Neutral Beam 

Neutral Beams: 

Neutral Beam Injection (NBI) involves the introduction of high-energy (neutral) atoms into the magnetically confined plasma. The atoms are immediately ionized and are trapped by the magnetic field. The high-energy ions then transfer part of their energy to the plasma particles in repeated collisions, thus increasing the plasma temperature.

The National Spherical Torus Experiment - Upgrade (NSTX-U) NBI system configuration consists of two beamlines connected to the NSTX-U vacuum vessel. Each beamline has three positive ion sources and associated components to form and accelerate a neutral beam, and to inject the neutral beam into NSTX-U plasmas in support of the experimental program. Each source can fire separately or in concert. The two beamlines can be operated together or each separately.

NSTX-U beamlines are supported by NBI engineering and subsystems including: deionized water, cryogenics, vacuum systems, gas injection, high and low voltage power supplies, and the locally operated control and monitoring system.

Neutral Beam Long Pulse Ion Sources: 

The long pulse ion source provides the accelerated particle beam used as the principal auxiliary plasma heating method on NSTX-U. The plasma generator and accelerator can deliver a 120 keV, 70 Ampere positive ion beam with half and third energy constituents to the beamline neutralizer. The resulting neutral beam, stripped of the remaining ions by the bending magnet, can then be injected into plasma or fired into the beamline calorimeter for beam conditioning purposes

The NBI system is capable of operation up to 120 keV for approximately 1 second and 80 keV for 5 seconds.  With six sources at 100 keV, the NBI system is capable of 15 MW injected neutral power in support of NSTX-U experiments.  Neutral beam injection has provided numerous benefits in heating, fueling, and adding torque to NSTX plasmas