A Decoupling Box for Spectral Readout in the Dissociative Electron Attachment of Nitric Oxide. ALEXANDER WARKENTIN (Fresno City College, Fresno, CA 93741) ALI BELKACEM (Lawrence Berkeley National Laboratory, Berkley, CA 94720)

The Dissociative Electron Attachment (DEA) of nitric oxide (NO) will be studied with the use of a femtosecond titanium sapphire laser and a position sensitive, delay line detector with the use of micro-channel plates (MCP) to aid in the search and study of reported dissociation channels. The position and time of flight (TOF) of the O- anions collected on a detector can be used with conservation of energy equations to determine the internal energy of the dissociated nitrogen atoms. However, One of the problems inherent to complex detection systems is limitations imposed by the presence of electronic noise. To address this problem the detector splits up the signal into two wires: one with a signal pulse and noise, and one with just noise. A high-pass filter decoupling circuit box was designed and built that allows an efficient subtraction of these contributing noise waveforms between wires. A test of the decoupling box’s performance was carried out using similar noise vibrations and signal pulses. The tests show that when the time delay is set correctly between the noise and noise/signal wires from the detector’s anode, that the out-of-phase noise cancels at the transformer in the decoupling box to yield a clean signal pulse that can be used in the data readout.

A Scintillating Possibility. THOMAS RAND-NASH (University of California, Berkeley, Berkeley, CA 94720) BOB JACOBSEN (Lawrence Berkeley National Laboratory, Berkley, CA 94720)

Accurate neutrino-nuclei cross sections are critical for understanding the dynamics of supernovae collapse. Further, supernovae models based on current cross section estimates have been unsuccessful in predicting the abundances of heavy elements produced during these events. To address these concerns, a new detector is required. The goal of the group is the selection of materials for, and construction of, prototypes for this detector. Several scintillating calorimeter paddles are constructed using sheets of solid scintillator, wavelength shifted optical fibers, and photomultiplier tubes. All aspects of the designs are explored, from electronics configurations, to data analysis methods, in an effort to understand the system while maximizing its function. The optimal configuration will resolve energies up to several hundred MeV, and will serve as the prototype for a segemented, upgradeable, and portable detector to be housed at the Spallation Neutron Source at Oak Ridge National Laboratory. Ultimately, the detector will be able to search for neutrino oscillations, measure the neutrino-proton scattering cross sections, and measure neutrino-nucleus cross sections.

A Simulation Study for a Prototype of a Multipurpose Segmented Neutrino Detector. LESLIE SANFORD (Southern University A&M College, Baton Rouge, LA 70813) DR. A. R. FAZELY (Lawrence Berkeley National Laboratory, Berkley, CA 94720)

We report Monte Carlo simulation studies of a small one-ton fine segmented detector with plastic scitinllator strips and x-y scintillating fibers for tracking. The Monte Carlo simulation is designed to simulate low energy neutrino interactions within a volume of one cubic meter. All Monte Carlo calculations were performed using Geant-3.21 code. The purpose of this research is to study the properties of low energy neutrino interactions. The segmented detector is capable of fine sampling and calorimetry in order to perform measurements of energy and momentum with good resolution for low energy neutrino interactions.  The detector is composed of alternating planes of thin plastic scintillator and tracking devices. These planes are of sufficient height and width to allow full calorimetry of Michel electrons.  The detector could serve as a prototype for a larger 200 - ton detector to search for neutrino oscillations, measure neutrino-proton scattering cross sections, search for rare decays of po and h and measure neutrino nucleus interaction cross sections, all of interest to nuclear, particle and astrophysics.

Absolute Photoionization Cross Sections of Kr4+ and Kr5+ Ions. ERIKA LEVENSON (University of California, Berkeley, Berkeley, CA 94720) FRED SCHLACHTER (Lawrence Berkeley National Laboratory, Berkley, CA 94720)

The abundance and charge-state distribution of ions inside planetary nebulae can tell scientists a great deal about the evolution of stars. Photoionization models are used in the analysis of emission lines of ions from nebulae, and atomic data such as photoionization cross sections are needed for input. Krypton ions are created in planetary nebulae, but no atomic data exists for their ionization. Absolute photoionization cross-section measurements were made for Kr4+ and Kr5+ ions at beamline 10.0.1 at the Advanced Light Source (ALS), using third generation synchrotron radiation from the ALS and the merged-beams technique. Interference of the direct and indirect photoionization processes produces resonances at several photon energies. The number of photoions detected and all measured experimental variables are used to calculate the absolute cross section at various photon energies to put the measurements on an absolute scale. Absolute photoionization cross-section measurements as a function of nominal photon energy for Kr4+ from 85-92 eV, Kr4+ from 121-134 eV, and Kr5+ from 88-95 eV were made. These data will serve as benchmarks for theory and will be available for input to astrophysical models.

Argon Ion Production Following a K-Shell Vacancy Cascade. CORI JACKSON (Solano Community College, Suisun, CA 94534) FRED SCHLACHTER (Lawrence Berkeley National Laboratory, Berkley, CA 94720)

Electron reconfiguration following photoionization of an atom is a complex process when the vacancy is created in an inner shell of the atom. Ionization of an inner-shell electron creates a cascade of electronic transitions to fill the vacancy or vacancies produced. An atom with a K-shell vacancy is unstable, often resulting in an emission of an electron. An electron from a higher level rushes to fill the void left after the departure of the K-shell electron. Transitions continue to occur until all lower shells have been filled with electrons. The entire vacancy cascade may follow any number of paths and each may produce a variety of highly ionized ions. Experimental investigation is performed to test quantum mechanical calculations regarding ion abundance following K-shell photoionization and resulting vacancy cascades. Charge state distribution and total ion yield resulting from a vacancy cascade following photoionization of a K-shell electron in argon has been measured as a function of photon energy using synchrotron radiation and magnetic mass spectroscopy. K-shell ionization of argon was produced by intense, monochromatic x rays supplied by beamline 9.3.1 at the Advanced Light Source (ALS) located at Lawrence Berkeley National Laboratory (LBNL). Argon was injected into a 180  magnetic mass analyzer and then bombarded with x rays to produce photoionization. Photons with energies ranging from 3200 to 3220 eV were used to ionize the K-shell electrons. The analyzer separated the resultant argon ions according to charge state. Argon-ion charge states Ar+ through Ar7+ were measured and normalized to existing abundance ratios for ion production at 3213 eV. Ion production was dependent on photon energy. Above the argon K-shell ionization threshold of 3206.3 eV, the Ar4+ ion is most prevalent. Ar4+ comprises approximately 42% of all ions produced above this photon energy. Below the K-shell ionization threshold, only small quantities of ions are produced. Future work will examine ion production as a function of reconfiguration pathway in order to explain these abundance results.

ATLAS Pixel: Quality Control of Front-End FE-I3 Chips. ERIC FENG (University of California, Berkeley, Berkeley, CA 94720) MAURICE GARCIA-SCIVERES (Lawrence Berkeley National Laboratory, Berkley, CA 94720)

ATLAS is an international collaboration to build the next-generation high energy particle detector for the Large Hadron Collider (LHC) at CERN. The innermost of the three concentric detectors comprising ATLAS is a pixel detector that is positioned directly outside the LHC beam pipe. The pixel detector's building block is the module, which consists of a 250um thick, finely pixilated silicon sensor tile that is bonded via indium bumps to 16 "Front End" silicon integrated circuits (FE-I3 chips). Each of the 50x400um sensor pixels is read out by an independent channel on one of the FE-I3 chips. Quality control of these high-precision FE-I3 chips is vital to ensure the high detector efficiency required to distinguish individual tracks among the hundreds produced every 25ns by the LHC collisions. We describe electrical tests and visual inspections of 2,016 Front-End FE-I3 chips that were tested between 1/20/04-5/6/04 for use in module construction for the pixel detector. A host of electrical tests were performed on the wafers before and after they were diced into individual chips, which determined that there is a 1% degradation in the electrical quality of the chips that occurs during dicing and indium bump deposition. Visual inspections were performed on chips to filter out those with indium bump defects such as residual photoresist, merged bumps, smeared or missing bumps, and debris. These quality control checks resulted in an overall electrical yield of 62.7% and a visual yield of 86.8%. These figures compare favorably with the conservative projections of 50% and 85% that were used to purchase chips for the pixel detector.

Characterization and Analysis of the Negative Feedback Loop Laser Pointing and Stabilization System for the Laser Optics and Accelerator Systems Integrated Studies (L’OASIS) Group. ZAC JUDKINS (College of Marin, Kentfield, CA 94904) CSABA TOTH (Lawrence Berkeley National Laboratory, Berkley, CA 94720)

The L’OASIS Ti: Sapphire laser system involves multiple laser beams propagated over hundreds of meters, ultimately converging within a volume of a few cubic millimeters. Mechanical and electrical noise within the laser sources and optics, along with air-currents on the tables, create small vibrations of the beam. Over long propagation distances these micron sized vibrations manifest as deviations from a known centroid by up to one fifth the laser beam’s diameter (and up to a full beam diameter in the focused area of the target chamber). Stabilizing the effects of these vibrations would greatly reduce wasted time and increase the success rate of experiments done by the group. The negative feedback loop stabilization system under testing this summer consists of a Hamamatsu Position Sensitive Detector (PSD) and a piezoelectric actuator (PZT) placed upstream from the PSD. The PSD relays information about the beam's movment about a set centroid to the PZT; the PZT makes micron sized pointing adjustments to reject these movements. The main problems with this stabilization method arise due to the laser system. The main pulse beam of the L’OASIS system has a repetition rate of 10 Hz, with each pulse lasting approximately 200 ps (50 fs inside the target chamber). The problem is that the frequencies of the problematic vibrations occur at a much higher rate. So, the PZT attempts to correct pulse N+1 using information about pulse N, but recent tests have shown that there is no position correlation between consecutive pulses at a rep rate of 10 Hz. A possible solution may be to inject a low intensity continuous wave (CW) laser collinearly with the main pulse beam, such that the two beams encounter the same optics and air-currents, and their centroids fluctuate in the same manner. The PSD would then have continuous information about the position of both laser beams and could simultaneously correct for the CW and the main pulse beam. Attempts to implement this solution have shown poor results due to the diverse nature of the vibrations to be rejected. The feedback loop successfully corrects the CW beam while decreasing the stability of the pulse beam by approximately 30%. Expecting collinearity of the beam paths seems implausible; increasing the repetition rate of the pulse beam to 1 kHz, may show improvement. Supported by the Department of Energy under Contract No. DE-AC03-76SF00098.

Coupling Mode Locked Femtosecond Laser Pulses into Photonic Crystal Fibers. JONAH VAN BOURG (Columbia University, New York, NY 10027) ROBERT KAINDL (Lawrence Berkeley National Laboratory, Berkley, CA 94720)

An important device in the realm of modern optics is a nonlinear interferometer - an optical array which can be used to determine the phase of a mode locked oscillated 800nm femtosecond laser operating at 80 megahertz and thereby stabilize it. To build such a device, the spectrum of the laser’s gaussian pulse must be broadened in such a way that it remains collimated and intense. To do so, the infrared laser light is focused into a complex microstructure fiber, also known as a photonic crystal fiber (PCF) by using an extremely precise five axis fiber mount (~0.2 um precision). After the beam was focused into the fiber, a direct correlation between the intensity of the input gaussian pulse and the breadth of the output spectrum was observed, confirming the important formula which governs self-phase modulation in nonlinear optics.

Evaluation of Various Methods of Neutron Dosimetry. ETHAN LAKE (Tennessee Technological University, Cookeville, TN 38501) PEGGY MCMAHAN (Lawrence Berkeley National Laboratory, Berkley, CA 94720)

As ionizing radiation, neutrons can be very destructive. Normally, the earth’s atmosphere and magnetic field act as a shield from large amounts of dangerous radiation. However, in the harsh environment of space and the upper atmosphere, there is little, or no, protection. Scientists wish to study the effects of neutrons on both living cells and microelectronics in order to better understand the effects of neutron radiation, and to improve shielding and safety precautions. At LBNL a large-area detector sensitive to fast neutrons is being developed which will incorporate new technology in scintillators and electron multipliers. Scintillators are being researched and will be tested to determine which is best for the application; selection criteria and characteristics will be discussed. The Gas Electron Multiplier consists of a series of foils which will multiply the scintillation induced photoelectrons. It will be assembled and tested to determine its operating characteristics, and results will be discussed. Using these components and others, the neutron detector will be able to give a 2-D picture of neutron flux incident on any sample.

Heavy Ion Beam Optical Diagnostics. BRYAN BELL (Shasta College, Redding, CA 96049) ALEX FRIEDMAN (Lawrence Berkeley National Laboratory, Berkley, CA 94720)

Heavy ion beam diagnostics consist of a slit that lets a portion of the heavy ion beam through and the scintillator that emits light when the ions strike it. Optical diagnostics are used to determine how ‘good’ a beam is. A beam needs to be spreading or contracting uniformly if it’s not changes have to be made to the focusing magnetic and electric quadropules.In the High Current Experiment(HCX) at Lawrence Berkeley National Lab a potassium(k+ ) ion beam is used. The ion beam injection energy is 1-1.6 MeV with a line charge density of 0.1-0.2µC/m. The goal of HXC is studying the transport of heavy ion beams the measuring the allowable “fill factor” (ratio of beam size to pipe size) improving the methods for determining the phase-space distribution of a beam. From an optical diagnostic station images are generated by the camera of the ion beam from the scintillator. When the ion beam passes through the slit it starts spreading out The spread is determined by the distance between the slit and the scintillator and the transverse velocity of the ions in the beam. From the spread we can obtain the transverse velocity of the ions in the beam x’ =(u-x)/dz where u is a the horizontal coordinate of a pixel on the scinttilator x is the slit position and dz is the distance between the scintillator and the slit. By taking a small vertical slice of pixels on the scintillator and summing over the vertical axis f at x’,x is obtained where x is the slit position. When this is done for all the vertical slices in the scintillor the distribution f(x’) at the position the slit was at is formed. By making a composite of f(x’) at each x another 2D image is made that shows the beam distribution as a function of x and x’. Similar things can be done to show the beam distribution as a function of y and y’ from a slit that moves vertically. With the program that was written over the summer it will do all of the operations to derive the image that represents f(x,x’) from a directory that contains the horizontal slit scan of the ion beam it also requires a text file describing the different properties of the experiment. The original goal of the project was to produce a 4D phase space distribution of the ion beam by synthesizing the to 2D data sets together. Unfortunately this wasn’t accomplished in the ten week time frame but the program as it exists now does produce nice 2D results for f(x,x’) f(y,y’) and f(x,y) and does cubic and hermite interpolation on these 2D distributions.

Let There be (More) Light: Modeling Superconducting Magnets to Optimize Luminosity for LHC. RAPHAEL ROSEN (Harvard University, Cambridge, MA 2138) STEVE GOURLAY (Lawrence Berkeley National Laboratory, Berkley, CA 94720)

Realizing luminosity levels necessary to operate the Large Hadron Collider (LHC) at maximum potential requires sharp advances in the development of superconducting magnets. The larger the aperture of a magnet, the greater the luminosity—the number of collisions per second per cross section. Larger apertures, however, decease the gradient—an essential parameter for steering beams. Our group modeled magnetic fields of quadrupole magnets, considering Nb3Sn and NbTi cables. We generated a plot of gradient as a function of magnet bore radius to determine how large one could construct a magnet without making the gradient flag too abruptly. The model we used employed a theoretical framework to describe magnetic field as a function of current, while it applied empirical equations to describe the current’s dependence upon field. We used Mathematica 5.0 to solve these two functions of one another. The ultimate, most accurate gradient model used four thick rings of superconducting cable. As expected, we found that Nb3Sn at 1.8 K had the highest gradient of our materials, though we were surprised to learn that the curves were not linear, but instead resembled a 1/x graph. Experimental measurements of gradient for Nb3Sn matched our plot well, though our field values appeared high when compared with our older lab data, but not so high when compared with our latest research. Predictions we made for NbTi matched existing data well, lending credence to the accuracy of our model’s theoretical component. Future research might look to improve the empirical formula for Nb3Sn. Additionally, physicists can, when given a necessary gradient, use our plot to determine the maximum possible bore radius, clearing the way for a new breed of magnets that may achieve still greater luminosities.

Measuring Physical Properties of Various Materials Using Lasers. DOMINIC HOWARD (Universitiy of Maryland, Adelphi, MD 20783) RICK RUSSO (Lawrence Berkeley National Laboratory, Berkley, CA 94720)

Part of my research for the summer included using lasers to measure properties of various materials. I shot a 1064nm Pulsed laser at a sample of material to be analyzed. The impact of the light pulse on the sample produces waves of certain characteristics that are based on the physical properties of the material. This is similar to the surface waves generated in water by throwing a rock into a calm lake. Those waves are analyzed by using a Mach-Zehnder interferometer connected to a computer using Labview software. It is therefore possible to find the flexural stiffness and shear rigidity of various samples including many different types of metals and papers. The results agreed with expected values. The advantage of this method is the sample can be moving while it is tested and has the capacity to give more accurate data.

Non-Intercepting Space-Charge Measurement of a Heavy Ion Beam. MONSERRAT AMEZCUA (Contra Costa Community College, San Pablo, CA 94806) ENRIQUE HENESTROZA (Lawrence Berkeley National Laboratory, Berkley, CA 94720)

In the pursuit to find other means of generating commercial energy, the Heavy Ion Fusion program tests concepts for inertial fusion drivers in a series of experiments. One of which, the Neutralized Transport Experiment (NTX), is exploring the physics of focusing with plasma a space-charge-dominated beam, along with a way to accurately obtain a neutralized ion beam profile without disturbing the beam itself. Analysis of the NTX electron beam diagnostic system designed and developed by The Heavy Ion Fusion group at Lawrence Berkeley National Laboratory and intended to non-disturbingly measure the profile of a heavy ion beam, is needed. The diagnostics system consisting of an electron gun that provides a small spot electron beam that transversely crosses and is deflected by the space-charge of a 25mA potassium ion beam, has a camera installed beyond the electron beam path focused on a scintillator that gets optical image of the electron beam by extracting charges. To predict an ion beam profile from the experimental electron beam deflection measurements, simulations of the electron beam trajectories were carried out by a program created in the computer language Python. The ion beam profile was predicted to have the values of the ion beam parameters used in the simulation that best approximated the experimental data. A second program, traced electron trajectories using the electric field calculated from the charge distribution obtained from an image of the ion beam, thus, having the specific charge density distribution, electric potentials, and size of the actual ion beam. Comparing the non-intercepting diagnostic result with results obtained from image analysis, wire scanning, and slit cup experiments, showed the electron beam diagnostics is fairly accurate. Furthermore, the converging potassium ion beam was partially neutralized using a plasma source and the non-intercepting electron beam diagnostics predicted an accurate profile when compared to image analysis results. However, there are some factors interfering with the sensitive electron beam diagnostics making it hard to accurately predict the profile of a fully neutralized ion beam, and the plans to cover the NTX diagnostics box with µ-metal seem promising. The current NTX diagnostic system can scan an ion beam of up to 3 cm in radius providing information that helps us understand the physics of heavy ion beams and getting us closer to the ultimate goal of using inertial fusion as an energy source.

Searching for Gravitational Lensing by Cosmic Strings in Hubble GOODS Data. CATHERINE IHM (Northwestern University, Evanston, IL 60208) PROFESSOR GEORGE SMOOT (Lawrence Berkeley National Laboratory, Berkley, CA 94720)

Cosmic strings are linear topological defects that may have formed during phase transitions of the early universe. Their existence has not yet been proven; their discovery could deeply affect cosmology and particle physics. To detect cosmic strings, their lensing effects can be exploited. If a string lies between an observer and a galaxy, light from the galaxy will then travel in two paths around the string. The observer will see an identical pair of galaxies, one image on each side of the string. Our detection method involves finding pairs of similar galaxies within a wide-field sky survey and analyzing the distribution of their separations. In the presence of a GUT-scale cosmic string, the number of pairs is expected to pile up at around 5 arcseconds of separation. Images from the Great Observatories origins Deep Survey (GOODS), which surveyed Hubble Deep Field-North and Chandra Deep Field-South, were searched for lensed pairs. Similarity between two galaxies is assessed by cross-correlating the objects and finding their correlation coefficients. All pairs within a certain range of appropriate correlation values were selected, and their separation distribution was plotted. No “piling up” of pairs occurred; a cosmic string was not detected. However, this technique for detection has not yet been applied to all of the sections in the GOODS fields. The rest of the data must be searched, and many other wide-field surveys investigated before the existence of cosmic strings is conclusively ruled out or confirmed.

The Complexities of Environmental Tobacco Smoke and How They Affect Exposure Assessment. DAVID FISHER (North Park University, Chicago, IL 60625) MICHAEL G. APTE (Lawrence Berkeley National Laboratory, Berkley, CA 94720)

Researchers have studied Environmental Tobacco Smoke (ETS) to quantify the dynamic behavior and toxicity of each constituent. Understanding the behavior of ETS constituents is critical to accurate exposure assessment for health effects studies. In trying to accurately assess exposure in a number of smoking scenarios, researchers are finding that ETS is far more complex than once thought. The ultimate goal for researchers is to establish a set of tracers that successfully track the dynamic behavior of ETS for further field study in the health effects of ETS. In establishing the set, each marker constituent must represent characteristics of several other components of ETS. Problems in exposure assessment can because of the different dynamic behaviors of the constituents, such as differences in ETS gas and particle constituent behaviors. In particular, the use of nicotine as a tracer may cause exposure assessment misclassification because the dynamic behavior of nicotine is not similar to most other components of ETS. Research in component specific tracing has been deemed necessary for exposure and health effects to a given component. Two key factors affect the relative behavior of gas phase ETS tracers: ventilation and sorption. Sorption can be studied independently while ventilation experimentation must take sorption into consideration when interpreting data. Sorption experiments have been established to study ETS in real world conditions, meaning fully furnished rooms. Particle phase tracing must take into consideration particle size-dependent deposition rates as well as ventilation. Three particle size related classifications are studied. Functionally, these are lung alveoli absorbing particles, bronchial depositing particles, and nose and pharynx depositing particles. Particles also have more complex behavior considerations than gases, such as gravity, diffusion to surfaces, volatilization, and particle binding. This paper presents the complexity ETS and the limitations that tracers present in thorough exposure assessment.

The Universe Adventure: Public Education in Cosmology and Astrophysics. MELISSA MCCLURE (University of Rochester, Rochester, NY 14627) MICHAEL BARNETT (Lawrence Berkeley National Laboratory, Berkley, CA 94720)

In the past few years, the lack of public comprehension of scientific concepts and discoveries has become a concern. If people do not understand science, they are less likely to appreciate it; students and young people are an essential part of the future of science, but if they are not informed about the new and exciting innovations being made in technical fields, they may fail to be inspired to consider a career in one of them. At the very least, because government grants for science come from money from taxpayers, scientists wish to inform the public about the discoveries which their money is financing. The result has been an increase on the part of the scientific community to provide the public with information and education aimed towards a non-technical audience. To this end, scientists must use the latest information technologies and educational techniques to convey abstract concepts in ways that are accessible to a wide spectrum of learning styles.

Viability of Confined Magnetic Radiation Shielding for Human Mars Mission. MICHAEL MOORE (College of the Redwoods, Eureka, CA 99501) DR. STEPHEN GOURLAY (Lawrence Berkeley National Laboratory, Berkley, CA 94720)

The possibility of a human mars mission is greater than ever after the successes of the two robotic rovers and the discovery of tantalizing evidence that water once existed on the red planet. Among the many problems to overcome while traversing the inner solar system on a voyage to Mars is how to best shield future astronauts from the onslaught of radiation found in interplanetary space. The effects of ionizing radiation are well studied at low LET (linear energy transfer), but for the highly charged particles with high kinetic energy (very high LET) very little is known about the risk to humans. It is clear from measurements taken by several science instruments that interplanetary space contains more radiation than current shielding technologies can handle. Consisting mainly of protons, the radiation environment is most dangerous due to positive ions from solar particle events and galactic cosmic radiation. The kinetic energy of these ions varies from 2 keV to 1020 eV. By plotting the radius of curvature of charged particles through a constant magnetic field against kinetic energy and strength of field it is shown that a large part of the most dangerous ions will pass through even the strongest magnetic field producible using Superconducting NbTi.