Bulletin of the American Physical Society
2012 Annual Meeting of the California-Nevada Section of the APS
Volume 57, Number 13
Friday–Saturday, November 2–3, 2012; San Luis Obispo, California
Session D3: Nuclear and Plasma Physics |
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Chair: Warren Rogers, Westmont College Room: Business 003 0209 |
Friday, November 2, 2012 4:12PM - 4:24PM |
D3.00001: Results from the RHIC Beam Energy Scan Daniel Cebra In 2010 and 2011, RHIC ran a scan of several beam energies in order to map the phase boundary between hadronic and partonic matter. Au+Au collisions were studied at 200, 62.4, 39, 27, 19.6, 11.5, and 7.7 GeV. This range of collision energies is expected to produce systems that undergo the transition to hadronic matter at baryon chemical potentials that range from 25 to 450 MeV. At the lower end of the range of chemical potentials, the transition from partonic to hadronic matter will be a crossover, however at higher chemical potentials the transition is expected to be first order. Studies of the RHIC beam energy scan data are searching for signatures of the first order phase transition using signals which are sensitive to the nuclear compressibility. Studies of fluctuations are being used to identify the critical point. Additionally, studies are being pursued to identify where the new phenomena seen at the highest RHIC energies and used to establish the creation of a partonic medium will turn-off. The data from this first Beam Energy Scan have defined the key search energies for these observables. RHIC is now considering a follow-up BES-II to further examine these key energies. [Preview Abstract] |
Friday, November 2, 2012 4:24PM - 4:36PM |
D3.00002: Analysis of fixed target collisions with the STAR detector Brooke Haag Collisions between beam halo nuclei and the aluminum beam pipe allow the STAR detector at RHIC to study fixed-target Au+Al collisions. The injection and sub-injection energy gold beams produce Au+Al collisions at center-of-mass energies of 4.5, 3.5, and 3.0 GeV. These collisions allow STAR to extend the beam energy scan to lower center of mass energies and higher baryon chemical potentials than previously possible. This in turn provides a means of searching for the possible critical point to quantify the nature of the phase transition between hadronic and partonic matter. In this talk, fixed target acceptances for tracking will be discussed. Pion ratios extracted from these fixed-target collisions will be presented and compared to earlier published results from the AGS, SPS, and RHIC. [Preview Abstract] |
Friday, November 2, 2012 4:36PM - 4:48PM |
D3.00003: Cal Poly Contributions to the CUORE Experiment David Miller, Samuel Meijer, Michael Haskin, Thomas Gutierrez CUORE (Cryogenic Underground Observatory for Rare Events) is a multinational experimental collaboration searching for the lepton-violating neutrinoless double beta decay ($0\nu\beta\beta$) in $^{130}$Te. The detection of $0\nu\beta\beta$ would indicate the neutrino is a Majorana fermion and also set the absolute mass scale of the electron neutrino. The experiment is currently being built in stages at the Gran Sasso National Laboratory in Assergi, Italy. CUORE-0 is a detector array expected to go online this year consisting of 52 bolometric crystals in a single tower, which is equivalent to 1/19th of the full mass of CUORE. We will describe our recent contributions to activities associated with CUORE-0 deployment, background reduction efforts, and the CUORE crystal verification runs as the collaboration works towards bringing CUORE online in 2014. [Preview Abstract] |
Friday, November 2, 2012 4:48PM - 5:00PM |
D3.00004: Progress and Expectations for the NIFFTE Fission TPC Brandon Seilhan The Neutron Induced Fission Fragment Tracking Experiment (NIFFTE) aims to improve current neutron-induced fission cross-section measurements through the use of a purpose-built Time Projection Chamber (TPC). Recent improvements to the fission TPC, including a sixfold increase in instrumented area and the capability to determine neutron time-of-flight, improve the ability of the fission TPC to precisely measure fission cross-sections. The current status including updates on the measurement of the cross section ratio for U-238 to U-235 and Pu-239 to U-235 will be discussed. [Preview Abstract] |
Friday, November 2, 2012 5:00PM - 5:12PM |
D3.00005: Reflectivity Tests for the High Threshold \v{C}erenkov Counter Mirrors for the CLAS12 detector at JLab Harneet Grewal, Andrew Puckett, Youri Sharabian, John Price The CEBAF accelerator at the Thomas Jefferson National Accelerator Facility is currently undergoing an energy upgrade from 6 to 12 GeV. As a result of this, the existing CLAS \v{C}erenkov counter is not sufficient to distinguish electrons from pions. To alleviate this situation, a new, High-Threshold \v{C}erenkov Counter (HTCC) is being built to allow $e/\pi$ separation up to a momentum of $5\,\mathrm{GeV}$. This new detector will utilize a mirror assembly to direct the \v{C}erenkov photons into a region of the detector with a low magnetic field, and that is free from other detector elements. To maximize the efficiency of the HTCC, the mirror reflectivity is a critical parameter. It is also important to minimize the amount of material in the mirrors, to avoid degrading downstream measurements of the energy and momentum of the outgoing particles. Doing all of this, while maintaining the overall construction cost within stringent limits presented a challenge on several fronts. This talk will discuss the requirements for the HTCC, and will highlight the construction of the test stand currently in use for the mirror reflectivity tests. The present status of the reflectivity test will also be discussed. [Preview Abstract] |
Friday, November 2, 2012 5:12PM - 5:24PM |
D3.00006: Measuring gamma ray production from laser-produced pair plasmas G. Jackson Williams, Hui Chen, Jaebum Park, John Seely, Riccardo Tommasini Ultraintense lasers have been shown to produce large quantities of positrons in a short burst, forming an electron-positron pair plasma. Outside the laboratory, these plasmas are only found in energetic astrophysical events such as gamma ray bursts, active galactic nuclei, and black holes. Due to the low fluences from these interstellar phenomenon, however, direct observations of the annihilation events are difficult and many properties are still unknown. We have constructed and tested laser-plasma diagnostics to perform the first measurement of annihilation radiation from laser-produced pair plasmas. This talk will present experimental and simulation results from this effort and their implications for laboratory pair plasmas in the understanding of astrophysical events. [Preview Abstract] |
Friday, November 2, 2012 5:24PM - 5:36PM |
D3.00007: Experimental study of preformed plasmas using the Titan laser at LLNL Jaebum Park, Hui Chen, Jackson Williams, Hector Baldis, Andy Hazi, Shaun Kerr, Ed Marley, Ronnie Shepherd In ultra-high intensity ($>$10$^{19}$ W/cm$^{2})$ ultra-short ($\sim $picosecond scale) pulsed laser plasma experiments, the main irradiating pulses are usually preceded by nanosecond scale of pre-pulses, due to amplified stimulus emission (ASE). The ASE generates pre-plasma, which is often characterized by its scale-length, the spatial decay length of the plasma density. These preformed plasmas are believed to play an important role in laser-plasma interactions and in accelerating charged particles, such as electrons. To better understand their role in producing charged particle beams in laser-solid target interactions, we have investigated, using optical interferometry, pre-plasmas produced by a controlled nanosecond-long pulse laser and also ones created by the ASE of the short-pulse Titan laser at Lawrence Livermore National Laboratory. I will present the optical interferometry data and compare the characteristics of pre-plasmas from both the LP and ASE cases. [Preview Abstract] |
Friday, November 2, 2012 5:36PM - 5:48PM |
D3.00008: Cold Plasma Characterization and Interaction with Materials Jude Rowe The nature of cold plasma and the interaction it has on other surfaces and microbial organism is of great scientific and applied potential. Using a ``starting from scratch'' approach, a plasma chamber equipped with AC pick-up coils was designed and built to investigate interactions with the plasma state and other materials. Three main experiments were conducted, first plasma interacting with material within the chamber, second frequency change due to change in ionized gas, and finally methods of pumping energy into plasma were examined. AC Plasma was created using 60Hz power with voltage up to 1.5kV and 36mA in Helium and in air. Temperatures inside the chamber did not significantly increase and plasma temperature was derived from theory. Chamber pressure was measured down to 200 mtorr and averaged around 350 mtorr during measurements. The distance between electrodes controlled main plasma confinement for measurement within coil range. Fourier spectrum analysis was utilized in identifying and characterizing plasma internal characteristics. External macroscopic changes and wave form behaviors were observed and these behaviors will be discussed in context of current theories. [Preview Abstract] |
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