D. H. Son

The ZEUS forward plug calorimeter with lead scintillator plates and WLS fiber readout

A Forward Plug Calorimeter (FPC) for the ZEUS detector at HERA has been built as a shashlik lead–scintillator calorimeter with wave length shifter fiber readout. Before installation it was tested and calibrated using the X5 test beam facility of the SPS accelerator at CERN. Electron, muon and pion beams in the momentum range of 10–100 GeV/c were used. Results of these measurements are presented as well as a calibration monitoring system based on a 60Co source.

Signal-to-noise ratio measurement and radiation damage study of silicon PIN diode with a proton beam

We designed and fabricated silicon PIN diodes having p+ active area of 1.0 cm × 1.0 cm on a 5-in. high resistivity (≫5 kΩ⋅cm) n-type FZ (float zone), 380 μm-thick silicon wafer. For signal-to-noise ratio (SNR) measurement of the diode, we required that the fabricated diode should be fully depleted at the operation voltage and the level of the leakage current of the sensor should be less than 10 nA/cm2 at the operation voltage. The SNR of the diode was measured by using a 45 MeV proton beam from the MC-50 cyclotron at Korea Institute of Radiological and Medical Sciences (KIRAMS) in Seoul, Korea. Experiment was performed at room temperature and 46 volts was biased to fully deplete the diode. The SNR of the diode was measured to be 20.8 after corrected for the minimum ionizing particle. The different PIN diode which has relatively large leakage current was used for radiation damage test with the same proton beam. The leakage currents as a function of the reverse bias voltages were measured before and after the proton beam irradiation. The prototype was irradiated with 1.4 ×107 fluence. We annealed the diode after irradiation of the proton beam and measured the leakage current dependence on times at the operation voltage. We present the understanding of radiation-induced detector deterioration and the SNR of the silicon diode in this paper.

Performance test of the silicon PIN diode with radioactive sources

Silicon PIN diodes with an active area of 1 cm × 1 cm were fabricated on a high resistivity, (100)-oriented, n-type, 380-μm thick and 5-inch silicon wafer. These diodes were originally fabricated on purpose to monitor strip sensor fabrication processes. To evaluate the performance of the silicon PIN diode, we measured the signal-to-noise ratio (SNR) and energy resolution using radioactive sources. We measured the radiation detection responses of the silicon PIN diodes and observed photopeaks from radioactive sources, Am-241, Sr-90 and Cs-137. The spectrum by simulation was compared with those of the source tests to understand the measurement results. The tests with Am-241 and Cs-137 sources used random trigger because γ fully deposits its energy in a silicon PIN diode. Another PIN diode was used for trigger purpose with Sr-90, β source. Am-241 test showed a sharp peak of 59.5 keV γ as we expected. The γ peak was used for calibration that converts ADC value into energy. We used Cs-137 source to compare a resolution at the lower energy level (32 keV γ) with 59.5 keV γ. Two different conditions were set for Cs-137; without a lead-block and with 3mm-lead-block to reduce β background. In the test of Sr-90, the SNR of the silicon PIN diode was measured to be 36.0. We present the energy resolution and the SNR of the diode measured by using the radioactive sources.

Prototype development of silicon array sensor for x-ray detector

A prototype of silicon array sensor with 256 pixels and a frontend electronics system for its readout was developed for X-ray imaging. The characteristics of the sensor and some test results of the electronics system are presented.