1.2.5. - Scans
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.