PACS

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PACS

• Test Cryostat,
• OGSE and MGSE

Gerd Jakob MPE
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Test Equipment and OGSE Overview
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PACS test cryostat specifications

• Two liquid helium reservoirs 70l for 4.2K and
  13l for 1.7K level
• 90l liquid nitrogen for thermal shielding
• Optical bench diameter 1060mm, covered by 4.2K
  thermal shield with 900mm available height for
  PACS FPU test optics
• Hold time of each temperature level 48 hours
  with full PACS operation (goal)
• Specified mechanical, optical and electrical
  interfaces to PACS FPU and test equipment
• 2 FIR windows for calibration sources input and
  for optical alignment checks
• 2 window shutter/filter mechanisms at 77K shield
  
• Cryogenic filters at 77K and 4.2K shields to
  provide predicted Herschel telescope background
• Representative cryogenic harness with 1100 wires
  227 shields for FPU, 124 wires 20 shields
  for cryostat and test equipment
• Specific mounting rack for different cryostat
  operation positions, e.g. 30 tilt for cooler
  recycling 90 tilt for shield mounting and
  cryostat transport.
• Provide clean instrument environment, payload
  integration in cleanroom class 1000

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Test cryostat status

• Cryostat built at Cryovac GmbHMPEs design
  specifications fulfilled
• Cryo harness built, integrated with cryostat and
  tested by MPE in cw31/03
• Several cryo tests performed-hold time 77K
  level 57h-hold time pumped 1.7K level gt60h,
  lowest temperature 1.4K-hold time 4.2K level
  56h, but only without 4.2K-shield!
• Cryostat failed last acceptance test with
  4.2K-shield in cw 42/03
• Optical bench temperature too high (6,3K) 4.2K
  LHe-tank hold time 24 hours (48h goal) shield
  temp. 25K
• Heat dissipation on 4.2K level 1W higher than
  without 4.2K-shield
• Investigations on a presumable thermal link
  ongoing modifications and amendments in progress
• Delivery to MPE for optical alignment of test
  optics with STM after successful acceptance test,
  end Nov.03

FPU integration
evacuation
operation with 20tilt
optical bench dia.1060mm
cryostat transportation
PACS cryostat in different positions Overall
height 2400mm, Mounting rack 1400mm x 2100mm
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Test optics and Herschel telescope simulator
specifications

• Herschel telescope simulator test optics to be
  integrated with test cryostat, aligned to PACS
  FPU and operated at 4.2K
• Image quality goal 3µm wave front error (?PACS),
  field distortion less than 1 blue photometer
  detector pixel for the total chopped PACS field
  of view
• Design of a complex opto-mechanical imaging and
  baffling system, internal and external
  calibration sources
• Provision of FIR background based on Herschel
  telescope temperature of 70K-90K
• 3 cryogenic mechanisms for different internal and
  external calibration source selection
• 2 internal calibrated cryogenic blackbodies
• TUFIR wavelength calibrator in combination with
  an internal integrating sphere
• TUFIR input in combination with a point source
  simulator
• External blackbody, extended or with point source
  simulator
• Water vapor absorption cell for initial
  wavelength calibration

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Test optics schematic and design
3D design of test optics and Herschel telescope
simulator
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Test optics status

• Herschel telescope simulator test optics
  designed, built and assembled at MPE
• Rigid tripod structure with optics base plate and
  stray light reducing housing to be integrated
  with test cryostat
• Interfaces to cryostat, calibration sources and
  test equipment complete
• Test optics harness parts under final assembly
• Temperature sensors, positions sensors and read
  outs implemented
• Test equipment available
• Integration of 10 mirrors, integrating sphere,
  mechanisms and optical alignment is ongoing
• Optical alignment accuracy goal of test optics to
  PACS FPU within /- 1 arcmin by means of a
  minimum of 3 cryogenic tests to be performed in
  test cryostat

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Test optics status ctd.

• FIR black coating according KT72-process applied
  to test optics housing and components
• 7 temperature sensors on motors, pupil P1,
  mirrors, structure
• Thermal I/F and cooling straps for PACS FPU
  manufactured and available
• The MPE developed cryo torquer motor was
  successfully operated at 4.2K
• Motor life time test with gear box successful at
  4.2K
• Chopper wheel performance test at 4.2K to be
  repeated with reduced friction of angular ball
  bearing in order to achieve the goal for chopping
  frequencies up to 2Hz
• Flip mirror mechanisms to be tested at 4.2K in
  combination with motor/gear
• Alignment and integration is performed in
  cleanroom class 1000

Test optics and PACS FPU STM
Cryo flip mirror Mechanism1 assembly with gear
box and cryo torquer motor
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Internal calibration source cryogenic blackbody

• Design and manufacturing of 2 identical cryogenic
  blackbodies for absolute flux calibration and
  background devices selected or chopped by test
  optics chopper wheel
• 18mm opening of cavity adapted to test optics
  pupils P4 and P5
• FIR coating acc. KT72-process applied
• Operational temperature range 4.2K 80K
• Typical temperatures of 10K 60K can be
  stabilized within 35 minutes by a heaterpower of
  100mW with controller LS370
• Power dissipation typically 12.5mW at 30K and
  35mW at 50K
• Absolute temperature accuracy /-20mK at 20K and
  /-35mK at 50K with integrated calibrated
  temperature sensor CX-1070 and contr. LS370
• Thermal stability requirement of lt/-1.25mK at
  30K and lt/-5mK at 50K feasible
• Status final assembly ongoing, test equipment
  available, tests at cryogenic temperature to be
  performed during test optics alignment checks

MPE design of a cryogenic blackbody
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External calibration source TUFIR and I/F

• TUFIR (tunable high resolution coherent FIR
  radiation source) used for final wavelength
  calibration and spectral ghost detection
• I/F implemented in test optics designinput
  through cryostat windows 1 and 2 selected by
  cryo-mechanisms
• Window 1-4.2K-aperture for 300K background
  reduction-f/4.4 light cone for TUFIR beam
  collection-integrating sphere dia. 80mm for
  homogenous illumination of pupil P3 and for
  filling the telescope simulator beam-background
  heater to simulate Herschel telescope
  temperatures of 70K-90K
• Window 2-point source mask in combination with
  TUFIR located in external focus F2 PACS chopped
  field of view completely covered-Herschel
  telescope background simulated by attenuation
  filter sets on different temperature levels
• Status test optics I/F available, TUFIR I/F to
  be defined

Test optics with integrating sphere,
4.2K-aperture and background heater for TUFIR
input through cryostat window1
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External calibration source blackbody

• External blackbody in combination with scannable
  point source simulator for point spread function
  and grating alignment investigations
• Design of X/Y translation stage and point source
  simulator finished
• Scanning area covers the complete field of
  external focus F2
• Reproducibility goal 20µm
• Point source simulation pattern to be PC
  controlled and synchronized with PACS data
  read-out
• Calibrated blackbody source and controller
  available, temperature range 300K 750K, maximum
  cavity opening dia. 25mm
• Hot plate alternatively foreseen
• Status manufacturing has been started

Schematic of external blackbody set-up
(above) and 3D design with point source mask on
X/Y translation stage, aligned with cryostat
window2
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External calibration source water vapor source

• Design of a water vapor absorption cell for
  initialwavelength calibration
• 300mm absorption pathlength and typical
  watervapor pressure of10-25mbar provide
  appropriate absorptionlines in the
  PACSwavelength range
• Alternative gas CO foreseen
• Hot plate provides background, temperature range
  300K 600K
• Alignment with external focus F2 at test cryostat
  window 2
• Status final design finished end of Nov.03

schematic of the water vapor source set-up
(above) and 3D design of absorption cell aligned
with cryostat window 2
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Mechanical ground support equipment MGSE
Crane with fine drives installed in MPE
PACS cleanroom class 1000, 07/03
Hoisting device for PACS FPU available, used
for STM integration 06/03
Pumping unit available, containing oil free
vacuum and helium pumps,pressure gauges,gas
flow meters and vacuum assembly 10/03
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Mechanical ground support equipment MGSE ctd.

• PACS FPU class 1000
• transportation container
• with shock absorber,
• shock and tilt indicators,
• venting ports
• design complete,
• manufacturing starts
• 11/03