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. WadaTohoku 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

2/1410th ITPA diagnostics meeting , Moscow 10-14/04/06 M. Sasao

Concept of a He- beam

Beam dump

Analyzer

BeamSource

26 m

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 MeVHe0 in the ground state

He++ + He0 => He0 + He++

Measuringpoint

RFQ + HV stage (above)1m x 1m + 1m x 1m x 3m

Detectionpoint

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Development of a He- beam (1) M. Sasao, K. Shinto, et al.

• Pencil beam system for POP Pencil beam system for POP – Optimization of HeOptimization of He++ beam beam– Characterization of beamsCharacterization of beams– Optimization of Alkali gas cellOptimization of Alkali gas cell– Phase space change by charge Phase space change by charge

exchange cellexchange cell– Optimaization of Beam opticsOptimaization of Beam optics– Measurement of metastable fractMeasurement of metastable fract

ionion

• Full Size He+ sourceFull Size He+ source Test at NIFS NBI test standTest at NIFS NBI test stand

• SDS(System Design Study) foSDS(System Design Study) for r ITERITER

MilestonesMilestones

Ion source

Double focus mass separator/lens

He+ beamlets

Main acceleration

Lens

Na/Rb cell

Lens

Free flying tube

Tohoku Univ. HeTohoku Univ. He-- Test System Test System

10 mA He+He-,He0

He+

10 A He-

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Development of a He- beam (2)

Pencil beam system for POPPencil beam system for POP

絶縁碍子上に高圧ステーションを構成 (100-200kV)

He+ イオン源アルカリ

金属ガスセル

偏向電磁石

飛行管用貫通孔（隣の実験室へ）

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Development of a He- beam (3)

Full Size modelFull Size model

絶縁碍子上に高圧ステーションを構成 (100-200kV)

He+ イオン源アルカリ

金属ガスセル

偏向電磁石

飛行管用貫通孔（隣の実験室へ）

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Concept of a HeH+ beam

Typical Beam parameter:He0, from a HeH+, 20 mA, 5cm x 20cm, 0.2 mA/cm2

Accelerated up to 1.5-1.8 MeVHe0 in the ground state

Measuringpoint

RFQ + HV stage (above)1m x 1m + 1m x 1m x 3m

DetectionpointProduced He0 beam energy (keV)

HeH+

2 mA/cm2He0

0.2 mA/cm2

SeparationAcceleration

Neutralization 10%

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Development of a HeH+ beam H. Sakakida, et al.

In the case of high energy 25 keV beam, if

15 % of the total current of 40 A, (which in

cludes H+, H2+, H3

+, He+ and HeH+ compon

ents) is the HeH+ component, the current

density of HeH+ is ~13 mA/cm2, which is s

ufficient for the primary beam in the meas

urement of ITER.

The conditions producing HeH+ beam were not inves

tigated in detail as yet. Therefore, the optimum condit

ions to extract HeH+ beam have been explored using

our beam system.

In order to measure beam species, mass spectromet

er, whose energy range is limited less than 500 eV, is

used. Therefore, DC power supply of 300 V is used fo

r the beam acceleration (here, -4.5 kV is applied to

the deceleration electrode for efficient beam extractio

n). 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, th

e number of HeH+ particles corresponds to ~15 % of t

otal counts for HeH+, He+ and H+ ions.

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Measurement of He* fraction M. Okamoto

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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[1] Pencil beam system for Proof Of Principle

[2] Full Size He[2] Full Size He++ source source

[3] System Design Study for ITER[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.

10/1410th ITPA diagnostics meeting , Moscow 10-14/04/06 M. Sasao

Summary and crucial issues

• Development of a He- beam is on going in 3 sub-groups in parallel, [1] PenPencil beam system for POPcil beam system for POP

[2] Full Size He[2] Full Size He++ source source [3] System Design Study for [3] System Design Study for ITERITER

• The option of a HeH+ source is promising as an alternative probing beam. • Several measurement methods of He* fraction are proposed and their princi

ples 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 ima

ging.

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.

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Summary and Future work

• It is crutial to keep a tangential port at #6. -

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Conclusion

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Conclusion

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Conclusion

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Conclusion