| 1. |
- Balcerzyk, M., et al.
(författare)
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Energy resolution and light yield non-proportionality of ZnSe : Te scintillator studied by large area avalanche photodiodes and photomultipliers
- 2002
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - 0168-9002 .- 1872-9576. ; 482:3, s. 720-727
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Tidskriftsartikel (refereegranskat)abstract
- The ZnSe: Te scintillator has been studied by means of a photomultiplier with an extended bialkali photocathode, a large area avalanche photodiode (LAAPD) and a PIN photodiode. The light output was determined to be 28 300+/-1700 photons/MeV. Results indicate good proportionality for light output versus gamma-ray energy. Measurements of the 662 keV gamma-ray energy spectrum recorded using a LAAPD resulted in an energy resolution of 5.4+/-0.3%. Based on these results, an intrinsic energy resolution of 3.3+/-0.7% has been calculated.
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| 2. |
- Bäck, Torbjörn, et al.
(författare)
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A TOF-PET system for educational purposes
- 2002
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier. - 0168-9002 .- 1872-9576. ; 477, s. 82-82
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Tidskriftsartikel (refereegranskat)abstract
- A TOF-PET system has been designed and constructed for educational purposes. The aim of this system is to demonstrate the possibilities of positron emission tomography in general and the time-of-flight method in particular to the students of various courses at the Royal Institute of Technology, Stockholm, Sweden. The set-up consists of 48 small BaF2 crystals coupled to fast photomultipliers placed in a ring geometry. The signals of the photomultipliers are fed into fast constant fraction discriminators (CFD). The outputs of these are directed to a specially designed logic VME unit. which combines the CFD signals of 6 neighbouring channels to one signal by adding a different delay to each channel. The logic circuitry produces a prompt pulse for each event that serves as the start pulse for the 8-channel fast TDC. The delayed pulses act as the stop pulses for the TDC. In a computer. the measured times are converted into information about which the photomultipliers fired with the difference in the time of flight. The set-up is described and the results are presented.
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| 3. |
- Bäck, Torbjörn, et al.
(författare)
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An educational tool for demonstrating the TOF-PET technique
- 2001
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : AMERICAN PHYSICAL SOC. - 0168-9002 .- 1872-9576. ; 471:1-2, s. 200-204
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Tidskriftsartikel (refereegranskat)abstract
- A detector system for positron emission tomography with time-of-flight capability has been built to serve as an educational tool for undergraduate students. The set-up consists of 48 BaF2 scintillator crystals, each coupled to a fast photo-multiplier tube, mounted in a circular geometry. The analogue detector pulses are handled by fast constant fraction discriminators. A dedicated unit reduces the 48 channels to eight channels via delay-fine encoding, and the signals are then fed to an eight channel fast time-to-digital converter. A VME processor sorts the events and sends them to a workstation where the coincident events are extracted. The time resolution of the detectors together with fast VME based electronics allows for time-of-flight measurements to improve on the signal-to-noise ratio in the, reconstructed images. The system can be used for different types of exercises for the students, varying from the fundamentals of scintillator detectors to advanced image reconstruction. The set-up is described and some results are presented. (C) 2001 Elsevier Science B.V. All rights reserved.
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| 4. |
- Klamra, Wlodzimierz, et al.
(författare)
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Response of BaF2 and YAP : Ce to heavy ions
- 2000
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - 0168-9002 .- 1872-9576. ; 444:3, s. 626-630
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Tidskriftsartikel (refereegranskat)abstract
- The light output and energy resolution for BaF2 and YAP:Ce have been measured with O-16, Cl-35 and Br-79 in the energy region 8.5-34 MeV. Both crystals show a nonproportional light yield response, mostly pronounced for the lighter ions.
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| 5. |
- Klamra, Wlodzimierz, et al.
(författare)
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Studies of scintillation light nonproportionality of ZnSe(Te), CsI(Tl) and YAP(Ce) crystals using heavy ions
- 2002
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - 0168-9002 .- 1872-9576. ; 484:03-jan, s. 327-332
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Tidskriftsartikel (refereegranskat)abstract
- The scintillation light yield for ZnSe(Te), CsI(T1) and YAP(Ce) crystals have been studied with alpha particles, C-12 and Br-81 in the energy region 2.8-42.2 MeV. A nonproportional behavior was observed, mostly pronounced for alpha particles on YAP(Ce). The results are understood in terms of delta-rays effect.
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| 6. |
- Moszynski, M., et al.
(författare)
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Application of large area avalanche photodiodes to study scintillators at liquid nitrogen temperatures
- 2003
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - 0168-9002 .- 1872-9576. ; 504:03-jan, s. 307-312
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Tidskriftsartikel (refereegranskat)abstract
- Properties of Large Area Avalanche Photodiodes (LAAPDs) at liquid nitrogen (LN2) temperatures in application to study pure NaI, CsI and BGO scintillators are presented. All the tested crystals exhibited excellent performance at LN2 temperatures reflected by a high light output and very good energy resolution. The study showed that the LAAPD operating at LN2 temperatures is an excellent light readout device for testing different scintillators at low temperatures.
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| 7. |
- Moszynski, M., et al.
(författare)
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Energy resolution and light yield non-proportionality of pure NaI scintillator studied with large area avalanche photodiodes at liquid nitrogen temperatures
- 2002
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - 0168-9002 .- 1872-9576. ; 486:02-jan, s. 13-17
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Tidskriftsartikel (refereegranskat)abstract
- The pure NaI crystal has been studied using a Large Area Avalanche Photodiode (LAAPD) at near liquid nitrogen (LN2) temperatures. The study showed a high light output of 44000+/-4000 photons/MeV (ph/MeV), the energy resolution of 5.9 +/- 0.2% for 661.6 keV gamma-rays from a Cs-137 source and a good proportionality of the light yield versus gamma-ray energy. It has been shown also that a cooled LAAPD is an excellent photodetector to study scintillators at near LN2 temperatures.
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| 8. |
- Moszynski, M., et al.
(författare)
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Intrinsic energy resolution of pure NaI studied with large area avalanche photodiodes at liquid nitrogen temperatures
- 2003
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - 0168-9002 .- 1872-9576. ; 505:02-jan, s. 63-67
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Tidskriftsartikel (refereegranskat)abstract
- The energy resolution and non-proportionality of the light yield vs gamma-ray energy of pure NaI scintillators directly coupled to Large Area Avalanche Photodiodes (LAAPDs) and cooled down to the liquid nitrogen temperatures have been studied. Large improvements of energy resolution and nearly proportional light yield response have been obtained at very long shaping time constants. Energy resolution of 3.8+/-0.1% for 662 keV gamma-rays from a Cs-137 source was recorded at 50 mus integration time. The intrinsic resolution of the crystal vs energy of gamma-rays has been estimated by measurements of the number of primary electron-hole pairs generated in LAAPD by scintillation light.
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| 9. |
- Pausch, G., et al.
(författare)
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RoSiB - a 4 pi silicon ball for charged-particle detection in EUROBALL
- 2000
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - 0168-9002 .- 1872-9576. ; 443:03-feb, s. 304-318
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Tidskriftsartikel (refereegranskat)abstract
- A 4 pi silicon bail for detection and identification of light charged particles in large multidetector gamma-arrays as EUROBALL is presented. The design is based on a N = 42 ball with 12 pentagons and 30 hexagons as used in the GASP array. The absorptive material for gamma-rays is minimized to the detector thickness of 300 or 500 mu m and a 0.63 mm ceramic backing. The geometrical coverage is designed for about 90% of 4 pi. A pulse shape discrimination method with totally depleted detectors working in the reverse mount allows identifying protons and alpha-particles above an energy threshold of about 2 MeV. The performances of the ball were rested at the tandem - booster accelerator combination of the MPI Heidelberg in two experiments using the high-recoil reaction of 228 MeV Ni-58 + Ti-46 and the low-recoil reaction of 95 MeV O-16 + Ni-58. The two-dimensional spectra of zero-crossing (ZC) versus energy confirmed an excellent discrimination of protons and alpha-particles in all the detectors at different angles. The energy spectra of protons and alpha-particles measured in the experiments are presented. too. The gamma-spectra measured in coincidence with various combinations of emitted particles showed a high selectivity of the ball. The reduced total efficiency for protons of 59% and 55% and alpha-particles of 44% and 32% measured in a nuclear spectroscopy application is analyzed in a Monte-Carlo simulation (GEANT). It is due to a combined influence of a thick target needed to stop the recoiling residual nuclei and thick absorbers needed to protect the Si-detectors from scattered beam. The results along with the GEANT extrapolation to optimum experimental conditions confirm that RoSiB is a highly efficient and selective device for identification of rare reaction channels with heavy ions.
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| 10. |
- Sipos, A., et al.
(författare)
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Visualization of neutron and proton induced particle production in a CMOS image sensor
- 2003
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - 0168-9002 .- 1872-9576. ; 509:03-jan, s. 328-332
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Tidskriftsartikel (refereegranskat)abstract
- A commercially available off the shelf CMOS Image Sensor was irradiated with neutron and proton beams. The Image Sensor is equipped with standard video output. The data were collected on VHS videotapes and analyzed off-line after digitization. The camera chip with 110 000 pixels each having 12 x 12 mum(2) size, shows the nuclear reactions occurring in the sensitive layer as bright spots or tracks. Several applications are suggested based on the inexpensive CMOS Image Sensor.
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