| 591. |
- Antozzi, P, et al.
(författare)
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Neutron wall emission in tokamaks and plasma diagnostics
- 1996
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Ingår i: 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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Tidskriftsartikel (refereegranskat)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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| 592. |
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| 593. |
- Apyan, A., et al.
(författare)
-
Coherent bremsstrahlung, coherent pair production, birefringence, and polarimetry in the 20-170 GeV energy range using aligned crystals
- 2008
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Ingår i: Physical Review Special Topics - Accelerators and Beams. - 1098-4402. ; 11:4, s. 041001-
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Tidskriftsartikel (refereegranskat)abstract
- The processes of coherent bremsstrahlung (CB) and coherent pair production (CPP) based on aligned crystal targets have been studied in the energy range 20-170 GeV. The experimental arrangement allowed for measurements of single photon properties of these phenomena including their polarization dependences. This is significant as the theoretical description of CB and CPP is an area of active debate and development. With the approach used in this paper, both the measured cross sections and polarization observables are predicted very well. This indicates a proper understanding of CB and CPP up to energies of 170 GeV. Birefringence in CPP on aligned crystals is applied to determine the polarization parameters in our measurements. New technologies for high-energy photon beam optics including phase plates and polarimeters for linear and circular polarization are demonstrated in this experiment. Coherent bremsstrahlung for the strings-on-strings (SOS) orientation yields a larger enhancement for hard photons than CB for the channeling orientations of the crystal. Our measurements and our calculations indicate low photon polarizations for the high-energy SOS photons.
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| 594. |
- Ballabio, L, et al.
(författare)
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alpha-particle knock-on signature in the neutron emission of DT plasmas
- 1997
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Ingår i: PHYSICAL REVIEW E. - : AMER INST PHYSICS. - 1063-651X. ; 55:3, s. 3358-3368
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)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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| 595. |
- Ballabio, L, et al.
(författare)
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Energy spectrum of thermonuclear neutrons
- 1997
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Ingår i: REVIEW OF SCIENTIFIC INSTRUMENTS. - : AMER INST PHYSICS. - 0034-6748. ; 68:1, s. 585-588
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)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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| 596. |
- Ballabio, L, et al.
(författare)
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Relativistic calculation of fusion product spectra for thermonuclear plasmas
- 1998
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Ingår i: NUCLEAR FUSION. - : INT ATOMIC ENERGY AGENCY. - 0029-5515. ; 38:11, s. 1723-1735
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)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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| 597. |
- Cazzaniga, C., et al.
(författare)
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Thin YAP:Ce and LaBr3:Ce scintillators as proton detectors of a thin-film proton recoil neutron spectrometer for fusion and spallation sources applications
- 2014
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 751, s. 19-22
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Tidskriftsartikel (refereegranskat)abstract
- Two thin inorganic scintillators based on YAP and LaBr3 crystals (1 in, diameter x 0.1 in, height) have been used for proton measurements at the Uppsala tandem accelerator in the energy range 4-8 MeV. Measurements show a comparable good energy resolution for the two detectors, better than 2% (FWHM) for 8 MeV protons, which compares to 3.8% (LaBr3) and 3.7% (YAP) obtained at the 1.3 MeV peak of a Co-60 gamma-ray source. The main advantages of these crystals are a fast scintillation time (less than 30 ns), an excellent light yield and the capability to operate in large neutron background, which make them ideal candidates as proton detectors of a thin-film proton recoil neutron spectrometer for application on fusion experiments and fast neutron spallation sources.
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| 598. |
- Eriksson, Jacob, et al.
(författare)
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Dual sightline measurements of MeV range deuterons with neutron and gamma-ray spectroscopy at JET
- 2015
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Ingår i: Nuclear Fusion. - : Institute of Physics Publishing (IOPP). - 0029-5515 .- 1741-4326. ; 55:12
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Tidskriftsartikel (refereegranskat)abstract
- Observations made in a JET experiment aimed at accelerating deuterons to the MeV range by third harmonic radio-frequency (RF) heating coupled into a deuterium beam are reported. Measurements are based on a set of advanced neutron and gamma-ray spectrometers that, for the first time, observe the plasma simultaneously along vertical and oblique lines of sight. Parameters of the fast ion energy distribution, such as the high energy cut-off of the deuteron distribution function and the RF coupling constant, are determined from data within a uniform analysis framework for neutron and gamma-ray spectroscopy based on a one-dimensional model and by a consistency check among the individual measurement techniques. A systematic difference is seen between the two lines of sight and is interpreted to originate from the sensitivity of the oblique detectors to the pitch-angle structure of the distribution around the resonance, which is not correctly portrayed within the adopted one dimensional model. A framework to calculate neutron and gamma-ray emission from a spatially resolved, two-dimensional deuteron distribution specified by energy/pitch is thus developed and used for a first comparison with predictions from ab initio models of RF heating at multiple harmonics. The results presented in this paper are of relevance for the development of advanced diagnostic techniques for MeV range ions in high performance fusion plasmas, with applications to the experimental validation of RF heating codes and, more generally, to studies of the energy distribution of ions in the MeV range in high performance deuterium and deuterium-tritium plasmas.
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| 599. |
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| 600. |
- Gatu Johnson, Maria, et al.
(författare)
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The 2.5-MeV neutron time-of-flight spectrometer TOFOR for experiments at JET
- 2008
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 591:2, s. 417-430
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Tidskriftsartikel (refereegranskat)abstract
- A time-of-flight (TOF) spectrometer for measurement of the 2.5-MeV neutron emission from fusion plasmas has been developed and put into use at the JET tokamak. It has been optimized for operation at high rates (TOFOR) for the purpose of performing advanced neutron emission spectroscopy (NES) diagnosis of deuterium plasmas with a focus on the fuel ion motional states for different auxiliary heating scenarios. This requires operation over a large dynamic range, including high rates of > 100 kHz with a maximum value of 0.5 MHz for the TOFOR design. This paper describes the design principles and their technical realization. The performance is illustrated with recent neutron TOF spectra recorded for plasmas subjected to different heating scenarios. A true event count rate of 39 kHz has been achieved at about a tenth of the expected neutron yield limit of JET, giving a projected maximum of 400 kHz at peak JET plasma yield. This means that the count rate capability for NES diagnosis of D plasmas has been improved more than an order of magnitude. Another important performance factor is the spectrometer bandwidth, where data have been acquired and analyzed successfully with a response function for neutrons over the energy range 1 to > 5 MeV. The implications of instrumental advancement represented by TOFOR are discussed.
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