X Ray Polarization Measurement And Cosmic Rays Tracer Based On THGEM Gas Detector

Micro Pattern Gas Detector(MPGD)has the advantages of high counting rate,extremely fast time response,sub-millimeter spatial resolution,easy to be manufactured with large area,robustness and low cost.Therefore,there are many in-depth research of MPGD and it has also been widely used.X-ray polarization can provide much important information,such as the geometry structure of high-energy objects,the strength of the surrounding magnetic field and the radiation mechanism.It is an important means for understanding astrophysics.The measurement of X-ray polarization based on the photoelectric effect requires a highly sensitive detector,which can get a longer/thinner photoelectron track and finely reconstruct the photoelectron track.These are requirements for detectors.MPGD can adapt to these requirements and is a good choice for photoelectric polarization detectors.For these reasons,the optical readout was firstly investigated by using an ICCD camera based on the MicroMegas gas detector.X-ray and alpha particles were imaged two-dimensionally and both of alpha particles and photoelectron tracks were obtained.Then the electrons were collected and read by using a Topmetal chip based on THGEM gas detector.The obvious photoelectron tracks were obtained at different gas pressure and gain,especially under the conditions of the pressure of 80 kPa and a gain higher than 4×103,which basically meets the requirements for reconstructing the exit direction of the photoelectrons.A high-energy cosmic radiation detection device(HERD),the Chinese Space Station plans to deploy,will explore the dark matter particles and finely observe the original cosmic rays of the high energy region in the space.The calorimeter,composed of LYSO cubic crystals,is a HERD core detector.Cosmic rays tracer based on THGEM gas detector discussed in this paper,was performed the calibration of LYSO crystals.The effective area of the THGEM gas detector is 20×30 cm2 and the gain of the double-layer THGEM is close to 1×104,which was readout by a 200+134 two-dimensional strip and the position of the 55Fe source is reconstructed.In addition,in respect of the production process,the hydrogen peroxide system was used to whole-plate chemical polishing corrosion for the THGEM film,which achieved to develop a variety of THGEM films.