Plasma & Laser Diagnostics

EUV / VUV detectors are used for calculating the fractional abundance of ions for hot plasmas with different electron temperatures and electron densities.

They are used to characterise wavelengths and the emissivity versus temperature of the brightest spectral lines emitted by ions with wavelengths longer than 45 Å. ITER plasmas can be analysed using selected EUV lines, similar to the space-based instruments routinely used to study temperatures, emission lines and motions of 0.1–2 keV solar coronal plasmas.

It is important to match the detector yield over the entire spectral range whilst maintaining good spatial as well as temporal resolution. It is possible to use direct and indirect detection. Direct detection is achieved by selecting back thinned CMOS sensors in order to optimise quantum efficiency in the range of 100 eV and above. With a band gap of 3.5 eV on average, each photon is well discriminated, however coping with bright signals can be issue. Indirect detection can be used with either an MCP or phosphor screen assembly read out by a CMOS detector with giving a better compromise on dynamic range.

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