Large Optical Window Research Articles

Visible and Infrared Absorption Spectra of Uranium Dioxide

The absorption spectra for single crystal and polycrystalline UO/sub 2/ were measured between 0.6 and 15 mu at room temperature. The spectrum for UO/ sub 2/ resembles that of a typical semiconductor, opaque in the visible but transparent over a large portion of the infrared. The absorption edge is located at approximately 0.6 mu (2.0 ev). A large optical window extends from 3 to 13 mu . The absorption coefficient for single crystal UO/sub 2/ was determined between 1.5 and 15 mu . A maximum value of 57 cm/sup -1/ was measured at 1.70 mu with minimum values of 6 cm/sup -1/ at 2.75 and 8 mu . The absorption coefficient of polycrystalline UO/sub 2/ at wavelengths less than 8 mu is estimated to be ten times larger than for single crystal UO/sub 2/. (auth)

Inflatable Gasket for the 72-In. Bubble Chamber

A satisfactory glass-to-metal seal at liquid hydrogen temperatures has been developed for the large oval-shaped optical window of the 72-in. liquid hydrogen bubble charaber. Indian wire is held in contact with the character glass by an inflatable stainless steel member capable of 160 mils useful deflection. During cooldown to liquid hydrogen temperatures, the stainless steel chamber shrinks about 3/18 inmore than the glass. causing a relative translation between the contacting surfaces. To avoid opening leaks, the gasket is not sealed until the cooldown is nearly completed. Only a nominal inflation pressure ( approximately 50 psig) is used during the cooldown, enough to keep the assembled parts in position without mashing the indium. At about 77 deg K, after most of the relative shrinkage has occurred, the inflation pressure is increased to between 400 and 600 psig, mashing the indium and making the real. With a double row of indium wires, the bearing stress on the glass is only approximately 800 psi at an inflation pressure of 400 psig. Since the BSC-517/ 645 glass should be able to withstand a compressive stress on the order of 10,000 psi for this gasket geometry, an adequate margin of safety should exist. Because amore » multiplicity of seals with pumpcuts between each seal is used, it is not necessary that each seal be tight to a helium leak detector as long as the vacuum pumps can handle the leaks. In practice it was found that after an initial period of chamber pulsing the seal improves. A vacuum in the range of 10/sup -5/ to 10/sup -6/ mm Hg can be held above the glass, with a liquid pressure below the glass varying from 95 to 30 psig. Pressures in the chamber-side and glass-side pumpouts vary from 10 mu to 1000 mu , and in the glass-edge pumpout the pressure is about 50 mu . During the first liquid hydrogen operation the chamber was cycled from room temperature to low absolute temperatures (27 deg K) three times with the same set of gaskets. (auth)« less