Extreme compression of heavy-ion beam pulses: Experiments and modeling

Longitudinal bunch compression of intense ion beams for warm dense matter and heavy ion fusion applications occurs by imposing an axial velocity tilt onto an ion beam across the acceleration gap of a linear induction accelerator, and subsequently allowing the beam to drift through neutralizing plasma as the pulse compresses. The finite-size of the acceleration gap and time-dependent nature of the induction voltage waveform for longitudinal compression are demonstrated to increase the effective longitudinal temperature of the charge bunch, reduce the resulting fractional velocity tilt from its intended value, and transversely defocus the beam in a time-dependent manner. The over-focusing technique or a strong final-focus solenoid may be used to refocus the longitudinally compressing beam to the small spot size required (sub-mm to few mm) at a coincident focal plane. In the case of a final-focus solenoid, supersonic cathodic-arc plasma may be injected into the high-field region from the low-field end for beam neutralization experiments.