12-16 September 2005
University of Liverpool
Europe/Zurich timezone

Novel Position-Sensitive Ion-Current Detector Arrays Using a Self-Collection Method for Secondary-Electron Suppression

Sep 15, 2005, 10:30 AM
45m
University of Liverpool

University of Liverpool

Greenbank Conference Park
Board: P7
Contributed Poster X-ray and Gamma-ray Detectors P : Coffee and Poster Session

Speaker

Dr Junko Kohagura (Plasma Research Centre, University of Tsukuba)

Description

Recent findings of the importance of radially sheared electric-field formation in plasmas enhance the requirements of spatial-profile measurements of ion-confining potentials and ion-current signals simultaneously. For instance, the frequency analyses of end-loss ion- energy spectrometer arrays (IES) signals show the existence of electron drift waves, giving a peaked structure over a few kHz and turbulence-like fluctuations without any coherent azimuthal phasing relation below a few kHz during a weaker sheared period. On the other hand, some finite levels of turbulent fluctuations and remarkable suppression of turbulence are found during a stronger sheared period with ECH. This encourages the usefulness of potentials and radial electric-field shear for confinement improvements. For the purpose of observations of these important parameters, we have been developing several types of multigridded electrostatic ion- energy spectrometers and ion-current detectors because of their compact-sized simple structures and convenient handling without the effects on the plasma-confining magnetic fields of the plasma device. These ion-diagnostics are proposed to obtain precise ion- energy spectra and absolute values of ion currents without any perturbations from simultaneously incident energetic electrons into the arrays. For instance, the ion-current detector consists of a set of parallel metal plates with respect to lines of ambient magnetic forces of a plasma device for analyzing incident ion currents along with a grid for shielding the collector against strays due to the metal-plate biasing. One of the most essential characteristic properties of the proposed detector is based on the physics principle of a “self-collection” mechanism for suppressing the effects of secondary-electron emission from a metal collector. Availability of the detector is clearly demonstrated in the GAMMA10 plasma experiments.

Primary author

Dr M Hirata (Plasma Research Centre, University of Tsukuba,)

Co-author

Dr Junko Kohagura (Plasma Research Centre, University of Tsukuba)

Presentation materials