Simulation of ITER ICWC scenarios in JET

Encouraging results recently obtained with alternative ion cyclotron wall conditioning (ICWC) in the present-day tokamaks and stellarators have elevated ICWC to the status of one of the most promising techniques available to ITER for routine interpulse conditioning in the presence of the permanent high toroidal magnetic field. The paper presents a study of ICWC discharge performance and optimization of the conditioning output in the largest tokamak JET using the standard ICRF heating antenna A2 in a scenario envisaged at ITER full field, BT=5.3 T: on-axis location of the fundamental ICR for deuterium, ω=ωcD+. The perspective of application of the alternative technique in ITER is analyzed using the 3-D MWS electromagnetic code, 1-D RF full wave and 0-D plasma codes.Обнадёживающие результаты по альтернативной ионно-циклотронной (ИЦ) чистке поверхностей вакуумной камеры, полученные недавно на современных токамаках и стеллараторах, выдвинули этот метод в число наиболее вероятных технологий, планирующихся использовать в ITERe между импульсами в присутствии постоянного сильного тороидального магнитно поля. В настоящей работе представлены результаты исследований ВЧ-разряда и его оптимизаци по усилению эффекта чистки в крупнейшем из ныне действующих токамаке JET с использованием стандартных ИЦ A2 антенн. Эксперименты по ВЧ-чистке на JETе были осуществлены в режиме, моделирующем сценарий ИЦ-разряда в токамаке-реакторе ITER, при работе на полном магнитном поле BT=5.3 T и при расположении фундаментального ИЦ-резонанса для дейтерия ω=ωcD+ в центре вакуумной камеры. Перспективы применения альтернативной ВЧ-чистки в ITERе анализируются с помощью численных кодов: 3-D MWS- электромагнитного кода, 1-D ВЧ-кода и 0-D плазменного кода.Обнадійливі результати з альтернативної іонної циклотронної (ІЦ) чистки поверхонь вакуумної камери, отримані останнім часом в сучасних токамаках і стелараторах, висунули цей метод до числа найбільш вірогідних технологій, які планується використовувати в ІТЕРі між імпульсами в присутності постійного сильного тороїдального магнітного поля. В роботі представленo результати дослідження ВЧ-розряду та його оптимізації щодо підсилення ефекту чистки в найбільшому з нині діючих токамаці JET з використанням стандартних ІЦ А2 антен. Експерименти по ВЧ-чищенню на JETі були здійснені в режимі, що моделює сценарій ІЦ-розряду в токамаці-реакторі ITER, при роботі на повному магнітному полі BT=5.3 T та при розміщенні фундаментального ІЦ-резонансу для дейтерію ω=ωcD+ в центрі вакуумної камери. Перспективи застосування альтернативної ВЧ-чистки в ITERі аналізуються за допомогою числових кодів: 3-D MWS- електромагнітного коду, 1-D ВЧ-коду і 0-D плазмового коду

Development of Scientific Simulation 3D Full Wave ICRF Code for Stellarators and Heating/CD Scenarios Development

In this report we describe theory and 3D full wave code description for the wave excitation, propagation and absorption in 3-dimensional (3D) stellarator equilibrium high beta plasma in ion cyclotron frequency range (ICRF). This theory forms a basis for a 3D code creation, urgently needed for the ICRF heating scenarios development for the operated LHD, constructed W7-X, NCSX and projected CSX3 stellarators, as well for re evaluation of ICRF scenarios in operated tokamaks and in the ITER . The theory solves the 3D Maxwell-Vlasov antenna-plasma-conducting shell boundary value problem in the non-orthogonal flux coordinates ({Psi}, {theta}, {var_phi}), {Psi} being magnetic flux function, {theta} and {var_phi} being the poloidal and toroidal angles, respectively. All basic physics, like wave refraction, reflection and diffraction are self consistently included, along with the fundamental ion and ion minority cyclotron resonances, two ion hybrid resonance, electron Landau and TTMP absorption. Antenna reactive impedance and loading resistance are also calculated and urgently needed for an antenna -generator matching. This is accomplished in a real confining magnetic field being varying in a plasma major radius direction, in toroidal and poloidal directions, through making use of the hot dense plasma wave induced currents with account to the finite Larmor radius effects. We expand the solution in Fourier series over the toroidal ({var_phi}) and poloidal ({theta}) angles and solve resulting ordinary differential equations in a radial like {Psi}-coordinate by finite difference method. The constructed discretization scheme is divergent-free one, thus retaining the basic properties of original equations. The Fourier expansion over the angle coordinates has given to us the possibility to correctly construct the ''parallel'' wave number k{sub //}, and thereby to correctly describe the ICRF waves absorption by a hot plasma. The toroidal harmonics are tightly coupled with each other due to magnetic field inhomogeneity of stellarators in toroidal direction. This is drastically different from axial symmetric plasma of the tokamaks. The inclusion in the problem major radius variation of magnetic field can strongly modify earlier results obtained for the straight helical, especially for high beta plasma, due to location modification of the two ion hybrid resonance layers. For the NCSX, LHD, W7-AS and W7-X like magnetic field topology inclusion in our theory of a major radius inhomogeneity of the magnetic field is a key element for correct description of RF power deposition profiles at all. The theory is developed in a manner that includes tokamaks and magnetic mirrors as the particular cases through general metric tensor (provided by an equilibrium solver) treatment of the wave equations. We describe that newly developed stellarator ICRF 3D full wave code PSTELION, based on theory described in this report. Applications to tokamaks, ITER, stellarators and benchmarking with 2D TORIC and 3D AORSA codes are given in included subreport

3D Electromagnetic Theory of ICRF Multi Port Multi Loop Antenna

"In this report the theory of three dimensional antenna in lon Cyclotron Resonance Frequency (ICRF) is developed for a plasma with circular magnetic surfaces. The multi loop antenna is located in ITER several ports. Circular plasma and antenna geometry provides new important tools to account for: l) right loading antenna impedance matrix calculation urgently needed for a matching of RF generator with an antenna; 2) right calculation of an antenna toroidal and poloidal excited spectra because the DIFFRACTION, refraction and REFLECTION effects for the Fast Waves (FW) are in FIRST time are included self consistently in 3D ICRF antenna - plasma treatment; 3) right calculation of RF power deposition profiles because self consistently found 3D antenna - plasma FW excited spectra in non slab plasma model are important ones in a weakly dissipated plasma for Fast Waves (even for ITER parameters). In the developed theory multi loop antennae are located in several ITER ports with arbitrary relative toroidal and poloidal positions. It gives great flexibility of investigation possibility for production of an optimal ICRF antenna directivity in conditions of limited toroidal space in a reactor port and a possibility to control widness of excited FW k - spectra to control RF power deposition profiles into a plasma. The above theory allows to calculate RF losses on a Faraday screen bars. In the model developed each loop is located in a special individual recess in a tokamak port to control in some extent mutual coupling between loops through a vacuum port region and simulteneously to support the Faraday screen bars. The theory developed accounts for two options for poloidal loops: to be located INSIDE of each sub recess (with a smaller mutual loops coupling) and to be located OUTSIDE of each sub recess (more closely to plasma) with an increased antenna loading resistance. Radial antenna loops feeders are taken into account as well. The MULTI PORT structure of the theory gives another important tool to control mutual coupling of loops: it is possible to locate one port just near another one with, for example, only two loops in each sub PORT just simulating contineous conducting boundary between several loops (besides of sub recess walls). Another possibility is to simulate extended toroidal port size to improve an antenna directivity. The information about plasma properties comes into antenna theory through plasma surface impedance matrix Y_mm and is calculated separately by fast MlNTOR2 code described in Part A. According to theory developed the ANPORT code has been written. The first runs indicated strong mutual loops coupling of ITER now designed antenna. The work is under progress.

3D Maxwell-Vlasov Boundary Value Problem Solution in Stellarator Geometry in Ion Cyclotron Frequency Range (final report)

"In this report we develop the theory for the wave excitation, propagation and absorption in 3-dimensional (3D) stellarator equilibrium high beta plasma in ion cyclotron frequency range (ICRF). This theory forms a basis for a 3D code creation, urgently needed for the ICRF heating scenarios development for the constructed LHD [1] and projected W7-X [2] stellarators and for the stellarators being at operation (like CHS, W7-AS, etc.). The theory solves the 3D Maxwell-Vlasov antenna-plasma-conducting shell boundary value problem in the non - orthogonal flux coordinates (psi,theta,varphi), psi being magnetic flux function, theta and varphi being the poloidal and toroidal angles, respectively. All basic physics, like wave refraction, reflection and diffraction are firstly self consistently included, along with the fundamental ion and ion minority cyclotron resonances, two ion hybrid resonance, electron Landau and TTMP absorption. Antenna reactive impedance and loading resistance are also calculated and urgently needed for an antenna -generator matching. This is accomplished in a real confining magnetic frield being varying in a plasma major radius direction, in toroidal and poloidal directions, through making use of the hot dense plasma dielectric kinetic tensor. We expand the solution in Fourier series over toroidal (varphi ) and poloidal (theta) angles and solve resulting ordinary differential equations in a radial like psi - coordinate by finite difference method. The constructed discretization scheme is divergent - free one, thus retaining the basic properties of original equations. The Fourier expansion over angle coordinates has given to us the possibility to correctly construct the ""parallel"" wave number k_parallel and thereby to correctly describe the ICRF waves absorption by a plasma. The toroidal harmonics are tightly coupled with each other due to magnetic field inhomogenity of stellarators in toroidal direction. This is drastically different from axial symmetric plasma of the tokamaks. The inclusion in the problem major radius variation of magnetic field can strongly modify earlier results obtained for the straight helical, especially for high beta plasma, due to modification of locations of the two ion hybrid resonance layers. For W7-X Iike magnetic field topology the inclusion in our theory of a major radius inhomogenity of the magnetic field is a key element for correct description of RF power deposition profiles at all. The theory is developed in a manner that includes tokamaks and magnetic mirrors as the particular cases through general metric tensor (provided by an equilibrium solver) treatment of the wave equations. We describe the structure of newly developed stellarator ICRF 3D full wave code STELION, based on theory described in this report.