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New Developments in Photodetection for Particle Physics
and Nuclear Physics
J. E. Elias
Fermi National Accelerator Laboratory*
P.O. Box 500, Batavia, IL 60510, USAAbstract
Photodetectors are widely used in particle and nuclear
physics research. Since the beginning of the modern era of
photoelectric transducers in the late 1930's, many types of
devices have been developed and exploited for physics
research. New performance requirements arising in physics
experiments have often provided very interesting
technological drivers for industry. New ideas for photo-
detection are rapidly adapted by the physics community to
enable more powerful experimental capabilities. This report
gives a sampling of new developments in photodetection for
physics research in the period since the first conference in
this series, Beaune 96. Representative examples of
advances in vacuum devices, solid-state devices and gaseous
photodetectors are described including, where appropriate,
an indication of areas where technological improvements are
needed or expected.
1. INTRODUCTION
Research in particle and nuclear physics relies heavily on
photodetection methodologies for tracking, energy and
particle identification detectors. Charged particles are
detected either through the ionization produced by the
particle's passage or through emission of photons produced
by scintillation, fluorescence, Cherenkov or annihilation
processes. Although the physics community does little basic
research in photodetection, being very much application
driven, any new developments in photodetection are rapidly
evaluated and developed for physics experiments purposes.
The pace of innovation in the past ten to fifteen years has far
outstripped that of previous decades, particularly in solid-
state photodetectors. A large part of the dynamic has been
requirements from new experiments in which rather extreme
conditions are present: magnetic fields up to 40 kGauss,
radiation exposures up to 10 MRad, a linear dynamic range
of 18 bits, single photon counting with more than 50%
efficiency, and high stability over years of operation.
The first conference on new developments in
photodetection, Beaune 96 [1], was created in recognition of
this sudden flowering. This second conference three years
later (dedicated to the memory of P. Besson who founded
the series) marks the continuance if not acceleration of thepace of development in photodetectors for physics research.
In this report, photodetection developments are grouped into
three classifications, vacuum devices, gaseous photo-
detectors and solid-state devices. Representative examples
from each have been selected that are illustrative of the
progress and accomplishments since Beaune 96, and no
claim of inclusiveness is made.
2. VACUUM DEVICES
A. Photomultiplier Tubes
In a global sense, one could say that progress since the
invention of the photomultiplier tube at the RCA labs in
1936 has been incremental. However, further innovations
such as fiberoptic faceplates, mesh and metal-channel
dynodes, graded seals, microchannel plates, and electron
bombardment anodes have all led to totally new capabilities
and applications. Many of these new types of
photomultipliers have come in response to the needs of
physics research experiments. The physics market may be a
risky one-shot business for industry, but the technology
drivers from physics applications can lead to new types of
photomultiplier tubes and open new market areas.
Today's global economy has resulted in a situation where
developments are controlled by market considerations. The
largest single market is for gamma cameras with 180,000
units sold annually [2]. Competitiveness here hinges on four
performance areas; pulse height resolution, stability,
reliability, and physical footprint. Physics applications
which can benefit from these characteristics, particularly
pulse height resolution, are then leveraging into a very large
R&D effort. For example, studies at Jefferson Lab for the
modest UV response of a silica aerogel Cherenkov radiator
[3] have shown that the superior photoelectron collection
efficiency of relatively inexpensive gamma camera tubes can
provide performance figures as good as those of very
expensive tubes with quartz windows and a high gain
gallium-phosphide first dynode.
The photomultiplier tube developed for the time-of-flight
detector in the CDF experiment illustrates the situation
where a new device is realized as a variation of an existing
standard device. In this detector, scintillators are located in
a high magnetic field and light pipes to a field-free region
are ruled out since timing resolution varies as the square root*Work supported by U. S. Department of Energy under contract no. DE-AC02-76CH0300.
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Elias, John E. New developments in photdectection in particle physics and nuclear physics, article, October 8, 1999; Batavia, Illinois. (https://digital.library.unt.edu/ark:/67531/metadc628487/m1/3/: accessed April 17, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.