Beam Species Measurements on the MAST NBI system. Brendan Crowley Thanks to R King (CCFE) and A Bharatti (IPR). Outline of discussion. Neutral beams at MAST Ion Source Configurations Beam Species Model Beam Spectroscopy Results. Neutral Beams at MAST. Two on axis beams
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Beam Species Measurements on the MAST NBI system
R King (CCFE) and A Bharatti (IPR)
How well they do this depends on:
Mostly we need to know:
Filament or RF driven discharge
Magnetic confinement achieved by using permanent magnets in multi-cusp configuration - strong field on the walls, field-free region in the centre of the source.
Ions created in various electron-molecule and ion-molecule collisions.
Typical ion source parameters:
Parameters determined by the ion source
(fixed magnetic configuration and gas flow):
Magnetic configuration of the standard MAST supercusp ion source.
Magnetic configuration of the new MAST supercusp ion source.
Beam emission shifted from Dα by
Source parameters : Species mix (H+:H2+:H3+);
Beam parameters : Perveance scans ( beam divergence );
Beam species distribution; Neutral beam fractions (H(E):H(E/2):H(E/3));Power fractions (P(E):P(E/2):P(E/3);
This particle has full energy, E
These have half energy, E/2
These have one third energy, E/3
There are three simple scenarios:
These three molecular ions have all been accelerated through the same potential, and therefore they all have the same energy. “E”.
The collisions with the neutraliser gas can cause the molecular ions to dissociate.
(Hik ,b )
DSS analysis : Corona model
H-alpha transition diagram
and power fractions
C2 and C3 are intensity multiplication factors and they depend on beam energy and target thickness.
Calculated Vs measured beam fractions
( 1X1016 molecules/cm2)
Estimation of Beam fractions
Beam fractions at 20KeV
Formulation : K H Berkner, R V Pyle and J W Stearns, 1975, Nuclear fusion, 249-254,15.
J Kim and H H Haselton, 1979, J.Appl.Phys,3802-3807,50.
Cross sections : C F Barnett, Atomic data for nuclear fusion, 1990,Volume.1,Report ORNL-6086/V1,
Oak ridge national laboratory.