Electron energy increase in a laser wakefield accelerator using up-ramp plasma density profiles

• Published in: Scientific reports Vol. 9; no. 1; pp. 11249 - 7
• Main Authors: Aniculaesei, Constantin, Pathak, Vishwa Bandhu, Kim, Hyung Taek, Oh, Kyung Hwan, Yoo, Byung Ju, Brunetti, Enrico, Jang, Yong Ha, Hojbota, Calin Ioan, Shin, Jung Hun, Jeon, Jong Ho, Cho, Seongha, Cho, Myung Hoon, Sung, Jae Hee, Lee, Seong Ku, Hegelich, Björn Manuel, Nam, Chang Hee
• Format: Journal Article
• Language: English
• Published: England Nature Publishing Group 02.08.2019; Nature Publishing Group UK
• Subjects: Divergence; Energy; Helium; Lasers; Plasma
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-019-47677-5

The phase velocity of the wakefield of a laser wakefield accelerator can, theoretically, be manipulated by shaping the longitudinal plasma density profile, thus controlling the parameters of the generated electron beam. We present an experimental method where using a series of shaped longitudinal plasma density profiles we increased the mean electron peak energy more than 50%, from 175 ± 1 MeV to 262 ± 10 MeV and the maximum peak energy from 182 MeV to 363 MeV. The divergence follows closely the change of mean energy and decreases from 58.9 ± 0.45 mrad to 12.6 ± 1.2 mrad along the horizontal axis and from 35 ± 0.3 mrad to 8.3 ± 0.69 mrad along the vertical axis. Particle-in-cell simulations show that a ramp in a plasma density profile can affect the evolution of the wakefield, thus qualitatively confirming the experimental results. The presented method can increase the electron energy for a fixed laser power and at the same time offer an energy tunable source of electrons.