| 1. |
- Abel, I, et al.
(author)
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Overview of the JET results with the ITER-like wall
- 2013
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In: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 53:10, s. 104002-
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Journal article (peer-reviewed)abstract
- Following the completion in May 2011 of the shutdown for the installation of the beryllium wall and the tungsten divertor, the first set of JET campaigns have addressed the investigation of the retention properties and the development of operational scenarios with the new plasma-facing materials. The large reduction in the carbon content (more than a factor ten) led to a much lower Z(eff) (1.2-1.4) during L- and H-mode plasmas, and radiation during the burn-through phase of the plasma initiation with the consequence that breakdown failures are almost absent. Gas balance experiments have shown that the fuel retention rate with the new wall is substantially reduced with respect to the C wall. The re-establishment of the baseline H-mode and hybrid scenarios compatible with the new wall has required an optimization of the control of metallic impurity sources and heat loads. Stable type-I ELMy H-mode regimes with H-98,H-y2 close to 1 and beta(N) similar to 1.6 have been achieved using gas injection. ELM frequency is a key factor for the control of the metallic impurity accumulation. Pedestal temperatures tend to be lower with the new wall, leading to reduced confinement, but nitrogen seeding restores high pedestal temperatures and confinement. Compared with the carbon wall, major disruptions with the new wall show a lower radiated power and a slower current quench. The higher heat loads on Be wall plasma-facing components due to lower radiation made the routine use of massive gas injection for disruption mitigation essential.
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| 2. |
- Romanelli, F, et al.
(author)
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Overview of the JET results
- 2011
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In: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 51:9
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Journal article (peer-reviewed)abstract
- Since the last IAEA Conference JET has been in operation for one year with a programmatic focus on the qualification of ITER operating scenarios, the consolidation of ITER design choices and preparation for plasma operation with the ITER-like wall presently being installed in JET. Good progress has been achieved, including stationary ELMy H-mode operation at 4.5 MA. The high confinement hybrid scenario has been extended to high triangularity, lower ρ*and to pulse lengths comparable to the resistive time. The steady-state scenario has also been extended to lower ρ*and ν*and optimized to simultaneously achieve, under stationary conditions, ITER-like values of all other relevant normalized parameters. A dedicated helium campaign has allowed key aspects of plasma control and H-mode operation for the ITER non-activated phase to be evaluated. Effective sawtooth control by fast ions has been demonstrated with3He minority ICRH, a scenario with negligible minority current drive. Edge localized mode (ELM) control studies using external n = 1 and n = 2 perturbation fields have found a resonance effect in ELM frequency for specific q95values. Complete ELM suppression has, however, not been observed, even with an edge Chirikov parameter larger than 1. Pellet ELM pacing has been demonstrated and the minimum pellet size needed to trigger an ELM has been estimated. For both natural and mitigated ELMs a broadening of the divertor ELM-wetted area with increasing ELM size has been found. In disruption studies with massive gas injection up to 50% of the thermal energy could be radiated before, and 20% during, the thermal quench. Halo currents could be reduced by 60% and, using argon/deuterium and neon/deuterium gas mixtures, runaway electron generation could be avoided. Most objectives of the ITER-like ICRH antenna have been demonstrated; matching with closely packed straps, ELM resilience, scattering matrix arc detection and operation at high power density (6.2 MW m-2) and antenna strap voltages (42 kV). Coupling measurements are in very good agreement with TOPICA modelling. © 2011 IAEA, Vienna.
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| 3. |
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| 4. |
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| 5. |
- Frenje, J, et al.
(author)
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Neutron emission Doppler-shift measurements in deuterium-tritium plasmas
- 1999
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In: REVIEW OF SCIENTIFIC INSTRUMENTS. - 0034-6748. ; 70:1, s. 1176-1180
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Journal article (other academic/artistic)abstract
- Spectrometry of the neutron emission is discussed as a probe of the fuel ion velocity distribution in tokamak plasmas where the instrumental energy calibration allows determination of Doppler shifts on an absolute scale or relative to the emission of ther
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| 6. |
- Frenje, J, et al.
(author)
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Neutron spectrometry of triton burn-up in plasmas of deuterium
- 1998
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In: Plasma Physics and Controlled Fusion. ; 40, s. 1211-1219
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Journal article (peer-reviewed)abstract
- The first measurement of the energy distribution of the neutron emission from the nuclear burn-up of tritons produced at 1 MeV in d + d --> t+p reactions is reported. The results refer to deuterium plasmas with a strongly pulsed neutron production attaine
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| 7. |
- Hjalmarsson, A, et al.
(author)
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Neutron time-of-flight spectrometer for high rate diagnosis of deuterium plasmas
- 2001
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In: REVIEW OF SCIENTIFIC INSTRUMENTS. - : AMER INST PHYSICS. - 0034-6748. ; 72:1, s. 841-844
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Journal article (peer-reviewed)abstract
- The new concept for the design of a neutron time of flight spectrometer operating at high rates of events has been studied based on instrumental modeling and neutron transport calculations. The aim is to find an optimized design for an instrument that can
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| 8. |
- Kallne, J, et al.
(author)
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New neutron diagnostics with the magnetic proton recoil spectrometer
- 1999
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In: REVIEW OF SCIENTIFIC INSTRUMENTS. - 0034-6748. ; 70:1, s. 1181-1184
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Journal article (other academic/artistic)abstract
- The first magnetic proton recoil type neutron spectrometer has been put to use for diagnosing tokamak plasmas of high neutron yield rates (the range Y-n = 10(15)- 6 x 10(18) n/s). The spectrometer principles along with the diagnostic installation are pres
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| 9. |
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| 10. |
- Tardocchi, M, et al.
(author)
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Neutron spectrometry of radio-frequency heated deuterium-tritium plasmas
- 1999
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In: REVIEW OF SCIENTIFIC INSTRUMENTS. - 0034-6748. ; 70:1, s. 1171-1175
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Journal article (peer-reviewed)abstract
- Spectrometry of the neutron emission has been used to probe the nonthermal features of the fuel ion velocity distributions in tokamak plasmas, especially, those arising from auxiliary heating. The first time resolved measurements are reported from the use
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| 11. |
- Antozzi, P, et al.
(author)
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Neutron wall emission in tokamaks and plasma diagnostics
- 1996
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In: NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT. - : ELSEVIER SCIENCE BV. - 0168-9002. ; 368:2, s. 457-472
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Journal article (peer-reviewed)abstract
- The wall emission (WE) background accompanying observations of fusion plasma neutrons is a limiting factor in high accuracy neutron diagnostics. It is an important issue to solve for envisaged burning plasma experiments such as with ITER. This work repres
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| 12. |
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| 13. |
- Ballabio, L, et al.
(author)
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alpha-particle knock-on signature in the neutron emission of DT plasmas
- 1997
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In: PHYSICAL REVIEW E. - : AMER INST PHYSICS. - 1063-651X. ; 55:3, s. 3358-3368
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Journal article (other academic/artistic)abstract
- The fast alpha-particle kinetic effects in fusion plasmas of deuterium and tritium are studied in the perspective that they can give rise to minority populations of fast fuel ions. The resulting modification of the neutron emission spectrum is computed fo
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| 14. |
- Ballabio, L, et al.
(author)
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Energy spectrum of thermonuclear neutrons
- 1997
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In: REVIEW OF SCIENTIFIC INSTRUMENTS. - : AMER INST PHYSICS. - 0034-6748. ; 68:1, s. 585-588
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Journal article (other academic/artistic)abstract
- The neutron energy spectrum from d+t and d+d reactions in a thermonuclear fusion plasma is investigated with the help of a combination of analytical and numerical (Monte Carlo) methods. The energy moments of the neutron spectrum are analytically determine
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| 15. |
- Ballabio, L, et al.
(author)
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Relativistic calculation of fusion product spectra for thermonuclear plasmas
- 1998
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In: NUCLEAR FUSION. - : INT ATOMIC ENERGY AGENCY. - 0029-5515. ; 38:11, s. 1723-1735
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Journal article (other academic/artistic)abstract
- The first three moments of the energy distributions of products from fusion reactions in thermonuclear plasmas with Maxwellian ion velocity distributions are determined analytically. Relativistic kinematics is used allowing the desired accuracy to be reac
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| 16. |
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| 17. |
- Gorini, G, et al.
(author)
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Neutron emission spectrum from anisotropic DT plasmas
- 1999
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In: REVIEW OF SCIENTIFIC INSTRUMENTS. - : AMER INST PHYSICS. - 0034-6748. ; 70:1, s. 1209-1212
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Journal article (other academic/artistic)abstract
- The diagnostic information from fusion neutron energy spectra under anisotropic plasma conditions is investigated analytically and numerically. The ion anisotropy is parametrized by a Maxwellian velocity distribution with different temperatures along (T-p
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| 18. |
- Gorini, G, et al.
(author)
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Neutron spectrometry diagnostic of triton burn-up in deuterium fusion plasmas
- 1997
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In: PLASMA PHYSICS AND CONTROLLED FUSION. - : IOP PUBLISHING LTD. - 0741-3335. ; 39:1, s. 61-71
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Journal article (other academic/artistic)abstract
- Spectrometry measurements of neutrons from triton bum-up can provide information on fast ion confinement in deuterium plasmas. This study concerns the relationship between the burn-up neutron spectrum and the triton slowing-down distribution under classic
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| 19. |
- Gorini, G, et al.
(author)
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Neutron spectrometry for plasma rotation
- 1997
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In: REVIEW OF SCIENTIFIC INSTRUMENTS. - : AMER INST PHYSICS. - 0034-6748. ; 68:1, s. 561-564
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Journal article (other academic/artistic)abstract
- The principles of neutron spectrometry for determination of the toroidal rotation velocity (V-t) of the plasma in tokamaks are discussed. Comparison is made with photon spectroscopy which shows that neutron spectroscopy can be used as a rotation diagnosti
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| 20. |
- Gorini, G., et al.
(author)
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Nuclear scattering effects on the neutron emission in fusion plasmas
- 2008
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In: Few-body systems. - : Springer Science and Business Media LLC. - 0177-7963 .- 1432-5411. ; 44:1-4, s. 57-60
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Journal article (peer-reviewed)abstract
- Ion reactions and elastic scatterings in fusion plasmas of H and He nuclides are discussed as they can be observed in the neutron emission spectrum (NES). New calculations are presented on radio-frequency driven multi-step processes in (HeD)-He-3 plasmas involving knock-on scattering whose relative importance is discussed besides use for new plasma studies.
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| 21. |
- Henriksson, H, et al.
(author)
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Neutron emission study of DT plasmas heated with tritium neutral beams
- 2001
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In: REVIEW OF SCIENTIFIC INSTRUMENTS. - : AMER INST PHYSICS. - 0034-6748. ; 72:1, s. 832-835
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Journal article (peer-reviewed)abstract
- The neutron emission energy spectrum from deuterium-tritium fusion reactions has been measured in experiments carried out at the Joint European Torus for plasmas heated with high power neutral beam (NB) injection of tritium beams at E-b approximate to 150
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| 22. |
- Kallne, J, et al.
(author)
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Feasibility of neutron spectrometry diagnostic for the fuel ion density in DT tokamak plasmas
- 1997
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In: REVIEW OF SCIENTIFIC INSTRUMENTS. - : AMER INST PHYSICS. - 0034-6748. ; 68:1, s. 581-584
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Journal article (other academic/artistic)abstract
- The neutron wall emission (WE) background is a crucial element of neutron spectrometry as a fuel density diagnostic for burning deuterium-tritium fusion plasmas in tokamaks. WE spectra have been studied based on MCNP neutron transport calculations applied
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| 23. |
- Ronchi, Emanuele, et al.
(author)
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A bipolar LED drive technique for high performance, stability and power in the nanosecond time scale
- 2009
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In: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 599:2-3, s. 243-247
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Journal article (peer-reviewed)abstract
- Pulsed light sources are often used to monitor the stability of light detectors such as photomultiplier tubes. Light emitting diodes (LEDs) are suitable for this due to their high specific light yield. While pulsed operation in the region of [mu]s is generally accessible with most LEDs and drivers, the ns time scale often represents a technical challenge. This paper describes a technique of bipolar LED drive that can produce light pulses of a few ns at high stability, reliability and power. The driver also offers control over the properties of the light pulse produced such as shape, intensity and repetition rate. This approach has been studied in 2003 and implemented in 2004 for two fusion neutron spectrometers at the Joint European Torus (JET) namely the Magnetic Proton Recoil upgrade (MPRu) and the Time Of Flight Optimized for Rate (TOFOR). A driver has been manufactured and connected to the scintillation detectors of each spectrometer through an optical fiber distribution network. Both MPRu and TOFOR have been successfully relying on this system for calibration and performance monitoring for several years, confirming the long-term stability and reliability of this technique.
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| 24. |
- Tardocchi, M, et al.
(author)
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Time resolved neutron emission spectroscopy of DT plasmas with ion cyclotron resonance heating
- 2001
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In: REVIEW OF SCIENTIFIC INSTRUMENTS. - : AMER INST PHYSICS. - 0034-6748. ; 72:1, s. 836-840
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Journal article (peer-reviewed)abstract
- The energy spectrum of the DT neutron emission was measured in experiments carried out at JET for plasmas of deuterium-tritium heated with different ion cyclotron resonance heating (ICRH) schemes. The spectrum was measured with the magnetic proton recoil
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