Methods of beam emittance measurements of high power negative ion beams for NBIs

Saquilayan, G. Q.; Kashiwagi, M.; Tobari, H.; Hoshino, Junichi; Ichikawa, Masahiro; Umeda, N.; Watanabe, K.; Wada, M.; Sasao, M.

doi:10.1063/1.5083748

Cited by 4 publications

(5 citation statements)

References 7 publications

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“…The design for the emittance measurement is reconsidered from the previous one [7] with the objective to investigate the peripheral region of the beam. First, to minimize the possible overlapping of signals in the emittance patterns of a pepper pot arrangement, 1 mm diameter pinholes and the distances of their spacing were examined.…”

Section: Experimental Setup and Beam Diagnostics For High Power Beamsmentioning

confidence: 99%

“…For the beam acceleration test, the accelerator was modified by reducing the gap length from 109 mm to 88 mm, to optimize the beam optics for higher beam current acceleration at the target perveance for the ITER accelerator. The beam optics was analyzed using a two-dimensional (2D) beam trajectory analysis code BEAMORBT [7]. Figure 3 shows the beam trajectories at the minimum divergence angle for the H-beam with the currents and energies of 200 A/m 2 and 1 MeV for the gap of 109 mm and 230 A/m 2 870 keV for the gap of 88 mm.…”

Section: Beam Acceleration Under Perveance Matched Condition With Itermentioning

confidence: 99%

“…In the conventional measurement of the beam footprint visualized through an infrared (IR) camera, the peripheral of the beam footprint could not be clearly determined whether it is a divergent beam component or measurement background noise. To understand the divergent beam components, an emittance measurement system using one-dimensional carbon-fiber-composite (1D-CFC) plates have been newly developed to measure high power beams of 200 MW/m 2 [7]. In this paper, improvements were applied to the emittance measurement aiming to measure the peripheral region of the beam.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

High Power Density Beam Measurement of a Single Beamlet Multi-Grid Prototype H^- Negative Ion Accelerator

Saquilayan

Kisaki

Kojima

et al. 2022

J. Phys.: Conf. Ser.

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Beam optics of the ITER prototype accelerator with 88 mm acceleration gap length has been examined through H- beam acceleration tests at the ITER target beam perveance. The beam optics has been examined for beam energies up to 790 keV under the ITER target perveance. The total grid heat load was successfully reduced to 10 %, which was lower than the allowable value of 15 %. The beam emittance of the ITER perveance has been measured for the first time by using newly developed emittance measurement system consisting of carbon-fiber-composite (CFC) plate with pin-holes. The emittance of 790 keV H- beam shows the divergence angle of the beam core is satisfied with the ITER requirement of <7 mrad. Measurement at the beam periphery was made possible by modifying the pin-hole size of pepper-pot apertures, and the observed divergent components were 20 mrad. The ratio of the diverged beam became lower with the increase of the beam energy. This result contributes the design of the ITER accelerator and the beam line components.

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Section: Experimental Setup and Beam Diagnostics For High Power Beamsmentioning

confidence: 99%

Section: Beam Acceleration Under Perveance Matched Condition With Itermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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High Power Density Beam Measurement of a Single Beamlet Multi-Grid Prototype H^- Negative Ion Accelerator

Saquilayan

Kisaki

Kojima

et al. 2022

J. Phys.: Conf. Ser.

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“…As well as posing issues for meeting homogeneity targets, this creates difficulties with diagnosing a beam comprised of potentially hundreds of beamlets, as it is typically only possible to perform measurements on collections of beamlets. Whilst diagnostics do exist that are able to resolve individual beamlets through calorimetric measurement [15,31,32], these are necessarily placed within a few cm of the extraction system, where beamlets have not yet merged, and power densities can be in excess of 10 MW m −2 [33]. Probe type diagnostics are not able to survive such high heat loads, and so they require either a modification of the ion source or a reduction of the ion current below the optimum to operate.…”

Section: Generating and Diagnosing Large Negative Ion Beamsmentioning

confidence: 99%

“…Despite these issues, low values of divergence have been measured at a number of facilities. A 900 keV negative ion beam was extracted from 15 apertures with an estimated beamlet divergence of less than 7 mrad (0.4°) at the MAMuG facility [15]. The NBI system on the Large Helical Device has demonstrated large beams with an estimated 4-6 mrad (0.23°-0.34°) beamlet divergence at 120 keV, with 5 grid segments each containing 168 apertures [16].…”

Section: Introductionmentioning

confidence: 99%

The particle tracking code BBCNI for large negative ion beams and their diagnostics

Hurlbatt

Harder

Wünderlich

et al. 2019

Plasma Phys. Control. Fusion

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Heating and current drive in the next generation tokamak ITER requires the use of large and powerful neutral beams, generated by a precursor ion beam from an ion source around 1 m × 2 m in cross-section. To avoid energy losses and component damage, strict requirements are placed on the divergence and uniformity of this ion beam, which is comprised of many individual beamlets. Understanding, controlling, and predicting the behaviour of these large ion beams requires knowledge of these individual beamlets and their interactions with one another. This is hindered by available experimental diagnostics on these large beams typically only having access to volume averaged information. A forward simulation of beam diagnostics would allow the connection of experimental results with otherwise unobtainable individual beamlet properties. The particle tracking and ray tracing code Bavarian Beam Code for Negative Ions was developed for this reason, and takes into account the interaction of individual component beamlets with whole-beam diagnostics to produce synthetic data that can be compared with experimental results. In this work a significantly reworked and upgraded version of the code is presented and example results are given and analysed for the ITER relevant test facility BATMAN Upgrade. It is shown how the simulation can recreate experimental results, and that one must consider the whole beam in order to do so. The impact of beamlet mixing on beam emission spectroscopy results is shown, as is the importance of long range magnetic fields on the beam transport. The capabilities and limitations of the code are discussed with a view toward application to ITER size ion sources.

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Study of beamlets extracted from a multi-aperture and five-stage acceleration system

Kashiwagi

Kisaki

Saquilayan

et al. 2022

Review of Scientific Instruments

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A beam optics study using the ITER-relevant high intense negative ion beams, such as 1 MeV, 200 A/m2, has been performed experimentally and analytically using a multi-aperture and five-stage accelerator. Initially, multi-beamlets generated from this accelerator were deflected in various directions due to the magnetic field and space charge repulsion between beams and showed various divergences. These had limited the pulse length and the beam energy. Compensation methods of the beamlet deflections have worked effectively and contributed to achieving the ITER requirement, the divergence angle of <7 mrad, and the deflection angle of <1 mrad for 1 MeV beam. The beam pulse has been gradually extended from 1 to 100 s and is now going to a longer pulse based on these results. One of the remaining issues is to understand and suppress peripheral components of the beam, namely, the halo, and to reduce the local heat loads observed around the aperture edge. This halo component has been successfully distinguished from the beam core by using a newly developed beam emittance measurement system for high intense beams. By combining this measured beam emittance and the beam simulation, it was clarified for the first time that the halo components are generated in an area of 1 mm width from the aperture edge.

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Methods of beam emittance measurements of high power negative ion beams for NBIs

Cited by 4 publications

References 7 publications

High Power Density Beam Measurement of a Single Beamlet Multi-Grid Prototype H^- Negative Ion Accelerator

High Power Density Beam Measurement of a Single Beamlet Multi-Grid Prototype H^- Negative Ion Accelerator

The particle tracking code BBCNI for large negative ion beams and their diagnostics

Study of beamlets extracted from a multi-aperture and five-stage acceleration system

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Methods of beam emittance measurements of high power negative ion beams for NBIs

Cited by 4 publications

References 7 publications

High Power Density Beam Measurement of a Single Beamlet Multi-Grid Prototype H- Negative Ion Accelerator

High Power Density Beam Measurement of a Single Beamlet Multi-Grid Prototype H- Negative Ion Accelerator

The particle tracking code BBCNI for large negative ion beams and their diagnostics

Study of beamlets extracted from a multi-aperture and five-stage acceleration system

Contact Info

Product

Resources

About

High Power Density Beam Measurement of a Single Beamlet Multi-Grid Prototype H^- Negative Ion Accelerator

High Power Density Beam Measurement of a Single Beamlet Multi-Grid Prototype H^- Negative Ion Accelerator