Druck-Materie 20b.qxd - JUWEL - Forschungszentrum Jülich
Druck-Materie 20b.qxd - JUWEL - Forschungszentrum Jülich
Druck-Materie 20b.qxd - JUWEL - Forschungszentrum Jülich
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etween 4 . 10 -3 eV and 2 . 10 -1 eV the methane-hydrate moderator is inferior to an ice<br />
moderator. We like to remark, that the shown energy spectra are only normalized to the<br />
number of incident protons and the active detector area, but neither to the hydrogen density<br />
nor to the mass density.<br />
5. CONCLUSION<br />
In this article the latest results of the JESSICA experiment were presented. We measured<br />
the time of flight spectra for water and ice at different temperatures. From the time of<br />
flight spectra the energy spectra were derived. In the future we will compare the data with<br />
Monte-Carlo simulations using new neutron scattering kernels [7]. First measurements with a<br />
methane-hydrate moderator delivered promising results but have to be confirmed with further<br />
measurements. Especially the background effects will be studied in more detail using a neutron<br />
generator. The experimental investigation of the wavelength dependent time structure of<br />
the neutron pulses will be performed during the upcoming beam time.<br />
REFERENCES<br />
[1] ESS Vol.III, The ESS Technical Study, ISBN 090-237-6-659, November 1996<br />
[2] K.Nünighoff et al., Improvements of the JESSICA experiment, this conference<br />
[3] K.Inoue et al., Slow Neutron Spectra in Cold Moderators, Journal of Nuclear Science<br />
and Technology 11[5] (1974) 228<br />
[4] K.Inoue et al., Atomic Energy Society Japan 21 (1979) 865<br />
[5] A.W.McReynolds and W.L.Whittemore, Inelastic Scattering of Neutrons from<br />
Very Cold Materials, Inelastic Scattering of Neutrons in Solids and Liquids,<br />
IAEA S33-35 (1961) 421<br />
[6] W.L.Whittemore and A.W.McReynolds, Differential Neutron Thermalization,<br />
General Atomic Annual Summary Report GA-2503, October 20, 1961<br />
[7] W.Bernnat et al., Scattering kernels of cryogenic media; this conference<br />
181