A 1.8-MeV K⁺ injector for the high current beam transport experiment

Abstract

For the High Current Beam Transport Experiment~HCX! at Lawrence Berkeley National Laboratory, an injector is required to deliver up to 1.8 MV of 0.6 A K ϩ beam with an emittance of '1 p-mm-mrad. We have successfully operated a 10-cm-diameter surface ionization source together with an electrostatic quadrupole~ESQ! accelerator to meet these requirements. The pulse length is '4 ms, firing at once every 10-15 s. By optimizing the extraction diode and the ESQ voltages, we have obtained an output beam with good current density uniformity, except for a small increase near the beam edge. Characterization of the beam emerging from the injector included measurements of the intensity profile, beam imaging, and transverse phase space. These data along with comparison to computer simulations provide the knowledge base for designing and understanding future HCX experiments.

The DCU laser ion source

“…24 The beam is created in an idealized one-dimensional ͑1D͒ diode and accelerated to the required kinetic energy. The space-charge-limited current density for ions with charge-state Z i and mass m i in a gap of width d and applied voltage V ext is given by the expression…”

Parametic Study of the current limit within a single driver-scaletransport beam line of an induction Linac for Heavy Ion Fusion

“…The source is biased at a negative DC potential ( Bias V ) and the gate electrode is at dome potential, thereby inhibiting ion emission from the hot surface. During ion extraction, the extraction circuit, which acts like a switch, delivers a pulse swing 3 ( Gate V ) up to 140 kV, going from a bias voltage of -60 kV to an extraction voltage of +80 kV, applied to the source with respect to the gate electrode through a step-up transformer driven by a tunable pulse forming network (PFN) [124,125]. The source filament transformer not only supplies the heater power (2500 Watts), but is also a high-voltage isolation transformer allowing the source to be biased at -80 kV.…”

Progress in the high current experiment (HCX) February-July 2002

“…The beam energy at present is limited to 1.5 MeV until the water resistor that distributes the voltage along the injector column is modified. To date, contact-ionization and aluminosilicate ion sources have been used, as described in [2]. The injector beam characterization measurements and the very first measurements through the HCX were made using the contact ionization source, before switching to the alumino-silicate source (f100 mm diameter) in April 2002.…”