JEM-X Status S. Brandt on behalf of the JEM-X team

1. JEM-X StatusS. Brandt on behalf of the JEM-X team Partly based on a presentation at ESOC, Feb 2005 at review marking the end of the nominal INTEGRAL mission ESAC, March 14, 2005

2. Hardware performance(no news) • Electronics • The performance of the JEM-X electronics has been nominal • No resets of DFEE CPU • No ageing of FPGA • Unchanged performance of amplifiers • Mechanical • No gas leak of Be window • No detectable contamination of the Xe gas • Detector collimator geometrical details are harder to model than expected. Vignetting function at large off-axis angles has some uncertainties. SDAST Meeting,March 2005 JEM-X Status Søren Brandt page 2

3. Software performance • DFEE software • Performance has been nominal • Software patches have been introduced to tune detector performance and increase event processing speed(no new ones recently) • DPE software • Performance of IASW and CSSW have been nominal • One SW patch to correct broadcast packet interpretation • SW patch to raise class of OEM 191 is pending • One reset of CSSW/IASW has occurred; most likely due to SEU • A few cases of failure to restore context after DFEE switch-off has occurred (one recent case during December eclipse season was quickly corrected by MOC) SDAST Meeting,March 2005 JEM-X Status Søren Brandt page 3

4. Detector performance (is stable and unchanged) • Anomaly I • Degradation (loss of anode strips) of detector micro-strip due to heavy cosmic ray nuclei • Action: • Reduce HV from 900V to 820V, reducing the gain from ~1500 to ~600 • Use only one JEM-X unit at a time for the nominal mission • Impact: • Lower sensitivity in the ~3 to ~4 keV range • One unit only provides lower sensitivity for weak sources • Anomaly II • Steady increase of detector gain over time due to ion drift in glass substrate • Action: • Reduce HV one step (10 V) when needed to maintain constant gain within +- 10% • Impact: • Slowly degrading energy resolution • Slow change of spatial gain map • Operational inconvenience SDAST Meeting,March 2005 JEM-X Status Søren Brandt page 4

5. Status of the microstrip anodes Six anodes have been lost since JEM-X1 was reactivated in March 2004. We do not expect a similar loss rate in the future since three of these anodes were in a weak group already in Nov.-Dec. 2002. JEM-X1 February 2003 JEM-X1 March 2004 JEM-X1 January 2005 SDAST Meeting,March 2005 JEM-X Status Søren Brandt page 5

6. JEM-X detector gain increase (ageing) • Both units show increase of gain of ~1% per orbit of use (HV on) relative to the original gain  relative gain increase slows down to ½% per orbit after 100 orbits and to 1/3% after 200 orbits of use • Slow-down of gain increase in JEM-X1 due to lower temperature is inconclusive, but average lowering of detector tempeture is only ~2.5C • Lower temperature may slow down degradation of energy resolution DV corrected gain JEM-X2 JEM-X1 DV corrected gain Actual gain SDAST Meeting,March 2005 JEM-X Status Søren Brandt page 6

7. Temporary gain recovery • After extended period of HV-off the gain returns to its original value (the charge configuration is restored) • However, accelerated ”ageing” to a stable state then occurs over a period of 10-20 hours • Activation of dormant unit for science use should take this effect into account • Also impact on data taken after extended period of solar activity (like Jan 2005, where HV was off for 1 week) SDAST Meeting,March 2005 JEM-X Status Søren Brandt page 7

8. Detector resolution evolution • The energy resolution is slowly degrading (slower in JEM-X1 than in JEM-X2) • The resolution of JEM-X1 is now 10.5% @ 22 keV compared to 9% just after launch • The resolution of JEM-X2 is now about 12% @ 22 keV • The gain evolution may be slightly non-uniform over the plate, causing a slow drift in the spatial gain map • The spatial gain map is monitored by the Xe flourecense background line at 30 keV JEM-X1 JEM-X2 SDAST Meeting,March 2005 JEM-X Status Søren Brandt page 8

9. JEM-X HV setting • Due to ”frequent” lowering of the HV setting to keep a constant gain the HV value is now set by ISOC • However, a conservative HV setting must be kept in the MOC DB to avoid high gain after manual recovery • Responsibility of the instrument team to plan ahead and coordinate with MOC DB updates Example of JEM-X gain after recovery performed where the MOC DB contained ”old” HV setting SDAST Meeting,March 2005 JEM-X Status Søren Brandt page 9

10. JEM-X IREM Reaction is disabled • Experience shows that JEM-X internal radiation protection logic works well • Software switch-off mechanism only active when in data taking (but that is almost always the case) • Hardware switch-off mechanism always active • Using IREM may cause loss of science time • Conclusion: disable JEM-X reaction to IREM (OCR #183 implemented) Example of ”normal” IREM induced HV-off about 5-10 min before internal JEM-X mechanism would have triggered. SDAST Meeting,March 2005 JEM-X Status Søren Brandt page 10

11. Correlation of the JEM-X background rate and ground based cosmic ray monitor data from Oulu • The JEM-X noise count rate has grown by 40 % since the start of the mission. • The increase is closely correlated with the cosmic ray activity as measured by ground based neutron monitors. JEM-X Oulu SDAST Meeting,March 2005 JEM-X Status Søren Brandt page 11

12. Expected evolution of the background What about IBIS and SPI ? Oulu 40 years cosmic ray history The prediction is that the JEM-X rate will increase by another 20-40% as the Solar minimum evolves JEM-X/INTEGRAL 2 years SDAST Meeting,March 2005 JEM-X Status Søren Brandt page 12

13. Dither pattern • HEX dither is preferred when continuous JEM-X coverage is important • 5x5 dither does not provide continuous coverage and vignetting far off-axis is still not completely modeled • Staring observations introduce artifacts in the imaging and is discouraged • Artifacts in HEX and 5x5 observations may be further reduced by not exactly repeating the pointing pattern (suggested scheme from Niels Lund) SDAST Meeting,March 2005 JEM-X Status Søren Brandt page 13

14. Moving the center point for hex dithers Original center point Additional center point positions 120’ 40’ 72’ Original dither points SDAST Meeting,March 2005 JEM-X Status Søren Brandt page 14

15. Sensitivity gain by operating both JEM-X units:improvement for (isolated) weak sources • Assumptions: 100 counts per TM packet, 30 c/s background per unit, 1 Crab is 125 c/s, 7 science TM packets per 8 sec • 2 gain below ~110 mCrab total source flux, no gain above 460 mCrab • For allocation of 10 science TM packets, 2 gain below ~260 mCrab, no gain above 760 mCrab • General improvement of imaging by reduction of artifacts • Detector ageing increases by a factor of 2 10 science TM 7 science TM SDAST Meeting,March 2005 JEM-X Status Søren Brandt page 15

16. Conclusions • The JEM-X performance has been nominal, aside from the ”ageing” of the micro-strip substrate described above • Operations have been smooth, with efficient and competent monitoring and speedy recovery actions at MOC, keeping the loss of observing time to an absolute minimum • The planning at ISOC has been efficient and the support for the Observers Manual has been strong • The monitoring of the science TM by the ISDC operators has been helpful and the extra support for the JEM-X Instruments Station has been much appreciated • The handling of ”change requests” has been very flexible and great efforts have been put into finding ways of implementing the wishes of the JEM-X team • The Coordination Meeting has been an important forum for the Instrument Team to gain understanding of the different branches of the ground segment • JEM-X is ready to support the continued operations of INTEGRAL • Lesson learnt: Instrument team access to raw data should have been should have been included in the system design SDAST Meeting,March 2005 JEM-X Status Søren Brandt page 16

17. NOT THE END of INTEGRAL (or JEM-X)