Druck-Materie 20b.qxd - JUWEL - Forschungszentrum Jülich

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4. SOLID PHASES OF MESITYLENE-D0 AND THEIR PHONON DENSITY OF STATES Solid phases of mesitylene-D0 can be easily obtained using a proper thermal procedure according to the scheme of phase transformations presented in Figure 5. The structural modifications of solid mesitylene have been identified by their characteristic NPD patterns in the lattice spacing range of 0.5 – 0.7 nm. The characteristic diffraction patterns of the three structural modifications of solid mesitylene, which can be obtained at low temperatures, are displayed in Figure 6. The IINS spectra measured at low temperatures exhibit peculiarities in the dynamics of these structural modifications of solid mesitylene. The difference in harmonic lattice dynamics of phases III and II, as well as the stochastic dynamics of methyl groups in these phases, are displayed in Figure 7. One can see that the QNS wings of phase II at 90K are much broader than those in phase III. This means that the barriers for methyl group rotations in phase II are much lower than in phase III. At higher temperatures, especially above the III – II transition at 91 K, the IINS spectra of phases II and I seem to be quite similar. The temperature dependence of the IINS spectra of phase I is shown in Figure 8. The IINS spectrum of liquid mesitylene at 290 K displayed also in Fig. 8 is almost smooth and shows broad quasi-elastic wings caused by rotational and translational diffusion of molecules in the liquid phase. The QNS wings for solid phase I measured at 220 K are narrower, and probably they are caused only by rotational diffusion of methyl groups. There is no significant difference in the IINS spectra of phase I down to about 100 K. They show a few precursory peaks of internal vibrations of the molecule and still significant quasi-elastic scattering caused by relatively fast reorientations of methyl groups. Quasi-elastic scattering is not observed at 20 K. The IINS spectrum at this temperature reflects the harmonic dynamics of the lattice and internal vibrations of the molecule in the structure of phase I. Normalized Intensity - I(λ)/Φ(λ) [a.u.] 40 30 20 10 0 1,3,5-(CH 3 ) 3 C 6 H 3 T = 20 K Phase I Phase II Phase III 0.35 0.40 0.45 0.50 0.55 d [nm] hkl 0.60 0.65 0.70 108 2Θ = 56.6 o Figure 6. The characteristic NPD spectra of solid phases of mesitylene-D0 measured at 20K.
Intensity of scattered neutrons - I(λ)*10 3 counts/h 12 8 4 0 1,3,5-(CH 3 ) 3 C 6 H 3 phase III phase III phase II phase II 1 2 3 4 5 6 Incident neutron wavelength - λ [A] 109 o T = 90 K T = 20 K Figure 7. Comparison of the IINS spectra of the solid phases II and III of mesitylene-D0 measured at 20K and 90K. Intensity of scattered neutrons - I(λ)*10 3 counts/h 25 20 15 10 5 0 1,3,5-(CH 3 ) 3 C 6 H 3 liquid phase I phase I 1 2 3 4 5 6 Incident neutron wavelength - λ [A] o T = 290 K T = 220 K T = 120 K T = 20 K Figure 8. The IINS spectra of solid phase I at T=20K, 120K and 220K and liquid mesitylene-D0 at T=290K.
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ACoM - 6 6th 6 International Worksh
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Forschungszentrum Jülich GmbH Inst
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Preface These are the Proceedings o
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List of participants, cont’d. Kü
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Pepe M. 43 Petriw S. 43 Picton D.J.
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Experimental background, results an
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• Light water ice as H(H2O) at T
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In Table 2 a survey is given about
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sigma-T in barns/molecule Figure 4.
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2.3 Liquid water Compared to the so
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presented. The corresponding experi
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3.2 Gaseous hydrogen and deuterium
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Rho(Omega) normalised 160 140 120 1
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elatively free and can also suffer
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Figure 16. Heat Capacity for Solid
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o-D2 and p-H2 at 5K for an ucn ener
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Figure 22. UCN Upscattering Rates i
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ho(omega) normalised 40 35 30 25 20
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derived from Walker [52]. The neutr
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Since there is only a small gain of
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7. CALCULATION OF SCATTERING LAW DA
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For the validation of these data se
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[36] Nielsen, M.: Phonons in Solid
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2. THE CASE OF MOLECULAR SOLIDS An
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γ r ( 0) ≅ 2 2 2 T erf e ( ) / 2
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4. PRELIMINARY APPLICATION Solid Me
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[5] Meeting on Moderator Concepts a
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state. Conversely, the monatomic hy
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Note that the equilibrium trihydrog
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para hydrogen system under irradiat
Page 62 and 63: [12] T. E. Fessler and J. W. Blue,
Page 64 and 65: tion of neutron intensities, partic
Page 66 and 67: varied between calculations but the
Page 68 and 69: 5. THE OPTIMISATION OF MULTIPLY GRO
Page 70 and 71: Figure 7. A comparison of time dist
Page 72 and 73: 4.8 cm hydrogen slab in front of a
Page 75 and 76: ACoM - 6 6 th Meeting of the Collab
Page 77 and 78: the moderator is annealed every 12
Page 79 and 80: The method requires two additional
Page 81 and 82: ABSTRACT ACoM - 6 6 th Meeting of t
Page 83 and 84: Heat transfer processes across phas
Page 85 and 86: 3. TWO-PHASE FLOW PATTERN IN THE MO
Page 87 and 88: continuous phase dominating, and a
Page 89 and 90: Also the velocity pattern has chang
Page 91 and 92: Figure 8. Methane pellets concentra
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Page 95 and 96: sample volume and the nominal densi
Page 97 and 98: The results presented in this paper
Page 99: Table 10. Summary of energy transfe
Page 102 and 103: 2. EXPERIMENTAL Methane hydrate was
Page 104 and 105: Figure 4. Energy levels of methane
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Page 108 and 109: phase transitions from phase II to
Page 110 and 111: After melting phase I in the cryost
Page 114 and 115: G(ν) [a.u.] 8 6 4 2 Phase II Phase
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Page 118 and 119: A not quite as perfect cold spectru
Page 120 and 121: 2.2 Inelastic neutron scattering Th
Page 122 and 123: Figure 4. Inelastic spectra at the
Page 124 and 125: 3.2 Moderator performance The resul
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Page 128 and 129: Figure 2. The methane pelletizer, m
Page 130 and 131: Figure 5. The cryogenic hopper fill
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Page 134 and 135: ture
Page 136 and 137: The charging device scheme could be
Page 138 and 139: Table 1. Data of irradiation of met
Page 140 and 141: 5. METHODS OF PROCESSING OF RAW EXP
Page 142 and 143: of radicals, that is, before a burp
Page 144 and 145: 6.2 Condition for thermally stimula
Page 146 and 147: Table 4. Estimated values of an ene
Page 148 and 149: • Nine spontaneous burps were obs
Page 150 and 151: APPENDIX Some useful relations and
Page 152 and 153: APPENDIX. Graphs of burps. 148
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Page 160 and 161: 2. EXPERIMENTAL SETUP Fig. 1 will g
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All these parameters are kept const
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4. CONCLUSIONS We demonstrated that
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JESSICA (Juelich Experimental Spall
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The moderator system consists of th
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to change the temperatures and to p
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168
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supplied from the high pressure bom
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10 9 10 8 10 7 10 6 Para35%[Experim
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174
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2. TIME OF FLIGHT SPECTRA AND ENERG
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When applying this transformation t
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data were analyzed in more detail.
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182
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First of all, we should conclude th
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The equation (a) may also describe
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Even at h=0.01 mm which is too smal
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model and some consequences of its
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methane and 0.7-1.5% for water ice
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case: the sample of infinite size.
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Phase Diagram of the CH4-H20 system
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Reaction Chamber for Hydrate Produc
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Analysis: X-ray diffraction pattern
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Comparison with non-hydrate forming
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Mechanical Tests: Apparatus 220
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Morphology of Indium Jacket 222
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Schriften des Forschungszentrums J
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Schriften des Forschungszentrums J
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Druck-Materie 20b.qxd - JUWEL - Forschungszentrum Jülich

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