Bulletin of the American Physical Society
2015 Fall Meeting of the APS Division of Nuclear Physics
Volume 60, Number 13
Wednesday–Saturday, October 28–31, 2015; Santa Fe, New Mexico
Session JJ: Mini-Symposium on Digital Signal Processing in Nuclear Physics Experiments |
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Chair: Robert Grzywacz, University of Tennessee Room: Coronado |
Friday, October 30, 2015 10:30AM - 11:06AM |
JJ.00001: Digital Signal Processing in the GRETINA Spectrometer Invited Speaker: Mario Cromaz Developments in the segmentation of large-volume HPGe crystals has enabled the development of high-efficiency gamma-ray spectrometers which have the ability to track the path of gamma-rays scattering through the detector volume. This technology has been successfully implemented in the GRETINA spectrometer whose high efficiency and ability to perform precise event-by-event Doppler correction has made it an important tool in nuclear spectroscopy. Tracking has required the spectrometer to employ a fully digital signal processing chain. Each of the systems 1120 channels are digitized by 100 Mhz, 14-bit flash ADCs. Filters that provide timing and high-resolution energies are implemented on local FPGAs acting on the ADC data streams while interaction point locations and tracks, derived from the trace on each detector segment, are calculated in real time on a computing cluster. In this presentation we will give a description of GRETINA's digital signal processing system, the impact of design decisions on system performance, and a discussion of possible future directions as we look towards soon developing larger spectrometers such as GRETA with full 4$\pi$ solid angle coverage. This work was supported by the Office of Science in the Department of Energy under grant DE-AC02-05CH11231. [Preview Abstract] |
Friday, October 30, 2015 11:06AM - 11:18AM |
JJ.00002: The digital data acquisition system for the implantation-decay station at the Fragment Mass Analyzer Dariusz Seweryniak, John T. Anderson, Michael P. Carpenter, Helena M. David, Michael Albers, Akaa Ayangeakaa, Calem R. Hoffman, Robert V.F. Janssens, Torben Lauritsen, Timothy Madden, Michael Oberling, Philip Wilt, Shaofei Zhu The implantation-decay station developed for the Argonne Fragment Mass Analyzer (FMA) is an essential tool for studies of exotic nuclei far from the line of stability at ATLAS. It consists of various focal plane detectors, a 160X160 double-sided Si strip detector, a Si ``tunnel'' detector, and an array of Ge clover detectors. In order to make it sensitive to rapidly-decaying nuclei and in order to increase its count-rate capability it was equipped with a digital data acquisition system which processes waveforms by employing 14-bit, 100-MHz digitizers designed originally for the GRETINA gamma-ray tracking array. However, a new digitizer and trigger firmware was developed to optimize the system for decay spectroscopy and to integrate it with the digital DAQ developed for Gammasphere. Among the first results, short-lived isomers in $^{\mathrm{254}}$Rf were observed for the first time in two separate experiments with either the FMA or the Berkeley Gas-Filled Separator. [Preview Abstract] |
Friday, October 30, 2015 11:18AM - 11:30AM |
JJ.00003: The new digital data acquisition system for Gammasphere M.P. Carpenter, M. Albers, J.T. Anderson, A. Ayangeakaa, H.M. David, C.R. Hoffman, R.V.F. Janssens, T. Lauritsen, T. Madden, M. Oberling, D. Seweryniak, P. WIlt, S. Zhu A new digital-based data acquisition system (DAQ) for Gammasphere has been developed. This system leverages the electronics designed for the GRETINA collaboration. At the center of this development are the GRETINA 10-channel digitizer modules which handle the Ge preamp signals at a 100MHz rate, and master trigger and router modules which allow triggers to be constructed from information obtained from the digitizer channels [1]. The new DAQ increases event throughput significantly over the existing system while addressing multiple repair and maintenance issues. New hardware and firmware to integrate the DAQ with Gammasphere and its suite of ancillary detectors has been developed allowing for a seamless changeover from the analog DAQ to the new digital system. An overview of the system and illustrative results from several recent experiments will be presented. This material is based on work supported by the DOE, Office of Science, Office of Nuclear Physics under Contract No. DE-AC02-06CH11357. \\[4pt] [1] J.T. Anderson et al., IEEE Transactions on Nuclear Science, vol. 56, issue 1, pp. 258-265. [Preview Abstract] |
Friday, October 30, 2015 11:30AM - 11:42AM |
JJ.00004: Architecture and Performance of the Nab DAQ Aaron Sprow, Christopher Crawford The Nab experiment is being constructed to measure the electron-neutrino angular correlation in neutron beta decay. A precise time-of-flight measurement to determine the energy of a proton and a measurement of the energy deposited by an electron in coincidence are required to meet the target precision of $\Delta a/a\simeq 1\times10^{-3}$. Using the National Instruments PXIe-5171R, a new DAQ architecture, in which the level 2 trigger logic is removed by digitizing to continuous local ring buffers and migrating global coincidence logic to CPU software, has been developed. This new DAQ scheme results in a simpler, more flexible system. The full 2-chassis, 256-channel system has been constructed, and production grade firmware has been developed. The results of studies to characterize the DAQ performance and a discussion of improvements will be presented. [Preview Abstract] |
Friday, October 30, 2015 11:42AM - 11:54AM |
JJ.00005: Practical Experience of Signals Processing Using Digitizers Mark Sikora, Mohammad Ahmed Experiments at HI$\gamma$S and TUNL are increasingly replacing analog electronics with digitizers. This overhaul requires offline algorithms to extract experimental observables from the raw detector waveforms. The new routines must be tailored to the unique characteristics of the detector output and in the context of the pulsed time structure of the beams produced at the two labs. To date, data has been collected and analyzed using NaI, LaBr$_3$, high-purity germanium, and organic liquid scintillator detectors in both neutron and photon experiments. The algorithms which have been developed in the course of this analysis will be presented. [Preview Abstract] |
Friday, October 30, 2015 11:54AM - 12:06PM |
JJ.00006: Bayesian signal processing of pulse shapes for background rejection in the \textsc{Majorana Demonstrator} Benjamin Shanks The \textsc{Majorana Demonstrator} uses high purity germanium (HPGe) detectors in the p-type point contact (PPC) geometry to search for neutrinoless double-beta decay ($0\nu\beta\beta$) in $^{76}$Ge. Due to the unique electric potential created within the PPC geometry, the detailed pulse shape depends on the number of energy depositions contained within a given event. Pulse shape analysis (PSA) techniques can be used to estimate the number of separate depositions which combine to form a single pulse. This information can be used to discriminate between $0\nu\beta\beta$ candidate events, which deposit energy at a single detector site, and gamma ray background, which can scatter and deposit energy in multiple locations. The problem of determining whether a pulse is single- or multi-site is well suited to Bayesian classifiers. Once trained via supervised machine learning, these algorithms can perform nonlinear cuts against multi-site events using the estimated probability function as a discriminator. The Bayesian approach can also be naturally extended to incorporate a model of the physical process responsible for signal generation within the detector. Presented here is an overview of the Bayesian classifier developed for use on the \textsc{Demonstrator}. [Preview Abstract] |
Friday, October 30, 2015 12:06PM - 12:18PM |
JJ.00007: Digital Electronics for Nuclear Physics Experiments Wojtek Skulski, David Hunter, Eryk Druszkiewicz, Dev Ashish Khaitan, Jun Yin, Frank Wolfs Future detectors in nuclear physics will use signal sampling as one of primary techniques of data acquisition. Using the digitized waveforms, the electronics can select events based on pulse shape, total energy, multiplicity, and the hit pattern. The DAQ for the LZ Dark Matter detector, now under development in Rochester, is a good example of the power of digital signal processing. This system, designed around 32-channel, FPGA-based, digital signal processors collects data from more than one thousand channels. The solutions developed for this DAQ can be applied to nuclear physics experiments. [Preview Abstract] |
Friday, October 30, 2015 12:18PM - 12:30PM |
JJ.00008: A Digital Data Acquisition for VANDLE Miguel Madurga, S. Paulauskas, Robert Grzywacz, David Miller, Stephen Padgett, Hui Tan Neutron energy measurements can be achieved using time-of-flight (ToF) techniques. A digital data acquisition system was developed for reliable ToF measurements with subnanosecond timing resolution based on digitizers with 10ns and 4 ns sampling periods using pulse shape analysis algorithms. A validation procedure was developed to confirm the reliability. The response of the algorithm to photomultiplier signals was studied using a specially designed experimental system based on fast plastic scintillators. The presented developments enabled digital data acquisition systems to instrument the recently developed Versatile Array of Neutron Detectors at Low-Energy (VANDLE)[1,2].\\[4pt] [1] C. Matei et al., Proceedings of Science, NIC X, 138 (2008)\\[0pt] [2] S. V. Paulauskas et al., NIMA 797, 22 (2014) [Preview Abstract] |
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