|
FUV FILTERS
Each of the five UVI filters are comprised of three
reflective and one transmissive element. Each element is a dielectric
multilayer stack. The design of the filters results in a significant
reduction of the visible light passing through while maintaining
a high throughput for the wavelengths of interest. The wavelengths
short of the region of interest are primarily absorbed by the
materials in the dielectric stack and/or the transmissive element.
The wavelengths long of the region of interest are primarily
absorbed by the substrate on the reflective elements. For more
information on the filter design, refer to the following paper:
- Muamer Zukic, Douglas G. Torr, Jongmin Kim,
James F. Spann, and Marsha R. Torr, Filters for the International
Solar Terrestrial Physics Mission far-ultraviolet imager, Opt.
Eng., 32, 3069, 1993.
A significant effort was put forth in evaluating
materials to be used in the filters. Selection of materials is
difficult in the wavelength region from 115 nm to 200 nm because
of the limited number of materials which have are transmitting
(small extinction coefficient). Of those materials that are transmitting,
many are susceptible to radiation effects and become less transparent
when exposed. We conducted tests to determine which materials
are suitable for a radiation environment and provide a proper
high or low index of refraction required for the multilayer design.
For more information on the materials, refer the following three
papers:
- M. Zukic, D. G. Torr, J. F. Spann, and M.
R. Torr, Vacuum Ultraviolet Thin Films, Part I Optical Constants
of BaF2, CaF2, LaF3, MgF2, Al2O2, HfO2, and SiO2, Appl. Opt.,
29, 28, 4284, 1990.
- M. Zukic, D. G. Torr, J. F. Spann, and M.
R. Torr, Vacuum Ultraviolet Thin Films, Part II Vacuum Ultraviolet
All-Dielectric Narrowband Filters, Appl. Opt., 29,
28, 4293, 1990.
- Charles E. Keffer, Marsha R. Torr, Muamer
Zukic, James F. Spann, Douglas G. Torr, and Jongmin Kim, Radiation
Damage Effects in Far Ultraviolet Filters and Substrates, Appl.
Opt., 33, 6041, 1994.
The pioneering effort of the filter design
was headed by Dr. Muamer Zukic while at the Center
for Applied Optics at the University of Alabama in Huntsville.
He is currently a Research Scientist at Jaycor, Huntsville, AL,
phone: (256) 837-9100. The development of the filters was a joint
effort between the University of Alabama in Huntsville and the
Marshall Space Flight Center. The key individuals in this effort
were Dr. M. Zukic, Dr. J. F. Spann, Dr. Kim, and Dr. Charles Keffer.
Photographs
Filter
Performance
Because of the unique design of the UVI filters,
the required bandwidth and peak throughput is achieved. The filter's
performance allows the separation of various auroral emissions
for the first time using a 2 dimensional imager. The analysis
of various images taken with the filters allows for quantitative
assessment of the total energy flux into the auroral regions
and the characteristic energy. The peak wavelength and bandwidth
of each filter is listed below.
|
The
The
The
