LSST Camera Cryostat Design & Integration DOE Program Review SLAC June 2006 Rafe H. Schindler...
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Transcript of LSST Camera Cryostat Design & Integration DOE Program Review SLAC June 2006 Rafe H. Schindler...
LSST Camera Cryostat Design & Integration
DOE Program ReviewSLAC
June 2006
Rafe H. SchindlerExperimental Group E - SLAC
DOE Review
June 2006 SLAC
2
Overview
• SLAC Is Responsible for The Major Mechanical Components & The Final Integration & Testing of the LSST Camera:
– RAFTS – BACK END ELECTRONICS – OPTICAL ELEMENTS – CRYOSTAT & FOCAL PLANE– CAMERA BODY MECHANISMS– UTILITIES (Thermal/Vacuum/Contamination)
• Will Discuss The Cryostat Design and SLAC R&D. Then Briefly the Cryostat Assembly Sequence
CRYOSTAT REQUIREMENTS
GRID PROPERTIES
METROLOGY
ASSEMBLY AND TEST
SLAC DELIVERABLES
Integration & Testing of Camera
DOE Review
June 2006 SLAC
3
LSST Cryostat Design, Assembly & Test
REQUIREMENTS COMBINE:
• Mounting of Close-Packed Rafts & Ancillary Sensors Onto GRID -- Maintaining Overall Flatness (~10 um)
• Rapid Sub-m Metrology to Verify Focal Plane Flatness During Assembly
– From 200C -1000C in All Orientations and Through Optics
• Fast XY Actuation of GRID For Tracking– ~100 um Motion at ~10’s Hz
• Dissipation of ~1KW Internal Heat From Electronics & Radiation Thru L3
• Maintaining Thermal Uniformity Across Sensors (0.3 0C) For QE
– Vac Vessel (10-6 Torr) with Large Window
• Control Contamination Onto The Cold FPA
One of the More Challenging Engineering Tasks
DOE Review
June 2006 SLAC
4
Focal Plane Flatness Budget
Sensor Module
5m p-v flatness over entire sensor surface
Raft Assembly
6.5m p-v flatness over entire surfaces of sensors
Focal Plane Assembly
10m p-v flatness over entire surfaces of sensors
(at -100 0C & All Camera Orientations)
Before FPA I&T
A Few Microns For Mechanical Reproducibility, Gravity, and Thermal Distortions
DOE Review
June 2006 SLAC
5
Focal Plane Design Philosophy To Achieve Metrological Goals
Build Precision Into The GRID and the RAFTS In Advance Allowing Fast “Snap Together” Assembly of Focal Plane:
• Make GRID a Thermally & Mechanically Passive Structure
» Use Si Carbide For High Stiffness & Conductivity and Low Thermal Expansion (matched to Al Nitride).
» Isolate It To Minimize Heat Flow & Distortion
< 0.3 m Gravity Sag and <0.2m Sagitta for T~10C
• Make RAFTS Interchangeable Without Further Adjustment
» Use 3-Vee kinematic coupling with sub-m repeatability
» Setup Rafts relative to their kin. mnts on same metrology fixture
» Pre-load GRID & Adjust Kin. Mnt. Balls on GRID To Accept Standard Raft at Ambient Temp.
THIS SHOULD OBVIATE NEED TO FUTHER ADJUST RAFTS DURING I&T
DOE Review
June 2006 SLAC
6
Raft Metrology Fixture Embodies Desired Geometry Needed on Grid
FEE Cage
Raft
Flat and parallel to 3
balls ~100 nm
Raft Metrology
Fixture
Set up detectors coincident to the flat surface of the fixture
Raft and GRID Metrology Strategy To Speed Assembly
AT BNL
DOE Review
June 2006 SLAC
7
Kinematic Mounting Points On The GRID Are Measured & Adjusted to Mimic Raft Metrology Fixture
During Assembly of Focal Plane, a Motion Stage Lifts Raft Onto GRID Kin. Mounting Points From Behind
Thermal Connections Are Made
Metrological Verification Follows Immediately (see following slides)
GRID
GRID
Cold PlateCold Plate
FEE Cage
Raft
Metrology Strategy To Simplify RAFT Assembly onto GRID
AT SLAC….
DOE Review
June 2006 SLAC
8
PRACTICAL REALIZATION OF THIS MOUNTING & METROLOGY SCHEME
BALLS MOUNTED IN GRID
SPRING TO LOAD KINEMATIC MOUNT TO GRID
3-Vee BLOCKS ON RAFT To Mount RAFT to GRID
ADJUSTORS FOR EACH SENSOR’S KIN. MNT. TO AlN RAFT BASE
~12cm
DOE Review
June 2006 SLAC
9
Metrology Techniques Under Evaluation To Verify and Monitor Focal Plane Flatness
• During RAFT Insertion, Flatness Must Be Measured At Ambient Temperature to <<0.5m Across ~65cm Diameter Focal Plane
• When Cryostat Sealed With L3 Must Be Re-Measured Under Vacuum and Cold
– Investigating Non-Contact Laser Displacement Heads as the Primary Tool
• Also Evaluating “In-Situ” Methods To Allow On-Demand Measurements of Changes in the FPA Independent of Camera and Telescope Optics
– Capacitive Edge Sensors (Rafts)
– Diffraction Pattern Generator (Sensor Surface + Rafts)
Allow Fast Diagnostic Verification of FPA Alignment in all Orientations
Non-Contact Laser Displacement Heads For Metrology During Assembly
L3 or WINDOWFOCAL PLANE
OPTICAL REF. FLAT
TRIANGULATION HEAD
LASER TRIANGULATION HEADXY STAGE
SHOWN UPSIDE DOWN
Two Commercial Laser Displacement Heads Mounted in Opposing Directions on XY Stage
One Looks Down at Optical Reference Flat
The Other Looks Up at Focal Plane
Sum of the Two Displacements Removes Most XY Stage Errors
Sub-m Metrology Can Be Done Rapidly By Stitching Smaller Overlapping Areas
DOE Review
June 2006 SLAC
11
Test of Non-Contact Displacement Heads
Sensor Head Sensor Head (LK-G15)(LK-G15)
Sensor Sensor Head Head (LK-G37)(LK-G37)
Optical FlatOptical Flat(reference(reference))
SiC SiC SampleSample
XY Actuation XY Actuation StageStage
Dual Dual ControllerController
12cm
DOE Review
June 2006 SLAC
12
Displacement Sensor Test – Measurement of Polished Silicon Carbide Sample
~0.2 m
RE
SID
UA
LS
DISTANCE ALONG SiC SURFACE
1 m
FORWARD SCAN
BACKWARD SCAN
TEST AT SLAC
DOE Review
June 2006 SLAC
13
Dual sensor XY carriage
Inspection Opt. Table
Assy Opt. Table
Reference surface XY carriage
Camera Focal Plane GRID
Displacement sensors (up & down looking)
Bottom View Shows Partial Population of Focal Plane Array
FPA STITCHING METROLOGY IN PRACTICE
Cryostat Open For Raft Insertion
Take Rapid Measurements After Each Insertion
Multiple Overlapping Samples With Translated Reference Flat Used to Stitch Together the Large Surface
DOE Review
June 2006 SLAC
14
Stitching Metrology Strategy - Simulation
• Fidelity of Measurement Is Trade-Off Between Speed and Completeness
• Simulation Used To Determine Metrology Strategy and Approach:
Monolithic reference (eg granite surface & air bearing) versus localized sampling (smaller ref. flat)
Sample 65cm Diam. Focal Plane With a 20cm Flat
Propagated Error Distributions Compared to Input errors. Four Simulations (2x Different Grid Spacings and 2x Ref. Separations)
Input Error
3mm Spacing
10mm Spacing1.5 Radii Separation
1.2 Radii Separation
DOE Review
June 2006 SLAC
15
STARTUP OF METROLOGY TEST LAB
Polycold dual circuit, recirculating cryo-cooler (1.5 kW cooling capacity @ -120ºC) – just arrived
Vacuum chamber for Cold Metrology (cryogenic thermal control & optical quality inspection window)
TEST CHAMBER
TURBO PUMP
RGA
OPTICAL WINDOW
XY STAGE
TEMP. & PRESS. CNTRLS
DOE Review
June 2006 SLAC
16
In-Situ Metrology: Diffraction Pattern Generator
• Measure FPA Flatness Directly by Centroiding …Ellipses & Measuring Deviations of Known Pattern
• Centroiding Digital Images off Silicon Gives a <<1m on CCD Piston
Laser & Grating
Silicon Wafer
Raft
Grant Awarded at Stanford Nanofabrication Facility To Pursue Grating Fabrication Techniques
• Goal: Shorter spots, increased density & uniform intensity
CCD Imaged Ellipse
In-Situ Metrology: Capacitive Edge Sensors
• Measure Raft Alignment and Piston Directly
SIMPLEST IMPLEMENTATION:
• Conductive Pads Printed on Rafts & GRID
• Digitizing Chip Mounted Near Pads
• Measure Raft Piston and/or XY At Each Corner
SLAC R&D WITH THIS CHIP:
• Full Size Prototype With AD4766 Chip
• Chip Tested In Lab at -1200C
• Noise Limited To ~20 nm For Our Typical Displacements (~200m)
25
DOE Review
June 2006 SLAC
18
Cryostat Assembly Sequence – Designed For Tests & Arbitrary Removal Of Rafts For Repair/Replacement
SiliconCarbide
Grid
Fast Actuators
Cryo Plate
Cool Plate
Feedthrough Flange
Outer Cylinder
INSTALL GRID+ACTUATORS+CRYO PLATES INTO CLEAN & EMPTY BODYINSTALL GRID+ACTUATORS+CRYO PLATES INTO CLEAN & EMPTY BODY
ADD RAFT DUMMY LOADS & TEST FAST ACTUATION SYSTEMADD RAFT DUMMY LOADS & TEST FAST ACTUATION SYSTEM
ADD BLANKOFFS & TEST VACUUM & THERMAL SYSTEMSADD BLANKOFFS & TEST VACUUM & THERMAL SYSTEMS
VERIFY CONTAMINATION SPECIFICATIONS VERIFY CONTAMINATION SPECIFICATIONS
DOE Review
June 2006 SLAC
19
RAFT LOADING SEQUENCE – IN ANY BAY
WORKING UPSIDE DOWN IN CLEAN ROOM:WORKING UPSIDE DOWN IN CLEAN ROOM:
REMOVE DUMMY LOAD IN BAY & INSTALL INSULATIONREMOVE DUMMY LOAD IN BAY & INSTALL INSULATION
ALIGN & SUPPORT RAFT FROM BACKSIDE WITH ROBOTALIGN & SUPPORT RAFT FROM BACKSIDE WITH ROBOT
INSTALL ONTO GRID’S KINEMATIC MOUNTS INSTALL ONTO GRID’S KINEMATIC MOUNTS
DOE Review
June 2006 SLAC
20
WARM METROLOGY
PULL DOWN RAFT ONTO KINEMATIC MOUNTS ON GRIDPULL DOWN RAFT ONTO KINEMATIC MOUNTS ON GRID
MAKE UP THERMAL CONNECTIONS TO CRYO PLATE # 1MAKE UP THERMAL CONNECTIONS TO CRYO PLATE # 1
VERIFY SURFACE FLATNESS – WARM – USING METROLOGY HEADSVERIFY SURFACE FLATNESS – WARM – USING METROLOGY HEADS
DOE Review
June 2006 SLAC
21
INSTALL BACK-END ELECTRONICS
ATTACH BEE CARDS TO FLEX CABLE - TAKE UP SRVC LOOPATTACH BEE CARDS TO FLEX CABLE - TAKE UP SRVC LOOP
MAKE UP THERMAL CONNECTIONS TO BEE CAGEMAKE UP THERMAL CONNECTIONS TO BEE CAGE
ATTACH FO CABLE TO FEEDTHROUGH & TESTATTACH FO CABLE TO FEEDTHROUGH & TEST
DOE Review
June 2006 SLAC
22
REPEATFOR ALL BAYS
REPEAT METROLOGICAL & FULL ELECTRONIC TESTING – COLD REPEAT METROLOGICAL & FULL ELECTRONIC TESTING – COLD PROCEED TO INTEGRATE CRYOSTAT WITH CAMERA BODYPROCEED TO INTEGRATE CRYOSTAT WITH CAMERA BODY
CLOSE CRYOSTAT WITH L3 & REAR BULKHEAD CLOSE CRYOSTAT WITH L3 & REAR BULKHEAD VACUUM & THERMAL PROCESS THE CRYOSTAT – CHECK CONTAMINATIONVACUUM & THERMAL PROCESS THE CRYOSTAT – CHECK CONTAMINATION
DOE Review
June 2006 SLAC
23
CONCLUSIONS
• EXCELLENT PROGRESS DEVELOPING AN INTEGRATED CRYOSTAT & FOCAL PLANE DESIGN TO MEET SCIENCE REQUIREMENTS:
– VIABLE STRATEGIES FOR:
– ASSEMBLY & REPAIR – RAFT AND FOCAL PLANE METROLOGY– THERMAL CONTROL OF SENSORS AND RAFTS
• DEVELOPING MORE DETAILED DESIGN FOR VACUUM, THERMAL AND CONTAMINATION CONTROL OF CRYOSTAT AS A SYSTEM AS WELL AS THE ACTUATION OF THE GRID
• R&D TO VERIFY METROLOGY TECHNIQUES PROCEEDING
• R&D TO STUDY CONTAMINATION ISSUES & MATERIALS CONTROL STARTING UP
DOE Review
June 2006 SLAC
24
SPARE SLIDES
DOE Review
June 2006 SLAC
25
Dual sensor XY carriage
Inspection Opt. Table
Assy Opt. Table
Reference surface XY carriage
Rear Bulkhead Closed
Displacement sensors (up & down looking)
Metrology of FPA Under Vacuum and Cold
Displacement Sensor Measures FPA Through Vacuum Barrier Window.
Cryostat Body
Cryostat Closed With Vacuum Window or L3 and Cooled To Operating Temp.
Metrology Repeated [Applying Small Optical Corrections]
DOE Review
June 2006 SLAC
26
Simplify Metrology By Use of Silicon Carbide
• Significantly Better Structural and Thermal Properties Than Metals
– Expect ~ 1/3 m Sag Under Gravity & < 0.5 m From Thermal Distortion
• Good CTE Match To Al Ni In Rafts
Support Support
Support
1 G Sag of Loaded GRID
Focal Plane Assembly Unit Alum. Steel Invar 36 SC-30Total mass with rafts (25 kg) kg 100 237 246 112P-V gravity sag over aperture
0-90 elevation angle m 1.350 1.030 1.400 0.25030-90 elevation angle m 0.675 0.515 0.700 0.12545-90 elevation angle m 0.395 0.302 0.410 0.07360-90 elevation angle m 0.181 0.138 0.188 0.033
Mode shape and frequencyMode 1, torsion/twist Hz 205 219 184 463Mode 2, X translation Hz 241 261 217 546Mode 3, Y translation Hz 339 384 321 775Mode 4, Z translation Hz 366 413 346 846
Elastic modulus / density SI 25.56 25.00 17.67 130.16Thermal conductivity / CTE SI 10.00 4.69 8.08 75.00
DOE Review
June 2006 SLAC
27
Stitching Metrology Checkout (3)
• Top: 4 separate realizations of resulting surface figure error propagation, depending on grid spacings and number of intermediate reference locations.
• Bottom: demonstration of recovering an input aspherical term to 1% of its “true” value (using a 200mm diameter reference to map a 640mm diameter focal plane.
DOE Review
June 2006 SLAC
28
PROTOTYPE LASER PROJECTOR HEAD THAT WOULD BE MOUNTED ON GRID
2.00"0.75" 0.3930"
0.37"1.07"
1.57"0.15"
1.25"
0.83"
0.95"
0.35"
0.75"
0.65"0.22"
0.83"
0.95"
0.28"
1.00"
CONSTRUCTED UTILIZING STABILIZED SINGLE MODE FIBER COUPLED DIODE LASER, DIFFRACTIVE & FOCUSSING ELEMENTS
PROJECTOR HEAD
DIODE LASER
DOE Review
June 2006 SLAC
29
IMPROVEMENTS ADDRESSING REMAINING PROBLEMS
• ELONGATED ELLIPSES:
• INCREASE DENSITY TO BETTER UTILIZE GRID REAL ESTATE:
ADD FOCUSSING ELEMENT AFTER DIFFRACTIVE ELEMENT
Lens
Laser
Diffractive beam splitterCrossed gratings
ADD BEAM SPLITTER AFTER FOCUSSING ELEMENT
OR DEVELOP CUSTOMIZED MICROMACHINED DIFFRACTIVE ELEMENTS
DOE Review
June 2006 SLAC
30
OPTIMIZED MICROMACHINED 2D ARRAY OF APERTURES
Layout for chrome-on-glass diffraction grating with electron beam etched apertures being produced at Stanford in June 2006
Lens
Laser
Micromachined diffraction grating
Laser generates array of spots with relatively uniform amplitudes if apertures ~
Pattern from 0.5 micron diameter circular apertures on a grid of 150 columns per mm and 50 rows per mm.
Awarded Grant at Stanford Nanofabrication Facility To Pursue Grating Fabrication Techniques
DOE Review
June 2006 SLAC
31
CABLE TO BACK ANNULAR FLANGE
ATTACH FIBER OPTIC & FLEX CABLES TO REAR FLANGE FTATTACH FIBER OPTIC & FLEX CABLES TO REAR FLANGE FTINSTALL OTHER ELEMENTS INSTALL OTHER ELEMENTS
Guide, SH SensorsGuide, SH SensorsTemperature Monitoring & ControlTemperature Monitoring & ControlIn-Situ Metrology, Fe55 Source, Service Cables…In-Situ Metrology, Fe55 Source, Service Cables…
TEST CONNECTIONSTEST CONNECTIONS
DOE Review
June 2006 SLAC
32
Camera Integration and Test Sequence
SENSOR ACCEPTANCE TESTFunctional + Metrological (warm)
RAFT ACCEPTANCE TESTMetrological (warm)
RAFT TOWER ACCEPTANCE TESTFull Functional + Thermal + Metrological(warm and cold) + Contamination(?)
FEE
Si CCD Sensor
Raft Structure
Raft Assembly
Flex Cable &
FEE Cage
Thermal Strap(s)
Sensor Packages
CCD Carrier
Thermal Strap(s)
DOE Review
June 2006 SLAC
33
Camera Integration and Test Sequence
CRYOSTAT BODY ACCEPTANCE TESTVacuum Processing, Contamination, Plumbing, Thermal Controls, FPA Actuation
FOCAL PLANE ASSEMBLYMetrological (warm), Limited Functional Testing of Sensors & Electronics
Grid
Cryo PlateImage Stabilization Actuators
Outer Cylinder
Tested Raft Towers
BEE (not shown)
Sensors Not Shown:GuideShack HartmanCurvature
Temp. Install L3 WindowOr Blankoff
Raft Towers
Temp. install Cryostat Back Plate
Back Flange
DOE Review
June 2006 SLAC
34
Camera Integration and Test Sequence
CRYOSTAT & FPA ACCEPTANCE TEST• Metrological (warm, cold), Vacuum Processing,Contamination, Sensor Thermal Controls, Full Actuation, Full Sensor & Electronics Functional Tests
• Use In-Situ Systems To Verify Metrology In All Orientations & Following Actuation
Cryostat Rear Bulkhead
Focal Plane (one raft shown)
L3 and/or Window
Not Shown:BEE And Cables to Bulkhead Flange Other Misc CablesElements of Thermal SystemElements of Vacuum SystemIn-Situ Metrology SystemsX-Ray Source Calibration System
Cryostat Body
DOE Review
June 2006 SLAC
35
Camera Integration and Test Sequence
CAMERA BODY & MECHANISMS ACCEPTANCE TESTSMech.Functionality, Contamination
CAMERA MECH. FUNCTIONALITYACCEPTANCE TEST
Base Plate
Shutter (temp. install)
Filter Changer, (temp. install)
Camera Housing
Filter Carousel, with Dummy Filters
Cryostat Assembly With L3
•Electrical Integration
•Plumbing Integration -thermal system -vacuum system -purge system
Shutter
Functional Tests Power & ConditioningExposure Control Elect.FP Control Elect.Vacuum /Purge Control Elect.Thermal Control Elect.
Filter Changer
Utilities Frame
DOE Review
June 2006 SLAC
36
Camera Integration and Test Sequence
CAMERA CALIBRATIONS AND FINAL ACCEPTANCE TEST
L1/L2 Assembly
Filters on Carousel
Camera CalibrationsSee Talk: David Burke
Filter in use
LOAD FILTERS
ADD L1/L2