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

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to change the temperatures and to provide moderator temperatures up to 90 K. Figure 6 shows the measured temperatures at the bottom and at the top of the moderator vessel first without heating the top plate of the cold head, secondly by heating the cold head more and more. All the time the temperature difference between the top and the bottom of the vessel was about 4.0 K. Figure 6: Temperatures at the moderator vessel 4. CONCLUSION It has been demonstrated which engineering efforts were necessary to install the cryogenic moderator system for JESSICA, a full scale model of the target-reflector-moderator system for a large spallation source. The cryogenic moderator system has been installed and improved. The moderator system can be operated with different moderator materials like water, ice, methane hydrate, methane, hydrogen, and a combination of different moderator 166
materials. This is possible because the moderator system can be operated both as a closed system and as an open one, where a liquid or solid medium can be filled into the moderator vessel under helium atmosphere. So far, experiments at JESSICA have been performed with water, ice and methane hydrate as moderator material. The measured energy spectra of these moderator materials are documented in [4] and [5]. Additional experiments at JESSICA will be made with moderator material which has to be condensed from storage containers into the moderator vessel. These experiments with hydrogen and methane will take place in 2003. ACKNOWLEDGMENTS The authors are grateful to the whole JESSICA collaboration. The staff members of the Central Department of Technology are acknowledged for building up JESSICA. In particular F.J.Bongartz and M.Dick are acknowledged for their good ideas in realizing difficult technical details of the cold moderator. Moreover, we acknowledge the work in preparing the technology of the cold moderator system by H.Barnert-Wiemer and we thank N.Paul for the help in building up JESSICA at the COSY accelerator. REFERENCES [1] Inoue, K. et al., Atomic Energy Soc. Japan, 21 (1979) 865, 1979 [2] Barnert-Wiemer, H., Conceptual Design of a Cold Methane Moderator System for the European Spallation Source (ESS), <strong>Forschungszentrum</strong> <strong>Jülich</strong> GmbH, Germany, Juel- 3067, ISSN 0944-2952, 2002 [3] Tietze-Jaensch, H. et al., JESSICA, the ESS-like target/reflector mock-up and the cold moderator test facility, ICANS-XV, 15 th Meeting of the International Collaboration on Advanced Neutron Sources, Nov. 6-9 2000, Tsukuba, Japan [4] Pohl, Ch. et al., The JESSICA Experiment – Part II, Results from the JESSICA- Experiment, ACoM-6, 6 th Meeting of the Collaboration on Advanced Cold Moderators, Sept. 11-13 2002, Juelich, Germany [5] Nuenighoff, K. et al, The JESSICA Experiment – Part I, Improvements of the JESSICA- Experiment, ACoM-6, 6 th Meeting of the Collaboration on Advanced Cold Moderators, Sept. 11-13 2002, Juelich, Germany 167
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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
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4.8 cm hydrogen slab in front of a
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ACoM - 6 6 th Meeting of the Collab
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the moderator is annealed every 12
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The method requires two additional
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ABSTRACT ACoM - 6 6 th Meeting of t
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Heat transfer processes across phas
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3. TWO-PHASE FLOW PATTERN IN THE MO
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continuous phase dominating, and a
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Also the velocity pattern has chang
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Figure 8. Methane pellets concentra
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ACoM - 6 6 th Meeting of the Collab
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sample volume and the nominal densi
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The results presented in this paper
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Table 10. Summary of energy transfe
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2. EXPERIMENTAL Methane hydrate was
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Figure 4. Energy levels of methane
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102
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phase transitions from phase II to
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After melting phase I in the cryost
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4. SOLID PHASES OF MESITYLENE-D0 AN
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G(ν) [a.u.] 8 6 4 2 Phase II Phase
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112
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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
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
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Page 174 and 175: supplied from the high pressure bom
Page 176 and 177: 10 9 10 8 10 7 10 6 Para35%[Experim
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Page 180 and 181: 2. TIME OF FLIGHT SPECTRA AND ENERG
Page 182 and 183: When applying this transformation t
Page 184 and 185: data were analyzed in more detail.
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Page 188 and 189: First of all, we should conclude th
Page 190 and 191: The equation (a) may also describe
Page 192 and 193: Even at h=0.01 mm which is too smal
Page 194 and 195: model and some consequences of its
Page 196 and 197: methane and 0.7-1.5% for water ice
Page 198 and 199: case: the sample of infinite size.
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Page 216 and 217: Phase Diagram of the CH4-H20 system
Page 218 and 219: 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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