A compact and finely grained sandwich calorimeter is designed to instrument the very forward region of a detector at a future e + e − collider. The calorimeter will be exposed to low energy e + e − pairs originating from beamstrahlung, resulting in absorbed doses of about one MGy per year. GaAs pad sensors interleaved with tungsten absorber plates are considered as an option for this calorimeter. Several Cr-doped GaAs sensor prototypes were produced and irradiated with 8.5-10 MeV electrons up to a dose of 1.5 MGy. The sensor performance was measured as a function of the absorbed dose.
Results of investigation of X-ray sensors on the basis of GaAs compensated with chromium (HR GaAs) are presented in this work. HR GaAs material is shown to have the following physical parameters: the resistivity about 1GOhm*cm, the nonequilibrium charge carrier lifetime – hundreds of nanoseconds. Prototypes of microstrip and array HR GaAs sensors have been manufactured and tested. It is demonstrated that the sensors provide spatial resolution according to the pixel pitch and allow obtaining high quality X-ray images.
Results obtained from development, construction, testing, and evaluation of GaAs:Cr ionizing radiation detectors and X-ray digital imaging systems based on such detectors are presented. The technology devised is shown to make possible the development of detectors with the following parameters: electron mobility -electron lifetime product of 10 -4 cm 2 /V, hole mobility -hole lifetime product of 10 -6 cm 2 /V, gamma-radiation resistance of ≥ 51Mrad, active layer thickness as great as 800µm, and detector chip dimensions of 51×51mm 2 . The detectors under consideration exhibit high speed of response (≤10ns) and high X-and charged-particle radiation sensitivity. The detector output signal is linearly dependent on the X-ray irradiation dose rate up to 120mR/s and X-ray quantum energy up to 3MeV. Scanning detection units to be used in mammographs and fluorographs and in nondestructive testing devices were constructed and tested. The spatial resolution of the detection systems is 5lp/mm.
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