PACS SVR 2 18 Jan 2007 FM ILT: Spectrometer1 Spectrometer Performance H. Feuchtgruber, T. Müller,...
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Transcript of PACS SVR 2 18 Jan 2007 FM ILT: Spectrometer1 Spectrometer Performance H. Feuchtgruber, T. Müller,...
FM ILT: Spectrometer
PACS SVR 2 18 Jan 2007
1
Spectrometer Performance
H. Feuchtgruber, T. Müller,A. Poglitsch
FM ILT: Spectrometer
PACS SVR 2 18 Jan 2007
2
Overview
• Thermal behaviour • Spectral coverage• Wavelength calibration• Spectral resolution and instrumental profile• Sensitivity NEP• Relative spectral response• Leakage and Ghosts• Photoconductor Arrays
!! Mostly draft results, no final reports yet !!
FM ILT: Spectrometer
PACS SVR 2 18 Jan 2007
3
Boundary Conditions
• Limited Time
• Apply best guess values for detector biases and heater
• Measurements have been carried out in few flux regimes
with mostly smallest capacitor.
• Optics misaligment and the significant amount of time
spent to investigate it
• Blue and Red spectrometer had to be operated separately
FM ILT: Spectrometer
PACS SVR 2 18 Jan 2007
4
Thermal Behaviour (1)• Results from CUS Observation: “SPEC_thermal_OBS”
• Test of all spectroscopy components within one single measurement• Illustrate the temperature behaviour of PACS during typical spectrometer and photometer operations• Determine FPU temperature upper limits during heat dissipation• Measure temperature transients in the individual sub-units• Assess overall thermal conductances and heat fluxes• Verify proper thermal strapping to cryostat thermal reservoirs• Identify possible problem areas
FM ILT: Spectrometer
PACS SVR 2 18 Jan 2007
5
Thermal Behaviour (2)• Results from CUS Observation: “SPEC_thermal_OBS”
• Test of all spectroscopy components within one single measurement• Illustrate the temperature behaviour of PACS during typical spectrometer and photometer operations• Determine FPU temperature upper limits during heat dissipation• Measure temperature transients in the individual sub-units• Assess overall thermal conductances and heat fluxes• Verify proper thermal strapping to cryostat thermal reservoirs• Identify possible problem areas
FM ILT: Spectrometer
PACS SVR 2 18 Jan 2007
6
Spectral coverage
Available grating range = 44.62 degrees working range = 43.1 degrees (low grating output)
order “measured” specification [45000 – 1050000]
n=3 73.2µm – 34.8 µm 72µm - 56µm n=2 109.8µm – 52.2µm* 105µm - 72µm n=1 219.6µm – 104.3µm 210µm - 105µm
* Nominal 72-56µm band can be measured in grating order 2 and 3
FM ILT: Spectrometer
PACS SVR 2 18 Jan 2007
7
Wavelength Calibration (1) Sources and available measurements:
- FIR-Methanol-Laser provided by LENS Tested spectral lines: 70.512, 77.406, 96.522, 118.834 µm - OGSE vapor cell Tested spectral range scans: 58-60µm and 132-145µm
=; =; gLHe=117.175; n=[1,2,3] ; pix=[1..16]
=0-gratpos/dgrat with dgrat=23301[steps/]
So far just: 0 (FM) = 0 (CQM) + 3.78 (no detailed analysis and no
module dependence yet !)
FM ILT: Spectrometer
PACS SVR 2 18 Jan 2007
8
Wavelength Calibration (2)
Laser: 70.512 µmGrating order = 3Filter A
Pixel:11,7
Laser setup in front of cryostat
FM ILT: Spectrometer
PACS SVR 2 18 Jan 2007
9
Wavelength Calibration (3)
Laser: 70.512 µmGrating order = 3Filter A
Pixel:11,7
Signals beyond cut level in white
MeasuredGaussfit
FM ILT: Spectrometer
PACS SVR 2 18 Jan 2007
10
Wavelength Calibration (3)
Blue spectrometer,Grating order 3, single pixelVapor cell p = 20-28mbar
Red spectrometer,grating order 1,single pixelVapor cell p = 8.5 mbar
MeasuredModel
MeasuredModel
FM ILT: Spectrometer
PACS SVR 2 18 Jan 2007
11
Spectral Resolution & Instrumental Profile
• 3 laser lines confirm predictions from design on central pixels • Instrumental profile is “gaussian” at least down to a residue at 3% level
FM ILT: Spectrometer
PACS SVR 2 18 Jan 2007
12
• Staring measurement at fixed grating position and given OGSE BB input flux has been analyzed (no dark current and straylight considerations yet !):
• CRE setting: Nominal bias, smallest capacitor, 64 readouts per ramp
Sensitivity: System NEP Map
blue red
88µm; TBB=30K; Ppix=3.96e-14W 194µm; TBB=22.5K; Ppix=1.15e-14W
FM ILT: Spectrometer
PACS SVR 2 18 Jan 2007
13
Relative Spectral Response
n=3
n=2
n=2
n=1
BB@12KCint=140fF
BB@30KCint=230fF
• Draft analysis of different spectral scans on OGSE BB at 30K.
• Single pixel only
• Probably saturation effects for red detector at 30K
• Leakage effects seen at longwave band edges
Not yet measured with n=1
57µm 105µm72µm
leakage
FM ILT: Spectrometer
PACS SVR 2 18 Jan 2007
16
- Plot of Ghost Responses in 1st Order
0th
order
Leak 2nd order
Ghost 2nd order 2pass
Ghost 1st order 2passNormal Signal
Ghost 1st order 3pass
From
SV
R 1
FM ILT: Spectrometer
PACS SVR 2 18 Jan 2007
17
- Plot of Ghosts, 1st Order, with Baffles
Leak 2nd orderGhost 2nd order 2pass
Ghost 1st order 2passNormal Signal
From
SV
R 1
FM ILT: Spectrometer
PACS SVR 2 18 Jan 2007
18
Leakage and Ghosts (3)
CQM “ghosts”
“clean” FM
• Successful baffling implemented
FM ILT: Spectrometer
PACS SVR 2 18 Jan 2007
19
- Leakage effects are within expectations from order sorting filter performances
- ECR-011, baffle modifications were successful in removing the sharp spectral ghosts seen during CQM
- Tests with the strongest laser line at 118.834 µm did not show leaking features in the blue bands
- No ghosts seen during all laser tests
Leakage and Ghosts (4)
FM ILT: Spectrometer
PACS SVR 2 18 Jan 2007
20
Photoconductor Arrays (1)
• PACS-ME-NCR-236: “2 pixels low response”
• PACS-ME-NCR-237: “crosstalk in supply group 2”