Expected performance of time-gradient magnetic field SESANS diffractometer at pulsed reactor IBR-2

Abstract

The application of the time-gradient magnetic field neutron spin-echo technique (TGF-NSE) aiming to extend the possibilities of the REFLEX reflectometer at the pulsed reactor IBR-2 (Dubna, Russia) towards a high and medium resolution small-angle scattering is considered. This technique requires the use of a linearly increasing magnetic field in the form of the sequence of saw-teeth pulses. Such a technique is well-suited to the pulsed structure of the neutron beam at the IBR-2 reactor. The wide range of neutron wavelengths employed in the time-of-flight (TOF) operation mode allows for the simultaneous coverage of a wide range of spin-echo lengths (corresponding to a wide Q-range in conventional SANS). Virtual experiments carried out using the VITESS simulation package demonstrate that such a setup at IBR-2 will allow for the coverage of the length scales from 100 Å to 6000 Å in a single instrument setting. The use of the TGF-NSE technique in the TOF mode leads to gaps in the measured SANS curves due to the jumps of magnetic field at the end of saw-teeth pulses. However, crucially, these do not harm the quality of the data. Moreover, the lost data can be retrieved by an additional measurement with a delayed start of the magnetic pulse sequence.