ACIS On-Orbit Instrumental Background Rate Predictions

09Mar99/fkb

XRCF:

(1/2 CR/frame)/(20 cm² s/frame) = 1/40 CR/cm²/s (ACIS telem at XRCF)

(1/40 CR/cm²/s)/(2*pi) = 4.0e-3 CR/cm²/s/sr (EPHIN/Chandra at TRW)

HEO/XRCF:

(0.32 CR/cm²/s/sr)/(4.0e-3 CR/cm²/s/sr) = 80.0 (Meyer, ARAA, 1969)

(0.38 CR/cm²/s/sr)/(4.0e-3 CR/cm²/s/sr) = 95.0 (EPHIN/SOHO at L1)

=> Scale instrumental background rates by 100x to convert from sea-level rates to HEO rates with a safety margin of 5-20%.

HEO FI: (1/40 CR/cm²/s)(10 ct/CR)(100) = 25 ct/cm²/s = 150 ct/s/CCD

HEO BI: (1/40 CR/cm²/s)(1.5 ct/CR)(100) = 4 ct/cm²/s = 24 ct/s/CCD

Predicted On-Orbit ACIS Instrumental Background Fluxes vs.
Event Grade & Amplitude Filter

CCD
Type E ‹ = 10 KeV 10 keV ‹ E ‹ = 100 keV E ‹ = 100 keV

G02346 G0123456 B0-254 B0-255 B0-255 B0-255

(ct/cm²/s/keV) (ct/cm²/s/keV) (ct/cm²/s/keV)

FI 0.015 0.018 0.19 2.0 0.056 0.25

BI 0.026 0.030 0.077 0.080 0.036 0.040

CCD Type	E ‹ = 10 KeV	10 keV ‹ E ‹ = 100 keV	E ‹ = 100 keV
G02346	G0123456	B0-254	B0-255	B0-255	B0-255
(ct/cm²/s/keV)	(ct/cm²/s/keV)	(ct/cm²/s/keV)
FI	0.015	0.018	0.19	2.0	0.056	0.25
BI	0.026	0.030	0.077	0.080	0.036	0.040

Predicted On-Orbit ACIS Instrumental Background Rates vs.
Event Grade & Amplitude Filter

CCD
Type E ‹ = 10 KeV E ‹ = 100 KeV
G02346 G0123456 B0-254 B0-255 G02346 G0123456 B0-254 B0-255
(ct/s/CCD) (ct/s/CCD)
FI 1 2 12 121 3 4 27 150
BI 2 2 5 5 5 5 24 24
(ct/s) (ct/s)
I-array 7 12 65 610 20 25 159 774
S-array 8 12 58 494 22 26 156 648