It is found that stable proton acceleration from a thin foil irradiated by a linearly polarized ultraintense laser can be realized for appropriate foil thickness and laser intensity. A dual-peaked electrostatic field, originating from the oscillating and nonoscillating components of the laser ponderomotive force, is formed around the foil surfaces. This field combines radiation-pressure acceleration and target normal sheath acceleration to produce a single quasimonoenergetic ion bunch. A criterion for this mechanism to be operative is obtained and verified by two-dimensional particle-in-cell simulation. At a laser intensity of ∼5.5×10(22) W/cm(2), quasimonoenergetic GeV proton bunches are obtained with ∼100 MeV energy spread, less than 4° spatial divergence, and ∼50% energy conversion efficiency from the laser.
Comparison of the dose-response relationship of retinal damage induced by Q-switched (Q-sw) Nd:YAG lasers was conducted for rabbits and monkeys. Experimental results indicated that the two probit regression lines were parallel to each other, and the damage threshold (ED50) ratio was approximately 1:3.57. Observations of the injurious effects of Q-sw Nd:YAG rangefinders--the total energy level being about 10-100 mJ--and their injurious distances are reported in this paper. A brief description is given of coagulative and hemorrhagic pathological changes under different exposure conditions and at various distances.
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