Energetics and energy scaling of quasi-monoenergetic protons in laser radiation pressure acceleration

Abstract

Theoretical and computational studies of the ion energy scaling of the radiation pressure acceleration of an ultra-thin foil by short pulse intense laser irradiation are presented. To obtain a quasi-monoenergetic ion beam with an energy spread of less than 20%, two-dimensional particle-in-cell simulations show that the maximum energy of the quasi-monoenergetic ion beam is limited by self-induced transparency at the density minima caused by the Rayleigh-Taylor instability. For foils of optimal thickness, the time over which Rayleigh-Taylor instability fully develops and transparency occurs is almost independent of the laser amplitude. With a laser power of about one petawatt, quasi-monogenetic protons with 200 MeV and carbon ions with 100 MeV per nucleon can be obtained, suitable for particle therapy applications

Enhancement of proton energy by polarization switch in laser acceleration of multi-ion foils

“…17 This is a more efficient acceleration process for producing high energy monoenergetic protons, suitable for many applications requiring that the accelerated protons have good beam quality and a narrow energy spectrum. However, previous works demonstrated with two-dimensional (2D) particle-in-cell (PIC) simulations 16,18,[22][23][24] that the Rayleigh-Taylor instability (RTI) limits the acceleration achieved by RPA and rapidly broadens the proton beam's energy spectrum. For RPA of thin-foil targets of one species, the energy scaling study with PIC simulation 18 indicates that petawatt power laser is needed to obtain $200 MeV quasi-monoenergetic protons with energy spread within 20% of the peak flux energy, which may make the laser proton acceleration scheme less attractive for commercial practical applications, as it is difficult to build a petawatt laser, and the laser also produces strong radiation that is difficult to shield.…”

“…However, previous works demonstrated with two-dimensional (2D) particle-in-cell (PIC) simulations 16,18,[22][23][24] that the Rayleigh-Taylor instability (RTI) limits the acceleration achieved by RPA and rapidly broadens the proton beam's energy spectrum. For RPA of thin-foil targets of one species, the energy scaling study with PIC simulation 18 indicates that petawatt power laser is needed to obtain $200 MeV quasi-monoenergetic protons with energy spread within 20% of the peak flux energy, which may make the laser proton acceleration scheme less attractive for commercial practical applications, as it is difficult to build a petawatt laser, and the laser also produces strong radiation that is difficult to shield. 25,26 However, by using a thin composite multi-ion protoncarbon foil, researches have shown that the energy can be further increased.…”

“…The scheme of laser RPA of quasi-monoenergetic protons has been actively studied in theory and simulations [11][12][13][14][15][16][17][18][19] and experiments. 20,21 In RPA, or equivalently "light sail," high intensity circularly polarized laser light with a high contrast ratio accelerates nearly the whole thin foil by the radiation pressure.…”

Spot size dependence of laser accelerated protons in thin multi-ion foils

“…In order to acquire quasi-monoenergetic protons, the scheme of laser RPA has been actively studied in theory and simulations [18][19][20][21][22][23][24][25][26] and experiments. 27,28 In RPA, a high intensity circularly polarized laser beam irradiates an ultra-thin foil and accelerates nearly the whole foil by the radiation pressure.…”

Quasi-monoenergetic protons accelerated by laser radiation pressure and shocks in thin gaseous targets

“…Protons with quasi-monoenergy and high beam quality were obtained in simulations. [13][14][15][16][17][18][19][20][21] However, solid hydrogen targets are difficult to produce in experiment and only diamond-like carbon has been used experimentally with limited success. 15 Recently, CO 2 laser proton acceleration with gas targets has attracted much interest since hydrogen gas is readily available, and CO 2 laser is low-cost, long-duration and able to deliver substantial amounts of energy.…”