​Absorption of neutrons by the sample and containers are calculated using the formalism of Paalman-Pings [1]. In this formalism absorption corrections from flat plate containers are calculated using analytical formula, but cyclindrical and annular cells are calculated neumerically. In the QENS experiments on liquid samples annular containers are used for most of the cases,. In those cases calculations of corrections due to absorption of neutrons should be done for annular containers. 

To calculate corrections follow steps as described below:

• Click on  Indirect Corrections on the  interface menu.
  
• Click on Calculate Paalman-Pings tab
  
• Select input file type from the drop down list, either Workspace or File.
  
• Load the reduced Input File with extensions _red  for reduced file or _sqw for a S(q,w) file
  
• Load the reduced Input File with extensions _red  ​or _sqw for the empty container (Optional). 
  
• Select EMode as Indirect from the drop-down menu in the Corrections Details section. Efixed should be autometically populated from the instrument parameters data already loaded as Sample File. All other options in this section keep as default, those will not be used for absorption calculations in QENS. 
  
• In the section of Shape Details select the shape of the sample as Annular, Cylinder or Flat Plate. Give all parameters required for the selected sample container. Your instrument scientist can help to find out those parameters. 
  
• Keep step sizes as default value 0.002.
  
• In the section od Sample Details give the mass density of the sample in unit of gm/cm³ and the checal formula of the sample. In the description of chemical formula put the number of atoms as a number just after the symbol of the element and give a hyphen in bewteen two elements. In this formulas H2-O represents water. For more details on how to supply chemical formula for isotopes and fractional number of atoms see the documentation here​. 
• Supply also details of materials used in containers following the same procedures as Sample Details described above in the section of Can Details.
• Click on Run to calculate the correction factor using Paalman-Pings methodology. 
  
  

• ​Select options for plotting as Wavelength, or Angles, or both to get output against wavelength of incident neutrons, Q of the instrument or both, respectively. The absorption corrections for sample, container and sample plus containes are given as A_ss, A_cc, A_sc, respectively.
• Workspaces created can be saved as Nexus file using the button Save. 
  
  

[1]  H H Paalman & C J Pings, J Appl Phys 33 2635 (1962)​

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