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PACS PHOTOMETER DETECTOR ARRAYS REQUIREMENTS STATUS

Detailed updates on the requirements status of a detector array linked to a Buffer Unit, including thermal budget, electrical dissipation, spectral responses, and detector performances.

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PACS PHOTOMETER DETECTOR ARRAYS REQUIREMENTS STATUS

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  1. PACSPHOTOMETERDETECTOR ARRAYSREQUIREMENTSSTATUS L. Rodriguez, O. Boulade CEA/DSM/DAPNIA/SAp

  2. Detector array and 300mK readout stage 2 detector arrays linked to a 2K Buffer Unit (BU) by thermally resistive ribbon cables BFP LETI/LIR Deliveries requirement 10 Sub-arrays - 8 for the "Blue" focal plane - 2 for the "red" focal plane

  3. BFP LETI/LIR Deliveries: Pixel/array geometry

  4. BFP LETI/SAp Delivery

  5. Measured for one ribbon cable 300 mK Thermal budget Electrical dissipation on CL Not done yet, optimisation impossible with CQM Buffer Units due to diodes protections. Conduction from 2K through 300 mK-2 K ribbon cables

  6. Electrical dissipation on BU Conduction from 4 K through 2K-4K ribbon cables Mass budgets of LETI/LIR deliveries 2 K Thermal budget & mass budget Measurements with BOLC => Still 1mW margin ! Will be used to drive signals. Not measured yet (ribbon cables just received)

  7. PACS Bands Absorption curves Blue & Red FP wavelength coverage => Blue arrayfulfils bothbands requirements

  8. Spectral uniformity Blue FP +15% Mean value -15% 60-90µm 90-130 µm +15% Mean value Spectral uniformity Red FP -15% 130-210 µm Spectral response uniformity

  9. QM DEPARTURES FROM FM • Differential mode will be upgraded on FM • BLIND PIXELS: • ON CD=Heaters: a charge resistor @ 300 mK on every blind pixel to prevent "runaway" mode. • ON CL= Bias: bias on blind pixels independent of active pixels. • In case of failure of blind pixels, on selected arrays a degradedmode can be switched on! Gap between arrays already mentioned

  10. Black body @ 21.5 K Chopper @ 25.5 K Detectors performances: responsivity Mean values over the whole array,obtained thanks to optical filters measurements at MPE.

  11. differential mode FM BU Noise distribution Channel linked to the scope Missing channel Detectors performances: noise • On arrays produced in 2000 and 2002 the noise level was dominatedby BU CMOS transistor level (~1µV/√Hz). • The QM BU delivered in 2003 was degraded by contact resistancegenerating Schottky noise 10-100 times higher than before; and clocks response times too low to cope with 40 Hz frame requirement. • We decided to mount FM Buffer Units and tested them independently from arrays.

  12. Functional performances • Multiplexing: 16->1 (by conception) : OK • Yield: on tested QM sub-arraysfunctional-active pixels (~98%)-blind pixels (~87%) but affect active pixels* =>switch able diff. mode. • Detector array dispersion: Gain: ( < 8% RMS req.) Offset:< 20 mV. ( < 50mV req.) • * One blind pixel for 8 active pixels

  13. Time sequence over 511 sec spectral density Detectors performances: NEP • CQM assembly not yet tested at Saclay. • Red CQM delivered this week. • Response measured at Grenoble before BU replacement was 2 1010 V/W. • Long duration measurements on detectors in 2002 don't show 1/f noise excess. Most pixels will be background limited.

  14. cryocooler Mylar mirror Blackbody preamplifiers Vulnérability to Ionising Particles Preliminary tests performed at Saclay end June Source 60Co Intensity: 6 kRad/h. We noticed a reversible degradation of the thermometric gainduring irradiations [0 -> 21] kRads. • Tests in particles ( p, a )planned in February at Orsay Tandem facility. • Tests in Heavy Ions planned May -June 2004 at GANIL facility.

  15. Ionisingparticles vulnerability Mechanical vibrations aging Thermal vac. Kevlar Comp SBT/JPL Warm BFP 500 h 80°C High intensityg rays Kevlar 4 K Static stiffness Warm BFP +det. arrays 50 cycles 300K-4K low intensityg rays 77 K BFP +det. arrays p, a individual particles HI individual particles When ? 2003-2004 March-april 2004 2004 Summer2003 Feb-june 2004 Early 2004 On dedicated 4 K facility On standard facility On standard facility On dedicated 300 mK facility Where ? On dedicated 77 K facility EVALUATION PLAN SUMMARY (on BFPs)

  16. CONCLUSIONS • Since IBDR CEA demonstrated the ability to manufacture completedetectors assemblies responding to PACS requirements in a reasonableschedule. • Most encountered problems today are related to the manufacture yield : processes are difficult to stabilize in a context of production rationalisation. • CQM • Our current schedule for the CQM imposes a minimal test period!!! • The Bolometer arrays will be evaluated respectively for 5 days (Red/2 sub-arrays) and 6 days (Blue/ 8 sub arrays) at BFP level. • At PhFPU level the detectors will be integrated with CQM cooler (1st time!)and tested only for 10 days before delivery. • Optimization will be impossible (specially temperature regulation) • Our knowledge of the system will be made at Inst. level tests (if possible).

  17. CONCLUSIONS cont. • FM • BU:Buffer Units (now incorporated in the CQM arrays) show expected performances levels. • CL: 300 mK readout circuits manufactured in // with BU.Not included in CQM because incompatibles with current CD. • CD: (detection layer) modified to improve differential modeoperations are in the final processing phases (see JLA).

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