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Max-Planck-Institut für AstronomieHeidelberg
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 22.-23. June 2006
PACS SVR, MPE22.-23.06.2006 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, Cint, tint
- Using different - Filter combinations- BB-temperatures- Detector temperatures
- Dark measurments
FM-LS Tests
MPIA Test Facility
f-ratio as in PACSIR-flux attenuation: ~ 2.5 · 10-6
PACS SVR, MPE22.-23.06.2006 Ge:Ga Detector Arrays
FM LS-Sevenpacks
FM-LS during integration into
MPIA test cryostat
FMmodul
e
Warm functional test
Cold performanc
e testcomments
LS 1 2 hot pixels
LS 2 - 2 non-confirming modules (dummy channel)
LS 2_2 1 open pixel
LS 3 - 1 non confirming module(output frame not stable, low VSS current)
LS 4 - 2 modules with weak pixels
LS 5 1 module under higher stress
LS 6 1 open (dummy) channel 2 modules under higher stress
PACS SVR, MPE22.-23.06.2006 Ge:Ga Detector Arrays
FM LS-Sevenpacks
FMmodul
e
Warm functional test
Cold performanc
e testcomments
LS 1 2 hot pixels
LS 2 - 2 non confirming modules (dummy channel)
LS 2_2 1 open pixel
LS 3 - 1 non confirming module(output frame not stable, low VSS current)
LS 4 - 2 modules with weak pixels
LS 5 1 module under higher stress
LS 6 1 open (dummy) channel 2 modules under higher stress
0 2 4 6 8 10 12 14 16 18 202,5
3,0
3,5
4,0
4,5
5,0
5,5
UBias
= 200mV, Cint
= 0
UBias
= 200mV, Cint
= 1FM 115
Ou
tpu
t Vo
ltag
e [V
]
CRE-Channel
channel #14
0 2 4 6 8 10 12 14 16 18 202,5
3,0
3,5
4,0
4,5
5,0
5,5
UBias
= 200mV, Cint
= 0
UBias
= 200mV, Cint
= 1
FM 122
Out
put V
olta
ge [V
]
CRE-Channel
channel #7
FM 122 (LS 2_2)
FM 115 (LS 1)
PACS SVR, MPE22.-23.06.2006 Ge:Ga Detector Arrays
ResponsivityNEP
Responsivity / NEP
Responsivity: 7.4 A/W ± 1.7 A/WNEP: 1.18 · 10-16 A/W ± 4.6 · 10-17 A/W
UBias = 200mV, TDet = 2.5K
FM 126, FM 135, FM 136:higher stress (mounting screw of
the test housing pressed the module) modules OK
LS 1 LS 2_2 LS 5 LS 6
PACS SVR, MPE22.-23.06.2006 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)
0 2 4 6 8 10 12 14 16 180
5
10
15
20 200mV, Cint
= 1
Re
spo
nsi
vity
[A/W
]
channel
FM120 FM118 FM115 FM114 FM110 FM108 FM107
0 2 4 6 8 10 12 14 16 180
5
10
15
20 200mV, Cint
= 1
Re
spo
nsi
vity
[A/W
]
channel
FM122 FM115 FM121 FM116 FM113 FM112 FM111
Spiking pixel FM 115 ch. #14
FM 122 ch. #7 open
0 2 4 6 8 10 12 14 16 180
5
10
15
20
25
30
UBias
= 200mV, Cint
= 1
Re
sp
on
siv
ity [
A/W
]
Channel
FM132 FM131 FM123 FM128 FM126 FM125 FM119
0 2 4 6 8 10 12 14 16 180
5
10
15
20U
Bias = 200mV, C
int = 1
Re
sp
on
siv
ity [A
/W]
Channel
FM130 FM137 FM136 FM135 FM134 FM133
Spiking pixel FM 114 ch. #4
UBias = 200mV, TDet = 2.5K, Cint = 240 pF
higher stress on FM 126
higher stress on FM 135 and FM 136
PACS SVR, MPE22.-23.06.2006 Ge:Ga Detector Arrays
Responsivity - Bias Scan
0 50 100 150 200 250 3000
5
10
15
20
25 Bias Scan, Cint
= 1
Re
spo
nsi
vity
[A/W
]
bias voltage [mV]
FM120 FM118 FM115 FM114 FM110 FM108 FM107
0 50 100 150 200 250 3000
5
10
15
20
25C
int = 1
Res
pons
ivity
[A/W
]
UBias
[mV]
FM122 FM115 FM121 FM116 FM113 FM112 FM111
0 50 100 150 200 250 3000
5
10
15
20
25C
int = 1
Re
spo
nsi
vity
[A
/W]
UBias
[mV]
FM132 FM131 FM123 FM128 FM126 FM125 FM119
0 50 100 150 200 250 3000
5
10
15
20
25C
int = 1
Re
sp
on
siv
ity [A
/W]
UBias
[mV]
FM130 FM137 FM136 FM135 FM134 FM133
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 andopen pixels
TDet = 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, MPE22.-23.06.2006 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)
TDet = 2.5K
0 50 100 150 200 250 300
0
1x10-16
2x10-16
3x10-16
4x10-16
5x10-16
6x10-16 Bias Scan, Cint
= 1
NE
P [W
/Hz1/
2 ]
bias voltage [mV]
FM120 FM118 FM115 FM114 FM110 FM108 FM107
0 50 100 150 200 250 300
0
1x10-16
2x10-16
3x10-16
4x10-16
5x10-16
6x10-16
Cint
= 1
NE
P
UBias
[mV]
FM122 FM115 FM121 FM116 FM113 FM112 FM111
0 50 100 150 200 250 300
0
1x10-16
2x10-16
3x10-16
4x10-16
5x10-16
6x10-16
Cint
= 1
NE
P
UBias
[mV]
FM132 FM131 FM123 FM128 FM126 FM125 FM119
0 50 100 150 200 250 300
0
1x10-16
2x10-16
3x10-16
4x10-16
5x10-16
6x10-16
Cint
= 1
NE
P
UBias
[mV]
FM130 FM137 FM136 FM135 FM134 FM133
w/o spiking andopen pixels
FM 126 (LS 5),FM 135 (LS 6),FM 136 (LS 6):higher stress
caused by mounting in the
test housing
PACS SVR, MPE22.-23.06.2006 Ge:Ga Detector Arrays
Dark Current [e-/s]UBias = 200mV, TDet = 2.5K
LS1
LS 1
LS 5
Mean: 3550 e-/s ± 600 e-/s
Requirements: CD ≤ 5*104 e-/s
PACS SVR, MPE22.-23.06.2006 Ge:Ga Detector Arrays
Higher stress on 3 FMs smaller band gap
LS 5 LS 6
1615141312111098765432
Band gap [meV]
Band Gap
0,25 0,30 0,35 0,40 0,45 0,50e-36
e-35
e-34
e-33
e-32
e-31
e-30
e-29
e-28
e-27
e-26
e-25
e-24
e-23
e-22
dark
cur
rent
[A]
1/TDet
[1/K]
ch2
0,25 0,30 0,35e-36
e-35
e-34
e-33
e-32
e-31
e-30
e-29
e-28
e-27
e-26
e-25
e-24
e-23
e-22
Parameter Wert Fehler------------------------------------------------------------A 2,46252 0,49093B -103,80926 1,6843------------------------------------------------------------
R SD N P-------------------------------------------------------------0,99934 0,14967 7 <0.0001------------------------------------------------------------
da
rk c
urr
en
t [A
]
1/T [1/K]
ch2 lin. fit
FM 120, Ch 2(LS 1)
photon flux on detector
Thermal excitation: Idark ~ exp (-E/kTDet)
PACS SVR, MPE22.-23.06.2006 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: 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
Ionizing Radiation and Curing
No stable operation of Ge:Ga detectors
PACS SVR, MPE22.-23.06.2006 Ge:Ga Detector Arrays
Ionizing Radiation Tests
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
Long term measurments with 137Cs
Generic charge ramp
Radioactive 137Cs source
PACS SVR, MPE22.-23.06.2006 Ge:Ga Detector Arrays
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
PACS SVR, MPE22.-23.06.2006 Ge:Ga Detector Arrays
NEP and Responsivity
Glitch rate: Start irradiation: 9 ± 1 hits/s/pixplateau: 16 ± 2 hits/s/pix
Plateau: Accuracy: 4.5 %# > 3σ : 6%
5h
UBias = 160mV, TDet = 2.5K
PACS SVR, MPE22.-23.06.2006 Ge:Ga Detector Arrays
Bias ScanTDet = 2.5K
Under Irradiation: Operating Ge:Ga detectors
at Ubias < 160mV
PACS SVR, MPE22.-23.06.2006 Ge:Ga Detector Arrays
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)