1. 3/16/04mwb, sek, MIT/CSR MIT XIS Status 16 March 2004 Overview: TCE board rebuild status Back-illuminated CCD performance & status (Slightly) improved FI resolution w/ new  s Improved BI resolution in PSUM mode Grades, gain & resolution in BI devices How should we use charge injection? Initialization issues

2. 3/16/04mwb, sek, MIT/CSR Thermal Control Electronics Board Status Four (revised) flight boards passed acceptance level vibration & thermal tests at MIT Boards hand-carried to ISAS today TCE board engineering test script defined, sent to Japan Plan to install & test boards in flight AE/TCE in Osaka next week Plan workmanship shake at ISAS (April?)

3. 3/16/04mwb, sek, MIT/CSR Back-illuminated CCD Progress Traditional BI CCDs provide much better low-energy QE (x 3 at 0.5 keV), but much poorer spectral resolution (x 2-3 at 0.5 keV) than FI CCDs Problem is ascribed to poor charge collection at the back surface of the detector. The chemisorption-charging (CC) backside treatment process (M. Lesser) has shown promise for UV detectors. We have recently obtained excellent X-ray results with back-illuminated XIS CCDs treated with the CC process.

4. 3/16/04mwb, sek, MIT/CSR Back-illuminated CCD Progress At November XIS team meeting we reported results from first chemisorption-charging XIS BI device. Progress since then: –4 more devices tested (5 total) from 2 wafers (1 CI wafer 1 non-CI wafer) –Revised clock voltages found (lower noise, no spurious charge) –Two devices calibrated (1 CI, one non-CI); QE model constrained –Charge injection function verified –40 MeV proton irradiation to check radiation tolerance –Dark current, background rejection efficiency measured –>1000 hours total “CCD clocking” test time; ~50 thermal cycles –Flight sensor base with BI CCD built, passed vibration acceptance testing; thermal test in progress. Generally, performance fulfills promise of first test results

5. 3/16/04mwb, sek, MIT/CSR Spectral Resolution & Quantum Efficiency Comparison: Back- & Front-illuminated XIS CCDs 277 eV: QE BI /QE FI = 40.3 FWHM BI = 50-55 eV FWHM FI = 50-55 eV 525 eV: QE BI /QE FI = 3.3 FWHM BI = 60-65 eV FWHM FI = 45-50 eV BI split threshold: 7e -

6. 3/16/04mwb, sek, MIT/CSR Measured XIS BI CCD Quantum Efficiency BI QE Model Parameters + BI Measurements

7. 3/16/04mwb, sek, MIT/CSR Chemisorption Charging Process Back Surface Structure 45  m Si 3 nm SiO 2 1 nm Ag 5 nm HfO 2 [ Deadlayer Sensitive Volume (not to scale) (Burke, Lesser et al., 2003)

8. 3/16/04mwb, sek, MIT/CSR XIS Effective Area Comparison: 1 BI Sensor vs 1 FI Sensor Includes XRT-I area & transmission of all filters

9. 3/16/04mwb, sek, MIT/CSR XIS Spectral Resolution: FI & BI CCDs

10. 3/16/04mwb, sek, MIT/CSR XIS Spectral Resolution Comparison: BI vs FI Simulated Spectra of SNR E0102 -72.3 Back-illuminated Front-illuminated OVII OVIII

11. 3/16/04mwb, sek, MIT/CSR BI CCD Spectral Resolution: XIS, Chandra ACIS & XMM-Newton EPIC-PN Simulated Spectra of SNR E0102 -72.3 XIS BI & FI Chandra ACIS-S XMM-Newton EPIC-PN 4.6 c s -1 (4 FI) 6.9 c s -1 (2 FI+2 BI) 3.1 c s -1 8.0 c s -1 (EPN) 5.0 c s -1 (2EMOS) 10 20 0 0 1.5 0 ct s -1 keV -1 Energy (keV) ct s -1 keV -1 Note: EPIC MOS Resolution comparable to XIS (but is not a BI CCD)

12. 3/16/04mwb, sek, MIT/CSR XIS Dark Current Comparison: BI vs FI

13. 3/16/04mwb, sek, MIT/CSR Radiation Induced Pulse-height Shift in BI CCD Event Center Pixel Pulse-height (adu) Column Number

14. 3/16/04mwb, sek, MIT/CSR Radiation-Induced Loss of Spectral Resolution BI CCD at 5.9 keV FWHM at 5.9 keV (eV) Column Number

15. 3/16/04mwb, sek, MIT/CSR Radiation-Induced CTI Increase in XIS BI & FI CCDs

16. 3/16/04mwb, sek, MIT/CSR Background Rejection Efficiency Comparison: BI, FI similar @ E <1 keV BI better 1-2.5 keV by x 2 ( mostly lower Si K fluorescence) FI better 2.5-12 keV by x2.5 60 Co Gamma/e - Response Comparison G02346 events

17. 3/16/04mwb, sek, MIT/CSR BI Resolution in PSUM Mode

18. 3/16/04mwb, sek, MIT/CSR BI CCD Pulse-height vs Grade (390 eV)

19. 3/16/04mwb, sek, MIT/CSR BI CCD Pulse-height vs Grade Selection

20. 3/16/04mwb, sek, MIT/CSR BI Test Experience Summary 5 BI devices tested from 2 wafers >1000 hours total cold CCD-clocking time > 50 thermal cycles (25 thermal cycles on one device) Nominal calibration measurement suite run on 2 devices Radiation testing (40 MeV protons) on one device 60 Co response checked BI devices require slightly different clock levels Flight-sensor base passed acceptance vibration; thermal test in progress. No peculiar gain or QE instabilities noted to date.

21. 3/16/04mwb, sek, MIT/CSR Possible Additional BI ‘Stability’ Tests UV (2600 A) flood test (at CSR): *Flood CCD with light from EEPROM burner *Look for gain/QE drift at low energies due to interface charging Ly  test (at Lincoln Lab): *Have ‘loaned’ one device to UV instrument team at LL *They will check response at Ly  *This test will check deadlayer model Extended high-temperature (+60C) aging test? *2-day ‘informal’ test already done Others?

22. 3/16/04mwb, sek, MIT/CSR Additional BI Calibration Needed Additional QE data E< 0.5 keV *‘Deadlayer is known only to 70 ± 20 nm *Additional data at 180 eV, 390 eV would be useful Energy-scale data at E< 2 keV *Energy scale is not linear here Spectral resolution with flight AE/TCE (all E) *BI resolution is quite sensitive to AE/TCE noise Spatial QE non-uniformity at E> 6 keV *BI CCD seems to be slightly thinner than expected

23. 3/16/04mwb, sek, MIT/CSR XIS Sensor Base with Back-illuminated CCD CCD calibrated at MIT Vibration test passed 5 March Thermal test in progress Anticipate shipment 24 March

24. 3/16/04mwb, sek, MIT/CSR XIS BI Sensor Base Delivery Prospects Anticipate 1st BI sensor base (with CCD w1.8c5) ready for shipment 24 March Next flight candidate BI CCDs: *w1.8c2 now under test; CTI worse than w1.8c5 but could fly *w1.8c8 expected at CSR now *Third wafer still at University of Arizona Engineering team has ISS commitments through April CCD team (Bev) will calibrate 2nd flight BI device in April Expect to deliver 2nd BI sensor base at end of May

25. 3/16/04mwb, sek, MIT/CSR FI Resolution & Noise with reduced Serial Clocks

26. 3/16/04mwb, sek, MIT/CSR How should we use charge injection? Two possible uses: –CTI measurement (with checkered flag to allow ground correction) –CTI reduction (with grid to fill traps) Tsuru-san finds poor correlation between injected amplitude & X-ray amplitude: –Very interesting & useful analysis; we had not done this! –Injected charge must be summed as events for stable injection (why?) –Inherent CTI in w1.3c6 is rather small (< 5 x 10 -6 ) –I think there is hope for this method but I haven’t done my homework So-called ‘grid’ method is very promising: –Improves resolution for radiation-damaged FI & BI chips –Loss of QE seems as expected (or better!) –How will DE handle injected grid? What about extra hot pixel rate? Main questions: How & when do we decide about use of CI?

27. Massachusetts Institute of Technology Center For Space Research 27

28. Massachusetts Institute of Technology Center For Space Research 28 An Example: Injecting a Grid Pattern Charge injection is programmable. Purpose of “Grid” program is to reduce radiation damage effects: *Charge is injected in each column of every 54th row. *Injected charge (temporarily) fills radiation-induced traps. *Filled traps cannot contribute to charge transfer inefficiency. *Result is better spectral resolution. Rows filled by charge injection Charge moves down during readout ID/IG Input Register Charge moves right during injection

29. Massachusetts Institute of Technology Center For Space Research 29 Effect of Proton Irradiation on XIS Response Prelaunch: FWHM: 132 eV. Post-irradiation (2 yr on-orbit equivalent): Gain shift 1.3%; FWHM: 210 eV Without Charge Injection

30. Massachusetts Institute of Technology Center For Space Research 30 Effect of Proton Irradiation on XIS Response Prelaunch: FWHM: 132 eV. Post-irradiation with charge injection: Gain shift 0.5%; FWHM: 144 eV With Charge Injection

31. 3/16/04mwb, sek, MIT/CSR CTI at 5.9 keV vs Charge Injection Level Radiation-damaged BI CCD

32. 3/16/04mwb, sek, MIT/CSR Radiation-Induced Loss of Spectral Resolution in BI CCD FWHM at 5.9 keV (eV) Column Number

33. 3/16/04mwb, sek, MIT/CSR Resolution Improvement with Charge Injection Radiation-damaged BI CCD at 525 eV

34. 3/16/04mwb, sek, MIT/CSR CI Grid Period(rows)/ Open Fraction 277 eV525 eV1.5 keV5.9 keV * 54/0.9810.9550.9470.9540.978 114/0.9910.9820.9810.9861.008 Relative QE with Grid Charge Injection Radiation Damaged BI device For quad B of BI w1.8c6 after 40 MeV proton irradation Based on ‘counts under peak’; statistical precision ~0.005 Injected charge rows treated as 0 in event finding * NB: 5.9 keV data do NOT have hot pixels removed