Review of particle physics Hagiwara, K; Nakamura, K; Amsler, C ...
Physical review. D, Particles and fields,
07/2002, Letnik:
66, Številka:
1
Journal Article
Recenzirano
This biennial Review summarizes much of Particle Physics Using data from previous editions, plus 2205 new measurements from 667 papers, we list, evaluate, and average measured properties of gauge ...bosons, leptons, quarks, mesons, and baryons We also summarize searches for hypothetical particles such as Higgs bosons, heavy neutrinos, and supersymmetric particles All the particle properties and search limits are listed in Summary Tables We also give numerous tables, figures, formulae, and reviews of topics such as the Standard Model, particle detectors, probability, and statistics This edition features expanded coverage of CP violation in B mesons and of neutrino oscillations For the first time we cover searches for evidence of extra dimensions (both in the particle listings and in a new review) Another new review is on Grand Unified Theories A booklet is available containing the Summary Tables and abbreviated versions of some of the other sections of this full Review All tables, listings, and reviews (and errata) are also available on the Particle Data Group website http //pdg 1b1 gov.
Anesthesia is currently required for positron emission tomography (PET) studies of the animal brain in order to eliminate motion artifacts. However, anesthesia profoundly affects the neurological ...state of the animal, complicating the interpretation of PET data. Furthermore, it precludes the use of PET to study the brain during normal behavior. The rat conscious animal PET tomograph (RatCAP) is designed to eliminate the need for anesthesia in rat brain studies. It is a miniaturized full-ring PET scanner that is attached directly to the head, imaging nearly the entire brain. RatCAP utilizes arrays of 2 mm /spl times/ 2 mm LSO crystals coupled to matching avalanche photodiode arrays, which are in turn read out by full custom integrated circuits. Principal challenges have been addressed considering the physical constraints on size, weight, and heat generation in addition to the usual requirements of small-animal PET, such as high spatial resolution in the presence of parallax error. A partial prototype has been constructed and preliminary measurements and optimization completed. Realistic Monte Carlo simulations have also been carried out to optimize system performance, which is predicted to be competitive with existing microPET systems.
The RatCAP has been designed and constructed to image the awake rat brain. In order to maximize system performance, offline digital coincidence data processing algorithms including offset delay ...correction and prompt and delayed coincidence detection have been developed and validated. With offset delay correction using a singular value decomposition (SVD) technique, overall time resolution was improved from 32.6 to 17.6 ns FWHM. The experimental results confirm that the ratio of prompts to randoms was improved because a narrower timing window could be used. 18 F-fluoride rat bone scan data were reconstructed using our fully 3-D ML-EM algorithm with a highly accurate detector response model created from Monte Carlo simulation.
A study on the properties of lead tungstate crystals Zhu, R.Y.; Ma, D.A.; Newman, H.B. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
07/1996, Letnik:
376, Številka:
3
Journal Article
Recenzirano
Odprti dostop
This report summarizes the results of a study on the properties of five large and five small size lead tungstate (PbWO
4) crystals. Data are presented on the longitudinal optical transmittance and ...light attenuation length, light yield and response uniformity, emission spectra and decay time. The radiation resistance of large crystals and possible curing with optical bleaching are discussed. The result of an in depth materials study, including trace impurities analysis, are also presented. The general conclusion from this investigation is that further research and development is needed to develop fast, radiation-hard PbWO
4 crystals for the CMS experiment at the CERN LHC.
The gas electron multiplier (GEM) may provide a convenient method for obtaining significant electron multiplication over large detector areas. An important potential application of the GEM is in ...microTPCs. We are conducting a study of a multi-GEM structure with particular emphasis on the following characteristics: gain uniformity/stability, ion feedback, and position readout. In particular, we present the first experimental results of interpolating anode pad readout. Initial results provide encouragement that the GEM application in microTPCs may be realized.
One of the most promising high resolution positron emission tomography detector designs comprises an array of small, optically isolated scintillator crystals each coupled to an independent ...photosensor, such as an avalanche photodiode (APD). However, crosstalk between crystals (due to Compton scatter, photoelectron escape, or incomplete optical isolation) can significantly degrade performance and is expected to increase as crystals become narrower to improve spatial resolution. Various measures of crosstalk have been determined for different configurations of 4 /spl times/ 8 blocks of 2 mm /spl times/ 2 mm lutetium oxyorthosilicate (LSO) crystals coupled to matched Hamamatsu APD arrays. Results indicate that ignoring crosstalk signals could lead to a /spl sim/ 30% loss in coincidence sensitivity for a tomograph using these detectors and a decrease in energy resolution of /spl sim/ 2 percentage points. Spatial and time resolution would not be significantly affected with most practical front-end architectures.
The capability to create high quality images from data acquired by the Rat Conscious Animal PET tomograph (RatCAP) has been evaluated using modified versions of the PET Monte Carlo code Simulation ...System for Emission Tomography (SimSET). The proposed tomograph consists of lutetium oxyorthosilicate (LSO) crystals arranged in 12 4 /spl times/ 8 blocks. The effects of the RatCAPs small ring diameter (/spl sim/40 mm) and its block detector geometry on image quality for small animal studies have been investigated. Since the field of view will be almost as large as the ring diameter, radial elongation artifacts due to parallax error are expected to degrade the spatial resolution and thus the image quality at the edge of the field of view. In addition to Monte Carlo simulations, some preliminary results of experimentally acquired images in both two-dimensional (2-D) and 3-D modes are presented.
This report presents recent progress of a study on the radiation damage in lead tungstate (PbWO/sub 4/) crystals. The dose rate dependence of radiation damage in PbWO/sub 4/ has been observed. An ...optimization of the oxygen compensation through post-growth thermal annealing has led to PbWO/sub 4/ samples with significantly improved radiation hardness. Front irradiation is found to cause a factor of 2 to 6 times less severe damage than uniform irradiation. Lanthanum doping was found not to be a determining factor for PbWO/sub 4/ radiation hardness improvement. Finally, a TEM/EDS analysis revealed that the radiation damage in PbWO/sub 4/ crystals is caused by oxygen vacancies.
A study of scintillation beta microprobes Woody, C.L.; Stoll, S.P.; Schlyer, D.J. ...
IEEE transactions on nuclear science,
10/2002, Letnik:
49, Številka:
5
Journal Article
Recenzirano
Several types of scintillation microprobes have recently been developed to directly measure positron activity from radiotracers in live animals. These probes consist of either a small lutetium ...oxyorthosilicate (LSO) crystal or plastic scintillator coupled to an optical fiber that is read out with a photomultiplier tube operated in a single photon counting mode. In this paper, a comparison is made between the two types of probes in terms of their sensitivity to both positrons and gammas. It was found that LSO offers very high sensitivity to positrons due to its high density and light output, and allows the construction of very small probes for certain applications. The LSO probe can also provide effective discrimination between positrons and gammas, and provide better localization of positron decays, using pulse height discrimination. Results are also given on the use of the microprobe on live laboratory animals.
A study has been carried out to investigate the possibility of using a pair of LSO + APD detector arrays to obtain a noninvasive measurement of the arterial input function for use in PET. The main ...focus of this study was to determine the spatial resolution and sensitivity required to obtain a high quality image that would permit a precise determination of the region of interest around the wrist artery. From these data a quantitative arterial input function that has minimal interference from the tissue and vein background can be obtained. The detector arrays were operated in coincidence counting mode to obtain planar images of various phantoms to demonstrate the feasibility of the concept.
PDF