Development of an halbach array for a gisaxs instrument

For nanoparticle research, a Halbach array device has been developed that allows the dynamic reproducible definition of the magnet field strength and orientation at a sample. The maximum achievable field strength is 0.5 Tesla. The main application of the Halbach array will be in the sample environment of the GISAXS instrument GALAXI.The magnet field orientation and strength are defined by rotating permanent magnets with stepper motors. Control of the stepper motors is implemented with a S7-1500 PLC in the ET200SP form factor. All field computations are executed in Nicos which controls the device. One challenge in development is the dynamic positioning of magnets due to changing forces. For vacuum applications, a water-cooling system has been implemented that allows the control of the motor temperatures. Design and implementation of the Halbach array device as well as future plans will be presented

Design and test of a reverse osmosis pressure cell for in-situ small-angle neutron scattering studies

We introduce a new method for real-time studies of membrane scaling and biofouling on thin film composite membranes (TFC) in reverse osmosis and nanofiltration water treatment using in-situ small-angle neutron scattering (SANS). SANS delivers information on nano and microscopic structures that support the interpretation of relevant engineering parameters such as membrane permeability and water flux. A flow cell high pressure SANS is described, followed by SANS characterization of TFC membranes finding ~ 0.5 μm large cavities and ~ 300 Å diameter large rod-like cavities inside the non-woven polyester and micro-porous polysulfone layer, respectively. In-situ desalination experiments in cross-flow mode at an applied pressure of 6 bars and feed flow velocity of 0.2 cm/s are followed. The scattering cross-section times sample thickness (μt = Σt × DS) derived from the transmission coefficient shows an overall enhancement due to newly formed scattering centers which is accompanied by a reduced membrane permeability measured simultaneously. This observation is supported by enhanced scattering of the membrane due to μm large domains of mass fractal structure. The addition of the protein BSA to the feed after desalination of 30 h effectuates strong enhancement of the permeability accompanied by a about a 50% decline of μm large scattering centers

TetraMag: A compact magnetizing device based on eight rotating permanent magnets

In this paper we describe a novel magnetizing device based on eight rotatable permanent magnets arranged in a quadrupolar configuration, which is termed the TetraMag. TetraMag creates stable and homogeneous magnetic fields at the sample position with a resolution of 0.02 mT tunable between –570 mT and +570 mT. The field direction is continuously rotatable between 0° and 360° within the sample plane, while the field strength is maintained. A simplified mathematical description of TetraMag is developed leading to magnetic field calculations which are in good agreement with the experimental results. This versatile device avoids electrical energy dissipation, cooling mechanisms, and hysteresiseffects known from classical electromagnets. It is ultrahigh vacuum compatible and it offers a completely free optical path over 180° for magneto-optical experiments. It is suitable for scattering experiments with synchrotron radiation and neutrons and may be employed in a large class of magnetization experiments

Technical Specification of the Small-Angle Neutron Scattering Instrument SKADI at the European Spallation Source

Small-K Advanced DIffractometer (SKADI is a Small-Angle Neutron Scattering (SANS) instrument to be constructed at the European Spallation Source (ESS). SANS instruments allow investigations of the structure of materials in the size regime between Angstroms up to micrometers. As very versatile instruments, they usually cater to the scientific needs of communities, such as chemists, biologists, and physicists, ranging from material and food sciences to archeology. They can offer analysis of the micro- and mesoscopic structure of the samples, as well as an analysis of the spin states in the samples, for example, for magnetic samples. SKADI, as a broad range instrument, thus offers features, such as an extremely flexible space for the sample environment, to accommodate a wide range of experiments, high-flux, and optimized detector-collimation system to allow for an excellent resolution of the sample structure, short measurement times to be able to record the internal kinetics during a transition in the sample, as well as polarized neutron scattering. In this manuscript, we describe the final design for the construction of SKADI. All of the features and capabilities presented here are projected to be included into the final instrument when going into operation phase

Polarimetry for 3He Ion Beams from Laser–Plasma Interactions

We present a compact polarimeter for 3He ions with special emphasis on the analysis of short-pulsed beams accelerated during laser–plasma interactions. We discuss the specific boundary conditions for the polarimeter, such as the properties of laser-driven ion beams, the selection of the polarization-sensitive reaction in the polarimeter, the representation of the analyzing-power contour map, the choice of the detector material used for particle identification, as well as the production procedure of the required deuterated foil-targets. The assembled polarimeter has been tested using a tandem accelerator delivering unpolarized 3He ion beams, demonstrating good performance in the few-MeV range. The statistical accuracy and the deduced figure-of-merit of the polarimetry are discussed, including the count-rate requirement and the lower limit of accuracy for beam-polarization measurements at a laser-based ion source

A High-Density Polarized 3He Gas–Jet Target for Laser–Plasma Applications

A laser-driven spin-polarized 3He2+-beam source for nuclear–physics experiments and for the investigation of polarized nuclear fusion demands a high-density polarized 3He gas-jet target. Such a target requires a magnetic system providing a permanent homogeneous holding field for the nuclear spins plus a set of coils for adjusting the orientation of the polarization. Starting from a transport vessel at a maximum pressure of 3 bar, the helium gas is compressed for a short time and can be injected into a laser–interaction chamber through a non-magnetic opening valve and nozzle, thus forming jets with densities of about a few 1019 cm−3 and widths of about 1 mm. The target comprises a 3D adjustment system for precise positioning of the jet relative to the laser focus. An auxiliary gas system provides remote target operation and flushing of the gas lines with Ar gas, which helps to reduce polarization losses. The design of the target, its operation procedures and first experimental results are presented

A polarized 3He Target for the Exploration of Spin Effects in Laser-induced Plasmas

In order to investigate the polarization degree of laser-accelerated 3He ions from a polarized 3He gas-jet target, several challenges have to be overcome. One of these is the development of an appropriate polarized 3He gas-jet target. Since our experiments are carried out at the PHELIX Petawatt Laser Facility, GSI Darmstadt, the layout of the set-up has to cope with the available space within the PHELIX target chamber. The essential components of such a layout are a magnetic holding field for storing polarized 3He gas inside the vacuum chamber for many hours, the gas-jet source for providing the desired laser target, and finally, a polarimeter for measuring the spin-polarization degree of laser-accelerated 3He2+ ions