Analysis of time-of-flight small-angle neutron scattering data on mesoscopic crystals such as magnetic vortex lattices

Bragg diffracted intensities and q values for crystalline structures with long repeat distances may be obtained by small-angle neutron scattering (SANS) investigations. An account is given of the methods, advantages and disadvantages of obtaining such data by the multichromatic time-of-flight method, compared with the more traditional quasi-monochromatic SANS method. This is illustrated with data obtained from high-magnetic-field measurements on magnetic vortex line lattices in superconductors on the former HFM/EXED instrument at Helmholtz-Zentrum Berlin. The methods have application to other mesoscopic crystalline structures investigated by SANS instruments at pulsed sources

Results of the test of a pair of 20 kA HTS current leads

A new series connected 25 T hybrid magnet system is being set up by the Helmholtz Zentrum Berlin (HZB) for neutron scattering experiments. CRPP has designed and manufactured a pair of 20 kA current leads for the powering of the outer superconducting coils of the hybrid magnet system. In connection with the test of joints for JT60SA, the current leads were tested at ENEA at low voltage up to a current of 18 kA. The mass flow rates required to cool the current leads at different currents measured in the test are in line with the design calculations. For the sum of the resistances of the warm and cold end copper contacts of the HTS module values of 13 (Lead A) and 11 nOhm (Lead B) were measured. In addition, the helium flow through the heat exchanger part was stopped at 10 and 12 kA to study the behaviour of the current leads in case of a loss of flow. The time elapsed between stopping of the helium mass flow and the initiation of a quench was found to be 117 s (Lead A) and 125 s (Lead B) compared to a calculated value of 86 s. The lower value obtained by the calculation can be attributed to the lower initial temperatures in the experiment