2-D Modeling of Energy-z Beam Dynamics Using the LiTrack Matlab Program. SEAN CAULEY (Paine College Augusta, GA 30901) MIKE WOODS (Stanford Linear Accelerator Center, Stanford, CA, 94025)

Short bunches and the bunch length distribution have important consequences for both the Linac Coherent Light Source (LCLS) project at SLAC and the proposed International Linear Collider (ILC) project. For both these projects, it is important to simulate what bunch length distributions are expected and then to perform actual measurements. The goal of the research is to determine the sensitivity of the bunch length distribution to accelerator phase and voltage. This then indicates the level of control and stability that is needed. In this project I simulated beamlines to find the rms bunch length in three different beam lines at SLAC, which are the test beam to End Station A (ILC-ESA) for the ILC studies, LCLS and LCLS-ESA. To simulate the beamlines, I used the LiTrack program, which does a 2-dimensional tracking of an electron bunch's longitudinal (z) and the energy spread beam (δE) parameters. In order to reduce the time of processing the information, I developed a small program to loop over adjustable machine parameters. LiTrack is a Matlab script and Matlab is also used for plotting and saving and loading files. The results show that the LCLS in Linac-A is the most sensitive when looking at the ratio of change in phase degree to rate of change. The results also show a noticeable difference between the LCLS and LCLS-ESA, which suggest that further testing of the effects caused by the Beam Switch Yard and End Station A to determine why the result of the LCLS and LCLS-ESA vary

A study of Z-plane capacitance. HARSHIL PARIKH (University of Illinois at Urbana Champaign Urbana-Champaign, IL 61801) DR. SANJAY SWAIN (Stanford Linear Accelerator Center, Stanford, CA, 94025)

The BaBaR detector at the Stanford Linear Accelerator Center is currently undergoing an upgrade to improve its muon and neutral hadron detection system. The Resistive Plate Chambers (RPCs) that had been used till now have deteriorated in performance over the past few years and are being replaced by Limited Streamer Tube (LSTs). Each layer of the system consists of a set of up to 10 streamer tube modules which provide one coordinate ( coordinate) and a single "Z-plane" which provides the Z coordinate of the hit. The large area Z-planes (up to ) are 1mm thick and contain 96 copper strips that detect the induced charge from avalanches created in the streamer tube wires. All the Z-planes needed for the upgrade have already been constructed, but only a third of the planes were installed last summer. After installing the 24 Z-planes last year, it was learned that 0.7% of the strips were dead when put inside the detector. This was mainly due to the delicate solder joint between the read-out cable and the strip, and since it is difficult to access or replace the Z-planes inside the detector, it is very important to perform various tests to make sure that the Z-planes will be efficient and effective in the long term. We measure the capacitance between the copper strips and the ground plane, and compare it to the theoretical value that we expect. Instead of measuring the capacitance channel by channel, which would be a very tedious job, we developed a more effective method of measuring the capacitance. Since all the Z-planes were built at SLAC, we also built a smaller 46 cm by 30 cm Z-plane with 12 strips just to see how they were constructed and to gain a better understanding about the solder joints.

An Automated Method for Characterizing the Relaxedness of Galaxy Clusters. MATTHEW GEORGE (Harvard University Cambridge, MA 02139) STEVE ALLEN / GREG MADEJSKI (Stanford Linear Accelerator Center, Stanford, CA, 94025)

Relaxed galaxy clusters are useful tools for probing cosmological parameters like the gas mass fraction of the universe. Selecting relaxed clusters for this purpose can be a time-consuming and subjective task, so we present methods to automate parts of the process. We fit elliptical isophotes to a diverse sample of Chandra cluster data and summarize other methods for quantifying relaxedness which will be included in future work. Analysis of the results of tests from isophote fitting, combined with numerical simulations of cluster structures and comparison to previous classifications will allow us to formulate criteria for selection of relaxed clusters. We find that they tend to have core radii less than approximately 60 kpc from King model fits, shifts in isophote centroids of less than 25 kpc over a range in semi-major axes of several hundred kpc, and significantly greater surface brightness profile gradients within 30 kpc of their cores than unrelaxed clusters. These criteria will help with future cosmological work as larger amounts of cluster data are taken and need objective classification.

Analysis of B → l Decays With BaBar. YIWEN CHU (Massachusetts Institute of Technology Cambridge, MA 02139) JOCHEN DINGFELDER (Stanford Linear Accelerator Center, Stanford, CA, 94025)

As part of the BaBar project at SLAC to study the properties of B mesons, we have carried out a study of the exclusive charmless semileptonic decay mode B → l , which can be used to determine the Cabbibo-Kobayashi-Maskawa matrix element V_ub. Using simulated event samples, this study focuses on determining criteria on variables for selection of B → l signal and suppression of background from other types of B ‾ B events and continuum processes. In addition, we determine optimal cuts on variables to ensure a good neutrino reconstruction. With these selection cuts, we were able to achieve a signal-to-background ratio of 0.68 and a signal efficiency of the order of 1%. Applying these cuts to a sample of 83 million B ‾ B events recorded by BaBar in e+e- collisions at the Υ(4S) resonance, we obtain a yield of 115 ± 19 B → l decays.

Background Characterization for Thermal Ion Release Experiments with ²²⁴Ra. HELEN KWONG (Stanford University Stanford, CA 94305) PETER ROWSON (Stanford Linear Accelerator Center, Stanford, CA, 94025)

The Enriched Xenon Observatory for neutrinoless double beta decay uses ¹³⁶Ba identification as a means for verifying the decay's occurrence in ¹³⁶Xe. A current challenge is the release of Ba ions from the Ba extraction probe, and one possible solution is to heat the probe to high temperatures to release the ions. The investigation of this method requires a characterization of the alpha decay background in our test apparatus, which uses a ²²⁸Th source that produces ²²⁴Ra daughters, the ionization energies of which are similar to those of Ba. For this purpose, we ran a background count with our apparatus maintained at a vacuum, and then three counts with the apparatus filled with Xe gas. We were able to match up our alpha spectrum in vacuum with the known decay scheme of ²²⁸Th, while the spectrum in xenon gas had too many unresolved ambiguities for an accurate characterization. We also found that the alpha decays occurred at a near-zero rate both in vacuum and in xenon gas, which indicates that the rate was determined by ²²⁸Th decays. With these background measurements, we can in the future make a more accurate measurement of the temperature dependency of the ratio of ions to neutral atoms released from the hot surface of the probe, which may lead to a successful method of Ba ion release.

Balloon-Borne Gamma-Ray Polarimeter (PoGO) to study Black Holes, Pulsars, and AGN Jets: Design and Calibration. ZACHARY APTE (Hampshire College Amherst, MA 01002) TSUNEYOSHI KAMAE (Stanford Linear Accelerator Center, Stanford, CA, 94025)

Polarization measurements at X-ray and gamma-ray energies can provide crucial information on the emission region around massive compact objects such as black holes and neutron stars. The Polarized Gamma-ray Observer (PoGO) is a new balloon-borne instrument designed to measure polarization from such astrophysical objects in the 30-100 keV range, under development by an international collaboration with members from United States, Japan, Sweden and France. The PoGO instrument has been designed by the collaboration and several versions of prototype models have been built at SLAC. The purpose of this experiment is to test the latest prototype model with a radioactive gamma-ray source. For this, we have to polarize gamma-rays in a laboratory environment. Unpolarized gamma-rays from Am241 (59.5 keV) were Compton scattered at around 90 degrees for this purpose. Computer simulation of the scattering process in the setup predicts a 86% polarization. The polarized beam was then used to irradiate the prototype PoGO detector. The data taken in this experiment showed a clear polarization signal, with a measured azimuthal modulation factor of 0.35 ± 0.02. The measured modulation is in very close agreement with the value expected from a previous beam test study of a polarized gamma-ray beam at the Argonne National Laboratories Advanced Photon Source. This experiment has demonstrated that the PoGO instrument (or any other polarimeter in the energy range) can be tested in a libratory with a simple setup to a similar accuracy.

Extended Source Gamma-Ray Emission from WIMP Annihilation in the Sagittarius Dwarf Elliptical Galaxy. VIDYA VASU-DEVAN (Columbia University New York, NY 10027) LARRY WAI (Stanford Linear Accelerator Center, Stanford, CA, 94025)

The proximity of the dark matter dominated Sagittarius Dwarf Elliptical Galaxy (position (l,b) = 5.6^o, -14^o) allows it to act as an ideal laboratory for the exploration of extended gamma-ray emission from Weakly Interacting Massive Particle (WIMP) annihilation processes in a dark matter-dominated system. Since the matter in our universe is predominantly dark, exploring such processes as WIMP annihilation will lead to a better understanding of cosmology. In order to study this gamma-ray emission, a model for the diffuse background gamma-radiation in the dwarf galaxy's region is extracted from the Energetic Gamma Ray Experiment Telescope (EGRET) data. After validating this model and comparing it to the EGRET diffuse model, the background model is added to effective bleeding-contamination from external point sources and multiple models for the signal-above-background emission. Various models of this emission are tested: a)no source located in region, b)unidentified point source 3EG J1847-3219 from the Third EGRET Catalog responsible for the emission and c)extended emission resulting from WIMP annihilation responsible for the signal above background. These models are created through the employment of Monte Carlo simulation methods, utilizing the response functions of the EGRET instrument to simulate the point spread function, energy dispersion and effects of variable effective area depending on angle of incidence. Energy spectra for point sources are generated from the best predictions of spectral indices listed in the Third EGRET Catalog and the spectrum for the extended dark matter source is generated from Pythia high energy annihilation simulations. Hypothesis testing is conducted to assess the goodness-of-fit of these models to the data taken by EGRET. Additionally, we hope to expand our analysis by employing the response functions of the imminent Gamma Ray Large Area Space Telescope (GLAST) to our models. This extension should highlight the sensitivity disparities between GLAST and EGRET and show GLAST's potential enhancement of this analysis. This process will allow for forecasting of extended WIMP annihilation emission signatures for the GLAST detector.

Hardware Testing of the BaBar Drift Chamber. BRYCE LITTLEJOHN (Principia College Elsah, IL 62028) JOCHEN DINGFELDER (Stanford Linear Accelerator Center, Stanford, CA, 94025)

The BaBar drift chamber provides position, timing, and dE/dx measurements for charged decay products of the (4S) resonance at 10.58 GeV. Increasing data collection rates stemming from higher PEP II luminosities and background have highlighted dead time problems in the drift chamber's data aquisition system. A proposed upgrade, called Phase II, aims to solve the problem with the introduction of rewritable, higher-memory firmware in the DAQ front-end electronics that lowers dataflow through the system. After fabrication, the new electronics components were tested to ensure proper function and reliability before installation in the detector. Some tests checked for successful operation of individual components, while others operated entire sections of the upgraded system in a mockup drift chamber environment. This paper explains the testing process and presents results regarding performance of the upgrade electronics.

Improving the raster scanning methods used with x-ray fluorescence to see the ancient Greek copy of Archimedes work. ISABELLA GRIFFIN (Norfolk State University Norfolk, VA 23504) UWE BERGMANN (Stanford Linear Accelerator Center, Stanford, CA, 94025)

X-ray fluorescence is being used to detect the ancient Greek copy of Archimedes work. The copy of Archimedes text was erased with a weak acid and written over to make a prayer book in the Middle Ages. The ancient parchment, made of goat skin, has on it some of Archimedes most valuable writings. The ink in the text contains iron which will fluoresce under x-ray radiation. My research project deals with the scanning and imaging process. The palimpsest is put in a stage that moves in a raster format. As the beam hits the parchment, a germanium detector detects the iron atoms and discriminates against other elements. Since the computer scans in both forwards and backwards directions, it is imperative that each row of data lines up exactly on top of the next row. There are several parameters to consider when scanning the parchment. These parameters include: speed, count time, shutter time, x-number of points, and acceleration. Formulas were made to relate these parameters together. During the actual beam time of this project, the scanning was very slow going; it took 30 hours to scan ½ of a page. Using the formulas, the scientists doubled distance and speed to scan the parchment faster; however, the grey scaled data was not lined up properly causing the images to look blurred. My project was is to find out why doubling the parameters caused blurred images, and to fix the problem if it is fixable.

Investigating the Infrared Properties of Candidate Blazars. JESSICA HALL (University of Southern California Los Angeles, CA 90007) SETH DIGEL, GREG MADEJSKI (Stanford Linear Accelerator Center, Stanford, CA, 94025)

Blazars are active galaxies with super-massive black holes, containing jets that accelerate plasma material and produce radiation. They are unique among other active galaxies for properties such as rapid variability and the lack of emission lines. The double-peaked spectral energy distribution (SED) found for most blazar objects suggests that synchrotron radiation and Compton scattering occurs in the jets. This study is an investigation of the infrared (IR) spectra of a selected population of blazar candidates, focusing on the IR properties of objects within the three types of blazars currently recognized by their spectral characteristics at other wavelengths. Using blazar candidates found in a recent study of the northern sky (Sowards-Emmerd et al., The Astrophysical Journal, 2005), IRAS data for 12, 25, 60, and 100 µm, as well as any available data from 2MASS and EGRET, were located. The synchrotron peak of the SED of each object was expected to occur anywhere in the infrared (IR) to soft X-ray range. However, peaks were generally found to lie in the IR range, suggesting potential selection biases. An analysis of selection techniques reveals that the figure of merit used in the original survey is engineered to select objects with a Compton scattering peak luminosity occurring in the GeV range, the energy band most easily detected by the upcoming GLAST mission. Therefore, this figure of merit selection process should be used to compile a list of blazar candidates for further study in anticipation of the launch of the satellite.

Localized PEPII Storage Ring Optics Measurements. JONATHAN LANDY (Caltech Pasadean, CA 91126) YITON YAN (Stanford Linear Accelerator Center, Stanford, CA, 94025)

in paper.

Mapping Strain in Nanocrystalline Nitinol: an X-ray Diffraction Method. MATTHEW BIBEE (University of California, San Diego La Jolla, CA 92093) APURVA MEHTA (Stanford Linear Accelerator Center, Stanford, CA, 94025)

Understanding the mechanical properties of biomedical devices is critical in predicting and preventing their failure in the body. Such knowledge is essential, for example, in the design of biomedical stents, which must undergo repeated strain over their ten year lifetimes without breaking. Computational models are used to predict mechanical response of a device, but these models are not complete; there are significant deviations from the predictions, especially when devices are subjected to repeated multi-axial loads. Improving these models requires comparisons with actual measurements of strained nitinol. Local measurements of the full strain tensor can be made using X-ray diffraction techniques, but they are currently limited to materials whose grain size is larger than the X-ray beam size or require several diffraction patterns produced by rotation of the sample. Nitinol stents are nanocrystalline, with grains smaller than any available X-ray beam. We present a method for measuring the local strain in a nanocrystalline material from a single X-ray diffraction pattern by extending current powder diffraction techniques. The components of the strain tensor are mapped onto a displacement ellipsoid, which is then reconstructed from diffraction data through Bragg's law and least-squares fitting. Using simulated diffraction data, we performed sensitivity tests to examine how the accuracy of the method depends on how much of the diffraction pattern is measured. We found that strain can be accurately calculated from measurements of at least three diffraction arcs of at least 20 in length. Thus we believe that our method is a viable approach to calculating strain provided a sufficient amount of diffraction pattern is recorded.

Neutron Attenuation and Monte Carlo Calculations Using the FLUKA Simulation Program. BRENT COVELE (Rose-Hulman Institute of Technology Terre Haute, IN 47803) ALBERTO FASSO (Stanford Linear Accelerator Center, Stanford, CA, 94025)

Rather than construct thick shielding around radioactive sources to attenuate hazardous radiation, physicists often design winding networks of tunnels to effectively limit the range of radiation while providing access to the source if necessary. However, it is important to know how quickly the radiation attenuates, and instead of planning physical experiments, physicists use complex simulations to model various situations via Monte Carlo calculations. The simulation program used in this experiment was FLUKA. A concrete labyrinth with two legs of lengths 10 d/vA and 20 d/vA (d is the centerline distance, A is the inner cross-section) was designed with an isotropic neutron point source at the mouth of the first leg. Sixty different scenarios were run with twelve energies and five cross-sections to determine the rate of attenuation. A model equation with two empirically determined constants was chosen to be fit to the resultant data. Most of the model curves matched the data in the high energies and in the first leg very well, but it was found that a "second-order" version of the model equation with an extra term in the denominator was better for matching the data from the low energies, especially in the second leg. One constant in the equation was shown to have a beam energy dependency, possibly exponential, while the other was independent. Both were fairly independent of the geometry, but both also showed remote signs of a linear, geometric dependency, especially in the lower half of the energy groups. Most of the energy curves remained within the upper and lower bounds of the universal transmission curve, although there was some slight intersecting at the upper bound at long distances. Further research is needed to fit a curve to the energy dependency of the first constant as well as corroborate the possible geometric dependencies. It is recommended that data fitting be continued with the second-order equation, including matching it to some high-energy data.

Photometric Supernova Typing for the SDSS SN Survey. ELIZABETH RIVERS (Wellesley College Wellesley, MA 02481) MASAO SAKO (Stanford Linear Accelerator Center, Stanford, CA, 94025)

In the fall of 2004 the Sloan Digital Sky Survey (SDSS) 2.5m telescope scanned the southern equatorial stripe for approximately 20 nights over the space of two months. Light curves for over four dozen supernovae (SNe) were collected over time using five colored filters ugriz that together had a range of approximately 3000A to 10500A. 22 SNe were spectroscopically confirmed with follow-up observation. Using the data obtained in the Fall 2004 campaign, preparations are now being made for the Supernova Survey of the SDSS II, a three-year extension of the original project. One main goal of the Supernova Survey will be to identify and study type Ia SNe of up to redshift ~0.4, the intermediate 'redshift desert,' as well as enabling further study of other types of SNe including type 1b/c and peculiar SNe. Most of the SNe found will not have spectra taken, due to time and cost constraints. Thus it would be advantageous to be able to robustly type SNe solely from the light curves obtained by the SDSS telescope prior to, or even without ever obtaining a spectrum. Using light curves of well-observed SNe templates were constructed for comparison with unknown SNe in order to photometrically type them.

Relative Humidity in Limited Streamer Tubes for Stanford Linear Accelerator Center's BABAR Detector. MARY LANG (Massachusetts Institute of Technology Cambridge, MA 02139) MARK CONVERY, WOLFGANG MENGES (Stanford Linear Accelerator Center, Stanford, CA, 94025)

The BABAR Detector at the Stanford Linear Accelerator Center studies the decay of B mesons created in e+e- collisions. The outermost layer of the detector, used to detect muons and neutral hadrons created during this process, is being upgraded from Resistive Plate Chambers (RPCs) to Limited Streamer Tubes (LSTs). The standard-size LST tube consists of eight cells, where a silver-plated wire runs down the center of each. A large potential difference is placed between the wires and ground. Gas flows through a series of modules connected with tubing, typically four. LSTs must be carefully tested before installation, as it will be extremely difficult to repair any damage once installed in the detector. In the testing process, the count rate in most modules showed was stable and consistent with cosmic ray rate over an approximately 500 V operating range between 5400 to 5900 V. The count in some modules, however, was shown to unexpectedly spike near the operation point. In general, the modules through which the gas first flows did not show this problem, but those further along the gas chain were much more likely to do so. The suggestion was that this spike was due to higher humidity in the modules furthest from the fresh, dry inflowing gas, and that the water molecules in more humid modules were adversely affecting the modules' performance. This project studied the effect of humidity in the modules, using a small capacitive humidity sensor (Honeywell). The sensor provided a humidity-dependent output voltage, as well as a temperature measurement from a thermistor. A full-size hygrometer (Panametrics) was used for testing and calibrating the Honeywell sensors. First the relative humidity of the air was measured. For the full calibration, a special gas-mixing setup was used, where relative humidity of the LST gas mixture could be varied from almost dry to almost fully saturated. With the sensor calibrated, a set of sensors was used to measure humidity vs. time in the LSTs. The sensors were placed in two sets of LST modules, one gas line flowing through each set. These modules were tested for count rate v. voltage while simultaneously measuring relative humidity in each module. One set produced expected readings, while the other showed the spike in count rate. The relative humidity in the two sets of modules looked very similar, but it rose significantly for modules further along the gas chain.

Turn-by-Turn and Bunch-by-Bunch Transverse Profiles of a Single Bunch in a Full Ring. RICHARD KRAUS (University of Nevada, Reno Reno, NV 89557) ALAN S. FISHER (Stanford Linear Accelerator Center, Stanford, CA, 94025)

The apparatus described in this paper can image the evolution of the transverse profile of a single bunch, isolated from a full PEP-II ring of 1500 bunches. Using this apparatus there are two methods of single bunch imaging; bunch-by-bunch beam profiling can image every bunch in the ring a single bunch at a time with the images of sequential bunches being in order, allowing one to see variations in beam size along a train. Turn-by-turn beam profiling images a single bunch on each successive turn it makes around the ring. This method will be useful in determining the effect that an injected bunch has on a stable bunch as the oscillations of the injected bunch damp out. Turn-by-turn imaging of the synchrotron light uses a system of lenses and mirrors to image many turns of both the major and minor axis of a single bunch across the photocathode of a gateable camera. The bunch-by-bunch method is simpler: because of a focusing mirror used in porting the light from the ring, the synchrotron light from the orbiting electrons becomes an image at a certain distance from the mirror; and since the camera does not use a lens, the photocathode is set exactly at this image distance. Bunch-by-bunch profiling has shown that in the Low Energy Ring (LER) horizontal bunch size decreases along a train. Turn-by-turn profiling has been able to image 100 turns of a single bunch on one exposure of the camera. The turn-by-turn setup has also been able to image 50 turns of the minor axis showing part of the damping process of an oscillating injected charge during a LER fill. The goal is to image the damping of oscillations of injected charge for 100 turns of both the major and minor axis throughout the damping process during trickle injection. With some changes to the apparatus this goal is within reach and will make turn-by-turn imaging a very useful tool in beam diagnostics.