Lithium promises to give refractive x-ray optics the highest possible
transmission, aperture and intensity gain. Room-temperature embossing of lithium with parabolic dies from polypropylene produces lenses that focus well but are not yet good enough for imaging. X-ray measurements suggest two causes of problems, one of which one can be solved easily.
Lithium is the best material for refractive x-ray lenses, with peak performance around 8 keV. To date we have built a prototype of Cederstrom's so-called alligator lens, and have tested the lens with beamline 7ID's 10 keV x-rays on the Advanced Photon Source at Argonne National Laboratories. To date we have attained only a threefold gain, most likely limited by surface roughness that is avoidable with more careful manufacturing techniques.
Work begun in 1986 has continued on the reflex-diode oscillator mounted on one of the four Aurora $OM10-MV, $OM22-(Omega) pulse lines. This is a preliminary report on the most recent work, which extracted microwaves radially into 18 rectangular WR-975 waveguides around the virtual cathode. Two additional arms upstream of the anode extracted microwaves around the real cathode. Vestigial-loop, waveguide directional couplers measured the radially extracted microwave energy. The output is typically 50 to 100 J/arm, for the frequencies between 0.6 and 1.0 GHz. Effects were compared from two cathode tips differing by a factor of $OM2 in diameter. Additional parameter variations have included the anode/cathode spacing and the positioning of a second foil.
A reflex diode operating from 1 to 8 GHz is powered by the TEMPO pulser at Harry Diamond Laboratories. High-power microwave (HPM) pulses (60 ns FWHM) are radiated into a large anechoic chamber. These pulses are monitored with waveguide rf couplers, and open-ended waveguide. Two configurations of the reflex diode are compared. The configurations differ by the polarity of the applied voltage pulse. These two configurations are studied experimentally and numerically, using the particle-in-cell code MAGIC.
Work begun in 1986 is continuing on the reflex-diode oscillator mounted on one of the Aurora 10-MV 22- ci pulsers. The most recent work extracted microwaves radially into six rectangular WR-975 waveguides at the virtual cathode and into two additional arms a few meters downstream. Two of the waveguides were open-ended and radiated into an anechoic chamber. Diagnostics for radially extracted microwave energy included directional couplers card calorimeters and free-field sensors. The peak output is ''-50 3 per arm for the frequencies below 1. 0 (3Hz. Parameter variations have included the anode/cathode spacing and the positioning of a second anode foil. Dosimetry and electric field measurements were made to study beani dynamics in the drift region. Thus far the measurements suggest that our virtual cathode is weak. 1.