Reflectivity and spectral shift from laser plasmas generated by high-contrast, high-intensity KrF laser pulses

Abstract

The energy and spectrum of the reflected 248 nm radiation are studied from solid targets up to 1.15 × 10 18 W cm −2 intensity. The experiments used the 700 fs directly amplified pulses of the KrF system which was cleaned from prepulses with the new Fourier-filtering method providing 12 orders of magnitude temporal contrast. Increasing the intensity from 10 15 W cm −2 results in increasing absorption up to more than 90% above 10 18 W cm −2 . This is accompanied by increasing x-ray conversion exhibiting a less steep power law dependence for low-Z matter than for gold. Strong blue shift of the reflected radiation from the backward propagating plasma was observed. It is shown that in the case of KrF laser pulses of highest contrast, vacuum heating can be one of the dominant absorption mechanisms. This article is part of a discussion meeting issue ‘Prospects for high gain inertial fusion energy (part 1)’.

Preparations for a European R&D roadmap for an inertial fusion demo reactor

“…The European consortium has also undertaken studies of stable channel formation in fusion relevant plasmas [ 36 – 38 ], electromagnetic pulse generation and mitigation [ 39 ], UV fast electron generation and energy transport [ 40 ], magnetic fields [ 41 ], reactor materials under hostile radiation environments [ 23 ], among others, including the role of magnetic fields in guiding fast electrons.…”

Large Spectral Shift of Reflected Radiation From Laser Plasmas Generated by High Contrast KrF Laser Pulses

“…Detailed study of the reflectivity for high and low contrast pulses for p-polarized radiation has been discussed in detail elsewhere, together with the observed increasing x-ray conversion efficiency with increasing intensity [18]. Herewith Figure 3 shows the measured specular reflectivity from boron and gold targets both for p-and s-polarized 248 nm KrF laser pulses of 700 fs duration.…”

Prospects for high gain inertial fusion energy: an introduction to the second edition

“…The requirement for high gain in order to drive down the capital infrastructure costs of future inertial fusion power plants (and, therefore, the costs of electricity) when these reactors are ready for market delivery were also reinforced [5]. Following discussions of the welcome formation of a fusion industry advocacy group [6] as well as discussions on the elements required for constructing future roadmaps [7], a number of research articles devoted to understanding obstacles to ignition on current-day devices were then presented [8][9][10][11][12][13]. Part I concluded with a fascinating discussion of the benefits of deploying the Naval Research Laboratory's argon-fluoride (ArF) driver, operating at a wavelength of 193 nm, for direct drive of inertial fusion targets.…”