Analysis of laser wavelength and energy dependences of the impulse in a magnetic thrust chamber system for a laser fusion rocket

Experiments using a pendulum thrust stand are performed to determine the dependences of the impulse on the laser wavelength and energy in a magnetic thrust chamber system for a laser fusion rocket. The impulse is generated by the interaction between a diamagnetic current in a laser-produced plasma and a magnetic field. The plasma is produced by irradiating a spherical polyacetal target with a single-beam glass laser (laser pulse duration: 1.3 ns; laser wavelengths: 1,053, 527 and 351 nm; laser energy: 30-900 J). The magnetic field is generated by a cylindrical neodymium permanent magnet (50mm diameter and 40mm long) placed in a position 33mm from the target. Impulses in the range 0.02- 10 mNs are measured using a pendulum thrust stand. The experiments reveal that the impulse for 2ω is similar to that for 3ω, and is larger than that for ω.