Electrostatic shock acceleration of ions in near-critical-density plasma driven by a femtosecond petawatt laser
Prashant Kumar Singh, Vishwa Bandhu Pathak, Jung Hun Shin, Il Woo Choi, Kazuhisa Nakajima, Seong Ku Lee, Jae Hee Sung, Hwang Woon Lee, Yong Joo Rhee, Constantin Aniculaesei, Chul Min Kim, Ki Hong Pae, Myung Hoon Cho, Calin Ioan Hojbota, Seong Geun Lee, Florian Mollica, V. Malka, Chang‐Mo Ryu, Hyung Taek Kim, Chang Hee Nam
Abstract
With the recent advances in ultrahigh intensity lasers, exotic astrophysical phenomena can be investigated in laboratory environments. Collisionless shock in a plasma, prevalent in astrophysical events, is produced when a strong electric or electromagnetic force induces a shock structure in a time scale shorter than the collision time of charged particles. A near-critical-density (NCD) plasma, generated with an intense femtosecond laser, can be utilized to excite a collisionless shock due to its efficient and rapid energy absorption. We present electrostatic shock acceleration (ESA) in experiments performed with a high-density helium gas jet, containing a small fraction of hydrogen, irradiated with a 30 fs, petawatt laser. The onset of ESA exhibited a strong dependence on plasma density, consistent with the result of particle-in-cell simulations on relativistic plasma dynamics. The mass-dependent ESA in the NCD plasma, confirmed by the preferential reflection of only protons with two times the shock velocity, opens a new possibility of selective acceleration of ions by electrostatic shock.