Spectroscopic camera analysis of the roles of molecularly assisted reaction chains during detachment in JET L-mode plasmas

Karhunen, J.; Holm, A.; Aleiferis, S.; Carvalho, P.; Groth, M.; Lawson, K.; Lomanowski, B.; Meigs, A.; Shaw, A.; Solokha, V.

doi:10.1016/j.nme.2022.101314

Cited by 7 publications

(18 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This shows that, throughout the entire discharge, MAD is the dominant neutral atom generation process. This is in agreement with previous findings on TCV [24], JET [46] as well as SOLPS-ITER modelling with modified rates for TCV [28].…”

Section: Hydrogenic Power Losses In the Super-x Divertor And Molecula...supporting

confidence: 93%

The role of plasma–atom and molecule interactions on power & particle balance during detachment on the MAST Upgrade Super-X divertor

Verhaegh,

Lipschultz,

Harrison

et al. 2023

Nucl. Fusion

View full text Add to dashboard Cite

This paper shows first quantitative analysis of the detachment processes in the MAST Upgrade Super-X divertor (SXD). We identify an unprecedented impact of plasma-molecular interactions involving molecular ions (likely $D_2^+$), resulting in strong ion sinks (Molecular Activated Recombination - MAR), leading to a reduction of ion target flux. The MAR ion sinks exceed the divertor ion sources before electron-ion recombination (EIR) starts to occur, suggesting that significant ionisation occurs outside of the divertor chamber. In the EIR region, $T_e \ll 0.2$ eV is observed and MAR remains significant in these deep detached phases. The total ion sink strength demonstrates the capability for particle ion exhaust in the Super-X Configuration. Molecular Activated Dissociation (MAD) is the dominant volumetric neutral atom creation process can lead to an electron cooling of 20\% of $P_{SOL}$. The measured total radiative power losses \emph{in the divertor chamber} are consistent with inferred hydrogenic radiative power losses. This suggests that intrinsic divertor impurity radiation, despite the carbon walls, is minor in the divertor chamber. This contrasts previous TCV results, which may be associated with enhanced plasma-neutral interactions and reduced chemical erosion in the detached, tightly baffled SXD. The above observations have also been observed in higher heat flux (narrower SOL width) type I ELMy H-mode discharges. This provides evidence that the characterisation in this paper may be general.

show abstract

Section: Hydrogenic Power Losses In the Super-x Divertor And Molecula...supporting

confidence: 93%

The role of plasma–atom and molecule interactions on power & particle balance during detachment on the MAST Upgrade Super-X divertor

Verhaegh,

Lipschultz,

Harrison

et al. 2023

Nucl. Fusion

View full text Add to dashboard Cite

show abstract

“…MAR & MAD not only have an impact on the divertor physics, but also result in a significant content of excited hydrogen atoms and thus hydrogen Balmer line emission as was shown in literature [48,14,13,12,5,7,6,11] and is indicated by the increase in Dα emission during detachment as shown in figure 3. Since that strong increase in Dα emission is not captured by the 'default' setup, this causes strong concerns on the synthetic deuterium (and tritium) atomic emission diagnostic signals predicted from plasma-edge modelling.…”

Section: Impact On Diagnostic Design Analysis and Real-time Detachmen...mentioning

confidence: 69%

“…Answering that question requires further investigation, including further studies on the applicable molecular charge exchange as well as applying those to a range of reactor conditions, which is outside the scope of this work. Although there are large uncertainties regarding the molecular charge exchange rates, the molecular vibrational distribution (that determines these effective rates to a large extent) and their applicability to reactors, signatures of the impact of molecular ions on the hydrogen emission are being observed in JET with the ITER-like wall [12,13,14] during deep detachment.…”

Section: Could Molecular Ions Play a Role In Reactors During Detachment?mentioning

confidence: 99%

“…Plasma-molecular effects result in a significantly enhanced population of the hydrogen atom n = 3 state, which may have implications for the treatment of photon opacity to the Lyman series in simulations [51,52] as well as the diagnosis of photon opacity [7]. Accounting for molecular ions in the analysis of hydrogen atomic line emission required the creation of novel analysis techniques [14,13,6], which need to be further expanded to include photon opacity effects.…”

Section: Impact On Diagnostic Design Analysis and Real-time Detachmen...mentioning

confidence: 99%

“…Recent experimental investigations have used spectroscopy and filtered camera imaging on TCV [2,3,4,5,6,7,8,9,10], MAST-Upgrade [11] and JET [12,13,14] that register significant Balmer line emission after the break-up of molecular ions. For TCV [6,7], it was shown that MAR from molecular ions is a dominant contributor to the reduction of the ion target flux in contradiction with SOLPS-ITER simulations [6,15] that did not show a roll-over of the ion target flux [15,16,17,18].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Investigating the impact of the molecular charge-exchange rate on detached SOLPS-ITER simulations

Verhaegh¹,

Williams²,

Moulton³

et al. 2023

Preprint

View full text Add to dashboard Cite

show abstract

Transition from MAR to EIR of deuterium plasma detachment in NAGDIS-II

Shi,

Kaizawa,

Tanaka

et al. 2023

Phys. Scr.

View full text Add to dashboard Cite

Volumetric plasma recombination in a detached deuterium (D) plasma was experimentally studied in the linear plasma device NAGDIS-II. The radial distributions of the electron temperature (T e ) and the electron density (n e ) were measured by upstream and downstream laser Thomson scattering (LTS) systems and D-atom excited states of the Balmer series (n = 3–7) were measured by optical emission spectroscopy (OES). The results indicated that the electron static pressure, particle flux and heat flux present a two-step reduction with an increasing neutral pressure, suggesting that molecule activated recombination (MAR) and electron–ion recombination (EIR) were activated, respectively. The difference in the distributions of the atomic state population densities was observed to be a feature of the transition from the MAR-dominant phase to the EIR-dominant phase. The transition between the two phases had a distinct boundary at T e ∼0.7 eV, which was considered a transition point between the phases. The ratios of the atomic state population densities showed different features in the two phases, and are expected to be useful in characterizing the phase and degree of plasma detachment.

show abstract

Spectroscopic camera analysis of the roles of molecularly assisted reaction chains during detachment in JET L-mode plasmas

Cited by 7 publications

References 27 publications

The role of plasma–atom and molecule interactions on power & particle balance during detachment on the MAST Upgrade Super-X divertor

The role of plasma–atom and molecule interactions on power & particle balance during detachment on the MAST Upgrade Super-X divertor

Investigating the impact of the molecular charge-exchange rate on detached SOLPS-ITER simulations

Transition from MAR to EIR of deuterium plasma detachment in NAGDIS-II

Contact Info

Product

Resources

About