ON THE OPTIMAL CHARACTERISTICS OF THE MULTICHANNEL IMAGING CAMERA FORTEV GAMMA-RAY OBSERVATIONS

The detection efficiency of atmospheric Cerenkov flashes as a function of the camera parameters was studied in order to determine the optima l camera parameters for the discovery of VHE gamma ray point sources. Simulations of the detection process and calculation of the flash para meters are used. It is shown that the optimal value of the camera angu lar diameter is in the range 3-degrees-.1-3-degrees-.7 and the optimal pixel size is from 0-degree-.2 to 0-degree-.3. In these cases the num ber of photomultipliers ranges from 61 to 127 for a camera with a hexa gonal window. The computations are made for the case when any two chan nels generate a logical signal, i.e. at least two pulses are higher th an the threshold. Note that the photocathode current fluctuation cause d by the night sky radiation is very important for the calculations be cause it is the major factor which determines the lower limit for the pixel size. Calculations neglecting fluctuations caused by the night s ky lead to an incorrect conclusion: the smaller the pixel size, the be tter are the images, i.e. they are close to real ones (unlimited resol ution camera).