R. Bose

The first GCT camera for the cherenkov telescope array

The Gamma Cherenkov Telescope (GCT) is proposed to be part of the Small Size Telescope (SST) array of the Cherenkov Telescope Array (CTA). The GCT dual-mirror optical design allows the use of a compact camera of diameter roughly 0.4 m. The curved focal plane is equipped with 2048 pixels of ~0.2{\deg} angular size, resulting in a field of view of ~9{\deg}. The GCT camera is designed to record the flashes of Cherenkov light from electromagnetic cascades, which last only a few tens of nanoseconds. Modules based on custom ASICs provide the required fast electronics, facilitating sampling and digitisation as well as first level of triggering. The first GCT camera prototype is currently being commissioned in the UK. On-telescope tests are planned later this year. Here we give a detailed description of the camera prototype and present recent progress with testing and commissioning.

Test of CZT Detectors with Different Pixel Pitches and Thicknesses

The modified horizontal Bridgman (MHB) process produces cadmium zinc telluride (CZT) crystals with high yield and excellent homogeneity. Various groups, including our own, previously reported on the test of 2times2times0.5 cm3 MHB CZT detectors grown by the company Orbotech and read out with 8times8 pixels. In this contribution, we describe the optimization of the photolithographic process used for contacting the CZT detector with pixel contacts. The optimized process gives a high yield of good pixels down to pixel diameters/pitches of 50 microns. Furthermore, we discuss the performance of 0.5 cm and 0.75 cm thick detectors contacted with 64 and 225 pixel read out with the RENA-3 ASICs from the company NOVA R&D.

Abundances of Ultra-Heavy Galactic Cosmic Rays from the SuperTIGER Instrument

R. P. Murphy∗1, W. R. Binns1, R. G. Bose1, T. J. Brandt2, P. F. Dowkontt1, T. Hams 2,6, M. H. Israel1, A. W. Labrador3, J. T. Link2,6, R. A. Mewaldt3, J. W. Mitchell2, B. F. Rauch1, K. Sakai2,6, M. Sasaki2,6, E. C. Stone3, C. J. Waddington4, J. E. Ward1,‡, and M. E. Wiedenbeck5† 1 Washington University in St. Louis, St. Louis MO 63130 USA 2 NASA Goddard Space Flight Center, Greenbelt, MD 20771 USA 3 California Institute of Technology, Pasadena, CA 91125 USA 4 University of Minnesota, Minneapolis, MN 55455 USA 5 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 USA 6 Center for Research and Exploration in Space Science and Technology (CRESST) ‡ Now at Institut de Fisica d’Altes Energies (IFAE), Bellaterra, Spain

Leakage currents and capacitances of thick CZT detectors

The quality of cadmium zinc telluride (CZT) detectors is steadily improving. For state of the art detectors, readout noise is thus becoming an increasingly important factor for the overall energy resolution. In this contribution, we present measurements and calculations of the dark currents and capacitances of 0.5 cm thick CZT detectors contacted with a monolithic cathode and 8times8 anode pixels on a surface of 2times2 cm2. Using the NCI ASIC from Brookhaven National lab as an example, we estimate the readout noise caused by the dark currents and capacitances. Furthermore, we discuss possible additional readout noise caused by pixel-pixel and pixel-cathode noise cross- coupling.

Test of CZT detectors with different pixel pitches and thicknesses

The modified horizontal Bridgman (MHB) process produces cadmium zinc telluride (CZT) crystals with high yield and excellent homogeneity. Various groups, including our own, previously reported on the test of 2times2times0.5 cm3 MHB CZT detectors grown by the company Orbotech and read out with 8times8 pixels. In this contribution, we describe the optimization of the photolithographic process used for contacting the CZT detector with pixel contacts. The optimized process gives a high yield of good pixels down to pixel diameters/pitches of 50 microns. Furthermore, we discuss the performance of 0.5 cm and 0.75 cm thick detectors contacted with 64 and 225 pixel read out with the RENA-3 ASICs from the company NOVA R&D.