Analysis of Beam Position Monitor. APRIL WHITE (Tennessee State University Nashville, TN 37209) THEODORE L. WILLIAMS (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

The Linear Accelerator (Linac) for the Spallation Neutron Source (SNS) accelerates negative hydrogen ions to an energy of one billion electron volts. In order to maintain the trajectory of the particles throughout the accelerator, beam position monitors (BPM) are utilized. The BPMs provide valuable information pertaining to the vertical, the horizontal, the phase, and the amplitude of the Linac beam. An interactive computer program was designed and implemented in MatLab for the purpose of analyzing the data acquired by the beam position monitors. Data analysis techniques included generation of statistical data and model independent analysis via singular value decomposition methods. In order to analyze the data created by singular value decomposition, a beam simulation module was generated. To analyze the spatial eigenvectors, the data output of the module was incorporated into the Matlab program. The results of the analysis will be used to improve the BPM's system performance and to obtain system resolution beyond that achieved by individual BPMs.

Automated Analysis of SNS Linac Beam Position Monitor Data. AMELIE GILLMAN (Tennessee State University Nashville, TN 37209) THEODORE WILLIAMS (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

The Spallation Neutron Source's (SNS) Linear Accelerator (Linac) accelerates pulsed beams of H- ions for use in neutron production via the spallation process. The accelerator consists of an ion source for H- production, a room temperature normal-conductivity Linac for acceleration of H- particles to approximately 200 MeV, and a superconducting niobium Linac with a nominal operating temperature of 2 K for acceleration of the beam to 1 GeV (90% the speed of light). In order to reduce beam loss and to improve beam stability, the trajectory of the intense H- beam must be strictly monitored throughout the Linac. In an effort to characterize and maintain alignment of the beam pulses, beam position monitors (BPMs) located throughout the Linac provide measurements of horizontal and vertical beam centroid displacement, beam phase, and beam intensity. An adaptable, interactive computer program was designed and implemented in MatLab for the purpose of automating the analysis of the data acquired by the BPMs. Program functionality includes generation of frequency distribution histograms and calculation of statistical information including the mean, standard deviation, and root mean square values for individual and multiple BPMs. Data filtering is applied per user-specified options including standard deviation and data variability constraints, as well as cross-parametric correlation of BPM measurement values. The application supports Model Independent Analysis via singular value decomposition (SVD) techniques, which allows for discrimination between temporally and spatially correlated oscillatory modes in the data. These SVD methods provide powerful technique for estimating the BPM resolutions, as well as for identifying coherent motion inherent in the beam. The results of the analysis will be used to characterize and improve the BPM system performance, as well as to aid in identifying the sources of coherent beam motion.

Beam Loss and Residual Activation Trending Data Analysis for the Spallation Neutron Source. ARIEL RUFFIN (Tennessee State University Alumna Nashville, TN 37209) TED WILLIAMS (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

The Spallation Neutron Source (SNS) linear accelerator has several diagnostic tools that are used to measure the amount of beam lost. These tools have been utilized during beam commissioning. Although the commissioning process includes a gradual increase in the beam intensity, the beam pulse width and the frequency of operation, the process also involves characterizing the beam. Some of the processes used to characterize the beam result in increased activation of accelerator components. The Front End, the Drift Tube Linac (DTL), and most of the Coupled Cavity Linac (CCL) of the SNS have been operated. Beam loss data were collected using Beam Loss Monitors and differential Beam Current Monitors. Residual activation data were also taken at various times during and after the commissioning run. Beam loss and residual activation data analysis is conducted according to guidelines specified in the Operations Procedure Manual titled "Procedure for Trending Beam Loss and Radiological Monitoring Data." As part of the analysis, a radiological survey is required. A precision-detailed radiological survey was designed and conducted and compared with the archived pulse-to-pulse beam loss monitor data and the calculated beam losses. The residual activation in the accelerator enclosure was found to be greater than predicted because that activation included losses resulting from exploring the beam characteristics.

Bettering Communication Among Nuclear Astrophysicists: An Overview of the Computational Infrastructure for Nuclear Astrophysics. RICK CARROLL (Pellissippi State Technical Community College Knoxville, TN 37933) MICHAEL SMITH (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

In the past half century there have been numerous advances in the understanding of astrophysical phenomena such as element synthesis during stellar events, and the evolution of the next generation of stars and planets. This progress is a result of the compilation of large datasets consisting of laboratory measurements of thermonuclear reaction rates. Surprisingly, the standard reaction rate library among the astrophysics community, REACLIB, subsists with a decade long lapse in incorporating laboratory findings. In a 2003 article, Michal Smith addresses the importance of centralizing the efforts of world-wide research, and introducing "user-friendly" dissemination and evaluation tools to astrophysicists. The Computational Infrastructure for Nuclear Astrophysics (CINA) project was launched in 2003 to fulfill this need. With this interactive suite, reaction rate information can easily be accessed, updated, and utilized. In order to improve the efficiency and functionality of the suite for nuclear astrophysics studies, CINA is currently undergoing a redevelopment stage. Specifically, efforts are being made to approach real-time retrieval of element synthesis data. Currently, datasets and other essential information used by the interface are stored in text files in a linear fashion. This means that a search for a particular piece of data must start from the beginning of a file and "look" for its target. The goal of the current project is to migrate the text file storage method to a relational database storage method, such as MYSQL, to increase the communication speed of data to the interface, and then to the research community. Once implemented, these improvements to the Computational Infrastructure for Nuclear Astrophysics will aid in the immediate evaluation, distribution and application of today's laboratory results.

Deposition and Characterization of Colossal Magnetoresistive La_0.8Sr_0.2MnO₃ Films on a Single Crystal-like CeO₂ Substrate Architecture. DAVID GETTMAN (California State University Fresno Fresno, CA 93740) AMIT GOYAL (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

La_xSr_1-xMnO₃ (LSMO) is one member of a class of metallic magnetic perovskites that show a large change in resistivity in an applied magnetic field, which is referred to as the colossal magnetoresistance (CMR) effect. This property makes the materials attractive from a technological viewpoint for use in hard disk drive read/write heads, magnetic sensors, and magnetic random access memories (MRAM). Some of the major obstacles to the commercial use of these materials are high deposition temperatures and the need to use relatively costly single crystal substrates for epitaxial growth. One inexpensive substrate used for the deposition of epitaxial YBa₂Cu₃O₇ superconducting perovskite films are single crystal-like CeO₂ substrate architectures. Films of LSMO with 20% Sr doping were deposited by radio frequency magnetron sputtering under various deposition conditions on a substrate architecture based on these CeO₂ substrates. The films were characterized structurally and morphologically by x-ray diffraction, optical microscopy, and step profilometry. It was discovered that all the deposited films were under-oxygenated using a wide variety of deposition conditions and therefore were not suitable for magnetoresistance measurements. Some discussion of possible reasons for this under-oxygenation is included. Future work will look at overcoming the oxygenation problem, measuring the magnetotransport properties of the LSMO CMR thin films, and depositing other types of half-filled ferromagnetic metals such as Fe₃O₄ which also show CMR effects.

Development of a Genetic Algorithm to Parametrize Thermonuclear Reaction Rates from the NACRE Library. CARLOS ORTIZ (Davidson College Davidson, NC 28035) MICHAEL SMITH (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

Astrophysicists simulating the processes inside stars that drive stellar explosions depend on large collections of thermonuclear reaction rates. The NACRE collaboration recently evaluated numerous key reaction rates, yet these rates have not been incorporated into REACLIB, a standard collection of over 60,000 rates. Incorporating the NACRE library requires the parametrization of all its rates into the functional form used by the REACLIB community. Implementing object oriented programming techniques in Fortran 90, a genetic algorithm (GA) was designed to fit these reaction rates with seven parameters. The range of these reaction rates may at times stretch over thirty orders of magnitude. The algorithm's implementation was inspired by numerous web sources, in particular the GA FAQ and the GA Archives. Moreover, the use of object oriented concepts was heavily guided by the writings of V. K. Decyk, C. D. Norton, and B. K. Szymanski in the journal of Scientific Programming. Currently, the algorithm generates good solutions in a timely fashion. However, its performance does not match either that of the Levenberg-Marquardt method or that of the Generalized Least Squares method, the latter currently under development for the Computational Infrastructure for Nuclear Astrophysics (CINA). Both of these methods readily fit a sizable portion of the NACRE library within a two percent maximum error, whereas the GA algorithm fits only most areas of the data sets satisfactorily. Still, the performance of both these and other methods depends on the quality of the input set of initial parameters. The task of generating this input could be performed well by the genetic algorithm, thus creating a robust hybrid algorithm. Also, the algorithm's structure readily allows further improvements, such as adding new search strategies and fitting data sets to other functional forms, thus serving as a flexible, much needed tool for researchers. It also allows changing the fitness function from chi squared to any other objective function, thus potentially eventually serving not only as a fitting algorithm, but also as a general-purpose nonlinear optimization algorithm.

Electron Tomography: A new Diagnostics Technology for the Spallation Neutron Source Accumulator Ring. AARON VINCENT (Laval University Quebec City, QC G1W 1M3) SARAH COUSINEAU (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

The Spallation Neutron Source accelerator ring will accumulate 10¹⁴ protons per pulse for the production of neutrons via the spallation process. Operating at such high beam intensities requires a reliable, robust set of beam diagnostics. The high beam intensity in the ring precludes the use of traditional interceptive beam diagnostics used to measure beam density distributions. Electron tomography is a new non-destructive, non-interceptive beam analysis tool that exploits the trajectory deflection of an electron bunch due to the proton beam electromagnetic field. A two-dimensional scan of the electron beam through the proton beam allows for a complete reconstruction of the two-dimensional cross-sectional proton beam density distribution. Here, the electron tomography system was simulated in an advanced modular programming package that modeled the interaction between a 50 to 200KeV electron beam and the electromagnetic field generated by the proton beam. Realistic electron gun, scanning and detection parameters were used to ensure accuracy and both lateral sweeping and fixed-pivoting hardware setups were studied for the electron gun. The collected data was filtered and the proton beam was reconstructed in MatLab using a modified version of a medical tomography reconstruction algorithm. The resulting reconstructed density profiles were compared with the original proton beam. The effects of sampling resolution, hardware parameters, mechanical error and data filtering were studied, and each parameter was optimized for accuracy of reconstruction and maximization of signal-to-noise ratio. It was found that even when realistic errors were introduced the reconstruction was still accurate enough to warrant the implementation of electron tomography technology in SNS. The reconstruction software developed here will eventually be used to process actual beam data in the SNS ring.

Linux-Based Application for the New Generation Digital Pulse Processing-Based Data Acquisition System for Nuclear Physics Experiments. ZACHARY OWENS (Walter State Community College Morristown, TN 37813-6899) ROBERT GRZYWACZ (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

Nuclear fusion and fission are, theoretically, ways to produce efficient and clean energy but they need to be economical. Fundamental nuclear physics research is necessary to address some of the energy generation issues. Reliable modeling of nuclei and their nuclear reactions is needed. So there are experiments that test theoretical nuclear models, where novel methods of doing experiments have been developed. Nuclear reactions e.g. fusion-evaporation and reaction products are studied. Rare reaction products are separated with the use of magnetic spectrometers. Single nuclei have to be identified and their decay radiation detected. A combination of detectors and electronic readout system is used to achieve that. Nuclear decay radiation is detected in semiconductor detectors. There is a charge that the detector converts into a voltage pulse and digitizes in the fast sampling electronic board. Signals go through an analog-to-digital converter, which produces a digital image of a pulse at 100 million times per second (100MHz). Real Time Processing circuitry is analyzing this image and extracting useful information characterizing pulse amplitude, its arrival time and radiation type. This information is extracted from the electronics and stored for further analysis. Readout and control software compatible with other Holifield Radioactive Ion Beam Facility (HRIBF) used systems is being developed. In this project existing Windows XP software has to be converted into Linux, which has better real time performance and reliability, and is easily modified. The software is converted by taking the code from the windows version of the software that runs. Then commenting out all the code that is not working right in Linux then slowly put it back together. The new generation of hardware that will supple this software with data is called Pixie-16 manufactured by XIA LLC, Ca. It comes with a 16 input channel PCI board with 100 MHz sampling Analog-To-Digital-Converter, which has new abilities in storing more information, which also may result in improving detection sensitivity. It is connected to a computer running operating system Enterprise Linux 3 (kernel 2.4). User-friendly interface has to be developed for easier control of the complex tasks of the Pixie-16 board. The Pixie-16 development will enable measurements on rare isotopes and study their properties more accurately.

Measuring the Friction Drag Reduction of Superhydrophobic Glass in Water. EVAN MARKEL (Cornell University Ithaca, NY 14850) JOHN T. SIMPSON (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

Through several mechanical and chemical processes, the surface structure of glass can be designed to have superhydrophobic properties. A material is defined as superhydrophobic if a drop of water sitting on top of the material beads up to have a contact angle with the surface greater than 150 degrees. (A perfectly superhydrophobic material has a contact angle of 180 degrees.) Among many applications, this glass could be used as an inexpensive coating for the bottom of ships or other watercraft. When the glass is submerged underwater there is a microscopic layer of air separating the surface of the glass from the water. Because this glass is so water repellant, there should be a significant reduction of friction drag in water, compared to normal glass. This project first involves designing and fabricating a magnetic bearing to separate form drag from friction drag in conducting drag reduction experiments. The magnetic bearing is composed of an electromagnet, infrared emitter, detector, and op-amp circuit, which work to levitate an object underneath the electromagnet. The bearing suspends a magnetic apparatus underneath it, which holds a cylinder of the superhydrophobic glass. A circular cylinder of the glass is used because there is no water displacement as it spins, so there is no form drag. The apparatus is then spun using air jets, and a high-speed camera counts the number and frequency of rotations as the glass spins in the water. From this information, a decay coefficient of the water's friction drag can be calculated. The results for the superhydrophobic glass will be compared to those for a control sample of regular glass, and the amount of friction drag reduction will be found and presented. This work is part of a project to design, test, and develop superhydrophobic nano-structured materials.

Monte Carlo Simulations of Type I X-ray Bursts. LUKE ROBERTS (Colorado College Colorado Springs, CO 80936) DR. MICHAEL S. SMITH (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

Type I x-ray bursts (XRB) occur on the surface of an accreting neutron star in a binary star system. Accreted matter from the normal star is deposited on the surface of the NS and becomes extremely hot and dense. In the steady state burn phase, hydrogen is converted to helium through the beta+ limited CNO cycle, which contributes to the temperature increase on the surface of the NS. Once a high enough temperature is reached in the envelope, a runaway thermonuclear explosion ensues. These thermonuclear explosions are driven by the rp- and alpha,p-processes, which occur on proton-rich unstable nuclei. Almost all reaction rates involving these nuclei have never been experimentally measured. Theoretically determined rates generally have an uncertainty greater than a factor of two. To understand how these uncertainties effect final nuclear abundances and energy generation throughout the burst, a Monte Carlo simulation using a post-processing element burning code is employed. In the MC simulation, all of the reaction rates are varied simultaneously for each of the 5,000 trials. This is done randomly for each reaction according to a log-normal probability distribution taken from the value and uncertainty of the rate as stated in the literature. We find variations in the nuclear reaction alpha(2alpha,gamma)12C strongly effect all final nuclear abundances and energy generation throughout the burst. Positron decays of the nuclei 21Mg, 24Si, 25Si, 30S and 34Ar also effect energy generation in the XRB. The final abundances of high mass nuclei are strongly affected by proton captures on nearby nuclei. Upper limits on the uncertainties of final abundances of nuclei were also found. Future work will include verification of results by separate methods and larger numbers of MC trials for more accurate statistics.

Optimization of the Aorsa 1-Dimensional Code. RYAN MOORE (Georgia Institute of Technology Atlanta, GA 30332) MARK CARTER (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

The Aorsa 1-dimensional program was written by E. F. Jaeger of the Fusion Energy Division at Oak Ridge National Labs. ORNL and the Princeton Plasma Physics Laboratory use the Fortran code to analyze plasma heating caused by an antenna that couples its radio frequency power to the plasma. The resolution of the analysis is dependent on the physics involved and is computationally intensive. Optimizing Aorsa will allow researchers at ORNL and PPPL to more accurately and efficiently analyze plasma heating by RF Antennas. To increase the resolution and decrease the runtime, three parts of the code were identified for optimization by timing studies. The most expensive subroutine, BESIEXP, calculated the i and j Bessel functions with argument, G, proportional to the ratio of the charged particle gyroradius to the wavelength. BESIEXP was called many times with a wide G distribution with the G's clustered around discrete steps. The subroutine is now replaced by one that interpolates linearly on a table of Bessel functions. The steps of the table are centered around the clusters of G to decrease the error. Interpolation cuts the time spent in BESIEXP by two-thirds. Spacing the table to align with the G distribution gives the same error as an evenly spaced table with 21 times the resolution. A second part of the code that is optimized is the impedance scan used for 3D antenna analysis. A Message Passing Interface now splits the scan among different processors that calculate their values independently and send them to the Master process for ordered output. MPI decreases the time spent in the impedance scan by a factor approximately equal to the number of processors used. The third part of the code identified for optimization was the dense matrix amat, solved for each wave. Preliminary testing shows that making the matrix sparse and using a sparse solver such as MUMPS will save time and memory with minimal error. Continued refinement on Aorsa is needed, but the benefit of the optimization can already be seen.

Thermal Rate-of-Rise and Cooling Curve as Diagnostic Tools for Closed Cycle Refrigerators (CCR). ARIEL RUFFIN (Vanderbilt University Nashville, TN 37209) LOUIS SANTODONATO (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

Temperature control is a crucial aspect of many types of scientific experiments, including most neutron scattering experiments. The Spallation Neutron Source (SNS), which will produce the most intense pulsed neutron beams in the world for scientific research and industrial development, will also develop advanced "sample environment" devices for controlling temperature and/or other sample parameters. The present research is part of the SNS sample environment development program, and involves the development of a new diagnostic technique ("thermal rate-of-rise") which will help debug and optimize commonly-used laboratory devices. This new technique, analogous to the well-known pressure rate-of-rise test, has been applied to a Closed Cycle Refrigerator (CCR) which produces temperatures in the 4 to 300 Kelvin (K) range. The thermal rate-of-rise test is prepared by first conducting the commonly used "cooling curve" diagnostic, where the CCR is actively cooled to its base temperature. The rate-of-rise test then proceeds by turning the machine off and allowing the temperature to drift back to room temperature while recording the data. Shown here is how the thermal rate-of-rise and cooling curves compliment each other and allow one to distinguish between various types of problems, such as inadequate heat shielding and virtual vacuum leaks.