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src/sas/perspectives/calculator/media/resolution_calculator_help.rst
rec392464 rbc9a0e1 3 3 .. This is a port of the original SasView html help file to ReSTructured text 4 4 .. by S King, ISIS, during SasView CodeCamp-III in Feb 2015. 5 6 .. |pi| unicode:: U+03C0 7 .. |lambda| unicode:: U+03BB 8 .. |Ang| unicode:: U+212B 5 9 6 10 Q Resolution Estimator … … 10 14 ----------- 11 15 12 This tool is to approximately estimate the resolution of Q based on the SAS13 instrumental parameter values assuming that the detector is flat and vertical14 to the incident beam direction.16 This tool is approximately estimates the resolution of Q from SAS instrumental 17 parameter values assuming that the detector is flat and normal to the 18 incident beam. 15 19 16 20 .. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ … … 19 23 ------ 20 24 21 1. Select the source and source type (Monochromatic or TOF). Note that the 22 computational difference between the sources is only the gravitational 23 contribution due to the mass. 25 1) Select *SAS Resolution Esimator* from the *Tool* menu on the SasView toolbar. 24 26 25 2 . Change the default values of the instrumental parameters as desired.27 2) Select the source (Neutron or Photon) and source type (Monochromatic or TOF). 26 28 27 3. The input formats of wavelength and its spread (=FWHM/wavelength) depend on 28 the source type.For monochromatic wave, the inputs are just one values as shown 29 with the defaults.For TOF, the min and max values should be separated by "-" 30 to describe the wavelength band range. Optionally, the input of the wavelength 31 (NOT of the wavelength spread) could be extended by adding "; --" where the -- 32 is the number of the bins for the numerical integration. Otherwise, the 33 default value "10" bins will be used. The same number of bins will be used 34 for the corresponding wavelength spread in either cases. 29 *NOTE! The computational difference between the sources is only the 30 gravitational contribution due to the mass of the particles.* 35 31 36 4. For TOF, the default wavelength spectrum is flat. The custom spectrum file 37 (with 2 column text: wavelength(A) vs. intensity) can also be loaded by 38 selecting "Add new" in the combobox. 32 3) Change the default values of the instrumental parameters as required. Be 33 careful to note that distances are specified in cm! 39 34 40 5. Once set all the input values, click the compute button. Depending on 41 computation loads the calculation time will vary. 35 4) Enter values for the source wavelength(s) and its spread (= FWHM / wavelength). 36 37 For monochromatic sources, the inputs are just one value. For TOF sources, 38 the minimum and maximum values should be separated by a '-' to specify a 39 range. 40 41 Optionally, the wavelength (BUT NOT of the wavelength spread) can be extended 42 by adding '; nn' where the 'nn' specifies the number of the bins for the 43 numerical integration. The default value is nn = 10. The same number of bins 44 will be used for the corresponding wavelength spread. 42 45 43 6. 1D and 2D dQ will be displayed in the text-box at the bottom of the panel. 44 Two dimensional resolution weight distribution (2D elliptical Gaussian 45 function) will also be displayed in the plot panel even if the Q inputs are 46 outside of the detector limit. The red lines indicate the limits of the 47 detector (if a green lines appear (for TOF), it indicates the limits of the 48 maximum q range for the largest wavelength due to the size of the detector). 49 Note that the effect from the beam block is ignored, so in the small q region 50 near the beam block 46 5) For TOF, the default wavelength spectrum is flat. A custom spectral 47 distribution file (2-column text: wavelength (|Ang|\) vs Intensity) can also 48 be loaded by selecting *Add new* in the combo box. 51 49 52 [ie., q<2*pi*(beam block diameter) / (sample to detector distance) / lamda_min] 50 6) When ready, click the *Compute* button. Depending on the computation the 51 calculation time will vary. 53 52 54 the variance is slightly under estimated. 53 7) 1D and 2D dQ values will be displayed at the bottom of the panel, and a 2D 54 resolution weight distribution (a 2D elliptical Gaussian function) will also 55 be displayed in the plot panel even if the Q inputs are outside of the 56 detector limit (the red lines indicate the limits of the detector). 57 58 TOF only: green lines indicate the limits of the maximum Q range accessible 59 for the longest wavelength due to the size of the detector. 60 61 Note that the effect from the beam block/stop is ignored, so in the small Q 62 region near the beam block/stop 55 63 56 7. The summary can be accessed by clicking the 'light-bulb' icon at the bottom 57 of the SasView main window. 64 [ie., Q < 2*|pi|\*(beam block diameter) / (sample-to-detector distance) / |lambda|\_min] 65 66 the variance is slightly under estimated. 67 68 8) A summary of the calculation is written to the SasView *Console* at the 69 bottom of the main SasView window. 58 70 59 71 .. image:: resolution_tutor.gif … … 68 80 .. image:: q.gif 69 81 70 In the limit of the small angle, the variance of q in the firstorder71 approximation is82 In the small-angle limit, the variance of Q is to a first-order 83 approximation 72 84 73 85 .. image:: sigma_q.gif 74 86 75 In summary, the geometric and gravitational contributions depending on the 76 shape of each factors can be expressed as shown the table. 87 The geometric and gravitational contributions can then be summarised as 77 88 78 89 .. image:: sigma_table.gif 79 90 80 Finally, we use a Gaussian functionto describe the 2D weighting distribution81 of the uncertainty in q.91 Finally, a Gaussian function is used to describe the 2D weighting distribution 92 of the uncertainty in Q. 82 93 83 94 .. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ … … 85 96 References 86 97 ---------- 87 D.F.R. Mildner and J.M. Carpenter, J. Appl. Cryst. 17, 249-256 (1984)88 98 89 D.F.R. Mildner, J.M. Carpenter and D.L. Worcester, J. Appl. Cryst. 19, 311-319 90 (1986) 99 D.F.R. Mildner and J.M. Carpenter 100 *J. Appl. Cryst.* 17 (1984) 249-256 101 102 D.F.R. Mildner, J.M. Carpenter and D.L. Worcester 103 *J. Appl. Cryst.* 19 (1986) 311-319 104 105 .. ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ 106 107 .. note:: This help document was last changed by Steve King, 19Feb2015
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