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

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Figure 4. Inelastic spectra at the lowest energy transfers from THF clathrate at T = 2 K and for three scattering angles (E0 = 7 meV, δE = 0.4 meV; Qo = 1.5; 1.9 and 2.9 Å -1 resp.). 3.1.3 Hexagonal ice The results for hexagonal ice, which is usually obtained by cooling down light water slowly to cryogenic temperatures, are shown in Figures 5 and 6 for different energy transfer regimes, respectively, but at a temperature of 2 K in both cases. To our knowledge there has been no report in the literature about an observation of these low energy modes in ice. The physical origin of these excitations is not understood yet. Figure 5. Inelastic spectra from ice at T = 2 K and for two scattering angles (E0 = 41 meV, δE = 4 meV; Qo = 4.8 and 7.2 Å -1 resp.). Note that the line at 10 meV observed with THF clathrate is missing in ice (comp. Fig. 3). 118
Figure 6. Inelastic spectra from ice at T = 2 K and for two scattering angles (E0 = 7 meV, δE = 0.4 meV; Qo = 1.9 and 2.9 Å -1 resp.). 3.1.4 Mesitylene It has been observed that mesitylene forms different low temperature crystalline modifications depending on the rate of cooling [11]. The crystalline phase obtained by slowly cooling down (at a rate of 1 to 2 K per minute only) is supposed to form a structure with high barriers against free rotations of the methyl groups. This assumption should be visible in different differential inelastic neutron cross sections. Therefore we performed scattering experiments from a quenched mesitylene specimen as well as one, which was subject to a particular cooling and annealing treatment suggested elsewhere [8]. The results are shown in Figure 7. Figure 7. Inelastic spectra from mesitylene at T = 2 K. Circles denote data taken with the quenched sample, and crosses taken with the sample annealed for 8 hours just below the melting point and cooled down slowly afterwards. (E0 = 26 meV, δE = 2.1 meV; Qo = 3.0 and 5.8 Å -1 , respectively). 119
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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
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[12] T. E. Fessler and J. W. Blue,
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tion of neutron intensities, partic
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varied between calculations but the
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5. THE OPTIMISATION OF MULTIPLY GRO
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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
Page 93 and 94: ACoM - 6 6 th Meeting of the Collab
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 112 and 113: 4. SOLID PHASES OF MESITYLENE-D0 AN
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 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
Page 162 and 163: All these parameters are kept const
Page 164 and 165: 4. CONCLUSIONS We demonstrated that
Page 166 and 167: JESSICA (Juelich Experimental Spall
Page 168 and 169: The moderator system consists of th
Page 170 and 171: 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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