Multi-keV x-ray production by high harmonic generation using ultra-intense lasers

Board Of Regents, Nshe, Obo University Of Nevada, Reno, Reno NV

Investigators

Abstract

This project addresses the development of two techniques to extend the reach of compact x-ray sources, producing bright, ultrafast x-rays in the multi-kilovolt regime from sources based on intense laser-plasma interaction. The research involves the experimental generation, measurement and modeling of ultrafast (femtosecond) x-rays using the mechanisms of betatron radiation and high harmonic generation (HHG) in the relativistic limit. The first mechanism uses the betatron oscillation of accelerated electrons in the focusing field of a plasma-based accelerator to generate intense broad-bandwidth incoherent x-rays spanning the kilovolt hundred kilovolt window. In the first phase of the work this betatron radiation source will be used to test, calibrate, and field x-ray diagnostics required to characterize the radiation in this range. This knowledge and expertise will be applied to HHG in the second phase of this program. Secondly, a new method for extending coherent x-ray HHG into the many-kilovolt regime by using multiple laser pulses of relativistic intensity will be developed. HHG occurs when an electron is ionized from a host atom and is then driven back to recombine with the atom by the laser field. Photon energy is limited in conventional single-pulse schemes by plasma-induced decoherence, which limits the effective interaction length. For relativistic intensities, the magnetic interaction of the ionized electron with the laser field further suppresses radiation generation by preventing the electron from recombining with the atom. An intense laser will be used to expel plasma electrons creating an ion channel, and, by using two counterpropagating pulses, the magnetic-field induced drift of the electron will be removed. This will extend the reach of compact coherent HHG sources from 0.5 kilovolt (current state-of-the-art) to potentially 100 kilovolt and beyond.