Changeset 795 for sans/Dev/trunk/NCNR_User_Procedures/Reduction/SANS/ILL_Utils.ipf

Timestamp:

Apr 4, 2011 12:18:33 PM (11 years ago)

Author:

srkline

Message:

Changes to SANS reduction that apply to other Facilities:

These changes are related to the propagation of errors in 2D, on a
per-pixel basis. These changes only affect the errors that are reported in
the QxQy? ASCII file output. The 1D code is unaffected.

If these changes are not implemented, then errors of zero will be substitued as defaults
for these experimental errors.

Upon data loading, an error matrix, linear_data_error is generated and filled with
error values appropriate for Poisson statistics (not simply sqrt(n)).

4 functions in FACILITY_DataReadWrite.ipf have been added, and they are rather
self-explanatory:

• WriteBoxCountsErrorToHeader?()
• WriteTransmissionErrorToHeader?()
• getBoxCountsError()
• getSampleTransError()

In FACILITY_Utils.ipf, the AttenuatorTransmission?() function now returns
an additional parameter, atten_err, which is one standard deviation of the
attenuator transmission value. It returns a default error=0 (which is
correct if no attenuation is used). Facilities can fill this function in
with their own estimates for the uncertainty in the attenutator transmission.

File:

• sans/Dev/trunk/NCNR_User_Procedures/Reduction/SANS/ILL_Utils.ipf (modified) (3 diffs)

sans/Dev/trunk/NCNR_User_Procedures/Reduction/SANS/ILL_Utils.ipf

@@ -175 +175 @@
 // detStr is passed as TextRead[9] and is an identifier for the detector
 //
-Function DetectorDeadtime(fileStr,detStr)
-        String fileStr,detStr
+// [dateAndTimeStr] is optional, and could be used as a switch for 
+// different historical detector configurations
+Function DetectorDeadtime(fileStr,detStr,[dateAndTimeStr])
+        String fileStr,detStr,dateAndTimeStr
         
         Variable deadtime
         
-// your code here
-deadtime = (2e-6)
+        // your code here
+        deadtime = (2e-6)
 
         return(deadtime)
@@ -922 +924 @@
 // called by Correct.ipf, ProtocolAsPanel.ipf, Transmission.ipf
 //
-Function AttenuationFactor(fileStr,lam,attenNo)
+// atten_err is one std. deviation, passed back by reference
+Function AttenuationFactor(fileStr,lam,attenNo,atten_err)
         String fileStr
-        Variable lam,attenNo
+        Variable lam,attenNo,&atten_err
         
         Variable attenFactor
@@ -930 +933 @@
         
         attenFactor = Attenuators_ILL[attenNo]
-        
+
+        // Change April 2011 - now returns error in atten trans
+        atten_err = 0
+                
 //      print attenfactor