P73

Presentation Title:	Wide-gap CdTe Double-Sided Strip Detectors for High-Resolution Imaging Spectroscopy of Solar Flares in Hard X-rays for FOXSI-4
Author(s):	Shunsaku Nagasawa, Takahiro Minami, Shin Watanabe, Tadayuki Takahashi, Yixian Zhang, Kristopher Cooper, Athanasios Pantazides, Lindsay Glesener and FOXSI-4 team

Abstract:

We develop a new configuration CdTe double-sided strip detector as “Wide-gap CdTe-DSD,” in which a gap between strips is much wider than strips, as focal plane detectors in hard X-ray band (4-20 keV) for direct-focusing imaging spectroscopy observation of solar flares for FOXSI-4. The detector has 128 strip electrodes on both cathode and anode sides varied from 60 μm strip pitch (30 μm strip and 30 μm gap width) to 100 μm strip pitch (30 μm strip and 70 μm gap width). By widening the gap between the strips, the percentage of charge sharing events between adjacent strips is enhanced, and a sub-strip position resolution could be achieved by utilizing the information on the sharing energies.
To confirm this concept, we conducted an evaluation test by uniformly irradiated X-rays using 241Am.
By developing a new energy reconstruction method to compensate for the charge loss of wider gaps and the depth of interaction effects, an energy resolution of 0.9 keV is obtained using all single and double strip events. We also conducted fine beam scanning experiments at SPring-8 to study the spatial dependence of the response. The beam size is collimated to 10 μm squared, and the beam energy is changed from 7 to 35 keV. From these experiments, the sub-strip position resolution has been demonstrated, especially for the anode side, with a precision of 10 μm in the gap region. Finally, we constructed an onboard data processing network using a standard communication interface of SpaceWire and new FPGA board SPMU-001.
We succeeded in developing the CdTe-DSD Data Encoder software to control and acquire data from four CdTe-DSDs simultaneously, which can withstand the high count rate and large data volume of solar flares observed by FOXSI-4.

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