Neutral Beam Injection for Plasma and Magnetic FieldDiagnostics

Conference · Wed Aug 01 00:00:00 EDT 2007

OSTI ID:925529

Vainionpaa, Jaakko Hannes; Leung, Ka Ngo; Kwan, Joe W; Levinton, Fred

At the Lawrence Berkeley National Laboratory (LBNL) adiagnostic neutral beam injection system for measuring plasma parameters,flow velocity, and local magnetic field is being developed. High protonfraction and small divergence is essential for diagnostic neutral beams.In our design, a neutral hydrogen beam with an 8 cm x 11 cm (or smaller)elliptical beam spot at 2.5 m from the end of the extraction column isproduced. The beam will deliver up to 5 A of hydrogen beam to the targetwith a pulse width of ~;1 s, once every 1 - 2 min. The H1+ ion species ofthe hydrogen beamwill be over 90 percent. For this application, we havecompared two types of RF driven multicusp ion sources operating at 13.56MHz. The first one is an ion source with an external spiral antennabehind a dielectric RF-window. The second one uses an internal antenna insimilar ion source geometry. The source needs to generate uniform plasmaover a large (8 cm x 5 cm) extraction area. We expect that the ion sourcewith internal antenna will be more efficient at producing the desiredplasma density but might have the issue of limited antenna lifetime,depending on the duty factor. For both approaches there is a need forextra shielding to protect the dielectric materials from the backstreaming electrons. The source walls will be made of insulator materialsuch as quartz that has been observed to generate plasma with higheratomic fraction than sources with metal walls. The ion beam will beextracted and accelerated by a set of grids with slits, thus forming anarray of 6 sheet-shaped beamlets. The multiple grid extraction will beoptimized using computer simulation programs. Neutralization of the beamwill be done in neutralization chamber, which has over 70 percentneutralization efficiency.

• Research Organization: Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: DE-AC02-05CH11231
• OSTI ID: 925529
• Report Number(s): LBNL-62477; R&D Project: Z2IS29; BnR: 600301010; TRN: US0803052
• Resource Relation: Conference: 12 International Conference on Ion Sources, ICIS,Jeju, Korea, August 26-31, 2007
• Country of Publication: United States
• Language: English

Related Subjects

43
70
ANTENNAS
BEAM INJECTION
COMPUTERIZED SIMULATION
DIELECTRIC MATERIALS
EFFICIENCY
ELECTRONS
EXTRACTION COLUMNS
GEOMETRY
HYDROGEN
ION BEAMS
ION SOURCES
LIFETIME
MAGNETIC FIELDS
PLASMA DENSITY
PROTONS
QUARTZ
SHIELDING
TARGETS
VELOCITY
Neutral Beams Plasma magnetic field diagnostics RF drivenmulticusp ion source