Polarization Analysis with 3He Spin Filters for Separating Coherent from Incoherent Scattering in Soft Matter Studies

In soft matter small angle neutron scattering (SANS) studies at large Q values, incoherent scattering becomes the dominant signal. In the Q-range of interest to this work, from 0.2 Å−1 to about 1.0 Å−1, the coherent scattering from the typical protein or polymer in a D2O buffer solution inevitably drops one to two orders of magnitude or more below the total scattering. Even after careful and accurate subtraction of the measured D2O buffer scattering, the remaining corrected, i.e. sample-only, signal will still be dominated by diffuse incoherent scattering from hydrogen in the sample itself. This is the exact region of interest when one wishes to probe the structural changes in “living” proteins caused by interactions and motions related to function. To further complicate the problem, there is strong motivation to measure this Q-regime at very low concentrations because it has been shown with wide angle X-ray scattering that proteins can undergo concentration-dependent structural changes that rapidly increase below concentrations of about 5% [1] motivating the study of protein solutions at ever lower concentrations. In this case the signal from the protein will inevitably become much less than the scattering of the D2O buffer solution it is contained in. Polarization analysis offers the opportunity to separate the weak coherent signal from the larger incoherent signal and perhaps enable measurements under the conditions described above. This paper will address the issues associated with the correct separation of coherent and incoherent scattering for soft matter samples. We have performed tests measurements on KWS2 which show the viability of the method on a protonated α-lactalbumin solution at 2.5% (1 mm thick) and 0.25% (2 mm thick) concentrations in a D2O buffer solution. Additionally describe a the method of implementation using 3He spin filters, some practical considerations, and future plans for a dedicated device at the JCNS

A new neutron depth profiling spectrometer at the JCNS for a focused neutron beam

© 2020, © 2020 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. A new neutron depth profiling (NDP) spectrometer has been designed and built for the use at a high intensity focused cold neutron beam of the reflectometer MARIA at the Heinz Maier-Leibnitz Zentrum (MLZ, Germany). The extremely high neutron flux at the sample position of MARIA joined with the multiple charged particle detectors allows less than 10 s sampling rate and paves the way to study the kinetics of Li ions in thin-film microbatteries. The performance of the spectrometer with standard calibration samples and (Formula presented.) amorphous thin films is presented; possibilities to operando study the Li distribution inside thin-film rechargeable lithium batteries are discussed

A new fast detection system at the KWS-2 high-intensity SANS diffractometer of the JCNS at MLZ - prototype test

A new detection system based on an array of 3He tubes and innovative fast detection electronics was designed and produced by GE Reuter Stokes for the high-intensity small-angle neutron scattering diffractometer KWS-2, operated by the Jülich Centre for Neutron Science (JCNS) at the Heinz Meier-Leibnitz Zentrum (MLZ). The new detector consists of a panel array of 144 3He tubes and a new fast read-out electronics. The electronics is mounted in a closed case in the backside of the 3He tubes panel array and will operate at ambient atmosphere under cooling air stream. The new detection system is composed of eighteen 8-pack modules of 3He-tubes that work independently of one another (each unit has its own processor and electronics). Knowing beforehand the performance of one detector unit and of one single tube detector is prerequisite for tuning and maximizing the performance of the complete detection system. In this paper we present the results of the tests of the prototyped 8-pack of 3He-tubes and corresponding electronics, which have been carried out at the JCNS instruments KWS-2 (in high flux conditions) and TREFF

A new neutron depth profiling spectrometer at the JCNS for a focused neutron beam

A new neutron depth profiling (NDP) spectrometer has been designed and built for the use at a high intensity focused cold neutron beam of the reflectometer MARIA at the Heinz Maier-Leibnitz Zentrum (MLZ, Germany). The extremely high neutron flux at the sample position of MARIA joined with the multiple charged particle detectors allows less than 10 s sampling rate and paves the way to study the kinetics of Li ions in thin-film microbatteries. The performance of the spectrometer with standard calibration samples and LiNbO3 amorphous thin films is presented; possibilities to operando study the Li distribution inside thin-film rechargeable lithium batteries are discussed

In Situ Dynamic Light Scattering Complementing Neutron Spin Echo Measurements on Protein Samples

Monitoring the state of the sample on the minute-time scale is crucial in case of sensitive soft matter or biological samples, given that neutron spin echo measurements take up to several days. Moreover, there is no method to interpret the normalized intermediate scattering function obtained by neutron spin echo measurements if relevant sample properties change during the measurement. Dynamic light scattering provides information on the diffusion constant of particles in solution (biological macromolecules like proteins, protein aggregates, polymer particles, etc.) with average hydrodynamic radii in a broad range from a few nanometers up to several microns. This information can be obtained within a few minutes and it offers a good overview of the current sample state. Details on the novel in situ dynamic light scattering set-up with one fixed scattering angle and first results obtained on a molten globule state of apo-myoglobin are presented

Multi-angle in situ dynamic light scattering at a neutron spin echo spectrometer

A new sample environment, called Bio-Oven, has been built for the Neutron Spin Echo (NSE) SpectrometerJ-NSE Phoenix. It provides active temperature control and the possibility to perform Dynamic Light Scattering(DLS) measurements during the neutron measurement. DLS provides diffusion coefficients of the dissolvednanoparticles and thus one can monitor the aggregation state of the sample on a time scale of minutes duringthe spin echo measurement times on the order of days. This approach helps to validate the NSE data or toreplace the sample when its aggregation state influences the spin echo measurement results. The new Bio-Ovenis an in situ DLS setup based on optical fibers decoupling the free space optics around the sample cuvettein a lightproof casing from the laser sources and the detectors. It collects light from three scattering anglessimultaneously. Six different values of momentum transfer can be accessed by switching between two differentlaser colors. Test experiments were performed with silica nanoparticles with diameters ranging from 20 nm upto 300 nm. Their hydrodynamic radii were determined from DLS measurements and compared with the onesobtained by a commercial particle sizer. It was demonstrated that also the static light scattering signal can beprocessed and gives meaningful results. The protein sample apomyoglobin was used for a long-term test and ina first neutron measurement using the new Bio-Oven. The results prove that the aggregation state of the samplecan be followed using in situ DLS along with the neutron measurement

KWS-2 SANS diffractometer for soft-matter and biological systems

The KWS-2 classical pinhole small-angle scattering instrument is a dedicated facility for structural studies in the fields of soft-condensed matter, chemistry and biology. Recent upgrades of the detection system aimed for optimization of the instrument towards high intensity structural studies and investigations of fast structural changes due to rapid kinetic processes