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FM-LS Tests

FM-LS Tests. Warm Functional Tests Separate warm functional test on each module Warm functional test after integration in MPIA test cryostat Cold Performance Tests Cold functional test Cold performance test Variation of Detector-Bias, C int , t int Using different Filter combinations

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FM-LS Tests

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  1. FM-LS Tests • Warm Functional Tests • Separate warm functional test on each module • Warm functional test after integration in MPIA test cryostat • Cold Performance Tests • Cold functional test • Cold performance test • Variation of Detector-Bias, Cint, tint • Using different • Filter combinations • BB-temperatures • Detector temperatures • Dark measurments MPIA Test Facility f-ratio as in PACS IR-flux attenuation: ~ 2.5· 10-6

  2. FM LS-Sevenpacks FM-LS during integration into MPIA test cryostat

  3. FM LS-Sevenpacks FM 115 (LS 1) channel #14 FM 122 (LS 2_2) channel #7

  4. Responsivity / NEP UBias = 200mV, TDet = 2.5K FM 126, FM 135, FM 136: higher stress (mounting screw of the test housing pressed the module) modules OK Responsivity NEP LS 1 LS 2_2 LS 5 LS 6 Responsivity: 7.4 A/W ± 1.7 A/W NEP: 1.18 · 10-16 A/W ± 4.6 · 10-17 A/W

  5. Responsivity - Homogenity UBias = 200mV, TDet = 2.5K, Cint = 240 pF Spiking pixel FM 114 ch. #4 FM 122 ch. #7 open Spiking pixel FM 115 ch. #14 higher stress on FM 135 and FM 136 higher stress on FM 126

  6. Responsivity - Bias Scan TDet = 2.5K w/o spiking and open pixels FM 126 (LS 5), FM 135 (LS 6), FM 136 (LS 6): higher stress caused by mounting in the test housing

  7. NEP - Bias Scan TDet = 2.5K w/o spiking and open pixels FM 126 (LS 5), FM 135 (LS 6), FM 136 (LS 6): higher stress caused by mounting in the test housing

  8. Dark Current [e-/s] UBias = 200mV, TDet = 2.5K LS1 Mean: 3550 e-/s± 600 e-/s Requirements: CD ≤ 5*104 e-/s LS 1 LS 5

  9. Band Gap FM 120, Ch 2 (LS 1) 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 Band gap [meV] Thermal excitation: Idark ~ exp (-E/kTDet) photon flux on detector LS 6 LS 5 Higher stress on 3 FMs  smaller band gap

  10. Ionizing Radiation and Curing • Goal: High absolute photometric accuracy in the FIR during „quiet“ periods (~ 1%) • Essential: • - Stable operation of Ge:Ga-detectors in PACS at L2 • - Optimize operating conditions: UBias, TDet • - Minimize curing and calibration frequency • Radiation Environment at L2: • - Galactic CR particles (low level fluxes: 3-5 ions/cm²/s; typical energy: 500 MeV – few GeV) • - Solar particles events (avg. sol max: 2.5 · 105 ions/cm²/s; Ep ≈ 100 MeV, Eions ≈ GeV range) • Radiation damage in extrinsic photoconductors • - Generation of electron hole pairs in bulk of detector • - Capture of minority carriers by compensating impurities • Effects on Detector Performance: • - Spikes / glitches • - Higher detector noise, dark current, detector output  change of calibration • - Lower S/N No stable operation of Ge:Ga detectors

  11. Ionizing Radiation Tests Long term measurments with 137Cs • Conditions • Simulated PACS operation conditions • Realistic FIR background: 10-14 W/pix • Low stressed Ge:Ga detector array • ~48 hours each • Every 1 to 10 min a measurement • Without irradiation (preparatory test) • Performance of detector and the test setup • Analysis of systematic effects  Measurments highly reproducible with stability < 1% • 137Cs detector irradiation • L2 radiation environment: 137Cs source (Eγ = 0.662 MeV) • Hit rate (> 3σ): ~16/s/pix Radioactive 137Cs source Generic charge ramp

  12. Deglitching Method • Glitch detection & deglitching: • sigma clipping applied to pairwise differences (values >3σ) • Skewed distributions: • Robust estimator, e.g., Hodge-Lehmann estimator: μ= median (Xi+Xj)/2 with 1 ≤ i ≤ j ≤ n Glitches skewed distribution

  13. NEP and Responsivity UBias = 160mV, TDet = 2.5K 5h Glitch rate: Start irradiation: 9 ± 1 hits/s/pix plateau: 16 ± 2 hits/s/pix Plateau: Accuracy: 4.5 % # > 3σ : 6%

  14. Bias Scan TDet = 2.5K Under Irradiation: Operating Ge:Ga detectors at Ubias < 160mV

  15. Ionizing Radiation Tests • Preliminary Results: • Measurements w/o irradiation are highly reproducible • 137Cs allows simulations of radiation environment at L2 • Effective technique for CR rejection: Sigma clipping with robust estimator (e.g., HL) • So far: • Operating Ge:Ga detectors at a lower bias voltage < 160mV • Long term knowledge of  better 5% • Good curing by IR flash (~ 10-12 W/pixel)

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