Neutral beam injector research and development work in the USA Page: 4 of 8
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50-60 keV neutral beams for pulses of 0.5 sec (0.1 sec) for PDX (ISX).
The PDX system is in fabrication and assembly. LPT and TNS are in the
conceptual phase and half-scale ion sources are under test in the 100 kV
range, which will soon be extended to 150 keV.
An intense research and development program wih modified three-grid
duoPIGatron source  provided a dense (400 mA/cm ), uniform (+5%), and
quiescent (+10%) plasma from which 70 amperes of positive ions have been
extracted at 40 kV. The source has also been operated using deuterium un-
der similar conditions. Permanent magnets have been placed around the 2nd
anode region to produce a cusp field which confines the plasma in a highly
uniform manner. The source operation is characterized by moderate filament
and arc power requirements, high gas efficiency (50%) and a high degree of
reliability. The arc efficiency has been measured to be about 1 kW for
every ampere of extracted beam. Although the source has generally been
operated for pulse durations of 100 ms at 10% duty cycle, it has near dc
capabilities, and 40 A pulses of 500 ms duration have been extracted. A
smaller source has been operated for 10 s at 200 mA/cm2.
An outstanding feature of the ORNL source is its ability to provide
very high atomic yields, 85%. The high energy atomic fraction plays an
important part in beam penetration and power deposition in a tokamak plasma.
Control of the ion species will provide means of controlling the beam pene-
tration to match the varying tokamak plasma density.
Initial experiments in energy recovery employing crossed magnetic
field blocking of the electrons from the gas charge exchange cell have proved
successful. The un-neutralized component is collected at ground potential.
Energy recovery has been measured co be (40 + 20)%. A 200 keV, 100 A posi-
tive ion source with c.w. capability and energy recovery is in the design
stage. The entire 200 keV beam line is being redesigned to insure a high
efficiency system. Such a positive ion system with direct recovery effi-
ciency of -80% might well satisfy the injector requirements for heating
future reactor size tokamaks.
Future research and development plans also include simplifying and
increasing the reliability of 40 to 80 keV injector systems.
Computer simulations  are available and are found to be an ex-
tremely valuable aid in every phase of this program, both in predicting
and verifying systems performance.
3. NEUTRAL BEAM INJECTORS BASED ON NEGATIVE IONS
3.1 BNL Negative Ion Activities
The objective of the BNL program is todevelop multiampere (equivalent)
high-energy injection systems based on direct extraction from negative ion
plasma sources. Two types of direct extraction negative ion plasma sources
have been extensively investigated, namely the magnetron source and Penning
type source. Several improvements were implemented on these sources, which
are basically of the cold cathode type operating in a mixture of deuterium
gas and cesium vapor. These improvements (independent cesium vapor control,
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Pyle, R.V.; Baker, W.R. & Barr, W.L. Neutral beam injector research and development work in the USA, article, July 1, 1978; Berkeley, California. (https://digital.library.unt.edu/ark:/67531/metadc1182193/m1/4/: accessed April 21, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.