Spectrometer Performance

1
Spectrometer Performance

• H. Feuchtgruber, T. Müller,
• A. Poglitsch

2
Overview
!! Mostly draft results, no final reports yet !!

• Thermal behaviour
• Spectral coverage
• Wavelength calibration
• Spectral resolution and
• instrumental profile
• Sensitivity NEP
• Relative spectral response
• Leakage and Ghosts
• Photoconductor Arrays

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

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

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

6
Spectral coverage

• Available grating range 44.62 degrees
• working range 43.1 degrees (low grating
  output)
• order measured specification
• 45000 1050000
• n3 73.2µm 34.8 µm 72µm - 56µm
• n2 109.8µm 52.2µm 105µm -
  72µm
• n1 219.6µm 104.3µm 210µm - 105µm
• Nominal 72-56µm band can be measured in grating
  order 2 and 3

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

?? ???? gLHe117.175 n1,2,3 pix1..16
??0-gratpos/dgrat with dgrat23301steps/? So
far just ?0 (FM) ?0 (CQM) 3.78? (no
detailed analysis and no module
dependence yet !)
8
Wavelength Calibration (2)
Laser setup in front of cryostat
Laser 70.512 µm Grating order 3 Filter A
Pixel11,7
9
Wavelength Calibration (3)
Laser 70.512 µm Grating order 3 Filter A
Pixel11,7
Measured Gaussfit
Signals beyond cut level in white
10
Wavelength Calibration (3)
Red spectrometer, grating order 1,single
pixel Vapor cell p 8.5 mbar
Measured Model
Measured Model
Blue spectrometer, Grating order 3, single
pixel Vapor cell p 20-28mbar
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

12
Sensitivity System NEP Map

• 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

??88µm TBB30K Ppix3.96e-14W
??194µm TBB22.5K Ppix1.15e-14W
blue
red
13
Relative Spectral Response

• 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

57µm
105µm
72µm
BB_at_12K Cint140fF
n2
n2
BB_at_30K Cint230fF
n1
leakage
n3
Not yet measured with n1
14
Leakage and Ghosts (1)
15
Leakage and Ghosts (2)
16
l-l Plot of Ghost Responses in 1st Order
0 t h o r d e r
Ghost 1st order 3pass
From SVR 1
Ghost 1st order 2pass
Normal Signal
Ghost 2nd order 2pass
Leak 2nd order
17
l-l Plot of Ghosts, 1st Order, with Baffles
From SVR 1
Ghost 1st order 2pass
Normal Signal
Ghost 2nd order 2pass
Leak 2nd order
18
Leakage and Ghosts (3)
CQM ghosts
clean FM

• Successful baffling
• implemented

19
Leakage and Ghosts (4)

• 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

20
Photoconductor Arrays (1)

• PACS-ME-NCR-236 2 pixels low response

• PACS-ME-NCR-237 crosstalk in supply group 2

21
Photoconductor Array (2)

• PACS-ME-NCR-237
• crosstalk in supply
• group 2
• (few x 100mV/s up
• to several V/s)
• Crosstalk is also
• present in supply
• group 1, however
• much less
• (few x 10mV/s)

Dummy resistor !
Measured Model