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- Giacomelli, Luca, 1973-
(författare)
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Development of Neutron Emission Spectroscopy Instrumentation for Deuterium and Deuterium-Tritium Fusion Plasmas at JET
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The study of high power fusion plasmas at the JET tokamak has been further enhanced through the development of instrumentation for neutron emission spectroscopy (NES) measurements. This has involved the upgrade of the magnetic proton recoil (MPR) spectrometer used for deuterium-tritium plasmas earlier so that the MPRu can now be also employed for deuterium (D) plasmas. A neutron time-of-flight (TOF) spectrometer designed for optimized rate (TOFOR) has been constructed and put into operation. The MPRu and TOFOR spectrometers were carried out as part of the JET enhanced performance program and represent the most advanced instrumentation for NES diagnosis of both D and DT tokamak plasmas setting a central platform for R&D direct to the next step in fusion research to be carried out with ITER.The MPRu work presented in this thesis concerns the development of a new focal plane detector based on the phoswich scintillator technique. The main objective of this sub-project was to increase the signal-to-background ratio to permit measurement of the 2.5-MeV neutron emission from d+d-->3He+n reactions and, hence, allow NES diagnosis of D plasmas. The objective was achieved as demonstrated in preliminary measurements at JET.The development of TOFOR from concept to construction is presented in the thesis including, in particular, the commissioning of the instrument at JET. The objective of the TOFOR project was to achieve the same high performance in the NES diagnosis of D plasmas as had earlier been demonstrated by the MPR for DT plasmas. TOFOR has been used in the first plasma physics experiments reported in this thesis. These demonstrate that the performance objectives have been achieved as tested, in particular, in the observation of auxiliary heating effects on velocity distribution of the deuterium population.
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- Gorini, Giuseppe, et al.
(författare)
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Neutron Emission from Beam-Injected Fast Tritons in JET Plasmas with Reversed or Monotonic Magnetic Shear.
- 2004
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Ingår i: 31st EPS Conference on Plasma Physics. ; , s. 4-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The neutron emission from fast tritons in plasmas with different magnetic shearconfigurations has been investigated in a dedicated experiment on JET. Short pulses ofneutral beam injection were used to deposit fast tritons in deuterium plasmas. By comparingthe measured neutron yield with predictions based on DT reaction calculations, fast tritonlosses can be assessed. The latter are expected to be very low according to neoclassicalpredictions based on Fokker-Planck simulation [1]. Much larger “anomalous” beam-ionlosses (up to 40%) have been reported in TFTR experiments for plasma conditions withreversed magnetic shear [2]. The TFTR experiments indicated an excess DT rate in thesimulation and, to a lesser extent, in the DD rate and plasma stored energy. This wasinterpreted as anomalous beam-ion loss associated with reverse shear due to an unidentifiedloss mechanism. Evidence of a similar effect was searched for in the JET experimentsreported in this paper.
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- Gorini, G, et al.
(författare)
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Proposed Neutron Emission Spectroscopy Diagnostics of Energetic Deutrons in JET rium Plasmas
- 2001
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Ingår i: 7th IAEA TCM on Energetic Particles.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The DT experimental campaign on JET (1997) represented a major step forward for neutron emissionspectroscopy (NES) diagnostics thanks to the high count rate measurements obtained with themagnetic proton recoil (MPR) neutron spectrometer in high fusion yield plasmas [1]. NESmeasurements were made on JET DT plasmas for different heating conditions including thosegenerating energetic deuterons either directly through NB injection, or through ICRH accelerationusing the (D)T minority scheme [2]. A multiple-component model has been developed for analysisof dt neutron spectra that is based on a simplified description of fuel ion velocity distributions fordifferent heating conditions [3,4]. The same model is used here for projections of NES spectra fromJET deuterium plasmas using the dt results as input. This is done on the basis of a system of twocomplementary NES instruments, the TOFOR (Time of Flight - Optimized Rate) [5] and MPRu(Magnetic Proton Recoil Upgrade) spectrometers that are presently proposed for installation onJET [6]. Both spectrometers would record neutron spectra in D plasmas but for different viewinglines. TOFOR would have a “vertical” view, i.e. at an angle of 90° relative to the toroidal magneticfield. This is the same viewing line used for some of the previous dd NES measurements on JET[7]. MPRu would have a “tangential” view, i.e. horizontal (on the equatorial plane) at an angle of47° relative to the toroidal magnetic field and opposite to the beam injection direction. This is thesame viewing line used for the 1997 dt measurements using the magnetic proton recoil (MPR)spectrometer.Projections of dd neutron spectra under the assumptions above are used here for an assessmentof the performance and requirements of NES as a diagnostic of energetic deuterons in JET.
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