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ITER vacuum vessel showing plasma diagnostics systems

UKAEA Culham is researching and developing the LIDAR Thomson scattering and charge exchange recombination spectroscopy (CXRS) systems for the 5 billion Euro ITER project (the international successor to JET) under construction in France. ITER will be a major experimental facility, demonstrating the scientific and technical feasibility of fusion power. Companies with expertise or specific products relevant to the LIDAR and CXRS systems (as described below) are invited to contact UKAEA.

Fusion research in the UK is centred on the Culham Science Centre in Oxfordshire. In addition to UKAEA's Mega Amp Spherical Tokamak (MAST) experiment, the centre hosts the world's largest fusion experiment – the Joint European Torus (JET). A wide range of photonic techniques are used for measurements for control of the plasma produced by MAST and JET. Diagnostics systems on ITER are at the concept design stage with installation intended well in advance of plasma commissioning (scheduled for 2016).

What does an ITER diagnostic look like?

The ITER diagnostic systems are grouped in "Port Plugs" (usually several systems per plug). The ports are apertures in the ITER vacuum vessel through which diagnostics, heating systems and remote handling are introduced. The complete plug would be provided to ITER by one Party (even if there are subsystems provided by other Parties). An equatorial port plug with the LIDAR system is shown schematically below:

Equatorial port plug with the LIDAR laser and collection optics (proposed design)

Opportunities for UK industry

1.LIDAR Thomson scattering system for measuring the plasma temperature and density profile in the plasma core

Laser(s) for LIDAR: pulses of ~5 Joules, 100 Hz repetition rate (could be via a cluster of lasers) able to run all day with exceptionally high reliability. Pulse duration ~250 picosecond, wavelengths probably two in 500- 1100nm band (e.g. ~500, ~1000), . Line width a few nm or less, (stray light in time or wavelength has to be at a very low level).

Detectors for 250nm - 1100nm (several bands), depending on the laser chosen. High effective quantum efficiency (target>5%). Response time ~250ps. Gateable with a few nanosecond response time. Streak cameras might be an option.

Mirrors: large metal and dielectric mirrors to relay the plasma light with the same bandwidth as the detectors and lasers.. The metal mirrors (possibly rhodium) may operate at 400°C, in vacuum, possibly using an electrically heated substrate, without outgassing. Some of the dielectric mirrors will also be in vacuum so need to be bakeable to 240°C and operate stably at ~100°C. Subject to plasma erosion/deposition and radiation damage from neutrons and gammas. Plane and curved mirrors with dimensions upward of ~20cm.

Spectrometers: these will probably be polychromators with wide and narrow band filters covering the region ~250nm to 1100nm (depending on the laser).

Remote mirror alignment systems for hostile environments, for example, resistant to thermal expansion of mirror mounts.

A range of test/calibration equipment spanning 250 – 1100nm for precision measurements of mirror reflectivity (80- >98%) and ~250ps- 1ns pulse tests.

2. Charge exchange recombination spectroscopy (CXRS) system to measure the helium (ash) content, and ion temperature and flows in the plasma core.

Mirrors: similar to those for LIDAR above. The first, plasma facing, mirror is likely to be a large (1.7m long) plane mirror. Subsequent mirrors will be of various toroidal curvatures, up to 1m diameter, either multilayer or possibly aluminium coated.

Optical fibres: a very large array of radiation tolerant fibres (over 800, typically 1mm diameter and 200m long) coupling light from a weak source to an array of high etendue spectrometers.

Spectrometers: up to 30, with an etendue of 10 - 6 st.m 2 , and a dispersion ~1 nm/mm. The spectral regions of interest include 468 nm and 529 nm; methods of combining the spectra from these regions in one spectrometer/detector so as to preserve optical efficiency and reduce components are of particular interest.

Detectors: Each spectrometer is foreseen to be fitted with a CCD detector, but the large number of detectors involved means that we are looking for significant cost savings by exploiting common elements of the detectors. Other detector technologies could be of great interest if they can match the quantum efficiency, noise and readout capabilities of present scientific CCD cameras.

Additional ITER information and UKAEA contact details
The EU activity is presently under the European Fusion Development Agreement. The ITER organisation manages the international activity. The UK fusion programme is conducted by UKAEA at Culham, funded by EPSRC and EURATOM. There is also an industry liaison group at Culham (www.fusion-industry.org.uk ). Note: All above specifications are indicative only.

Contact Dan Mistry, UKAEA Fusion and Industry for more details on 01235 466607 and This e-mail address is being protected from spambots. You need JavaScript enabled to view it .