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28-nm laser damage testing of LIF

Description: We have tested several samples of LIF, both single crystal and press forged, for damage resistance to 10-ns 248-nm pulses at 35 pps. The damage thresholds - the highest levels at which no damage could be produced - ranged from 4 to 6 J/cm/sup 2/ although some test sites survived irradiation at approx. 30 J/cm/sup 2/. We observed that bulk damage is the primary failure mechanism in single crystal and press forged samples and that both types exhibit the same resistance to laser damage.
Date: January 1, 1981
Creator: Foltyn, S.R. & Newman, B.E.
Partner: UNT Libraries Government Documents Department

Predamage threshold electron emission from insulator and semiconductor surfaces

Description: Predamage electron emission shows a dependence on fluence, bandgap and wavelength consistent with multiphoton excitation across the bandgap and inconsistent with avalanche ionization and thermionic emission models. The electron emission scales with pulselength as 1/..sqrt..T. 6 references, 8 figures, 1 table.
Date: February 5, 1985
Creator: Siekhaus, W.J.; Kinney, J.H. & Milam, D.
Partner: UNT Libraries Government Documents Department

Facilities for studying radiation damage in nonmetals during irradiation

Description: Two facilities have been developed for making optical absorption, luminescence and other measurements on a single sample before, during and after irradiation. One facility uses /sup 60/Co gamma rays and the other 0.5 to 3 MeV electrons from an accelerator. Optical relays function as spectrophotometers, luminescenc detectors, etc. All radiation sensitive components are outside of walk-in irradiation chambers; all measurement control and data recording is computerized. Irradiations are made at controlled temperatures between 5K and 900/sup 0/C. The materials studied include glasses, quartz, alkali halides (especially natural rock salt), organic crystals, etc. As determined from color center measurements the damage formation rate in all materials studied at 25/sup 0/C or above is strongly temperature dependent. The defect concentration during irradiation is usually much greater than that measured after irradiation. The fraction of defects annealing after irradiation and the annealing rate usually increases as the irradiation temperature increases. The completed studies demonstrate that, in most cases, the extent of maximum damage and the damage formation and annealing kinetics can be determined only by making measurements during irradiation.
Date: August 1, 1984
Creator: Levy, P.W.
Partner: UNT Libraries Government Documents Department

Review of ultraviolet damage threshold measurements at Lawrence Livermore National Laboratory

Description: The results of damage threshold measurements made at LLNL using ultraviolet wavelength laser pulses are reviewed. Measurements were made with pulses from a krypton fluoride laser with wavelength of 248 nm and pulse duration of 20 ns and with Nd-glass laser pulses converted to the third harmonic wavelength of 355 nm with duration of 0.6 ns. Measurements are presented for transparent window materials, crystals and harmonic generation, single layer dielectric films of oxide and fluoride materials and multilayer high reflectivity and antireflective coatings.
Date: January 1, 1984
Creator: Lowdermilk, W.H. & Milam, D.
Partner: UNT Libraries Government Documents Department

Damage thresholds of thin film materials and high reflectors at 248 nm

Description: Twenty-ns, 248-nm KrF laser pulses were used to measure laser damage thresholds for halfwave-thick layers of 15 oxide and fluoride coating materials, and for high reflectance coatings made with 13 combinations of these materials. The damage thresholds of the reflectors and single-layer films were compared to measurements of several properties of the halfwave-thick films to determine whether measurements of these properties of single-layer films to determine whether measurements of these properties of single-layer films were useful for identifying materials for fabrication of damage resistant coatings.
Date: January 1, 1982
Creator: Rainer, F.; Lowdermilk, W.H.; Milam, D.; Carniglia, C.K.; Hart, T.T. & Lichtenstein, T.L.
Partner: UNT Libraries Government Documents Department

Mechanical strength of low-temperature-irradiated polyimides: a five-to-tenfold improvement in dose resistance over epoxies

Description: Neutronics calculations by Engholm show that without additional shielding even the first fusion test reactors such as the Fusion Engineering Device will produce lifetime doses at magnet insulator locations that exceed the radiation tolerance of glass-fabric-filled (gff) epoxies now used. To explore the possible use of an alternative insulator, the mechanical strength of pure and recently available gff polyimides was studied as a function of gamma-ray irradiation at 4.9 K to 100 MGy (10/sup 10/ rads). After a postirradiation anneal at 307/sup 0/K the flexure and compressive strengths of the gff materials measured at 77/sup 0/K were reduced by up to 40% for 100 MGy while the pure material changed little. Testing done at 300/sup 0/K gave similar results, but all stress values were about 40% less. Compared to earlier epoxy studies we find that, overall, the gff polyimides are 5 to 10 times more radiation resistant than comparably prepared gff epoxies.
Date: June 1, 1981
Creator: Coltman, R.R. Jr. & Klabunde, C.E.
Partner: UNT Libraries Government Documents Department

PINEX (Pinhold Neutron Experiment) fluor characteristics

Description: This report will describe recent experiments to characterize four fluors: BC-400, 408, 422, 430. Each fluor sample was 0.5 cm thick commensurate with our standard Electronic Pinhole Neutron Experiment (EL-PINEX) fluors. The important results are that the neutron-gamma sensitivity ratios did not change significantly, although the absolute gamma and neutron sensitivities decreased. 6 figs., 4 tabs.
Date: July 1, 1988
Creator: Koehler, H.; Kammeraad, J.; Davis, B. & Burns, E.
Partner: UNT Libraries Government Documents Department