A simple imaging system to facilitate crystal orientation with respect to the x−ray beam for Berg−Barrett topography has been constructed. This system consists of an image intensifier tube with an x−ray phosphor deposited on its fiber−optic input plate and means to manipulate and indicate the crystal orientation. Applications of the system to studies of both crystalline and biological samples are given

Lau, S. S.

Vreeland, T., Jr.

English

Caltech Authors - Main

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A simple image intensifying system for Berg-Barrett 
topography 
T. Vreeland,Jr. and S. S. Lau 
W. M. Keck Laboratory of Engineering Materials, California Institute of Technology, Pasadena, California 91109 
(Received 15 April 1974; and in final form, 2 May 1974) 
A simple imaging system to facilitate crystal orientation with respect to the x-ray 
beam for Berg-Barrett topography has been constructed. This system consists of 
an image intensifier tube with an x-ray phosphor deposited on its fiber-optic input 
plate and means to manipulate and indicate the crystal orientation. Applications 
of the system to studies of both crystalline and biological samples are given. 
INTRODUCTION 
X-ray topographic methods have been employed in a 
variety of studies of crystalline materials (see review by 
Armstrong and Wu1). In both transmission and reflection 
topography, the specimen is oriented for Bragg diffraction 
from a known set of crystallographic planes. Bragg reflec-
tions are usually detected by a radiation counter, or by 
direct viewing of the reflection on a fluorescent screen. 
A few investigators have employed viewing of the inten-
sified image formed on a fluorescent screen (Lang and 
Reifsnider, 2 Green3) and others have used x-ray video 
systems (Green3). 
Direct viewing of the image on a fluorescent screen 
without electronic intensification is difficult because of the 
low x-ray intensity. Optimum adjustment of the crystal 
orientation can only be approximated in this manner and 
must be checked by the use of film. The image inten-
sification system described in this paper for reflection 
topography provides sufficient luminous gain that com-
plete darkness and dark adapted vision are not required 
as they were for the system used previously (Turner, 
Vreeland, and Pope)4 • An improved construction of the 
Berg-Barrett camera has been reported by Liang and 
Pope. 5 Their camera is totally enclosed to decrease radia-
tion exposure to the experimenter, but this enclosure 
restricts the placement and observation of the fluorescent 
screen. The Berg-Barrett camera described here permits 
the fluorescent screen to be placed close to the specimen 
(to increase resolution) and provides ample radiation 
shielding for the experimenter. 
THE IMAGE TUBE 
An RCA type 4549 tube with a 40 mm diam input face 
is used. This is a three-stage electrostatic focus image 
intensifier with a luminous gain of about 75 OOOX and a 
maximum center resolution of 40 lp/mm. The tube operates 
from a 6. 7 5 V de power source and generates 45 k V inter-
nally. The tube is supplied with a current limiting circuit, 
and for use with the input end grounded. It would be 
desirable to have the viewing end of the tube grounded, 
but this would require the input end to be at -45 kV and 
prevent its placement close to the (grounded) specimen 
for optimum resolution. 
41 Rev. Sci. lnstrum., Vol. 46, No. 1, January 1975 
An x-ray phosphor can be deposited directly onto the 
input plate of the image tube or onto a well-polished 
fiber-optic plate which is coupled to the input plate of 
the tube with silicon grease or optical cement. Deposition 
is achieved by either a settling process (Stonc6) or an 
electrophoretic process (McGee, Airey, and Aslam7). 
A settled coating was found to be somewhat easier to 
apply. We are currently using a General Electric 118-2-19 
phosphor (ZnCdS, P-20, with a particle size of 3-4 Jl.). 
The fine particles of phosphor were separated by flotation 
and a coating of a few microns in thickness ( ~ 1 mg/ cm2) 
was deposited by the settling process. This coating is 
sufficiently thin so that it does not degrade the resolution 
of the system. While the phosphor coating thickness may 
be optimized (to maximize luminous output) for a given 
x-ray wave length, the 1 mg/cm2 is a good compromise 
for the commonly used radiations (Cr K..,, Co K..,). 40 J1. 
gold dots flashed onto a zinc specimen with basal surface 
orientation can be resolved from an x-ray topographic 
image taken from the output plate of the present system. 
The x-ray phosphor on the input end of the image tube 
is covered by a thin opaque plastic film which prevents 
room light from exciting the phosphor. Metal foil x-ray 
filters arc taped over the plastic f1lm when they are needed 
to attenuate either x-ray fluorescence from the crystal or 
unwanted Bragg reflections due to characteristic K~ 
radiation. 
The tube is clamped in a horizontal position so that it 
projects through a metal plate which serves as a radiation 
FrG. 1. Photograph of the camera with the drives in place. a-360° 
protractor for roll angle; b-specimen; c-optoelectronic system 
d-dc g~armot_or; e-180° protractor for Bragg angle; £-friction drive 
g-vertlcal adjustment; h-manual micrometer drive· i-x-ray track 
and j-circular table. ' 
Copyright © 1975 by the American Institute of Phvsics 41 
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42 T. Vreeland, Jr. and S. S. Lau: Image intensifying system 42 
Fw. 2. Imal-(ing system with the image tube in place. A-x-ray 
beam stop with fluorescent screen; B~--~image tuhe assembly; C--
viewing end of the image tube; n--vertical adjustment for the image 
tube; E--~-llcxiblc cable for micrometer drive; and ]<'-~-x-ray slit col-
limator tube. 
shield. This shield, and the tube itself protect the experi-
menter from radiation emanating from the x-ray tube and 
the specimen. Adjustments arc provided for both the 
height of the image tube and its projection through 
the plate. 
CRYSTAL MANIPULATIONS 
The camera parts described in Turner et al.4 were used. 
These parts provide for translation perpendicular to the 
x-ray track (manual micrometer drive), vertical adjust-
ment of the crystal (perpendicular to the x-ray track), 
Bragg angle adjustment (rotation of a 10 em circular table 
about a vertical axis), and roll angle about the normal 
to the crystal face. 
A flexible coupling attached to the micrometer drive 
and passing through the metal plate of the image tube 
mount permits translation adjustments to be made. A 15 em, 
180° protractor w~1s attached to the circular table. Direct 
current gearmotors provide a friction drive for the pro-
tractors on the circular table and on the roll angle ad-
justment. An optoelectronic system is incorporated in each 
motor mount assembly to generate signals which indicate 
angular position. When rotation occurs, the protractor 
divisions (black lines on a clear plastic) are counted by 
this system. Bragg angle and roll angle adjustments are 
made, with control on speed and direction, and displayed 
2110 Tf20 
Tom 
(a) (b) 
FIG. 3. (a) Symmetry pattern of a zinc crystal with basal surface 
orientation showing three reflecting conditions simultaneously. (b) The 
geometry used to obtain the topograph of Fig. 3(a) is shown as a 
triangle in the shaded area of the reflection locus plot. Zinc (0001) 
surface, Co Ka radiation. Due to the finite size of both x-ray source 
<md crystal surface area, three reflections are obtained although the 
three reflecting loci do not intersect at a common point. Fluorescence 
from the specimen causes the bright haze in the center of the picture. 
Rev. Sci. lnstrum., Vol. 46, No. 1, January 1975 
IOi 
211 
iol 
T2T 
(a) (b) 
FIG. 4. (a) Symmetry pattern of a silicon crystal with (111) orienta-
tion satisfying three reflecting conditions simultaneously. (h) The 
geometry used to obtain the topograph of Fig. 4(a) is shown as a 
tri<mglc in the shaded area of the reilcciion locus plot. Silicon (111) 
surface, Co Ka radiation. 
on ft h<md-held control box (Bragg angle display reads 
0.0°-·99.5° in 0.5° increments and roll angle display re<tds 
0°--360° in 1 o increments). A photograph of the camera 
with the drives in place is shown in Fig. 1. Figure 2 shows 
the system with the image tube in place. 
APPLICATIONS 
A. Determination of Crystal Orientation with 
Respect to the X-ray Beam 
In order to align the crystal for a specif1c Bragg reflec-
tion, it is necessary to establish the crystal orientation 
with respect to the incident beam. For example, if the zero 
layer (10l3) reflection from a zinc specimen with basal 
surface orientation is desired, it is best to select an in-
cident beam direction to satisfy the (2023), (01 12) and 
(10i2) reflecting conditions simultaneously as indicated by 
the shaded area on the locus plot in Fig. 3(b). Once the 
symmetry pattern is identified on the image tube [shown 
on Fig. 3(a)] the zero layer of the (10i3) reflection or 
any other possible reflections can be obtained by adjusting 
the crystal (Bragg angle and roll angle adjustment) to the 
required orientation according to the reflection locus plot. 
All crystallographic directions on the specimen surface can 
also be determined by first establishing the location of the 
symmetry pattern. Another example is shown in Fig. 4(a) 
and (b) where the incident beam satisfies the (404), (400), 
and (004) reflections simultaneously for a (111)-oriented 
FIG. 5. Topograph of a ;>,inc crystal wit~ (0001) . surface showing 
substructure and damage. Zero layer of (1013) reflectiOn. 
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43 T. Vreeland, Jr. and S. S. Lau: Image intensifying system 43 
(a) (b) 
FIG. 6. (a) Image of a rat brain section recorded by a commercial unit (Faxatron, manufactured by the Field Emission Co.). 1.5 em in width, 
1 mm thick. (b) Stereo pair of images of a similar rat brain section recorded with the present system. 
silicon crystal. It should be noted that the (0112) and 
(1012) reflections for zinc and the ( 400) and (004) reflec-
tions for silicon are weak and narrow, and are difficult to 
observe without image intensification. 
B. Survey of Possible Bragg Reflection 
for Topography 
An optimal Bragg reflection should have a strong re-
flecting intensity and a large reflecting area. The present 
system allows a quick survey of all possible Bragg reflec-
tions and the determination of the optimal reflection for 
topography. 
C. Survey of Crystal Quality 
Substructure, scratch and handling damage in the 
specimen are easily identified by observation of the inten-
sified image. Figure 5 shows an example of an image ob-
tained from a poor quality zinc crystal. Both damaged 
areas and subgrains are clearly revealed. The dimensions 
of the subgrains and damaged areas can also be estimated. 
D. Determination of Diffracting Area 
It is often necessary to determine which portion of the 
crystal is diffracting, as in the case where different reflec-
tions from the same area are to be obtained. This simple 
imaging system is very useful for adjusting the specimen 
so that the area of interest is strongly diffracting. 
E. Biological Applications 
Biological samples have been examined using this imaging 
system. Sections of rat brain with a barium compound 
injected into the blood vessels were examined with Cu Ka 
Rev. Sci. lnstrum., Vol. 46, No. 1, January 1975 
radiation. The samples are typically 1 mm thick. The 
sample was placed in the direct x-ray beam and the imaging 
system was placed behind and in contact with the rat 
brain section. Transmission images of the sample ob-
servable on the output end of the image tube were recorded 
on photographic films. Figure 6(a) shows a rat brain sec-
tion recorded by a commercial unit (Faxatron manufac-
tured by the Field Emission Company, W-radiation, 25 kV, 
3 rnA, ~8 min exposure time). Figure 6(b) shows a similar 
rat brain section recorded in a stereo pair with the present 
system (copper radiation, 8 kV, 1 rnA, 15 sec exposure 
time). We have found that the present system produced 
a rat brain image with better resolved vessels with much 
shorter exposure time. When W radiation is used with the 
present system quantum noise is significantly reduced with 
an operating voltage of 15 kV and above and the required 
exposure time is reduced to a fraction of a second. 
ACKNOWLEDGMENT 
We would like to thank Dr. Douglas C. Mohr for his 
helpful assistance in the preparation of phosphor screens. 
1R. W. Armstrong and C. Cm. Wu, Microstructural Analysis: Tools 
and Techniques, edited by J. L. McCall and W. M. Mueller, 
(Plenum, N.Y., 1973). Also see "X-ray Diffraction Microscopy," 
by R. W. Armstrong and C. Cm. Wu, E.M.G. Report No. CXXI, 
University of Maryland, Center of Materials Research, College 
Park, Maryland. 
2A. R. Lang and K. Reifsnider, Appl. Phys. Let. 15, 258 (1969). 
'R. E. Green, Jr., Advances in X-ray Analysis, edited by C. S. Barrett, 
Vol. 14, p. 311. 
4A. P. L. Turner, T. Vreeland, Jr., and D. P. Pope, Acta Cryst., 
A24, 452 (1968). 
•s. L. Liang and D. P. Pope, Rev. Sci. Instrum. 44, 8, 956 (1973). 
6H. D. Stone, Advances in Electronic Imaging and Electron Physics, 
Vol. 22A, p. 571. 
7J. D. McGee, R. E. Airey, and M. Aslam, Advances in Electronic 
Imaging and Electron Devices, Vol. 22A, p. 571. 


A simple image intensifying system for Berg-Barrett

topography

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A simple image intensifying system for Berg-Barrett topography

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