Control of post-disruption runaway electron beams in DIII-D

Eidietis, N. W.; Commaux, N.; Hollmann, E. M.; Humphreys, D. A.; Jernigan, T.C.; Moyer, R. A.; Strait, E. J.; Vanzeeland, M.; Wesley, J.C.; Yu, J. H.

doi:10.1063/1.3695000

Cited by 53 publications

(56 citation statements)

References 30 publications

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“…It is noteworthy that the horizontal drift we discussed here has drastically different physics with the force imbalance along major radius, which has been invoked when discussing the observed inward motion during plateau regime 16 . The fundamental physics here is the balance in canonical angular momentum budget, which can not be recovered by simply considering the runaway current as an ordinary current carrying circuit.…”

Section: Discussionmentioning

confidence: 99%

“…This inward drift will ultimately result in the intersection between runaway electrons and the wall, causing tremendous damage to the first wall due to its localized way of energy deposition 18 . The reason of this displacement is attributed to the force imbalance under externally generated vertical field 16 , while the possible role played by the dynamic of relativistic electrons in a self-generated magnetic field has not been fully explored.…”

Section: Introductionmentioning

confidence: 99%

“…However, the corresponding evolution in configuration space has not received due attention. During the aforementioned runaway current plateau, it is widely observed that there is a gradual inward drift of runaway current [15][16][17] . This inward drift will ultimately result in the intersection between runaway electrons and the wall, causing tremendous damage to the first wall due to its localized way of energy deposition 18 .…”

Section: Introductionmentioning

confidence: 99%

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On the inward drift of runaway electrons during the plateau phase of runaway current

Qin

2016

Physics of Plasmas

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The well observed inward drift of current carrying runaway electrons during runaway plateau phase after disruption is studied by considering the phase space dynamic of runaways in a large aspect ratio toroidal system. We consider the case where the toroidal field is unperturbed and the toroidal symmetry of the system is preserved.The balance between the change in canonical angular momentum and the input of mechanical angular momentum in such system requires runaways to drift horizontally in configuration space for any given change in momentum space. The dynamic of this drift can be obtained by integrating the modified Euler-Lagrange equation over one bounce time. It is then found that runaway electrons will always drift inward as long as they are decelerating. This drift motion is essentially non-linear, since the current is carried by runaways themselves, and any runaway drift relative to the magnetic axis will cause further displacement of the axis itself. A simplified analytical model is constructed to describe such inward drift both in ideal wall case and no wall case, and the runaway current center displacement as a function of parallel momentum variation is obtained. The time scale of such displacement is estimated by considering effective radiation drag, which shows reasonable agreement with observed displacement time scale. This indicates that the phase space dynamic studied here plays a major role in the horizontal displacement of runaway electrons during plateau phase.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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On the inward drift of runaway electrons during the plateau phase of runaway current

Qin

2016

Physics of Plasmas

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“…The thermal loading during the thermal quench [1,2,[9][10][11][12][13] can lead to severe melting or ablation of the plasma facing components, while the eddy currents driven by the current quench can lead to large forces on in-vessel structures [11]. Finally, it is possible for a large fraction of the plasma current to be converted to a runaway electron beam [1,2,[14][15][16][17][18][19][20][21][22][23], potentially leading to severe localized damage to invessel components if position control of the beam is not maintained [24].…”

Section: : Introductionmentioning

confidence: 99%

Dynamics of the disruption halo current toroidal asymmetry in NSTX

Gerhardt¹

2013

Nucl. Fusion

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This paper describes the dynamics of disruption halo current non-axisymmetries in the lower divertor of the National Spherical Torus Experiment [M. Ono, et al. Nuclear Fusion 40, 557 (2000)]. While. The halo currents typically have a strongly asymmetric structure where they enter the divertor floor, and this asymmetry has been observed to complete up to 7 toroidal revolutions over the duration of the halo current pulse. However, the rotation speed and toroidal extend of the asymmetry can vary significantly during the pulse. The rotation speed, halo current pulse duration, and total number of revolutions tend to be smaller in cases with large halo currents. The halo current pattern is observed to become toroidally symmetric at the end of the halo current pulse. It is proposed that this symmeterization is due to the loss of most or all of the closed field line geometry in the final phase of the vertical displacement event.

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“…Mechanical loading by induced eddy currents during the current quench [11][12][13][14][15][16] can create significant forces on in-vessel structures such as blanket modules [17]. Furthermore, during the current quench, the plasma current can be converted to a beam of runaway electrons [3,4,[18][19][20][21][22][23][24][25][26], with potential for severe damage if position control of the beam is lost and it strikes the first wall [27]. Finally, the plasma column often moves upward or downward during or proceeding the disruption, and makes contact with the first wall or divertor.…”

Section: : Introductionmentioning

confidence: 99%