Photon-Counting Soft X-ray Telescope for the Solar-C Mission

1. Photon-Counting Soft X-ray Telescope for the Solar-C Mission Taro Sakao (ISAS/JAXA) and N. Narukage1, M. Shimojo2, S. Tsuneta2, Y. Suematsu2, S. Miyazaki2, S. Imada1, N. Nishizuka1, K. Watanabe1, T. Dotani1, E. E. DeLuca3, S. Ishikawa4 (1: ISAS/JAXA, 2: NAOJ, 3: Harvard-CfA, 4: SSL/UCB)

2. Conceptual Layout of the Solar-C Spacecraft EUVS SUVIT X-ray Telescope (XIT) (S/C: ~6.7m in height, ~3.5m in bus module width)

3. Introduction • X-ray Imaging (Spectroscopic) Telescope for Solar-C • Perform seamless observations of the solar atmosphere (photosphere, chromosphere, transition region and corona) with a suite of 3 telescopes. • Imaging observations of the corona • Forms and mechanisms of storage and dissipation of energy • Quantitative understanding on the reconnection physics • Connectivity with the lower atmosphere (?) • Two possibilities under study for the X-ray telescope • (1) Photon-counting imaging-spectroscopic grazing incidence X-ray telescope • (2) Ultra-high-resolution normal incidence EUV telescope Context information for EUVS high-throuput spectrometer

4. Outline • Overview of the photon-counting X-ray telescope • Expected observation performance • Development activities • Summary

5. Overview of the Photon-Counting X-ray Telescope

6. X-ray Spectra from the Sun Discovery Space

7. Key Features of the Photon-Counting Soft X-ray Telescope

8. Science Targets • Energy dissipation processes in the corona that lead to dynamic activities of the corona. • MHD structures associated with magnetic reconnection during flares • Identify, e.g., shock structures (slow shock, fast shock) • Plasma conditions (temperature, heating status) in the upstream/downstream regions of a shockContinuum spectra  Determine electron temperatures • Spatial distribution and evolution of supra-thermal electrons(which serve as the seed for accelerated electrons). • Heating mechanism for active regions • In particular, for hot plasmas in the AR core: • Spatial distribution of spectral features (Disk AR・・lateral, Limb AR・・・vertical） • Temporal evolution of spectra with high time resolution by virtue of non-dispersive imaging-spectroscopy • Identify heating location and understand heating process(es) for the AR coreInformation on temperature distribution and its evolution.* This may be particularly powerful under the nano-flare-heating picture for ARs.

9. Possibilities:Shocks in the Reconnection Structure (Tsuneta,Ap.J.1996) (Tsuneta,Ap.J.1997)

10. ShockAccelerationofElectronsinCosmicPlasmas Non-Thermal Power-Law Spectrumwith g=1.95 (Koyamaetal.1995)

11. Expected Observation Performance

12. Energy Spectra(Grazing incidence angle = 0.9°) Active Regions TNET = 130 s TNET = 654 s • Imaging in Fe XVII (~4 MK) emission which is not • possible in EUV wavelength range. • Imaging in higher temperature lines (6-8 MK) with • longer net integration time. Mg Si (~6-8 MK) Fe XVII (~4 MK) 0.5 1 2 keV 0.5 1 2 keV Flares TNET= 140 s Ca (~20 MK) • Imaging at Ca XIX (at 3.9 keV; 20 MK plasma) line • Determing electron temperature from continuum Bremsstrahlung emission ※ TNET： Integration time necessary for constructing the spectra shown with a single 0.4”-size pixel. TNET = 262 s  ~30 s integration for 1.2” area, while ~10 s for 2” area. (Fe) 1 5 10 keV

13. Energy Spectra(Grazing incidence angle = 0.45°) Active Regions TNET= 262 s TNET= 654 s 0.5 1 2 keV 0.5 1 2 keV Flares Ca Fe (~20-50 MK) TNET= 133 s TNET= 800 s • Imaging at Fe XXIV-XXVI (20-50 MK) lines • Detection of supra-thermal electron emissions • from continuum Bremsstrahlung emission Fe/Ni 1 5 10 keV 1 5 10 keV

14. Development Activities

15. 55Fe X-ray Photons detected by a Back-illuminated CMOS-APS(at room temperature) CMOS sensor 55Fe source (Frame read-out at ~8.4 fps for ~870 x 650 pixels.)

16. 55Fe Event Spectra for a Back-Illuminated CMOS Sensor 3 sigma thresholdfor non-dark pixel 3 sigma threshold with (2n+3)x(2n+3) area summing for (2n+1)x(2n+1) event (n = 0, 1, 2, ..) Mn Ka (5.9 keV) 3x3 1x1 Note large peak width due to excessive pixel summation around each signal pixel(s). • For BI CMOS, all signal charges seems to be appropriately collected. • Note the device is with low-res. Si and with very thin depletion layer (~<1 mm). Nevertheless, a good fraction of events (25%) resulted in single pixel events.

17. 55Fe Event Spectra for a Front-Illuminated CMOS Sensor 3 sigma thresholdfor non-dark pixel 3 sigma threshold with (2n+3)x(2n+3) area summing for (2n+1)x(2n+1) event (n = 0, 1, 2, ..) Mn Ka (5.9 keV) 3x3 1x1 Note low energy tail for split events • For FI CMOS, some signal charges for split events are lost.

18. Ultra-Precision Surface Figuring for Grazing-Incidence Mirrors at Osaka University Figure accuracy: ~10 nm P-V needed for 0.5” HPD HXR focusing performance 30 nm 25 nm “At-wavelength phase retrieval interferometry” at SPring-8 N.B. SPIE-8139 “Advances in X-Ray/EUV Optics and Components VI” in this conference! Going to build at-wavelength Wolter mirror measurement system at SPring-8 in this Japanese fiscal year.

19. Summary • Two coronal imagers under consideration for Solar-C • (1) photon-counting X-ray telescope and (2) ultra-high-resolution EUV telescope • Science and technology for the photon-counting telescope presented. • Near-future development activities for the photon-counting telescope • CMOS-APS • Evaluate higher frame rate, low noise BI device [for read-out performance] • Evaluate nearly fully depleted BI device in collaboration with Open U., U.K. [for spectroscopic performance] • GI mirror: Near-future plans • Build at-wavelength Wolter mirror measurement system at SPring-8, and establish measurement performance for surface figures in collaboration with Osaka U., Japan. • Key technologies growing rapidly. Sufficient performance can be expected within years to come.

20. Backup Slides

21. Photon-Counting Area (Figure courtesy of e2v)

22. Non-Thermal Component down to ~4 keV (RHESSI Microflare) Non-thermal power-law spectra down to keV energy range (Hannah et al. 2008)

23. Observation Performance of the Photon-Counting X-ray Telescope