The imaging heavy ion beam probe (i-HIBP) developed at the ASDEX Upgrade tokamak is a new diagnostic concept for investigations at the edge of high temperature plasmas. By means of a heavy alkali beam injector, a neutral primary beam of an energy of 70 keV is injected into the fusion plasma, where it is ionized generating a fan of secondary beams. These are deflected by the magnetic field of the tokamak and intersect a scintillator plate in the limiter shadow of the tokamak. The light pattern on the scintillator detected with a high speed camera contains radial information on the density, electrostatic potential and the magnetic field in the edge region of the plasma. For the design of the i-HIBP, a detailed beam model including the 3D tokamak magnetic field and beam attenuation effects for cesium and rubidium atoms is developed in order to find the optimum injection scheme within the limited space of the tokamak environment for maximum 1Corresponding author.
Multi-channel scanning filter spectrometer with narrow band pass of 2 nm is installed in Large Helical Device (LHD) for Beam Emission Spectroscopy (BES) using hydrogen (H) and deuterium beam (D). The spectral shape of transmitted light (half width at half maximum, skewness and kurtosis) is measured using the monitor grating spectrometer coupled with the filter spectrometer. No distortion of the spectrum shape is observed in the wavelength scan range of 8 nm required for the Doppler shift of the BES emission from H-beam and D-beam.
An imaging heavy ion beam probe (i-HIBP) diagnostic, for the
simultaneous measurement of plasma density, magnetic field and
electrostatic potential in the plasma edge, has been installed at
ASDEX Upgrade. Unlike standard heavy ion beam probes, in the i-HIBP
the probing (heavy) ions are collected by a scintillator detector,
creating a light pattern or strike-line, which is then imaged by a
camera. Therefore, a good characterization of the scintillator
response is needed. Previous works focused on the scintillator
behaviour against irradiation with light ions such as hydrogen and
alpha particles. In this work we present the characterization of
several scintillator screens — TG-Green
(SrGa2S4:Eu2
+), YAG-Ce
(Y3Al5O12:Ce3
+) and P11 (ZnS:Ag) —
against irradiation with 133Cs+ ions, in an energy range
between 5 and 70 keV and ion currents between 105 and 107
ions/(s·cm2). Three main properties of the scintillators
have been studied: the ionolumenescence efficiency or yield, the
linearity and the degradation as a function of the fluence. The
highest yield was delivered by the TG-Green scintillator screen with
> 8·103 photons/ion at 50 keV. All the samples showed a
linear response with increasing incident ion flux. The degradation
was quantified in terms of the fluence F1/2, which leads to a
reduction of the emissivity by a factor of 2. TG-Green showed the
lowest degradation with F1/2= 5.4·1014
ions/cm2. After the irradiation the samples were analyzed by
Scanning Electron Microscopy (SEM), Rutherford Backscattering
Spectrometry (RBS) and Particle Induced X-ray Emission (PIXE). No
trace of Cs was found in the irradiated regions. These results
indicate that, among the tested materials, TG-Green is the best
candidate for the i-HIBP detector.
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