Update to Near Infrared System for SNAP

1. Update to Near Infrared System for SNAP Vic Scarpine FNAL SNAP Electronics Meeting March 11, 2003

2. Topics • SNAP NIR Overview • Visit to University of Michigan • What is Michigan doing? • Discussions on NIR issues • What can Fermilab do?

3. State-of-the-art 2k x 2k HgCdTe detector with 1.7 mm cutoff under development by RSC NIR System Concept • 150 NIR Megapixels: • 36 (2k  2k) 18 mm HgCdTe detectors (0.34 sq. deg) • 3 special bandpass filters covering 1.0 –1.7 mm in NIR • T = 140K (to limit dark current) HgCdTe

4. NIR System: Performance Goals

5. Risk Assessment Presented to DOE • Read Noise • Initial measurements of 1.7m devices have noise problem • Additional production runs may be needed • Hope that WFC3 solves this problem or… • May be to modify readout strategy to achieve required read noise • Intrapixel Variation • May not be acceptable for photometry • Rockwell may be able to “sculpt” electric field • Simulation shows dithering is a solution but needs to be measured • How do you spec this for a vendor?

6. Risk Assessment Presented to DOE • Qualification Testing • Need to define characterization and qualification of large number of HgCdTe devices • To obtain 44 science grade devices need to test at least several hundred devices • For NSGT 25 devices they are planning three large test and qualification facilities

7. SNAP NIR Players • Greg Tarle, Univ of Michigan – NIR R&D coordinator • Univ of Michigan - have begun to set up HgCdTe evaluation facility • Number of professors, research scientists, post-docs, grad student • ~ 3-4 full-time equivalent • Univ of Indiana – working with Michigan on filters and quantum efficiency measurements • LBL – development of readout electronics?? • Don Figer – infrared detectors consultant at Space Telescope Science Institute • Rockwell – HgCdTe FPA supplier. Possible readout chip. • Ratheon – developing HgCdTe FPA • Others??? Caltech/JPL/UCLA?

8. Main NIR R&D Activities* • Establish a facility for testing and characterizing NIR FPAs at University of Michigan • Study detector read noise and reduction with multiple reads • Study intrapixel variations and impact on photometry • Develop mechanical and thermal concept for NIR imager • Develop plan for testing and qualifying large numbers of HgCdTe FPAs • Produce R&D phase deliverables • Produce realistic cost and schedule estimates for CDR *SNAP R&D Plan

9. Michigan Infrared Detector Lab • Comparative testing and evaluation of industrial supplied HgCdTe FPAs • Characterize read noise, dark current and quantum efficiency • Study intra-pixel variations and impact on photometry • Determine optimum sampling strategy for reducing RMS read-out • Establish facilities for receiving and qualifying NIR FPAs • Optimize calibration techniques and strategies • Develop mechanical and thermal concept for NIR imager in an integrated focal plane

10. Michigan Infrared Detector Lab • Lab being established • dewar/vacuum system built • Low noise DAQ electronics purchased and being integrated • Testing multiplexers to debug system and set noise floor • Need to acquire science grade FPA ($$$) • Test setup ~ $100K

11. U of M Visit - Issues • New question about Rockwell FPA pixel stability • Dark current appears function of readout time • Is this charge trapping effect? • If so them has many effects: i.e. linearity, image lag • Rockwell vs Ratheon • Rockwell has made 1.7m for WFC3 • Ratheon has made 2k x 2k, 2.5m for VISTA • Both want ~> $500K for development of SNAP 2k x 2k 1.7m prototypes • Time to receive first science grade test FPA critical • U of M may purchase and reimbursed by DOE • Not clear why they can’t get one of the WFC3 rejects for testing

12. U of M Visit - Issues • Electronics Readout Chip • Use LBL CCD chip? • Rockwell may develop readout chip • Will this meet SNAP requirements? • Not sure if Raytheon making a chip • Other players??? • Does FNAL have an interest here? Can we do a better job? • Political Question • Will NIR completely end up in NASA’s hands?

13. U of M Visit - Issues • Device characterization and testing plan • Question of how to spec and measure NIR FPA parameters • Intrapixel variance • Pixel stablility • Scientific Issues – Tim McKay • Should the NIR format be re-evaluated for non-SN science? • Are the filters optimized? • Is SNAP pushing 1.7m too hard? • Backing off may have small effect on SN search but allow for more imaging time?

14. What can Fermilab do for NIR? • Develop a test and qualification site • Fermilab experience in detector measurements • About a year away - allows time to setup test system • Already too many players? • ~ $100K and few full-time equivalent • Simulation • Study optimizing NIR detectors for science • Clustering, weak lensing • FNAL astrophysicist involvement • Detector simulation? • Intrapixel variation, dithering, charge-trapping • Fermilab can help now

15. Ongoing HgCdTe Characterization Efforts • Detector Characterization Lab (DCL) at Goddard Space Flight Center (PI Ed Cheng) The DCL currently supports the characterization of HgCdTe detectors for the Hubble Space Telescope Wide Field Camera 3 instrument. • NASA has funded four laboratories to develop and assess the quality of NGST prototype detectors: • The University of Hawaii Laboratory (PI Donald Hall) will develop and characterize HgCdTe detectors manufactured by Rockwell Scientific. • The University of Rochester Laboratory (PI William Forrest) will develop and characterize InSb detectors made by Raytheon Infrared Operations. • The Independent Detector Testing Laboratory (PI Don Figer) at Space Telescope Science Institute and the Johns Hopkins University will characterize both HgCdTe and InSb detectors in a comparative hardware setup. • The Laboratory at NASA Ames Research Center (PI Craig McCreight) is developing and characterizing Si:As mid-infrared detectors.

16. What can Fermilab do for NIR? • Readout chip development • Fermilab has lots of ASIC experience • Use Fermilab ASIC experience someplace in SNAP • If interested then when do we start? • Investigate non-HgCdTe technologies • Look into issues for making large format InGaAs FPAs – compile information • Is it too much development time for SNAP? • Are there other players looking down this road?

17. E-Mail from Michael Levi to John Marriner Dear John, Just to correct an important issue in your write-up, I need to point out that there is another major axis in the NIR area. We have "married“ the Michigan effort to a major Caltech/JPL/UCLA effort in the NIR. The Caltech group is heavily involved in the development and testing of the commercial readout chip as well as involved with JPL & UCLA in the development (and deploying on telescopes) of the detector technology. In the next two years the issue with the detector development is a solid-state physics problem as opposed to straight-out testing. The NIR detectors do not currently meet our specifications and we had to bring NIR experts in to work on this aspect. The development of a second axis was a management decision to bring in world-class experts in NIR. So, the FNAL interest in this area would be a third effort -- thus would require a careful coordination of interests, skills, and timing. Thanks for listening, Michael