Max-Planck-Institut für Astronomie Heidelberg PACS SVR 22./23. June 2006 MPE Garching J. Stegmaier, U. Grözinger, D. Lemke, O. Krause, H. Dannerbauer, T. Henning, R. Hofferbert, U. Klaas, J. Schreiber Ge:Ga Detector Arrays PACS SVR phase 1, MPE Garching June 2006

PACS SVR, MPE Ge:Ga Detector Arrays 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 -BB-temperatures -Detector temperatures -Dark measurments FM-LS Tests MPIA Test Facility f-ratio as in PACS IR-flux attenuation: ~ 2.5 · 10 -6

PACS SVR, MPE Ge:Ga Detector Arrays FM LS-Sevenpacks FM-LS during integration into MPIA test cryostat FM module Warm functional test Cold performance test comments LS 1 2 hot pixels LS non-confirming modules (dummy channel) LS 2_2 1 open pixel LS non confirming module (output frame not stable, low V SS current) LS modules with weak pixels LS 5 1 module under higher stress LS 6 1 open (dummy) channel 2 modules under higher stress

PACS SVR, MPE Ge:Ga Detector Arrays FM LS-Sevenpacks FM module Warm functional test Cold performance test comments LS 1 2 hot pixels LS non confirming modules (dummy channel) LS 2_2 1 open pixel LS non confirming module (output frame not stable, low V SS current) LS modules with weak pixels LS 5 1 module under higher stress LS 6 1 open (dummy) channel 2 modules under higher stress channel #14 channel #7 FM 122 (LS 2_2) FM 115 (LS 1)

PACS SVR, MPE Ge:Ga Detector Arrays Responsivity NEP Responsivity / NEP Responsivity: 7.4 A/W ± 1.7 A/W NEP: 1.18 · A/W ± 4.6 · A/W U Bias = 200mV, T Det = 2.5K FM 126, FM 135, FM 136: higher stress (mounting screw of the test housing pressed the module)  modules OK LS 1LS 2_2LS 5LS 6

PACS SVR, MPE Ge:Ga Detector Arrays Responsivity - Homogenity LS 1 (FM 120, 118, 115, 114, 110, 108, 107)LS 2_2 (FM 122, 115, 121, 116, 113, 112, 111) LS 5 (FM 132, 131, 123, 128, 126, 125, 119)LS 6 (FM 130, 137, 136, 135, 134, 133) Spiking pixel FM 115 ch. #14 FM 122 ch. #7 open Spiking pixel FM 114 ch. #4 U Bias = 200mV, T Det = 2.5K, C int = 240 pF higher stress on FM 126 higher stress on FM 135 and FM 136

PACS SVR, MPE Ge:Ga Detector Arrays Responsivity - Bias Scan LS 1 (FM 120, 118, 115, 114, 110, 108, 107)LS 2_2 (FM 122, 115, 121, 116, 113, 112, 111) LS 5 (FM 132, 131, 123, 128, 126, 125, 119)LS 6 (FM 130, 137, 136, 135, 134, 133) w/o spiking and open pixels T Det = 2.5K FM 126 (LS 5), FM 135 (LS 6), FM 136 (LS 6): higher stress caused by mounting in the test housing

PACS SVR, MPE Ge:Ga Detector Arrays NEP - Bias Scan LS 1 (FM 120, 118, 115, 114, 110, 108, 107)LS 2_2 (FM 122, 115, 121, 116, 113, 112, 111) LS 5 (FM 132, 131, 123, 128, 126, 125, 119)LS 6 (FM 130, 137, 136, 135, 134, 133) T Det = 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

PACS SVR, MPE Ge:Ga Detector Arrays Dark Current [e - /s] U Bias = 200mV, T Det = 2.5K LS1 LS 5 Mean: 3550 e - /s ± 600 e - /s Requirements: CD ≤ 5*10 4 e - /s

PACS SVR, MPE Ge:Ga Detector Arrays Higher stress on 3 FMs  smaller band gap LS 5 LS Band gap [meV] Band Gap FM 120, Ch 2 (LS 1) photon flux on detector Thermal excitation: I dark ~ exp (-E/kT Det )

PACS SVR, MPE Ge:Ga Detector Arrays 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: U Bias, T Det - 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 · 10 5 ions/cm²/s; E p ≈ 100 MeV, E ions ≈ 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 Ionizing Radiation and Curing No stable operation of Ge:Ga detectors

PACS SVR, MPE Ge:Ga Detector Arrays Ionizing Radiation Tests Conditions –Simulated PACS operation conditions –Realistic FIR background: 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% 137 Cs detector irradiation –L2 radiation environment: 137 Cs source (E γ = MeV) –Hit rate (> 3 σ ): ~16/s/pix Long term measurments with 137 Cs Generic charge ramp Radioactive 137 Cs source

PACS SVR, MPE Ge:Ga Detector Arrays Deglitching Method Glitch detection & deglitching: -sigma clipping applied to pairwise differences (values >3 σ ) Skewed distributions: -Robust estimator, e.g., Hodge-Lehmann estimator: μ = median (X i +X j )/2 with 1 ≤ i ≤ j ≤ n Glitches  skewed distribution

PACS SVR, MPE Ge:Ga Detector Arrays NEP and Responsivity Glitch rate: Start irradiation: 9 ± 1 hits/s/pix plateau: 16 ± 2 hits/s/pix Plateau: Accuracy: 4.5 % # > 3σ : 6% 5h U Bias = 160mV, T Det = 2.5K

PACS SVR, MPE Ge:Ga Detector Arrays Bias Scan T Det = 2.5K Under Irradiation: Operating Ge:Ga detectors at U bias < 160mV

PACS SVR, MPE Ge:Ga Detector Arrays Ionizing Radiation Tests Preliminary Results: Measurements w/o irradiation are highly reproducible 137 Cs 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 (~ W/pixel)

PACS SVR, MPE Ge:Ga Detector Arrays Backup slides

PACS SVR, MPE Ge:Ga Detector Arrays Curing by IR flash IR flash ~ W/pixel, 30 s U Bias = 160mV, T Det = 2.5K

PACS SVR, MPE Ge:Ga Detector Arrays Simulation of a Solar Flare Event high γ flux, 1min hit rate > 3σ: 56/pix/s U Bias = 160mV, T Det = 2.5K