Efficient Multi-keV X-Ray Sources from Ti-Doped Aerogel Targets

Abstract

We have measured the production of $h\ensuremath{\nu}\ensuremath{\approx}4.7\text{ }\text{ }\mathrm{keV}$ x rays from low-density Ti-doped aerogel ($\ensuremath{\rho}\ensuremath{\approx}3\text{ }\text{ }\mathrm{mg}/\mathrm{cc}$) targets at the OMEGA laser facility (University of Rochester), with the goal of maximizing x-ray output. Forty OMEGA beams (${\ensuremath{\lambda}}_{L}=0.351\text{ }\ensuremath{\mu}\mathrm{m}$) illuminated the two cylindrical faces of the target with a total power that ranged from 7 to 14 TW. The laser fully ionizes the target (${n}_{e}/{n}_{\mathrm{crit}}\ensuremath{\le}0.1$), and a laser-bleaching wave excites, supersonically, the high-$Z$ emitter ions in the sample. Ti $K$-shell x-ray emission was spectrally resolved with a two-channel crystal spectrometer and also with a set of filtered aluminum x-ray diodes; both instruments provide absolute measurement of the multi-keV x-ray emission. We find between 40 and 260 J of output with $4.67\ensuremath{\le}h\ensuremath{\nu}\ensuremath{\le}5.0\text{ }\text{ }\mathrm{keV}$.