H{sup -} radio frequency source development at the Spallation Neutron Source

Journal Article · Wed Feb 15 00:00:00 EST 2012 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.3678651· OSTI ID:22063884

Welton, R F; Gawne, K R; Han, B X; Murray, S N; Pennisi, T R; Roseberry, R T; Santana, M; Stockli, M P ^[1]; Dudnikov, V G ^[2]; Turvey, M W ^[3]

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1. Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37830-6471 (United States)
2. Muons, Inc., 552 N. Batavia Avenue, Batavia, Illinois 60510 (United States)
3. Villanova University, 800E. Lancaster Ave, Villanova, Pennsylvania 19085 (United States)

The Spallation Neutron Source (SNS) now routinely operates nearly 1 MW of beam power on target with a highly persistent {approx}38 mA peak current in the linac and an availability of {approx}90%. H{sup -} beam pulses ({approx}1 ms, 60 Hz) are produced by a Cs-enhanced, multicusp ion source closely coupled with an electrostatic low energy beam transport (LEBT), which focuses the 65 kV beam into a radio frequency quadrupole accelerator. The source plasma is generated by RF excitation (2 MHz, {approx}60 kW) of a copper antenna that has been encased with a thickness of {approx}0.7 mm of porcelain enamel and immersed into the plasma chamber. The ion source and LEBT normally have a combined availability of {approx}99%. Recent increases in duty-factor and RF power have made antenna failures a leading cause of downtime. This report first identifies the physical mechanism of antenna failure from a statistical inspection of {approx}75 antennas which ran at the SNS, scanning electron microscopy studies of antenna surface, and cross sectional cuts and analysis of calorimetric heating measurements. Failure mitigation efforts are then described which include modifying the antenna geometry and our acceptance/installation criteria. Progress and status of the development of the SNS external antenna source, a long-term solution to the internal antenna problem, are then discussed. Currently, this source is capable of delivering comparable beam currents to the baseline source to the SNS and, an earlier version, has briefly demonstrated unanalyzed currents up to {approx}100 mA (1 ms, 60 Hz) on the test stand. In particular, this paper discusses plasma ignition (dc and RF plasma guns), antenna reliability, magnet overheating, and insufficient beam persistence.

• OSTI ID: 22063884
• Journal Information: Review of Scientific Instruments, Vol. 83, Issue 2; Conference: ICIS 2011: 14. international conference on ion sources, Giardini-Naxos, Sicily (Italy), 12-16 Sep 2011; Other Information: (c) 2012 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0034-6748
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ANTENNAS
BEAM CURRENTS
BEAM PULSERS
BEAM TRANSPORT
CALORIMETRY
COPPER
ENAMELS
HYDROGEN IONS 1 MINUS
ION SOURCES
LINEAR ACCELERATORS
MAGNETS
MHZ RANGE
NEUTRON SOURCES
PLASMA
PLASMA GUNS
PORCELAIN
RADIOWAVE RADIATION
RF SYSTEMS
SPALLATION