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We present in this article the description of the upgraded soft x-ray tomographic diagnostic which has been installed in the Madison symmetric torus (MST) reversed field pinch. The previous diagnostic has been extended with two manipulators, for a total of three moveable probes and a fixed one. The line integrated emissivity (brightness) will be measured with arrays of photodiodes and the total number of channels has been increased from 24 to 74. The electronic layout has also been upgraded, and a type of custom made current-to-voltage amplifier has been developed. The diagnostic will be used to continue and extend the magnetohydrodynamics analysis of the MST plasma. The imaging of rotating coherent structures (one or, as recently showed, two) which appear during quasisingle helicity or pulsed poloidal current drive experiments will be performed in more detail. The photocameras can be easily extracted, modified, and inserted again, allowing applications and utilizations of the diagnostic. © 2004 American Institute of Physics.

We describe a prototype linear vacuum-ultraviolet x-ray pinhole camera based on the luminescence of a phosphor screen working in reflection mode. The luminescence emitted by the phosphor, in response to radiation selected by a broadband filter, is detected using a 1024 pixel intensified linear array detector. By operating this detector with integration times from 20 to 50 ms, random plasma fluctuations can be smeared out, so that structures related to the magnetic topology can be searched for.

We describe the application of the singular spectrum analysis (SSA), an advanced adaptive statistical technique, to denoise experimental signals and to remove trends in order to isolate the relevant fluctuating components. We illustrate a fast denoising algorithm and show its performances relatively to synthetic and experimental signals of the soft x-ray (SXR) spectrometer and the polarimeter installed in the reversed field experiment (RFX) device. As a further application, we report a first estimate of the electron temperature fluctuations in the core of the RFX experiment. They have been performed with a multifilter SXR spectrometer and applying SSA for the first time in plasma physics the singular spectrum analysis. We find that temperature fluctuations are typically not larger than a few percent and are well correlated with magnetic fluctuations. (C) 2001 American Institute of Physics.

In RFX a monitor for the measurement of the on-axis electron temperature with high temporal resolution has been designed and operated during the last experimental campaigns. It consists of four soft x-ray (SXR) diodes which observe the plasma through four beryllium filters of different thickness. In this article the main design issues are presented. The measured values of the temperature, computed both with the standard double foil method and with a fit of all the available signals, are reported, correlated with the main plasma parameters and briefly compared with the results of other diagnostics. The main causes of systematic error, the effect of the noise and the reliability of the results in various plasma conditions have been investigated. Dynamic evaluations of the temperature up to a maximum bandwidth of 5 kHz are described, confirming the potentialities of the technique to follow fast phenomena. Possible improvements of the diagnostic and future developments are also pointed out.

Indirect digital imaging sensors employ tailored phosphors screens to convert incident x-ray or vacuum-ultraviolet (VUV) photons to visible light quanta A convenient method to prepare pixelated phosphor screens that can be easily tailored in thickness, type, and spatial resolution is presented. The characterization and evaluation of these screens in the laboratory is addressed and their application to high-resolution VUV and x-ray cameras is discussed.

This addendum applies to papers authored by contributors from the Axially Symmetric Divertor Experiment (ASDEX) Upgrade Team published in Review of Scientific Instruments. This addendum provides the full list of ASDEX Upgrade Team contributors and their affiliations.

The article presents the design and the first results of a new eight camera, soft x-ray (SXR) and bolometric tomography which has been installed in RFX, a large (R=2 m, a=0.46 m), high current reverse field pinch experiment operating in Padova. The main features of the diagnostic, which has been designed with standards compatible with the requirements of large fusion experiments, are: (a) it allows simultaneous reconstruction of both SXR and total radiation emissivity structures with high spatial and time resolution (bandwidth up to 200 kHz for SXR and 10 kHz for bolometry). Moreover, computer controlled remote actions which interchange up to five material filters in front of the detectors allow the exploration of different energy ranges; (b) it can be easily decoupled from the machine without breaking the main vacuum and can be operated during first wall baking up to 300 °C thanks to a cooling circuit; (c) the detection chain is designed to measure very low signals [in the order of 1 nA for SXR diodes an...