92
H. J. Hilke and W. Riegler
permitting low load resistances and thus high counting rates. Cosmic ray physics
in particular profited from systems of such counters used with electron tube
coincidence circuits. It took a number of years to understand the basic processes
in different gases and under various operation conditions.
Proportional counters regained interest, when the development of more sensitive
readout electronics permitted energy determination. In the second half of the 1940s,
however, the demand for faster counters with longer lifetime and higher sensitivity
initiated a move towards scintillation techniques, which saw a rapid development,
especially after the introduction of the photomultiplier, soon providing fast response
and time resolutions below 10 −8 s. On the gas detector side, only the novel technique
of parallel plate counters [6] could compete, with time resolutions down to 10 −10 s,
however with lower rate capability. A detailed account of the developments up to
the 1950s can be found in [7].
The field of gas detectors was revived with the introduction of the multiwire
proportional chamber by Charpak in 1968 [8] and shortly afterwards with the
extension by two groups to drift chambers with different geometries [9, 10]. The
following decades saw a rapid development of the techniques, especially in high
energy physics but also for nuclear physics and other fields. An additional major
R&D effort was triggered in the 1990s by the requirements for the LHC: extreme
particle rates and radiation hardness. Solutions demanded very careful choice of gas
fillings as well as of construction materials and methods. Gas detectors were and are
still used mainly for tracking but also in calorimeters, Cherenkov counters and the
detection of transition radiation. Only in the layers closest to the interaction points
in accelerator experiments and in other applications where spatial resolution is the
prime requirement, finely grained silicon detectors have taken over as first choice.
Most of the detector developments were made possible only by the extremely
rapid progress in the field of electronics, with respect to miniaturization, integration
density, cost and radiation hardness.
Powerful simulation programs have been developed in the past decades and
have been widely used in the development and optimization of gas detectors. The
program Garfield [11] calculates electric fields, electron and ion trajectories and
induced signals. The program Heed [12] describes primary ionization produced by
fast particles in gases and the program Magboltz [13] electron transport properties
in gas mixtures. The agreement of simulation and measurement has become
impressive.
We shall at several occasions refer to designs and studies from the LHC experiments. Recent detailed reports them may be found in [14–17]. The development of
the last years can well be followed in the Proceedings of the Vienna Conference on
Instrumentation initiated in 1977 as Wire Chamber Conference on a tri-annual basis
[18] and of the annual IEEE Nuclear Science Symposia.
The following sections will start with a description of the basic processes in
gaseous detectors: ionization of the gas by charged particles (Sect. 4.2.1), transport
of electrons and ions in electric and magnetic fields (Sect. 4.2.2), avalanche
amplification in high electric fields (Sect. 4.2.3), formation of the readout signals
(Sect. 4.2.4) and ‘ageing’ of detectors under irradiation (Sect. 4.2.6). A discussion
H. J. Hilke and W. Riegler
permitting low load resistances and thus high counting rates. Cosmic ray physics
in particular profited from systems of such counters used with electron tube
coincidence circuits. It took a number of years to understand the basic processes
in different gases and under various operation conditions.
Proportional counters regained interest, when the development of more sensitive
readout electronics permitted energy determination. In the second half of the 1940s,
however, the demand for faster counters with longer lifetime and higher sensitivity
initiated a move towards scintillation techniques, which saw a rapid development,
especially after the introduction of the photomultiplier, soon providing fast response
and time resolutions below 10 −8 s. On the gas detector side, only the novel technique
of parallel plate counters [6] could compete, with time resolutions down to 10 −10 s,
however with lower rate capability. A detailed account of the developments up to
the 1950s can be found in [7].
The field of gas detectors was revived with the introduction of the multiwire
proportional chamber by Charpak in 1968 [8] and shortly afterwards with the
extension by two groups to drift chambers with different geometries [9, 10]. The
following decades saw a rapid development of the techniques, especially in high
energy physics but also for nuclear physics and other fields. An additional major
R&D effort was triggered in the 1990s by the requirements for the LHC: extreme
particle rates and radiation hardness. Solutions demanded very careful choice of gas
fillings as well as of construction materials and methods. Gas detectors were and are
still used mainly for tracking but also in calorimeters, Cherenkov counters and the
detection of transition radiation. Only in the layers closest to the interaction points
in accelerator experiments and in other applications where spatial resolution is the
prime requirement, finely grained silicon detectors have taken over as first choice.
Most of the detector developments were made possible only by the extremely
rapid progress in the field of electronics, with respect to miniaturization, integration
density, cost and radiation hardness.
Powerful simulation programs have been developed in the past decades and
have been widely used in the development and optimization of gas detectors. The
program Garfield [11] calculates electric fields, electron and ion trajectories and
induced signals. The program Heed [12] describes primary ionization produced by
fast particles in gases and the program Magboltz [13] electron transport properties
in gas mixtures. The agreement of simulation and measurement has become
impressive.
We shall at several occasions refer to designs and studies from the LHC experiments. Recent detailed reports them may be found in [14–17]. The development of
the last years can well be followed in the Proceedings of the Vienna Conference on
Instrumentation initiated in 1977 as Wire Chamber Conference on a tri-annual basis
[18] and of the annual IEEE Nuclear Science Symposia.
The following sections will start with a description of the basic processes in
gaseous detectors: ionization of the gas by charged particles (Sect. 4.2.1), transport
of electrons and ions in electric and magnetic fields (Sect. 4.2.2), avalanche
amplification in high electric fields (Sect. 4.2.3), formation of the readout signals
(Sect. 4.2.4) and ‘ageing’ of detectors under irradiation (Sect. 4.2.6). A discussion