Intense tera-hertz laser driven proton acceleration in plasmas

Abstract

We investigate the acceleration of a proton beam driven by intense tera-hertz (THz) laser field from a near critical density hydrogen plasma. Two-dimension-in-space and three-dimension-in-velocity particle-in-cell simulation results show that a relatively long wavelength and an intense THz laser can be employed for proton acceleration to high energies from near critical density plasmas. We adopt here the electromagnetic field in a long wavelength (0.33 THz) regime in contrast to the optical and/or near infrared wavelength regime, which offers distinct advantages due to their long wavelength (λ=350 μm), such as the λ2 scaling of the electron ponderomotive energy. Simulation study delineates the evolution of THz laser field in a near critical plasma reflecting the enhancement in the electric field of laser, which can be of high relevance for staged or post ion acceleration.

Laser‐Driven Strong‐Field Terahertz Sources

“…Reproduced with permission. [16] b) Scheme of the evanescent-wave postaccelerator for laser-generated proton beams.…”

“…Another recent proposal is a THz-driven ion source from a near-critical-density hydrogen plasma. [16]…”

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reason for this interest relies on the fact that THz radiation can couple resonantly to numerous fundamental motions of ions, electrons, and electron spins in all phases of matter. [6,8,11] For example, simulations suggest that exciting matter with intense THz transients may lead to massive modifications of electrically [14] or magnetically [15] ordered domains and enable the acceleration of free ions to ≈1 MeV, [16] and postacceleration to 50-100 MeV energies. Consequently, THz radiation, both continuous-wave and pulsed, has been used for characterization of and gaining insight into elementary processes in complex materials.

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“…[3][4][5][6][7][8][9][10][11][12][13] Instead of using weak fields to primarily observe selected THz modes such as phonons or magnons, strong fields allow one to actively drive them to unprecedentedly large amplitudes, potentially thereby resulting in novel states of matter. [6,8,11] For example, simulations suggest that exciting matter with intense THz transients may lead to massive modifications of electrically [14] or magnetically [15] ordered domains and enable the acceleration of free ions to ≈1 MeV, [16] and postacceleration to 50-100 MeV energies. [17] Remarkable experimental results such as switching of magnetic order, [18,19] parametric amplification of optical phonons, [20] novel insights into spin-lattice coupling, [21,22] and acceleration of free electrons in a THz linear accelerator [23] were achieved only recently.…”

110-mJ 225-fs cryogenically cooled Yb:CaF_2 multipass amplifier

“…Besides enabling cutting-edge applications, like investigation and control over material properties and their dynamics under the influence of extremely high quasi-static fields [12], or THz-assisted attosecond pulse generation [13], such intense THz pulses are ideally suited for charged-particle manipulation [14] and acceleration [15][16][17]. Combining efficient diodepumped solid-state (DPSS) sub-ps pump lasers with novel THz generation techniques and laser-ion acceleration may lead to the realization of compact and versatile ion sources suitable for medical applications [15,17]. Therefore, the development of short-pulse, high-energy pump lasers is highly demanded for novel techniques of THz pulse generation and application.…”