Pellet fuelling requirements to allow self-burning on a helical-type fusion reactor

Sakamoto, R.; Miyazawa, J.; Yamada, H.; Masuzaki, S.; Sagara, A.

doi:10.1088/0029-5515/52/8/083006

Cited by 19 publications

(25 citation statements)

References 19 publications

(24 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…2). Second, the density is further increasing to about 70% above the value before pellet EX/P5-1 injection on a much longer time scale (~400ms) consistent with earlier observation [11]. On the same time scale, the temperatures recover.…”

Section: Pellet Fueling In the Large Helical Devicesupporting

confidence: 87%

The effect of transient density profile shaping on transport in large stellarators and heliotrons

Dinklage¹,

Sakamoto²,

Yokoyama³

et al. 2017

Nucl. Fusion

Self Cite

View full text Add to dashboard Cite

Transport studies of pellet fuelling e xperiments on LHD are reported. Spatio-temporal evolutions after pellet in jection into LHD discharges show cases with central density increase on the time scale of particle transport processes. Both the temperature grad ient and the density gradient change during the density relaxation, the latter even in sign. The resulting thermodynamic forces influence radial electric fields-both as a driving term but also by, e.g., affecting the E r dependence of ion transport. Magnetic fluctuations have been found to be induced by pellet inject ion but to die out with the relaxation of the pressure profile.

show abstract

Section: Pellet Fueling In the Large Helical Devicesupporting

confidence: 87%

The effect of transient density profile shaping on transport in large stellarators and heliotrons

Dinklage¹,

Sakamoto²,

Yokoyama³

et al. 2017

Nucl. Fusion

Self Cite

View full text Add to dashboard Cite

show abstract

“…A more quantitative treatment of the effects of transient density profile shaping in LHD had been published before [17], also taking into account the mutual interaction between plasma transport as a function of the plasma parameters, and the profile perturbation by pellets. The interplay between pellet re-fuelling and density relaxation phenomena, with focus on the requirements of a burning fusion plasma, is presented in detail in [18]. In order not to repeat the arguments developed there, we restrict ourselves here to the description of the observed phenomena, and their possible implications for the technique of pellet series injection.…”

Section: Density Profile Effectsmentioning

confidence: 99%

Particle fueling experiments with a series of pellets in LHD

Baldzuhn

Damm

Dinklage

et al. 2018

Plasma Phys. Control. Fusion

View full text Add to dashboard Cite

Ice pellet injection is performed in the heliotron LHD (Large Helical Device) [1,2]. The pellets are injected in short series with up to 8 individual pellets. Parameter variations are performed for the pellet ice isotopes, the LHD magnetic configurations, the heating scenario, and some others. These experiments are performed in order to find out, whether deeper fuelling can be achieved with series of pellets compared to single pellets. An increase of the fuelling efficiency is expected since pre-cooling of the plasma by the first pellets within a series could help for deeper penetration of the later pellets in the same series. In addition these experiments have to show up, which boundary conditions must be fulfilled to optimize that technique. The high-field side injection of pellets, as proposed for deep fuelling in a tokamak, will not be feasible with the same efficiency in a stellarator or heliotron, because there the magnetic field gradient is smaller than in a tokamak of comparable size. Hence, too shallow pellet fuelling, in particular in a large device or a fusion reactor, will be an issue that can be overcome only by extremely high pellet velocities, or other techniques that will have to be developed in the future. It turned out that the fuelling efficiency can be enhanced by injection of a series of pellets, however further investigations will be needed in order to optimize this approach to deep particle fuelling.

show abstract

“…In order to predict the burning plasma properties on the basis of the LHD experiments, the direct profile extrapolation (DPE) method [5], in which the normalized plasma pressure profile obtained from the LHD experiment is directly extrapolated into a burning plasma by assuming gyro-Bohm type parameter dependence, has been extended to a dynamic plasma profile analysis. A similar analysis method was adopted in a previous paper [6], but an evaluation method for the particle diffusion coefficient, which impacts the fueling efficiency, has been updated in this paper. The principal justifications for the DPE method are based on the facts that (i) the LHD plasma shows gyro-Bohm type parameter dependence under wide experimental conditions, (ii) the collisionality of the selfburning plasma in a helical reactor (ν * b ∼ 0.1 − 0.4) is within the range of collisionality in the LHD experimental regime, 0.01 and (iii) the heating power density of the LHD experiments, 0.25∼0.5 MW/m 3 , corresponds to that of the self-burning plasma.…”

Section: A Modelmentioning

confidence: 99%

“…Since this model supposes similarity in the plasma pressure profile between the LHD plasma and the burning plasma, the pressure profile of the burning plasma can be extrapolated directly without consuming much computing time. This extrapolation method has been extended to a dynamic plasma profile analysis taking into account the source profile of the fueling and the diffusive nature of plasma particle confinement [6], [7]. In this study, possible gaps between the current LHD experiment and the reactor operation have been investigated using the above mentioned dynamic profile extrapolation model.…”

Section: Introductionmentioning

confidence: 99%

Prospects for Self-Burning Operation in Heliotron-Type Fusion Reactor

Sakamoto

Yamada

2016

IEEE Trans. Plasma Sci.

View full text Add to dashboard Cite

Possible gaps between the current LHD experiment and the reactor operation have been investigated using the dynamic profile extrapolation model, which is validated by LHD experiments. Self-burning solutions can be achieved under the wide range of fueling conditions. However, the minimum fusion output is rather high and it may be incompatible with the allowable heat load to the in-vessel components. In order to meet the conditions, improvement of the confinement properties or increase of the magnetic field strength is required. In addition, auxiliary heating is one of the effective means for reducing the minimum fusion output by substituting fusion alpha heating, although this means abandoning the advantage of self-burning capability. Fuel dilution is enhanced due to the source profile effects of the alpha particle that is generated in the core plasma and fuel which must be injected from the periphery. In order to mitigate the fuel dilution to below an acceptable level, sufficient fuel re-circulation is required even if it leads to reduction of burning efficiency.

show abstract

Pellet fuelling requirements to allow self-burning on a helical-type fusion reactor

Cited by 19 publications

References 19 publications

The effect of transient density profile shaping on transport in large stellarators and heliotrons

The effect of transient density profile shaping on transport in large stellarators and heliotrons

Particle fueling experiments with a series of pellets in LHD

Prospects for Self-Burning Operation in Heliotron-Type Fusion Reactor

Contact Info

Product

Resources

About