Changes between Initial Version and Version 1 of Tutorials/KU/SAS


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Aug 13, 2018 3:48:43 PM (4 years ago)
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ajj
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  • Tutorials/KU/SAS

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     1= Exercise 9 - SANS Data Analysis using !SasView = 
     2 
     3||= **Table of Contents** =|| 
     4|| [#intro Introduction] || 
     5|| [#section1 1. Familiarisation with SasView] || 
     6|| [#section2  2. Exploring geometrical models] || 
     7||   [#section21 2.1 Spheres] || 
     8||   [#section22 2.2 Cylinders] || 
     9||   [#section23 2.3 Polydispersity] || 
     10||   [#section24 2.4 Resolution] || 
     11 
     12 
     13== [=#intro Introduction] == 
     14This exercise will introduce you to analysing SANS data using geometrical models in !SasView. In the first lab session you will look at how different shapes produce different scattering patterns, and how the model parameters affect the scattering pattern. In the second lab session you will then load some real SANS data and attempt to fit models to the data in !SasView. 
     15 
     16This first exercise is divided into 2 sections: 
     17 
     181. [#section1 Familiarisation with SasView] 
     192. [#section2  Exploring geometrical models] 
     20 
     21Before beginning the exercise, you must first ensure that !SasView is installed. If you have not done so already, follow [wiki:KEMM37/InstallSasView these installation instructions]. 
     22 
     23Tasks you should perform are shown thus: 
     24{{{ 
     25#!div style="background: lightblue" 
     26**TASK 0:** Install !SasView. Installation instructions can be found here: [wiki:KEMM37/InstallSasView] 
     27}}} 
     28 
     29 
     30 
     31== [=#section1 1.] Familiarisation with !SasView == 
     32{{{ 
     33#!div style="background: lightblue" 
     34[=#task1 **TASK 1:**] Start !SasView. The application should open and look something like the images below. 
     35}}} 
     36 
     37|| [[Image(kemm37_sasviewmac.png, 500px)]] || [[Image(kemm37_sasviewwin.png, 500px)]] || 
     38|| !SasView 4.1.2 on Mac OS || !SasView 4.1.2 on Windows 10 || 
     39 
     40 
     41The !SasView user interface contains 4 main areas: 
     42* The Data Explorer 
     43  * This is where data is loaded and can then be plotted or sent to the various types of analysis. 
     44  * Models not associated with data (called "Theories" in !SasView) can be plotted and converted to datasets. 
     45* The Analysis Panel (which defaults to showing Fitting) 
     46  * This is where you do the work of analysing data or generating theories 
     47  * !SasView currently supports four analysis tools: 
     48     * Fitting - for theory generation or model fitting to 1D and 2D SANS, SAXS, or SESANS data 
     49     * P(r) Inversion - for converting I(Q) to P(r) 
     50     * Invariant - for calculating the scattering invariant from a 1D data set 
     51     * Correlation Function - for performing a correlation function analysis of a 1D data set 
     52* The plot windows (which appear when something is plotted) 
     53* The menus, toolbar, and status area. 
     54 
     55The capabilities of !SasView are described in more detail in the [http://www.sasview.org/docs/user/user.html  application documentation] with links to the relevant parts of the documentation available as "Help" buttons in each part of the GUI. 
     56 
     57{{{ 
     58#!div style="background: lightblue" 
     59[=#task2 **TASK 2:**] Briefly familiarise yourself with !SasView panels, menus and documentation. Try changing to different analysis tools.  
     60}}} 
     61 
     62 
     63 
     64== [=#section2 2.  Exploring geometrical models] == 
     65In this part of the exercise, you will plot the scattering patterns calculated using different geometrical models and explore the effect that the model parameters have on the scattering. 
     66 
     67{{{ 
     68#!div style="background: lightblue" 
     69[=#task3 **TASK 3:**] Restart !SasView 
     70 
     71Before starting this part of the exercise, you should have a clean !SasView instance. Quit !SasView and restart it. 
     72}}} 
     73 
     74 
     75=== [=#section21 2.1 Spheres] === 
     76 
     77{{{ 
     78#!div style="background: lightblue" 
     79[=#task4 **TASK 4:**] Plot the scattering from a collection of spherical particles 
     80 
     81In the Fit Panel, there should be a single tab labelled "Fitpage1". In that tab, choose the model category "Sphere" and the model "sphere". 
     82}}} 
     83 
     84The fit panel and a plot panel that appears should look like the following: 
     85 
     86[[Image(kemm37_fitpage1_1.png, 500px)]] [[Image(kemm37_sphere.png, 500px)]] 
     87 
     88{{{ 
     89#!div style="background: lightblue" 
     90[=#task5 **TASK 5:**] Change the parameters and note the changes in the scattering pattern. 
     91 
     92In the "Fitpage1" tab, scroll down to the bottom and: 
     93 * Increase "Npts" to 200 
     94 * Check the "Log" box 
     95 
     96Next, click "Compute" 
     97 
     98This will improve the fidelity of the modelled curve. 
     99 
     100Now scroll back up and try adjusting the various model parameters one at a time. Pressing enter after changing a value should recalculate the scattering. If not, use the Compute button. 
     101 
     102What effect do the each of the parameters have on the scattering curve? 
     103* scale 
     104* background 
     105* sld and sld_solvent 
     106* radius 
     107}}} 
     108 
     109 
     110=== [=#section22 2.2 Cylinders] === 
     111 
     112{{{ 
     113#!div style="background: lightblue" 
     114[=#task6 **TASK 6:**] Plot the scattering from a collection of cylindrical particles 
     115 
     116From the "Fitting" menu, select "New Fit Page". 
     117 
     118In the Fit panel, a new tab labelled "Fitpage2" should appear. In that tab, choose the model category "Cylinder" and the model "cylinder". 
     119}}} 
     120 
     121The fit panel and a plot panel that appears should look like the following: 
     122 
     123[[Image(kemm37_fitpage2_1.png, 500px)]][[Image(kemm37_cylinder.png, 500px)]] 
     124 
     125{{{ 
     126#!div style="background: lightblue" 
     127[=#task7 **TASK 7:**] Change the parameters and note the changes in the scattering pattern. 
     128 
     129In the "Fitpage2" tab, scroll down to the bottom and: 
     130 * Increase "Npts" to 200 
     131 * Check the "Log" box 
     132 
     133Next, click "Compute" 
     134 
     135This will improve the fidelity of the modelled curve. 
     136 
     137Now scroll back up and try adjusting the various model parameters one at a time. Pressing enter after changing a value should recalculate the scattering. If not, use the Compute button. 
     138 
     139What effect do the each of the parameters have on the scattering curve? 
     140* scale 
     141* background 
     142* sld and sld_solvent 
     143* radius 
     144* length 
     145}}} 
     146 
     147 
     148=== [=#section23 2.3 Polydispersity] === 
     149 
     150{{{ 
     151#!div style="background: lightblue" 
     152[=#task8 **TASK 8:**] Apply polydispersity to model parameters 
     153 
     154Select the "Fitpage1" tab that contains the sphere model. 
     155 
     156Find the section labelled "Polydispersity and Orientational Distribution" 
     157 
     158- Click the "On" radio button and a new section should appear labelled "Distribution of radius". 
     159 
     160- Enter a value for "PD[ratio]" between 0.0 and 1.0 - this is the polydispersity defined as sigma_r/r. 
     161 
     162What effect does varying the polydispersity have on the scattering curve? 
     163 
     164Repeat the exercise for the cylinder model in "Fitpage2" 
     165 
     166}}} 
     167 
     168 
     169=== [=#section24 2.4 Resolution] === 
     170{{{ 
     171#!div style="background: lightblue" 
     172[=#task9 **TASK 9:**] Apply resolution functions to your model 
     173 
     174Select the "Fitpage1" tab that contains the sphere model. 
     175 
     176Find the section labelled "Polydispersity and Orientational Distribution" 
     177 
     178- Click the "Off" radio button and the polydispersity section should disappear 
     179 
     180Find the section labelled "Set Instrumental Smearing" 
     181 
     182- Click on the "Custom Pinhole Smear" radio button and a data entry box should appear. 
     183 
     184- Enter a value for the percentage dQ/Q that is applied to the model - start with a value of 10.  
     185 
     186- Try various values of dQ/Q ranging from 1% to 50%. 
     187 
     188What effect does this have on the scattering curve? 
     189 
     190}}} 
     191 
     192 
     193== What's Next? == 
     194You can now move on to the second lab session looking at fitting of data : [wiki:KEMM37/Lab1B Lab 1B Data Fitting]