SEOP polarized 3 He Neutron Spin Filters for the JCNS user program

Over the past several years the JCNS has been developing in-house applications for neutron polarization analysis (PA). These methods include PA for separation of incoherent from coherent scattering in soft matter studies (SANS), and online polarization for analysis for neutron reflectometry, SANS, GISANS and eventually spectroscopy. This paper will present an overview of the user activities at the JCNS at the MLZ and gives an overview of the polarization 3He methods and devices used. Additionally we will summarise current projects which will further support the user activities using polarised 3He spin filters

3^{3}He Neutron Spin Filter cell development program at JCNS

In order to produce high-quality 3He Neutron Spin Filters (NSF) with a high polarisation level, it is necessary to achieve a long 3He relaxation time by the reduction of the wall relaxation. This requires one to minimise the amount of impurities at the surface of the glass cells, and to have as few contaminants as possible in the gas filling system. In this report we describe the detailed procedure we employ to produce 3He cells using our newly built filling station. The obtained life times for a number of cells are practically approaching the fundamental limit imposed by the dipole-dipole interaction between 3He atoms

Magic-PASTIS for XYZ polarization analysis using SEOP polarized 3^{3}He gas

We present progress towards a complete system for neutron polarization analysis on a time-of-flight (TOF) neutron spectrometer with a large area/angle detector array. Finite element calculations have been used to model the field gradients of a newly proposed PASTIS coil set, which uses a wide-angle banana shaped 3He Neutron Spin Filter cell (NSF) to cover a large neutron scattering solid angle. The final goal of this insert is to enable X-Y-Z polarization analysis to be installed on the future hot/thermal time-of flight spectrometers, although the method is also applicable to thermal/cold spectrometers as well. The components of this system, such as the magnetic field coils and design are applicable to neutron spectroscopy with wide angle detector arrays in general, and the 3He wide angle cell developments for polarized inelastic neutron scattering are independent from the methods used to polarize the gas as well

Considerations on Quality Factors from Super Mirrors and 3^{3}He Spin Filters for Polarization Analyzers on Wide Q-range Instrumentation

Polarization analysis will be needed on modern neutron scattering instrumentation designed to measure wide dynamic Q-ranges. These instruments will often use large area detectors and potentially multiple neutron wavelength bands or pulsed sources. This will place high demands on the method used for the polarization analysis. Two methods, super mirrors and 3He neutron spin filters, are often considered as the only solutions. In this paper we will discuss the basic differences in these two methods for applications measuring a wide dynamic Q-range via the use of large area detectors. First we will present the simplified theory for conceptual understanding of how both wide angle SM and wide angle 3He analyzer devices perform. Then we discuss how the properties of each method will effect neutron performance taking into account practical considerations. Such a conceptual understanding of the basics of design, performance and limitations of the two main options for such wide angle polarization analysis is timely given the growing momentum toward the use of such techniques as an extension of capability on current neutron instrumentation and for the planing of the many new instruments that will be designed in the near future, e.g., the future ESS source in Swede

The GISANS instrument at the HBS

This manuscript describes a concept of a grazing incidence small-angle neutron scattering (GISANS) instrument for the high brilliance source (HBS). The HBS being a compact pulsed neutron source using a moderate energy proton accelerator which allows for very compact moderators and shielding, and flexible pulse repetition rates. Similar to many other instrument concepts for this source, the lowest proposed HBS pulse frequency of 24 Hz with a relatively large detector distance is the optimal choice for the instrument described here in terms of obtained intensity and Q-range (i.e. scattering vector range). Such a configuration has the added advantage of good Q-resolution, which is important when scattering depths need to be resolved well. This is especially the case for GISANS when the incident angle is close to the critical angle of total reflection. The performance obtained from detailed ray-tracing computer simulations predict a high performance instrument that will be comparable to reflectometers and small angle neutron scattering (SANS) instruments at high-flux reactor sources such as the Forschungsreaktor Munich (FRM-2) and others

Polarization analysis on the small-angle neutron scattering diffractometer KWS-1: A faster, more versatile instrument

A number of upgrades have been made to the KWS-1 small-angle neutron scattering (SANS) instrument, operated by the Jülich Centre for Neutron Science (JCNS) and located at the research reactor FRM II of the Heinz Maier-Leibnitz Zentrum (MLZ) in Garching, Germany. A neutron flux on the sample of 1×108 cm−2 s−1 makes it one of the most intense SANS instruments in the world, while an optional double-disc chopper can reduce wavelength spread down to Δλ/λ = 1% [1], allowing for high resolution measurements. In this presentation, we will describe two recent upgrades, aimed towards optimization of studies of nanoscale magnetic correlations. The first is the installation of an upgraded detector. In September 2018, we were able to achieve commissioning of a new detector consisting of an array of 3He tubes interfaced with fast electronics (supplied by GE Reuter Stokes, OH, USA) to minimize dead-time for high-intensity measurements. An increase in the total detected area resulted in a new maximum Q-range of 0.7 Å−1, a 60% improvement over the previous geometry. 3He provides improved discrimination from background events, increasing signal-to-noise, while a faster detector response allows us to increase the source aperture for even shorter measurement times. In-line with our development of KWS-1, particularly for the magnetic SANS community, we report on recent developments for the option of measuring with polarization analysis. An analyser cell with polarized 3He allows detecting all four scattering cross-sections with a Qmax > 0.06 Å−1. The 3He cell is contained inside a μ-metal chamber, designed in-house by our JCNS 3He group, to ensure a high degree of uniformity of the magnetic field at the cell position. In recent experiments, a cell lifetime of more than 90 hours was achieved. The achieved cell lifetime is more than 90 hours. A new option for in-situ polarization of a 3He cell, allowing for time-independent analyzing efficiency of post-scattered neutrons, will be discussed