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Instrumentation for Extremely Large Telescopes

Instrumentation for Extremely Large Telescopes. Hubert of Liege 656-727. Patron Saint of: Hunters Archers Liege, Belgium Forest Workers Precision Instrument Makers Machinists Mad Dogs. Production and Use of VPH Gratings.

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Instrumentation for Extremely Large Telescopes

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  1. Ringberg Castle 2005

  2. Instrumentation for Extremely Large Telescopes Hubert of Liege 656-727 • Patron Saint of: • Hunters • Archers • Liege, Belgium • Forest Workers • Precision Instrument Makers • Machinists • Mad Dogs Ringberg Castle 2005

  3. Production and Use of VPH Gratings Purpose: To relate our experiences with VPH gratings in the Goodman Laboratory to builders of instrumentation for ELTs. • VPH Grating Design • VPH Grating Production • VPH Gratings in the Goodman Spectrograph Ringberg Castle 2005

  4. Volume Phase Holographic (VPH) Gratings Under the geometry pictured, the Bragg condition is: , where m is the integer order, l is the wavelength, L is the grating period, n is the refractive index, and a is the incident angle Ringberg Castle 2005

  5. More Generally… Courtesy Sam Barden Ringberg Castle 2005

  6. Designing a Grating Ringberg Castle 2005

  7. Goodman Laboaratory Design Software Ringberg Castle 2005

  8. VPH Manufacturing Facilities Ringberg Castle 2005

  9. Multiplex VPH Design Ringberg Castle 2005

  10. VPHs in use:The Goodman Spectrograph

  11. Standard Features All-refracting imaging spectrograph operating from 320 to 850 nm 5' x 5' imaging field with 0.146"/pixel sampling R = 900 to 9,000 (3 pixel sampling) at full throughput Maximum R = 14,000 (2 pixel sampling) at lower throughput Multi-slit mask and atmospheric dispersion corrector option for multi-object spectroscopy of 100 targets in 3' x 5' field Ringberg Castle 2005

  12. Challenging Specifications Articulated camera (90 deg) to use transmission VPH gratings Flexure limit of 1/10 pixel for 360 rotation at Nasmyth Image degradation < 0.16”, broadband, at field corners Imaging throughput maximum of 75%, inclusive of CCD (68% at 350 nm). Spectroscopic throughput maximum of 65%, inclusive of CCD (50% at 350 nm) Ringberg Castle 2005

  13. Construction Photos Ringberg Castle 2005

  14. Delivered June 2004 Ringberg Castle 2005

  15. Flexure Tests Ringberg Castle 2005

  16. First Lab Image Ringberg Castle 2005

  17. Conclusion: VPH gratings offer advantages in size, efficiency, scattered light, but not without introducing some new difficulties… Ringberg Castle 2005

  18. Extra mechanical or optical complexity • Mitigated by “dual purpose” articulation • Vendors Limited • Kaiser Optical Systems Inc. (75 mm max) • Ralcon (now Wasatch Photonics) • Centre Spatial de Liege (CSL) • Manufacturing Problems • Curved substrates due to glue shrinkage (KOSI) • Wrong Line Density (KOSI) • Coatings Removed (RALCON) • Bandwidth-efficiency variations across pupil (everybody) • Who knows? • Film Limitations • Maximum index modulation ~0.1 • Absorption in UV/IR Ringberg Castle 2005

  19. Ringberg Castle 2005

  20. The Goodman Spectrograph Deployment

  21. Ringberg Castle 2005

  22. Optical Components in Chapel Hill Ringberg Castle 2005

  23. Mechanical Components in Chapel Hill Ringberg Castle 2005

  24. Shipping and Receiving Ringberg Castle 2005

  25. In the Gemini Labs Ringberg Castle 2005

  26. Into the SOAR Nasmyth Cage Ringberg Castle 2005

  27. To the Mountain La Salchicha Grande Ringberg Castle 2005

  28. Waiting….. Ringberg Castle 2005

  29. First Light Ringberg Castle 2005

  30. Problems

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