T-REX
The Time-of-flight Reciprocal space Explorer (T-REX) is under construction at the European Spallation Source (ESS) as an in-kind contribution led by Forschungszentrum Jülich (Germany) in collaboration with Consiglio Nazionale delle Ricerche (CNR) / Università degli Studi di Perugia (Italy). The project will be completed in 2027 with the end of cold commissioning.
T-REX is set to take its place as a world-class ESS direct geometry chopper spectrometer, used to measure wide energy transfer with good wave vector resolution, using polarized or non-polarized neutrons and polarization analysis. In particular, polarized neutrons will enable the separation of the magnetic contributions from nuclear scattering and the analysis of polarization and eigenvectors of magnetic excitations. Of particular importance for hydrogen-containing samples in energy research, soft matter and life sciences is the ability to separatecoherent and nuclear spin incoherent scattering.
The scientific mission of T-REX is mainly the study of dynamics in single crystals showing magnetic properties, which require the exploration of the energy range from several tenths of μeV, for the determination of small energy gaps, to several hundreds of meV, for studies of, for example, excitations in the parent compounds of high Tc superconductors or excitations into the Stoner continuum. Therefore, the range of incident neutron energy is selectable from 2 meV to 160 meV thanks to the bi-spectral extraction system enabling the use of neutrons generated at the thermal as well as the cold moderator of the ESS.
The design of T-REX features XYZ neutron spin polarization analysis. Thermal neutron polarization is achieved with the SEOP setup [1], whereas cold neutrons utilize a V-cavity polariser. Neutron spin analysis in XYZ is performed with the magic PASTIS setup [2], already manufactured for the TOPAS project. Specific investigations of high quality 3He cells are required [3], to achieve a long decay time of the polarization of the gas, which is a crucial for experimental investigations.
The chopper system [4] has been specifically designed to achieve a highly efficient poly-chromatic illumination of the sample. It enables variable acquisition time frames, by means of a specially developed chopper (the FAN chopper) that suppresses selectively the sub-pulses generated by the resolution defining choppers. The energy resolution can be adapted in the range from 1% to 3% at 3meV and from 3% to 6% at 100 meV, thus providing flexible trading of resolution for flux, with the benefit o increasing the flux at the sample up to 5 times. By limiting the beam divergence through a set of collimators, the Q resolution can be tailored to experimental needs [5].
The secondary spectrometer features a vacuum path of 3 m from sample to detector, which will cover 2 sr when reaching full scope. With the angles covered by design, it will yield a dynamic range that extends from 0.05 Å-1 < Q < 10 Å-1, thus exploring a wide range of the reciprocal space.
T-REX Team
Forschungszentrum Jülich (DE): Nicolò Violini, Hans Kämmerling, Achim Heynen, Jörg Voigt, Thomas Brückel
Università degli Studi di Perugia (IT): Andrea Orecchini, Pietro Tozzi, Alessandro Paciaroni, Francesco Sacchetti
Consiglio Nazionale delle Ricerche (IT): Andrea Orecchini, Pietro Tozzi
References and Links
[1] E. Babcock, Z. Salhi, T. Theisselmann, D. Starostin, J. Schmeissner, A. Feoktystov, S. Mattauch, P. Pistel, A. Ioffe, J. of Phys / Conf. Series 711, 012008 (2016)
[2] E. Babcock, Z. Salhi, P. Pistel, A. Ioffe, G. Simeoni, J. of Phys / Conf. Series 528, 012018 (2014)
[3] Z. Salhi, E. Babcock, A. Ioffe, P. Pistel, J. of Phys / Conf. Series 528, 012015 (2014)
[4] J. Voigt, N. Violini, T. Brückel, NIMA 741, 26 - 32 (2014)
[5] N. Violini, J. Voigt, S. Pasini, T. Brückel, NIMA 736, 31 - 39 (2014)