Chemistry Reference
In-Depth Information
TABLE 5.1 Specifications and Applications of Sample Stages
Two-Position
Chi
Quarter-Circle
Cradle
Stage
Fixed Chi
XYZ Stage
Specifications
v
180
-þ180
(from the base goniometer)
35.26
0 and 35.26
7
-þ101
c
0
360
continue
360
continue
360
continue
f
0
X
N/A
N/A
50-þ50mm
40-þ40mm
Y
N/A
N/A
50-þ50mm
40-þ40mm
Z
N/A
N/A
50-þ50mm
1-þ2mm
Applications
Phase ID
Yes, capillary
Yes, capillary
Yes
Yes
Stress
Yes
Yes (biaxial)
Yes
Yes (biaxial)
Texture
Yes
Yes
Yes (limited)
Yes (best)
Mapping
No
No
Yes
Yes
Microdiffraction
Yes
Yes
Yes
Yes
Sample size
Small
Small
Large
Medium
Sample number
Single
Single
Multiple
Multiple
Auto alignment
No
No
Yes
Yes
same order in the sequence. The c-axis is a right-handed rotation about a horizontal
axis within the diffractometer plane. The orientation of the c-axis is determined by the
v angle; therefore, it ismounted directly on thev circle. The orientation of thef-axis is
determined by bothc andv, therefore, it ismounted on top of the c circle. Thef-axis is
always perpendicular to the c-axis. All three rotation axes cross at the instrument
center. The three translations should only bring different part of the sample into the
instrument center, but not move any axis away from the instrument center. By
definition, the orientation of the sample coordinates varies with any rotation axis,
so the XYZ stage should be mounted last in the stacking sequence, that is, on top of the
f-axis. Since the Z-axis overlapswith thef-axis, it is possible to build thef-axis above
the Z-axis. The X-andY-axis must be built on top of the f-axis. Therefore, the
acceptable axis sequence from the base goniometer to the sample can either be
v ! c ! f ! (X, Y, Z)orv ! c ! Z ! f ! (X, Y). The axes in parenthesis
have the same sequence order and can be stacked in any relative order mechanically.
Any axis in the sequence can be absent. For example, in the XYZ stage shown in
Figure 5.2(c), the XYZ axes are directly mounted on the v circle, and c and f are
absent and considered to be zero. In rare cases, the above sequence is not followed,
which will result in a different behavior of the goniometer. For instance, if the f-axis
is stacked above the X- and/or Y-axis, the X or Y translation will offset the f-axis
from the instrument center. In this case, the f rotation will bring a different part of
the sample into the instrument center. The X-ray irradiated area will be a circular
trace on the sample instead of a spot. This type of mechanism may be used only
when the purpose of f rotation is to oscillate the sample to improve sampling
statistics.
