First results of dust injection in T-10 plasma

First results of T-10 injection experiments of the carbon dust particles with 2-10 mm diameter and 40-300 m/s velocity are presented. Different scenarios of the dust injection were tested. The dust particles ablation was studied. An approach for determination of a dust particle penetration length was developed. Measured penetration depths (3-7 cm) are compared with the simulation by the ablation model. The mm range of the separate dust particle diameters derived from the ablation data was close to sizes of the dust injected assuming that an acceleration of the separate particle is similar to the large carbon pellet in the pellet injector.Представлено перші результати експериментів по інжекції вуглецевих пилових часток діаметром 2-10 мкм зі швидкостями 40-300 м/с у Т-10. Протестовано різні сценарії інжекції пилу. Досліджено випар пилових часток. Розроблено приблизну методику визначення глибини проникнення пилових часток. Обміряні глибини проникнення (3-7 см) порівнювалися з розрахунками по моделі випару. Оцінені мікронні діаметри часток, отримані з даних по випару, є близькими до розмірів інжектованого пилу, у припущенні того, що окремі частки прискорюються так само, як і при інжекції великих пелетів.Представлены первые результаты экспериментов по инжекции углеродных пылевых частиц диаметром 2-10 мкм со скоростями 40-300 м/с в Т-10. Протестированы различные сценарии инжекции пыли. Исследовано испарение пылевых частиц. Разработана приблизительная методика определения глубины проникновения пылевых частиц. Измеренные глубины проникновения (3-7 см) сравнивались с расчетами по модели испарения. Оцененные микронные диаметры частиц, полученные из данных по испарению, близки к размерам инжектированной пыли, в предположении того, что отдельные частицы ускоряются так же, как и при инжекции крупных пеллетов

Inverse magnetic catalysis in field theory and gauge-gravity duality

We investigate the surface of the chiral phase transition in the three-dimensional parameter space of temperature, baryon chemical potential and magnetic field in two different approaches, the field-theoretical Nambu-Jona-Lasinio (NJL) model and the holographic Sakai-Sugimoto model. The latter is a top-down approach to a gravity dual of QCD with an asymptotically large number of colors and becomes, in a certain limit, dual to an NJL-like model. Our main observation is that, at nonzero chemical potential, a magnetic field can restore chiral symmetry, in apparent contrast to the phenomenon of magnetic catalysis. This "inverse magnetic catalysis" occurs in the Sakai-Sugimoto model and, for sufficiently large coupling, in the NJL model and is related to the physics of the lowest Landau level. While in most parts our discussion is a pedagogical review of previously published results, we include new analytical results for the NJL approach and a thorough comparison of inverse magnetic catalysis in the two approaches.Comment: 37 pages, 11 figures, to appear in Lect. Notes Phys. "Strongly interacting matter in magnetic fields" (Springer), edited by D. Kharzeev, K. Landsteiner, A. Schmitt, H.-U. Ye

Lattice QCD Simulations in External Background Fields

We discuss recent results and future prospects regarding the investigation, by lattice simulations, of the non-perturbative properties of QCD and of its phase diagram in presence of magnetic or chromomagnetic background fields. After a brief introduction to the formulation of lattice QCD in presence of external fields, we focus on studies regarding the effects of external fields on chiral symmetry breaking, on its restoration at finite temperature and on deconfinement. We conclude with a few comments regarding the effects of electromagnetic background fields on gluodynamics.Comment: 31 pages, 10 figures, minor changes and references added. To appear in Lect. Notes Phys. "Strongly interacting matter in magnetic fields" (Springer), edited by D. Kharzeev, K. Landsteiner, A. Schmitt, H.-U. Ye

Magnetic Catalysis: A Review

We give an overview of the magnetic catalysis phenomenon. In the framework of quantum field theory, magnetic catalysis is broadly defined as an enhancement of dynamical symmetry breaking by an external magnetic field. We start from a brief discussion of spontaneous symmetry breaking and the role of a magnetic field in its a dynamics. This is followed by a detailed presentation of the essential features of the phenomenon. In particular, we emphasize that the dimensional reduction plays a profound role in the pairing dynamics in a magnetic field. Using the general nature of underlying physics and its robustness with respect to interaction types and model content, we argue that magnetic catalysis is a universal and model-independent phenomenon. In support of this claim, we show how magnetic catalysis is realized in various models with short-range and long-range interactions. We argue that the general nature of the phenomenon implies a wide range of potential applications: from certain types of solid state systems to models in cosmology, particle and nuclear physics. We finish the review with general remarks about magnetic catalysis and an outlook for future research.Comment: 37 pages, to appear in Lect. Notes Phys. "Strongly interacting matter in magnetic fields" (Springer), edited by D. Kharzeev, K. Landsteiner, A. Schmitt, H.-U. Yee. Version 2: references adde

Conceptual design of pellet charge eXchange (PCX) diagnostics for stellarator W7-X

Pellet Charge eXchange diagnostic using Li pellets has been considered for the W7-X machine. Geometry of the experimental set-up and parameters of both lithium pellet injector (LPI) and neutral particle analyser (NPA) were evaluated. It was shown that this diagnostics can provide very well detectable H"0 signal in the range 50 - 1000 keV generated by RF driven H"+ minority ions in W7-X. The PCX diagnostics will be able to measure H"+ energy spectra and density profiles in wide range of W7-X plasma parameters. The proposed NPA can be designed on a basis of the NPA ISEP (Ioffe institute) installed now on JET. A pellet light-gas gun can be used to accelerate Li pellets of 2 - 3 mm in size up to 1 km/s velocities. That provides the required pellet penetration into the plasma core. Due to sticky problems with Li operation, a special technique of loading and keeping the pellets in a charger unit of LPI has to be developed. Development of PCX diagnostics for absolute measurements of the confined minority protons requires improvement of the pellet ablation model used. Knowledge of the cloud dimensions and density distributions of different charge states of ions is of special interest. It is necessary to improve predictions of pellet penetrations in non-Maxwellian plasmas as well. An optical system for measurements of pellet cloud density profiles should be foreseen on W7-X. (orig.)Available from TIB Hannover: RA 71(10/20) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman