Index of content:
Volume 77, Issue 12, December 2006
- NUCLEAR PHYSICS, FUSION AND PLASMAS
77(2006); http://dx.doi.org/10.1063/1.2400667View Description Hide Description
We report here a design of the portable high current generator, which can be used for a row of experiments and applications, including, but not limited to, pinch, plasma focus, vacuum spark, etc. The generator consists of the capacitor bank, multigap spark switch, load chamber, and built-in high voltage triggering generator. The capacitor bank consists of 12 General Atomics 35404 type capacitors (, , , ). It stores at charging voltage. Each three capacitors are commuted to a load by the multigap spark switch, which is able to commute by eight parallel channels. Switches operate in ambient air at atmospheric pressure. At charging voltage the generator provides with rise time and inductive load and with rise time and . Delay of output pulse relative to high voltage triggering pulse is with jitter. The dimensions of the generator are and the weight is , and only one high voltage power supply is required as additional equipment for the generator. The generator with a pumping system is placed on area about . Operation and handling are very simple, because no oil nor purified gases are required for the generator. The generator has been successfully employed for experiments on the Ni pinch load. X-ray pulse duration (full width at half maximum above ) was about . Radiation yield was observed in the range and in the energy range, which is comparable to results, obtained on the nanosecond accelerators. Clearly resolved images of wire indicate micron level size of hot spot. These results demonstrate possibility of this generator for application for x-ray backlighting.
77(2006); http://dx.doi.org/10.1063/1.2403091View Description Hide Description
Compatible operation of steady state mode and pulse mode is realized in the KT-5D device. New power supplies with the operation control systems for the steady state toroidalmagnetic field as well as for the vertical field are added, and the rf wave injection systems for sustaining steady state plasmas are upgraded. After the modification, the device now can work not only as a tokomak with pulsed plasma currents as it was but also as a simple magnetized torus with steady state plasma discharges. It allows more flexible and efficient experimental researches on the magnetically confined plasmas to be carried on in the same device.
Development of a pulsed-biasing system and temperature measurement techniques for transient heating experiments on plasma-material interactions77(2006); http://dx.doi.org/10.1063/1.2403938View Description Hide Description
A power switching system has been developed to reverse the voltage polarity on the sample holder of PISCES-B from negative to positive potential in the microsecond time scale. Positive biasing draws electrons from the steady-state plasma through the sample, creating Ohmic heating on the surface. This pulsed biasing is used to replicate the transient heat loads that will be seen on plasma facing components during transient events, such as edge localized modes, in a device such as ITER. Surface temperatures are measured using two pyrometry techniques, a fast two-color system and a slower, more sensitive spectral system.
77(2006); http://dx.doi.org/10.1063/1.2400216View Description Hide Description
We describe the polarimetric characterization in the far infrared of a set of metallic mirrors and of a corner cube retroreflector whose surface has been exposed to a tokamakplasma. The objective of the measurements was to investigate possible changes of the polarization state of the incident radiation due to plasma depositions and identify possible sources of errors for the measurement of the ITER profile by far-infrared (FIR) polarimetry. Tests have been made on Mo and Cu mirrors exposed to the plasma in TEXTOR and Tore Supra. A corner cube retroreflector exposed in Tore Supra was also tested. The thickness and composition of the plasma depositions on these optical elements were known by previous surface analysis and visible ellipsometry studies. Our tests have been carried out in the FIR laboratory of the RFX experiment in Padova, Italy, and in the Laser Research Laboratory of the Department of Electrical and Electronic Engineering at University College Cork, Ireland, using a Stokes polarimeter assembled from components of the RFX FIR polarimetric diagnostic. The tests indicate that the plasma depositions on these elements do not affect the polarimetric response of the surface in the FIR, the only noticeable effect being a significant decrease of the reflectivity in a highly damaged region of limited area on the surface of one mirror. No other effect that may prevent the use of mirrors or corner-cube retroreflectors with this kind of surface damage in the poloidal ITER polarimeter has been observed.