Design and performance of a compact field cage for the HERD side-on transition radiation detector

Abstract The ability of the side-on transition radiation detector (TRD) for High Energy Radiation Detector (HERD) to accurately calibrate energy of cosmic ray depends on the precision in measuring and identifying Transition Radiation (TR) photons. This requires maximizing the transmittance of TR photons to the sensitive volume and the collection of resulting electrons by the detector. An optimization of the field cage is necessary for both aspects. In response to the need for high TR photon transmittance from the side and a uniform electric field in a compact structure for the TRD, a dual-width strip structure field cage solution has been developed. This field cage has a TR photon transmittance of over 95%, 3D modeling based on the actual detector and Monte Carlo simulations indicate that the electron collection efficiency in the field cage can reach 97.2%. The test results for the energy response differences at various incident positions within the sensitive volume of the detector indicate that the normalized gain range is between 0.9 and 1.1, demonstrating good consistency.