AN EVALUATION OF MULTILAYER MIRRORS FOR THE SOFT-X-RAY AND EXTREME-ULTRAVIOLET WAVELENGTH RANGE THAT WERE IRRADIATED WITH NEUTRONS

The Plasma Spectroscopy Group at the Johns Hopkins University develops high photon throughput multilayer mirror (MLM) based soft x ray and e xtreme ultraviolet (XUV 10 Angstrom<lambda<Angstrom<304 Angstrom) spec troscopic diagnostics for magnetically confined fusion plasmas. The D- T reactions in large fusion reactor type devices such as the Internati onal Thermonuclear Experimental Reactor will produce neutrons at a rat e as high as 5x10(19) n s(-1). The MLMs, which are used as dispersive and focusing optics, will not be shielded from these neutrons. In an e ffort to assess the potential radiation damage, four MLMs (No. 1: Mo/S i, d=87.8 Angstrom, Zerodur substrate with 50 cm concave spherical cur vature; No. 2: W/B4C, d=22.75 Angstrom, Si wafer substrate; No. 3: W/C , d=25.3 Angstrom, Si wafer substrate; and No. 4: Mo/Si, d=186.6 Angst rom, Si wafer substrate) were irradiated with fast neutrons at the Los Alamos Spallation Radiation Effects Facility (LASREF). The neutron be am at LASREF has an energy distribution that peaks at 1-2 MeV with a t ail that extends out to 100 MeV. The MLMs were irradiated to a fast ne utron fluence of 1.1x10(19) n m(-2) at 270-300 degrees C. A comparison between the dispersive and reflective characteristics of the irradiat ed MLMs and the corresponding qualities of control samples will be giv en. (C) 1997 American Institute of Physics.