R & D Status of Beam Neutralization System M. Sasao, K. Shinto, M R & D Status of Beam Neutralization System M. Sasao, K. Shinto, M. Okamoto, S. Kitajima, N. Tanaka, M. Nishiura, O. Kaneko, H. Sakakida, and M. Wada Tohoku Univ. NIFS, AIST,and Doshisha Univ. OUTLINE Concept Development of a He- beam Development of a HeH+ beam Measurement of He* fraction Summary and Future work

Concept of a He- beam He++ + He0 => He0 + He++ Typical Beam parameter: He0, from auto-detached He-, 10 mA, 5cm x 20cm, 0.1 mA/cm2 Accelerated up to 1.5-1.8 MeV He0 in the ground state He++ + He0 => He0 + He++ Beam dump Analyzer Beam Source 26 m He++ + He0 => He0 + He++ RFQ + HV stage (above) 1m x 1m  + 1m x 1m x 3m Measuring point Detection point

Development of a He- beam (1) M. Sasao, K. Shinto, et al. Milestones Ion source Double focus mass separator/lens He+ beamlets Main acceleration Lens Na/Rb cell Free flying tube Pencil beam system for POP Optimization of He+ beam Characterization of beams Optimization of Alkali gas cell Phase space change by charge exchange cell Optimaization of Beam optics Measurement of metastable fraction Full Size He+ source Test at NIFS NBI test stand SDS(System Design Study) for ITER He-,He0 He+ 10 mA He+ 10 A He- Tohoku Univ. He- Test System

Development of a He- beam (2) Pencil beam system for POP 飛行管用貫通孔（隣の実験室へ） He+イオン源 偏向電磁石 アルカリ金属ガスセル 絶縁碍子上に高圧ステーションを構成(100-200kV)

Development of a He- beam (3) Full Size model 飛行管用貫通孔（隣の実験室へ） He+イオン源 偏向電磁石 アルカリ金属ガスセル 絶縁碍子上に高圧ステーションを構成(100-200kV)

Concept of a HeH+ beam Separation Acceleration Neutralization 10% HeH+ 2 mA/cm2 He0 0.2 mA/cm2 Separation Acceleration Neutralization 10% Typical Beam parameter: He0, from a HeH+, 20 mA, 5cm x 20cm, 0.2 mA/cm2 Accelerated up to 1.5-1.8 MeV He0 in the ground state Produced He0 beam energy (keV) RFQ + HV stage (above) 1m x 1m  + 1m x 1m x 3m Measuring point Detection point

Development of a HeH+ beam H. Sakakida, et al. The conditions producing HeH+ beam were not investigated in detail as yet. Therefore, the optimum conditions to extract HeH+ beam have been explored using our beam system. In order to measure beam species, mass spectrometer, whose energy range is limited less than 500 eV, is used. Therefore, DC power supply of 300 V is used for the beam acceleration (here, -4.5 kV is applied to the deceleration electrode for efficient beam extraction). Figure shows the number of HeH+, He+ and H+ ions as a function of He gas pressure ratio to the total gas pressure of the mixture gas (He and H2) in the case of low energy 300 eV and ~6 A beam. It is clear that the production rate of HeH+ increases, when He pressure ratio is larger than ~75 %. In the case of 90 % ratio, the number of HeH+ particles corresponds to ~15 % of total counts for HeH+, He+ and H+ ions. In the case of high energy 25 keV beam, if 15 % of the total current of 40 A, (which includes H+, H2+, H3+, He+ and HeH+ components) is the HeH+ component, the current density of HeH+ is ~13 mA/cm2, which is sufficient for the primary beam in the measurement of ITER.

Measurement of He* fraction M. Okamoto

Summary and crucial issues Development of a He- beam is on going in 3 sub-groups in parallel, [1] Pencil beam system for Proof Of Principle [2] Full Size He+ source [3] System Design Study for ITER The option of a HeH+ source is promising as an alternative probing beam. Several measurement methods of He* fraction are proposed and their principles will be tested.

Summary and crucial issues Development of a He- beam is on going in 3 sub-groups in parallel, [1] Pencil beam system for POP [2] Full Size He+ source [3] System Design Study for ITER The option of a HeH+ source is promising as an alternative probing beam. Several measurement methods of He* fraction are proposed and their principles will be tested. It is crutial to keep a tangential port at #6. Is it possible to send the argument- from diagnostic point of veiw? (although 99% is on the current drive, and blanket test.) Example: Various important phenomena which should be studied on ITER require 2D imaging. A tangential port can be used for various 2D imaging (X-ray, VUV, visible, bolometric, neutrons, gamma’s, etc.), in addition to the beam alpha-particle diagnostics.

Summary and Future work It is crutial to keep a tangential port at #6. -

Conclusion

Conclusion

Conclusion

Conclusion