| 1. |
- Hidvegi, Attila, et al.
(author)
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A high-speed data acquisition system for segmented Ge-detectors
- 2007
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In: 2006 IEEE Nuclear Science Symposium Conference Record, Vol 1-6. - : IEEE. - 1424405610 - 9781424405619 - 1424405602 ; , s. 999-1001
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Conference paper (peer-reviewed)abstract
- When using segmented Ge-detectors for gamma ray tracking it is necessary to determine the segment pulse shapes with high accuracy. A high-speed data acquisition system with many channels, high precision and with high sampling rate is required. To find the optimum performance, we are investigating what can be achieved by a system with extremely high sampling rates, 10 bits @2GS/s. There are many other applications for such a system. Higher sampling rates usually mean lower bit resolution of the ADC, but with oversampling we expect to achieve a very good energy and time resolution. The system uses high performance FPGAs (Xilinx Virtex-IV) to cope with the data rates delivered by the high speed ADCs and to make all the data processing onboard in real time. Control and monitoring is implemented in an embedded soft processor. This processor is also in charge of the offboard gigabit Ethernet communication. The final system will consist of several separate boards, each with a number of input channels that will have to communicate with each other in real time over a high-speed communication link. The processed result will be transmitted over Ethernet to final storage. The project introduces many challenging issues, which are being addressed in turn with different prototype designs. These issues are: the ADC performance, interfacing the ADCs to the FPGA, implementing the flexible processing algorithms and high speed interconnection between the boards.
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| 2. |
- Uher, J, et al.
(author)
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Highly sensitive silicon detectors of thermal neutrons
- 2007
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In: Nuclear Science Symposium Conference Record, 2006. IEEE. Vol 3.. - : IEEE conference proceedings. - 1424405602 - 9781424405619 ; , s. 1346-1348
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Conference paper (peer-reviewed)abstract
- Planar semiconductor diodes supplemented with a layer of an appropriate neutron converter such as 6LiF can be used for thermal neutron counting or imaging. Neutrons interacting in the converter generate alphas and tritons which enter the semiconductor and are detected there. However, simple planar devices suffer from limited detection efficiency which cannot reach more than about 5%. The limit in detection efficiency can be overcome by etching a 3D microstructure of trenches, pores or columns in the detector and filling it with the neutron converter. The overall neutron detection efficiency of such structure with pores was simulated. The results indicate an increase in the detection efficiency by factor of 6 in comparison with a standard planar neutron detector. Samples with different silicon column sizes were fabricated to study the electrical properties of 3D structures. The charge collection efficiency in silicon columns from 10 μm to 800 μm wide and 80 μm high was measured. Single pad detectors with pores were also fabricated and tested for thermal neutron detection. The samples have square pores of 20 μm wide, ~60 μm deep. The pore pitch is 70 μm. 6LiF was used as the neutron converter in all cases. Pulse height spectra of the filled samples irradiated by thermal neutrons were measured. The measurement proved functionality of such detectors and its usability for thermal neutron detection.
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| 3. |
- Bauer, Florian, 1975-, et al.
(author)
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Evaluation of a Micro-Channel Plate PMT in PET
- 2006
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In: Nuclear Science Symposium Conference Record, 2006, IEEE. - 1424405602 ; , s. 2503-2505
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Conference paper (peer-reviewed)abstract
- The focus of this paper is the evaluation of micro-channel plate PMTs for PET detectors. Several properties of MCPs make them interesting for PET applications, such as fast time response, high spatial resolution, compact size, low susceptibility to magnetic fields, high gain and low power consumption. The preliminary tests in this paper are performed with the 51 mm times 51 mm square Burle 85011-501 assembly with 64 anodes (8 times 8). A new version of this MCP will be examined for the full paper. Initial measurements have been performed with a pulsed LASER (Hamamatsu Picosecond Light Pulser PLP-10 with M8903 Laser diode head). The engineering sample of the 85011 exhibited a time resolution of 26 ps. Further measurements will be performed, such as transit time measurements and timing measurements with scintillators. Single-photon timing measurements were presented earlier in [Ref. 1], from the old version as well as the suitability of the device in Cherenkov detectors in [Ref. 2]. For the full paper it is also planned to develop a circuit which allows lossless splitting of the anode signal.
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| 4. |
- Di Mauro, A., et al.
(author)
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A New GEM-like Imaging Detector with Electrodes Coated with Resistive Layers
- 2006
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In: 2006 IEEE NUCLEAR SCIENCE SYMPOSIUM CONFERENCE RECORD, VOL 1-6. - : IEEE. - 9781424405619 ; , s. 3852-3859
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Conference paper (peer-reviewed)abstract
- We have developed and tested several prototypes of GEM-like detectors with electrodes coated with resistive layers. These detectors can operate stably at gains close to 10(5) and if discharges appear at higher gains the protective layers restrict their energies so that they do not damage either the detector or the readout electronics. We discovered that the cathodes of these detectors could be coated by CsI layers and in such a way the detectors gain high efficiency for the UV photons. We also demonstrated that such detectors can operate stably in the cascade mode and high overall gains (similar to 10(6)) are reachable. This opens applications in several areas, for example in RICH or in noble liquid TPCs. The simplified prototype of the RICH detector was built and successfully tested in the laboratory. The first results of operation of the new detectors at cryogenic temperatures are given.
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| 5. |
- Emri, M., et al.
(author)
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Software development framework supporting multimodal tomographic imaging
- 2007
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In: 2006 IEEE Nuclear Science Symposium Conference Record. - : IEEE. - 1424405610 - 9781424405619 ; , s. 1857-1859
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Conference paper (peer-reviewed)abstract
- Engineers specialized in multimodal tomography regularly face a wide scale of programming tasks requiring an integrated software system to ensure cost efficiency. Accordingly, a software development framework has been worked out comprising libraries for cluster-based data acquisition, image reconstruction, management of data files and complex multimodal volumetric visualization. This framework enabled us to develop complex software for our miniPET project [1]. This software contains a graphical application integrating data acquisition, cluster monitoring, event sorting, image reconstruction, interactive image processing tools for advanced multimodal visualization. It also contains utilities to solve these tasks without graphical user interface. The components of our acquisition program can run on embedded Linux systems making new ways to develop any other types of data acquisition software that uses embedded Linux systems. A versatile development framework is developed containing specific libraries and special file formats that support multimodal tomography. This framework was successfully used to elaborate our complex miniPET software.
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| 6. |
- Gavler, Sara Bergenius, et al.
(author)
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Fluctuation studies and energy reconstruction in a segmented calorimeter
- 2006
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In: 2006 IEEE Nuclear Science Symposium Conference Record. - : IEEE. - 9781424405619 ; , s. 177-181
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Conference paper (peer-reviewed)abstract
- In order to better understand energy estimation of electromagnetic showers in segmented calorimeters, detailed Geant4 simulation studies of electromagnetic showers in the energy range 1-100 GeV in CsI have been performed. When sampled in layers of 1.99 cm thickness, corresponding to 1.08 radiation lengths, the energy fluctuations in the samples show distributions that vary significantly with depth. The energy distributions are similar for incident electrons and photons and were found to change systematically along the shower, varying little with the initial energy. Three probability distributions have been fitted to the data: negative binomial, log-normal and Gaussian distributions, none of which gives a good fit over the full shower length. The obtained parameterizations might be useful in the use of the maximum likelihood method for estimating the energy. Two methods for estimating the energy have also been studied. One method is based on fitting individual longitudinal shower profiles with a G-function, the other one corrects the measured energy for leakage by utilizing the energy deposited in the last layer. Our simulations indicate that the last-layer correction method applied to photons and electrons of 1 and 10 GeV gives about a factor of 2 improvement in the energy resolution.
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| 7. |
- Imrek, J., et al.
(author)
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Development of an improved detector module for miniPET-II
- 2007
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In: 2006 IEEE Nuclear Science Symposium Conference Record. - : IEEE. - 1424405610 - 9781424405619 ; , s. 3037-3040
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Conference paper (peer-reviewed)abstract
- We present a new detector module developed for miniPET-II, the second generation of the miniPET small animal PET scanners. The improved module features new hardware components for better performance: LySO crystal material, increased number of crystal segments, Hamamatsu H9500 PSPMT, Xilinx Virtex-4 FPGA and Gigabit Ethernet. However, the principle of operation is the same: no hardware coincidence detection is implemented, data is acquired in list mode and transfered over an Ethernet network. The resulting new module is more suitable for full ring configurations.
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| 8. |
- Syntfeld-Kazuch, A., et al.
(author)
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Non-proportionality and Energy Resolution of CsI(Tl)
- 2007
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In: 2006 IEEE Nuclear Science Symposium Conference Record. - : IEEE. - 1424405610 - 9781424405619 ; , s. 1144-1149
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Conference paper (peer-reviewed)abstract
- Experimental studies of CsI(Tl) crystals with different amount of Tl activator are presented. Such properties like non-proportionality, energy resolution and number of photoelectrons per 1 MeV-γ were inspected at two different shaping time constants, i.e. 3 and 12 μs. A CsT(Tl) crystal was coupled to the XP5212 PMT with a photocathode blue sensitivity of 12.2μA/lmF. Six GsI(Tl) crystals of different size were tested. Among them three samples were of known Tl concentration which amounted roughly 0.05, 0.1 and 0.25 mol%. The data analysis showed much more proportional character of the crystal response, higher number of photoelectrons/MeV-γ, and what follows better overall energy resolution obtained for 12 μs time constant for all tested samples. Calculated intrinsic resolution improved at longer shaping time constant as well, indicating that for CsI(Tl) crystals more proportional response implies better intrinsic energy resolution of the host crystal. In contrast, intrinsic resolution at low energy region (below about 30 keV) deteriorated for the longer shaping time constant. An α/γ ratio was also measured for each tested CsI(Tl) crystal in order to find any indication to an explanation of the intrinsic resolution deterioration for low energy photons at the 12 μs integration time.
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