PIC Simulation (IMAGE) Osaka University Caption This is a three-dimensional (x, y, z) PIC simulation result using EPOCH code for a proton plasma. Laser-matter interaction is not taken into account here for simplicity. Each side of a periodic cube box and the cell size are set to be 240 nm and 2 nm, respectively. At t = 0, the interior of the bubble with R0 = 60 nm is perfect vacuum. An otherwise uniform plasma composed of cold ions and hot electrons characterised by Te = 1 MeV, Z = 1, and ni0 = ne0 = 3×1021 cm−3 are initiated. (a) Snapshots of the bubble collapse with the proton density distributions color-coded. The bubble is found to pulsate repeating implosion and explosion. (b)Temporal evolution of the proton energy spectrum for the same case as panel (a). At each collapse, proton flash is observed. Credit M. Murakami Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.