Design Study for the Large Helical Device

Iiyoshi, A.; Fujiwara, Masami; Motojima, O.; Ohyabu, N.; Yamazaki, K.

doi:10.13182/fst90-a29179

Cited by 252 publications

(118 citation statements)

References 4 publications

Supporting

Mentioning

118

Contrasting

Order By: Relevance

“…The calculations in figure (1) are performed for the r/a = 0.5 surface of the LHD stellarator [41] in its standard configura- Table 1 of Ref. [4], whereas all harmonics with relative amplitude > 4 × 10 −5 are retained for the W7-X calculations.…”

Section: Comparison Of E R Termsmentioning

confidence: 99%

Comparison of particle trajectories and collision operators for collisional transport in nonaxisymmetric plasmas

et al. 2014

View full text Add to dashboard Cite

In this work, we examine the validity of several common simplifying assumptions used in numerical neoclassical calculations for nonaxisymmetric plasmas, both by using a new continuum drift-kinetic code and by considering analytic properties of the kinetic equation. First, neoclassical phenomena are computed for the LHD and W7-X stellarators using several versions of the drift-kinetic equation, including the commonly used incompressible-E × B-drift approximation and two other variants, corresponding to different effective particle trajectories. It is found that for electric fields below roughly one third of the resonant value, the different formulations give nearly identical results, demonstrating the incompressible E ×B-drift approximation is quite accurate in this regime. However, near the electric field resonance, the models yield substantially different results. We also compare results for various collision operators, including the full linearized Fokker-Planck operator. At low collisionality, the radial transport driven by radial gradients is nearly identical for the different operators, while in other cases it is found to be important that collisions conserve momentum.

show abstract

Section: Comparison Of E R Termsmentioning

confidence: 99%

Comparison of particle trajectories and collision operators for collisional transport in nonaxisymmetric plasmas

et al. 2014

View full text Add to dashboard Cite

show abstract

“…Note that the highest β value ever achieved in stellarators is about 5% [24,25]. Several years ago this was a level target for the largest stellarators [17,26]. Just for comparison: the reference operation of ITER is considered with β < 3% [27].…”

Section: General Relations and Assumptionsmentioning

confidence: 99%

Theory of Diamagnetic Signal in Current-Free Stellarators

Pustovitov

2010

Plasma and Fusion Research

View full text Add to dashboard Cite

The toroidal magnetic flux through the plasma column is calculated analytically for current-free stellarators of arbitrary geometry without assumptions on the plasma shape, aspect ratio, etc. This is done with accuracy sufficient for extracting the contribution due to the finite plasma pressure from this flux. The final result is a formula relating the measured diamagnetic signal with β, the ratio of the plasma pressure to the magnetic pressure. This formula is obtained assuming small β and the relative depth of the magnetic well. These are natural conditions for stellarators, therefore the final result can be recommended for magnetic diagnostics without practical limitations. Keywords: stellarator, magnetic diagnostics, diamagnetic signal, plasma equilibrium, current-free plasma DOI: 10.1585/pfr.5.S2054 InroductionDiamagnetic measurements are a traditional diagnostics used for determining the plasma energy content in tokamaks and stellarators [1][2][3][4][5]. Interpretation of the measurements are based on a simple formula originally derived for a circular plasma cylinder [6] 2 δΦwhere the measured diamagnetic signal is defined asB is the magnetic field, B v is the vacuum magnetic field, Φ 0 = B 0 S ⊥ with S ⊥ = πb 2 being the transverse crosssection of the plasma column, b is its minor radius, B 0 is the toroidal field, B J is the poloidal field at the plasma boundary due to the net toroidal current,β ≡ 2p/B 2 0 is the ratio of the volume-averaged plasma pressure p to the magnetic field pressure B 2 0 /2. It is known that Eq. (1) can be applied to large-aspectratio tokamaks with a circular plasma [7]. The same or slightly modified formula has been used for conventional stellarators [8][9][10], though the validity of Eq. (1) has been proved for straight stellarators only [11,12]. Strictly speaking, for stellarators with current-carrying plasma (B J 0) Eq. (1) should contain an additional term [11,12]. Here we consider the case when this contribution can be disregarded.The diamagnetic signal for arbitrary shape and aspect ratio current-free plasma in a toroidal conventional stellarator was calculated analytically in [13]. In analytical author's e-mail: pustovit@nfi.kiae.ru * permanent address: Russian Research Centre 'Kurchatov Institute', Pl. Kurchatova, Moscow, 123182, Russia theory, when a cylindrical result is generalized for account of the toroidal effects, this is usually done by large-aspectratio expansion. It was unexpected that the problem considered in [13] turned out to be solvable without this 'natural' simplification and even without any assumption on the plasma shape. The obtained result [13] was ready for practical use. Similar to (1), it directly relates the measured diamagnetic signal δΦ to the value of interest, the integral on the right hand side over the plasma volume. Here the constant F b = 2πrB t describes the vacuum toroidal field B t , r is the radius from the main vertical axis, and δ SH is a small correction related to the Shafranov shift and helical field. Later, numerical calculation...

show abstract

“…The device itself is very complex in design and construction, which is the main reason why development and implementation of stellarators is not very sought after. Experiments are still being carried out in Japan, at the Large Helical Device [7,8], and in Spain at the TJII [9,10]. The Wendelstein 7-X is currently being constructed in Germany.…”

Section: Nuclear Fusion and The Tokamak Reactormentioning

confidence: 99%

Repetitive operation of the University of Saskatchewan Compact Torus Injector

Pant

Hirose

Xiao

2010

Radiation Effects and Defects in Solids

View full text Add to dashboard Cite

Development of fueling technologies for modern and future tokamak reactors is essential for their implementation in a commercial energy production setting. Compared to the presently available fueling technologies, gas or cryogenic pellet injection, compact torus injection presents an effective and efficient method for directly fueling the central core of tokamak plasmas. Fueling of the central core of a tokamak plasma is pivotal for providing efficient energy production. The central core plasma of a reactor contains the greatest density of fusion processes. For consistent and continuous fueling of tokamak fusion reactors, compact torus injectors must be operated in a repetitive mode.The goal of this thesis was to study the feasibility of firing the University of Saskatchewan Compact Torus Injector (USCTI) in a repetitive mode. In order to enable USCTI to fire repetitively, modifications were made to its electrical system, control system and data acquisition system. These consisted primarily of the addition of new power supplies, to enable fast charging of the many capacitor banks used to form and accelerate the plasma. The maximum firing rate achieved on USCTI was 0.33 Hz, an increase from the previous maximum firing rate of 0.2 Hz achieved at UC Davis.Firing USCTI in repetitive modes has been successful. It has been shown that the CTs produced in any given repetitive series are properly formed and repeatable. This is made evident through analysis of data collected from the CTs' magnetic fields and densities as they traveled along the injector barrel. The shots from each experiment were compared to the series' mean data and were shown to be consistent over time.Calculations of their correlations show that there are only minimal deviations from shot to shot in any given series.ii

show abstract

Design Study for the Large Helical Device

Cited by 252 publications

References 4 publications

Comparison of particle trajectories and collision operators for collisional transport in nonaxisymmetric plasmas

Comparison of particle trajectories and collision operators for collisional transport in nonaxisymmetric plasmas

Theory of Diamagnetic Signal in Current-Free Stellarators

Repetitive operation of the University of Saskatchewan Compact Torus Injector

Contact Info

Product

Resources

About