This paper discusses a derivation of the scan impedance for a phased array consisting of arbitrarily oriented planar elements with arbitrary current distribution located in a general stratified media. It is shown that the scan impedance will remain scan independent if and only if the product of the element power pattern and the transformation function for the stratified dielectric media varies as the cosine to the scan angle. An entire class of scan independent phased arrays is def'med in this fashion. As simple examples of this class, we discuss arrays of slots or dipoles bounded by a single dielectric slab with e = 1.3. The scan impedance has VSWR < 1.5 for scan angles up to _+80 ø in both principal planes, and further improvements appear possible. These designs are quite different and superior to earlier phased array designs (Magill and Wheeler, 1966;Campbell and Popovich, 1972;Chen, 1973).

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The conversion efficiency into kilovolt line radiation for 248-nm light at 1017 W/cm2 on an aluminum target is measured. The x-ray yield is found to increase with the scale length of the target plasma. The interaction is modeled as resonance absorption, and the plasma scale length is determined from the prelase energy and irradiance.

We have studied the interaction of 290-fs, 308-nm laser pulses with aluminum targets at irradiances exceeding 5×1018 W/cm2. The x-ray spectrum is dominated by the H- and He-like lines from aluminum, with the brightest lines radiating 0.8% of the incident laser light energy. This fraction is close to that measured at 50 times less irradiance, but occurs at a slightly higher ionization stage. The x rays are emitted from a region of subcritical electron density at 3–6×1021 W cm−3. The radiance of the 1.73-keV Lα line is measured to be 4×1012 W/cm2/sr.

Absfmcf-The mutual admittance method i s used to calculate the transmission through a two layer array of slots. The slot arrays are thin and parallel. The plane wave illumination is at an arbitrary angle in either the E-plane or the H-plane. The mutual admittance between two slot antennas, either in the same or M e r e n t planes, is derived. In this derivation it is assumed that the slots are small enough so that when short-circuited at their terminals the electric field scattered from the slot is negligible. The evaluation of the mutual admittance sums is simpE6ed by the extension to the slot case of certain impedance relationships established previously for a two-layer dipole array. For many applications the two-layer slot array is more desirable than a single-layer array since a wider passband and sharper skirts can be obtained with proper design.The analysis shows, however, that for high incidence angles the dip in the center of the passband may be deeper than for the similar two-layer dipole array.