In this section
Tosca
Tosca is an indirect geometry spectrometer optimised for the study of molecular vibrations in the solid state. In its present form, the instrument has been operational since 2000 and during that time has set the standard for broadband chemical spectroscopy with neutrons.
Instrument scientists
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Technical information
Tosca covers the energy transfer range between -24 cm-1 and 4000 cm-1, and has an outstanding spectral resolution of approximately 1.25% ET.
Measurements are typically performed at very low temperatures (<30 K) and sample masses are typically on the gram scale. The instrument sits at 17.01 m from a room temperature water moderator, while the neutron beam at the sample position has a square shape and is 4.5 x 4.5 cm2 in size. The double disc 4-blade chopper, running at 10 Hz, is positioned at a distance of 9.455 m from the moderator centre. The chopper prevents pulses overlap and blocks the slow neutrons for the three pulses and allows them to pass during the long pulse. The secondary flight path is 0.6 m long on average, while the detector array is comprised of a total of ten banks each having thirteen 30 x 1 cm2 3He squashed tubes.
Related resources
Sample environment
Sample cells
- Standard cells (cells for the sample changer and air sensitive samples)
- Gas handling cells – a lot of experiments in areas like catalysis and hydrogen storage require dosing of gases
- Specialist cells that can be treated at high temperatures with and without gas handling
Sample changer
Tosca has an automated sample changer that can handle up to 36 samples. The operation of the sample changer is controlled by the computer in the cabin.
Parahydrogen rig
A specialised parahydrogen rig, part of the gas handling kit, has been designed to be used mainly with Tosca.
Parahydrogen is required to study the rotational line of molecular hydrogen. We produce parahydrogen by liquefying hydrogen at 20 K on a paramagnetic salt that acts as a catalyst to convert orthohydrogen into parahydrogen.
The conversion process takes less than 12 hours for an efficiency of 98% conversion.
If your experiment requires the use of parahydrogen, contact the instrument scientists.
Software
Inelastic neutron scattering (INS) spectroscopy, contrary to other vibrational spectroscopic techniques such as infrared or Raman spectroscopies, provides richer microscopic insight into a material due to the absence of selection rules induced by the symmetry of the molecule and via its dependence on both energy (E) and momentum (Q) transfer. First-principles density functional theory (DFT) based calculations are now routinely used to interpret infrared and Raman spectra. These calculations can also be used to interpret INS spectra, however, there is a need to include the neutron scattering cross sections, overtones and combination modes, together with instrument specific E-Q windows. abINS is an open source algorithm in Mantid that uses the normal modes that are obtained from DFT calculations. As the algorithm is available within Mantid, it is straightforward to compare theory and experiment.
Following features are available in abINS available in Mantid version 6.3:
- ability to use data from a number of DFT lattice dynamics packages: CASTEP, CRYSTAL, DMOL3, GAUSSIAN, VASP, PHONOPY
- providing temperature adjustment through the Debye-Waller factor
- providing control over overtones (1 to 10)
- providing atom projected INS spectrum for in-depth analysis
- providing control over Tosca forward and backward detectors
You can find more information about abINS on this website.
If you use abINS, please cite: K Dymkowski, SF Parker, F Fernandez-Alonso and S Mukhopadhyay, AbINS: The modern software for INS interpretation (2018). doi:10.1016/j.physb.2018.02.034
The other software for Tosca data analysis is aClimax.
Recent publications
Instrument reference
All publications and datasets based on experiments using Tosca should cite that the data is collected by DOI: 10.5286/isis.instrument.2527. Experiment DOIs follow the format 10.5286/ISIS.E.RBXXXXXXX, where XXXXXXX is the 7-digit experiment (RB) number and these can be viewed via the Data Gateway.
Reference papers:
Recent and future developments on Tosca at ISIS, S.F. Parker, F. Fernandez-Alonso, A.J. Ramirez-Cuesta, J. Tomkinson, S. Rudić, R.S. Pinna, G. Gorini and J. Fernández Castañon, Journal of Physics Conference Series, 554 (2014) 012003. [DOI: 10.1088/1742-6596/554/1/012003]
The neutron guide upgrade of the TOSCA spectrometer, R.S. Pinna, S. Rudić, S.F. Parker, J. Armstrong, M. Zanetti, G. Skoro, S.P. Waller, D. Zacek, C.A. Smith, M.J. Capstick, D.J. McPhail, D.E. Pooley, G.D. Howells, G. Gorini, F. Fernandez-Alonso, Nuclear Ins. and Methods in Physics Research A 896, 68 (2018).