Modeling of tungsten filament in gas discharge in H ion source.

Sources of negative ions such as H are essential elements of proton accelerators and tokamaks. They have limited lifetime. The replacement of an ion source is a costly process causing delays in the operation of the entire machine.

Upgrading the LANSCE accelerator with a SNS RF-driven H ion source.

The LANSCE accelerator is currently powered by a filament-driven, biased converter-type H ion source that operates at 10%, the highest plasma duty factor for this type of source, using only ∼2.2 SCCM of H. The ion source needs to be replaced every 4 weeks, which takes up to 4 days.

Design and fabrication of a duoplasmatron extraction geometry and LEBT for the LANSCE H⁺ RFQ project.

The 750-keV H(+) Cockcroft-Walton at LANSCE will be replaced with a recently fabricated 4-rod Radio Frequency Quadrupole (RFQ) with injection energy of 35 keV. The existing duoplasmatron source extraction optics need to be modified to produce up to 35 mA of H(+) current with an emittance <0.02 π-cm-mrad (rms, norm) for injection into the RFQ.

Different approaches to modeling the LANSCE H⁻ ion source filament performance.

An overview of different approaches to modeling of hot tungsten filament performance in the Los Alamos Neutron Science Center (LANSCE) H(-) surface converter ion source is presented. The most critical components in this negative ion source are two specially shaped wire filaments heated up to the working temperature range of 2600 K-2700 K during normal beam production. In order to prevent catastrophic filament failures (creation of hot spots, wire breaking, excessive filament deflection towards source body, etc.

Electron stripping processes of H⁻ ion beam in the 80 kV high voltage extraction column and low energy beam transport line at LANSCE.

Basic vacuum calculations were performed for various operating conditions of the Los Alamos National Neutron Science H(-) Cockcroft-Walton (CW) injector and the Ion Source Test Stand (ISTS). The vacuum pressure was estimated for both the CW and ISTS at five different points: (1) inside the H(-) ion source, (2) in front of the Pierce electrode, (3) at the extraction electrode, (4) at the column electrode, and (5) at the ground electrode. A static vacuum analysis of residual gases and the working hydrogen gas was completed for the normal ion source working regime.