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FOXSI : Focusing Optics X-ray Solar Imager

Steven Christe 1 , S. Krucker 2 , L. Glesener 2 , S. Ishikawa 2 , S. McBride 2 , D. Glaser 2 , P. Turin 2 , R.P. Lin 2 , M. Gubarev 3 , B. Ramsey 3 , S. Saito 4 , Y. Tanaka 4 , T. Tadayuki 4 , S. Watanabe 4 , T. Tajima 4 , H. Tajima 4 , S. Masuda 4 1 NASA GSFC, Greenbelt, MD

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FOXSI : Focusing Optics X-ray Solar Imager

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  1. Steven Christe1, S. Krucker2, L. Glesener2, S. Ishikawa2, S. McBride2, D. Glaser2, P. Turin2, R.P. Lin2, M. Gubarev3, B. Ramsey3, S. Saito4, Y. Tanaka4, T. Tadayuki4, S. Watanabe4, T. Tajima4, H. Tajima4, S. Masuda41NASA GSFC, Greenbelt, MD 2Space Sciences Lab, Berkeley, CA 3NASA MSFC, Huntsville, AL 4Astro-H team, Japan FOXSI: Focusing Optics X-ray Solar Imager

  2. FOXSI Introduction • Sounding rocket mission fundedunder NASA SR&T LCAS in 2008. • Launch scheduled for January 24th 2012. • Led by Space Sciences Lab, UC. Berkeley + NASA GSFC • Optics – NASA MSFC • Detectors – JAXA ISAS • FOXSI2 (second flight with upgraded detectors and optics) is already funded. SPIE Meeting 2011

  3. FOXSI Science Motivation (weak) Thin target emission RHESSI HXR Obs. thermal • RHESSI Limitations • Dynamic range (~10) • Sensitivity (intense) Thick target footpoints Need higher sensitivity and dynamic range (than RHESSI). SPIE Meeting 2011

  4. FOXSI Heritage • Leveraging technologies developedfor astrophysical observations. • HXR electroform-nickel replicated optics as flown on the HERO balloon payload (Ramsey et al. 2002) • Double-sided Si strip detectors (Kokubun et al. 2010, built for HXI on Astro-H) • The Sun is a star but… SPIE Meeting 2011

  5. Solar Requirements • Compared to astrophysical observations, solar observations require • High angular resolution (< 10 arcsec FWHM) • High dynamic range (sharply peaked PSF). • The ability to handle high count rates (thousands of counts/s). SPIE Meeting 2011

  6. FOXSI Payload Overview Telescope modules (7 shells & 7 modules) This way up 22 in rocket skin (yellow) 2 m-long Al tube (gray) Detector plane(7 Si DSSDs) Full moment cantilever connection (green) SPIE Meeting 2011

  7. FOXSI Optics Details • Focal Length: 2 m • Number of modules: 7 • Number of shells: 7 (10) • Optics Type: Wolter I • Outer shells radius: 51.51 mm • Inner shell radius: 37.99 mm (32.48 mm) • Shell length: 60 cm. • Energy range:up to ~15 keV * Values in parenthesis are for FOXSI2. SPIE Meeting 2011

  8. Effective area • FOXSI’s effective area • Blue represents the current configuration for the flight in 2012 • Redrepresents an upgraded configuration for a flight in 2014 • Due to increased area and smaller detectors, FOXSI will be ~50 times more sensitive than RHESSI (in this energy range). 2011 2013 The dashed line represent the area provided by the optics. The effective area including thermal blanketing and detector response is also shown (solid lines).

  9. Shell Alignment Clips • Maintaining shell alignment during sounding rocket launch loads is nontrivial. • During vibration tests resonances were found in the outermost (largest) shells. • Special clips were designed which connectthe mounting spider to mirror shells • Spread out launch loads • Reduces epoxy-shrinkage-induced axial figure error SPIE Meeting 2011

  10. Shell Alignment Process • Shells are built up from the inner to outer. • Micropositionersat three points are used to enforce circularity before bonding. • The circularity of each shell is monitored in real time during bonding process. Module Integration stand SPIE Meeting 2011

  11. FOXSI Optics • Shell resolution is 6-7 arcsec (FWHM). • Measured module resolution7-8 arcsec. • Little to no loss of resolution in alignment process. • Module HPD ~26 arcsec. SPIE Meeting 2011

  12. Dynamic Range • FOXSI dynamic range • PSF falls 2 orders of magnitude <30 arcsec. • 3 orders of magnitude <60 arcsec. • Giving a dynamic range of 100-1000 for solar flare observations. • 10-100 better than prev. solar HXR observations (RHESSI). (4-15 keV) SPIE Meeting 2011

  13. FOXSI Detectors • Double-sided Silicon Strip Detectors (DSSD) • 128 x 128 strips, 500 mm thick • 75 mm pitch(9.6 x 9.6 mm) • Efficiency 98% for 10 keV68% for 15 keV • Energy resolution ~ 1 keV • CdTe DSSDfor FOXSI2 FOXSI detector board with wirebonded detectors

  14. Conclusion • FOXSI will be ready for its first flight inJan 2012. • FOXSI • will provide <8 arcsec resolution HXR images of the Sun. • will investigate the presence of nonthermal electrons in the quiet Sun in its first flight. • will be a pathfinder for the next generation of solar hard x-ray spectroscopic imagers. • Satellite and balloonversions of FOXSI are under investigation. SPIE Meeting 2011

  15. SPIE Meeting 2011

  16. FOXSI Electronics • DSSDs read out by 4 ASICs (developed in part by GM Ideas) in photon counting mode. • FPGA (developed at SSL) clock each detector, perform data reduction, and package data. • Formatter adds telemetry data and sends to transmitter. ASICs DSSDs x 7 Formatter Transmitter FPGA SPIE Meeting 2011

  17. FOXSI Science • Main unsolved problems in solar physics • How and Why of particle acceleration (e.g. energetic electrons in solar flares). • Coronal Heating (energy release in the so-called quiet Sun). • Best tackled through HXR observations but need high sensitivity and dynamic range. • For indirect imaging (e.g. RHESSI), this is difficult. • HXR focusing optics combined with position-sensitive detectors can provide both. SPIE Meeting 2011

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