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Hard X-ray Imager

The HXI is a 5cm × 5cm Double-sided Strip Cadmium Telluride (DS-CdTe) detector located behind the WFI and observing simultaneously with it. Its 0.5 mm thickness affords nearly 100-percent detection efficiency for 40 keV X-rays. The HXI will have energy resolution better than 1 keV (FWHM) at 30 keV and a FOV of 8 arcmin × 8 arcmin.

The HXI will extend the energy coverage up to 40 keV and enable simultaneous observations with both detectors.

As a consequence of their co-location, the two instruments WFI and HXI will share the same optical axis and the same baffle structure, with heavy metal sheets added for hard X-ray coverage. See WFI/HXI layout.

To suppress background, an active anticoincidence shield will surround five sides of the imager. In addition, two layers of Double-sided Silicon Strip Detector (DSSD) will be mounted above the CdTe to serve as particle background detectors and detectors of 7 – 30 keV X-rays.

A thermal shield will be required between the WFI and HXI since they operate at different temperatures. The HXI cooling design, mechanical structure and electrical interfaces will all be independent from the WFI, so that both instruments can be operated separately.

The HXI is based on proven technology— the cadmium-telluride (CdTe) detectors for the HXI focal plane have considerable flight heritage. INTEGRAL/IBIS uses a CdTe array which has worked flawlessly in orbit since its 2002 launch. The IXO HXI shall be an advanced version of the HXI to fly in 2014 on JAXA´s ASTRO-H. One aspect that requires investigation is the design of an optimum engineering solution for mounting the HXI behind the WFI.

Read more about electroformed nickel replication mirror for the Hard X-ray Imager

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Selected References

• Takahashi, T. et al., 2005, Nuclear Instruments and Methods in Physics Research A 541 332–341
• Design and development of the SIMBOL–X hard x–ray optics, Pareschi, G.; Attinâ, P.; Basso, S.; Borghi, G.; Burkert, W.; Buzzi, R.; Citterio, O.; Civitani, M.; Conconi, P.; Cotroneo, V. et al., SPIE Vol. 7011 (2008)
• Development of a prototype nickel optic for the Constellation-X hard x-ray telescope, Romaine, S.; Basso, S.; Bruni, R. J.; Burkert, W.; Citterio, O.; Cotroneo, V.; Engelhaupt, D.; Freyberg, M. J.; Gorenstein, P.; Gubarev, M. et al., SPIE Vol. 6688 (2007)
• Development of a prototype nickel optic for the Constellation-X hard x-ray telescope: IV, Romaine, S.; Basso, S.; Bruni, R. J.; Burkert, W.; Citterio, O.; Conti, G.; Engelhaupt, D.; Freyberg, M. J.; Ghigo, M.; Gorenstein, P.; and 8 coauthors, SPIE Vol. 6266 (2006)
• The Con-X Hard X-Ray Telescope and its angular resolution, Gorenstein, P.; Romaine, S.; HXT Integral Optics Team, AAS Vol.207 (2005)
• Development of a prototype nickel optic for the Constellation-X hard x-ray telescope, Romaine, S.; Gorenstein, P.; Bruni, R.; Pareschi, G.; Citterio, O.; Ghigo, M.; Mazzoleni, F.; Spiga, D.; Basso, S.; Conti, G.; and 8 coauthors, AAS Vol. 207 (2005)
• Long-term Stability and High Energy Reflectivity Measurements of Depth Graded Multilayer Coatings for X-ray Optics, Unks, B. E.; Bruni, R. J.; Eguchi, H.; Gorenstein, P.; Romaine, S. E., AAS Vol. 205 (2004)