AUSTRALIAN NATIONAL UNIVERSITY System Design Note 4.02 Created: 3 July 200328 March 2003 Last modified: 5 August 20035 August 20033 July 2003

FOCAL PLANE MODULE TECHNICAL SPECIFICATIONS

Mark Downing, Jason Griesbach

Research School of Astronomy and Astrophysics

Institute of Advanced Studies

Australian National University

Revision History

Revision No.	Author & Date	Approval & Date	Description
Revision 1	Mark Downing, Jason Griesbach 7 February 2003		Original document.
Revision 2	Jason Griesbach 2 July 2003	Liam Waldron 2003-17-07	Modified to remove contract information (costing, schedules, etc) and to remove GL Scientific responsibility for handling detectors.
Revision 3	Liam Waldron 2003-17-07	Liam Waldron 2003-17-07 Jan van Harmelen 2003-17-07	(4.3) Gemini responsibility, (4.4) Rockwell Responsibility removed. RSAA Responsibility modified.

Contents

1 Purpose. 3

2 Introduction. 3

3 Focal Plane Module Requirements. 3

3.1 Requirements List 3

3.1.1 Focal Plane Flatness. 3

3.1.2 Focal Plane Flexure. 3

3.1.3 Detector X/Y Spacing. 3

3.1.4 Background Radiation. 4

3.1.5 Focal Plane Module Camera Mount 4

3.1.6 Heat Flow Symmetry. 4

3.1.7 Cold Strap Connection. 4

3.1.8 Electrical Connection. 4

3.1.9 Thermal Control 5

3.1.10 Handling. 5

3.1.11 Blackening. 6

3.1.12 Temperature Environment 6

3.2 Requirements Qualification Methods. 7

4 Responsibility. 7

4.1 GL Scientific Responsibility. 7

4.2 RSAA Responsibility. 8

5 Interfaces. 8

5.1 Focal Plane Module Mechanical Interface (including Cold Strap Interface) 8

5.2 Focal Plane Detector Electronic Interface. 8

5.3 Temperature Control Interface. 9

6 Documentation. 9

7 Risks. 9

7.1 Focal Plane Module Delivery. 9

7.2 Unproven Design. 9

1 Purpose 2

2 Introduction 2

3 Focal Plane Module Requirements 2

3.1 Requirements List 2

3.1.1 Focal Plane Flatness 2

3.1.2 Focal Plane Flexure 3

3.1.3 Detector X/Y Spacing 3

3.1.4 Background Radiation 3

3.1.5 Focal Plane Module Camera Mount 3

3.1.6 Heat Flow Symmetry 4

3.1.7 Cold Strap Connection 4

3.1.8 Electrical Connection 4

3.1.9 Thermal Control 4

3.1.10 Handling 5

3.1.11 Blackening 5

3.1.12 Temperature Environment 5

3.2 Requirements Qualification Methods 6

4 Responsibility 6

4.1 GL Scientific Responsibility 6

4.2 RSAA Responsibility 7

5 Interfaces 7

5.1 Focal Plane Module Mechanical Interface (including Cold Strap Interface) 7

5.2 Focal Plane Detector Electronic Interface 7

5.3 Temperature Control Interface 8

6 Documentation 8

7 Risks 8

7.1 Focal Plane Module Delivery 8

7.2 Unproven Design 8

1 Purpose 1

2 Introduction 1

3 Focal Plane Module Requirements 1

3.1 Requirements List 1

3.1.1 Focal Plane Flatness 1

3.1.2 Focal Plane Flexure 3

3.1.3 Detector X/Y Spacing 3

3.1.4 Background Radiation 3

3.1.5 Focal Plane Module Camera Mount 3

3.1.6 Heat Flow Symmetry 4

3.1.7 Cold Strap Connection 4

3.1.8 Electrical Connection 4

3.1.9 Thermal Control 4

3.1.10 Handling 5

3.1.11 Blackening 5

3.1.12 Temperature Environment 5

3.2 Requirements Qualification Methods 6

4 Responsibility 6

4.1 GL Scientific Responsibility 6

4.2 RSAA Responsibility 7

4.3 Gemini Responsibility 7

4.4 Rockwell Responsibility 7

5 Interfaces 7

5.1 Focal Plane Module Mechanical Interface (including Cold Strap Interface) 7

5.2 Focal Plane Detector Electronic Interface 7

5.3 Temperature Control Interface 8

6 Documentation 8

7 Risks 8

7.1 Focal Plane Module Delivery 8

7.2 Unproven Design 8

1 Purpose

This system design note defines the technical specifications and describes the detailed design, fabrication, documentation and testing of the GSAOI focal plane module.

2 Introduction

The focal plane module is the cryogenic subsystem in which the GSAOI imager detector mosaic of four Rockwell NGST packaged HAWAII-2RG (H2RG) HgCdTe/CdZnTe Molecular Beam Epitaxy (MBE) devices is mounted. It consists of the detector flex circuits, focal plane mounting plate, titanium legs, molybdenum spacers, base plate, temperature sensors, heaters, and connectors for thermal control of the focal plane mounting plate and base plate, the detector light shield and mask, and the module cover plate. The detector flex circuits shall be terminated in 37 pin microminiature-D connectors. This is compatible with the GSAOI requirements to read out the H2RGs through four outputs and use a non-ASICs detector controller (SDSU III). Gemini has stated that they are not interested in updating GSAOI to use ASICs or to read out through 32 outputs.

The design and construction of two focal plane modules will be subcontracted to Gerry Luppino through GL Scientific.

The term “focal plane module” is defined above. The term “focal plane assembly” refers to a focal plane module that has been populated with detectors.

3 Focal Plane Module Requirements

3.1 Requirements List

The focal plane module shall meet the following requirements.

3.1.1 Focal Plane Flatness

REQ-FPA-0001: The focal plane shall be flat to ± 1085 mm. The surfaces of the four detectors mounted in the focal plane assembly shall concurrently be fully contained between a pair of parallel planes separated by 20 µ0.17mm. (See SDN 02.09, April 2003)

GL Scientific will measure the unpopulated focal plane flatness before the focal plane module is shipped. The flatness of the focal plane is expected to be less than ± 10 mm (TBD by GL Scientific). This flatness will be verified by RSAA when the focal plane module is received. GL Scientific will provide detailed instructions and, the necessary installation fixtures, and molybdenum spacers so that RSAA will be equipped to mount the detectors. RSAA will measure and adjust height and tip tilt of each individual HAWII-2RG to the same reference plane by grinding the molybdenum spacers provided by GL ScientificRockwell. RSAA will assemble the HAWII-2RGs in the focal plane and verify flatness. RSAA will purchase and house appropriate metrology equipment to perform verification measurements.

3.1.2 Focal Plane Flexure

REQ-FPA-0002: Flexure at all orientations of the focal plane with respect to the detector housing shall be < 0.61.8 mm per 15° change of azimuth in the x and y directions, and < 108 mm in the z direction, where the z direction is normal to the detectors. RSAA will do FEA analysis to demonstrate that the focal plane module will meet flexure specifications. RSAA will verify flexure during flexure tests of the final GSAOI cryostat.

3.1.3 Detector X/Y Spacing

REQ-FPA-0003: The spacing between the detectors shall be ≤ 2.5 mm, and the columns of all detectors shall be parallel to < 80 mm in relationship to the centerline of the focal plane. GL Scientific will specify the appropriate tolerance for the focal plane manufacture. The final spacing, however, will be determined by how accurately Rockwell can glue the detector onto the package. RSAA will verify spacing between the detectors by measurement.

3.1.4 Background Radiation

REQ-FPA-0004: The focal plane module shall shield the detector from, and not generate, background radiation such that the detector dark current requirement of < 0.1e/s/pixel can be met. GL Scientific will meet background radiation specifications by following good radiation shielding practices and blackening all surfaces. RSAA will verify that background radiation specifications are met by performing dark current tests on the populated focal plane assembly in the RSAA test cryostat.

3.1.5 Focal Plane Module Camera Mount

3.1.5.1 Camera Attachment Points

REQ-FPA-0005: Convenient attachment points shall be provided on the corners of the focal plane module baseplate for mounting to the camera body. .

3.1.5.2 Camera Interface Light Seal

REQ-FPA-0006: An acceptable method of providing a light tight seal where the focal plane module attaches to the camera body shall be provided. GL Scientific will meet this specification by providing a surface at the front of the focal plane module that RSAA can mate with to obtain a light tight seal. RSAA will inspect the design to verify that a quality light seal can be made. Additionally, RSAA will verify the effectiveness of this light tight seal by performing dark current tests on the populated focal plane in the final GSAOI cryostat.

3.1.5.3 Focal Plane Assembly Electrical Isolation

REQ-FPA-0007: The focal plane assembly shall be able to be electrically isolated from the rest of the cryostat and connected to detector ground to allow the focal plane module to act as a Faraday shield to reduce electrical noise pickup. The design will be inspected to verify that the focal plane assembly can be electrically isolated from the rest of the cryostat.

3.1.5.4 Focal Plane Assembly Thermal Isolation

REQ-FPA-0008: The focal plane assembly shall be able to be thermally isolated from the rest of the cryostat to allow the outer focal plane assembly to be thermally controlled. The design will be inspected to verify that the focal plane module can be thermally isolated from the rest of the cryostat.

3.1.6 Heat Flow Symmetry

REQ-FPA-0009: Heat flow in the vicinity of the detector mosaic shall be symmetric to the greatest extent possible in order to minimize temperature gradients within the detectors. The mechanical design will be inspected to verify that symmetric heat flow is achieved.

3.1.7 Cold Strap Connection

REQ-FPA-0010: A cold strap connection shall be made from one edge of the focal plane module base plate via a single connection. . The copper to aluminium cold strap connection point will be electrically isolated with Silpad and Delrin isolating components.

3.1.8 Electrical Connection

3.1.8.1 Electrical Connection Points

REQ-FPA-0011: Electrical (both temperature and detector) connections shall be made from the back or edge of the focal plane assembly for ease of assembly/disassembly. Two connectors will be provided for thermal control; one for focal plane plate thermal control and the other for base plate thermal control. The design will be inspected to verify that electrical connections can be made from the back and that two connectors are provided for thermal control.

3.1.8.2 Detector Connector Type

REQ-FPA-0012: The detector flex circuits shall be terminated in 37 pin micro-D subminiature connectors. The baseplate light-tight feedthroughs shall use 37 pin micro-D subminiature connectors.

The use of 37 pin micro-D subminiature connectors will provide reliable termination points for the cryostat flex circuit when a motherboard is not used.

3.1.8.3 Focal Plane Motherboard

REQ-FPA-0013: The focal plane module shall provide the capability to use a motherboard if required.

The baseline design will not use a motherboard. A motherboard will be required if pre-amplifiers, additional filtering, protection circuitry, or clock terminations are required close to the detector. The design will be inspected to verify that the use of an optional motherboard is supported.

3.1.9 Thermal Control

GL Scientific shall provide analytical evidence to demonstrate that the focal plane module shall meet the following thermal specifications. RSAA will verify that the focal plane module meets thermal specifications by doing thermal tests in the RSAA test cryostat.

3.1.9.1 Detector Temperature Control

REQ-FPA-0014: The focal plane assembly shall allow the detector temperature to be thermally controlled to ±1 mK between 60 K and 90 K.

3.1.9.2 Detector Temperature Accuracy

REQ-FPA-0015: The absolute accuracy of the focal plane assembly temperature set point shall be 0.5 K or better. Temperature accuracy will be verified by reference to manufacturer’s temperature sensor data sheet.

3.1.9.3 Cool-down/Warm-up Time

REQ-FPA-0016: The focal plane assembly shall not add > 8 hours to the cool down and warm up time of the cryostat. Once the cryostat reaches temperature, the detectors should be able to be temperature controlled to required specifications within 8 hours.

3.1.9.4 Temperature Sensors

REQ-FPA-0017: Temperature sensors used to control the focal plane and base plate temperatures shall be Lakeshore Cernox series CX-1080-XX-20L sensors. This requirement will be verified by inspecting the design.

3.1.9.5 Heater Type

REQ-FPA-0018: The heater types and ohmic values used for thermally controlling the focal plane mounting plate and baseplate shall be compatible with the Lakeshore model 340 temperature controller. The heater shall have low thermal resistance and thermal time lag to allow the temperature control to react quickly to temperature disturbances.

3.1.9.6 Heater Power Dissipation

REQ-FPA-0019: When the focal plane is temperature controlled to the required specifications, the focal plane plate and baseplate heaters shall not dissipate more than 200 mW.

3.1.10 Handling

REQ-FPA-0020: The focal plane assembly shall be self-contained. It shall be removable from the camera as a single mechanical entity after disconnection of electrical signal cables, cold strap, and the devices that mount the module to the camera body. The module shall be provided with a cover that will protect the detector mosaic during handling. RSAA will inspect the design to verify that it meets the handling requirement.

3.1.11 Blackening

REQ-FPA-0021: A non-flaking, vacuum and cryogenic rated infrared optically black material shall be used for blackening all module mechanical surfaces potentially exposed to light. GL Scientific will meet this requirement by specifying the process by which the module parts will be blackened and by providing proof that it is non-flaking and has good optically black properties. RSAA will verify the non-flaking requirement by doing thermal cycling tests in the test cryostat and the infrared optically black property by analysis of the blackening process used and reference to manufacturers data sheets.

3.1.12 Temperature Environment

GL Scientific shall provide analytical evidence or information from manufacturers data sheets that each component of the focal plane assembly meets the following temperature environment specifications. RSAA will verify that the focal plane module meets temperature environment specifications by studying this evidence.

3.1.12.1 Laboratory Warm Environment

REQ-FPA-0022: The focal plane assembly shall be capable of operating warm in the laboratory over a temperature range of -15 to +25°C.

3.1.12.2 Survival Environment

REQ-FPA-0023: The focal plane assembly shall be capable of surviving a temperature range of -20 to +50°C without damage.

3.1.12.3 Transport Environment

REQ-FPA-0024: The focal plane assembly shall be capable of withstanding a temperature range of -20 to +50°C during transport without damage.

3.2 Requirements Qualification Methods

Table 1: Summary of Requirements Qualification Methods.

Requirement Number	Engineering Requirement	GL Scientific Qualification Method	RSAA Qualification Method
REQ-FPA-0001	Focal Plane Flatness	Measurement	Measurement
REQ-FPA-0002	Focal Plane Flexure	Analysis by RSAA	Measurement
REQ-FPA-0003	Detector X/Y Spacing	Reference to Design	Measurement
REQ-FPA-0004	Background Radiation	Reference to Design	Laboratory Test
REQ-FPA-0005	Camera Attachment Points	Reference to Design	Reference to Design
REQ-FPA-0006	Camera Interface Light Seal	Reference to Design	Reference to Design/ Laboratory Test
REQ-FPA-0007	Focal Plane Assembly Electrical Isolation	Reference to Design	Reference to Design
REQ-FPA-0008	Focal Plane Assembly Thermal Isolation	Reference to Design	Reference to Design
REQ-FPA-0009	Heat Flow Symmetry	Reference to Design	Reference to Design
REQ-FPA-0010	Cold Strap Connection	Reference to Design	Reference to Design
REQ-FPA-0011	Electrical Connection Points	Reference to Design	Reference to Design
REQ-FPA-0012	Detector Connector Type	Reference to Design	Reference to Design
REQ-FPA-0013	Focal Plane Motherboard	Reference to Design	Reference to Design
REQ-FPA-0014	Detector Temperature Control	Analysis	Laboratory Test
REQ-FPA-0015	Detector Temperature Accuracy	Reference to Data Sheet	Reference to Data Sheet
REQ-FPA-0016	Cool-down/Warm-up Time	Analysis	Laboratory Test
REQ-FPA-0017	Temperature Sensors	Reference to Design	Reference to Design
REQ-FPA-0018	Heater Type	Analysis	Laboratory Test
REQ-FPA-0019	Heater Power Dissipation	Analysis	Laboratory Test
REQ-FPA-0020	Handling	Reference to Design	Reference to Design
REQ-FPA-0021	Blackening	Refer to Process	Laboratory Test/ Analysis/ Reference to Data Sheets
REQ-FPA-0022	Laboratory Warm Environment	Analysis/Reference to Data Sheets	Analysis/Reference to Data Sheets
REQ-FPA-0023	Survival Environment	Analysis/Reference to Data Sheets	Analysis/Reference to Data Sheets
REQ-FPA-0024	Transport Environment	Analysis/Reference to Data Sheets	Analysis/Reference to Data Sheets

4 Responsibility

4.1 GL Scientific Responsibility

GL Scientific will be responsible for the following:

· Designing, fabricating, and assembling two focal plane modules. The focal plane modules include the focal plane mounting plate, titanium legs, base plate, the detector light shield and mask, and the module cover plate.

· Designing, and fabricating detector flex circuits of the multiplexer, the two engineering, and the four science detectors.

· Providing the assembly fixtures, spacers and detailed instructions for installing, removing and leveling the detectors in the focal plane.

· Delaying the fabrication of the second focal plane module until the first focal plane assembly has been tested by RSAA and feedback report received.

· Blackening all module mechanical surfaces potentially exposed to light.

· Providing the module with a cover that will protect the detector mosaic during handling.

· Providing, mounting, and wiring of temperature sensors, heaters, and connectors for thermal control of the focal plane plate and the baseplate.

· Designing of cold finger attachment locations in agreed with RSAA and providing any necessary taped holes for their mount.

· Providing attachment locations for mounting the assemblies to the camera body and a method of light tight sealing the focal plane assembly to the camera body.

· Providing details of the mechanical and electrical interfaces described in §5.

· Providing documentation as detailed in §6.

· Providing a sealed transport case capable of maintaining a dry nitrogen shipping environment for the focal plane module.

· Safe packing and shipping of the focal plane module to RSAA.

4.2 RSAA Responsibility

RSAA will be responsible for the following:

· Verifying that the focal plane assembly meets flexure requirements by performing flexure tests and/ordoing FEA analysis.

· Verifying that the temperature control of the focal plane plate and baseplate achieves the required specifications by doing thermal analysis (GL Scientific is responsible for meeting these specifications).

· Attaching the flex circuits to the detectors.

· Metrology of the multiplexer, the two engineering, and the four science detectors, and lapping of Molybdenum spacers to obtain the required focal plane flatness. All detectors will be installed and adjusted to the same reference plane and should be able to be installed in either focal plane assembly.

· Verifying that the detector spacing requirements are met (GL Scientific is responsible for meeting these specifications).

· If required, designing, fabricating, and assembling the detector motherboard to meet the detector performance specifications.

· Paying for the non-recurring design costs of the detector flex circuits.

1.1 Gemini Responsibility

Through the ANU/Gemini Fabrication Document, Gemini will be responsible for the multiplexer, the two engineering, and the four science detectors until they reach RSAA.

1.1 Rockwell Responsibility

Rockwell is responsible for paying for the fabrication costs of the detector flex circuits.

5 Interfaces

5.1 Focal Plane Module Mechanical Interface (including Cold Strap Interface)

The mechanical interface defines the focal plane module physical dimensions, mechanical mounting to the GSAOI camera body, and the cold strap connection points. GL Scientific will describe this interface by providing an electronic 3-D mechanical model in AutoCAD Mechanical Desktop v.6 dimensioned in mm.

5.2 Focal Plane Detector Electronic Interface

The detector electronic interface defines the number and type of connectors, their pin assignments, their mechanical position in focal plane assembly, and the physical dimensions of the motherboard. GL Scientific will describe the position of the connectors and the mechanical dimensions of the motherboard by providing an electronic DXF mechanical drawing that can be imported into RSAA PCB design package Protel 99 SE. GL Scientific will describe the position of the 37 pin micro-D subminiature connectors of the detector flex circuit and of the light tight feedthrough in the focal plane assembly by providing an electronic 3-D mechanical model in AutoCAD Mechanical Desktop v.6 or in Inventor V6 dimensioned in mm.

5.3 Temperature Control Interface

The temperature control interface defines the number and type of connectors, their pin assignments, and the mechanical position of connectors in the focal plane assembly. GL Scientific will describe the mechanical position of the connectors in the focal plane assembly by providing an electronic 3-D mechanical model in AutoCAD Mechanical Desktop v.6 or Inventor V6 dimensioned in mm. GL Scientific will describe the electrical interface by providing an electrical schematic of the temperature sensors, heaters and connector wiring in paper hardcopy and electronic version in a suitable file format.

6 Documentation

GL Scientific will provide the following documentation:

· A complete set of detailed as-built mechanical fabrication and assembly drawings for each mechanical component and for the completed module in paper hardcopies and electronic versions in AutoCAD Mechanical Desktop v.6 or Inventor V6.

· Electrical schematic of temperature and detector wiring in paper hardcopies and electronic version in a suitable file format.

· A complete list of commercially procured components, showing the name and address of the part fabricator and of the vendor.

· Metrology test report for each focal plane module.

· An assembly and alignment procedures manual.

· Device installation procedures manual.

7 Risks

7.1 Focal Plane Module Delivery

Late delivery of the focal plane module from GL Scientific is a schedule risk. Defining the delivery schedule for each project phase in the subcontract to GL Scientific, by remaining in close communication with Gerry Luppino, and following CFHT design to the greatest extent possible, shall mitigate this risk.

7.2 Unproven Design

It is unlikely that the thermal design and mechanical flexure of the current version of the GL Scientific focal plane module will have been tested before the first GSAOI module is delivered. Don Hall has fabricated two focal plane assemblies and tested one, but these were much earlier designs. The design has since been heavily modified. CFHT has one on order from GL Scientific, but are waiting for ASICs to be proved. RSAA doing thermal and flexure analysis to prove the GL Scientific design shall mitigate the risk of not meeting the thermal and mechanical flexure requirements. Additionally, early delivery of the first focal plane module will be sought to do thermal and flexure measurements.