Experimental evidence for the enhanced and reduced stopping regimes for protons propagating through hot plasmas

Abstract

Our understanding of the dynamics of ion collisional energy loss in a plasma is still not complete, in part due to the difficulty and lack of high-quality experimental measurements. These measurements are crucial to benchmark existing models. Here, we show that such a measurement is possible using high-flux proton beams accelerated by high intensity short pulse lasers, where there is a high number of particles in a picosecond pulse, which is ideal for measurements in quickly expanding plasmas. By reducing the energy bandwidth of the protons using a passive selector, we have made proton stopping measurements in partially ionized Argon and fully ionized Hydrogen plasmas with electron temperatures of hundreds of eV and densities in the range 1020–1021 cm−3. In the first case, we have observed, consistently with previous reports, enhanced stopping of protons when compared to stopping power in non-ionized gas. In the second case, we have observed for the first time the regime of reduced stopping, which is theoretically predicted in such hot and fully ionized plasma. The versatility of these tunable short-pulse laser based ion sources, where the ion type and energy can be changed at will, could open up the possibility for a variety of ion stopping power measurements in plasmas so long as they are well characterized in terms of temperature and density. In turn, these measurements will allow tests of the validity of existing theoretical models.

Generation of α-Particle Beams With a Multi-kJ, Peta-Watt Class Laser System

“…It is known that the penetration range of ions in a dense plasma is still not well-established because of the uncertainty in theoretically assessing the Coulomb logarithm which determines the stopping power. In fact, in the last years several experiments have addressed the study of stopping power of protons in plasma and in warm dense matter [9][10][11]. For αparticles the situation is similar and the effect on the possibility of igniting a thermonuclear target in ICF can be important [12][13][14].…”

Observation of a high degree of stopping for laser-accelerated intense proton beams in dense ionized matter

“…By irradiating a thin foil with ultra-high-intensity lasers, an ultrahigh accelerating field (1 TV/m) can be formed and multi-MeV ions with high intensity (10 10 A/cm 2 ) in short timescale (~ps) are produced [45][46][47][48][49][50][51][52][53] . Such beams provide experimental opportunities to investigate the beam-driven complex collective phenomena [54][55][56][57][58][59] . In particular, the stopping power for these intense beam could be orders of magnitude higher than that for individual particles if the beam intensity is high enough [60][61][62][63] .…”

High-energy-density physics based on HIAF

“…, Standard Stopping Model [74] , Li-Petrosso理论 [75] , T-Matrix理论 [76] 以及PIC数值 模拟程序 [77,78] Figure 15 The quasi-molecular resonace transfer probability of inner shell electrons as functions of (a) charge state and (b) energy of ions [68]. [22,84] .…”