The side-on design is used, for instance, in the type 931, the first mass-produced pmt.
The density structures in the expanding corona are identified by side-on laser shadowgraphy using a diagnostic probe laser beam with variable time delay with respect to the heating laser pulse.
The first one was looking side-on perpendicularly to the laser beam axis, the other was placed behind the target giving an image of its rear side.
The smoothing effect was monitored by a pair of pinhole cameras: one viewing side-on and the other one placed at the rear side of the target.
To investigate the growth rate of this instability, the channels were recorded side-on with a framing camera.
Occasionally, adjacent cones were found tilted at angles intermediate between side-on and end-on orientations.
These measurements were obtained from inner and outer segments of photoreceptors in side-on orientation.
The laser beam was split to provide simultaneous end-on and side-on measurements.
