Abstract
The Focusing Optics X-ray Solar Imager (FOXSI) sounding rockets are the first solar-dedicated direct-focusing hard X-ray (HXR) instruments. FOXSI rockets use Wolter-1 style HXR optics and solid state double-sided strip detectors. FOXSI images of solar HXR sources are influenced by the point spread function of the optics, the 2D segmentation of the detector into strip intersections, and noise in the detector readout. For FOXSI-4, new high-resolution optics will cause the instrument angular resolution to be limited by the minimum strip pitch of its CdTe detectors (60 µm). FOXSI images are also affected by charge sharing in the detector, when one incident photon causes signals in multiple adjacent strips. Charge sharing is more likely the closer a photon is incident to a strip boundary, making it a sub-strip-position-dependent effect. Tests of a FOXSI-3 CdTe detector (with 60 µm strip pitch) at a synchrotron beamline (the Advanced Light Source) have allowed for characterization of charge shared events. This knowledge is used to develop new methods for achieving sub-strip resolution in FOXSI detectors (0.6-3”, depending on incident photon position), applicable in the future to the FOXSI-4 detectors (or other similar systems). To evaluate the performance of these methods, a model has been developed combining the FOXSI-3 optical and detector response, the latter incorporating lab-measured properties of charge sharing in the system. Using this model, generated sources are convolved with the FOXSI-3 system to simulate FOXSI data. A corresponding deconvolution process then extracts a reconstructed source from the simulated data using the new imaging methods, and the original and reconstructed sources can be compared. We show that the reconstructed source approximates the original with higher spatial resolution than that which results from using strip-based position knowledge only. Notably, we demonstrate a new ability to resolve independent sources located only one strip pitch apart.
| Original language | English (US) |
|---|---|
| Title of host publication | X-Ray, Optical, and Infrared Detectors for Astronomy X |
| Editors | Andrew D. Holland, James Beletic |
| Publisher | SPIE |
| ISBN (Electronic) | 9781510653634 |
| DOIs | |
| State | Published - 2022 |
| Externally published | Yes |
| Event | X-Ray, Optical, and Infrared Detectors for Astronomy X 2022 - Montreal, Canada Duration: Jul 17 2022 → Jul 20 2022 |
Publication series
| Name | Proceedings of SPIE - The International Society for Optical Engineering |
|---|---|
| Volume | 12191 |
| ISSN (Print) | 0277-786X |
| ISSN (Electronic) | 1996-756X |
Conference
| Conference | X-Ray, Optical, and Infrared Detectors for Astronomy X 2022 |
|---|---|
| Country/Territory | Canada |
| City | Montreal |
| Period | 7/17/22 → 7/20/22 |
Bibliographical note
Funding Information:This work was supported under the 2019 NASA Fellowship Program (80NSSC19k1687). The FOXSI sounding rocket experiment is funded by NASA grants 80NSSC21K0030, 80NSSC17K0430, NNX08AH42G, NNX11AB75G, and NNX16AL60G. The Univeristy of Minnesota team is supported by an NSF Faculty Development Grant (AGS-1429512), an NSF CAREER award (NSF-AGS-1752268), and the SolFER DRIVE center (80NSSC20K0627). This work was also supported by JSPS KAKENHI Grant Numbers 22J12583, 21H04486, 18H05463, and 24244021. S.N. is also supported by FoPM (WINGS Program) and the JSR Fellowship (University of Tokyo, Japan).
Funding Information:
This research used resources of the Advanced Light Source, which is a DOE Office of Science User Facility under contract no. DE-AC02-05CH11231.
Publisher Copyright:
© 2022 SPIE.
Keywords
- CdTe
- Hard X-rays
- X-ray detectors
- calibration
- charge sharing
- solar flares
- solid-state detectors
- the Sun