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Contents → USER MANUAL AND TUTORIALS → Beginner's Guide to Diffractometer Operation → Scans

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Scans in spec are built of macros. Many different standard scans are available. Absolute-position motor scans such as ascan, a2scan and a3scan move one, two or three motors at a time. Relative-position motor scans are lup (or dscan), d2scan and d3scan. The relative-position scans all return the motors to their starting positions after the last point. Two motors can be scanned over a grid of points using the mesh scan.

Simple reciprocal space scans are hscan, kscan and lscan. The hklscan macro moves the diffractometer along an arbitrary straight line in reciprocal space. Scans such as hkcircle or hkradial describe other trajectories. The hklmesh scan measures intensities over a grid of reciprocal-space points.

If you do not know the arguments for a scan or how a scan is used, you can call up its usage by typing its name with no arguments.

1.FOURC> ascan
Usage:  ascan motor start finish intervals time

2.FOURC> hscan
Usage:  hscan start finish intervals time

3.FOURC> 

When the program does a scan such as hscan, the following happens: the program waits for motors to stop moving, calculates (H,K,L) for the current position and then scans H, holding K and L fixed for a reciprocal space scan along the H direction.

1.FOURC> hscan .9 1.1 20 1
Total 21 points, 21 seconds

Scan  20   Thu Feb 09 20:04:30 2017   file = cu110/90_01_31.a
hklscan 0.9 1.1 0 0 0 0 20 1
  #          H          K          L Detector  Monitor    Seconds
  0        0.9          0          0     2604    38939          1
  1       0.91          0          0     3822    38820          1
  2       0.92          0          0     5295    39034          1
  3       0.93          0          0     7259    38789          1
  4       0.94          0          0     9298    38804          1
  5       0.95          0          0    11505    38909          1
  6       0.96          0          0    13907    38821          1
  7       0.97          0          0    16022    39110          1
  8       0.98          0          0    17603    38839          1
  9       0.99          0          0    18834    38950          1
 10          1          0          0    19103    38917          1
 11       1.01          0          0    18701    39013          1
 12       1.02          0          0    17652    39135          1
 13       1.03          0          0    16011    38836          1
 14       1.04          0          0    13848    38901          1
 15       1.05          0          0    11585    38933          1
 16       1.06          0          0     9302    39022          1
 17       1.07          0          0     7237    39205          1
 18       1.08          0          0     5324    38957          1
 19       1.09          0          0     3780    38801          1
 20        1.1          0          0     2580    38975          1

Peak at 1 is 19103   FWHM at 1 is 0.05   COM is 1
Sum = 231272  Ave.Mon./Time = 38921  Ave.Temp. = 0C
28 second

2.FOURC> 

The output shown is what would generally appear on the screen. More detailed output is sent to the printer. Also, a complete scan header and the data points are stored in the data file. A rudimentary plot can be produced on the printer at the end of the scan. Typing splot will produce a plot of the data on the screen. Typing pts will list the data on the screen.

The setplot macro configures how the data will be displayed during and at the conclusion of scans.

1.FOURC> setplot

Do real-time screen plots during scans (NO)? y
Do screen plot after scan (YES)? <return>
Do printer plot after scan (NO)? y

2.FOURC> 

Scans can be aborted by typing ^C. Typing scan_on restarts an aborted scan at the current point.

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