X-ray imaging polarimetry with a 2.5-μm pixel CMOS sensor for visible light at room temperature

Abstract

X-ray polarimetry in astronomy has not been exploited well, despite its importance. The recent innovation of instruments is changing this situation. We focus on a complementary MOS (CMOS) pixel detector with small pixel size and employ it as an x-ray photoelectron tracking polarimeter. The CMOS detector we employ is developed by GPixel Inc., and has a pixel size of 2.5 µm × 2.5 µm. Although it is designed for visible light, we succeed in detecting x-ray photons with an energy resolution of 176 eV (FWHM) at 5.9 keV at room temperature and the atmospheric condition. We measure the x-ray detection efficiency and polarimetry sensitivity by irradiating polarized monochromatic x-rays at BL20B2 in SPring-8, the synchrotron radiation facility in Japan. We obtain modulation factors of 7.63% ± 0.07% and 15.5% ± 0.4% at 12.4 keV and 24.8 keV, respectively. It demonstrates that this sensor can be used as an x-ray imaging spectrometer and polarimeter with the highest spatial resolution ever tested.

Artifact-less Coded Aperture Imaging in the X-ray Band with Multiple Different Random Patterns

“…Therefore, we are able to gain the effective area and to reduce artifacts simultaneously by using our method. Combining this imaging capability with the polarization detectability of the CMOS imager, 22 our system can be used for the imaging polarimetry in hard X-rays.…”

“…As a detector, we used a 25M pixel CMOS imager with a pixel pitch of 2.5 µm. This imager has an ability of X-ray detection below 24 keV and has an energy resolution of 176 eV (Full Width at Half Maximum; FWHM) at 5.9 keV at a room temperature of 25 • C. 22 We set a frame time exposure of 90 ms to reduce detector backgrounds B (k,l) and pedestals in a frame. The pedestals are estimated from the latest set of dark images with the X-ray beam off.…”

On the Response of a Micro Non-Destructive Testing X-ray Detector

“…The need for the (detrimental for the image quality) demagnification is eliminated and a direct coupling of the scintillator material is thus permitted. Regarding the attainable resolution, sub – 2 μm pixel sizes have been reported [ 22 , 23 ].…”

Performance of a focal plane detector for soft X-ray imaging spectroscopy based on back-illuminated sCMOS

“…However, the tailing effect in CCD is obvious due to the charge transfer process when there is no shutter in front of the sensor [6]. Besides, the advantages of relatively simple peripheral circuit design have made CMOS gradually applied to many fields [7][8], including X-ray imaging polarimetry [9] or even as a focal plane detector for some micro or small X/γ-ray scientific mission [10] [11]. Therefore, the CMOS sensor is selected as the X-ray focal plane detector to test the X-ray mirror module.…”

“…the minimum reconstructed photon energy of the single-pixel event, 2-pixel split event, 3-pixel split event, and 4-pixel split event are T event , 2 ×T event , 3×T event , and 4×T event , respectively). The proportions of the different event split patterns show significant differences in each other, which maybe representing the polarization properties of incident X-ray photons according to the research by Kazunori Asakura et al 2019[9].…”