Differences

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--- playground:playground [2012/11/09 14:05] – auchemistry
+++ playground:playground [2024/01/23 07:31] – external edit 127.0.0.1
@@ Line 1: / Line 1: @@
-====== Andrew Unwin Was Not Here ======
+====== PlayGround ======
-[[
-Test page]][[http://example.com|External Link]].
+Play with any wiki page tests you like here.
-Here is some text
-Here is some topas text:
+====== Lobanov Absorption Correction for TOF Neutrons ======
-<code topas>
-'a comment
-  prm !zero 0
-</code>
+Description: This is the absorption correction used in GSAS formatted for TOF neutron diffraction
+Comment: Lobanov absorption macro with calculated lambda for wavelength dependence of mu (as per GSAS manual). The macro can be edited to function with CW data with 'Lam' replacing 'lambda' and 'Sin(Th)' replacing 'sintheta'
-====== PlayGround ======
+Contributed by: Pamela Whitfield
-Welcome to the PlayGround page. Please use this space to practice putting things into dokuwiki. In order to do this press the <html><span style="color:blue;">edit this page</span></html> button in the top toolbar of this page. After editing press <html><span style="color:blue;">save</span></html> and your work will be put onto this dokuwiki page.
- --- //[[john.evans@durham.ac.uk|John Evans]] 2009/08/25 14:20//
-\\ For more help with creating wiki pages go to [[http://dokuwiki.org/syntax]].
+Lf is the flightpath and two_theta the detector angle. The refinable parameter under each dataset is 'mu'
-<html>
-<div id="cse" style="width: 100%;">Loading</div>
-<script src="http://www.google.com/jsapi" type="text/javascript"></script>
-<script type="text/javascript">
-   google.load('search', '1');
-   google.setOnLoadCallback(function(){
-      new google.search.CustomSearchControl('013529302060368774732:y9u5ftshwew').draw('cse');
-   }, true);
-</script>
-</html>
+POWGEN flightpath is 60 metres with data focussed into a single dataset at 90 degrees.
-----
-<code topas>
+Absorption is angle-dependent. For more conventional TOF instruments with multiple detector banks such as HRPD, two_theta (and maybe Lf) will differ for each bank by using 'local' variables as opposed to global 'prm' variables, e.g.
-'some text
-prm !a 0
-continue_after_convergence
-</code>
+<code vb>
+/* this is a comment */
+' this is a quotation comment
+   TOF_XYE....
+    local !two_theta 145
+    local !Lf 25
+    local mu 0 min 0
+    Abs_Lobanov
+   TOF_XYE....
+    local !two_theta 90
+    local !Lf 26
+    local mu 0 min 0
+    Abs_Lobanov
+    macro Abs_Lobanov
+    {
+    prm !Lf 60.183 /* POWGEN 90 degree flightpath */
+    prm !h_bar 6.626176e-34 /* Plank's constant */
+    prm !m_n 1.67495e-27 /* neutron mass */
+    prm !td_const = 10^4 h_bar/(m_n Lf);
+    local !sintheta = Sin(Deg_on_2 two_theta);
+    local !lambda = Xo 10^4 h_bar/(m_n Lf);
+    local !k0 = 1.697653;
+    local !k1 = (25.99978 - (0.01911 sintheta^0.5)Exp(-0.024514 sintheta^2)) + 0.109561 sintheta - 26.0456;
+    local !k2 = -0.02489 - (0.39499 sintheta^2) + (1.219077 sintheta^3) - (1.31268 sintheta^4) + (0.871081 sintheta^5) - (0.2327 sintheta^6);
+    local !k3 = 0.003045 + (0.018167 sintheta^2) - (0.03305 sintheta^4);
+    local !k4 = 1.433902 + (11.07504 sintheta^2) - (8.77629 sintheta^4) + (10.02088 sintheta^6) - (3.36778 sintheta^8);
+    local !k5 = ((0.013869 - 0.01249 sintheta^2)Exp(3.27094 sintheta^2)) + ((0.337894 + (13.77317 sintheta^2))/((1 + 11.53544 sintheta^2)^1.555039));
+    local !k6 = (1.933433 / (1 + 23.12967 sintheta^2)^1.686715) - 0.13576 sintheta + 1.163198;
+    local !k7 = 0.044365 - (0.04259/((1 + 0.41051 sintheta^2)^148.4202));
+    scale_pks = If( (mu*lambda) < 3, Exp(-k0 (mu*lambda) - k1 (mu*lambda)^2 - k2 (mu*lambda)^3 - k3 (mu*lambda)^4),
+				Exp((k4 - k7/(1 + k5 ((mu*lambda)-3))^k6)+k7)
+				);
+    }
+</code>