Multilayer mirrors and filters for imaging the earth's inner magnetosphere

The authors present guidelines for the performance of multilayer mirrors and filters for imaging the earth's inner magnetosphere by isolating the 304-A He+emission. The analysis shows that the combination of filters and multilayer mirrors for an inner magnetosphere imager must attenuate the 1226-A Lyman α emission by six orders of magnitude and the 584-, 834-, and 1026-A background emissions by three orders of magnitude relative to the 304-A signal. Multilayer mirrors with the highest possible reflectance at 304 A are needed to preserve as much of the low-intensity 304-A signal as possible. The design of multilayer mirrors is discussed, and the results of an exhaustive computer search for the best multilayer mirror design for 304-A radiation are presented and analyzed. The theoretical performance of these new multilayer mirror designs is significantly better than th of designs currently used for imaging the solar 304-A emission. Promising materials for normal-incidence multilayer mirrors for 304-A radiation are B4C, Be, Si, or SiC used with Al, Mg, or Mg2Si. Promising materials for a filter for this application are Te passivated with Si, or a combination of Al or Si with B or C