WIYN Instrumentation: |
Project Team
M. Bershady - Project Scientist
Consultants: S. Barden, B. Schoening |
Contents | ||||
Description | Collimator | Spectrograph Layout | |||
Schedule | VPH Gratings | Throughput Budget | |||
Simulator | CCD | Beam Profile | |||
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This project is funded by the WIYN Consortium.
Figures and documents on this and related web
pages may not |
A GUI is available to optimize setups and calculate exposures for all gratings and fiber cables (calibrated with measured system throughput values where available; see Simulator). Modification of the camera-collimator angle (for conventional gratings) can optimize blaze-wavelength and anamorphic factors.
A more complete description can be found in our Sept 2003 report to the WIYN SAC and Board, which serves as our Concept Design.
The design is heavily constrained by the project-level requirement to keep the existing camera. The initial design consisted of a 3-element corrector with tilted elements (akin to the Wynne triplet, but using tilted, full spherical segments). A preliminary tolerance analysis showed the Bench implementation was likely unbuildable. The current off-axis design has 4 corrector elements and yields improved image performance than the existing on-axis design. Other considerations included:
The existing surface-relief grating suite for the WIYN Bench
Spectrograph delivers a wide range of coverage in wavelength and
resolution, as shown here in the left-hand figure. A completed Bench
upgrade may include a set of VPH gratings which replace or augment the
current capabilities of the existing gratings in this plane. Some
examples of possible VPH grating suites are shown in the
right-hand figure.
Two gratings resulting from the initial VPH effort, as contracted to Centre Spatial de Liege (CSL), will be part of the initial Bench Spectrograph upgrade: 740 l/mm and 3550 l/mm gratings. These are shown as red curves in the above, left figure. At this time, testing is underway on the 740 l/mm grating. The development is mature enough to offer the grating in Shared Risk mode for 2005B. We have taken delivery of a test-version of a small high-line-density grating (3300 l/mm). This was made on float glass and is not science grade. The high-density (3550 l/mm) science-grade vph grating is still under manufacture as of April 2005.
Grating Pages:
Grating Substrate | ||||||||||||||||
DCG parameters | physical aperture | clear aperture | ||||||||||||||
Grating Name | l/mm | (um) | dn | n=n2 | phi |
height (mm) | width (mm) | depth (mm) |
height (mm) | width (mm) | substrate
material | index n1=n3 |
grating man. | post-polish | coating | mount |
v740a | 740 | 17 14 effective | 0.03 | 1.43 | 0 | 220 219.46 |
240 239.55 |
24 24.55 |
200 | 211.5 | Diamant float glass; 2x12mm thick | ? | CSL | Yes; 2D Strehl of 0.7, 0th-order transmission; 2D Strehl of 0.1 for -1 order; LLNL | Yes; soft MgF2; KPNO | completed; KPNO |
v3300a CSL/WP3200 | 3300 | 12 | 0.048 | 1.43 | 0 | 120 | 170 | 24 | 100 | 150 | Diamant float glass; 2x12mm thick | ? | CSL | TBD | TBD | TBD |
v3550a CSL/WP4200 | 3550 | 6 pending | 0.10
pending | 1.5 pending | 0 | 230 | 500 | 30 | 210 | 480 | Zygo FS 7980 2F |
1.462 at 20 C and 1 atmos. | CSL | No | Yes; TBD | TBD |
Notes-
WARM images taken with eight of these are shown below. Note the left side of w10 and w11 are confused, and may be the same half-device - the bad column is exactly in the same place on both. These are all warm, relatively high illumination images - some things get better cold and others get worse.
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