Resolution in excitation width: 0.1 μeV to 50 μeV

The amplitude of the echo as a function of the Fourier time (i.e. the current in Larmor precession coils) gives a measurement of the damping/line width of an excitation. A purely elastic or harmonic line (Dirac) should have a zero width, i.e. an infinite life time. As the physics is often more complex, quasielastic, inelastic and anharmonic processes are responsible for a finite damping, which may be measured with IN20/TASSE.
In the 1-6 Amps range for the Larmor precession field, a line width from 0.1 μeV up to 50 μeV may typically be measured.

Resolution in energy shift: 1 μ-eV to 500 μeV

The phase shift of the echo is related to the energy shift of the observed excitation (anharmonicity, Gruneisen parameter, non linear coupling...). For elastic lines (structure), this shift is expected to be null, but inelastic line shifts may be measured from 1 μeV up to few 100 μeV in the 1-6 Amps range for the Larmor precession field.

The wavevector and energy range are set by the IN20 TAS instrument. Thanks to the Optimized Field Shape coil geometry, the Larmor precession stray fields are negligible at the coils extremities as well as along them (because of the superconductive shielding), which make coil/instrument tuning independent of the scattering angle A4. There is thus no fringe field interference between spectrometer arms.

Fourier time range: from 0 to 3.2 ns
At K_i=2.662 Å^-1 the Larmor precesssion coils with 1 Amps correspond to a Fourier time of t=160 ps. The maximum current in the precession coils is 20 Amps, which then enable to reach t=3.2 ns.

Practically, the Fresnel spiral coils limit presently the Fourier time to t=1 ns (6 Amps in the precession coils).