The BER II neutron source is back in operation and available for experiments following the interruption in availability
The High-Field Magnet (HFM) has attained 26 tesla in an initial test and thereby exceeded expectations. The HFM team is pleased about the well-deserved success.
© HZB/Ingo Kniest
Maintenance work has been successfully concluded – the High-Field Magnet has successfully attained 26 tesla in initial testing. New scientific experiments have become possible.
Berlin, February 2015: following conclusion of more than a of year of repairs and refurbishing, the BER II neutron source will shortly be available to its international user group again. The facility was powered up on Wednesday, February 18 and attained its nominal power level of 9,5 megawatts. Scientists of HZB are meanwhile preparing the measurement equipment so that experimental work can resume following a brief start-up period.
During the service interruption, a weld joint was eliminated that was known to be a potential weak point. This involved a weld joint for a seal located in the area of the separator between the two reactor pool halves. Damage to this weld joint was discovered in 2010 and has been carefully monitored since that time. This did not involve a component critical to safety; nevertheless, it was decided in 2013 to completely remove the weld joint.
At the same time, the new High-Field Magnet went through final assembly and was setup in its final operating position inside in the Neutron Guide Hall. Its 26-tesla magnetic field was first generated in December 2014 and it maintained this value stably over a longer period of time. So it even exceeded its target value of 25 tesla.
Following the maintenance period, an important objective was reached with the successful resumption in BER II operations: participants of the international Neutron School can again be offered actual neutron experiments of the customary high quality. The 12-day advanced course for young scientists will be taking place in Berlin for the 35th time, from February 26th to March 6th.
Developing and successfully setting up the High-Field Magnet, unique for neutron experiments, has only taken 7.5 years. All of the comparable hybrid magnet construction projects worldwide during the past 25 years have taken between 9.5 and 16 years. The brief project length can therefore be viewed as top of its class. In addition, the project remained within its planned budget of just under 21 mil. EUR after adjusting for inflation.
The High-Field Magnet represents yet another first-class instrument that is being connected to the neutron source for the final BER II support period. Completely new kinds of experiments become possible that will open up access to new science, such as researching superconduction and magnetic phase transitions in solid-state materials, for example.
- Magnetic imaging: Micro-flowers increase the local magnetic fieldMaterials with magnetic nanostructures have many potential applications such as in spintronics. To explore such materials, nanoscale magnetic-sensitive imaging techniques are very useful, but up to now only weak magnetic fields could be applied during the imaging process. Now an international collaboration led by Dr. Sergio Valencia, HZB, has developed an approach that overcomes this limitation. The team designed tiny magnetic flux concentrators (MFCs), into which the sample is placed. The geometry of the MFCs resembles a flower with a number of petals which focus the applied magnetic field into its center. This greatly expands the magnetic field range available during imaging, and so the range of magnetic systems that can be investigated. The micro-flowers, enhancing magnetic fields locally, can find application in different nanometric magnetic microscopy techniques.
- Disorder creates new properties in compound semiconductorsAn international research team has demonstrated that the intrinsic disorder of the compound semiconductor CuInSnS₄ can be exploited to influence its optical properties. While the atomic vibrations also sense the local disorder, their response is averaged over many different local environments and therefore appear isotropic, as expected for a cubic crystal. In contrast, the optical excitations, known as excitons, are much more sensitive to the local arrangement of atoms. Surprisingly, they show a direction-dependent optical response even though the average crystal structure is cubic. These findings shed new light on the relationship between disorder and material properties, opening up new options for targeted 'disorder engineering' in optoelectronic and photocatalytic devices.
- Superconducting TES array X-ray spectrometer goes into operation at BESSY IIEurope's first and only TES-spectrometer at a synchrotron source is now in operation at BESSY II, developed within a collaboration between the HZB, the MPI-CEC (Mühlheim-an-der-Ruhr, Germany) and the NIST (Boulder CO, USA). The photon detection efficiency of the new instrument exceeds that of wavelength-dispersive X-ray emission spectrometers by a factor of 100 to 1000. It will be used to investigate the electronic properties of atomically thin layers, nanostructures and highly diluted atomic and molecular samples. The team is looking forward to receiving exciting research proposals from the user community.