| 1. |
- Abat, E., et al.
(författare)
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Study of the response of the ATLAS central calorimeter to pions of energies from 3 to 9 GeV
- 2009
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002 .- 1872-9576. ; 607:2, s. 372-386
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Tidskriftsartikel (refereegranskat)abstract
- A fully instrumented slice of the ATLAS central detector was exposed to test beams from the SPS (Super Proton Synchrotron) at CERN in 2004. in this paper, the response of the central calorimeters to pions with energies in the range between 3 and 9 GeV is presented. The linearity and the resolution of the combined calorimetry (electromagnetic and hadronic calorimeters) was measured and compared to the prediction of a detector simulation program using the toolkit Geant 4. (C) 2009 Elsevier B.V. All rights reserved.
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| 2. |
- Apyan, A., et al.
(författare)
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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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| 3. |
- Kiptily, V. G., et al.
(författare)
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Fast ion JET diagnostics : Confinement and losses
- 2008
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Ingår i: BURNING PLASMA DIAGNOSTICS. - : AIP. ; , s. 283-290
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Konferensbidrag (refereegranskat)abstract
- A study of magnetically confined fast ions in tokamaks plays an important role in burning plasma research. To reach ignition and steady burning of a reactor plasma an adequate confinement of energetic ions produced by NBI heating, accelerated with ICRF and born in fusion reactions is essential to provide efficient heating of the bulk plasma. Thus, investigation of the fast ion behaviour is an immediate task for present-day large machines, such as JET, in order to understand the main mechanisms of slowing down, redistribution and losses, and to develop optimal plasma scenarios. Today's JET has an enhanced suite of fast ion diagnostics both of confined and lost ions that enable to significantly contribute to this important area of research. Fast ion populations of p, d, t, 3He and 4He, made with ICRF, NBI, and fusion reactions have been investigated in experiments on JET with sophisticated diagnostics in conventional and shear-reversed plasmas, exploring a wide range of effects. This paper will introduce to the JET fast-ion diagnostic techniques and will give an overview of recent observations. A synergy of the unique diagnostic set was utilised in JET, and studies of the response of fast ions to MHD modes (e.g. tornado modes, sawtooth crashes), fast 3He-ions behaviour in shear-reversed plasmas are impressive examples of that. Some results on fast ion losses in JET experiments with various levels of the toroidal field ripple will be demonstrated.
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| 4. |
- Kiptily, V. G., et al.
(författare)
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Recent progress in fast ion studies on JET
- 2009
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 49:6
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents recent results on fast ion studies on JET. A set of diagnostics for both confined and lost fast ions was employed for investigating the response of fast ions to MHD modes and for studying their behaviour in plasmas with toroidal field ripple and in shear-reversed plasmas. A dependence of the losses on MHD mode amplitude was deduced from the experimental data. A study of various plasma scenarios has shown that a significant redistribution of the fast ions happens during changes in the profile of the safety factor from shear-reversed to monotonic. Significant changes in the losses of ICRH accelerated protons were found to be associated with L-H confinement transitions in plasmas. After an L-H transition, an abrupt decrease in the ICRH proton losses was observed. In plasmas with an internal transport barrier, the loss of ICRH accelerated ions was found to increase as the barrier forms. Further results concerning fast ion losses were obtained during JET experiments in which the magnitude of the TF ripple was varied. The ripple losses of fusion products appear similar to classical losses, and are in agreement with modelling.
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| 5. |
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