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JEM-X Status S. 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. Hardware performance (no news). Electronics The performance of the JEM-X electronics has been nominal

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jem x status s brandt on behalf of the jem x team

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

hardware performance no news
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

software performance
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

detector performance is stable and unchanged
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

status of the microstrip anodes
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

jem x detector gain increase ageing
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

temporary gain recovery
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

detector resolution evolution
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

jem x hv setting
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

jem x irem reaction is disabled
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

correlation of the jem x background rate and ground based cosmic ray monitor data from oulu
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

expected evolution of the background
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

dither pattern
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

slide14

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

sensitivity gain by operating both jem x units improvement for isolated weak sources
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

conclusions
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

not the end

NOT THE END

of INTEGRAL (or JEM-X)