Simulation of the ion source extraction and low energy beam transport systems for the Spallation Neutron Source

Abstract

The ion source for the Spallation Neutron Source is a radio-frequency (rf) multi-cusp, volume-type H− source that is coupled to a rf quadrupole accelerator through a low energy beam transport (LEBT) system consisting of five electrostatic elements. To gain a deeper understanding of the operation of this system and to continue to refine the design, we have performed ion extraction and transport simulations using the computer code PBGUNS. A comparison is presented between simulation and the measured phase space of the beam for various values of LEBT electrode potentials. Both the emittance magnitude and orientation in phase space were found to be in reasonable agreement with measurement. A design study is also presented where the angle of the source outlet electrode has been optimized with the aid of PBGUNS simulations, resulting in a substantial reduction of the emittance.

Design, Operational Experiences and Beam Results Obtained with the SNS H− Ion Source and LEBT at Berkeley Lab

“…A systematic study of outlet-aperture contours 15 indicated that a longer channel such as the one shown in Fig. 3, as opposed to the knife-edge shape seen in Fig.…”

Status of the SNS H− Ion Source and Low-Energy Beam Transport System

“…A systematic study of outlet-aperture contours 16 indicated that a longer channel such as the one shown in Fig. 3, as opposed to the knife-edge shape seen in Fig.…”

Progress on a gas-accepting ion source for continuous-flow accelerator mass spectrometry

“…A drawing of the new ion source is shown in Figure 6. Details of the extraction geometry and magnetic fields were optimized through the respective use of the software PBGUNS [11] and Infolytica [12] MagNet. In comparison to the current ion source, the new version has several improvements including: i) better coupling to the magnesium-vapor charge-exchange canal, ii) improved control of the magnetic field (by using a solenoid magnet rather than permanent magnets), iii) improved alignment capability, iv) the ability to operate at potentials higher than 30 kV, v) the elimination of internal water seals with O-rings, and vi) the use of commercially available brazed insulators (as opposed to a glued ceramic/metal extraction column).…”