Development of a plasma generator for a long pulse ion source for neutral beam injectors

Abstract

A plasma generator for a long pulse H(+)/D(+) ion source has been developed. The plasma generator was designed to produce 65 A H(+)/D(+) beams at an energy of 120 keV from an ion extraction area of 12 cm in width and 45 cm in length. Configuration of the plasma generator is a multi-cusp bucket type with SmCo permanent magnets. Dimension of a plasma chamber is 25 cm in width, 59 cm in length, and 32.5 cm in depth. The plasma generator was designed and fabricated at Japan Atomic Energy Agency. Source plasma generation and beam extraction tests for hydrogen coupling with an accelerator of the KSTAR ion source have been performed at the KSTAR neutral beam test stand under the agreement of Japan-Korea collaborative experiment. Spatial uniformity of the source plasma at the extraction region was measured using Langmuir probes and ±7% of the deviation from an averaged ion saturation current density was obtained. A long pulse test of the plasma generation up to 200 s with an arc discharge power of 70 kW has been successfully demonstrated. The arc discharge power satisfies the requirement of the beam production for the KSTAR NBI. A 70 keV, 41 A, 5 s hydrogen ion beam has been extracted with a high arc efficiency of 0.9 -1.1 A/kW at a beam extraction experiment. A deuteron yield of 77% was measured even at a low beam current density of 73 mA/cm(2).

Commissioning of the first KSTAR neutral beam injection system and beam experiments

“…The ion source consists of a large bucket as a plasma generator [5] and a tetrode accelerator system for the beam extraction. All the elements that constitute the ion source are designed to cope with 300 s beam extraction, essentially steady-state operation.…”

“…A bucket type positive ion source was developed by KAERI from an early stage of the KSTAR construction phase [2], and a hydrogen ion beam has been demonstrated with a current of 55 A at an energy of 100 keV and a pulse duration of 2 s. An extended pulse duration of 300 s was also achieved for the lowered beam energy of 90 keV and 33 A of beam current [3]. More recently, the ion source bucket chamber was substantially replaced by a new one [4,5] to enhance the arc efficiency. The new ion source bucket chamber was developed by Japan Atomic Energy Agency (JAEA) in accordance with Korea-Japan fusion collaboration.…”

The Arc Regulation Characteristics of the High-Current Ion Source for the EAST Neutral Beam Injector

“…According to accelerator physics and classical probe measurement theory [7,11] , the ion beam density and probe ion saturation current can be calculated with Eqs. ( 1) and (2),…”

Performance of a New Ion Source for KSTAR Tokamak Plasma Heating

“…The main parameters and details of the new ion source can be found in Table 1. The plasma generator for the new ion source has the same design concept as the plasma generator for the prototype ion source, which has been developed by JAEA (Japan Atomic Energy Agency) [12] in Japan. The plasma generator consists of an anode arc chamber and cathode filament assemblies.…”