Science method

# Neutron Scattering - Science method

General group concerning neutron scattering techniques

Questions related to Neutron Scattering

Dear RG community,

I have just started my research career in the field of neutron spectroscopy.

I would be grateful if you could suggest some important books to read to get a deeper understanding of the subject matter.

Research interests: Neutron scattering, Neutron diffraction, Neutron imaging.

Thank you.

Regards,

KP

How to draw the anisotropy in different direction like the below figure from elastic constant data.

This book is not published anymore. The full reference is : "Neutron Scattering from Hydrogen in Materials" ; Proceedings of the second Summer School on Neutron Scattering : Zuoz, Switzerland, 14-20 August 1994 ; A. Furrer (ed.) ; World Scientific Singapore ; 1994. I'm looking for a scanned copy of the whole book. Thanks for your help ! Regards. Nicolas.

Dear all,

Please, any suggested publications to read about any real applications were performed using Bragg-edge neutron imaging BUT with "thermal" neutron beam (1.8 A° +/-), if existed, other than the most famous ones that use cold monochromatic beams for strain mapping or magnetism studies?

Thanks a lot in advance.

Mahmoud

Two most important structural parameter of a molecule is size and shape. While there is many spectroscopic (like DLS, neutron scattering, fcs) and microscopic (SEM,tem, AFM, etc); for shape measurement as I know, we depend on microscopic techniques.

I want to know other than such imaging techniques are there any such techniques that can measure the shape of nanoparticle or protein?

In small angle neutron scattering SAS (actually small angle neutron scattering, SANS), I obtained a 1D pattern showing a peak which is located over 1 inverse angstrom. The actual peak position is approximately 1.2 inverse angstrom. What is the possible meaning of it??

The scattered specimen is martensitic steel including inclusions in dozen nanometers and precipitate particles in few nanometers. The peak exists always regardless of heat-treatment.

Can I get a small clue on it??

(Please see the attached figure.)

The thermal neutron scattering length depends on the relative spin orientation of neutron and nucleus. It is defined such that b>0 corresponds to a repulsive potential and b<0 to an attractive potential.

Looking at the example of neutron scattering on protons, the two scattering lengths are listed separately in textbooks and e.g. in http://www.ati.ac.at/~neutropt/scattering/RecommendedScatteringLengths.PDF

They all agree that a combined spin of the neutron-proton system of 1 has a positive scatternig length (repulsive) and a combined spin of 0 a negative scattering length (attractive).

My question is why does this not line up with the fact that the S=1 deuteron state is bound (i.e., attractive) and the singlet state is unbound (i.e., repulsive)?

I have a thin porous material whose saturation needs to be determined. The relative permeability for a multi-phase flow is to be determined through the porous material and in order to express relative permeability as a function of saturation, I need to determine the saturation. The sample is of the dimension of 10mmX5mm and thickness of approximately 500 microns. How can I effectively measure the water saturation. Also, I think the internal methods of saturation determination like X-Ray method, neutron scattering would be not very effective considering the small dimensions of the sample. Correct me if I'm wrong.

How this Incoherent Scattering Component is high for 1H

What is the magnetic propagation vector (k) of helimagnetic phase of Cr

_{1/3}NbS_{2}?Consider for a homogenous nuclear reactor which is a toroidial tube filled with something like plutonium or uranyl nitrate solution. The toroidal has an infinite neutron scattering medium around it such as a vast volume of water.

How do we calculate the geometric buckling of the system ?

whats the difference in hydrogen-neutron and deuteron-neutron interaction?

I have read a lot of references about neutron scattering. But I am still confused by these phrases: coherent elastic scattering, incoherent elastic scattering, coherent inelastic scattering and incoherent inelastic neutron scattering? I learned that coherent elastic scattering is generally used for neutron diffraction measurement, and that coherent inelastic neutron scattering is used to measure phonon or magnon dispersion relations. But how about incoherent elastic scattering and incoherent inelastic scattering? What are their fundamental differences? What are their different applications in neutron scattering measurements?

How to understand diffuse scattering? What is the difference between elastic and inelastic diffuse scattering?

This is highly related to the critical phenomena in strongly correlated electron systems. Through this challenging question, I would like to invite those active researchers who have long been involved in the field of statistical physics and theoretical condensed matter physics so that we can at least find some clue to proceed ahead.

Neutron sources that produce fast neutrons uses a Spallation process but why not use a non-uniform magnetic field to act on the magnetic moment of the neutron to accelerate it, we know that the neutron will precess around the field say in the z-axis, then a gradient of the magnetic field in the plus z-direction will accelerate the neutron in the minus z-direct.

I'm about to analysis some neutron scattering curves via Sasview. However, this is my first time to fitting neutron scattering data. I don't know which model to choose. Are there any principles for that? Thanks.

I have a problem to understand how to calculate an MSD(t) (Mean Square Displacement), from a time trace, when the time intervalls between two consecutive points are not constant, and even change randomly, e.g. (data were recorded with the delta_t = 2 us):

t x

0.418424 -1.162677

0.418426 -1.187103

0.418432 -1.187103

0.418434 -1.206644

0.418436 -1.226185

0.418440 -1.235955

0.418442 -1.260381

0.418444 -1.245725

0.418446 -1.216414

0.418448 -1.187103

0.418452 -1.152907

0.418454 -1.123596

0.418456 -1.148021

0.418460 -1.167562

0.418462 -1.187103

0.418464 -1.172447

If somebody is able to write some steps (with my real values t and x) it would be great. How does the plot(MSD(t), t) look like?

structure factor solid state debye waller factor

My vesicle samples were stable from 5 - 10 mM. What concentration should I prefer for the measurement of Small Angle Neutron Scattering?

I am trying to analyze the SANS data using the Guinier-Porod model.

There are five parameters in the model: Guinier Scale, Dimension Variable, Rg, Porod Exponent and Background.

The Dimension Variable, Rg and Porod Exponent are strongly dependent on the Guinier Scale and background when I was fitting my data.

However, I read the papers using this model and cannot find the details about how to determine the Guinier scale and background.

Is the Guinier scale related to the volume fraction?

In a neutron diffraction experiment, how will the S(Q) look for strong absorbing atoms? Will it only affect low-Q range, high-Q range, or it will just shift the whole baseline downward at a constant value for the whole range?

and probably how do we correct it?

Thank you!

For example of a system with Li-6 isotopes in it.

What technique could one use to create a 3 dimensional image/composition analysis of a material that is made of two isotopes of the same element? For instance, if I make a disc of magnesium, and then coat it with a thin layer of a magnesium isoptope, what technique/instrument could I use to tell me the dimensions/volume/area/thickness of the isotope layer, and could also render an image that differentiates the two? The only thing I have found is neutron scattering (XRD for isotopes), but I want a volumetric analysis.

As you may know, neutrons are electrically neutral and can only be deflected by a magnetic field. The magnetic field interacts with the spin of neutrons i.e. the magnetic moment of neutrons and their trajectory is influenced in the presence of the magnetic field due to the magnetic force.

I know that the CST or COMSOL package can be used for tracking of charged particles such as electrons or protons in electromagnetic field.

However I need to design a certain type of magnetic field by putting several magnet together and then pass the neutrons through the magnetic field and study the trajectory of neutrons.

Do you have any idea if COMSOL or CST are capable of neutron tracking? or if they are not, could you please introduce any other package that you know?

In a cold neutron scattering experiment, the time-scale of the neutron-(phonon/magnon) interaction is often assumed to be in the range 1-10 ps. For a magnetic order this means that the order will appear static to the neutron probe if its dynamics is much slower than 10 ps or if it has an energy lower than about 0.5 meV. How can this time-scale be calculated?

The resolution of a neutron scattering diffractometer can be calculated via its energy resolution. An excitation of energy much smaller that the width in energy of the Bragg peak cannot be resolved. Typically an excitation of less than 1-0.1 meV cannot be resolved.

However it appears difficult to relate a resolution that is inherently dependent of the instrument to a physical quantity the timescale of the neutron-(magnon or phonon) interaction that is universal.

Please provide references related to the topic.

Topological spin structure or skyrmion is really a hot topic since discovered from neutron scattering in MnSi from 2009. While magnetic bubble domain is found much earlier in many materials with an out of plane anisotropy. In principle the magnetic bubble domain (with the size around several micrometer) may also show the same topological effect as the skyrmion(with the size around 100nm) if the spin structure changes in all x, y, and Z direction in the domain wall(which is not thin compred to the bubbles). Is that true?

Besides, according to:"Phys. Rev. Lett. 105, 197202", dipolar dipolar interaction can induce giant skyrmions which is similar to the bubbles. I want to ask: "Is the magnetic bubble domain a topological spin structure? "

For the typical out of plane anisotropy materials, during the spin rotation from one side to the other, it will form some nucleation points in the beginning and some pinning points which really need high field to rotate(a tail structure in the hysteresis). Are the nucleation and pinning points topological spin structures?

Low Temperature MFM or faraday microscopy will help to see the domain structure, is anyone know where I can perform such measurements?

Thank you very much for the help!

Traditionally neutron scattering is used to investigate magnetic properties of the condensed matter. This is because of strong interaction of neutron spin with the unpaired electron spin. X-rays being electromagnetic waves interact also with unpaired electrons. The interaction strength however is much smaller compared to that of neutrons. This should not be a great drawback because of the very high photon flux of the modern synchrotron sources and this flux is getting higher and higher. So far two magnetism sensitive X-ray methods have become quite useful, viz. X-ray magnetic scattering and X-ray magnetic circular dichroism (XMCD). But other X-ray spectroscopic techniques could also be sensitive to magnetism. Can anyone illuminate me about the modern developments in these fields?

In Monte Carlo simulation dedicated to criticality study of TRIGA reactor, thermal neutrons scattering of graphite is very important. Such data are calculated by THERMR module of NJOY99 data processing code. ENDF-B7.1 TSL data are treated and the obtained results show that coherent elastic scattering is represented as cumulative probability instead of cross section. However inelastic scattering is reproduced correctly and agree very well with values given by NEA JANIS code.

The results are attached to this message.

To solve the Schrödinger equation using the Impulse Approximation by Fermi Pseudopotential

I would like to measure the residual stress in a steel sample using time-of-flight (TOF) neutron diffraction. The collimators have an angular range of say 30 degrees when viewed from a plan view. Does this also mean that there is a similar vertical angular range for the collimator which makes the diffracted neutron beam a cone-like shape from the scanned gauge volume?

Why is charge ordering not possible in large-bandwidth manganites, e.g. the case of La1-xSrxMnO3. Is it due to its highly symmetric (i.e. untitled cubic/tetragonal) crystal structure, or is it something else?

Hexagonal manganites RMnO3 (R = Y, Dy, Ho, Er, Tm, Lu etc.) are multiferroic materials with ferroelectric transition at about 1000 K whereas the magnetic transition is at about 100 K. Unlike the orthorhombic manganites, here the cause of ferroelectricity is geometric and is not due to the magnetic ordering through inverse D-M effect. These hexagonal manganites show strong magnetostriction of the lattice parameters (external magnetostriction) near the magnetic phase transition and this can be easily measured by NPD or by XRPD. We have measured the external magnetostriction by NPD on D20 at ILL. But our attempt to measure small displacements in atomic coordinates and bond distances below T_N (internal magnetostriction) did not give any conclusive results from these NPD data. The inherent problem is probably the strong correlations between magnetic and structural parameters for the magnetic structure with propagation vector k = 0. For these structures, the magnetic reflections are on top of nuclear reflections and give rise to strong correlations. We tried to solve the problem by measuring neutron diffraction intensities up to a very high Q with a diffractometer (POWGEN) on a spallation source (SNS) and refine the magnetic structure with the low-Q data and the nuclear structure with high-Q data, but even this strategy did not succeed. Has anyone any better suggestions or explanations?

The "incoherent approximation" is used In many papers relating to thermal neutron scattering, but can you give one that gives detailed information why they use this approximation. Do you know the origin?