Photomultiplier window materials under electron irradiation: fluorescence and phosphorescence

Journal Article · Mon Sep 01 04:00:00 EDT 1975 · Appl. Opt., v. 14, no. 9, pp. 2104-2115

DOI:https://doi.org/10.1364/AO.14.002104· OSTI ID:4192105

Viehmann, W; Eubanks, A G; Pieper, G F; Bredekamp, J H

The fluorescence and phosphorescence of photomultiplier window materials under electron irradiation have been investigated using a Sr$sup 90$--Y$sup 90$ beta emitter as the electron source. Spectral emission curves of uv-grade, optical-grade, and electron-irradiated samples of MgF$sub 2$ and LiF, and of CaF$sub 2$, BaF$sub 2$, sapphire, fused silica, and uv-transmitting glasses were obtained over the 200--650-nm spectral range. Fluorescence yields, expressed as the number of counts in a solid angle of 2$pi$ sr/MeV of incident electron energy deposited MeV$sup -1$ (2$pi$ sr)$sup -1$, were determined on these materials utilizing photomultiplier tubes with cesium telluride, bialkali, and trialkali (S- 20) photocathodes, respectively. Typical yields observed with a uv/visible sensitive bialkali cathode range from 10 MeV$sup -1$ (2$pi$ sr)$sup -1$ for uv- grade MgF$sub 2$ to approx. =200 MeV$sup -1$ (2$pi$ sr)$sup -1$ for CaF$sub 2$. For comparison, sodium-activated cesium iodide, one of the most efficient scintillator materials, yields about 700 MeV$sup -1$ (2$pi$ sr)$sup -1$. High- purity fused silica has the lowest yield, approximately 6 MeV$sup -1$ (2$pi$ sr)$sup -1$. Optical-grade MgF$sub 2$ and LiF, as well as electron-irradiated uv- grade samples of these two materials, show enhanced fluorescence due to color- center formation and associated emission bands in the blue and red wavelength regions. Large variations in fluorescence intensities were found in uv-grade sapphire samples of different origins, particularly in the red end of the spectrum, presumably due to various amounts of chromium-ion content. Phosphorescence intensity expressed as a fraction of the steady-state fluorescence intensity is an extremely sensitive measure of crystalline perfection and purity. This fraction ranges from a high of approx. =10$sup -2$ for some fluoride samples to a low of less than or equal to2times10$sup -6$ for fused silica.

• Research Organization: NASA Goddard Space Flight Center, Greenbelt, Maryland 20771
• NSA Number: NSA-33-000801
• OSTI ID: 4192105
• Journal Information: Appl. Opt., v. 14, no. 9, pp. 2104-2115, Journal Name: Appl. Opt., v. 14, no. 9, pp. 2104-2115; ISSN APOPA
• Country of Publication: United States
• Language: English

Related Subjects

*PHOTOMULTIPLIERS-- WINDOWS
440200* --Instrumentation--Radiation Effects on Instrument Components
Instruments
or Electronic Systems
ELECTRONS
EMISSION SPECTRA
FLUORESCENCE
N46300* --Instrumentation--Radiation Effects on Instrument Components
Instruments
or Electronic Systems
ORBITING SOLAR OBSERVATORIES
PHOSPHORESCENCE