Material considerations in the microfabrication of grating microstructures for use in a laser-powered linear accelerator

Collaborative work between Brookhaven and Los Alamos National Laboratories is developing a new type of linear accelerator that uses a high-ower, a picosecond pulse CO/sub 2/ laser toirradiate a specialized form of grating with a pitch of 10.6 microns. The electromagnetic field that results can be used to accelerate electrons at field gradients of several GeV/m with potential efficiencies much better than current accelerators. The grating must be conductive to minimize resistive looses, be able to withstand high fields without damage, and requires dimensional tolerances in the sub-micron range. These requirements focus attention on grating material selection, microfabrication methods, and metrological methods used for quality control. At present, several types of gratings have been manufactured by reactive ion etching of fused silica in CHF/sub 3//Ar or etching silicon with KOH/H/sub 2/O or ethylenediamine-pyrocatechol solutions. Metrological analysis of the gratings has begun with a Tracor Northern 5700 digital image analyzer