Yu.M. Dikaev1, A.A. Kudryashov2

1,2 Kotelnikov Institute of Radioengineering and Electronics of RAS (Fryazino, Russia)

1 ymd289@yandex.ru, 2 aka217@ire216.msk.su

The paper considers the features of the occurrence of photocurrent in semiconductor epitaxial GaAs-structures in the mode of detecting sliding X-ray irradiation. In order to expand the range of effective energy for the registration of X-ray radiation, experimental measurements of the photocurrent of the GaAs detector were carried out at different orientations of it in relation to the direction of radiation. The dependences of the detector's photocurrent on the effective energy of the X-ray radiation have maximum values that shift to a more "hard" region of effective energies with a decrease in the sliding angle. By tilting the detector, a shift in the maximum photocurrent of the detector is achieved from an effective radiation energy of 30 keV with normal irradiation up to 60 keV, at a radiation slip angle of 50 and into the end. Based on the results of the study of GaAs structures, an arc-curved multi-element ruler of separate modules - detector assemblies - was developed. The radius of arc curvature is equal to the distance from the X-ray source to the surface of the detector, while each module is located at a sliding angle of 50 to the direction of propagation of X-ray radiation with a collimator in front of the detector line, a gap width of 1 mm. A multi-module line for 1024 channels, consisting of 16 modules, was developed. One module in such a line with GaAs structure dimensions 32 mm wide and 5 mm long consists of 64 channels. Each channel of the detector is scribbled in dimensions of 0.5 by 5 mm and is located at a sliding angle of α = 50 to the direction of propagation of X-ray radiation. In front of the detector line, a collimator with a slit width of 1 mm is installed to form a narrow beam of X-ray radiation. The multi-module detector is made in the form of an arc with a radius of curvature R = 1.5 m, equal to the distance from the X-ray source to the surface of the detector. Such a line of detectors with an X-ray source is synchronously scanned along the object under study. A brake X-ray source with a W-anode at a tube voltage of 100 kV was used.  The effective radiation energy of 60 keV is obtained by passing through a copper filter with a thickness of 0.8 mm. Radiation at such energies at a length of 5 mm at the end of the GaAs crystal is absorbed by 99.5%, that is, it corresponds to the most efficient conversion of the energy of the absorbed photons into a photocurrent. The photocurrent from each detector that occurs during the absorption of X-rays enters a low-noise operational amplifier, then the amplified analog signal is transmitted using the K switch for digitization. After processing by a computer, X-ray digital images of an object with a large dynamic range in terms of radiation energies are obtained, similar to those obtained earlier in the "soft" radiation registration mode with a lower dynamic range. The proposed multi-element detector can be used in medical diagnostics.

Dikaev Yu.M., Kudryashov A.A. X-ray detector based on epitaxial GaAs structures in sliding irradiation mode. Biomedicine Radio-engineering. 2024. V. 27. № 1. Р. 14-19. DOI: https://doi.org/10.18127/j15604136-202401-02 (In Russian)

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