Silver has the highest reflectance of all of the metals, but it tarnishes in the presence of sulfides, chlorides, and oxides in the atmosphere. Also, the silver reflectance is very low at wavelengths below 400 nm making aluminum more desirable mirror coating for the UV region. We have found a way to prevent silver tarnishing by sandwiching the silver layer between two thin layers of NiCrN x , and to extend the metal's high reflectance down to 200 nm by depositing the (thin) Ag layer on top of Al. Thus, the uv is transmitted through the thin Ag layer below 400 nm wavelength, and is reflected from the Al layer underneath. This UV-shifted durable coating 1 provides a valuable alternative to the aluminum coating for telescope mirror coatings where high throughput and durability are important considerations. The throughput for a telescope with, say, six reflections from silver coatings is (0.97) 6 = 83% compared to (0.92) 6 = 60% for aluminum coatings, or 28% less. The use of silver coatings allows more photons to be collected by primary mirror. Aluminum also has a reflectance dip at 850 nm caused by inter-band transitions which is eliminated by placing the thin Ag layer on top. This paper describes a nontarnishing silver coating having high reflectance down into the UV region. The average specular reflectance is 70% -97% in the near-UV, 95% -99% in the visible region, and ≥ 99% in the infrared region covering the total wavelength range 200 nm to 10,000 nm. Figure 1 compares the reflectance of our UVHR-LLNL silver coating to bare silver and aluminum overcoated with magnesium fluoride over the wavelength range 300 nm to 2000 nm.
The use of sounding rockets for calibrating solar cells offers two principal advantages:(1) there is no effect due to the terrestrial atmosphere and (2) the cells are recoverable immediately after calibration. On 18 September 1974, four n/p photovoltaic cells were calibrated in space and successfully recovered from a NASA Aerobee rocket that reached a peak altitude of 251 km. Two of the cells were optically filtered with 0.6 to 0.9 -p bandpass filters.The short -circuit current agreed to within 4% of the laboratory calibration; variation of cell output due to atmospheric attenuation in the altitude range of 80 to 251 km was 0.4% for the unfiltered cells.
A durable protected silver coating'x' was designed and fabricated for possible use on flashlamp reflectors in the National Ignition Facility (NE!) to avoid tarnishing under corrosive conditions and intense visible light (10 J/cm', 360 p). This coating provides a valuable alternative for mirror coatings where high reflectance and durability are important requirements. This paper describes a protected silver coating having high reflectance from 400 mn to 10,000 nm. The specular reflectance is between 95% and 98% in the visible region and 98% or better in the infked region.
Sputtered -sliced transmissive x -ray zone plates consisting of concentric rings of Al and Cu have been fabricated and tested using the 8.04 keV k -a line from Cu. Due to the need for high aspect ratios for this 1.54 A radiation, magnetron sputtering onto a rotating opaque central wire was chosen as the fabrication method. Both the fabrication technology and initial results are presented.
AbstractSputtered-sliced transmissive x-ray zone plates consisting of concentric rings of Al and Cu have been fabricated and tested using the 8.04 keV k-a line from Cu. Due to the need for high aspect ratios for this 1.54 A radiation, magnetron sputtering onto a rotating opaque central wire was chosen as the fabrication method. Both the fabrication technology and initial results are presented.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.