See also compose controls windows
The run composer is the main window of reflred. From here you can view and plot individual data files, and compose them into complete scans. You can access most of the other windows directly from the menu.
The initial list contains data files from the directory/pattern given on the command line, or from the current directory if none was given. You can select a different data set from the choose window (Data... on the menu).
Files are grouped according to the activity of the motors:
It is a slit scan if the beam is straight through but the slit motors are moving.
It is a rocking curve if the incident angle is fixed but the reflected angle is varying.
It is a specular scan if the incident angle matches the reflected angle.
It is a background scan if the incident angle does not match the reflected angle.
Background scans are tagged with + if the reflected angle is greater than the incident angle, or - if the reflected angle is greater than the incident angle.
There are a few rare scan types possible. A height scan is indicated by movement of motor 12 on NG-7. If no motors are moving, but temperature is being recorded then it will be classified as a temperature scan. Similarly for applied field. If nothing is changing then the file is tagged as a time evolution (or a single point slit scan if the beam is straight through).
Shown next to each data file is a box indicating the total range for the data set. The shaded portion of the box indicates the Qz range for that file. The vertical bar indicates a value of Qz = 0, or for Qx = 0 in the case of rocking curves. For slit scans, the data range indicates the slit 1 opening. For temperature scans, time evolution, or height scans, the data range indicates temperature, time or height respectively.
For NG-1 and X-Ray files there is no data column for Qz. Instead Qz is calculated from motor A3 (incident angle) or A4 (incident plus reflected angle). For rocking curves it must be A3 and for specular scans it doesn't matter since A3 is 2*A4. For background scans however either A3 or A4 can be the basis for Qz, with the other being the offset. This is indicated in the file selection tree by the label Background Q(A3) or Background Q(A4). It should be obvious which is correct by comparing the Q range of the background with the Q range of the corresponding specular. Click the label to toggle, or select "Options Background A#" from the menu to change them all. Doing so will change the Q range on the selected files as well, but not on the previously composed scans.
All runs are displayed with the same monitor count, which is the monitor of the first run selected (see monitor). You can scale each run independently using the attenuator window (Attenuator... in the menu), or click "align" to calculate the attenuators automatically. WARNING: the attenuator calculator does not work reliably. Read the details in attenuator.
Note: you cannot combine NG1 runs counted against monitor and time in the same scan. The NG1 monitor is positioned between slit 1 and slit 2, so as slit 1 opens, the monitor rate increases which means the counting time decreases within the run. When counting against time, the counting time is fixed within the run. The correct way to handle this is to reduce the monitor and time data separately then join the reduced lines.
NG-7 data is scaled by monitor count when it is loaded. A dead time correction is applied to the monitor count, which is linearly interpolated from the data in the file reflectivity/NG7monitor.cal. You can see the calibration data by opening the Tcl console and typing
load_NG7_monitor_calibration set NG7_monitor_calibration
Since the NG7 monitor does not count every neutron, there will be a detector to monitor ratio that needs to be measured. Once measured, this can be entered on the reduce screen as a transmission coefficient, entered as an attenuator, or saved as an ICP file and used as a slit scan. Since the detector to monitor ratio is not a constant especially at low Q, a slit scan taken at several points will give the best results.
Once you have selected your sequence of files, click "Accept" to average them into a complete scan. The resulting average will be displayed as a separate scan line. Click on the legend entry to hide it, or click "Clear" to remove it. The "Clear" button first removes the selected runs, then removes the scans. Scans are available for further processing in the reduce window (Reduce... in the menu).
For polarized beam, you will have to select A, B, C and D separately. Once you accept, separate lines will be created for each index.