Generation of MeV proton with 30 mJ laser energy by optimizing focusing spot using deformable mirror

Takuya Nayuki; Takashi Fujii; Yuji Oishi; Kei Takano; Xiaofang Wang; Alexander A. Andreev; Koshichi Nemoto; Ken-ichi Ueda

doi:10.1117/12.669278

8 June 2006 Generation of MeV proton with 30 mJ laser energy by optimizing focusing spot using deformable mirror

Takuya Nayuki, Takashi Fujii, Yuji Oishi, Kei Takano, Xiaofang Wang, Alexander A. Andreev, Koshichi Nemoto, Ken-ichi Ueda

Author Affiliations +

Proceedings Volume 6018, 5th International Workshop on Adaptive Optics for Industry and Medicine; 60180F (2006) https://doi.org/10.1117/12.669278
Event: 5th International Workshop on Adaptive Optics for Industry and Medicine, 2005, Beijing, China

Abstract

The generation of energetic protons using a polyimide tape of 7.5 μm thickness was carried out with laser pulses of 30 mJ energy and 80 fs duration. A deformable mirror system with a genetic algorithm (GA) was developed to optimize the laser-focusing spot. The fitness values used in the GA were measured from the focusing intensities under the low-gain condition of the power amplifier, or from x-ray in situ signals emitted from the target. Although we obtained a diffraction-limited size of 2 μm (full width at half maximum) using the former value, a precise optimization using the latter value was essential to accelerate protons whose flux was 10⁶/MeV/shot to a maximum energy of 1.1±0.3 MeV with laser pulses of only 30 mJ energy since a laser spot that is too tight may be sensitive to wave-front distortion caused by residual thermal lenses of the power amplifier.

Citation Download Citation

Takuya Nayuki, Takashi Fujii, Yuji Oishi, Kei Takano, Xiaofang Wang, Alexander A. Andreev, Koshichi Nemoto, and Ken-ichi Ueda "Generation of MeV proton with 30 mJ laser energy by optimizing focusing spot using deformable mirror", Proc. SPIE 6018, 5th International Workshop on Adaptive Optics for Industry and Medicine, 60180F (8 June 2006); https://doi.org/10.1117/12.669278

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