The Development of Shattered Pellet Injector on HL-2A

Xu, Huang; Nie, Lin; Zhu, G. L.; Chen, C. Y.; Wei, Pan; Liu, D. Q.; Cao, Z.; Xu, M.

doi:10.1080/15361055.2018.1554389

Cited by 15 publications

(7 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Both, experimental and numerical investigations have been carried out regarding the performance of SPI. As the first device to implement an SPI system, DIII-D has published extensive results on the SPI efficiency for both the TQ and the current quench (CQ) mitigation [8,[10][11][12][13][14], while several other devices around the world, including JET [5,14,15], K-STAR [16], HL-2A/2M [17], J-TEXT [18] and others, have been working intensively on the SPI scheme. On the other hand, 3D non-linear simulations has been used to look into the penetration, assimilation and radiation for both deuterium and impurity SPIs [9,[19][20][21] or massive material injections in general [22][23][24], providing insights into the MHD destabilization, transport and impurity radiation dynamics after the injection.…”

Section: Introductionmentioning

confidence: 99%

Radiation asymmetry and MHD destabilization during the thermal quench after impurity shattered pellet injection

Nardon

Hoelzl

et al. 2021

Nucl. Fusion

View full text Add to dashboard Cite

The radiation response and the MHD destabilization during the thermal quench after a mixed species shattered pellet injection with impurity species neon and argon are investigated via 3D non-linear MHD simulation using the JOREK code. Both the n = 0 global current profile contraction and the local helical cooling at each rational surface caused by the pellet fragments are found to be responsible for MHD destabilization after the injection. Significant current driven mode growth is observed as the fragments cross low order rational surfaces, resulting in rapidly inward propagating stochastic magnetic field, ultimately causing the core temperature collapse. The thermal quench (TQ) is triggered as the fragments arrive on the q = 1 or q = 2 surface depending on the exact q profile and thus mode structure. When injecting from a single toroidal location, strong radiation asymmetry is found before and during the TQ as a result of the unrelaxed impurity density profile along the field line and asymmetric outward heat flux. Such asymmetry gradually relaxes over the course of the TQ, and is entirely eliminated by the end of it. Simulation results indicate that the aforementioned asymmetric radiation behavior could be significantly mitigated by injection from toroidally opposite locations, provided that the time delay between the two injectors is shorter than 1 ms. It is also found that the MHD response are sensitive to the relative timing and injection configuration in these multiple injection cases.

show abstract

Section: Introductionmentioning

confidence: 99%

Radiation asymmetry and MHD destabilization during the thermal quench after impurity shattered pellet injection

Nardon

Hoelzl

et al. 2021

Nucl. Fusion

View full text Add to dashboard Cite

show abstract

“…[2] To avoid such damages and safely guard the continued operation of future high performance devices, various disruption avoidance systems (DAS) are designed, such as the electron cyclotron current drive (ECCD) or Heating (ECRH), [3][4][5][6] to suppress the instability of the dominant magnetic islands by modifying the current and pressure profile within. Facing this, disruption mitigation systems (DMS) such as the shattered pellet injection (SPI) [7][8][9][10][11][12][13][14][15][16][17] or other massive material injection (MMI) [18][19][20][21][22][23][24][25] techniques are used to deplete the majority of thermal energy via radiation loss during the TQ, and raise the density to help with runaway electron suppression during the CQ phase.…”

Section: Introductionmentioning

confidence: 99%

Stability impacts from the current and pressure profile modifications within finite sized island

Sun

2023

Chinese Phys. B

View full text Add to dashboard Cite

The stability (or instability) of finite sized magnetic island could play a significant role in disruption avoidance or disruption mitigation dynamics. Especially, various current and pressure profile modifications, such as the current drive and heating caused by electron cyclotron wave, or the radiative cooling and current expulsion caused by the Shattered Pellet Injection could be applied within the island to modify its stability, thus change the ensuing dynamics. In this study, we calculate the mode structure modification caused by such profile changes within the island using the perturbed equilibrium approach, thus obtain the change of stability criterion ∆′ and assess the corresponding quasi-linear island stability. The positive helical current perturbation is found to always stabilize the island, while the negative one is found to do the opposite, in agreement with previous results. The pressure bump or hole within the island has a more complicated stability impact. In the small island regime, its contribution is monotonic, with pressure bump tends to stabilize the island while pressure hole destabilizes it. This effect is relatively weak, though, due to the cancellation of the pressure term’s odd parity contribution in the second derivatives of the mode structure. In the large island regime, such cancellation is broken due to the island asymmetry, and the pressure contribution to stability is manifested, which is non-monotonic. The stability analysis in this paper helps to more accurately clarify the expected island response in the presence of profile modifications caused by disruption avoidance or mitigation systems.

show abstract

“…A research collaboration between the ITER Organization, US DOE, UKAEA and EUROfusion has been formed to address the key open issues that remain for the ITER DMS. Specifically, these are [2]: These points are being addressed through modelling and SPI experiments on DIII-D, JET, KSTAR, J-TEXT and HL-2A, and with planned experiments on ASDEX Upgrade [3][4][5][6][7][8]. DIII-D and KSTAR have two toroidally separated injectors allowing focussed experiments on points (c) and (d).…”

Section: Introductionmentioning

confidence: 99%

Disruption thermal load mitigation with shattered pellet injection on the Joint European Torus (JET)

et al. 2021

View full text Add to dashboard Cite

Disruption mitigation remains a critical, unresolved challenge for ITER. To aid in addressing this challenge, a shattered pellet injection (SPI) system was installed on JET and experiments conducted at a range of thermal energy fractions and stored energies in excess of 7 MJ. The primary goals of these experiments were to investigate the efficacy of the SPI on JET and the ability of the plasma to assimilate multiple pellets. Single pellet injections produced a saturation in total radiated energy (W rad) with increasing injected neon content, suggesting total radiation of stored thermal energy. Further increases in injected neon quantities resulted in reduced cooling times and current quench (CQ) durations, indicating higher impurity assimilation. No significant variation in CQ duration or W rad was observed when varying the deuterium content at fixed neon quantities. Higher assimilation, inferred by shorter CQ durations, was measured when a mechanical punch was used to launch the pellets and this was attributed to a lower pellet velocity leading to higher solid content in the pellet plume and larger fragments penetrating deeper into the plasma. Radiation asymmetries averaged over the cooling time were inferred from Emis3D and ranged from 1.6 to 1.9. Asymmetries averaged over the entire disruption sequence were found to increase at higher thermal energy fractions. The radiated energy fractions decreased with increasing thermal energy fractions but this trend was eliminated when toroidal asymmetries were accounted for with Emis3D. Pure deuterium pellets were able to produce cooling times of up to 75 ms with a gradual loss in thermal stored energy of up to 80%. Experiments with multiple pellet injection indicated W rad can be increased through pellet superposition and density can be increased with an additional D2 injection without a reduction in W rad. KPRAD modelling accurately reproduced the cooling times and the CQ duration at high thermal energies. Assimilation estimates from KPRAD indicated CQ rates scale strongly whilst W rad scales weakly and saturates with assimilated neon content. Comparable W rad can be achieved with lower assimilated neon quantities as longer cooling times are attained. Thus reduced neon content can be preferential in a thermal load mitigation scheme as it may reduce radiation asymmetries and prevent flash melting.

show abstract

The Development of Shattered Pellet Injector on HL-2A

Cited by 15 publications

References 5 publications

Radiation asymmetry and MHD destabilization during the thermal quench after impurity shattered pellet injection

Radiation asymmetry and MHD destabilization during the thermal quench after impurity shattered pellet injection

Stability impacts from the current and pressure profile modifications within finite sized island

Disruption thermal load mitigation with shattered pellet injection on the Joint European Torus (JET)

Contact Info

Product

Resources

About