Electrical Design
Tom Gauron
Conceptual Design - Phase A Quarterly Review
Period: 15 April 2011 to 08 June 2011

Outline
• Functional requirements
• Electrical design status
• NIRMOS electrical system
• Electrical subassemblies

Functional Requirements
• Instrument support and interface to facility
– Support rack mounted on instrument platform
– Receive AC power, Ethernet, coolant, CA, and GN from facility
– Power supplies, instrument computer(s), cable interface to instrument

Functional Requirements
• Instrument cables
– Moving Cables
• Power, Ethernet, coolant, GN, CA to NIRMOS on GIR via energy chain
– Local instrument
• Internal, cryo-vacuum rated cables (incl. detector array
Flex print moving cables)
• External subsystem to subsystem and to cryostat panel cables

Functional Requirements
• Calibration (suggested approach)
– Electronics to drive continuum and gas lamps
– Shutter and controller
– Single axis mechanism control

Functional Requirements
• Environmental control
– Cryocooler drive and closed loop control
– Temperature monitoring
– Vacuum pump control and monitoring
• Motion Control
– Control of stepper based precision optics positioning
– Control of LVPZT focal plane mechanism for flexure compensation and focus

Electrical Design Status
• Current Status:
– Electrical conceptual design completed
– System block and cable interconnect diagrams completed
– All support e-boxes defined
• Individual BOM’s created and costed
• Labor estimates completed

NIRMOS Electrical System
• Science detector assembly
• Support rack
• System moving cables
• Instrument interface
• Local instrument cables
• Electrical subassemblies
• Cryostat mounted electronics

Functional Requirements
• Science detector assembly
– Turnkey system from Teledyne Imaging Systems
– H2RG imager control, interface, and science data transport
– 6 – 4k x 4k 15um pixel Teledyne Imaging Systems detector/mux assemblies
– 6 – SIDECAR ASIC PWB’s co-located with science array for imager control, pixel digitization, and data transport via 16-bit LVDS parallel data
– Data rate >300 kpix/sec
– Interfaced to digital control boards in detector support assembly via 6 – moving flex circuit cables

Functional Requirements
• H4RG performance
– Expected read noise: 15 e / pix (per read) based on H2RG measurements
– Expect further reduction using Fowler sampling down to 1’s of e (<3e for >4-5min exposure)
– Dark current estimated at ~1e in 4min (@77K)
– SIDECAR ASIC performance baselined at
300kpix/sec (1.75 sec/frame) but can operate up to 500kpix/sec

Electrical Subassemblies
• Instrument electrical subassemblies
– Common design
• COTS components used where possible
• Rugged construction
• Light tight
• Designed for serviceability
• Thermally insulated with liquid loop heat extraction
• Robust MIL-C connectors
• Common power, coolant, and Ethernet input scheme

Electrical Subassemblies
• Support rack
– Cable and hose interface to facility
– LVPS
– Ethernet distribution
– Instrument CPU’s
– Cable interface to instrument on GIR via cable energy chain

Electrical Subassemblies
• Instrument electrical subassemblies
– Mechanism control
• 24-axis step motor control using Delta Tau PMAC, DSP based motion controller
• Position feedback via end of travel limits and resolver on select axes
• Safe-to-move interlock system
– Flexure control
• 5-axis precision position control using Physik
Instrument “finger walker” LVPZT technology

Electrical Subassemblies
• Electrical (instrument) interface
• Physical cable interface on GIR
• Local Ethernet and power distribution to reduce moving cables from support rack
• Focal plane array support
– Teledyne JADE-2 derived H4RG-SIDECAR ASIC control and interface PWB’s
– Ethernet data transport
– Redundant, low-noise, LVPS for science array electronics
– Science detector array cryo-temperature controller (Lakeshore 335)

Electrical Subassemblies
• Cryogenic control
– Sunpower cryo-cooler control/driver modules with RS-232 to Ethernet communications
• Temperature and vacuum control
– Temperature monitors (Lakeshore 218S)
– Vacuum gauge controller (Pfeiffer DPG109)
– Vacuum pump controllers (Varian)
– Heater controllers for instrument warm-up
(Omega CNi16D54)

Electrical Subassemblies
• Instrument cables (internal to cryostat)
– Vacuum rated connectors, conductors, labels, etc.
– Designed to minimize thermal path to exterior
• Instrument cables (external to cryostat)
– Robust MIL-C circular connectors used
– Keyed connectors to prevent mis-connect
– Flexible, industrial cable cordage used
– Cable shielding selected for EMI/RFI on a per signal type basis

Electrical Subassemblies
• Calibration electronics (suggested)
– High and low voltage programmable power supplies for Th-AR and continuum lamps
– Shutter and controller
– Provision for single axis mechanism (e.g. deployable screen)
– Preliminary design is based on Binospec calibration subsystem

Electrical Subassemblies
• Electronics internal to cryostat
– Mechanism electrical
• Cryo-vacuum rated step motors
• End of travel limits (all axes)
• Resolver position feedback (selected axes)
• Local connector interface for service
• Local temperature sensors
– Cryocoolers
• Sunpower GT cryocoolers and local temperature sensor for closed loop control located throughout cryostat