H. Sadrozinski

Water-equivalent path length calibration of a prototype proton CT scanner

PURPOSE The authors present a calibration method for a prototype proton computed tomography (pCT) scanner. The accuracy of these measurements depends upon careful calibration of the energy detector used to measure the residual energy of the protons that passed through the object. METHODS A prototype pCT scanner with a cesium iodide (CsI(Tl)) crystal calorimeter was calibrated by measuring the calorimeter response for protons of 200 and 100 MeV initial energies undergoing degradation in polystyrene plates of known thickness and relative stopping power (RSP) with respect to water. Calibration curves for the two proton energies were obtained by fitting a second-degree polynomial to the water-equivalent path length versus calorimeter response data. Using the 100 MeV calibration curve, the RSP values for a variety of tissue-equivalent materials were measured and compared to values obtained from a standard depth-dose range shift measurement using a water-tank. A cylindrical water phantom was scanned with 200 MeV protons and its RSP distribution was reconstructed using the 200 MeV calibration. RESULTS It is shown that this calibration method produces measured RSP values of various tissue-equivalent materials that agree to within 0.5% of values obtained using an established water-tank method. The mean RSP value of the water phantom reconstruction was found to be 0.995 ± 0.006. CONCLUSIONS The method presented provides a simple and reliable procedure for calibration of a pCT scanner.

Temperature effects on radiation damage to silicon detectors

Abstract Motivated by the large particle fluences anticipated for the SSC and LHC, we are performing a systematic study of radiation damage to silicon microstrip detectors. Here we report radiation effects on detectors cooled to 0°C (the proposed operating point for a large SSC silicon tracker) including leakage currents and change in depletion voltage. We also present results on the annealing behavior of the radiation damage. Finally, we report results of charge collection measurements of the damaged detectors made with an 241 Am α source.

Measurement of the Branching Fractions for D0 ---> pi- e+ electron-neutrino and D0 ---> K- e+ electron-neutrino and Determination of (V (c d) / V (c s))**2

Measurements of the exclusive branching fractions B(D^0→π^-e^+ν_e) and B(D^0→K^-e^+ν_e), using data collected at the ψ(3770) with the Mark III detector at the SLAC e^+e^- storage ring SPEAR, are used to determine the ratio of the Kobayashi-Maskawa matrix elements │V_(cd)/V_(cs)│^2 =0.057_(-0.015)^(+0.038)±0.005.

Temperature dependence of radiation damage and its annealing in silicon detectors

Silicon detectors at future collider facilities such as the Superconducting Super Collider (SSC) will be exposed to large fluences of both neutral and charged particles, resulting in considerable bulk radiation damage. In order to reduce the increase in leakage current associated with that damage, the proposed operating temperature of the silicon detectors in the SSC Solenoidal Detector Collaboration (SDC) experiment is 0 degrees C. In order to explore any potential complications of operating detectors at 0 degrees C, two sets of detectors were irradiated. One set was kept close to 0 degrees C during the exposure and annealing period, while the other was maintained at room temperature throughout ( approximately 27 degrees C during the exposure, and approximately 23 degrees C during the annealing period). The full depletion voltage and leakage current of the detectors during the irradiation period and over the subsequent annealing period were monitored. It is concluded that detectors will have to be operated at 0 degrees C, and, once damaged, be maintained at 0 degrees C in order to keep their operating voltage at a reasonable value ( >

Resonant substructure in Kππ decays of charmed D mesons

Abstract Dalitz plot analyses of four Kππ decays of the D 0 and D + mesons are presented. The relative amounts of K ∗ π, Kϱ and non-resonant Kππ in each decay mode are determined, and isospin amplitudes and phases are derived. These results are compared with predictions from QCD. The K − π + π + mode has a non-uniform, non-resonant contribution; attempts to fit this distribution are described.

An amplifier-discriminator chip for the GLAST silicon-strip tracker

An amplifier-discriminator circuit has been designed for reading data from the silicon-strip detectors of the Gamma Large Area Space Telescope (GLAST). For the 38 pF expected detector loading, an equivalent noise charge (ENC) of 1600 electrons has been demonstrated on a 32-channel chip with a power consumption of under 150 /spl mu/W per channel and a 1 /spl mu/S time constant. The typical rms threshold variation was under 750 electrons ENC. These results satisfy the requirements of the GLAST mission.

Beam test of gamma-ray large area space telescope components

A beam test of GLAST (Gamma-ray Large Area Space Telescope) components was performed at the Stanford Linear Accelerator Center in October, 1997. These beam test components were simple versions of the planned flight hardware. Results on the performance of the tracker, calorimeter, and anti-coincidence charged particle veto are presented.A beam test of GLAST (Gamma-ray Large Area Space Telescope) components was performed at the Stanford Linear Accelerator Center in October, 1997. These beam test components were simple versions of the planned flight hardware. Results on the performance of the tracker, calorimeter, and anti-coincidence charged particle veto are presented.

Tests of the radiation hardness of VLSI integrated circuits and silicon strip detectors for the SSC under neutron, proton, and gamma irradiation

As part of a program to develop a silicon strip central tracking detector system for the Superconducting Super Collider (SSC), the effects of radiation damage in silicon detectors and their associated front-end readout electronics are being studied. The authors report on the results of neutron and proton irradiations at the Los Alamos National Laboratory and gamma -ray irradiations at UC Santa Cruz. Individual components on single-sided AC-coupled silicon strip detectors and on test structures were tested. Circuits fabricated in a radiation-hard CMOS process and individual transistors fabricated using dielectric isolation bipolar technology were also studied. Bulk damage to the silicon itself is seen as the limiting factor in the lifetime of a detector system. In particular, it is the acceptor site creation in the active volume of the silicon detector that will limit the lifetime to approximately 10 yr for the innermost detectors. >

Results from the Beam Test of the Engineering Model of the GLAST Large Area Telescope

This paper describes the results of a beam test using the Engineering Model of the GLAST Large Area Telescope, which was installed in a beam of positrons, hadrons and tagged photons at SLAC. The performance of the four subsystems, Anti Coincidence Detector, Silicon Tracker, Calorimeter and Data Acquisition will be described.

The silicon tracker readout electronics of the Gamma-ray Large Area Space Telescope

A unique electronics system has been built and tested for reading signals from the silicon-strip detectors of the Gamma-ray Large Area Space Telescope mission. The system amplifies and processes signals from 884 736 36-cm strips using only 160 W of power, and it achieves close to 100% detection efficiency with noise occupancy sufficiently low to allow it to self trigger. The design of the readout system is described, and results are presented from ground-based testing of the completed detector system.