PACS IBDR 27/28 Feb 2002 PACS Photometer1 PACS PHOTOMETER J.L Auguères L.Rodriguez CEA/DSM/DAPNIA...

PACS Photometer 1

PACS IBDR 27/28 Feb 2002

PACS PHOTOMETER

J.L AuguèresL.Rodriguez

CEA/DSM/DAPNIAService d’Astrophysique

PACS Photometer 2


Development Status (1)

• Bolometers at LETI:– CQM run available (DC+RC & 2K buffers).

• BFPs:– Design finalised, Kevlar suspension validated.– Mounting tools:

• Design, detailed design, fabrication completed.• Mounting procedure validated (some tuning from experience)

– Test BFPs (used for bolometer test & selection):• Detailed design finalised.• A few sets available, additional sets under fabrication.• 1st (blue type) BFP integrated and under test at LETI.

– CQM Mechanic:• Design finalised, detailed design almost completed.• Optical filters: specified, design started but requires validation.

PACS Photometer 3


Main differences between SPIRE & PACS Bolometer arrays

VrRc

Rb

MU

X

address

300 mK 2 K

SPIRE arrays Problems•MUX function perturb the high impedance bolometer bridge.•MOS 1/f noise dominant.•Correlated noise show sensitivity to RF.•MUX only 8->1

PACS Photometer 4


Main differences between SPIRE & PACS Bolometer arrays

PACS arrays Solutions•Cold readout circuit under the pixel reflector: low capacitance.•MUX now 16->1 •MUX function after the readout.•Large readout MOS to reduce 1/f noise.•Blind pixels to remove all perturbations.•We added 2 impedance adaptation stages:-BU @ 2K,-BOLA @ 130K. To cope with thermal budgets

MU

XVr

Rc

Rb

300 mK 2 K

Buffer Unit

addressVrRc

Rbhe

ate

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BO

LA

heater

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BOLOMETER FOCAL PLANE

The detector unit: A 16 x 16 pixel array+ two rows of blind pixels…

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…attached by the 0.3K-2K ribbon cableto the buffer unit…

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8 arrays butted on the common carrier @ 300mK cooled by the strap…

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…under the 300 mK filter.The Buffer Units are assembled by 4

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The 0.3 K stage suspended by Kevlarwires on the 2K structure…

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Two half shells close the bolometer assembly…

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...and a cone with air gap filter achieve the stray light rejection.

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• PhFPU:– I/Fs

• with PACS FPU (almost) validated.• S/C I/F: Connectors: OK, 2K straps: Outstanding issues.

– 4K & 2K Structures.• Design completed.• Detailed design started (goal end of Feb. 02).• Call for Tender process started (SMs & CQM Models).

– Cooler:• Design, detailed design of STM, CQM, FM & FS

completed.• Manufacturing of 2 STM + 2 CQM parts completed.• Mounting ongoing.

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PHOTOMETER ASSEMBLY

The 2K structure holds the Blue and Red BFPs…

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PHOTOMETER ASSEMBLY

…is insulated from the 4 K stage by stainless steel tubes…

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PHOTOMETER ASSEMBLY

The 4 K structure is mechanically interfaced with the remaining partof the instrument

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PHOTOMETER ASSEMBLY

The cooler is mounted on the bottom,the RF filter boxes are bolted on the rear side.

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PHOTOMETER ASSEMBLY

The cooler straps are finally located.

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PHOTOMETER ASSEMBLY

A black painted metal blanketachieve the stray light rejection.

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BUDGETS

Mass Budget

Blue BFP = 630 gRed BFP = 520 g2 K Struc. = 550 g4 K Struc. = 2720 gCryocooler = 1700 gRF Filters = 1260 g

Total = 7380 g

Thermal Budget

2 K Stage = 5 mWElect. = 3.3 mWCond. = 1.7 mW

4 K stage = negative

0.3 K Stage = 12 µW

Cryocooler = 800 J/cycle

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• Cryogenic Test Facilities:– BFP Test facilities: Designed to test BFP individually, they

consist in: 1 cryostat equipped with 0.3K cooler and optical bench + 1 acquisition system.

• 2 identical facilities installed respectively at Saclay and LETI.

• Currently they are equipped with simplified optical benches.

– PhFPU Test facility: Designed to test a fully assembled PhFPU, it consists in one cryostat equipped with simplified optical bench.

• Specified.• Detailed drawing of cryostat almost completed.

– Irradiation test facility:• Cryostat ordered at IRlab.

– FTS spectrometer test facility:• Manufactured. Currently in acceptance tests.

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BFP & PhFPUTest facilities

LH

eL

N2

LH

eL

N2

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TESTS PROGRAM AND COLD FACILITIES

BFP test facility

PhFPU test facility

Irradiation test cryostat

Spectrometer

Filters measurements

check none none yes

Spectral responsivity none none none yes

Responsivityyes check yes check

Noise performances yes yes yes yes

Gamma ray total dose no no yes no

Protons and heavy Ions no no yes no

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TESTS RESULTS

Tests on bolometer arrays started only two weeks ago after unexpectedDelays on ribbon cables delivery.We started by functional tests: Pixel multiplexing, electronic chopping,blind pixel differential mode including tests on background compensationHeater.

16 pixels

Chopper on

Multiplexing imposes to drive signals of 40 frames/s x 16 pixels x 2 (chop) =1280Hz

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TESTS RESULTS: differential mode

Without heating the blindpixels

Heater on300 mV on heaters

350 mV on heaters

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BOLA is currently a « relay »: it adapts the output impedance of the BU to cope with the expected cablecapacitance in a given 2 K power consumption.

BOLA ISSUE

MU

X

VrRc

Rb

300 mK 2 K

Buffer Unit

addressVrRc

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LA

Warmelectronics

14 meters ?!

BOLA is still today the baseline!

h ea te r

PACS Photometer 27


Bandwidth measurementsin function of dissipated Power and output capacitance

100 1000 10000 Hz

100 1000

100 1000

Without capacitor

+1 nf

+2.2nf

6 mW2.5 mW

1.25 mW

BOLA ISSUE

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TESTS RESULTS• FUNCTIONNALITY:

– Detector array measured is completely functional.– Responsivity (V/W) is not available because test filters are still

to be measured and mounted.– Evaluation of multiplexing on noise increase currently

explored.– Buffer Unit performances are compliant with noise

specifications.

CONCLUSIONSThe detector system is a complex set up. It is completely

functional. We already notice some minor problems: - diode protection on BU for the 300 mK stage to be removed,- modify geometry of even/odd MOS transistors (threshold

slightly different).

PACS Photometer 29


PhFPU Models (1)• SMs:

– CEA SM:• Consists in flight representative 2K & 4K mechanical structures

equipped with dummy mass models of the BFPs and a Cryocooler SM.

• Goals: Validation of the mechanical concept.

– KT SM:• Consists in a flight representative 2K & 4K mechanical

structure equipped with dummy mass models of the BFPs and of the Cryocooler.

• Validation of: the mechanical I/F with the instrument, the mounting procedure, the mechanical concept.

• SOAM (Structure and Optical Alignment Model)

– Consists in the KT SM refurbished with optical marks.– To be used to perform Warm & Cold Alignment with the

instrument.

PACS Photometer 30


PhFPU Models (2)

• CQM:– Fully representative Flight Model.– Performance restrictions:

• Blue Channel: 8 functional arrays, 2 @ performances.• Red Channel: 2 functional arrays, 1 @ performances.

• FM:– Fully compliant.

• FS:– Spare BFPs & Cryo-cooler.

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AIV & QA

• AIV:– Full PhFPU Models AIV diagram available.– AIV means identified (already available or

development/procurement planned).

• QA:– QA organisation operational at SAp, LETI and SBT

• PA plans, Doc. Management,

– PhFPU QA Documentation:• DML (currently in draft)• DPL (currently in draft)

– Bolometer evaluation:• Evaluation plan available

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PROBLEM AREAS (1)

• Current lack of Bolometer Complete Test results:– Problem:

• The 1st blue BFP has been successfully integrated at LETI . We started measurements in an incomplete test bench, with some minor problems in stray light rejection, and 300 mK operation (new double stage 3He/4He cooler).

– Solution: • The tools needed to measure the performances will be validated and

implemented in the fore coming weeks.• cryogenic issues are under investigation.• additional SAp staff support test at LETI.

• 2K Buffer characteristics:– Problem:

• Encouraging results have been obtained from preliminary tests at LETI and at Sap. Today, uncertainties on the stray capacitance of the wires and allocated 2K power budget prevent to remove BOLA.

– Solution:• BOLA is still the baseline and to remove it, is a system issue (we will have to take

in account the EMI susceptibility).

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PROBLEM AREAS (2)• Optical filters:

– Problem: • filter housing design uneasy due to filter material behaviour.

– Solution:• Asking for samples of filter material to UC for housing

prototyping at SAp.• UC is investigating housing solutions as well (together with

SPIRE opt. filter design).

• Cooler electrical insulation:– Problem:

• Detector insulation from the instrument mechanical ground (today only through the cryo-cooler).

– Solution:• Several solutions under investigation.

PACS Photometer 34


PROBLEM AREAS (3)

• Cold (4K) Vibration Tests:– Problem:

• Cold vibration cannot be carried out at PhFPU level.

– Solution:• Cold Qualification at instrument level.

• Procurement of Ribbon cables:– Problem:

• Provision relies on only one company.

– Solution:• Looking for other sources.

PACS Photometer 35


SCHEDULE

Milestones Date

Blue & red QM, FM, SP + 2 cones + optical baffle delivery to MPE 10/04/2002

Optical filters delivery to SAp 06/05/2002

Blue & red black painted cones delivery from MPE 06/05/2002

SM KT PhFPU delivery to KT 29/07/2002

SM KT PhFPU delivery from MPE for refurbishment 02/09/2002

SOAM PhFPU delivery to MPE 30/09/2002

Cryo-cooler SM delivery from SBT 06/06/2002

PhFPU SM CEA available 18/07/2002

Cryo-cooler CQM delivery from SBT 23/09/2002

PhFPU CQM delivery to MPE 10/03/2003

Cryo-cooler FM delivery from SBT 22/07/2003

FM PhFPU delivery to MPE 23/02/2004

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PACS IBDR 27/28 Feb 2002 PACS Photometer1 PACS PHOTOMETER J.L Auguères L.Rodriguez CEA/DSM/DAPNIA...

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