Development of a high current H− ion source for cyclotrons

Abstract

A multi-cusp DC H(-) ion source has been designed and fabricated for medical applications of cyclotrons. Optimization of the ion source is in progress, such as the improvement of the filament configuration, magnetic filter strength, extraction electrode's shape, configuration of electron suppression magnets, and plasma electrode material. A small quantity of Cs has been introduced into the ion source to enhance the negative ion beam current. The ion source produced 16 mA of DC H(-) ion beam with the Cs-seeded operation at a low arc discharge power of 2.8 kW.

Present status of numerical modeling of hydrogen negative ion source plasmas and its comparison with experiments: Japanese activities and their collaboration with experimental groups

“…It should be noted that the validations have been done not in one discharge/source condition, but multi-source comparisons have been done up to now. In other words, the KEIO-MARC code has been already applied to many arc-discharge sources in different applications, e.g., QST (National Institute for Quantum and Radiological Science and Technology) 10A Ion source [21,25], JT-60SA Kamaboko source [22,23], and NIFS (National Institute for Fusion Science) 1/2 R&D (Research and Development) source [51] for the plasma heating in magnetic fusion devices, and SHI (Sumitomo Heavy Industry) compact source [17,18] for the medical application as mentioned in section 1.…”

“…Various examples of the model validation will be shown through comparisons with experiments and also how modeling studies contribute to the improvement of source performances.As for the multi-cusp arc-discharge source, we will first show a systematic study to help us understand the role of the EEDF on the H − VP in section 2.2. The study has been carried out for a compact multi-cusp arcdischarge source (SHI H − source: Sumitomo Heavy Industry H − source [17,18]) for medical application such as boron neutron capture therapy and the radioisotope production for molecular imaging technology.The SHI H − source is a typical tandem type H − source [19]. In such a tandem type volume sources, the plasma source volume is divided into two regions by the transverse magnetic field (the so-called magnetic filter filed: MF-field) to control the EEDFs and to promote the two step H − VP reactions explained above.…”

“…As for the multi-cusp arc-discharge source, we will first show a systematic study to help us understand the role of the EEDF on the H − VP in section 2.2. The study has been carried out for a compact multi-cusp arcdischarge source (SHI H − source: Sumitomo Heavy Industry H − source [17,18]) for medical application such as boron neutron capture therapy and the radioisotope production for molecular imaging technology.…”

Development of a 20 mA negative hydrogen ion source for cyclotrons

“…Since the addition of cesium (Cs) into this type of source is known to increase the H − production rate on the surface of the plasma electrode [1], Cs-free and Cs-seeded operations have been tested on our source. 15 mA of H − beam current is obtained at an arc power of 6.5 kW in Cs-free operation by the optimization of the filter magnet [2]. H − beam current reached 22 mA at a lower arc power of 2.6 kW with fewer co-extracted electrons and a lower gas flow rate in Cs-seeded operation [3].…”

“…Dipole magnets referred to as filter magnets are located at the extraction region of the chamber to create a magnetic filter field [7] perpendicular to the central axis of the chamber. The magnetic filter field is optimized so as to maximize the arc efficiency, defined as the ratio of the beam current to the arc power in Cs-free operation [2]. Effects of magnetic filter strength and arc power on H − production in Cs-free operation have also been studied by KEIO-MARC code [8,9].…”