Note: Thermally stable thin-film filters for high-power extreme-ultraviolet applications.

We investigated several types of thin-film filters for high intensity work in the extreme-ultraviolet (EUV) spectral range. In our application, with a peak EUV intensity of 2.7 W cm(-2), Ni-mesh-backed Zr filters have a typical lifetime of 20 h, at which point they suffer from pinholes and a 50% loss of transmission. Initial trials with Si filters on Ni meshes resulted in rupture of the filters in less than an hour. A simple thermal calculation showed that the temperature rise in those filters to be about 634 K. A similar calculation indicated that using a finer mesh with thicker wires and made of Cu reduces the temperature increase to about 60 K. We have exposed a Si filter backed by such a mesh for more than 60 h with little loss of transmission and no leaks.

Elimination of current dissipation in high transition temperature superconductors.

The relaxation of the shielding current-induced magnetic moment in YBa(2)Cu(3)O(7) thin films, which were grown in situ, is studied as a function of temperature. Although typical relaxations cause a large amount of decay in the magnetic shielding current (on the order of 10 to 20 percent for the first 1000 seconds), it is shown that this is not necessarily a serious problem for applications such as magnets operating in persistent-current modes. This is because the decay of the magnetic shielding current depends sensitively on how far away the operating current density is from the critical current density J(c). By using a quenching process the shielding current is reduced slightly below J(c) and the relaxation is dramatically reduced. A general relation between the relaxation rate at J(c) and the reduction of the relaxation rate upon lowering of the operating current is obtained and is shown to be consistent with experimental data.