Supervisor: Ing. Ivan Ďuran, PhD

Database for comparison of plasma parameters of the JET

tokamak in various regimes of its operation

Martin Kubič

Czech Technical University, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech RepublicInstitute of Plasma Physics, v.v.i., Academy of Sciences of CR, Association EURATOM/IPP.CZ, Prague,

Czech Republic

Supervisor: Ing. Ivan Ďuran, PhD

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OutlineOutline JET tokamakJET tokamak

JET operating regimes – ELMing H-mode & AT regimeJET operating regimes – ELMing H-mode & AT regime

MDB DatabaseMDB Database

Plasma shapePlasma shape

Main resultsMain results

- Density and temperature profiles

- Radiated power fraction

- Thermocouples measurement

- Energy balance

- Impurities concentration & Carbon strength source Conclusions and future plantsConclusions and future plants

Czech Technical University, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech RepublicInstitute of Plasma Physics, v.v.i., Academy of Sciences of CR, Association EURATOM/IPP.CZ, Prague,

Czech Republic

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JET parameters

Joint European Torus (JET)Joint European Torus (JET)

Three world records:

22 MJ of fusion energy in one pulse 16 MW of peak fusion power a 65% ratio of fusion power produced to total input power

Czech Technical University, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech RepublicInstitute of Plasma Physics, v.v.i., Academy of Sciences of CR, Association EURATOM/IPP.CZ, Prague,

Czech Republic

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JET operating regimesJET operating regimesOne of the main aims of JET is to develop operating regimes for future International Thermonuclear Experimental Reactor (ITER). The reference confinement scenario of ITER is based on the H-mode which exhibits a transport barrier at the plasma edge. Additionally, advanced confinement modes with internal transport barriers (ITB) are considered for ITER steady state operating regime.

• L-mode: the gradients are limited over the whole plasma cross section• H-mode: large gradients at the edge (edge transport barrier), but a flat region in the plasma core. • Advanced regimes: ITB is present with or without edge transport barrier.

Transport barrier can be basically defined as a region of reduced radial transport of energy or particles and hence increased pressure gradient.

Czech Technical University, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech RepublicInstitute of Plasma Physics, v.v.i., Academy of Sciences of CR, Association EURATOM/IPP.CZ, Prague,

Czech Republic

S1S1

S2S2

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JET dataJET data• At JET, signals from all diagnostic systems are digitised and stored in a central database.

• In total, more than one billion readings of diagnostic data are recorded per JET pulse. In other words, every JET pulse produces almost 2 GBytes of raw diagnostics data, so that as much as 50 GBytes are stored daily.

• Most of the data need further processing - this is done automatically where possible by dedicated computer codes, but in many cases human intervention and/or data validation is required.• All data are accessible to all scientists on the JET site and, moreover, any scientist from any EFDA Association can work with the data from his home institute via the technique of Remote Access.

• MDB is a Matlab based software developed in CRPP-EPFL Lausane, Switzerland.• Its output is a table which contains physicals quantities e.g. plasma current, averaged over predefined time windows for a selected shot list. • The table itself is stored as MATLAB binary MAT-file.

Czech Technical University, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech RepublicInstitute of Plasma Physics, v.v.i., Academy of Sciences of CR, Association EURATOM/IPP.CZ, Prague,

Czech Republic

MDB DatabseMDB Databse

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In order to get clearer picture, I initially build a small database containing 66 JET shots.

S1 regime (23 discharges): 70236-70239, 70241-70243, 70245-70247, 70540-70542, 70544-70553. S1 shots were performed during two experimental sessions Divertor geometry studies - ITER like‘ The first are characterized by high plasma current of 2.5 MA. The latter session is characterized by low NBI and ICRH heating of total power ~9MW.

• S2 regime (10 discharges): 69987, 70274, 70275, 70292, 70300, 70333, 70355, 70358, 70361, 70362. These shots are characterized by no external seeding.

• S2 regime with Neon seeding (29 discharges): 69974, 69976-69982, 69984, 70276, 70281-70283, 70285-70287, 70289, 70291, 70301, 70334-70341, 70359, 70360. • S2 regime with Nitrogen seeding (4 discharges): 70293-70295, 70297These shots were performed during two experimental session S2 Impurity seeding in AT scenarios characterized by BT=3.1 T and Ip=2 MA.

DatabaseDatabase

Czech Technical University, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech RepublicInstitute of Plasma Physics, v.v.i., Academy of Sciences of CR, Association EURATOM/IPP.CZ, Prague,

Czech Republic

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• The figure shows the geometry (separatrix position) of both S1 (blue line) and S2 (red line) sets of discharges for times in the middle of the interval used for MDB database compilation. • As it can be seen the plasma in these S1 discharges is limited by poloidal midplane limiter and as a result, a rather thin scrape-off layer (SOL) can be expected.• These examples of EFIT reconstruction represent well the whole sets of S1 and S2 shots, which I considered here.

Plasma shapePlasma shape

Czech Technical University, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech RepublicInstitute of Plasma Physics, v.v.i., Academy of Sciences of CR, Association EURATOM/IPP.CZ, Prague,

Czech Republic

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Strike points location

The evaluation of outer strike points location is wrong, unlike of inner strike points. This is probably caused by error of magnetic reconstruction using XLOC procedure. (to be further investigated) All the S2 strike points locations are almost the same with inner strike points located in the upper part of inner top divertor tile.

Czech Technical University, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech RepublicInstitute of Plasma Physics, v.v.i., Academy of Sciences of CR, Association EURATOM/IPP.CZ, Prague,

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Impurities seeded dischargesImpurities seeded discharges Deuterium only discharges: gas seeding of

3.5 x 1021

electrons/s and feature higher frequency of ELMs

Impurity seeded discharges: Ne – 5x1020 – 2x1021 electrons/sN

2 - 5x1021 – 2x1022 electrons/s

Impurity and Deuterium discharges:Ne - 1x10

21 electrons/s

N2 - 1.5x1022 electrons/s

D2 – 1.5x10

22 electrons/s

N2: seeded into the divertor private region (GIM11)

Ne: seeded into divertor private region (GIM11)from top of the main chamber (GIM5)from the bottom of the main chamber (GIM9)

Czech Technical University, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech RepublicInstitute of Plasma Physics, v.v.i., Academy of Sciences of CR, Association EURATOM/IPP.CZ, Prague,

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Main resultsMain results

Czech Technical University, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech RepublicInstitute of Plasma Physics, v.v.i., Academy of Sciences of CR, Association EURATOM/IPP.CZ, Prague,

Czech Republic

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Density and temperature profilesDensity and temperature profiles

Density profiles for both S1(+) and S2(o,o,o) regimes. The S1 plasmas have almost twice higher density.

Apparently, more peaked temperature profiles are measured in S2 compared to S1, as expected.

S2 discharges have almost twice higher temperature

S1S2S2 NeS2 N

S1S2S2 NeS2 N

Czech Technical University, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech RepublicInstitute of Plasma Physics, v.v.i., Academy of Sciences of CR, Association EURATOM/IPP.CZ, Prague,

Czech Republic

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Central temperatureCentral temperature

The S1 discharges are composed from the two distinct groups: one with total input power of ~9MW and the second with total input power of ~16MW. Significantly higher central temperature on average is obtain in S2 regime reaching up to 8 keV (but at about half of S1 density) in comparison with approximately 4 keV for S1 regime. The gas seeding has no obvious effect on central electron temperature. The higher temperature in seeded discharges is supposed to be due to higher input power.

S1S2

S2 NeS2 N

Czech Technical University, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech RepublicInstitute of Plasma Physics, v.v.i., Academy of Sciences of CR, Association EURATOM/IPP.CZ, Prague,

Czech Republic

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S1S2S2 NeS2 N

Ion temperature profileIon temperature profile

Right figure: Central ion and electron temperature are roughly equal with Ti/Te being slightly higher in S2 discharges.

S1S2S2 NeS2 N

Czech Technical University, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech RepublicInstitute of Plasma Physics, v.v.i., Academy of Sciences of CR, Association EURATOM/IPP.CZ, Prague,

Czech Republic

Ion and electron temperature ratio

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#70293

Radiated power fractionRadiated power fraction Significantly less power is radiated in S2 without impurity seeding compared to S1. There is too narrow density range in S2 to asses density dependence of radiated power fraction. The radiated power fraction for seeded discharges is mostly about 60% reaching the S1 level. Hypothesis: The seeded discharges with lower radiated power fraction has lower input of intrinsic impurities. Confirmed for shot #70293. See next slide.

#70293S1S2S2 NeS2 N

Czech Technical University, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech RepublicInstitute of Plasma Physics, v.v.i., Academy of Sciences of CR, Association EURATOM/IPP.CZ, Prague,

Czech Republic

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Radiated power fraction vs. gas seeded amountRadiated power fraction vs. gas seeded amount

Left figure: The radiated power fraction as a function of neon fuelling amount remains constant of about 60%. The minimum neon fuelling amount for this value is ~ 4.1021 electrons.

Right figure: The situation is almost the same for nitrogen seeded discharges. The minimum nitrogen fuelling amount necessary for reaching 60% of radiated power fraction is ~ 7.1022 electrons.

The nitrogen fuelling amount needed is ~10x higher compared to neon.

S2S2 Ne

S2S2 N

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Divertor radiated powerDivertor radiated power

Left figure: The S2 plasmas (without seeding) radiate less than the colder edges in S1 plasmas. The two S1 ’clouds’ correspond to the two groups of discharges in database which differ in amount of additional heating power. For S1 shots, taking into account two distinct levels of input power, the divertor radiated power remains constant. Right figure: Lower ability to radiate out the energy from the divertor in S2 regime without impurity seeding is apparent also here. Nicely seen transition of S2 regime into „S1 like“ depending on amount of impurities injected (to be confirmed).

S1S2S2 NeS2 N

S1S2S2 NeS2 N

Czech Technical University, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech RepublicInstitute of Plasma Physics, v.v.i., Academy of Sciences of CR, Association EURATOM/IPP.CZ, Prague,

Czech Republic

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Czech Technical University, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech RepublicInstitute of Plasma Physics, v.v.i., Academy of Sciences of CR, Association EURATOM/IPP.CZ, Prague,

Czech Republic

ThermocouplesThermocouples measurement measurement

Layout of divertor tiles

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Energy balanceEnergy balance

The energy balance is not perfect for both regimes. The situation is the worst in S1. Slightly more energy arrives to divertor tiles in S1 than there seems to be available. There is discrepancy between input and radiated energy saved in ppf/dvtc and that obtained by integration of input and radiated power.

S1S2

S2 NeS2 N

Czech Technical University, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech RepublicInstitute of Plasma Physics, v.v.i., Academy of Sciences of CR, Association EURATOM/IPP.CZ, Prague,

Czech Republic

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Impurities concentration & Carbon source strengthImpurities concentration & Carbon source strength

Left The S2 plasmas produce more impurities due to its low densities and therefore hotter edges, i.e. higher plasma wall interaction and strain of plasma facing components. The Z

eff is of course higher for S2 discharges with gas seeding.

Right: The carbon production is much higher in the outer divertor and the outer and inner ratio range varies from 1 to 9. No particular difference between seeded/non-seeded shots is seen. No particular dependence of this ratio on density is observed.

S1S2S2 NeS2 N

S1S2S2 NeS2 N

Czech Technical University, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech RepublicInstitute of Plasma Physics, v.v.i., Academy of Sciences of CR, Association EURATOM/IPP.CZ, Prague,

Czech Republic

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Conclusions and future plantsConclusions and future plants Database containing more than 80 parameters for 66 JET discharges was built in order to compare S1 and S2 JET operation regimes.

From the global point of view plasma in S2 regimes is less dens, hotter, with more peaked electron temperature profile compared to S1 plasmas.

The gas seeding has no deteriorative effect on central electron temperature.

The radiated power fraction is significantly lower in S2 compared to S1 regime. Impurity seeding of S2 discharges leads to increase the radiated power fraction up to 70%.

Discrepancy in energy balance calculation has been found in S1 regime. More energy arrives to divertor tiles than there seems to be available.

The carbon source strength is about 3 times stronger in outer divertor compared to inner divertor.

Further extension of the database along the JET experimental campaigns. Include information on ELM type and frequency. Attempt to include more quantities characterizing the edge plasma.

Czech Technical University, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech RepublicInstitute of Plasma Physics, v.v.i., Academy of Sciences of CR, Association EURATOM/IPP.CZ, Prague,

Czech Republic

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Czech Technical University, Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech RepublicInstitute of Plasma Physics, v.v.i., Academy of Sciences of CR, Association EURATOM/IPP.CZ, Prague,

Czech Republic

Thank you

For your

Attention