Bulletin of the American Physical Society
2005 2nd Joint Meeting of the Nuclear Physics Divisions of the APS and The Physical Society of Japan
Sunday–Thursday, September 18–22, 2005; Maui, Hawaii
Session KD: Mini-symposium on New Technology in Gamma Ray Detection |
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Sponsoring Units: DNP JPS Chair: Mark Riley, Florida State University Room: Ritz-Carlton Hotel Salon 1 |
Thursday, September 22, 2005 2:00PM - 2:30PM |
KD.00001: Overview of gamma ray tracking Invited Speaker: Gamma ray energy tracking is a new concept for a detector array with unprecedented capabilities. In this type of detector, the position and energy of individual interactions of all the gamma rays are identified, and the scattering sequences of the gamma rays are reconstructed. Such an array will give high peak efficiency, peak-to-background ratio, and position resolution. A number tracking detector projects have been started recently in US, Japan, Canada and Europe. In this talk I will present physics opportunities provided by tracking detectors, and review the recent progress of the construction projects, including the production and testing of segmented detector, the use of digital electronics for signal processing, results from an in-beam experiments, and design efforts for various subsystems. [Preview Abstract] |
Thursday, September 22, 2005 2:30PM - 2:45PM |
KD.00002: A digital signal decomposition algorithm for GRETINA David Radford Energy-tracking arrays such as GRETINA and AGATA will be the next generation of detector systems for in-beam gamma-ray spectroscopy. They depend on digital pulse processing to extract the positions and energies of multiple interactions in segmented high-purity Ge detectors. This processing makes use of digitized signals both from the hit segments themselves, and the induced image charges in neighboring segments. The complex algorithms involved make this process the major computational bottleneck for these detectors, requiring a computer farm at least of the order of 100 high-speed processors. For GRETINA, candidate algorithms for signal decomposition include Adaptive Grid Search, Singular Value Decomposition, and Sequential Quadratic Programming. Current work on the development of the algorithm, and verification of its efficacy and resolution, will be described. [Preview Abstract] |
Thursday, September 22, 2005 2:45PM - 3:00PM |
KD.00003: Gamma-Ray detector Array with Position and Energy sensitivity (GRAPE) E. Ideguchi, S. Shimoura, M. Niikura, M. Tamaki, H. Iwasaki, H. Sakai, T. Fukuchi, H. Baba, M. Kurokawa, S. Michimasa, S. Ota We have constructed a Ge detector array, GRAPE, for high- resolution in-beam gamma-ray spectroscopy using RI beams. In order to correct for the Doppler broadening effect from the moving gamma-ray emitters, the array was designed to have position sensitivities in the Ge crystal. The total array consists of 18 detectors and each of which contains twe Ge planar crystals with effective radius of 3 cm and thickness of 2 cm. One side of crystal has 3 $\times$ 3 segmented electrodes. The planar structure and the segmented electrodes enable us to extract the position information based on a pulse- shape analysis. The resolution of less than 1\% for v/c = 0.3 can be achieved after Doppler shift correction. Total efficiency of 5\% for 1 MeV gamma ray is expected. First-phase electronics using conventional analog techniques for pulse shape analysis has been completed. Overall performance of the system with the first-phase electronics was evaluated in the physics experiments using RI beams. As a second phase data acquisition, a system for pulse shape sampling using flash ADC was tested. R\&D of pulse shape analysis based on an artificial neural network algorithm was initiated by using the digital pulse-shape data. We will present current status of GRAPE. [Preview Abstract] |
Thursday, September 22, 2005 3:00PM - 3:15PM |
KD.00004: Sub-segment position measurement in 32-fold segmented high-purity germanium detectors D.-C. Dinca, C.M. Campbell, J.M. Cook, T. Glasmacher Sub-segment position resolution of gamma-ray interactions has been demonstrated for the cylindrically-symmetric 32-fold segmented HPGe detectors of the NSCL/MSU Segmented Germanium Array (SeGA) using digital electronics. Flash ADCs sampled waveforms at 100 MHz to measure both real and induced charges from the outer contact segments of a SeGA detector. To bypass issues with computation and bandwidth, integral quantities based on short (1-2 $\mu $sec) waveform samples were used. Analysis of induced charges on segments neighboring those with real charge deposition allowed for sub-segment position resolution along both the crystal's linear axis and the azimuthal angle. Multiple measures of the real charge signal's rise time allowed for determination of the radial position. [Preview Abstract] |
Thursday, September 22, 2005 3:15PM - 3:30PM |
KD.00005: Progress and Physics with planar germanium strip detectors (HpGeDSSDs) C.J. (Kim) Lister Large area position-sensitive planar germanium wafers potentially offer great promise in many areas of science, including nuclear structure research, medical and material imaging, space science, and homeland security. However, implementation of large, efficient, robust and high resolution counters has proven difficult and progress has been slow. I will report on several projects which have demonstrated the practical applications of these devices, including performing excellent Doppler correction, measuring linear polarizations, and the construction of a digital Compton camera. I will also review the considerable technical improvements being undertaking that will lead to improved devices in the future which will be more useful for widespread use. [Preview Abstract] |
Thursday, September 22, 2005 3:30PM - 3:45PM |
KD.00006: TIGRESS--The TRIUMF-ISAC Gamma-Ray Escape-Suppressed Spectrometer Paul Garrett, C. Andreoiu, D. Bandyopadhyay, P. Finlay, G.F. Grinyer, B. Hyland, A.A. Phillips, M.A. Schumaker, C.E. Svensson, A.A. Andreyev, G.C. Ball, R.S. Chakrawarthy, H. Cowan, G. Hackman, A.C. Morton, C.J. Pearson, M.B. Smith, R.A.E. Austin, A.J. Boston, H.C. Scraggs, T.E. Drake, J.P. Martin, F. Sarazin, J.C. Waddington, L.M. Watters TIGRESS is a next generation $\gamma$-ray spectrometer designed to be used at the TRIUMF radioactive beam facilities ISAC and ISAC-II. It will consist of 12 clover-geometry HPGe detectors that are suppressed with BGO-CsI anti-Compton shields. The outer contacts of each crystal is 8-fold segmented, including 2 longitudinal segments. The $\gamma$-ray interaction location is determined through analysis of pulse waveforms from the 32 outer contacts. Detailed coincidence scans of the prototype detector deduced a mean position sensitivity of 0.44 mm for single-interactions. Delivery of the production modules, with a slightly modified segmentation scheme, has commenced, and an in-beam test of the detector performance is currently scheduled for late July. Results of the characterization of the new production detectors, including a preliminary analysis of the ability to determine interaction locations in-beam, along with the performance of the suppression shield, will be presented. [Preview Abstract] |
Thursday, September 22, 2005 3:45PM - 4:00PM |
KD.00007: Tests of the GRETINA triple cluster prototype detector A.O. Macchiavelli, R.M. Clark, M. Cromaz, M.A. Deleplanque, M. Descovich, S. Ettenauer, P. Fallon, I.Y. Lee, E. Rodriguez-Vieitez, F.S. Stephens, D. Ward, M. Wiedeking The GRETINA prototype detector consists of a cluster of 3 tapered regular hexagonal HPGe capsules in a common cryostat. The Ge crystals have 36 segments (6 longitudinal x 6 transverse) and a central contact for a total of 111 channels, each instrumented with a cold FET stage. A number of tests have been performed and will be the subject of this presentation. Acceptance tests include: mechanical dimensions, liquid nitrogen holding time, and energy resolution. Characterization tests, which are of importance for the performance in tracking arrays, were carried out and include ``singles'' segment boundaries scans (Am --source) and ``coincidence'' scans for pulse shape analysis (Cs source). Preliminary results of an in-beam experiment using the reaction $^{12}$C($^{82}$Se,4n)$^{90}$Zr at 285MeV establish a position resolution (RMS) of $\sigma \quad \sim $2mm . [Preview Abstract] |
Thursday, September 22, 2005 4:00PM - 4:15PM |
KD.00008: Development and demonstration of gamma-ray tracking based Compton imaging instruments Kai Vetter Recent developments in the manufacture of large and two-dimensionally segmented, high-resolution Si and Ge detectors along with advances in digital signal processing enable the implementation of compact and highly sensitive Compton imaging spectrometers. A hybrid system of low-Z material such as Si and a higher Z material such as Ge promises a high Compton imaging sensitivity between 100keV and several MeV, which is an energy range of significant interest for applications in homeland security, astrophysics, and nuclear medicine. The excellent energy resolution of the low-temperature detectors being used provide isotope identification and spectroscopic background suppression as well as excellent imaging capabilities. The imaging capability of a Compton camera not only enables to localize and image radioactive sources but also enables to potentially increase the sensitivity in finding weak or hidden gamma-ray sources by increasing the signal-to-background ratio in the image. [Preview Abstract] |
Thursday, September 22, 2005 4:15PM - 4:30PM |
KD.00009: Development of Position Sensitive Germanium Detector Tomonori Fukuchi, Susumu Shimoura, Eiji Ideguchi, Meiko Kurokawa, Hidetada Baba, Shinsuke Ota, Mitsuru Tamaki, Megumi Niikura We have been developing the Gamma-Ray detector Array with Position and Energy sensitivity (GRAPE) which is mainly used for detecting $\gamma$-rays from fast moving nuclei. The GRAPE consists of 18 high-purity Germanium (Ge) detectors. All detectors have two planar-type Ge crystals (60 mm in diameter and 20 mm thickness). The electrode of Ge crystal is segmented in 3 $\times$ 3. The pulse shape analysis enable three-dimensional position determination. We applied an artificial neural network (ANN) algorithm for pulse shape analysis. An advantage of the ANN technique is rapid pattern recognition with an appropriate training in advance. We aim to extract the interacting position of $\gamma$-rays online using the ANN algorithm. In order to make a supervisory data set for training the ANN, the pulse shape sampling was performed using the flash-ADCs with a sampling rate of 100 MHz. However, the pulse shape sampling takes long time, therefore a fast sampling method using the Compton scattering kinematics was proposed. This method cope with the individual character of each detector and the change of a detector response as years go by. [Preview Abstract] |
Thursday, September 22, 2005 4:30PM - 4:45PM |
KD.00010: Multitracer imaging by strip germanium telescope Shinji Motomura, Shuichi Enomoto, Hiromitsu Haba, Yasuyuki Gono, Yasushige Yano In multitracer method, a tracer reagent that contains multiple nuclide (multitracer) is injected into samples such as plants or small animals. In order to examine the possibility of nondestructive imaging of the multitracer, we have fabricated a Compton camera including two double-sided strip germanium detectors. For image reconstruction, we are currently trying a linear model between the real image and an intermediate image referred to as a simple back-projection (SBP) image. When the number of the detected events is sufficiently large, the SBP image is regarded as being constructed by convoluting a blur and the real image. If we assume that the blur is invariant anywhere in the real image space, the real image can be reconstructed analytically. However, the blur varies depending on the position in the real image space. Therefore, the analytical method is relevant only in a restricted region. Thus we have implemented an iterative method in which the variation in the blur can be incorporated. In this talk the imaging performance of the current model of the Compton camera will be presented. [Preview Abstract] |
Thursday, September 22, 2005 4:45PM - 5:00PM |
KD.00011: R\&D of a low background cosmic Hard X-ray Imager with a Position Sensitive PMT and an Active Coded Mask Shinya Hirakuri, Motohide Kokubun, Takeshi Itoh, Takayuki Yanagida, Ryohei Miyawaki, Kazuo Makishima, Shin Kubo, Tsuneo Honda A new low background cosmic hard X-ray imager has been developed, based on the Hard X-ray Detector (HXD-II) which is one of the scientific payloads on board the 5th Japanese cosmic X-ray satellite \textit{Astro-E2} (scheduled for launch in June 2005). The imager incorporates one of the basic design concepts of the HXD-II, namely tight well-shaped active shields. Furthermore, it has an imaging capability (unlike the HXD-II), using a coded mask and a position-sensitive main detector. In order to reduce the background, the mask is made of active elements. First we made a prototype model, of which the main detector consists of a 64ch flat panel position sensitive photomultiplier (FP-PMT:HAMAMATU H8500) and an 8 $\times$ 8 array of CsI scintillator cubes of 5 mm in one dimension each. Reading out its 64 anode outputs by 8 of resister chains, we achieved a spatial resolution of about 5 mm (digitized). To improve the spatial resolution, we have adopted 256ch FP-PMT (HAMAMATU H9500) and are developing a readout unit which can acquire its 256 anode outputs, pixel by pixel, using analog LSI chips (ideas VA32 TA32). [Preview Abstract] |
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