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The CMOS Avalanche Photodiodes (APDs) and Charge Sensitive Preamplifiers (CSAs) were fabricated using the commercially available AMIS 0.7 mum high voltage process without any process modifications. The APDs have an N+/P-substrate structure with the diameters of their active areas equal to 25 mum, 50 mum, 100 mum, 400 mum, and 800 mum. The CSAs with three different input transistor sizes were configured with a folded cascode structure, and the ratio of the input transistor size is 1:2:4. The avalanche multiplication in APDs occurred at 10.9 V reverse bias, and gains between 9 and 40 with respect to the size of CMOS APDs were measured. In zero bias condition, the quantum efficiency peaks at 650 nm wavelength with a value of ~30%. As a result of the noise measurement for the CSAs, the CSAs with largest input transistor shows the best noise characteristics for various detector capacitances, while the CSAs with smallest size of input transistor shows the worst noise characteristics.

We evaluated X-ray image performance for several scintillators and a CMOS APS imager by both diagnostic radiography and mammography conditions. Commercially available scintillators such as Lanex screen, needle structured CsI (Tl), and fiber optic structured CsI (Tl) were coupled with a CMOS APS imager. The X-ray machines used in this study were fixed tube voltage of 80 kVp and variable tube current over 0.33 mA using LISTEMtrade for diagnostic radiography, and fixed tube voltage of 28 kVp and variable tube current over 16 mA using Alpha-STtrade for mammography. We used the RadEye1trade CMOS APS imager having an active area of 25 mm by 50 mm with the pixel size of 48 m.

Flat panel detectors using amorphous silicon p-i-n diodes have been developed for chest and portal imaging. In radiation therapy, an imaging device is exposed to a high radiation dose. So the radiation damage affects the leakage current of diode and may decrease the whole system performance. In this research we have investigated the radiation damage to the leakage current of a-Si:H diode made by PECVD and ion-shower doping methods, and studied the effect of a copper plate used in portal imaging. Leakage current as a function of absorbed dose shows that the damage effects seem to be same for two types of diodes when a copper plate is used. They have the threshold value below which leakage current does not change. Both of two diodes show different threshold behavior when a copper plated is not used. Threshold value shifts to a higher dose in the absence of a copper plate. In addition an ion-shower diode shows a higher leakage current at high absorbed dose compared to a PECVD diode. Since the p-n junction property of an ion-shower diode is not as good as a PECVD diode, the leakage current increase induced by radiation can be higher at high absorbed dose. Monte Carlo simulation tells that the copper plate used in portal imaging generates more secondary electrons, which transfer energy to the diode as they travel through.

To permit the pulsed field of a bump magnet to penetrate the vacuum chamber of a particle storage ring, a section of ceramic chamber is used. A thin metal coating on the inner surface is usually employed to prevent the static charge build-up on the surface of the ceramic chamber, as well as to reduce the coupling impedance. The metal coating, however, can lead to heating of the chamber walls due to eddy current. To avoid such an unwanted effect, a patterned coating is employed. In this paper, we discuss the electrical power and the field distortion due to the eddy current and the effect of various patterned metallic coatings on the motion of a circulating beam. The results are applied to the storage ring of the Pohang Light Source.