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

Développement des techniques pour le diagnostic des procédés de projection thermique sous pression réduite

Le procédé de projection plasma à pression réduite (voire très réduite, inférieur à 10mbar) est en plein essors et connaît actuellement un développement considérable. Cette technique permet d obtenir des revêtements très denses avec un taux de porosité très faible tout en gardant un bon rendement de projection. Les caractéristiques des dépôts sont directement liées aux paramètres de projection (gaz plasmagène, puissance de la torche, débit de poudre), le réglage de ces paramètres peut être fait en mesurant les caractéristiques du plasma et des particules en vol. Le développement d un tel procédé nécessite donc des moyens de diagnostics et de contrôles performants. Le but de ce travail est d explorer les différents moyens de diagnostic optique applicable dans de telles conditions de projection. Notre approche pour cette étude utilise principalement le DPV2000 et la spectrométrie d émission. Le DPV2000 est utilisé pour les mesures de la température, la vitesse et le diamètre des particules en vol. Dans le cas de fines particules et/ou de basse température les particules sont éclairées par un laser afin de mesurer la vitesse et le flux de particules en vol. la spectrométrie d émission pour l étude de la vaporisation des particules en vol et les dimensions de l écoulement plasma.There is an increasing interest for thermal plasma spraying at working pressure lower than 10 mbars. By spraying at such low pressure, it is expected that resulting coatings have a very low porosity while keeping a deposition rate higher. Developing such processes requires adjusting operating parameters as gas mixtures, arc current and particle injection quantities, among others, in correlation with coatings to produce. Setting input parameters of this new spray processes can be made by measuring characteristics of the plasma and sprayed particles by using optical diagnose techniques. The aim of this study is to develop the use of different tools for optical diagnostics under such conditions. Particle measurements are performed by using the system DPV2000 with its sensor head located in a cooled tube at atmospheric pressure and measuring the particles through an optical window. When particles are too small or too cold to be detected, they are illuminated by a laser diode. In that case particle temperature measurements are not possible anymore but it is still possible to measure the in-flight particle velocity and flux. In addition to particle diagnostics, optical emission spectroscopy is used to quantify the plasma volume and to study the sprayed particle vaporization. The results allowed defining the characteristics of future process chamber to perform thermal spray technique at 0,1mbar pressure.BELFORT-BU L. FEBVRE (900102102) / SudocBELFORT-UTBM-SEVENANS (900942101) / SudocSudocFranceF

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

Progress report on the novel time-of-flight spectrometer with polarization analysis TOPAS

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