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The performance of a silicon drift detector (SDD) with an integrated FET, delivered by the company PNSensor, Munich, Germany, was studied in gamma spectrometry at room temperature (23-25[degrees]C) with a La[Br.sub.3]:Ce crystal of 6 mm diameter and 6 mm height. The SDD characteristics were compared with those measured with a Photonis XP5212 photomultiplier, a Large Area Avalanche Photodiode (LAAPD) of Advanced Photonix, Inc., and a Hamamatsu S3590-18 Photodiode (PD). Energy resolution versus gamma ray energies and its components related to the photoelectron/electron-hole pair statistics and dark noise were measured and compared. At low energies, below 100 keV, the light readout by the photomultiplier gives the best results, while for high energies, above 300 keV, the light readout by the SDD delivers superior energy resolution. In particular, the best energy resolution of 2.7 % was determined for 662 keV gamma rays from a [sup.137]Cs source. Index Terms--Avalanche photodiodes, energy resolution, La[Br.sub.3] scintillator, photomultipliers, pin photodiodes, silicon drift detectors.

A BC523A liquid scintillator loaded with boron-10 was tested as a detector for both fast and thermal neutrons. A pulse shape discrimination (PSD) method based on a zero-crossing principle was applied to distinguish between neutron and gamma radiation. High quantum efficiency Photonis XP5500B photomultiplier was used to enhance light detection from the scintillator. This allowed a good registration of the energy spectrum of neutron capture events on boron-10, corresponding to about 60 keV [gamma]-rays. The applied PSD method proved to be useful for n/[gamma] discrimination. A good resolving power of the method was achieved even without gating on neutron capture events. A comparison with a standard BC501A liquid scintillator was done to evaluate thermal neutrons detection efficiency in BC523A. Index Terms--Boron-10, liquid scintillators, neutron detection, zero-crossing method.

The performance of several BrilLanCe La[Br.sub.3] crystals that range in size from 06 x 6 [mm.sup.2] up to 038 x 38 [mm.sup.2] coupled to XP5212 and R6231MOD photomultipliers were studied, and in the case of the small crystals, the crystals were also coupled to large area avalanche photodiodes (LAAPD) of Advanced Photonix, Inc. First, the performance of several photomultipliers from Photonis and Hamamatsu with La[Br.sub.3] were compared to select the best one, not affecting energy resolution, besides the photoelectron statistics. The light output and energy resolution for 662 keV gamma rays from [sup.137] Cs source were measured for all crystals. Moreover, for some crystals, the non-proportionality of the light yield and energy resolution versus gamma ray energy were measured and the intrinsic resolution of the crystals was calculated. For the smallest crystals of 06 x 6 [mm.sup.2] further comparative tests with LAAPD were carried out. Index Terms--Avalanche photodiodes, energy resolution, La[Br.sub.3] scintillator, non-proportionality of the light yield, photomultipliers.

Compton camera prototype for a position-sensitive detection of prompt γ rays from proton-induced nuclear reactions is being developed in Garching. The detector system allows to track the Comptonscattered electrons. The camera consists of a monolithic LaBr3:Ce scintillation absorber crystal, read out by a multi-anode PMT, preceded by a stacked array of 6 double-sided silicon strip detectors acting as scatterers. The LaBr3:Ce crystal has been characterized with radioactive sources. Online commissioning measurements were performed with a pulsed deuteron beam at the Garching Tandem accelerator and with a clinical proton beam at the OncoRay facility in Dresden. The determination of the interaction point of the photons in the monolithic crystal was investigated.

The properties of CdW[O.sub.4] (CWO) crystals in gamma spectrometry were studied. Several small samples of 10 x 10 x 3 mm size, typically used in CT X-ray detectors, were tested and then compared to the performance of a larger crystal of 20 mm in diameter and 20 mm in height. The light output, energy resolution, and nonproportionality of the CWO response versus gamma-ray energy, were measured and compared with those of a small BGO to discuss further the origin of the intrinsic resolution of pure undoped scintillating crystals. A high light output of 6500 [+ or -] 200 phe/MeV and a good energy resolution of 6.6 [+ or -] 0.2% for 662 keV gamma rays from a [sup.137]Cs source were measured for the small samples coupled to an XP3212 photomultiplier. Common nonproportionality curves and consequently common intrinsic resolutions of small CWO and BGO suggest that they represent fundamental characteristics of the heavy oxide scintillating material themselves. Index Terms--CdW[O.sub.4], energy resolution, non-proportionality, scintillators.

Limitations of the pulse-shape discrimination (PSD) technique - a promising method to identify the charged particles stopped in planar Si-detectors - have been investigated. The particle resolution turned out to be basically determined by resistivity fluctuations in the bulk silicon which cause the charge-collection time to depend on the point of impact. Detector maps showing these fluctuations have been measured and are discussed. Furthermore we present a simple method to test the performance of detectors with respect to PSD. Another limitation of the PSD technique is the finite energy threshold for particle identification. This threshold is caused by an unexpected decrease of the total charge-collection time for ions with a short range, in spite of the fact that the particle tracks are located in a region of very low electric field.

Pulse-shape discrimination with totally depleted Si-detectors in reverse mount has been investigated and shown to be an excellent method of charged-particle identification in the energy range of [approximately equal to] 2 to 20 AMeV. In test experiments with heavy-ion beams we obtained element identification up to Ti and isotope resolution even for elements heavier than carbon. The promising results and the simplicity of the electronics recommend this technique for applications in multidetector arrays. In particular, small and compact 4[Pi] Si balls with relatively low thresholds for charged-particle identification to be combined with 4[Pi] neutron detectors or [Gamma] arrays can be constructed.

Range verification of particle beams in real time is considered a key for tapping the full potential of radio-oncological particle therapies. The novel technique of prompt gamma-ray timing (PGT), recently proposed and explored in first proof-of-principle experiments, promises range assessment at reasonable expense but challenges detectors, electronics, and data acquisition. Energy-selected time distributions have to be measured at very high throughput rates to obtain the statistics necessary for range verification with single pencil beam spots. Clinically applicable systems should provide a time resolution of about 200 ps, to be obtained with large (about 2” diameter) scintillators, detector loads in the few-Mcps range, and data acquisition rates around 1 Mcps, if possible with compact and inexpensive systems. Such requirements can be met best with CeBr3 scintillators read out with conventional photomultiplier tubes, coupled to commercial but customized electronics featuring high-resolution pulse digitization and fast digital signal processing. The paper deduces design parameters from the constraints given by typical treatment conditions, and presents first results obtained with prototype detectors and electronics developed in accordance with the derived specifications. [ABSTRACT FROM AUTHOR]

Proton and light ion beams are applied to the therapeutic irradiation of cancer patients due to the favorable dose deposition of these particles in tissue. By means of accelerated ions, a high dose can be accurately deposited in the tumor while normal tissue is spared. Since minor changes in the patient’s tissue along the beam path can compromise the success of the treatment, an in-vivo monitoring of the dose deposition is highly desired. Cameras detecting the prompt \gamma -rays emitted during therapy are under investigation for this purpose. Due to the energy spectrum of prompt \gamma -rays with a range between a few keV and several MeV, it is reasonable to consider the utilization of electron-positron pair production events to reconstruct the origin of these prompt photons. The combined use as a pair production and Compton camera is expected to increase its efficiency. We evaluated if a pair production camera could be suitable in this context by means of Monte-Carlo simulations. Modelling of the pair production events taking place in a prototype detector dedicated to Compton imaging were performed. We analyzed the efficiency of the detector system regarding pair production and Compton events. The most crucial property of this pair production camera is the angular resolution. The results of this work indicate that the spatial resolution of the considered detection system used as pair production camera is, for principal reasons, insufficient for an application to range assessment in particle therapy. Furthermore, the efficiency of the pair production camera under study is one order of magnitude lower than the efficiency of the setup applied to the detection of Compton events. [ABSTRACT FROM AUTHOR]

A functional prototype two-plane Compton camera array for localization and identification of remote radiation sources, consisting of four PVT and four NaI(Tl) scintillation detectors with PMT readout, is presented. The large-volume, 76\times 76\times 76\ \ mm scintillators provide a broad field of view for scattered photons and facilitate maximum efficiency at moderate cost. Each detector is equipped with a voxelSPEC, a compact electronic module that provides high voltage for the PMT, signal processing, detector stabilization, and an Ethernet communication interface. The voxelSPEC delivers list-mode event data with nanosecond precision timing over non-proprietary Ethernet and makes a system extension very easy. A software package has been developed for real-time data processing and image reconstruction. Advantages in the hard- and software allow stable, unattended operation of the camera array for many days, and provide easy-to-read information on the radiation source in real time. Measurements with the prototype array have been performed for a few standard scenarios and geometries to verify the model predications obtained by Monte-Carlo simulations. Simulations have been further performed to explore larger camera arrays with 2\times 4\times 4, 2\times 8\times 8, 2\times 10\times 10, 2\times 13\times 13 and 2\times 16\times 16 detectors. [ABSTRACT FROM PUBLISHER]

Non-proportionality of light yield and energy resolution of Compton electrons in three scintillators (LaBr3:Ce, LYSO:Ce and CsI:Tl) were studied in a wide energy range from 10 keV up to 1 MeV. The experimental setup was comprised of a High Purity Germanium detector and tested scintillators coupled to a photomultiplier. Probing the non-proportionality and energy resolution curves at different energies was obtained by changing the position of various radioactive sources with respect to both detectors. The distance between both detectors and source was kept small to make use of Wide Angle Compton Coincidence (WACC) technique, which allowed us to scan large range of scattering angles simultaneously and obtain relatively high coincidence rate of 100 cps using weak sources of about 10 \muCi activity. The results are compared with those obtained by direct irradiation of the tested scintillators with gamma-ray sources and fitting the full-energy peaks. [ABSTRACT FROM PUBLISHER]

A method based on the Compton coincidence technique was applied to study the energy resolution of Compton electrons in wide energy range. The experimental setup was comprised of a High Purity Germanium (HPGe) detector and a LaBr3:Ce scintillator coupled to a photomultiplier. The detectors were set in a face-to-face geometry and the source was placed between them. Thus gating on events backscattered in the scintillator and detected in HPGe allowed one to measure the energy resolution of Compton scattered electrons at an energy corresponding to the Compton edge for a given source. This study confirms the importance of the electron scattering (δ-rays) as the main component of the intrinsic resolution in scintillators. The results are particularly important for discussion of the light yield non-proportionality contribution to the energy resolution of scintillators. [ABSTRACT FROM AUTHOR]

The performance of a silicon drift detector (SDD) with an integrated FET, delivered by the company PNSensor, Munich, Germany, was studied in gamma spectrometry at room temper- ature (23-25°C) with a LaBr3 :Ce crystal of 6 mm diameter and 6 mm height. The SDD characteristics were compared with those measured with a Photonis XP5212 photomultiplier, a Large Area Avalanche Photodiode (LAAPD) of Advanced Photonix, Inc., and a Hamamatsu S3590-18 Photodiode (PD). Energy resolution versus gamma ray energies and its components related to the photoelectron/electron-hole pair statistics and dark noise were measured and compared. At low energies, below 100 keV, the light readout by the photomultiplier gives the best results, while for high energies, above 300 keV, the light readout by the SDD delivers superior energy resolution. In particular, the best energy resolution of 2.7% was determined for 662 keV gamma rays from a 137Cs source. [ABSTRACT FROM AUTHOR]

The performance of several BrilLanCe LaBr3 crystals that range in size from Oslash 6 times 6 mm2 up to Oslash 38 times 38 mm2 coupled to XP5212 and R6231MOD photomultipliers were studied, and in the case of the small crystals, the crystals were also coupled to large area avalanche photodiodes (LAAPD) of Advanced Photonix, Inc. First, the performance of several photomultipliers from Photonis and Hamamatsu with LaBr3 were compared to select the best one, not affecting energy resolution, besides the photoelectron statistics. The light output and energy resolution for 662 keV gamma rays from137 Cs source were measured for all crystals. Moreover, for some crystals, the non-proportionality of the light yield and energy resolution versus gamma ray energy were measured and the intrinsic resolution of the crystals was calculated. For the smallest crystals of Oslash 6 times 6 mm2 further comparative tests with LAAPD were carried out. [ABSTRACT FROM PUBLISHER]

The properties of CdWO4 (CWO) crystals in gamma spectrometry were studied. Several small samples of 10times10times3 mm size, typically used in CT X-ray detectors, were tested and then compared to the performance of a larger crystal of 20 mm in diameter and 20 mm in height. The light output, energy resolution, and nonproportionality of the CWO response versus gamma-ray energy, were measured and compared with those of a small BGO to discuss further the origin of the intrinsic resolution of pure undoped scintillating crystals. A high light output of 6500plusmn200 phe/MeV and a good energy resolution of 6.6plusmn0.2% for 662 keV gamma rays from a 137Cs source were measured for the small samples coupled to an XP3212 photomultiplier. Common nonproportionality curves and consequently common intrinsic resolutions of small CWO and BGO suggest that they represent fundamental characteristics of the heavy oxide scintillating material themselves [ABSTRACT FROM PUBLISHER]

Inclusive neutron energy spectra were measuredb y time of flight using 1.22 GeV antiprotons from LEAR, CERN, as projectiles andtargets from natural Al, Cu, Ag, Ho, Ta, Au, Pb, Bi, U. The sum of two Maxwellian distributions was fitted to the spectra d2 σ/(d Ωd E) obtainedat several forward andbac kwardangles yielding neutron multiplicities M i andslop e or temperature parameters T i for the low-energy (evaporative, i = 1) andhigh-energy (pre-equilibrium, i = 2) parts, respectively. M 1 increases with A, proportional to the nuclear volume, and M 2 is growing with A 1/3, proportional to the nuclear radius. The T parameters are nearly independent of A. The results are comparedwith previous multiplicity measurements with a 4 π neutron detector, intranuclear cascade calculations and neutron spectra from stoppedan tiproton annihilation on nuclei. With the measuredproton spectra also the ratio of emitted neutrons to protons was determined for Au. [ABSTRACT FROM AUTHOR]