Electron Gun and Collector Simulations for Rhic Ebis at Bnl

Based on the successful experience of the Brookhaven National Laboratory test electron beam ion sources (EBIS), the relativistic heavy ion collider (RHIC) EBIS design utilizes a 10 A electron beam to produce the required ion source output intensity of 3.4×109 of Au32+ ions per 10–40 μs pulse. In order to provide increased cathode lifetime and reliability at the required 10 A, and accommodate future upgrades of RHIC EBIS ion intensity, it is desirable to upgrade the electron gun. Simulations have been made for a new electron gun and electron collector capable of generating and dissipating an electron beam with current up to 20 A. The method of forming the electron beam using magnetic compression and inverse magnetron geometry of the electron gun are the same as has been tested successfully on the electron beam test stand. The new gun has higher perveance and partially shielded spherical cathode. A bell-shaped radial current density distribution with reduced current density on a periphery of the beam, combined with a modified shape of the electron collector magnet shim, yields a simulated power density on the surface of the electron collector below 400 W/cm2 for electron beam currents up to 20 A.