Self-consistent calculation of the starting pitch factor of TE modes in gyrotron cavities

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The internal electric field in multilayer organic light-emitting diodes (OLEDs) is investigated using a combination of experimental measurement and numerical device modeling. This approach results in a detailed understanding of the functioning of a multilayer OLED. The method is applied to a standard device structure that has received broad attention in literature. From the experimental part, we have demonstrated that the average electric field inside the hole transport layer is larger than or equal to the

The electron cyclotron heating (ECH) system in TCV has recently been upgraded to a total of 4.5 MW of installed power. In order to extend the density range of ECH-heated plasmas up to electron densities of 1.2 x 10(20) m(-3), three 0.5 MW gyrotrons at a frequency of 118 GHz have been added to the existing 3 MW second harmonic system operating at a frequency of 82.7 GHz. The launcher consists of a mirror placed at the top of the vessel that collects the power of the three microwave sources and can be steered

The finite element method has been employed in order to simulate the behaviour of a HTS cable for transport current applications. The E-J model includes an anisotropic dependence of the critical current density Jc and power index n on the local magnetic field, whose magnitude is non-negligible and determines the effective critical current of the cable. The cable consists of four electrically insulated layers, each of them composed by 20 superconducting tapes, providing a total critical current of about 4 kA

Observations of nearly zero toroidal current in the central region of tokamaks (the "current hole") raises the question of the existence of toroidal equilibria with very low or reversed current in the core. The solutions of the Grad-Shafranov equilibrium equation with hollow toroidal current density profile including negative current density in the plasma center are investigated. Solutions of the corresponding eigenvalue problem provide simple examples of such equilibrium configurations. More realistic equi

In this paper, we present a novel Brillouin fiber-ring laser utilizing an unbalanced Mach-Zehnder interferometer (UMZI) as coupling device. The laser is pumped by a distributed-feedback laser diode and shows continuous-wave and single-frequency operation. Frequency-dependent transmission characteristics of the UMZI make it possible for the pump wave to pass through the laser-ring cavity with no resonance effect for stable pump operation, while the Brillouin laser signal still resonates in a high-finesse cav

Based on a mathematical model, simulation results show how the mechanical performances of the motor are sensitive to the prestressing force. A test bench has been developed in the laboratory for experimental measurements. The motor is driven by a two-phase resonant converter controlled by a DSP in order to realize a flexible control scheme. An hysteresis brake dynamometer controlled by PC make it possible to generate any load profile. Results obtained by measurement confirm the motor sensitivity to the vari

The development of high-power gyrotrons (118 GHz, 140 GHz) in continuous-wave (CW) operation for heating nuclear fusion plasmas has been in progress for several years in a joint collaboration between different European research institutes and industrial partners. The 140-GHz gyrotron being under development for the installation at the W7-X stellarator now under construction at the IPP Greifswald, Germany, operates in the TE28,8 mode and is equipped with a diode type magnetron injection electron gun, an impr

The TCV tokamak (R = 0.88 in, a < 0.25 in, BT < 1.54 T) is equipped with six 0.5 MW gyrotron sources operating at 82.7 GHz for second harmonic X mode ECH. By distributing the ECCD current sources over the discharge cross section, fully driven stationary plasmas with I-p = 210 kA, n(e0) = 2 x 10(19) m(-3), T-e0 approximate to 4 keV, were obtained for the full discharge duration of 2 s. Highly peaked electron temperature profiles with T-e0 up to 12 keV were obtained in central counter-current drive scenarios

We have made a software electromagnetic simulation of eddy current effects in Bi(2223)Ag sheathed tapes with applied AC transport current in a broad frequency range. We have used simple models of monocore and multicore tapes. Calculated is the power distribution (W/m3) within the metal sheath using the geometry of real tapes. The numerical simulation is carried out with Finite-element-method software. The paper also describes the influence of the tape cross-sectional architecture and the sheath resistivity

A two-dimensional PIC code aimed at the investigation of electron-cyclotron beam instabilities in gyrotrons and their effects on the beam quality is presented, The code is based on recently developed techniques for handling charge conservation and open boundaries and uses an electromagnetic field which is decomposed in its transverse magnetic (TM) and electric (TE) components, The code has been implemented on the massively parallel computer CRAY T3D, but can also be run on a single processor of the CRAY Y-M

The digital transient torque measuring device presented in this paper is able to make a "real time" calculation in steady-state and transient conditions of the electromagnetic torque or force of an extremely wide range of ac electrical machines supplied with sinusoidal voltages or through frequency converters with frequencies up to 30 kHz. The device needs no shaft position or speed sensors, it uses exclusively the acquisition of the stator currents and voltages. The main fields of applications are: test sh

The spontaneous and stimulated emissions of strongly excited GaAs/(Ga,Al)As quantum wells are investigated in the one-dimensional optical amplifier geometry, using the variable-stripe-length method. The optical amplification and its saturation are studied by monitoring the spectra of spontaneous and amplified luminescence as a function of the position on the stripe. The deduced experimental spatial dependences of carrier and luminous densities are found to agree in a semiquantitative way with the numerical

Self-consistent calculation of the starting pitch factor of TE modes in gyrotron cavities

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Internal electric field and charge distribution in multilayer organic light-emitting diodes

Preliminary results of top launch third harmonic X-mode electron cyclotron heating in the TCV tokamak

Numerical Modelling of a HTS Cable

Tokamak equilibria with reversed current density

Brillouin fiber laser pumped by a DFB laser diode

Influences to the mechanical performances of the travelling wave ultrasonic motor by varying the prestressing force between stator and rotor

Development of a 140-GHz 1-MW continuous wave gyrotron for the W7-X stellarator

Overview of TCV results

Effect of the sheath resistivity and tape geometry on eddy current loss in Bi(2223) tapes

G2DEM: A parallel two-dimensional electromagnetic PIC code for the study of electron-cyclotron instabilities of relativistic electron beams in cylindrical cavities

Digital transient torque measurement for rotating or linear AC machines (real time measurement)

Optical Amplification and Its Saturation in Semiconductor Quantum-Wells