Advanced CCD Imaging
Spectrometer (ACIS) |
Focal plane arrays: |
I-array (ACIS-I) | 4 CCDs placed to lie
tangent to the focal surface, used for imaging |
S-array (ACIS-S) | 6 CCDs in a linear
array tangent to the grating Rowland circle, used for either imaging
or as a grating readout |
CCD format | 1024 by 1024 pixels |
Pixel size | 24.0 µm (0.492 ± 0.0001 arcsec) |
ACIS-I array size | 16.9 by 16.9 arcmin |
ACIS-S array size | 8.3 by 50.6 arcmin |
On-axis effective area of frontside illuminated
(FI) chips (integrated over the PSF to >99% encircled energy): |
@ 0.5 keV | 110 cm2 |
@ 1.5 keV | 600 cm2 |
@ 8.0 keV | 40 cm2 |
Quantum efficiency for FI chips: | > 80% between 3.0 and
5.0 keV |
> 30% between 0.8 and 8.0 keV |
Quantum efficiency for backside illuminated (BI)
chips: | > 80% between 0.8 and 6.5 keV |
> 30% between 0.3 and 8.0 keV |
Maximum readout rate per channel | ~ 100
kpix/sec |
Minimum row readout time | 2.8 ms |
Nominal frame time | 3.2 sec (full frame) |
Allowable frame times | 0.2 to 10.0 sec |
Frame transfer time | 41 µs (per row) |
Point-source sensitivity | 4 X 10-15
ergs/cm2/s in 104 s (0.4 to 6.0 keV) |