DESI CD1 Review P 4 Plenary Corrector Optomech

DESI CD-1 Review P 4 Plenary Corrector, Opto-mech, Focal Plane Instrument Joseph Harry Silber (LBNL) Focal Plane System L 2 manager J. Silber 09/09/2014 CD-1 Review 1

DESI’s Major Items (opto-mechanical) Focal Plane Enclosure (FPE) Corrector Barrel Focal Plate Assembly (FPA) • moves on a hexapod • 5000 Fiber Positioners • 100 Illuminated Fiducials • 10 Guide/ Focus / Alignment cameras (GFAs) Corrector Optics • 4 silica lenses (C 1 -C 4) • 2 atmospheric dispersion correctors (ADC 1 -ADC 2) Upper Ring Cage Spiders (existing Mayall telescope) Cage & Ring Assembly Fiber View Camera (FVC) J. Silber 09/09/2014 CD-1 Review 2

Corrector optics • 6 lenses, 2 are atmospheric dispersion correctors (ADCs) • See DESI-0329 J. Silber 09/09/2014 CD-1 Review 3

Corrector lenses and ADCs C 1 C 4 C 3 C 2 ADC 2 BO 1. 1 Doel ADC 1 Element Diameter (mm) Mass (kg) Material Aspheric surfaces C 1 1140 201 Silica 0 C 2 850 151 Silica 1 ADC 1 800 102 N-BK 7 0 ADC 2 804 89 N-BK 7 0 C 3 834 84 Silica 1 C 4 1034 237 Silica 0 J. Silber 09/09/2014 CD-1 Review Moving a DES lens for alignment at UCL (University College London). 4

Lens Cells Spacer Steel ring Retaining ring and pad Barrel wall (carbon steel) Flexure • Supports each lens • Mounts in barrel • Flexures for thermal expansion Radial Insert Lens (glass) Radial Pad (RTV) Adjustment screw Axial Insert Axial Pad (RTV) Locking screw Cell (nickel-iron) Installation of a DES lens into cell at UCL. J. Silber 09/09/2014 CD-1 Review 5

Atmospheric Dispersion Correctors Dispersion due to prismatic effect of atmosphere at 30° elevation angle on Kitt Peak. Compensate with ADC (rotatable pair). ADC 1 Dispersion ADC 2 Dispersion + Atmospheric Dispersion J. Silber 09/09/2014 CD-1 Review = Net ADC Dispersion Image Dispersion 6

Barrel and Hexapod • Steel weldment in several segments BO 1. 2 Gutierrez • Each segment holds 2 lens cells • 6 DOF hexapod adjusts barrel within +/-10 mm range Hexapod Barrel C 1 C 4 Assembling DES barrel segments at UCL. J. Silber 09/09/2014 CD-1 Review 7

Cage, Spiders, Ring • mounts to Mayall truss • replacement of Mayall upper ring (no flip mechanism needed) Cage Spiders Upper Ring J. Silber 09/09/2014 CD-1 Review DES barrel on Blanco (Mayall’s twin) simulator at FNAL. 8

Corrector Requirements Doc SRDB ID Requirement DESI-0478 IN. COR-1002 -5 DESI-0478 Value Rationale Verif. Method Corrector mean design blur < 0. 4 arcsec DESI-0347 Analysis IN. COR-1006 Corrector field of view DESI-0315 Analysis DESI-0596 IN. COR-10601 Coating mean transmission > 98. 5% DESI-0347 Test DESI-0612 IN. COR-10110 C 1 cell static decenter ≤ 30 μm DESI-0335 Test DESI-0612 IN. COR-10111 C 1 cell dynamic decenter ≤ 50 μm DESI-0335 Analysis DESI-0612 IN. COR-10200 C 1 lens static decenter ≤ 50 μm DESI-0335 Test DESI-0612 IN. COR-10201 C 1 lens dynamic decenter ≤ 8 μm DESI-0335 Analysis DESI-0617 IN. COR-3000 Total mass ≤ 7000 kg DESI-0618 Analysis, Insp. DESI-0617 IN. COR-3002 Hexapod lateral step size < 15 μm DESI-0347 Test > 3° Some key requirements are shown in table above. DESI-0478 Complete list (24 items) of Corrector Optical Design requirements. DESI-0596 Complete list (11 items) of Corrector Lens Coating requirements. DESI-0612 Complete list (71 items) of Corrector Mechanical requirements. DESI-0617 Complete list (12 items) of Corrector Support Assy requirements. J. Silber 09/09/2014 CD-1 Review BO 4. 2 Besuner 9

Corrector production • WBS 1. 2 “Corrector and ADC Assembly” — P. Doel (UCL), BO 1. 1 — Lens procurement, coating — Mounting lenses in cells — Mounting cells in barrel • WBS 1. 3 “Cage & Ring Assembly with Barrel Components” — G. Gutierrez (FNAL), BO 1. 2 — Upper ring, spiders, cage — Corrector barrel — Hexapod and controller J. Silber 09/09/2014 CD-1 Review 10

Main items at prime focus Focal Plate Assembly (FPA) Fiber Cables Focal Plane Enclosure (FPE) Ring Cage Spider 5000 fiber positioners Corrector J. Silber 09/09/2014 CD-1 Review Services to FPS, hexapod, ADC will go up the rear spiders in this view. 11

Focal Plate Structure 10 identical petals Mounted in single integration ring Demonstrator petal from IAC. Full-scale test of machining tolerances and survey methods. J. Silber 09/09/2014 CD-1 Review 12

Fiber Positioners J. Silber 09/09/2014 CD-1 Review 13

Fiber Positioners • 6 generations, 24 units, production-ready J. Silber 09/09/2014 CD-1 Review 14

Fiber Positioner Interface to Plate J. Silber 09/09/2014 CD-1 Review 15

GFAs (guide/focus/alignment cameras) • • 1 GFA per petal 6 x flat filter (guide) 4 x stepped filter (wavefront) SLAC / Spanish group (same as DECam) J. Silber 09/09/2014 CD-1 Review 16

Illuminated Fiducials • • • Optical point sources, similar size as fiber positioners. Precisely surveyed with respect to mechanical datums. Pattern constrains FVC measurement against optical distortions and mechanical deformations. (DESI-0485) Fiducial Blue dots: fiducials which replace fiber positioners. Fiber positioner Red dots: “free”. J. Silber 09/09/2014 CD-1 Review 17

Focal Plate Petal Assembly (10 x) 9 x Service Rails Arrays of identical, alternating, fiber and electrical breakouts. Fiber Cable 42 x Fiber Furcation Tubes 9 x flex cables serve breakouts 42 x Fiber / Wire Fanouts Each serves 12 pos. Cold plate here if needed Power Supply Fiber Spool Box Positioner Ext. Electronics Petal J. Silber 09/09/2014 500 x Fiber Positioner Envelopes CD-1 Review Illuminated Fiducial GFA Assembly GFA Ext. Electronics 18

FVC (Fiber View Camera) Focal Plate Assembly Test plate of backlit fibers. J. Silber 09/09/2014 FVC measures centroids. CD-1 Review Yale test camera. 19

Focal Plane Requirements Doc SRDB ID Requirement Value Rationale Verif. Method DESI-0455 IN. FPA-20008 Focal Plate Z Deflection ≤ 15 μm RMS DESI-0315 Analysis DESI-0455 IN. FPA-20102 Positioner XY Error ≤ 5 μm RMS DESI-0347 Test DESI-0455 IN. FPA-20106 Reconfiguration Time ≤ 45 seconds DESI-0315 Test DESI-0455 IN. FPA-20107 Positioner Lifetime ≥ 372, 000 DESI-0584 Test DESI-0455 IN. FPA-20115 Fiber Z Error in Positioner ≤ 20 μm DESI-0347 Inspection DESI-0526 IN. AATP-40000 GFA Guide Accuracy ≤ 0. 03 arcsec DESI-0315 Analysis, Test DESI-0526 IN. AATP-40008 GFA Defocus Measurement ≤ 30 μm RMS DESI-0347 Analysis, Test DESI-0589 IN. AATP-40103 FVC Measurement Accuracy ≤ 3 μm RMS DESI-0315 Test DESI-0589 IN. AATP-40107 FVC Cycle Time DESI-0315 Test ≤ 5 seconds Some key requirements are shown in table above. DESI-0455 Complete list (53 items) of FPA requirements. DESI-0526 Complete list (13 items) of GFA requirements. DESI-0589 Complete list (10 items) of FVC requirements. J. Silber 09/09/2014 CD-1 Review 20

Focal Plane Production • WBS 1. 4 “Focal Plane System (FPS)” — J. Silber (LBNL), BO 1. 3 — Focal Plate Structure — Thermal Enclosure — Fiber Positioners — Guide/Focus/Alignment cameras — Fiber View Camera — Illuminated Fiducials J. Silber 09/09/2014 CD-1 Review 21

Who puts opto-mech together. P 7 Flaugher BO 1. 4 Besuner J. Silber 09/09/2014 CD-1 Review 22

How do we put a fiber on a galaxy. BO 1. 3 Silber BO 2. 3 Honscheid J. Silber 09/09/2014 CD-1 Review 23

Summary • • • Corrector, opto-mech, and focal plane instrument have well-defined technical requirements. The design concept that meets those requirements is well-understood. Corrector — Corrector optical design is done and has been successfully reviewed by independent experts. — Direct heritage from successful DES corrector, with a very similar design and the same personnel. — Clear sequence of events, taken largely from DES experience of FNAL and UCL experts. Detailed coordination with KPNO has been ongoing from the beginning of the project. Focal plane — Full scale prototype for the focal plate petal structure has been designed, built, and tested. — 24 successive prototypes for the fiber positioner have been designed, built, and tested. Production ready. Formerly high technical risk has been retired. — Guide / focus / alignment cameras hardware and software by DECam group. — Clear understanding of how to put fibers on targets. J. Silber 09/09/2014 CD-1 Review 24