Radiation hardness tests of GaAs amplifiers for liquid argon calorimetry

The high luminosity at LHC requires a high radiation resistance for the detectors, especially for those parts of calorimeters which cover the maximum of the electromagnetic shower. The total neutron flux expected after 10 years of LHC running is up to about 10"1"5n/cm"2 and the #gamma#-dose about (10/20) Mrad. These radiation levels are estimated for the region of #eta#=3, but vary with different detector positions and decrease by one or two orders of magnitude in the region of the end-cap hadronic calorimeter. The electronics which is installed inside the detector should withstand these radiation levels. The GaAs technology is one candidate for radiationhard electronics. In the context of the RD33 experiment, preamplifiers, summation and shaping electronics were designed in GaAs technology to be used for an electromagnetic liquid argon calorimeter. The working point of the electronics is optimised for a temperature of -187 C. The GaAs technology is based on n-channel transistors. The preamplifier is a current sensitive amplifier which means that the feedback capacity was chosen to be low. The amplification factor is described by the transfer function which is the ratio between the output voltage at the terminating resistor and the input current. The linearity and the noise are the main characteristics which were measured at different dose levels and fluences in the present study. The radiation hardness tests of GaAs electronics were performed in the Joint Institute for Nuclear Research, Dubna. (orig.)SIGLEAvailable from TIB Hannover: RR 2916(95-08) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Radiation hardness of GaAs preamplifiers for liquid argon calorimetry at LHC

Cold preamplifiers, designed in GaAs technology, are foreseen in the readout chain of the hadronic liquid argon end-cap calorimeter of the ATLAS experiment at LHC. The preamplifiers immersed in the liquid argon must withstand the hostile radiation environment during the operation of the LHC machine at the highest luminosities for the whole expected lifetime of the experiment. Preamplifiers, with a layout similar to the ones proposed, have been exposed to a high fluence of fast neutrons and to a high dose of #gamma# radiation. No significant deterioration of the performance has been observed for a neutron fluence up to #approx# 3.10"1"4 n cm"-"2 and up to 31 kGy, the highest #gamma# dose collected. Also only a moderate increase of the equivalent noise current has been seen for the radiation levels relevant for the operation in the ATLAS experiment. (orig.)SIGLEAvailable from FIZ Karlsruhe / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman