Absolute Quantum Efficiency of Selected Flight Devices

  In this section we present best-estimate absolute quantum efficiency curves for two flight devices. The devices are serial numbers w182c4r, a front-illuminated device in the S2 position of the ACIS focal plane, and w134c4r, a back-illuminated device in the S3 position. In each case the absolute quantum efficiency has been derived from the relative quantum efficiency measurements described above in section 4.7.2, together with the absolute quantum efficiency measurements described in section 4.6.1. In modelling the high-energy quantum efficiency of the S3 detector, we have also used measurements of relative quantum efficiency (of S3 with respect to S2) obtained during XRCF phase I. The modelled quantum efficiency of the S2 detector is shown in Figure 4.66. The modelled quantum efficiency of the S3 detector is shown in Figure 4.67.

These quantum efficiency curves have been provided to the AXAF science center as files named w182c4r_eff_997.qdp (for the S2 device) and w134c4r_eff_pre_997.qdp (for the S3 device). It is intended that these files be available from the MIT ACIS web page at http://acis.mit.edu. The files can be found on the MIT database in the directory /ohno/di/database/rsp/release.

  

Figure 4.66: Best-estimate ACIS S2 (Front-illuminated) Detector Quantum Efficiency Model

  

Figure 4.67: Best-estimate ACIS S3 (Back-illuminated) Detector Quantum Efficiency Model

Some notes on the computation of the relative quantum efficiency for each device follow. These notes are included as headers in the quantum efficiency files.