Carl M Chen

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The Neer I (polyethylene glenoid), Neer II (plastic glenoid surface with metal backing), Cofield, and Gristina monospherical total shoulder prostheses were tested for joint subluxation resistance and glenoid component fixation strength. Synthetic glenoid models with consistent structural properties and standard under-cutting geometry were used for glenoid(More)
We have developed a large CdTe pixel detector with dimensions of 23.7 × 13.0 mm and a pixel size of 448 × 448 μm. The detector is based on recent technologies of an uniform CdTe single crystal, a two-dimensional ASIC, and stud bump-bonding to connect pixel electrodes on the CdTe surface to the ASIC. Good spectra are obtained from 1051 pixels out of total(More)
In this paper we present studies of the I-V characteristics of CdZnTe detectors with Pt contacts fabricated from highresistivity single crystals grown by the high-pressure Brigman process. We have analyzed the experimental I-V curves using a model that approximates the CZT detector as a system consisting of a reversed Schottky contact in series with the(More)
| In this paper, we describe charge collection in CdZnTe pixel detectors, with emphasis on events split between multiple pixels (charge-sharing events). We describe the design of the CdZnTe pixel sensors, being developed for the balloon-borne High Energy Focusing Telescope (HEFT), and discuss investigations of charge sharing between pixels. We have(More)
We have developed large format CdZnTe pixel detectors optimized for astrophysical applications. The detectors, designed for the High Energy Focusing Telescope (HEFT) balloon experiment, each consists of an array of 24 44 pixels, on a 498 m pitch. Each of the anode segments on a CdZnTe sensor is bonded to a custom, low-noise application-speci c integrated(More)
Complete hard X-ray optics modules are currently being produced for the High Energy Focusing Telescope (HEFT), a balloon born mission that will observe a wide range of objects including young supernova remnants, active galactic nuclei, and galaxy clusters at energies between 20 and 70 keV. Large collecting areas are achieved by tightly nesting layers of(More)
We studied the effects of bulk and surface conductivity on the performance of high-resistivity CdZnTe (CZT) pixel detectors with Pt contacts. We emphasize the difference in mechanisms of the bulk and surface conductivity as indicated by their different temperature behaviors. In addition, the existence of a thin (10-100 A) oxide layer on the surface of CZT,(More)
Focusing optics are now poised to dramatically improve the sensitivity and angular resolution at energies above 10 keV to levels that were previously unachievable by the past generation of background limited collimated and coded-aperture instruments. Active balloon programs (HEFT), possible Explorer-class satellites (NuSTAR – currently under Phase A study),(More)