We present our recent experimental results of monoenergetic protons accelerated from the interaction of an intense terawatt CO2 laser pulse with a near-critical hydrogen gas target, with its density profile tailored by a hydrodynamic shock. A 5-ns Nd:YAG laser pulse is focused onto a piece of stainless steel foil mounted at the front edge of the gas jet nozzle orifice. The ablation launches a spherical shock into the near-critical gas column, which creates a sharp density gradient at the front edge of the target, with ~ 6X local density enhancement up to several times of critical density within ~<100 microns. With such density profile, we have obtained monoenergetic proton beams with good shot-to-shot reproducibility and energies up to 1.2 MeV.
Over the last two decades, BNL’s ATF has pioneered the use of high-peak power CO2 lasers for research in advanced accelerators and radiation sources. Our recent developments in ion acceleration, Compton scattering, and IFELs have further underscored the benefits from expanding the landscape of strong-field laser interactions deeper into the midinfrared (MIR) range of wavelengths. This extension validates our ongoing efforts in advancing CO2 laser technology, which we report here. Our next-generation, multi-terawatt, femtosecond CO2 laser will open new opportunities for studying ultra-relativistic laser interactions with plasma in the MIR spectral domain. We will address new regimes in the particle acceleration of ions and electrons, as well as the radiations sources, ranging from THz to gamma- rays, that are enabled by the emerging ultra-fast CO2 lasers.
We describe the physical principles and architecture of a multi-stage picosecond terawatt CO2 laser system, PITER-I,
operational at Brookhaven National Laboratory (BNL). The laser is a part of the DOE user's facility open for
international scientific community. One of the prospective strong-field physics applications of PITER-I is the
production of proton- and heavy-ion beams upon irradiating thin-film targets and gas jets. We discuss the possibilities
for upgrading a CO2 laser to a multi-terawatt femtosecond regime.
Igor Pogorelsky, Ilan Ben-Zvi, Marcus Babzien, Karl Kusche, John Skaritka, Igor Meshkovsky, Andrey Dublov, Vasili Lekomtsev, Igor Pavlishin, Yuri Boloshin, Gennady Deineko, Akira Tsunemi
The first terawatt picosecond CO2 laser, PITER I, is under commissioning at the Brookhaven Accelerator Test Facility. PITER I consists of a single-mode TEA oscillator, semiconductor optical switch, and two stages of the multi- atmosphere amplifiers. We report on design, simulation, and tests of the 10 ATM final amplifier that allows multi- terawatt peak power extraction in a picosecond laser pulse.
Dennis Palmer, Xi Wang, Roger Miller, Marcus Babzien, Ilan Ben-Zvi, Claudio Pellegrini, Joe Sheehan, John Skaritka, Triveni Srinivasan-Rao, Herman Winick, Martin Woodle, V. Yakimenko
The BNL/SLAC/UCLA symmetrized 1.6 cell S-band emittance- compensated photoinjector has been installed at the Brookhaven Accelerator Test Facility (ATF). The commissioning results and performance of the photocathode injector are presented. This photoinjector consists of the symmetrized BNL/SLAC/UCLA 1.6 cell S-band photocathode radio frequency gun and a single solenoidal magnet for transverse emittance compensation. The highest acceleration field achieved on the cathode is 150 MV/m, and the normal operating field is 125 MV/m. The quantum efficiency of the copper cathode was measured to be 4.5 multiplied by 10-5. The measured quantum efficiency of the magnesium cathode is a factor of ten greater than that of copper after using both laser and laser assisted explosive electron emission cleaning. The transverse emittance and bunch length of the photoelectron beam were measured. The optimized rms normalized emittance for a charge of 329 plus or minus 12 pC is 2.0 plus or minus 0.3 pi mm-mrad. The bunch length dependency of photoelectron beam on the rf gun phase and acceleration fields were experimentally investigated. Electric and magnetic field asymmetries studies are presented.
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