A solenoid final focusing system with plasma neutralization for target heating experiments

Intense bunches of low-energy heavy ions have been suggested as means to heat targets to the warm dense matter regime (Temperature ~ 0.1 to 10 eV, solid density ~1% to 100%). In order to achieve the required intensity on target, a beam spot radius of approximately 0.5 mm, and pulse duration of 2 ns is required with an energy deposition of approximately 1 J/cm². This translates to a peak beam current of 8 A for 0.4 MeV K+ ions. To increase the beam intensity on target, a plasma-filled high-field solenoid is being studied as a means to reduce the beam spot size from several mm to the sub-mm range. A prototype experiment to demonstrate the required beam dynamics has been built at Lawrence Berkeley National Laboratory. The operating magnetic field of the pulsed solenoid is 8 T. Challenges include suitable injection of the plasma into the solenoid so that the plasma density near the focus is sufficiently high to maintain space- charge neutralization of the ion beam pulse. Initial experimental results are presented.