Bulletin of the American Physical Society
2011 Fall Meeting of the APS Division of Nuclear Physics
Volume 56, Number 12
Wednesday–Saturday, October 26–29, 2011; East Lansing, Michigan
Session 2WB: Workshop on Advanced Digital Signal Processing Techniques in Nuclear Science II |
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Chair: Jac Caggiano, Lawrence Livermore National Laboratory Room: 104AB |
Wednesday, October 26, 2011 10:30AM - 11:00AM |
2WB.00001: Pulse-Shape Discrimination for Low-Background Proportional Counting Invited Speaker: Craig Aalseth Digital pulse-shape discrimination (PSD) is used to improve measurement sensitivity for internal-source gas proportional counters. Because the design of these detectors can be physically simple, they are well-suited for low-background applications where the radiopurity of detector materials must be stringently controlled. After mitigating dominant backgrounds (cosmic rays, external gamma-rays, radioactivity in materials), remaining background events frequently do not arise from ionization of the proportional counter gas. Various PSD methods have exploited the resulting pulse-shape differences. More sophisticated methods can offer better discrimination but may lead to more difficult calibration between model and detector. Variations between modeled and experimental shapes can limit the discriminating power achieved. This work addresses this difficulty by generating a template shape from each individual sample measurement of interest, a ``self-calibrating'' template. Differences in event topology can also cause differences in pulse shape. In this work the temporal region analyzed is limited to maximize background discrimination while avoiding unwanted sensitivity to event topology. Low-background measurements of tritium, carbon-14, argon-37, and argon-39 are currently being developed at the Pacific Northwest National Laboratory with detectors employing radiopure materials developed for neutrinoless double-beta decay and dark matter searches. The application of self-calibrating template PSD to measurement of these radioisotopes, along with initial measurement results, is described. Applications such as nuclear treaty verification, elucidating the environmental carbon cycle, and the assay of low-background materials for next-generation nuclear physics experiments are presented. [Preview Abstract] |
Wednesday, October 26, 2011 11:00AM - 11:30AM |
2WB.00002: From Analog Inputs to Physics Results: A Case Study in Using Digital Electronics in Physics Research Invited Speaker: Chris Perkins Particle collisions at the Relativistic Heavy Ion Collider (RHIC) can range from grazing collisions to head on collisions and can result in a wide range of physical interactions between the colliding particles. Signals from the full detector suite at a collision point cannot be readout quickly enough to record the full 10 MHz crossing rate. Therefore, to make physics conclusions from these collisions, signatures of specific interactions must be identified using a subset of the full detector to reduce the data acquisition rate to a manageable volume. These signatures must be encoded into a real-time digital pattern recognition system to choose the interactions needed to achieve physics results. This is accomplished using custom built electronics arranged in a tree structure to form a digital trigger system composed of analog-to-digital conversion electronics at the tree inputs and digital electronics throughout the rest of the tree. The trigger system developed for the Solenoidal Tracker at RHIC (STAR) is able to identify a wide array of configurable patterns among thousands of individual detectors at a rate of 10 MHz. The system can be easily programmed to identify new patterns and can be used to look for many different patterns simultaneously. The flexibility of this system allows for a wide range of physical interactions to be explored. This system was recently ported for use at a new experiment at RHIC called AnDY, exhibiting the system's general utility as a trigger and data acquisition system for physics experiments. [Preview Abstract] |
Wednesday, October 26, 2011 11:30AM - 12:00PM |
2WB.00003: Background Rejection for the MAJORANA Experiment Invited Speaker: Reynold Cooper The MAJORANA project is a neutrinoless double beta decay experiment based on the use of high purity, enriched, $^{76}$Ge crystals housed in ultra low background Cu cryostats as both the source ans the detector. In order to demonstrate the feasibility of the experiment, the collaboration is currently building a demonstrator consisting of up to 30 kg of enriched High Purity Germanium (HPGe) detectors and 10 kg of natural HPGe detectors. These detectors, which will take a P-type Point Contact (PPC) geometry, are designed to maximise performance in terms of energy resolution and background rejection efficacy. In order to achieve the background goal of 1 count per tonne-year in a 4 keV wide region of interest around the 2039 keV neutrinoless double beta decay Q-value, the MAJORANA DEMONSTRATOR will be constructed using ultra-clean materials and will employ sophisticated background rejection techniques. One such technique, which is key to achieving this background goal, is the ability to distinguish between single-site events from neutrinoless double beta decay and multiple-site events resulting from background gamma rays. This will be achieved through analysis of the digitised signal response of the HPGe detectors. The physics goals of the MAJORANA experiment will be discussed, along with the roles played by digital electronics and digital pulse processing techniques. Details of key background rejection algorithms will also be presented. [Preview Abstract] |
Wednesday, October 26, 2011 12:00PM - 12:30PM |
2WB.00004: Present and Future Applications of Digital Electronics in Nuclear Science - a Commercial Prospective Invited Speaker: Hui Tan Digital readout electronics instrumenting radiation detectors have experienced significant advancements in the last decade or so. This on one hand can be attributed to the steady improvements in commercial digital processing components such as analog-to-digital converters (ADCs), digital-to-analog converters (DACs), field-programmable-gate-arrays (FPGAs), and digital-signal-processors (DSPs), and on the other hand can also be attributed to the increasing needs for improved time, position, and energy resolution in nuclear physics experiments, which have spurred the rapid development of commercial off-the-shelf high speed, high resolution digitizers or spectrometers. Absent from conventional analog electronics, the capability to record fast decaying pulses from radiation detectors in digital readout electronics has profoundly benefited nuclear physics researchers since they now can perform detailed pulse processing for applications such as gamma-ray tracking and decay-event selection and reconstruction. In this talk, present state-of-the-art digital readout electronics and its applications in a variety of nuclear science fields will be discussed, and future directions in hardware development for digital electronics will also be outlined, all from the prospective of a commercial manufacturer of digital electronics. [Preview Abstract] |
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