Minority and mode conversion heating in (3He)-H JET plasma

Radio frequency (RF) heating experiments have recently been conducted in JET (He-3)-H plasmas. This type of plasmas will be used in ITER's non-activated operation phase. Whereas a companion paper in this same PPCF issue will discuss the RF heating scenario's at half the nominal magnetic field, this paper documents the heating performance in (He-3)-H plasmas at full field, with fundamental cyclotron heating of He-3 as the only possible ion heating scheme in view of the foreseen ITER antenna frequency bandwidth. Dominant electron heating with global heating efficiencies between 30% and 70% depending on the He-3 concentration were observed and mode conversion (MC) heating proved to be as efficient as He-3 minority heating. The unwanted presence of both He-4 and D in the discharges gave rise to 2 MC layers rather than a single one. This together with the fact that the location of the high-field side fast wave (FW) cutoff is a sensitive function of the parallel wave number and that one of the locations of the wave confluences critically depends on the He-3 concentration made the interpretation of the results, although more complex, very interesting: three regimes could be distinguished as a function of X[He-3]: (i) a regime at low concentration (X[He-3] < 1.8%) at which ion cyclotron resonance frequency (ICRF) heating is efficient, (ii) a regime at intermediate concentrations (1.8 < X[He-3] < 5%) in which the RF performance is degrading and ultimately becoming very poor, and finally (iii) a good heating regime at He-3 concentrations beyond 6%. In this latter regime, the heating efficiency did not critically depend on the actual concentration while at lower concentrations (X[He-3] < 4%) a bigger excursion in heating efficiency is observed and the estimates differ somewhat from shot to shot, also depending on whether local or global signals are chosen for the analysis. The different dynamics at the various concentrations can be traced back to the presence of 2 MC layers and their associated FW cutoffs residing inside the plasma at low He-3 concentration. One of these layers is approaching and crossing the low-field side plasma edge when 1.8 < X[He-3] < 5%. Adopting a minimization procedure to correlate the MC positions with the plasma composition reveals that the different behaviors observed are due to contamination of the plasma. Wave modeling not only supports this interpretation but also shows that moderate concentrations of D-like species significantly alter the overall wave behavior in He-3-H plasmas. Whereas numerical modeling yields quantitative information on the heating efficiency, analytical work gives a good description of the dominant underlying wave interaction physics

Answers and Solutions

Answers and solutions to the puzzles in this issue

perbedaan Pengaruh Latihan Kombinasi Lari-Lompat Tanah Datar dan Tanah Berpasir Terhadap Peningkatan Power Otot Tungkai Pada Mahasiswa Pembinaan Prestasi Taekwondo POK FKIP UNS Tahun 2017

ABSTRAK Alif Fatkhurahman. PERBEDAAN PENGARUH LATIHAN KOMBINASI LARI-LOMPAT TANAH DATAR DAN TANAH BERPASIR TERHADAP PENINGKATAN POWER OTOT TUNGKAI PADA MAHASISWA PEMBINAN PRESTASI TAEKWONDO POK FKIP UNS TAHUN 2017. Skripsi, Fakultas Keguruan dan Ilmu Pendidikan Universitas Sebelas Maret Surakarta. Maret 2018. Tujuan penelitian ini adalah untukmengetahui: 1) Pengaruh latihan kombinasi lari – lompat tanah datar terhadap peningkatan Power Otot Tungkai pada mahasiswa pembinan prestasi taekwondo POK FKIP UNS Tahun 2017. 2) Pengaruh latihan kombinasi lari – lompat tanah berpasir terhadap peningkatan Power Otot Tungkai pada mahasiswa pembinan prestasi taekwondo POK FKIP UNS Tahun 2017. 3) Perbedaan pengaruh latihan kombinasi lari – lompat tanah datar dan tanah berpasir terhadap peningkatan Power Otot Tungkai pada mahasiswa pembinan prestasi taekwondo POK FKIP UNS Tahun 2017. Penelitian ini merupakan eksperimen, populasi dan sampel dalam penelitian ini adalah mahasiswa putra pembinaan prestasi taekwondo POK FKIP UNS yang berjumlah 20 mahasiswa. Sampel dalam penelitian ini dibagi menjadi 2 kelompok, kelompok 1 sejumlah 10 orang dengan mendapatkan pelatihan lari-lompat tanah datar dan kelompok 2 sejumlah 10 orang dengan mendapatkan pelatihan lari-lompat tanah berpasir. Proses pembagian kelompok menggunakan teknik ordinal pairing. Teknik analisis data menggunakan uji t-test. Hasil penelitian diperoleh kesimpulan bahwa ada pengaruh latihan kombinasi lari-lompat tanah datar terhadap peningkatan Power Otot Tungkai pada mahasiswa pembinaan prestasi taekwondo POK FKIP UNS Tahun 2017, hal ini ditunjukkan dengan nilai thitung = 12,537 > ttabel = 1,83 ini berarti ada perbedaan yang signifikan antara data pre test dengan data post test pada kelompok eksperimen 1 (latihan kombinasi lari-lompat di tanah datar). Ada pengaruh latihan kombinasi lari-lompat tanah berpasir terhadap peningkatan Power Otot Tungkai pada mahasiswa pembinaan prestasi taekwondo POK FKIP UNS Tahun 2017, hal ini ditunjukkan dengan thitung = 14,581 > ttabel = 1,83 ini berarti ada perbedaan yang signifikan antara data pre test dengan data post test pada kelompok eksperimen 2 (latihan kombinasi lari-lompat di tanah berpasir). Ada perbedaan pengaruh latihan kombinasi lari-lompat tanah datar dan tanah berpasir terhadap peningkatan Power Otot Tungkai pada mahasiswa pembinaan prestasi taekwondo POK FKIP UNS Tahun 2017, hal ini ditunjukkan dengan nilai thitung = 3,131 > ttabel = 1,83. Hasil ini menunjukkan bahwa metode latihan kombinasi lari-lompat di tanah berpasir lebih baik dibandingkan dengan metode latihan kombinasi lari-lompat di tanah datar terhadap peningkatan power otot tungkai mahasiswa pembinaan prestasi taekwondo POK FKIP UNS Tahun 2017. Kata kunci: Power otot tungkai, metode latihan lari-lompat, tanah datar, tanah berpasir. �ABSTRACT Alif Fatkhurahman. INFLUENCE of DIFFERENCE EXERCISE COMBINATION RUN-JUMP FLAT GROUND and SANDY SOIL AGAINST INCREASED POWER LIMB MUSCLES on STUDENT ACHIEVEMENT COACHING FKIP UNS POK TAEKWONDO YEAR 2017. Thesis, Faculty of teacher training and educational sciences of the University Sebelas maret Maret Surakarta. March 2018. The purpose of this research is untukmengetahui: 1) the influence of combination of exercise running jump – flat ground against increased Power limb muscles on student achievement pembinan FKIP UNS POK taekwondo Year 2017. 2) influence of combination of exercise running jump – sandy soil against increased Power limb muscles on student achievement pembinan FKIP UNS POK taekwondo Year 2017. influence of Difference exercise 3) combination of the run – skip the flat ground and sandy soil against increased Power limb muscles on student achievement pembinan FKIP UNS POK taekwondo Year 2017. This research is experimental, the population and the sample in this research is a student son coaching taekwondo POK FKIP UNS achievements that add up to 20 students. The sample in this research are divided into two groups, group 1 a number of 10 people by getting the training run-flat ground and jump Group 1 a number of 10 people by getting the training run-jump-sandy soil. The process uses ordinal group Division pairing. Data analysis techniques using a t-test test. The research results obtained conclusions that there was influence of exercise a combination of run-flat land the jump to increased Power limb muscles on student achievement coaching taekwondo POK FKIP UNS Year 2017, it is indicated by the value of thitung = 12.537 > ttabel = 1.83 this means there is a significant difference between the data pre test post test data on the experimental group 1 (combination workouts run-jump across flat ground). There is the influence of combination of exercise running jump-sandy soil to increased Power limb muscles on student achievement coaching taekwondo POK FKIP UNS Year 2017, it is indicated with thitung = 14.581 > ttabel = 1.83 this means there are differences that significantly between the data pre test post test data on the experimental group 2 (practice run-jump combination in the sandy soil). There is a difference of influence of exercise running-jump combination flat ground and sandy soil to increased Power limb muscles on student achievement coaching taekwondo POK FKIP UNS Year 2017, it is indicated by the value of thitung = ttabel > 3.131 = 1.83. These results indicate that the method combination exercises run-jump across the sandy soil is better compared with the method of exercise combinations run-jump across the flat land to increased power student achievement coaching limb muscles taekwondo POK FKIP UNS The year 2017. Keywords: Power method of limb muscles, exercise run-jump, flat ground, sandy soil

Modelling of the effect of ELMs on fuel retention at the bulk W divertor of JET

Effect of ELMs on fuel retention at the bulk W target of JET ITER-Like Wall was studied with multi-scale calculations. Plasma input parameters were taken from ELMy H-mode plasma experiment. The energetic intra-ELM fuel particles get implanted and create near-surface defects up to depths of few tens of nm, which act as the main fuel trapping sites during ELMs. Clustering of implantation-induced vacancies were found to take place. The incoming flux of inter-ELM plasma particles increases the different filling levels of trapped fuel in defects. The temperature increase of the W target during the pulse increases the fuel detrapping rate. The inter-ELM fuel particle flux refills the partially emptied trapping sites and fills new sites. This leads to a competing effect on the retention and release rates of the implanted particles. At high temperatures the main retention appeared in larger vacancy clusters due to increased clustering rate

Velocity-space sensitivity of the time-of-flight neutron spectrometer at JET

The velocity-space sensitivities of fast-ion diagnostics are often described by so-called weight functions. Recently, we formulated weight functions showing the velocity-space sensitivity of the often dominant beam-target part of neutron energy spectra. These weight functions for neutron emission spectrometry (NES) are independent of the particular NES diagnostic. Here we apply these NES weight functions to the time-of-flight spectrometer TOFOR at JET. By taking the instrumental response function of TOFOR into account, we calculate time-of-flight NES weight functions that enable us to directly determine the velocity-space sensitivity of a given part of a measured time-of-flight spectrum from TOFOR

On the mechanisms governing gas penetration into a tokamak plasma during a massive gas injection

A new 1D radial fluid code, IMAGINE, is used to simulate the penetration of gas into a tokamak plasma during a massive gas injection (MGI). The main result is that the gas is in general strongly braked as it reaches the plasma, due to mechanisms related to charge exchange and (to a smaller extent) recombination. As a result, only a fraction of the gas penetrates into the plasma. Also, a shock wave is created in the gas which propagates away from the plasma, braking and compressing the incoming gas. Simulation results are quantitatively consistent, at least in terms of orders of magnitude, with experimental data for a D 2 MGI into a JET Ohmic plasma. Simulations of MGI into the background plasma surrounding a runaway electron beam show that if the background electron density is too high, the gas may not penetrate, suggesting a possible explanation for the recent results of Reux et al in JET (2015 Nucl. Fusion 55 093013)