X-ray Imaging Spectrometer (XIS)
Description

Figure 3. Response of back-illuminated (BI; red) and front-illuminated (FI; black) XIS sensors to characteristic X-rays from a boric oxide target. The BI device provides the expected large increases in quantum efficiency at carbon K (277 eV) and oxygen K (525 eV), and also exhibits excellent spectral resolution, comparable to that of the FI device, in this spectral band. Note that the BI device also detects boron-K emission, and so has measurable response at energies as low as 180 eV. NB: the CCDs used in this test are not the flight devices, so these values are approximations only. In particular, the depletion depth of the flight BI chip is somewhat smaller than the test device. The flight values will be fully determined in orbit.

Last updated: Wed May 10 17:33:19 EDT 2006 email: milleric@mit.edu