Implementation of a Zero-Field Spin-Echo Option at the Three-Axis Spectrometer {{IN3}} ({{ILL}}, {{Grenoble}}) and First Application for Measurements of Phonon Line Widths in Superfluid {{4He}}

We report on a new zero-field spin-echo spectrometer (ZETA), installed at the thermal three-axis spectrometer IN3 at ILL, Grenoble. In this technique the two long precession solenoids from neutron spin echo are replaced by two pairs of magnetic resonance coils in a zero-field region. This allows easy adaptation of tilted field geometries, necessary for measurements of phonon line widths with meV energy resolution. First test measurements of the roton line width and energy shift as well as line width of the low-Q phonon and in the ``region beyond the roton'' in superfluid 4He are described. The results are in agreement with the literature and show the good operation of ZETA. The implementation of ZETA at the high-flux three-axis spectrometer IN20, foreseen in the near future, will increase the count rate by typically one order of magnitude.     «

We report on a new zero-field spin-echo spectrometer (ZETA), installed at the thermal three-axis spectrometer IN3 at ILL, Grenoble. In this technique the two long precession solenoids from neutron spin echo are replaced by two pairs of magnetic resonance coils in a zero-field region. This allows easy adaptation of tilted field geometries, necessary for measurements of phonon line widths with meV energy resolution. First test measurements of the roton line width and energy shift as well as line w...     »