Showing papers by "Wen-Chang Chen published in 1996"

Development of large linear silicon drift detectors for the STAR experiment at RHIC

Abstract: Large area linear Silicon Drift Detectors (SDD) are being developed for high energy and relativistic heavy ion collider experiments. SDDs have been proposed for the inner tracking detector in the STAR experiment at the BNL relativistic heavy ion collider to become operational in 1999. The Silicon Vertex Tracker (SVT) will consist of a three layer barrel structure composed of 216 individual detectors, each 6.3 × 6.3 cm 2 . Prototypes, including one-way drift detectors (4.5 × 4.5 cm 2 ) and bi-directional drift detectors (6 × 6 cm 2 ) have been manufactured,and their properties have been studied. Design considerations, as well as test results, are presented in this article. Recent work has focused on minimizing the inactive guard structure area in order to optimize tracking efficiency. Particular attention is given to discussion of parameters that are sensitive to the reduced guard structure area, such as leakage current, maximum voltage and drift non-linearities.

Preparation of gradient-index (GRIN) polymer fibers for imaging applications

Abstract: A closed extrusion process combined with a core-shell separation die design is developed in this study for preparing gradient index (GRIN) polymer fibers with a quadratic distribution of the refractive index. The material system used in this investigation is methyl methacrylate (MMA, n = 1.49) and benzyl methacrylate (BzMA, n = 1.568). The refractive index differences between the center and the periphery (Δn) of the prepared polymer fibers increase from 0.0115 to 0.020 when BzMA in the reactant mixtures increases from 17 to 28%. This finding would suggest that increasing the high refractive index monomer in the reactant mixture increased Δn. The Δn values decrease from 0.018 to 0.0135 when the diffusion zone temperature increases from 70 to 90°C. The diffusion rates of the monomers increase with the temperature, thereby causing BzMA and MMA to distribute more uniformly at a higher temperature than at a lower one. This uniform distribution leads to the decrease of Δn with an increasing temperature. The prepared GRIN polymer fibers have potential applications as imaging lenses for scanners, fax machines, and copiers. © 1996 John Wiley & Sons, Inc.

Transport properties of electrons in silicon drift detectors measured in large magnetic fields

Abstract: A 45 × 45 mm rectangular n-type Silicon Drift Detector was studied in magnetic fields ranging from 0 to 4.7 T and for drift fields from 200 to 380 V/cm. Transport properties of electrons in silicon (Hall mobility, drift mobility and magnetoresistance) were determined by pulsing the detector with a Nd:YAG laser at different drift lengths and measuring both the transverse deflections of the signal and the increases in drift time versus an applied magnetic field. The width of the signal in both the drift and anode direction increased with magnetic field. The magnetic field was aligned parallel and normal to the drift direction. The detector was found to operate well for conditions expected in future experiments at the RHIC collider and experiment E896 at Brookhaven National Laboratory.

Experimental study of ship pitching motion reduction using anti-pitching fins

Abstract: In this paper, we investigate the usefulness of active stabilizing fins on ship pitching reduction under varying forward speeds, in varying wave lengths. A 4-meter self-propelled ship model and an electrohydraulically driven stabilizing fin system are used as our experimental system. Pitch angles, pitch rates, and ship forward speeds are measured and feedback to a fuzzy logic controller to calculate the deflection angle of the stabilizing fins. The effects of fin nonlinearity on achievable pitch reduction performance are discussed. It is shown that desired pitch response can only be achieved when the fin is operated in its linear region. The overall dynamic response of the ship approaches her open loop behavior when the degree of nonlinearity is high. This simple analysis to the pitch stablizing system provides basic information to ship designers. Experimental results validate this design guideline.

Synthesis and characterization of polymer light conduits

Abstract: Large diameter polymer light conduits are prepared for the first time by UV-curing. The polymer cores of the polymer light conduits are prepared from the copolymerization of various monomer mixtures in FEP tubes by UV curing, where FEP is used as the polymer cladding. The monomer mixtures consist of a multifunctional monomer for adjusting the heat resistance of the polymer cores and a monofunctional monomer for adjusting the flexibility. Experimental results indicate that the properties of the prepared polymer light conduits can be significantly modified by the formulations of the reactant mixtures. The onset thermal decomposition temperatures of the prepared polymer cores are 50°C to 79°C higher than that of the PMMA core. The glass transition temperatures and the refractive indices of the prepared polymer cores decrease from 78°C to -34°C and 1.490 to 1.474, respectively, when the contents of 2-ethyl-hexyl acrylate in the monomer mixtures increase from 0% to 70%. The prepared polymer light conduits conduits have large numerical apertures suitable for wide angle illumination applications.

Double particle resolution in STAR silicon drift detectors

Abstract: The inner tracking detector of the STAR experiment at the BNL Relativistic Heavy Ion Collider will consist of a three layer barrel structure of 216 silicon drift detectors. Calculations of the two-hit resolution achievable for these detectors are presented in this article. The effects on two-hit resolution of the electronic's response function, frequency of signal digitization and noise level are discussed.

Investigation of the properties of a radial silicon drift detector in the WA93-experiment

Abstract: A radial 3-inch silicon drift detector (SiDD), designed by Rehak, was used in the WA93 experiment to measure the production of charged particles and to determine detector characteristics for future applications with even higher multiplicities. Beside correlations with other detectors of the WA93 experiment, a Monte Carlo model and the results of a dedicated experiment with a test beam were used to interpret the S + Au 200 A GeV data. This paper describes the experimental setup and the methods used to extract the properties of the radial SiDD.