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

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), Forschungszentrum Jülich 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
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