Isochoric Heating of Solid-Density Matter with an Ultrafast Proton Beam

Abstract

A new technique is described for the isochoric heating (i.e., heating at constant volume) of matter to high energy-density plasma states (>10(5) J/g) on a picosecond time scale (10(-12)sec). An intense, collimated, ultrashort-pulse beam of protons--generated by a high-intensity laser pulse--is used to isochorically heat a solid density material to a temperature of several eV. The duration of heating is shorter than the time scale for significant hydrodynamic expansion to occur; hence the material is heated to a solid density warm dense plasma state. Using spherically shaped laser targets, a focused proton beam is produced and used to heat a smaller volume to over 20 eV. The technique described of ultrafast proton heating provides a unique method for creating isochorically heated high-energy density plasma states.

Investigations of Field Dynamics in Laser Plasmas with Proton Imaging

“…The temporal characteristics of the proton emission have been discussed theoretically and are supported by experimentally gained arguments in several publications [1,3,93,101,102]. The acceleration of the protons takes place on a picosecond timescale.…”

“…The proton beam usually has a broad and continuous energy distribution -but the energetic protons are all accelerated within 1-2 ps [1,3,93,101,102]. Starting at nearly the same time from the target, they reach the interaction target at different times.…”

“…That means that the instantaneous frequency is changing in time. If the frequency increases/decreases the pulse is called up-/down-chirped 1 . A pulse with dω(t)/dt = d 2 ϕ(t)/dt 2 = a 2 = const is called linearly chirped, the frequency is changing linearly in time.…”

“…Different applications established recently benefit from these beam attributes. High-energy-density matter can be created, which is of interest for astrophysics [1,2]. Furthermore, these beams are predestined for temporally and 1 spatially resolved pump-probe experiments.…”

“…By using curved targets the emission angle of the ion beam can be influenced. Concave targets can focus or collimate the whole ion beam [1,[10][11][12]. To achieve tailored spectra, especially monoenergetic ion beams, different approaches exist.…”