Changeset 3b67c30 in sasview for src/sas/perspectives
- Timestamp:
- May 2, 2015 2:00:11 PM (10 years ago)
- 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
- File:
-
- 1 edited
Legend:
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src/sas/perspectives/fitting/media/mag_help.rst
rce62e75 r3b67c30 36 36 * *ParallelepipedModel* 37 37 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. 38 In general, the scattering length density (SLD, = |beta|) in each region where the 39 SLD is uniform, is a combination of the nuclear and magnetic SLDs and, for polarised 40 neutrons, also depends on the spin states of the neutrons. 41 42 For magnetic scattering, only the magnetization component, *M*\ :sub:`perp`, 43 perpendicular to the scattering vector *Q* contributes to the the magnetic 44 scattering length. 43 45 44 46 .. image:: mag_vector.bmp … … 48 50 .. image:: dm_eq.gif 49 51 50 where /gamma/ = -1.913 the gyromagnetic ratio, /mu/B is the Bohr magneton, r051 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. 52 where |gamma| = -1.913 is the gyromagnetic ratio, |mu|\ :sub:`B` is the 53 Bohr magneton, *r*\ :sub:`0` is the classical radius of electron, and |sigma| 54 is the Pauli spin. 53 55 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 56 Assuming that incident neutrons are polarized parallel (+) and anti-parallel (-) 57 to the *x'* axis, the possible spin states after the sample are then 57 58 58 Non-spin flips: (+ +) and (- -) 59 Spin flips: (+ -) and (- +) 59 No spin-flips (+ +) and (- -) 60 61 Spin-flips (+ -) and (- +) 60 62 61 63 .. image:: M_angles_pic.bmp 62 64 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 65 If the angles of the *Q* vector and the spin-axis (*x'*) to the *x*-axis are |phi| 66 and |theta|\ :sub:`up`, respectively, then, depending on the spin state of the 67 neutrons, the scattering length densities, including the nuclear scattering 68 length density (|beta|\ :sub:`N`) are 68 69 69 70 .. image:: sld1.gif 70 71 71 for spin-flips 72 when there are no spin-flips, and 72 73 73 74 .. image:: sld2.gif 74 75 75 whe re76 when there are, and 76 77 77 78 .. image:: mxp.gif … … 85 86 .. image:: mqy.gif 86 87 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) 88 Here, *M*\ :sub:`0x`, *M*\ :sub:`0y` and *M*\ :sub:`0z` are the x, y and z components 89 of the magnetization vector given in the laboratory xyz frame given by 90 90 91 91 .. image:: m0x_eq.gif … … 95 95 .. image:: m0z_eq.gif 96 96 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 97 and the magnetization angles |theta|\ :sub:`M` and |phi|\ :sub:`M` are defined in 98 the figure above. 100 99 101 (spin up)/(spin up + spin down) 100 The user input parameters are: 102 101 103 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 =========== ================================================================ 104 110 105 *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. 107 112 108 113 .. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ 114 115 .. note:: This help document was last changed by Steve King, 02May2015
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