A. Karar

Characterization of avalanche photodiodes for calorimetry applications

Silicon avalanche photodiodes (APDs) have been studied extensively as photosensor candidates for the electromagnetic calorimeter of the CMS detector at LHC. This work presents the measurements of APDs from Hamamatsu and EG&G, with particular emphasis on multiplication factor, spectral response, excess noise factor as well as their dependence on wavelength. The results are compared to the theoretical predictions. Results on the stability of APD gain to bias and temperature drift are also presented. ( 1999 Elsevier Science B.V. All rights reserved.

Energy and spatial resolution of a Shashlik calorimeter and a silicon preshower detector

New projective prototypes of a scintillator/lead sandwich type sampling calorimeter Shashlik with a silicon preshower detector have been constructed and tested with an electron beam at CERN-SPS. The energy resolution is measured to be 8.7%E(GeV) in stochastic term, 0.330/E(GeV) in noise term and 0.5% in constant term. The angular resolution is better than 70 mradE(GeV).

APD'S EXCESS NOISE MEASUREMENTS USING SPECTRAL ANALYSIS (FFT)

Abstract In high energy physics, the measurement of APDs excess noise factor is essentially made by histogram method. Another method used mainly in telecommunication field is to measure the noise spectral density using a transresistance amplifier from which the output signal is analysed by FFT (Fast Fourier Transform). The main advantage of this spectral method is the capability to separate the different domain of the whole noise spectrum. In addition, it is easy to use and is more sensitive at low bias voltage. This method also allows one to detect the generation and recombination noises if they exist. For certain type of APDs, this method gives an opportunity to measure the primary photocurrent. We have measured the excess noise of two types of APDs with this spectral method as well as histogram method. The result by the spectral method coincides well with the histogram method.

Reduction of ECAL data volume using lossless data compression techniques

Abstract We investigate the possibility of reducing the data size of the electromagnetic calorimeter (ECAL) of CMS detector at the Large Hadron Collider. The Selective Readout is applied to reduce the data size at a manageable level. Then various data compression methods are considered, and their performances estimated using the data from the full simulation of the ECAL system. A reduction of the average event size by a factor of two or larger is obtained in most cases.

Beam test results of a Shashlik calorimeter in a high magnetic field

Abstract Shashlik calorimeter prototypes equipped with preshower detector have been tested in 3 T magnetic field with electron beam at CERN-SPS. The signal from electrons increases as much as 11% at 3 T magnetic field. No significant deterioration on the energy resolution as well as the preshower detector performance have been observed.