Changeset 3b67c30 in sasview


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Timestamp:
May 2, 2015 12:00:11 PM (9 years ago)
Author:
smk78
Branches:
master, ESS_GUI, ESS_GUI_Docs, ESS_GUI_batch_fitting, ESS_GUI_bumps_abstraction, ESS_GUI_iss1116, ESS_GUI_iss879, ESS_GUI_iss959, ESS_GUI_opencl, ESS_GUI_ordering, ESS_GUI_sync_sascalc, costrafo411, magnetic_scatt, release-4.1.1, release-4.1.2, release-4.2.2, release_4.0.1, ticket-1009, ticket-1094-headless, ticket-1242-2d-resolution, ticket-1243, ticket-1249, ticket885, unittest-saveload
Children:
765e47c
Parents:
f256d9b
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  • src/sas/perspectives/fitting/media/mag_help.rst

    rce62e75 r3b67c30  
    3636*  *ParallelepipedModel* 
    3737 
    38 In general, the scattering length density (SLD) in each regions where the  
    39 SLD (=/beta/) is uniform, is a combination of the nuclear and magnetic SLDs and  
    40 depends on the spin states of the neutrons as follows. For magnetic scattering,  
    41 only the magnetization component, *M*perp, perpendicular to the scattering  
    42 vector *Q* contributes to the the magnetic scattering length. 
     38In general, the scattering length density (SLD, = |beta|) in each region where the 
     39SLD is uniform, is a combination of the nuclear and magnetic SLDs and, for polarised 
     40neutrons, also depends on the spin states of the neutrons. 
     41 
     42For magnetic scattering, only the magnetization component, *M*\ :sub:`perp`, 
     43perpendicular to the scattering vector *Q* contributes to the the magnetic 
     44scattering length. 
    4345 
    4446.. image:: mag_vector.bmp 
     
    4850.. image:: dm_eq.gif 
    4951 
    50 where /gamma/ = -1.913 the gyromagnetic ratio, /mu/B is the Bohr magneton, r0  
    51 is the classical radius of electron, and */sigma/* is the Pauli spin. For  
    52 polarised neutron, the magnetic scattering is depending on the spin states.  
     52where |gamma| = -1.913 is the gyromagnetic ratio, |mu|\ :sub:`B` is the 
     53Bohr magneton, *r*\ :sub:`0` is the classical radius of electron, and |sigma| 
     54is the Pauli spin. 
    5355 
    54 Let's consider that the incident neutrons are polarized parallel (+)/ 
    55 anti-parallel (-) to the x' axis (See both Figures above). The possible  
    56 out-coming states then are + and - states for both incident states 
     56Assuming that incident neutrons are polarized parallel (+) and anti-parallel (-) 
     57to the *x'* axis, the possible spin states after the sample are then 
    5758 
    58 Non-spin flips: (+ +) and (- -) 
    59 Spin flips:     (+ -) and (- +) 
     59No spin-flips (+ +) and (- -) 
     60 
     61Spin-flips    (+ -) and (- +) 
    6062 
    6163.. image:: M_angles_pic.bmp 
    6264 
    63 Now, let's assume that the angles of the *Q*  vector and the spin-axis (x')  
    64 against x-axis are /phi/ and /theta/up, respectively (See Figure above). Then,  
    65 depending upon the polarisation (spin) state of neutrons, the scattering length  
    66 densities, including the nuclear scattering length density (/beta/N) are given  
    67 as, for non-spin-flips 
     65If the angles of the *Q* vector and the spin-axis (*x'*) to the *x*-axis are |phi| 
     66and |theta|\ :sub:`up`, respectively, then, depending on the spin state of the 
     67neutrons, the scattering length densities, including the nuclear scattering 
     68length density (|beta|\ :sub:`N`) are 
    6869 
    6970.. image:: sld1.gif 
    7071 
    71 for spin-flips 
     72when there are no spin-flips, and 
    7273 
    7374.. image:: sld2.gif 
    7475 
    75 where 
     76when there are, and 
    7677 
    7778.. image:: mxp.gif 
     
    8586.. image:: mqy.gif 
    8687 
    87 Here, the M0x, M0y and M0z are the x, y and z components of the magnetization  
    88 vector given in the xyz lab frame. The angles of the magnetization, /theta/M  
    89 and /phi/M as defined in the Figure (above) 
     88Here, *M*\ :sub:`0x`, *M*\ :sub:`0y` and *M*\ :sub:`0z` are the x, y and z components 
     89of the magnetization vector given in the laboratory xyz frame given by 
    9090 
    9191.. image:: m0x_eq.gif 
     
    9595.. image:: m0z_eq.gif 
    9696 
    97 The user input parameters are M0_sld = DMM0, Up_theta = /theta/up,  
    98 M_theta = /theta/M, and M_phi = /phi/M. The 'Up_frac_i' and 'Up_frac_f' are  
    99 the ratio 
     97and the magnetization angles |theta|\ :sub:`M` and |phi|\ :sub:`M` are defined in 
     98the figure above. 
    10099 
    101 (spin up)/(spin up + spin down) 
     100The user input parameters are: 
    102101 
    103 neutrons before the sample and at the analyzer, respectively. 
     102===========   ================================================================ 
     103 M0_sld        = *D*\ :sub:`M` *M*\ :sub:`0` 
     104 Up_theta      = |theta|\ :sub:`up` 
     105 M_theta       = |theta|\ :sub:`M` 
     106 M_phi         = |phi|\ :sub:`M` 
     107 Up_frac_i     = (spin up)/(spin up + spin down) neutrons *before* the sample 
     108 Up_frac_f     = (spin up)/(spin up + spin down) neutrons *after* the sample 
     109===========   ================================================================ 
    104110 
    105 *Note:* The values of the 'Up_frac_i' and 'Up_frac_f' must be in the range 
    106 between 0 and 1. 
     111*Note:* The values of the 'Up_frac_i' and 'Up_frac_f' must be in the range 0 to 1. 
    107112 
    108113.. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ 
     114 
     115.. note::  This help document was last changed by Steve King, 02May2015 
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