1. Calibration of swept charge devices (CCD-54)
Shyama Narendranath (ISRO Satelleite Centre)
Chris Howe and RAL/C1XS team,
P. Sreekumar (IIA) & P.S.Athiray (Manipal University)

2. Swept charge devices(e2V)
Similar to X-ray CCDs
Non-imaging, large area 1 cm x 1 cm
passive cooling, good performance at -15 degC
Single read out direction, simpler to use
Higher radiation tolerance compared to standard X-ray CCDs

3. Ground calibration plan
Objectives
Derive spectral re-distribution function and its energy dependence
Derive absolute detection efficiency of the swept charge devices
Methodology
Calibrate a reference detector (XR-100 CR Amptek Si-PIN ) at BESSY II
X-ray beam set up with DCM for SCD calibration with reference detector at RAL / RESIK

5. Si-PIN (transfer std) calibration

6. BESSY II measurements

7. Mono-energetic spectra from 0.6 to 10 keV
Steps of 1 eV near the absorption edge
Efficiency relative to Si(Li) detector
Spectral fits to mono-energetic spectra of Si-PIN transfer standard
Photopeak
Escape peak
Pile up
LE shelf

9. Bounds derived on detection efficiency of Si-PIN transfer standard

10. Bounds derived on characteristiscs of Si-PIN transfer standard

11. SCD calibration

12. SCD calibration at RESIK (RAL)
X,Y,Z movement
Replaceable
Quartz double crystal
Variable slit size
~ 4 m

15. SCD SRF at 8 keV
SRF (E, C, T) = photo peak + low energy tail+ low energy shelf+ split events + escape peak
Photopeak
Escape
peak
Power law
LE tail
LE shelf
Cut off

16. Calibration steps

17. Spectral fits to mono-energetic spectra

18. SCD-SRF as a function of energy
Bounds derived on detection efficiency of Si-PIN transfer standard

19. SCD Detection efficiency

20. Onboard calibration Fe-55 on the door Cosmic X-ray Background
Ar XRF from Earth’s atmos
Cosmic X-ray Background
(Model from Kushino et al 2004)

21. Uncertainties and error propogation
Assumptions
X-ray beam is parallel
Active area of detectors as given by manufactures
Error propagation at every stage
Uncertainity of ~ 5 % derived, including the spread in detection efficiency, across the 24 SCDs

22. C1XS background in orbit
Geotail bkg
Excess in sunlit side
Nominal bkg
Bkg in geotail

23. C1XS achievement - First detection of Na
1.04 keV
First direct measurement of enhanced Na abundances from the lunar surface
The best fit to one of the C1XS spectrum with all components
6th July 2009 (17:10:47 -17:13:59)

24. CLASS
4 cm2 area CCD-236 devices