Optical Diagnostics and Imaging - Applied Optics Fundamentals and Device Applications - page 317

The scintillators had various sizes up to about 6 in., so they were masked to
have a common 6 mm diameter circular area from which light could be col-
lected. Each was placed in a dark chamber with a fast photomultiplier tube
module (Hamamatsu H9656MOD), containing a transimpedance amplifier.
X-rays from the pulsers were directed at the scintillators from about 8 in.
outside of the dark box, at a flux density of the order of 10 9 cm −2 and duration
of approximately 30 ns/pulse. The photomultiplier was located about four-
teen inches from the scintillator, and was followed by a Tektronix TDS 2024B
200 MHz 2 Gs/s oscilloscope. Photographs of the resulting traces were used
to report the integrated output and speed of the scintillators.
It is interesting to note that the efficiency at 150 keV is not very different
from that at 450 keV, despite the 7.4× higher attenuation reported in the litera-
ture for 150 keV with respect to 511 keV [17]. Future work around the visible
photon yield per x-ray, as a function of x-ray energy and scintillator flavor,
may help clarify the issue. It is also notable that the measured decay times
are far longer than those reported [18]. For frames of about 1 μs duration,
placed at various spacing throughout an event of tens to thousands of micro-
seconds, the scintillator response times are inadequate.
6.13.5 System Configurations
Using currently available technology, the apparatus typically required in
order to implement a flash cinematography system will likely include
• High-voltage power supply
• Trigger, timing, and delay control electronics
• Trigger amplifier
• X-ray pulser(s) + [1] multi-anode x-ray tube
• Target positioning and backing fixture
• High decay rate scintillating screen (<10 μs decay)
• Mirror
• Image intensifier
• High frame rate camera
• Computer control system and software
• Connecting cables
This equipment can be configured in order to provide an efficient and safe
means of capturing x-ray image sequences synchronized to high-velocity
test events. The use of a multi-anode tube for x-ray exposure of fixed posi-
tion targets will reduce the complexity of some test arrangements. Complete
characterization of any parallax effects from multiple anode spacing can
be used to enhance spatial resolution of images used for metrology. The