Introduction to the disruption JET/MST program E. Joffrin &
P. Martin Presented by P. Martin
Slide 2
Consequences of disruptions Heat loads When thermal energy is
lost from the plasma (thermal quench) and during the current quench
phase, as the magnetic energy is converted to heat energy
Electromagnetic loads (induced and halo currents) Current will take
the path of least resistance when plasma intercept material surface
during VDE Runaway electrons Piero Martin | GPM 2015 | Lausanne |
21.01.15 | Page 2 JET
Slide 3
Disruption are a very serious issue Max electromagnetic forces
expected in ITER order of tens of MN For comparison a couple of
weight forces: o AIRBUS 380 5.5 MN o Medium size ship 50 MN Piero
Martin | GPM 2015 | Lausanne | 21.01.15 | Page 3
Slide 4
Disruption are a very serious issue In ITER disruption local
thermal loads in the worst cases significantly exceed (~10 times)
melting threshold of divertor targets and FW panels Piero Martin |
GPM 2015 | Lausanne | 21.01.15 | Page 4
Slide 5
Disruptions and runaways high priority for ITER Piero Martin |
GPM 2015 | Lausanne | 21.01.15 | Page 5
Slide 6
Piero Martin | GPM 2015 | Lausanne | 21.01.15 | Page 6
Disruption category in ITER
Slide 7
M. Lehnen, 17 th meeting of the ITPA-CC, December 2014 2014,
ITER Organization Page 7 IDM UID: Q8TSWP When do we need the DMS?
Lehnen et al., doi:10.1016/j.jnucmat.2014.10.075 Required from
early operation on (heat loads) High current operation requires
high mitigation success rate (EM loads) High efficiency needed at
high energies Runaway generation during non-active phase not
expected for unmitigated disruptions (no impurity influx)
Slide 8
Actions against disruptions Avoidance Drive safely.. Piero
Martin | GPM 2015 | Lausanne | 21.01.15 | Page 8
Slide 9
Actions against disruptions Avoidance Drive safely For fusion
not.. always an option Piero Martin | GPM 2015 | Lausanne |
21.01.15 | Page 9 N =1 2/1 NTMs Tearing Snakes Fishbones Sawteeth
NN q min 1 2 3 0 no wall limit with wall limit Hybrid scenarios
Advanced scenarios Baseline scenarios
Slide 10
Actions against disruptions Avoidance Drive safely or.. Active
control Piero Martin | GPM 2015 | Lausanne | 21.01.15 | Page
10
Slide 11
Actions against disruptions Avoidance Prediction Piero Martin |
GPM 2015 | Lausanne | 21.01.15 | Page 11
Slide 12
Actions against disruptions Avoidance Prediction Mitigation
Thanks to F. Felici for the car analogy Piero Martin | GPM 2015 |
Lausanne | 21.01.15 | Page 12
Slide 13
Disruption avoidance Stabilization of MHD modes through EC
localized injection on resonant surface To be combined with
termination strategy Esposito, Maraschek, MST review meeting (2014)
Piero Martin | GPM 2015 | Lausanne | 21.01.15 | Page 13
Single signal: JET Locked mode amplitude Locked mode amplitude
normalized to the total current Product of the two top and lower
flux measurement Product of the two top and lower flux measurement
normalized by the total current squared. Vertical stabilization
amplifier trip signal Current derivative. AUG Locked mode amplitude
Piero Martin| 2015 GPM | Lausanne | 21.01.15 | Page 15
Slide 16
Predictions Statistical tools Neural networks APODIS (classify
whether a pulse state is disruptive or non- disruptive and does
this through the entire duration of the pulse) Need training!
Physics based model needed Piero Martin| 2015 GPM | Lausanne |
21.01.15 | Page 16
Slide 17
Mitigation: Massive Gas Injection Injecting large amount of
noble gas at high pressure using fast opening valves. Can
potentially mitigate: o Heat loads o Electromagnetic loads o
Runaways electrons Name of presenter | Conference | Venue | Date |
Page 17 Hender, Active Control of MHD instabilities in Hot Plasmas,
Springer (2015) AUG
Slide 18
Massive Gas Injection Reduction of heat loads by increasing
radiated power fraction Issue of radiation asymmetry: need for
careful measurements to assess efficiency Olynek et al., Workshop
on Theory and Simulation of Disruptions PPPL (2013) C-mod Piero
Martin | GPM 2015 | Lausanne | 21.01.15 | Page 18
Slide 19
Massive Gas Injection Reduction of e.m. loads by reducing halo
currents, since current decay is quicker But, if too rapid, eddy
currents to high! Lehnen, MST GPM 2013 Piero Martin | GPM 2015 |
Lausanne | 21.01.15 | Page 19
Slide 20
Massive Gas Injection Reduction of heat loads by increasing
radiated power fraction Reduction of e.m. loads by reducing halo
currents, since current decay is quicker Effect on runaway under
investigation Pautasso, Papp MST review (2014) AUG Piero Martin |
GPM 2015 | Lausanne | 21.01.15 | Page 20
Slide 21
JET does not see RE mitigation with MGI Piero Martin| 2015 GPM
| Lausanne | 21.01.15 | Page 21 JET: no effect on current*, density
and HXR (injection location far from RE beam) *delayed decay in
current also without 2 nd injection C. Reux, IAEA 2014
Slide 22
MGI and RE generation Reux, 21 th PSI Conf., 2014 JET Piero
Martin | GPM 2015 | Lausanne | 21.01.15 | Page 22
Slide 23
MGI efficiency in ill plasmas Piero Martin| 2015 GPM | Lausanne
| 21.01.15 | Page 23 Pre-existing tearing modes decrease pre-TQ
duration This reduces fuelling and mitigation efficiency Pautasso,
EPS 2013 AUG
Slide 24
MDC-1 (ITPA joint experiment on MGI) Open questions 1.Test
feasibility and efficiency of MGI during current quench 2.Asses
injection location with respect to TQ radiation efficiency 3.Can TQ
radiation 90% radiation efficiency be confirmed? 4.Injection into
disruptive plasmas 5.Assess critical impurity density for RE
suppression Piero Martin| 2015 GPM | Lausanne | 21.01.15 | Page
24
Slide 25
Runaway losses and magnetic stochasticity Name of presenter |
Conference | Venue | Date | Page 25 Izzo IAEA FEC 2010 Nimrod
Slide 26
Runaway losses and magnetic stochasticity Enhanced losses with
externally applied magnetic perturbation Piero Martin| 2015 GPM |
Lausanne | 21.01.15 | Page 26 DIII-D TEXTOR RFX tok ITER Papp PPCF
2012 Lehnen PRL 2008 Hollmann PoP 2010 Gobbin ITPA 2014
Slide 27
MGI system in JET In 2015 3 disruptions mitigation valves o
DMV1 installed in 2008 upper vertical port of Octant 1 o DMV2
installed in 2013 horizontal port of octant 3 o DMV3 to be
installed in 2015 upper vertical port of octant 5 DMV1:4.6m away
from plasma separatrix not DT compatible. DMV2 & DMV3: 3.0 and
2.4m from plasma separatrix DT compatible Name of presenter |
Conference | Venue | Date | Page 27
Slide 28
JET disruption diagnostics Vertical and horizontal bolometry
camera (KB5V (octant 3) and KB5H (octant 6)) are located next to
DMV2 and DMV3 respectively. Old bolometry camera (KB1) diagnostics
located vertically in Octant 2, 3, 6 and 7 useful to characterize
radiation asymmetries. Available for operations in 2015. Fast
camera installed in oct 8 has a direct line of sight to the DMV1
gas entry tube can provide relatively localized information on the
DMV2 behavior although not directly in the line of sight. Piero
Martin| 2015 GPM | Lausanne | 21.01.15 | Page 28
Slide 29
MGI system in AUG Piero Martin | GPM 2015 | Lausanne | 21.01.15
| Page 29
Slide 30
AUG disruption diagnostic and mitigation systems Piero Martin|
2015 GPM | Lausanne | 21.01.15 | Page 30
Slide 31
TCV disruption diagnostic and mitigation systems Fast
mitigation valve available Diagnostics a complete set of fast
poloidal and toroidal magnetic probe arrays One infrared camera
with one or two more to be added shortly (MST2 project), which
could be used for runaway electron detection. a hard X-ray
tomographic spectrometer composed of 3 (soon to be 4) 24-detector
cameras with 7 keV resolution in the 10-300 keV range a runaway
(gamma-ray) detector a fast visible camera Piero Martin| 2015 GPM |
Lausanne | 21.01.15 | Page 31
