Reduced field Scenario with X3 heating in W7-X (original) (raw)

Long Pulse H-Mode Scenarios Sustained by RF Heating on EAST

Plasma Science and Technology, 2015

EAST has demonstrated its capability of long pulse operation using RF heating (LHCD and ICRF) in past experiments. One key issue to realize the long pulse H-mode experiments is to sustain the plasma current for steady state operation. Based on the calculations of the transport code ONETWO and its coupled RF code GENRAY, two scenarios have been proposed to achieve the 10 s H-mode plasma with Ip=400 kA, < ne >=4.5×10 19 m −3 , βN=2, and the 100 s H-mode plasma with Ip=280 kA, < ne >=3.5×10 19 m −3 , βN =1.8 recently. The current drive of lower hybrid wave is an important issue in the two scenarios. An experimental result on lower hybrid current drive in H-mode plasmas on EAST is also presented.

Electron Cyclotron Heating for W7-X: Physics and Technology

Fusion Science and Technology

The W 7-X Stellarator (R = 5.5 m, a = 0.55 m, B<3.0 T), which is presently being built at IPP-Greifswald, aims at demonstrating the inherent steady state capability of stellarators at reactor relevant plasma parameters. A 10 MW ECRH plant with cwcapability is under construction to meet the scientific objectives. The physics background of the different heating-and current drive scenarios is presented. The expected plasma parameters are calculated for different transport assumptions. A newly developed ray tracing code is used to calculate selected reference scenarios and optimize the EC-launcher and in-vessel structure. Examples are discussed and the technological solutions for optimum wave coupling are presented. The ECRH plant consists of 10 RFmodules with 1 MW power each at 140 GHz. The RF-beams are transmitted to the W7-X torus (typically 60 m) via two open multi-beam mirror lines with a power handling capability, which would already satisfy the ITER requirements (24 MW). Integrated full power, cw tests of two RF-modules (gyrotrons and the related transmission line sections) are reported and the key features of the gyrotron-and transmission line technology are presented. As the physics and technology of ECRH for both W7-X and ITER has many similarities, test results from the W7-X ECRH may provide valuable input for the ITER-ECRH plant.

Overview of ECR plasma heating experiment in the GDT magnetic mirror

Nuclear Fusion, 2015

This paper summarizes the results of experiments on electron cyclotron resonance heating (ECRH) of plasma obtained at the axially symmetric magnetic mirror device gas dynamic trap (GDT) (Budker Institute, Novosibirsk). The main achievement is the demonstration of plasma discharges with extremely high temperatures of bulk electrons. According to the Thomson scattering measurements, the on-axis electron temperature averaged over several sequential shots is 660±50 eV with peak values exceeding 900 eV in a few shots. This corresponds to an at least threefold increase as compared to previous experiments both at the GDT and at other comparable machines, thus demonstrating the maximum quasi-stationary (∼0.6 ms) electron temperature achieved in open traps. The breakthrough is made possible with the successful implementation of a sophisticated ECRH scheme in addition to standard heating by neutral beams (NBs). Another important result is the demonstration of the significantly increased lifetime of NB-driven fast particles with the application of ECRH, leading to a 30% higher plasma energy content at the end of the discharge. All available data including the previously demonstrated possibility of plasma confinement with β as high as 60%, allows us to consider fusion applications of axially symmetric magnetic mirror machines on a realistic basis.

Plasma heating due to XB mode conversion in a cylindrical ECR plasma system

Arxiv preprint physics/0410112, 2004

Extra Ordinary (X) mode conversion to Bernstein wave near Upper Hybrid Resonance (UHR) layer plays an important role in plasma heating through cyclotron resonance. Wave generation at UHR and parametric decay at high power has been observed during Electron Cyclotron Resonance (ECR) heating experiments in toroidal magnetic fusion devices. A small linear system with ECR and UHR layer within the system has been used to conduct experiments on X-B conversion and parametric decay process as a function of system parameters. Direct probing in situ is conducted and plasma heating is evidenced by soft x-ray emission measurement. Experiments are performed with hydrogen plasma produced with 160-800 W microwave power at 2.45 GHz of operating frequency at 10 −3 mbar pressure. The axial magnetic field required for ECR is such that the resonant surface (B = 875 G) is situated at the geometrical axis of the plasma system. Experimental results will be presented in the paper. I. INTRODUCTION Electron cyclotron resonance heating (ECRH) is a highly efficient, controllable and localized plasma heating [1] and current drive scheme in fusion machines such as tokamaks [2-5],

Recent Progress in Understanding the Physics of Plasma-Filled, High-Power Microwave Sources

AIP Conference Proceedings

The use of plasmas for generating high-power microwaves is studied for more than 50 years. During the 1990's Plasma-Assisted Slow-wave Oscillators (PASOTRONs) were invented and actively developed at Hughes Research Lab (HRL). These devices have a number of unique and attractive features. However, the experiments at HRL showed that to explore these features a better understanding of the physics is necessary. The present paper is focused on the recent studies of various physical issues, which are important for the pasotron operation. This theoretical and experimental activity resulted in more than doubling the pasotron efficiency (from about 20% to more than 50%) in the experiments carried out at the University of Maryland. CP625, High Energy Density and High Power RF: 5' * Workshop, edited by B. E. Carlsten

Plasma heating by high-energy-content microsecond electron beam at the GOL-3-II facility

Plasma Physics and Controlled Fusion, 1996

A description of the GOL-3-II facility and the first experimental results obtained on this new device are presented. This facility was constructed as part of the second stage of the GOL-3 programme for studying the interaction of microsecond electron beams with a plasma and its fast heating. The plasma column of the GOL-3-II facility is 12 m in length instead of 7 m for the first stage of GOL-3. The energy content of the capacitive storage for magnetic field supply has been increased from 10 MJ to 15 MJ. This allows us to have a magnetic field of up to 5 T in the homogeneous part of the solenoid and up to 10 T in its end mirrors. The expected key feature of the upgrading is an essential increase in the energy content of the electron beam injected into the plasma. The high-power electron beam generator U-2 is now used for the new beam-plasma interaction experiments with possible beam energy content of up to 0.3 MJ. It is shown experimentally that transportation of a 0.2 MJ electron beam through the 12 m plasma column is possible under conditions of almost full current neutralization. The collective beam-plasma interaction results in a plasma heating of up to 1-2 keV electron temperature at ≈ 10 15 cm −3 density.