Energy composition of high-energy neutral beams on the COMPASS tokamak

Mitošínková, K.; Ştöckel, J.; Varju, J.; Weinzettl, V.

doi:10.1515/nuka-2016-0069

Cited by 5 publications

(4 citation statements)

References 5 publications

(7 reference statements)

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“…The Doppler-shifted line intensities are proportional to the ion beam composition and the line broadening varies with the beamlet divergence ξ, as seen in the following formulas. A more detailed description of the spectral analysis process is given in [15], which is based on [16][17][18], exploiting cross sections from [19,20].…”

Section: Nbi Parametersmentioning

confidence: 99%

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Characterisation of the auxiliary heating power delivered by the 40 keV neutral beam injectors on the COMPASS tokamak

Bogár¹,

Varju²,

Havlíček³

et al. 2022

Plasma Phys. Control. Fusion

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Two identical neutral beam injectors (NBI) have been installed on the COMPASS tokamak. Each of them is capable of producing a deuterium (or hydrogen, helium) neutral beam with nominal power of up to 400 kW at 40 keV. Since the COMPASS tokamak is a compact machine the neutral beams’ design was carefully optimized to fit the neutral beam through the narrow ports of the tokamak. However, once the neutral beams are operated out of the scope of their optimal parameters, additional power losses due to the neutral beam scraping occur. The article investigates the amount of power losses due to neutral beam scraping. The losses are calculated by the neutral beam models and measured neutral beams parameters. The calculation results are compared with the measured power delivered into the plasma. There are two different neutral beam models employed. One describes neutral beam as a sum of small beamlets, which are Gaussian-like. Second one describes neutral beam a single Gaussian beam. The amount of the power lost to scraping is determined by both models and compared. Neutral beam parameters, input parameters for both models, are derived from the Doppler-shifted spectra emitted by fast neutral atoms. It is shown that when operating NBIs at nominal parameters, the scraping losses are negligible (<5% ). If the NBIs are operated to far from the nominal parameters, the scraping losses can reach up to ∼60% of the NBI output power. As the highest fractional losses occur with low power NBI, the beam duct is capable to withstand the corresponding power loads. The expected auxiliary heating power PAUX, the power entering the tokamak chamber carried by fast neutrals, is benchmarked against the additional plasma input power observed on the measured plasma parameters PNBI. The additional plasma input power PNBI is derived from the plasma power balance....

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Section: Nbi Parametersmentioning

confidence: 99%

“…The first results for NBI1 have been published with more detailed description of the used method in [15]. Figure 6 presents the measured parameters of NBI2 and figure 7 presents an extended data-set of NBI1.…”

Section: Nbi Parametersmentioning

confidence: 99%

Characterisation of the auxiliary heating power delivered by the 40 keV neutral beam injectors on the COMPASS tokamak

Bogár¹,

Varju²,

Havlíček³

et al. 2022

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

show abstract

“…A fractional composition of the two deuterium heating beams (up to 40 kV, 12 A) is derived from peak ratios of the Doppler red-shifted Dα line above 656 nm corresponding to individual beam components (D + , D + 2 , D + 3 , D 2 O + ) [47]. Measurements are performed by the HR2000+ spectrometer (FWHM about 0.06 nm) observing the beam at 45 • .…”

Section: Upgrade Of Particle and Beam Diagnosticsmentioning

confidence: 99%

Progress in diagnostics of the COMPASS tokamak

et al. 2017

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“…Main parameters of NBI 0 installed at the COMPASS tokamak. of the Doppler-shifted D α lines[12,13]: the higher the energy of the neutral, the larger its Doppler shift. The line-radiation is emitted by the formed NBI fast neutrals when their electron goes from an excited state to the ground state.…”

mentioning

confidence: 99%

Numerical modelling for beam duct heat loads calculations and application to the new 1 MW neutral beam injector in the COMPASS tokamak

Jaulmes¹,

Zadvitskiy²,

Bogár³

et al. 2022

Plasma Phys. Control. Fusion

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We introduce detailed numerical modelling of the fast neutral particles inside the duct of a new Neutral Beam Injector (NBI) recently installed at the COMPASS tokamak (major radius R0 = 0.56 m, vessel midplane minor radius a = 0.23 m, toroidal field Bt = 0.9 − 1.5T). This new NBI system is able to deliver 1MW power to the plasma at nominal injection energy of 80 keV. Collisions with the background neutrals inside the beam duct give birth to fast ions according to the density of the gas and tabulated cross-sections. The ion trajectories are then computed in the complete 3D magnetic field, showing the importance of the stray magnetic field and the magnitude of the field within the gap in between toroidal coils. During the experimental campaign dedicated to the new 1MW NBI, the beam duct heating was measured by a row of thermocouples located on the top-half of the beam duct. The fast ions collisions with the duct wall cause a local temperature increase with a characteristic pattern. In COMPASS, the location of the fast ions power deposition measured experimentally is in qualitative agreement with modelling of ion losses when following them after the re-ionization process. We trace back the details of the orbits corresponding to deposition at the hot-spot inside the beam duct. Quantitative comparison between the experiment and the simulation shows that a larger than expected amount of neutral gas was inside the duct and this study will guide the design of the future NBI duct in COMPASS Upgrade.

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Energy composition of high-energy neutral beams on the COMPASS tokamak

Cited by 5 publications

References 5 publications

Characterisation of the auxiliary heating power delivered by the 40 keV neutral beam injectors on the COMPASS tokamak

Characterisation of the auxiliary heating power delivered by the 40 keV neutral beam injectors on the COMPASS tokamak

Progress in diagnostics of the COMPASS tokamak

Numerical modelling for beam duct heat loads calculations and application to the new 1 MW neutral beam injector in the COMPASS tokamak

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