Fused Silica Windows Research Articles

Periscope-camera system for visible and infrared imaging diagnostics on TFTR

An optical diagnostic consisting of a periscope which relays images of the torus interior to an array of cameras is used on the Tokamak Fusion Test Reactor (TFTR) to view plasma discharge phenomena and inspect the vacuum vessel internal structures in both the visible and near-infrared wavelength regions. Three periscopes view through 20-cm-diam fused-silica windows which are spaced around the torus midplane to provide a viewing coverage of approximately 75% of the vacuum vessel internal surface area. The periscopes have f/8 optics and motor-driven controls for focusing, magnification selection (5°, 20°, and 60° field of view), elevation and azimuth setting, mast rotation, filter selection, iris aperture, and viewing port selection. The four viewing ports on each periscope are equipped with multiple imaging devices which include: (1) an inspection eyepiece, (2) standard (RCA TC2900) and fast (RETICON) framing rate television cameras, (3) a PtSi CCD infrared imaging camera, (4) a 35-mm Nikon F3 still camera, or (5) a 16-mm Locam II movie camera with variable framing rate up to 500 fps. Operation of the periscope-camera system is controlled either locally or remotely through a computer-CAMAC interface. A description of the equipment and examples of its application are presented.

Bulk And Surface Damage Thresholds Of Crystals And Glasses At 248 nm

We used 20 ns, 248 nm pulses to study surface and bulk damage in bare, polished samples of UV-transmitting glasses, fluoride crystals, and isomorphs of potassium dihydrogen phosphate (KDP). The intent was to test enough samples to establish the safe operating limits for currently available windows and crystals finished by routine techniques for optical fabrication. In fluoride crystals, thresholds for bulk inclusion damage and for rear-surface damage were comparable. The median rear-surface threshold was 16 J/cm2. The fluence limit in fused silica windows was determined by the threshold for rear-surface damage, which ranged from 5 to 9 J/cm2. For the isomorphs of KDP, the limiting fluence was the threshold for front-surface damage, which ranged from 3 to 9 J/cm2.

Index of refraction of shock-compressed fused silica and sapphire

Explicit relations between index of refraction and density are obtained for shock-compressed fused silica and sapphire. The relations are derived from the Doppler-frequency corrections to velocity-interferometry data obtained by Barker and Hollenbach in plate-impact experiments. The index-density relation for sapphire was found using an expression for the Doppler-frequency shift produced by a window material experiencing shock compression. For fused silica, a numerical calculation was required to compute frequency corrections for the combined ramp/shock waveforms produced in the experiments. In both cases the behavior of the refractive index over the density range of the data was found to be predicted quite accurately by adding a correction term to the Gladstone-Dale relation. A particular power-law dependence on density was found for this correction term in each case. The explicit index-density relations permit detailed calculations to be made for index-of-refraction effects from window materials in plate-impact experiments using velocity interferometry. As an example, refractive-index effects are calculated for a fused silica window experiencing a slowly rising compression wave generated in a glass-ceramic material. The present results also permit the polarizability behavior of these materials under shock compression to be examined.

Vacuum ultraviolet absorption spectra of oxygen in liquid and crystalline argon and nitrogen

The ultraviolet absorption spectra of oxygen have been observed in liquid and solid media at low temperature. By freezing slowly from the liquid phase, samples of crystalline argon and nitrogen were prepared with added amounts of oxygen ranging between 0.01% and 10%. The spectra were recorded photo-electrically, through fused silica windows, over the wavelength range from 1750 to 2900 Å. The Schumann-Runge bands of oxygen ( B 3 Σ u − ← X 3 Σ g − , 1750 to 2000 Å) were observed in solid and liquid mixtures of oxygen in argon or nitrogen at concentrations less than 5%, over the temperature range 60 to 90°K. The bands are broad, with half-intensity width of 150 to 550 cm −1 and show no structure. The bands show a slight shading toward the violet in contrast to the bands in the gas phase, and are displaced toward lower frequencies by 50 to 400 cm −1 as compared with the positions in the gas phase. These shifts appear to be slightly dependent upon temperature. The changes in position or shape of the bands between liquid and solid or between argon and nitrogen media are remarkably small. At concentration of oxygen above 5% the Herzberg bands of oxygen ( A 3 Σ u + ← X 3 Σ g − ) were observed in the region 2400 to 3000 Å. These bands are also broad (200 to 600 cm −1) and show some partially resolved structure. No differences were observed for changes either in temperature or matrix material.

Astronomical Instrumentation for Project Polariscope.

view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Astronomical Instrumentation for Project Polariscope. Teska, T. M. ; Pellicori, S. F. ; Roland, E. H. Abstract A 28-inch balloon-borne telescope with a Wollaston prism polarimeter is to be flown during the winter of 1963-64 in order to make observations in the ultraviolet between 3000 and 2000 A (Gehrels and Teska, AppI. opt. 2, 67,1963). The Wollaston-type prism is constructed of ammonium dihydrogen phosphate (ADP). The prism tises a 250 angle of cut with the halves of the prism contacted with a silicone fluid. Since the birefringent material used for construction is fragile, the prism is sealed in an insulated cell having high thermal mass. This cell is provided with fused silica windows. The transmission of each of the optical beams slowly drops from 70% at 3000 A to 30% at 1950 A for the 40-mm length of prism used. Tentative filters having widths of about 200 A have been constructed and tested. The filters are dyed silicone fluids mounted between silica windows and cast in an epoxy cell. The filter materials used are p-dimethylaminobenzaldehyde and 2-methyl- pyrazine. The filters are transparent above 3500 A and must be used with "solar-blind" photocathodes such as cesium telluride. The photomultiplier outputs are integrated using transistorized versions of the Weitbrecht Mark-Six system. A single-ended electrometer-tube input stage is followed by a silicon field-effect transistor which drives the output stages of the amplifier. The amplifier is temperature compensated for low zero drift consistent with a readout resolution of one part in 4000. Dry-reed relays are used for capacitor switching. For testing of components in the laboratory, a number of optical modules can be bolted together in various serial arrangements. The individual modules are a monochromator, a collimator, a reference detector, a goniometer table, ai~ ADP Glan- Thompson polarizing prism, a telescope, and a detector. This test instrument is rigidly constructed to allow it to be mounted on the Polariscope telescope for polarimeter calibration. Publication: The Astronomical Journal Pub Date: 1963 DOI: 10.1086/109054 Bibcode: 1963AJ.....68Q.295T full text sources ADS |