspect, it has also been necessary to develop graphical interface tools for loading light pattern instructions in real time. This was accomplished by way of Microsoft’s "Visual Basic.NET 2005 Express" interactive development environment (IDE). The final product, known as the "Light Panel Control System," is the product of by directional development, starting from the computer out to the development board and from the FPGA back.

Designing the Gamma Calorimeters for the Future International Linear Collider. ERIC JONES (State University of New York at Stony Brook, Stony Brook, NY, 11790) WILLIAM MORSE (Brookhaven National Laboratory, Upton, NY, 11973)

The electron-positron beams of the future International Linear Collider (ILC) must be monitored by utilizing feedback measurements of the bunch characteristics in order to keep them properly aligned for the optimum resulting luminosity once they collide. The Gamma Calorimeter (GamCal) is one of the proposed calorimeter designs to be placed in the very-forward region of the ILC that will be used to gather information about the beam interactions in order to maintain this alignment. It will measure the energy of photons produced by so-called beamstrahlung, a process which results from the intensification of the electromagnetic fields of the bunches as they pass through each other; however, their energy will not be measured directly. The beamstrahlung photons will first be converted into electron-positron pairs by directing them into a 10^-5 m thick diamond foil, and then the positrons will be magnetically deflected into a detector grid that will measure their energy. In order to obtain a quantity proportional to the luminosity, this information will then be combined with information from the Beam Calorimeter (BeamCal) that will detect the pair particles produced in the collisions. We have used Daniel Schulte’s simulation program, the Generator of Unwanted Interactions for Numerical Experiment Analysis Program, Interfaced with Geometry and Tracking (GEANT) (GUINEA-PIG), in order to understand the effects of changing important collision parameters such as the beam offset, the incoming beam angles, and the bunch lengths on the produced pair particles and beamstrahlung photons. The resulting GUINEA-PIG data were analyzed using the program Physics Analysis Workstation (PAW) and Excel. The photon energy and angular distributions will be used to optimize the detector placement in the GamCal, while other output data shall be used to determine if the luminosity can be optimized without data from the BeamCal during preliminary runs of the beams. Future studies shall also determine how well the converting foil will survive when the beams fail to interact, as the electron-positron beams are intense enough to punch holes through the foil, and these holes will decrease the acceptance of our detector. What we understand now are the number and energy acceptances for nominal bunch parameters with varying offsets and incoming angles, and that the foil should remain reliable to about 1% error.

Detection of Ultra High Energy Cosmic Rays Using Radar. STEVEN HICK (State University of New York at Stony Brook, Stony Brook, NY, 11794) HELIO TAKAI (Brookhaven National Laboratory, Upton, NY, 11973)

Ultra High Energy Cosmic Rays (UHECR) are constantly bombarding our planet from unknown sources outside the solar system and uncovering their mysteries can provide insight into the origins and evolution of the universe. The Mixed Apparatus for Radar Investigation of Cosmic-rays of High Ionization (MARIACHI) project is a collaborative effort between research scientists, educators, and students that will explore UHECR. Understanding UHECR will be a major accomplishment in the physics community since the energies they produce are orders of magnitude higher than energies we can produce on earth with current particle accelerators. MARIACHI will scatter radio waves off ionization trails that are created when UHECR interact with our atmosphere, and will be detecting these signals using scintillator arrays that are strategically located across Long Island. Along with the scintillator arrays, antennas will be constructed and used for the detection of UHECR, and calibrating these antennas will be a major step forward for MARIACHI. The design for an antenna is a simple double dipole, which we have been experimenting with all summer. Designing, calibrating, and implementing the antennas as a compliment to the scintillator arrays is a main goal for the project. Furthermore, MARIACHI will be developing ways to subtract unwanted background information from meteors and other sources that try and mask the detection of UHECR. The MARIACHI project is still in its initial phases and there is a high risk involved since it is unknown whether or not it’s possible to use radar for UHECR detection. Although there is this risk factor the concept of MARIACHI is highly seductive since the forward scattering technique is extremely inexpensive, which allows for a wide range of users to participate. The project is mainly concerned with pure scientific research, but is unique in the fact that research scientists, educators, and students are all participants. Detecting UHECR and extracting maximal information from the MARIACHI project has promise and potential for opening many new doors in physics and education.

Determining the Components of an Iron Beam at the NASA Space Radiation Laboratory. JENNIFER MABANTA (St. Joseph's College, Patchogue, NY, 11772) MICHAEL SIVERTZ (Brookhaven National Laboratory, Upton, NY, 11973)

Before extended space missions can occur, protective measures must be put in place for astronauts since prolonged exposure to radiation fields can have adverse effects. The purpose of the research done at the NASA Space Radiation Laboratory (NSRL) at Brookhaven National Laboratory (BNL) is to gain a better understanding of the cosmic rays in space and develop the most efficient countermeasure for the voyagers. Proton and heavy-ion beams from the BNL Booster accelerator are directed along a beam line to NSRL. These beams mimic cosmic rays providing a controlled area in which to study the effects of the rays. The most harmful of the rays is iron and the least destructive and most abundant is hydrogen. Of particular interest to NASA are the iron beams as they are the most destructive form of radiation facing astronauts. Since completely shielding them from these heavy beams would not be feasible given the constraints in space, scientists are seeking to utilize the process of fragmentation in their shielding methods. Fragmentation is the way in which heavy ions break up into lighter less dangerous ions. In order to study this process, it is necessary to measure the components within the beam. To achieve this, a scintillator detector is placed within the beam. However, the response of this scintillator is not linear with the deposited energy; it follows a relation known as Birk’s Law. In order to study the different components of the beam, the response function of the scintillator must be determined. Once this response function is made linear, each elemental ion within the iron beam is more easily identified. To create the best fit, the fewest number of parameters must be used while still keeping the value of chi squared at a minimum. Using the spreadsheet software Excel, a fitting routine was created that could be implemented on each of the components of the iron beam from hydrogen to iron. Using this routine, the centroids for the peak of each element was determined and used to develop the response function. A second order polynomial was found to be adequate to fit the response of the scintillator, y = 0.000121x^2 +1.0x. A comparison of the scintillator response function before and after unfolding shows that the response can be portrayed as a linear function within a given range. Using this function, scientists will be better able to characterize the iron beam in order to develop the best shielding methods for harmful space radiation.

Development of an Apparatus for Analysis of Monolayers by Grazing Incidence X-ray Diffraction (GIXD) and Brewster Angle Microscopy (BAM). MORGAN JACOBS (University of California, Berkeley, Berkeley, CA, 94707) JAMES VICCARO (Argonne National Laboratory, Argonne, IL, 60439)

The simultaneous use of grazing incidence x-ray diffraction (GIXD) and Brewster angle microscopy (BAM) is a powerful tool in imaging surfactant-water interfaces in Langmuir troughs. The use of both techniques allow imaging on both the angstrom and the micron scale. Previously, each technique has been used individually, however, due to the geometrical limitations of the Langmuir trough, it is difficult to use both techniques simultaneously. X-ray diffraction requires that the surfactant be in an inert atmosphere and BAM requires that a microscope be placed close to the surface being analyzed. The BAM setup previously used at Argonne National Laboratory has served as a starting point from which to make modifications. The trough is not large enough to contain the BAM microscope in its entirety, and it is therefore not possible to seal the trough. As such, an inert atmosphere is no longer practical. It may be possible to place the BAM microscope outside of the trough, using a coherent fiber optic bundle to transport the light from the inside of the trough to the microscope. However, there are a few issues that one must consider when using fiber optics. Foremost among these are collecting enough light, keeping high enough resolution, and maintaining polarization. The purpose of this project is to develop an apparatus based on an investigation of these problems. The IG-163 wound fiber optic bundle from Schott Fiber Optics seems like a promising candidate for our setup as it does seem to fit our criteria, but some testing will be required to determine whether or not it will be suitable.

Development of Integrated PV Reporting System. MARIANO PADILLA (Fullerton College, Fullerton, CA, 0) WILLEM BLOKLAND (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory is a state of the art accelerator-based neutron source. Neutron-scattering research helps develop new materials for superconductors, magnets and plastics. SNS uses a hydrogen ion pulse beam to bombard a mercury isotope target to produce the neutrons. Operators control the accelerator complex by using console screens that can display and set Process variables (PV) from the Input/Output Controller (IOC) devices. Reports on the statistics of the accelerator operation are needed to evaluate the performance of the accelerator. Providing time sensitive and accurate reports of the overall health of the accelerator in an automated, efficient and intuitive manner is an important necessity. The reporting system requirements are to provide an intuitive multi-platform and web-browser based user interface, integration with Oracle, e-mail systems and Portable Document Format (PDF) generation. The reporting system provides the user with a web-based interface to setup specific PVs to acquire, how to process, and how to publish the results. An integrated reporting system is developed using PHP, Java, Javascript, Java Server Pages (JSP) and Business Intelligence and Reporting Tools (BIRT) for ECLIPSE Integrated Development Environment (IDE). The Oracle database already in production use at SNS is the primary storage location for the data collected from the PV’s at a rate up to 1Hz. The integrated reporting system will provide physicists, operators and engineers with a simple platform to monitor, analyze, and report on the operation of the SNS accelerator.

Effect of Biotin Density on 2D Streptavidin Crystallization on Lipid Monolayers at the Liquid-Vapor Interface. MATTHEW LOHR (Pennsylvania State University, University Park, PA, 16802) MASAFUMI FUKUTO (Brookhaven National Laboratory, Upton, NY, 11973)

Phospholipid monolayers at the gas-liquid interface are interesting because of their ability to act as templates for two-dimensional (2D) crystallization of various proteins. Such behavior could lead to utilization for assembly of practical bio-nanostructures. Previously studied examples of this phenomenon include the crystallization of streptavidin through binding with biotinylated phospholipids. In this study, we examine the effect of biotin surface density on streptavidin crystallization by observing the behavior of streptavidin at an ionic subphase-vapor interface coated with a phospholipid monolayer comprised of a binary mixture of dimyristoylphosphatidylcholine (DMPC) and biotin-capped dipalymitoylphosphotidylethanolamine (DPPE-x-Biotin). We monitor the formation of 2D streptavidin domains on lipid surfaces using Brewster-angle microscopy (BAM) over 20 hours. The mean molecular area of lipids is fixed at 75 Å2/lipid, and the mole fraction of DPPE-x-Biotin ranges from 100% to 0.01%. These observations have yielded several distinct regimes for crystallization behavior. At 8% DPPE-x-Biotin composition and above (937.5 Å2 per biotin and below), bowtie-shaped crystal domains form almost immediately after injection of streptavidin, grow with time, and eventually cover the entire surface of the sample. At 5% and 4.3% DPPE-x-Biotin composition (1500 and 1744 Å2 per biotin), crystal domains only partially cover the available sample surface. At 3.9% and 3.5% DPPE-x-Biotin composition (1923 and 2142 Å2 per biotin), several crystal domains are observed, but they are not uniformly distributed over the entire surface. At 3% DPPE-x-Biotin and below (2500 Å2 per biotin or larger), the surface shows no crystal domains that can be discerned by BAM (=10 m). According to previous diffraction studies of streptavidin crystals under similar conditions, the proteins arrange in two-dimensional unit cells with an average of 1610 Å2 per biotin binding site. This observation and our BAM studies provide strong evidence that in order for the 2D crystallization of streptavidin to take place, the surface density of biotin linkers must be comparable to or larger than the binding site density in the 2D crystal. This observation may be key to understanding the mechanisms behind streptavidin’s crystallization behavior. These results supplement ongoing studies of streptavidin crystallization, including x-ray and optical studies of the effects of subphase pH.

Effect of Pipes in a Tank to be Purged of Oxygen. LAURA ZANTOUT (University of Minnesota, Minneapolis, MN, 55455) STEPHEN PORDES (Fermi National Accelerator Laboratory, Batavia, IL, 60510)

To produce a viable 50kton LArTPC (liquid argon time projection chamber), as proposed, the liquid argon within must reach a purity level of 10ppt oxygen. The purpose of the Daisy experiment is to determine if pipes used as structural components inside this detector would trap air and cause virtual leaks. A 2 cubic foot tank filled with 50 half-inch diameter pipes was used to simulate the structure that would be within the detector. As argon flowed through the tank, oxygen levels were monitored both on the gas outlet and within using monitors of various sensitivities. Several variations were run: with an internal fan, without a fan, and with one end of the pipes capped. Plots of percent oxygen vs. time for all of the runs were fit well by perfect mixing equations. This suggests that oxygen was not trapped in the pipes, but instead diffused out quickly. Other turbulence (such as convection currents) may have also accounted for some mixing, especially in the capped run. It appears that building a structure of much longer pipes will not contaminate the liquid argon inside a detector via virtual leaks, as long as mixing through diffusion is given time to progress, or sped up by a fan.

Effects of Elemental Impurities on TiNiSn Solution Growths. THOMAS BRENNER (Carleton College, Northfield, MN, 55057) PAUL CANFIELD (Ames Laboratory, Ames, IA, 50011)

The intermetallic compound TiNiSn has been of interest to researchers because of its semiconducting and thermoelectric properties. We attempted to determine the effects of constituent element purity on the growth and electrical properties of TiNiSn single crystals. We grew TiNiSn single crystals from a Sn flux, each time varying the purity of our constituent elements. In order to test the hypothesis that chlorine impurities affect the crystal formation and electrical properties of TiNiSn, we added nickel chloride powder to the starting elements for several growths. Qualitative differences in crystal growth were observed, and secondary compounds were identified by x-ray diffraction whenever possible. Resistivity measurements were made between 2 and 375 K on TiNiSn crystals from each growth, so that the effect of elemental purity on resistivity could be determined. Using the resistivity data, we calculated the semiconducting gap for each sample. Lower purity Ti led to variation in growth products, but changing Sn and Ni purity did not produce variation. The addition of nickel chloride produced several changes in the growth. For all samples room temperature semiconducting gaps were between 110 and 180 meV. No trends were observed in either gap energy or resistivity with respect to elemental purity.

Electron Cloud Modeling for the Positron Damping Ring Wigglers in the International Linear Collider. JENNIFER YU (Cornell University, Ithaca, NY, 14853) C.M. CELATA (Lawrence Berkeley National Laboratory, Berkley, CA, 94720)

The positron-electron collisions in the ILC must be simple, clean, and precise. However, the presence of an electron cloud in the positron damping ring would lead to a positron beam with unfavorable behavior and position. The research conducted for the Center of Beam Physics looked at the formation of the electron clouds using computer simulations, specifically in the wiggler section of the ring. The wiggler section is two hundred meters of magnetic dipoles that produce vertical fields of alternating sign. In the wigglers, the accelerated beam emits intense synchrotron radiation. When it hits the chamber walls, the radiation initiates the build-up of electrons. These primary electrons, trapped in the wigglers, also hit the vacuum walls and make even more electrons, called secondary electrons. The secondary electrons also produce electrons as the positron beam attracts the electron cloud and swings it to the opposite wall. The electron cloud can send the beam off track so the beam misses its collision or worse, hits the chamber walls. The electrons can also give the positron beam energy, which can make it harder to focus the beam. The research conducted tracked the formation of the electron clouds using Posinst, a benchmarked 2D code, and Warp, a code with both 2D and 3D capabilities. A 3D code is needed to follow the electrons in the changing magnetic fields of the ILC wiggler. However, as a first step, the research aimed to match the results of 2D Posinst-like Warp with Posinst, which has been checked with numerous electron cloud experiments and against other benchmarked codes. The agreement of 2D-Warp and Posinst shows the accuracy and precision of Warp and will lead to electron cloud modeling with 3D Warp. The computer simulations in 3D Warp will track the electron cloud in the ILC wiggler and will help find limiting parameters for the cloud.The computer simulations in 3D Warp will track the electron cloud in the ILC wiggler and will help find limiting parameters for the cloud.

Electron Cyclotron Resonance Ion Source Interlock Design. FRANCISCO RAMIREZ (Yuba Community Colllege, Marysville, CA, 95901) DR RICHARD PARDO (Argonne National Laboratory, Argonne, IL, 60439)

ATLAS (Argonne Tandem Linac Accelerator System), is a series of machines whose purpose is to accelerate ions and deliver them to several targets. ATLAS has two electron cyclotron resonance (ECR) ion sources. In the event of a failure, several of the ECR source components which includes solenoids, voltage sources, radiofrequency generators, and magnets can damage themselves as well as other machinery or workers around the source. A digital interlock is to be designed so that the source cannot damage itself or humans working around it. This interlock device is a digital circuit constructed of small electronic circuits called logic gates, which are simple electrically controlled switches. This interlock circuit will receive inputs indicating water flow, temperature among other conditions and the interlock will shut down the source or the appropriate component if any failure is detected in any of these inputs. A panic button will be provided which will shut down the source in case of an emergency. In addition, a reset button will be included in the interlock system; its purpose will be to allow the interlock system to function again after a failure has occurred or the panic button has been pressed. This interlock is to be designed in two different ways, TTL (Transistor-Transistor Logic) and Relay logic. This device’s TTL circuit is still being designed, having its frame and part of its relay logic already built.

Electronic Structure of Nanowire Arrays. SAM OCKO (Brown University, Providence, RI, 2912) WEI KU (Brookhaven National Laboratory, Upton, NY, 11973)

It has recently been proposed that electrons will localize in the intersections of nanowires. This is purely a quantum effect, originating from the wave nature of electrons, as there is no attractive potential to keep them in the intersection. This phenomenon of localization is very important because it might provide the basis for a functional device which uses localization to exhibit useful properties such as ferromagnetism, anti-ferromagnetic insulation, and perhaps even superconductivity. We investigate the electronic structure of an array of nanowires using a piece of software we have written, which uses self-adaptive bi-orthogonal wavelet basis to model the electrons’ wave functions. Instead of trying to solve Schrödinger’s equations directly and treating the problem as an eigen-value equation, we use a functional minimization method which uses conjugate gradient and steepest descent methods. The program we have developed is easily extensible, as other systems can be applied simply through changing the energy functional, which makes our program able to model many-body effects and solve other Quantum Mechanical systems. Our program has successfully demonstrated phenomena of localization and showed that the strength of localization is inversely proportional to the diameter of the wires. In application, a grid of nanowires could be possibly be printed on a piece of silicon, with complete control over the properties of the grid. Through properly choosing the diameter of the nanowires and the density of the grid, we could control the kinetic energy and electron interaction of the nanowires. Through modulating the gate voltage, we can tune the number of electrons in the grid. A grid of nanowires whose properties are chosen carefully might show many interesting electrical properties, including ferromagnetism, anti-ferromagnetic insulation, and perhaps even superconductivity, which we hope to investigate further.

Elemental Analysis of a Shrub-Steppe Soil. RACHAEL KALUZNY (Western Michigan University, Kalamazoo, MI, 49071) JAMES MCKINELY (Pacific Northwest National Laboratory, Richland, WA, 99352)

Scanning electron microscopy is an important research tool used widely today in areas such as medical evaluation, forensics evidence examination, and scientific research. Electron microscopes use a beam of highly energetic electrons to examine objects on a microscopic scale. This examination can yield: topography, morphology, composition, and crystallographic structure. Advanced automation on the ASPEX Personal Scanning Electron Microscope (PSEM) 3025 was used to acquire elemental data on a shrub-steppe soil sample obtained from the Yakima Valley near Sunnyside, WA. The PSEM 3025 was designed for semi-automated imaging and analysis of inorganic specimens in the millimeter to sub-micron range. The shrub-steppe soil was analyzed at 20kV with a working distance of 18.4 mm and an emission current of 112 µA. The automated run performed energy dispersive x-ray spectroscopy (EDS) on each particle. EDS is a technique based on characteristic X-ray peaks which are generated when an electron beam interacts with the specimen. Characteristic x-rays are produced for each element present in the region being analyzed. Comparison of the intensities of x-ray peaks are then used to verify the relative abundance of each element in the analyzed region. A total of 6611 particles were analyzed on the soil sample. Rule files were developed to define membership classes based on chemical properties and elemental ratios. Particles were grouped into the defined classes as the data was being acquired. From these results it can be seen that the shrub-steppe sample consists primarily of silicates containing iron, aluminum, and calcium. This is consistent with the composition of silt loam soils in the Yakima Valley.

Establishing Atmospheric Background Ion Levels for the Stand-Off Detection of Ion Sources. MARC PENALVER AGUILA (Montgomery College, Rockville, MD, 20850) JEFFREY GRIFFIN (Pacific Northwest National Laboratory, Richland, WA, 99352)

Airborne ion counts can be used to estimate the source and intensity of combustive and electrostatic activity. To determine the minimum threshold for stand-off detection of ion sources, it is necessary to establish the background levels of ions in the lower atmosphere. Source detection depends on the ability to distinguish between regular background variations and exceptional activity. Natural occurrences such as the diurnal cycle, clouds passing overhead, or changing weather conditions all may contribute to increased ion formation. Gerdien condensers, which draw a constant stream of air through an electric field, were used for sampling atmospheric ions. All samples were taken through the exhaust of a fume hood. Due to a possible thermal response from the operational amplifiers used to magnify the signal, the electronics were calibrated for temperature. An analysis of frequency of ion level variation was performed. Abnormal weather phenomena were noted and correlated to ion levels. Finally ion sources were placed in the hood to determine the sensitivity of the gerdiens. The electronics were found to have a minimal thermal response within the range of temperatures observed during the experiments. No multiplier or offset was needed to normalize the data. Fourier analysis revealed that the diurnal cycle was the only regular period linked to a variation in ion levels. A significant change in ion levels was associated with a thunderstorm. Moreover, the gerdiens were found to be highly sensitive to ions drawn through a fume hood. Nearby ion sources could easily be detected by the gerdiens, despite regular temperature and diurnal variations. The range of detection of known activity merits further investigation, as does the discrimination of sources by ion polarity. Possible applications of ion sensors include off-site and stand off detection of motor vehicles, abnormal laboratory conditions, and other ionizing sources.

Experimental Study of Effects due to Perturbations on Boundary Conditions to Couette Flows. FREDERICK MANLEY (University of Illinois, Champaign, IL, 61820) HANTAO JI (Princeton Plasma Physics Laboratory, Princeton, NJ, 8543)

When fluid flows between two independently rotating cylinders at low aspect ratios (the ratio of the height to the difference in radii), the flow is seen to deviate substantially from ideal Couette flow due to Ekman circulation along the end caps. In the case where the end caps are attached to the outer cylinder, fluid with less angular momentum is advected into the bulk flow, which decreases the mean velocity as predicted by the ideal case. In order to study the stability of Ekman circulation, an experiment was devised to perturb the Ekman boundary layer by modifying the inner cylinder. Water flows between an aluminum inner cylinder and acrylic outer cylinder and its velocity is measured using a Laser Doppler Velocimeter (LDV) scanned radially from underneath to obtain 2-D velocity profiles. The robustness of the Ekman layer was studied against perturbations of varying magnitudes. Though perturbing the inner cylinder boundary did produce profiles closer to the ideal Couette case, the Ekman layer proved to be more robust than predicted. Both a 7mm offset and four o-rings placed on the inner cylinder were needed to produce profiles resembling the ideal Couette case. A new apparatus will be built with a larger aspect ratio to observe the effects of similar perturbations on the less stable Ekman flow. In the future, less viscous fluids may be used to determine the effects of larger Reynolds numbers on Ekman stability.

Extensions to DivGeo, a Graphical Tool for Editing 2D Edge Plasma Computational Meshes Extensions to DivGeo, a Graphical Tool for Editing 2D Edge Plasma Quasi-Orthogonal Computational Meshes. ALAN CHIN (Princeton University, Princeton, NJ, 8540) DAREN P. STOTLER (Princeton Plasma Physics Laboratory, Princeton, NJ, 8543)

Transport of plasma and neutral particles across magnetic flux surfaces in tokamak fusion experiments is a highly complex dynamical system of much practical interest in designing efficient fusion reactors. Codes that have been written to simulate the behavior of such systems include B2 and Eirene, used to model plasma and neutral transport behavior, respectively, in the divertors of ITER, and DEGAS 2, used to model neutral transport during Gas Puff Imaging experiments on the National Spherical Torus eXperiment (NSTX), both of which approximate the plasma region by 2D computational meshes that are designed to be quasi-orthogonal to the poloidal magnetic flux surfaces inside the tokamak. Because the distribution of mesh cells and the topology of the mesh are specific to each experiment, a customized mesh must be created for each study undertaken. DivGeo (DG) is a graphical user interface used, in combination with mesh-generating codes such as Carre and Sonnet, to create and modify such meshes. Using the C programming language and GNU utilities in a Red Hat Linux environment, the source code of DG was modified and subjected to testing by the author and users of DG at Princeton Plasma Physics Laboratory (PPPL) and ITER. After the modifications, DG was now able to be compiled using the freely available Open Motif 2.x graphics library, which allowed it to run reliably on the Linux machines at PPPL. In addition, several new features were added to DG, including an auto-save feature, the ability to recognize concave mesh cells and the segment of the reactor determining the outer bound of the mesh, and the ability to view the mesh at arbitrary angles and aspect ratios. Together, these improvements allow precisely tailored and general meshes to be generated more quickly and easily, accelerating the progress of computational studies on tokamak plasmas.

Fast Track Finding in the ILC's Proposed SiD Detector. DAVID BAKER (Carnegie Mellon University, Pittsburgh, PA, 15289) DR. NORMAN GRAF (Stanford Linear Accelerator Center, Stanford, CA, 94025)

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