Final Assembly of the Helmholtz Zentrum Berlin Series Connected Hybrid Magnet System

The final assembly of the Series Connected Hybrid magnet system for the Helmholtz Zentrum Berlin for Materials and Energy HZB has occurred with the integration of the superconducting cold mass, cryostat, resistive Florida Bitter coils, and the cryogenic, chilled water, power, and control subsystems. The hybrid magnet consists of a 13 T superconducting Nb3Sn CICC coil and a set of 12 T resistive, water cooled coils at 4.4 MW. Much of the cryostat and cold mass functional requirements were dictated by the electromagnetic interactions between the superconducting and resistive coils. This includes the radial decentering and axial aligning forces from normal operations and a 1.1 MN fault load. The system assembly was an international achievement with the cold mass being completed at the NHMFL in the USA, cryostat to cold mass interfaces made at Criotec Impianti in Italy, and final assembly at the HZB in German

First Hybrid Magnet for Neutron Scattering at Helmholtz Zentrum Berlin

Helmholtz Zentrum Berlin HZB operates two large scale facilities the research reactor BER 2 and the syn chrotron source for soft X rays BESSY 2. This year HZB s neu tron instrument suite around BER 2 has been strengthened by a unique high magnetic field facility for neutron scattering. Its main components are the High Field Magnet HFM , which is the most powerful dc magnet for neutron scattering worldwide, and the Extreme Environment Di ffractometer EXED , which is a dedicated neutron instrument for time of flight technique. The hybrid magnet system is projected according to the special geo metric constraints of analyzing samples by neutron scattering in a high field magnet. Following our past experience, only steady state fields are adequate to achieve the goals of the project. In particular, inelastic scattering studies would virtually be excluded when using pulsed magnets. The new series connected hybrid magnet with a horizontal field orientation was designed and constructed in collaboration with the National High Magnetic Field Laboratory NHMFL , Tallahassee, FL, USA. With a set consisting of a su perconducting cable in conduit coil and different resistive coils of conical shape, maximum fields between 26 31 T are possible with cooling power between 4 and 8 MW for the resistive part. A series of commissioning activities of the magnet components and the technical infrastructure systems 20 kA power supply, water cooling, and 4 K Helium refrigerator was completed at HZB. The maximum field achieved with a 4 MW resistive coil was 26

Atomic Transport in Dense, Multi-Component Metallic Liquids

Pd43Ni10Cu27P0 has been investigated in its equilibrium liquid state with incoherent, inelastic neutron scattering. As compared to simple liquids, liquid PdNiCuP is characterized by a dense packing with a packing fraction above 0.5. The intermediate scattering function exhibits a fast relaxation process that precedes structural relaxation. Structural relaxation obeys a time-temperature superposition that extends over a temperature range of 540K. The mode-coupling theory of the liquid to glass transition (MCT) gives a consistent description of the dynamics which governs the mass transport in liquid PdNiCuP alloys. MCT scaling laws extrapolate to a critical temperature Tc at about 20% below the liquidus temperature. Diffusivities derived from the mean relaxation times compare well with Co diffusivities from recent tracer diffusion measurements and diffsuivities calculated from viscosity via the Stokes-Einstein relation. In contrast to simple metallic liquids, the atomic transport in dense, liquid PdNiCuP is characterized by a drastical slowing down of dynamics on cooling, a q^{-2} dependence of the mean relaxation times at intermediate q and a vanishing isotope effect as a result of a highly collective transport mechanism. At temperatures as high as 2Tc diffusion in liquid PdNiCuP is as fast as in simple liquids at the melting point. However, the difference in the underlying atomic transport mechanism indicates that the diffusion mechanism in liquids is not controlled by the value of the diffusivity but rather by that of the packing fraction

Results of the test of a pair of 20 kA HTS currents 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 n Omega (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