Disruptions and run-aways E. Joffrin With thanks to P. Lomas

E. Joffrin| GPM 2015| Lausanne | rd January| Page 2 Outline 1.Key deliverable for Some pictures … of disruptions/run-aways with the ILW 3.Key issues on disruptions/run-aways from C33 campaigns 4.Proposed experiments and tasks for Summary & discussion

E. Joffrin| GPM 2015| Lausanne | rd January| Page 3 “Quantify disruption mitigation efficiency in high energy plasmas and extrapolate to ITER” JET key deliverable & context A memorandum (by E. Joffrin & P. Martin) on a common strategy for the study of disruptions and run-away in EUROfusion has been circulated last october For JET, disruption is an integrated part of development to high Ip and Wth (see next slides) For ITER, disruption is the top identified risk for its future operation (mitigation essential above 8MA)

E. Joffrin| GPM 2015| Lausanne | rd January| Page 4 Upper dump plates Inner guard limiter Place where large disruptions (red) & run-away (yellow) damages have been observed

E. Joffrin| GPM 2015| Lausanne | rd January| Page 5 Bubble-like damage to the upper dump and IGWL place from run-aways toroidally asymmetric Outer ends beryllium UDP protection tiles all damaged in a similar way toroidally spray of droplets stuck on wall JET –ILW has already undergone severe damage to the Be component by disruptions and run-aways See also Reux IAEA 2014

E. Joffrin| GPM 2015| Lausanne | rd January| Page 6 Run-away impact seen on the upper dump plates by the wide angle IR camera during the experiments Footprint on upper dump-plate:  Localized hots spots on dump plate ribs  Toroidally and poloidally localized Consistent with upwards movement of plasma centroid

Name of presenter | Conference | Venue | Date | Page 7 IWGL 7X 2014 IWGL 7X 2012 Unchanged except run has disappeared New runaway damage Run-away and heat load impact: 2012 vs 2014

E. Joffrin| GPM 2015| Lausanne | rd January| Page Be Upper dump plates 2014 Be Upper dump plates New, runaway! Run-aways produces bubble-like damage to the Be limiters

E. Joffrin| GPM 2015| Lausanne | rd January| Page 9 Diagnostic:  Bolometry camera (KB5V (octant 3) and KB5H (octant 6)) close to DMV2 and DMV3.  Old bolometry camera (KB1) diagnostics in Octant 2/3/6/7: radiation asymmetries.  Fast camera installed in oct 8 has a direct line of sight to the DMV1 gas entry tube. (2008) Octant 1(2013) Octant 3(2015) Octant 5  DMV1 installed 4.6m away from the plasma separatrix. Not DT compatible.  DMV2/DMV3 installed 3.0 and 2.4m respectively away from separatrix. DT compatible JET hardware for 2015 – 2016 campaigns

H1.3: Quantify disruption mitigation efficiency in high energy plasmas and extrapolate to ITER Disruption mitigation at high energy content.  use of the 3 DMVs)  Modelling included (4) <2.5MA Higher current included in the baseline and hybrids to high current (for Ip>2.5MA) Radiation asymmetry of mitigated and unmitigated disruptions (2) TOTAL: 9 sessions + task: disruption prediction and avoidance schemes. + task: modelling of halo current + task: modelling runaway electrons stability Mitigation of run-away with high Z-material (3) Initially: 19 proposals and 29 sessions requested.

E. Joffrin| GPM 2015| Lausanne | rd January| Page 11 Can the TQ mitigation efficiency of 90% be confirmed at high thermal energy (high current)? JET observes a decreasing radiation efficiency with increasing thermal enrgy Also: decrease of radiation efficiency, is not changed by increasing the argon fraction >10% in the DMV. (Reux, IAEA 2014). EM load depends on the Current quench CQ rate: -Long CQ  high halo current -Short CQ  high eddy currents  How should we tailor the current quench time to get the smallest forces with acceptable heat load mitigation?  What is the best DMV arrangements for recovering 90% TQ mitigation efficiency?  Modelling and extrapolation for ITER of mitigation efficiency

Dependence of disruption radiation asymetries still not fully understood E. Joffrin| GPM 2015| Lausanne | rd January| Page 12 Toroidal pre-TQ asymetries can be controlled by multiple toroidal injection location Radiation peaking during the TQ is determined by the phase shift between the n=1 mode and the injection point both in JET and DIII-D.  Are there any other parameters that could explain radiation asymetries:  gas species?  q profiles (q>1 or <1) ?  Degraded plasma conditions (MHD, HL, …)  Magnetic asymetries (halo/eddy current) modelling

E. Joffrin| GPM 2015| Lausanne | rd January| Page 13 Objectives  Establish the optimal parameter and configuration of the set of toroidally spaced MGIs for minimizing the current quench time to get the smallest EM forces and heat loads in JET scenarios up to 2.5MA (note only 2 MGIs can be used for DT phase).  Produce a scaling of the forces for mitigated disruptions with Ip and total energy content.  Validate the JOREK and simplified model prediction on the current scan and extrapolate to JET-DT scenarios and ITER.  In the condition of the experiment, monitor systematically if run-away are generated. Relation with other experiment  This experiment has the objective to provide the optimised settings and DMV arrangements for minimising EM forces in the baseline scenario for Ip<2.5MA.  It will also bring information on radiation asymmetry  Monitor/detect systematically the presence of run-away and document the “run-away domain” Collaboration with MST1: Collaboration with MST1: close collaboration in particular on modelling of the MGI Number of sessions: 4 Disruption mitigation at high energy content

E. Joffrin| GPM 2015| Lausanne | rd January| Page 14 Objectives  Develop and compare off-line automated disruption identification and causes with real time capabilities.  Identify real time requirements and test on both JET and AUG database of disruptions.  Produce physics based (for instance locked mode) predictors using adequate signals and integrate into predictors.  Propose and test off-line a set of machine-independent quantities suitable as disruption identifiers and test on JET/AUG.  Establish a relation matrix between the alarms and the plasma response (scenario dependent) in coordination with the operation (SLs) group. Relation with other experiment/task  This task is the continuation of a task in C33-C34 with different objectives.  In , this task must be closely connected with the scenarios operation and focus on the plasma response to give for a given alarm. Collaboration with MST1: (very!) close collaboration. The efforts on disruption prevention and avoidance schemes have to be coordinated on EUROfusion devices by JET1 and MST1 TFLs. Disruption prevention and avoidance schemes for JET (task).

E. Joffrin| GPM 2015| Lausanne | rd January| Page 15 Objectives  Characterize the poloidal and toroidal radiation and heat load asymmetries in mitigated and unmitigated disruption.  Examine the asymmetry dependence with q profiles and/or different gas species  Determine mitigation efficiency and timescales in 'realistic' mitigation scenarios with unhealthy target plasmas (such as plasma with radiation pealing or MHD activity) Number of sessions: 2 Radiation asymmetry of mitigated and unmitigated disruptions Collaboration with MST1: Collaboration with MST1: Different measurements are present in JET and AUG would benefit from each other for the understanding of radiation asymmetries.

E. Joffrin| GPM 2015| Lausanne | rd January| Page 16 Objectives  Model the role of hiro and halo current and current asymmetry in unmitigated disruption for JET with M3D.  Validate/apply modelling to cases with EFCCs (JET 2009) and determine if halo can be controlled or by applying vertical fields Relation with other experiment/task  This task is a modelling task using existing codes and past data  The modelling may motivate and justify an experiment in JET, TCV or AUG. Collaboration with MST1: Collaboration with MST1: close collaboration on the modelling effort and validation of the models with data from different devices. Modelling of halo current (task)

E. Joffrin| GPM 2015| Lausanne | rd January| Page 17 Run-away domain has been identified in JET.  Test the impact of the plasma magnetic topology on the run-away generation (modelling)  Compute the orbits of runaway electrons in the 3D electromagnetic field.  Test the importance of the de-confinement of runaway electrons by MHD turbulence Runaway domain entry points in JET-C and JET-ILW: (f Ar = 40%, B t =3T)

E. Joffrin| GPM 2015| Lausanne | rd January| Page 18  This is unlikely to be achieved by “deconfinement” using a magnetic perturbation Present strategy to ensure dissipation: aim for a sufficient high density of high-Z from the beginning of the CQ or after a fixed delay (thus increasing Ec)  Late injection into an existing runaway beam has shown negligible effects on runaway current, the HXR emission. DMV2 DMV1 ITER require to dissipate most of the runaway energy within a timescale of ~100ms  There are evidence in JET that with pre-CQ no RAs are generated (Reux IAEA 2014)  Increase in gas density is predicted to increase dissipation  Optimum flow rate in early CQ injection  Develop magnetic in advance modelling for RA control and kinetic modelling

E. Joffrin| GPM 2015| Lausanne | rd January| Page 19 Objectives  Determine the efficiency of high Z impurity injection in a RA beam by changing the DMV flow rate, the DMV location and the time of injection wrt the CQ.  Modelling of results with kinetic modelling and fast equilibrium and produce an extrapolation to ITER. Collaboration with MST1: close collaboration on the mitigation methods with high Z impurity and modelling Number of sessions: 2 Mitigation of run-away with high Z material

E. Joffrin| GPM 2015| Lausanne | rd January| Page 20 Objectives  Test the importance of de-confinement of runaway electrons by magnetic perturbation and machine size effect in using the modelling of a test particle (JOREK).  Establish the basis for an experiment in a tokamak (JET or TCV) aiming at controlling the RA beam and testing the effect of applied vertical field or external magnetic perturbation. Relation with other experiment  This modelling Task should establish the experimental basis (or not) for the control of run-aways by magnetic perturbation for JET1 and/or MST1. Collaboration with MST1: Collaboration with MST1: Modelling that could apply to both JET and AUG Modelling of run-away electrons as a test particle (Task)

E. Joffrin| GPM 2015| Lausanne | rd January| Page 21 TitleSessions(proposals)HeadlinesITPA Exp.Disruption mitigation at high energy content 4 (3)D11, D06MDC-1 TaskDisruption prevention and avoidance schemes for JET - (5)D09MDC-17 MDC-22 Exp.Radiation asymmetry of mitigated and unmitigated disruptions 2 (3)D11MDC-1 TaskModelling of halo current- (2)D10MDC-1 Exp.Mitigation of run-away with high Z material 3 (3)D07MDC-16 TaskModelling of runaway electrons as test particles - (1)D07MDC-16 Summary of the envisaged experiments/tasks in the main programme Initially: 19 proposals and 29 sessions requested.

E. Joffrin| GPM 2015| Lausanne | rd January| Page 22 Proposals not considered in the Programme 1- Dependencies of run-away generation with the magnetic topology This proposed experiment is better suited in a tokamak like TCV. It is proposed to do it under MST1 (submitted to MST1) 2- ITPA joint experiment to study threshold conditions for runaway electron generation and suppression This proposal aims at using current plateau-born run-away and not disruptions run-away. These are not considered as relevant for run-away physics. Many devices have already contributed to the ITPA JE. 3- Disruption in Helium plasma No He campaign

E. Joffrin| GPM 2015| Lausanne | rd January| Page 23 Part II: JET1 – MST1 collaboration/joint work

E. Joffrin| GPM 2015| Lausanne | rd January| Page 24 TitleMST1 Exp.Disruption mitigation at high energy content Disruption mitigation with MGI (D3) Model mitigated disruptions with JOREK (D14) TaskDisruption prevention and avoidance schemes for JET Cross-machine analysis for JET & AUG disruption (D2). Cross disruption predictor AUG/JET (D4) Development of a disruption precursor based on rotating MHD instabilities (D12) Physics based real time identification of disruption (D18) Exp.Radiation asymmetry of mitigated and unmitigated disruptions Assessment of thermal load mitigation during MGI (D16) TaskModelling of halo current? Exp.Mitigation of run-away with high Z material Runaway electron generation and dissipation (D3) Effect of MGI asymmetry on generation and suppression of run-aways (D11) TaskModelling of runaway electrons as test particles Run-away electrons and disruption physics (D10) Model run-away electrons as a test particles in JOREK (D14) Synergies between the JET proposed experiments and MST1 proposals (12 proposals) on H1.3

E. Joffrin| GPM 2015| Lausanne | rd January| Page 25 Separate proposals in the MST1 list (8 proposals) 1.Model based plasma supervision and disruption avaidance (D5) 2.Disruption control in high bN and high density scenarios with ECCD/ECRH (D6) 3.Control of the locking position of locked modes near disruptions (D7) 4.Application of disruption avoidance techniques (ECCD/ECRH) in accessible scenarios (D8) 5.Determination and correction of the static intrinsic error field (D9) 6.2/1 NTM wall locking avaoidance by forced rotation through external magnetic perturbations (D13) 7.Effect of plasma shaping on run-away electrons (D15) (from JET!) 8.Decorrelation of run-away electrons by magnetic perturbations and role of 3D plasma response (D17) 9.Runaway electron position control and current ramp-down (D19) 10.En experimental investigation of the VDE dependence on plasma elongation and internal inductance in the TCV tokamak (D20) 11.Detection avoidance and mitigation of disruptions (D21) Specific proposals to the MST1 task Force  Note that they are also 2 EnR projects launched on this topics in 2015: IPP05 (JOREK modelling) & CEA09 (run-away modelling)

E. Joffrin| GPM 2015| Lausanne | rd January| Page 26 For discussion A close collaboration activity is foreseen (and necessary!) with MST1 on the topic of disruption and run-aways. AUG is equipped with similar tools than JET.  TLFs (MST1 & JET1) to seat together and define the common denominator and specificities in terms of experiments/tasks and deliverables.  In case of joint experiments, 2 scientific coordinator JET1/MST1 will be selected.  TFLs to contact PI of the 2 EnR projects to coordinate the efforts on modelling  TFLs to organise joint TF-meeting and science meeting on these subjects when necessary.  Database  (…) Any other ideas?

E. Joffrin| GPM 2015| Lausanne | rd January| Page 27 Headline 1.3: Avoidance and mitigation of disruption and runaways electrons H1.3-D01: Develop robust operation of ITER scenarios and their safe termination H1.3-D06: Document conditions for run-away electron generation and mitigation H1.3-D07: Test control of runaway electrons by alternative methods (non-axisymmetric fields) H1.3-D09: Develop disruption prediction methods that minimise the requirements for model training on ITER and real-time predictors methods optimised in term of model training, success rate, anticipation time, differentiation among different types of disruptions. H1.3-D10: Develop full 3D codes (plasma + vessel) to describe halo current formation and asymmetries. H1.3-D11: Qualification of Massive Gas Injection as a mitigation method for heat loads and forces (fuelling efficiency, local peaking of radiation load as function of MGI parameters and plasma conditions) H1.3-D12: Develop Disruption workflow – including ELM module/RMP. Headlines Key deliverable: quantify disruption mitigation efficiency in high energy plasmas and extrapolate to ITER