6 Calorimetry
263
6.7 Examples of Calorimeters and Calorimeter Facilities
The development of calorimetric facilities was and continues to be driven by the
main directions of particle physics. Not surprisingly, as particle physics had its
origin in cosmic ray studies, rather crude hadronic sampling calorimeters were
successfully used to measure the energy spectrum of cosmic rays [52]. Electron
scattering experiments provided the impetus for the development of homogeneous
[129] and sampling [130] electromagnetic calorimeters. A major step in understanding and perfecting hadronic sampling calorimeters was made for the study of hadron
scattering experiments, both with protons and neutrons [131]. The basic properties
of these instruments were derived and Monte Carlo studies helped to optimize them
[132]. The ISR provided the next motivation for a major development effort [35],
providing the basis for the calorimeter facilities at Fermilab, HERA and LHC. In
parallel, equally innovative calorimeter developments were and are initiated for
astro-particle physics.
The recent series of CP-violation experiments in neutral kaon decay has pushed
the requirements for electromagnetic calorimetry (Sect. 6.3.3). The LEP physics
program emphasized charged particle spectroscopy and identification, with one
notable exception, the L3 electromagnetic BGO crystal calorimeter (Sect. 6.3.1)
and U/gas hadron calorimeter. For the Fermilab Collider program general purpose
electromagnetic and hadronic calorimeter facilities were developed; facilities with
new levels of performance were required for HERA, motivated by the need for
precision jet spectroscopy (Sect. 6.7.5).
The LHC physics needs state-of-the-art electromagnetic and hadronic calorimetry, optimized for photons at the 100 GeV scale and for jets at the TeV scale,
posing challenging system questions, answered in novel and unconventional ways
(Sects. 6.7.3 and 6.7.6.1). The Future Collider physics programmes require further
performance improvements, particularly concerning jet spectroscopy, exploiting at
the same time the specific operation environment (Sects. 6.7.6.2).
6.7.1 The MEG Noble Liquid Homogeneous Calorimeter
with Light Readout
The MEG experiment at PSI [73] is dedicated to the search for lepton flavour
violation in muon decays. It aimed at a sensitivity for μ → eγ decays of 10 −13 .
This requires an outstanding background rejection (for example of the reaction
μ → eννγ), requiring a calorimeter with an excellent energy resolution for ~50 MeV
photons and a sub-ns response to cope with the high rate.
The half-cylinder shaped calorimeter is shown in Fig. 6.42. It contains 800 litres
of liquid Xenon, and is read out by 846 PMTs, covering approximately 30% of the
outside surface of the detector volume.
263
6.7 Examples of Calorimeters and Calorimeter Facilities
The development of calorimetric facilities was and continues to be driven by the
main directions of particle physics. Not surprisingly, as particle physics had its
origin in cosmic ray studies, rather crude hadronic sampling calorimeters were
successfully used to measure the energy spectrum of cosmic rays [52]. Electron
scattering experiments provided the impetus for the development of homogeneous
[129] and sampling [130] electromagnetic calorimeters. A major step in understanding and perfecting hadronic sampling calorimeters was made for the study of hadron
scattering experiments, both with protons and neutrons [131]. The basic properties
of these instruments were derived and Monte Carlo studies helped to optimize them
[132]. The ISR provided the next motivation for a major development effort [35],
providing the basis for the calorimeter facilities at Fermilab, HERA and LHC. In
parallel, equally innovative calorimeter developments were and are initiated for
astro-particle physics.
The recent series of CP-violation experiments in neutral kaon decay has pushed
the requirements for electromagnetic calorimetry (Sect. 6.3.3). The LEP physics
program emphasized charged particle spectroscopy and identification, with one
notable exception, the L3 electromagnetic BGO crystal calorimeter (Sect. 6.3.1)
and U/gas hadron calorimeter. For the Fermilab Collider program general purpose
electromagnetic and hadronic calorimeter facilities were developed; facilities with
new levels of performance were required for HERA, motivated by the need for
precision jet spectroscopy (Sect. 6.7.5).
The LHC physics needs state-of-the-art electromagnetic and hadronic calorimetry, optimized for photons at the 100 GeV scale and for jets at the TeV scale,
posing challenging system questions, answered in novel and unconventional ways
(Sects. 6.7.3 and 6.7.6.1). The Future Collider physics programmes require further
performance improvements, particularly concerning jet spectroscopy, exploiting at
the same time the specific operation environment (Sects. 6.7.6.2).
6.7.1 The MEG Noble Liquid Homogeneous Calorimeter
with Light Readout
The MEG experiment at PSI [73] is dedicated to the search for lepton flavour
violation in muon decays. It aimed at a sensitivity for μ → eγ decays of 10 −13 .
This requires an outstanding background rejection (for example of the reaction
μ → eννγ), requiring a calorimeter with an excellent energy resolution for ~50 MeV
photons and a sub-ns response to cope with the high rate.
The half-cylinder shaped calorimeter is shown in Fig. 6.42. It contains 800 litres
of liquid Xenon, and is read out by 846 PMTs, covering approximately 30% of the
outside surface of the detector volume.