Design and implementation of a full profile sub-cm ruby laser based Thomson scattering system for MAST

Journal Article · Wed Dec 15 00:00:00 EST 2010 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.3511556· OSTI ID:22075440

O'Gorman, T; Mc Carthy, P J; Prunty, S ^[1]; Walsh, M J; Dunstan, M R; Huxford, R B; Naylor, G; Maguet, Emmanuel; Scannell, R; Shibaev, S ^[2]

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1. Department of Physics, University College Cork, Association Euratom-DCU, Cork (Ireland)
2. EURATOM/CCFE Fusion Association, Culham Science Centre, Abingdon, Oxfordshire, OX14 3DB (United Kingdom)

A major upgrade to the ruby Thomson scattering (TS) system has been designed and implemented on the Mega-ampere spherical tokamak (MAST). MAST is equipped with two TS systems, a Nd:YAG laser system and a ruby laser system. Apart from common collection optics each system provides independent measurements of the electron temperature and density profile. This paper focuses on the recent upgrades to the ruby TS system. The upgraded ruby TS system measures 512 points across the major radius of the MAST vessel. The ruby laser can deliver one 10 J 40 ns pulse at 1 Hz or two 5 J pulses separated by 100-800 {mu}s. The Thomson scattered light is collected at F/15 over 1.4 m. This system can resolve small (7 mm) structures at 200 points in both the electron temperature and density channels at high optical contrast; {approx}50% modulated transfer function. The system is fully automated for each MAST discharge and requires little adjustment. The estimated measurement error for a 7 mm radial point is <4% of T{sub e} and <3% of n{sub e} in the range of 40 eV to 2 keV, for a density of n{sub e}=2x10{sup 19} m{sup -3}. The photon statistics at lower density can be increased by binning in the radial direction as desired. A new intensified CCD camera design allows the ruby TS system to take two snapshots separated with a minimum time of 230 {mu}s. This is exploited to measure two density and temperature profiles or to measure the plasma background light.

• OSTI ID: 22075440
• Journal Information: Review of Scientific Instruments, Vol. 81, Issue 12; Other Information: (c) 2010 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0034-6748
• Country of Publication: United States
• Language: English

Related Subjects

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
CAMERAS
CHARGE-COUPLED DEVICES
ELECTRON DENSITY
ELECTRON TEMPERATURE
ERRORS
EV RANGE
KEV RANGE
MAST TOKAMAK
NEODYMIUM LASERS
PHOTONS
PLASMA
PLASMA DIAGNOSTICS
PULSES
RUBY LASERS
STATISTICS
THOMSON SCATTERING
TRANSFER FUNCTIONS
VISIBLE RADIATION