Supervisor: Ing. Ivan Ďuran, PhD

1. Czech Technical University,Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic Institute of Plasma Physics, v.v.i., Academy of Sciences of CR, Association EURATOM/IPP.CZ, Prague, Czech Republic Database for comparison of plasma parameters of the JET tokamak in various regimes of its operation Martin Kubič Supervisor: Ing. Ivan Ďuran, PhD

2. Czech Technical University,Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic Institute of Plasma Physics, v.v.i., Academy of Sciences of CR, Association EURATOM/IPP.CZ, Prague, Czech Republic • Outline • JET tokamak • JET operating regimes – ELMing H-mode & AT regime • MDB Database • Plasma shape • Main results • -Density and temperature profiles • - Radiated power fraction • - Thermocouples measurement • - Energy balance • - Impurities concentration & Carbon strength source • Conclusions and future plants

3. Czech Technical University,Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic Institute of Plasma Physics, v.v.i., Academy of Sciences of CR, Association EURATOM/IPP.CZ, Prague, Czech Republic Joint European Torus (JET) JET parameters 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

4. Czech Technical University,Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic Institute of Plasma Physics, v.v.i., Academy of Sciences of CR, Association EURATOM/IPP.CZ, Prague, Czech Republic JET operating regimes One 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. S1 S2

5. Czech Technical University,Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic Institute of Plasma Physics, v.v.i., Academy of Sciences of CR, Association EURATOM/IPP.CZ, Prague, Czech Republic JET 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 Databse • 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.

6. Czech Technical University,Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic Institute of Plasma Physics, v.v.i., Academy of Sciences of CR, Association EURATOM/IPP.CZ, Prague, Czech Republic Database 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, 70297 These shots were performed during two experimental session S2 Impurity seeding in AT scenarios characterized by BT=3.1 T and Ip=2 MA.

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

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

9. Czech Technical University,Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic Institute of Plasma Physics, v.v.i., Academy of Sciences of CR, Association EURATOM/IPP.CZ, Prague, Czech Republic Impurities 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/sN2 - 5x1021 – 2x1022 electrons/s • Impurity and Deuterium discharges:Ne - 1x1021 electrons/sN2 - 1.5x1022 electrons/sD2 – 1.5x1022 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)

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

11. Czech Technical University,Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic Institute of Plasma Physics, v.v.i., Academy of Sciences of CR, Association EURATOM/IPP.CZ, Prague, Czech Republic S1 S2 S2 Ne S2 N S1 S2 S2 Ne S2 N Density and temperature profiles • Apparently, more peaked temperature profiles are measured in S2 compared to S1, as expected. • S2 discharges have almost twice higher temperature • Density profiles for both S1(+) and S2(o,o,o) regimes. The S1 plasmas have almost twice higher density.

12. Czech Technical University,Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic Institute of Plasma Physics, v.v.i., Academy of Sciences of CR, Association EURATOM/IPP.CZ, Prague, Czech Republic S1 S2 S2 Ne S2 N Central 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.

13. Czech Technical University,Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic Institute of Plasma Physics, v.v.i., Academy of Sciences of CR, Association EURATOM/IPP.CZ, Prague, Czech Republic S1 S2 S2 Ne S2 N S1 S2 S2 Ne S2 N Ion temperature profile Ion and electron temperature ratio • Right figure: Central ion and electron temperature are roughly equal with Ti/Te being slightly higher in S2 discharges.

14. Czech Technical University,Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic Institute of Plasma Physics, v.v.i., Academy of Sciences of CR, Association EURATOM/IPP.CZ, Prague, Czech Republic Radiated 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. S1 S2 S2 Ne S2 N #70293 #70293

15. Czech Technical University,Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic Institute of Plasma Physics, v.v.i., Academy of Sciences of CR, Association EURATOM/IPP.CZ, Prague, Czech Republic Radiated power fraction vs. gas seeded amount S2 S2 Ne S2 S2 N • 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.

16. Czech Technical University,Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic Institute of Plasma Physics, v.v.i., Academy of Sciences of CR, Association EURATOM/IPP.CZ, Prague, Czech Republic Divertor radiated power S1 S2 S2 Ne S2 N S1 S2 S2 Ne S2 N • 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).

17. Czech Technical University,Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic Institute of Plasma Physics, v.v.i., Academy of Sciences of CR, Association EURATOM/IPP.CZ, Prague, Czech Republic Thermocouplesmeasurement Layout of divertor tiles

18. Czech Technical University,Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic Institute of Plasma Physics, v.v.i., Academy of Sciences of CR, Association EURATOM/IPP.CZ, Prague, Czech Republic Energy balance S1 S2 S2 Ne S2 N • 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.

19. Czech Technical University,Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic Institute of Plasma Physics, v.v.i., Academy of Sciences of CR, Association EURATOM/IPP.CZ, Prague, Czech Republic Impurities concentration & Carbon source strength S1 S2 S2 Ne S2 N S1 S2 S2 Ne S2 N • 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 Zeff 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.

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

21. Czech Technical University,Faculty of Nuclear Sciences and Physical Engineering, Prague, Czech Republic Institute of Plasma Physics, v.v.i., Academy of Sciences of CR, Association EURATOM/IPP.CZ, Prague, Czech Republic Thank you For your Attention