CIV Vacuum Ultraviolet Fabry-Perot Interferometer for Solar Research |
|
G. Allen Gary Submitted: 2006-10-16 18:14
A tunable, high spectral resolution, high effective finesse, vacuum ultraviolet (VUV) Fabry-Perot interferometer (FPI) is described for obtaining narrow-passband images, magnetograms, and Dopplergrams of the transition region emission line of CIV (155nm). The integral parts of the CIV narrow passband filter package (2-10pm FWHM) consists of a multiple etalon system composed of a tunable interferometer that provides high-spectral resolution and a static low-spectral resolution interferometer that allows a large effective free spectral range. The prefilter for the interferometers is provided by a set of four mirrors with dielectric high-reflective coatings. A tunable interferometer, a VUV piezoelectric-control etalon, has undergone testing using the surrogate F2 eximer laser line at 157nm for the CIV line. We present the results of the tests with a description of the overall concept for a complete narrow-band CIV spectral filter. The fixed-gap interferometer of the filter is envisioned as being built using the coating-test MgF2 plates after being superpolished and recoated. The four-mirror prefilter would have dielectric multilayer Pi-stacks following the design concept used in the Ultraviolet Imager of NASA's Polar Spacecraft. A dual etalon system allows the effective free spectral range to be commensurate with the prefilter profile. With an additional etalon, a triple etalon system would allow a spectrographic resolution of 2pm. The basic strategy has been to combine the expertise of spaceflight etalon manufacturing with VUV coating technology to build a VUV FPI which combines the best attributes of imagers and spectrographs into a single compact instrument. Spectro-polarimetry observations of the transition region CIV emission will allow an increased understanding of the magnetic forces, mass motion, evolution, and energy release within the solar atmosphere at the base of the corona where mainly the magnetic field is approximately force-free. The 2D imaging of the full vector magnetic field at the height of maximum magnetic influence (minimum plasma beta) can be accomplished, albeit difficult, by measuring the Zeeman splitting of the CIV resonance pair. Our designs of multiple VUV FPIs are being developed to integrate within the future orbiting solar observatories to obtain the necessary CIV observations.
Authors: G. Allen Gary, Edward A. West, David Rees, Jack McKay, Maumer Zukic, and Peter Herman
Projects: None
|
Publication Status: Accepted/Forthcoming
Last Modified: 2006-10-17 10:57
|
 
 
 
 
|
|