6 Calorimetry
249
of krypton. In order to smooth the sampling of the shower, the bands were given a
zigzag shape in depth by passing the ribbons through staggered glass-epoxy frames.
The preamplifiers, connected to each signal band through a blocking capacitor, were
located in the liquid for best performances. This calorimeter operated at a high
voltage of 3 kV (0.3 kV/mm electric field), in a stable way during several years,
with performances characterized by a stochastic term of 3.5%/
√
E, a signal peaking
time of 80 ns, a noise per cell of 9 MeV (about 100 cells are needed to reconstruct
with high accuracy an electromagnetic shower), a linearity better than 1 part in a
thousand between 10 and 90 GeV, and an uniformity of response of 0.5%. Liquid
krypton is also being used for the calorimeter (KEDR) of the VEPP2M collider at
Novosibirsk [91].
Homogeneous noble liquid calorimeters with very high granularity readout can
lead to very interesting imaging and energy measurement properties. One concept,
inspired by gaseous tracking chambers (TPCs), was pioneered by the ICARUS
collaboration [92, 93]. A more recent example is microBoone at Fermilab [94].
Detectors of this type with long drift distances (1 m or above) find their application
in low rate experiments, such as neutrino experiments. The DUNE project, already
mentioned, combines the readout of scintillation light and ionization.
A potentially attractive alternative to noble liquids is the use of silicon detectors.
However, due to the high cost of silicon diode sensors, the silicon calorimeters
operated so far have been restricted to places where the lack of space, and the limited
volume, made the use of this technology mandatory. An example is given by SiCal
[95], the luminosity calorimeter of the Aleph experiment at LEP. It consisted of
a stack of 12 layers of silicon sensors interleaved with tungsten absorber plates,
for a total thickness of ~24 X 0 in a longitudinal extension of only 150 mm. High
resistivity, n-type (7 kcm, 300 μm thickness) Si was used for the 1.3 m 2 readout
area, divided into 12,228 channels. The primary purpose of the detector was an
absolute measurement of the luminosity using Bhabha scattering. The precision
in the reconstructed position of showers (see Sect. 6.4.1) and the precision of the
detector acceptance and alignment were essential for the measurement.
For the High-Luminosity LHC phase (HL-LHC) the CMS collaboration is
embarking on an extremely ambitious replacement of the electromagnetic part of
its end-cap calorimeters. Sampling calorimeters with Si-diode readout are being
developed. The total Si readout area will be 600 m2 with a total of 6 million readout
and 1 million trigger channels. Remarkably, intensive R&D has demonstrated that
the Si detectors will withstand the radiation load [96]. This approach will be
taken one step further for detector facilities at future colliders, such as a e + e −
Linear Collider, with Centre of Mass energy up to several hundreds of GeV.
Electromagnetic and hadronic calorimeters with extreme granularity and up to 100
million channels are being considered [97]. For such devices the use of Silicon
sensors is one technology of choice. The cost of this option may be an obstacle,
to be weighted against the potential performance advantages (see Sect. 6.5). In
the forward direction, where the level of electromagnetic radiation from the beams
is expected to be high, more radiation resistant sensors, like diamond, are being
considered [98].
249
of krypton. In order to smooth the sampling of the shower, the bands were given a
zigzag shape in depth by passing the ribbons through staggered glass-epoxy frames.
The preamplifiers, connected to each signal band through a blocking capacitor, were
located in the liquid for best performances. This calorimeter operated at a high
voltage of 3 kV (0.3 kV/mm electric field), in a stable way during several years,
with performances characterized by a stochastic term of 3.5%/
√
E, a signal peaking
time of 80 ns, a noise per cell of 9 MeV (about 100 cells are needed to reconstruct
with high accuracy an electromagnetic shower), a linearity better than 1 part in a
thousand between 10 and 90 GeV, and an uniformity of response of 0.5%. Liquid
krypton is also being used for the calorimeter (KEDR) of the VEPP2M collider at
Novosibirsk [91].
Homogeneous noble liquid calorimeters with very high granularity readout can
lead to very interesting imaging and energy measurement properties. One concept,
inspired by gaseous tracking chambers (TPCs), was pioneered by the ICARUS
collaboration [92, 93]. A more recent example is microBoone at Fermilab [94].
Detectors of this type with long drift distances (1 m or above) find their application
in low rate experiments, such as neutrino experiments. The DUNE project, already
mentioned, combines the readout of scintillation light and ionization.
A potentially attractive alternative to noble liquids is the use of silicon detectors.
However, due to the high cost of silicon diode sensors, the silicon calorimeters
operated so far have been restricted to places where the lack of space, and the limited
volume, made the use of this technology mandatory. An example is given by SiCal
[95], the luminosity calorimeter of the Aleph experiment at LEP. It consisted of
a stack of 12 layers of silicon sensors interleaved with tungsten absorber plates,
for a total thickness of ~24 X 0 in a longitudinal extension of only 150 mm. High
resistivity, n-type (7 kcm, 300 μm thickness) Si was used for the 1.3 m 2 readout
area, divided into 12,228 channels. The primary purpose of the detector was an
absolute measurement of the luminosity using Bhabha scattering. The precision
in the reconstructed position of showers (see Sect. 6.4.1) and the precision of the
detector acceptance and alignment were essential for the measurement.
For the High-Luminosity LHC phase (HL-LHC) the CMS collaboration is
embarking on an extremely ambitious replacement of the electromagnetic part of
its end-cap calorimeters. Sampling calorimeters with Si-diode readout are being
developed. The total Si readout area will be 600 m2 with a total of 6 million readout
and 1 million trigger channels. Remarkably, intensive R&D has demonstrated that
the Si detectors will withstand the radiation load [96]. This approach will be
taken one step further for detector facilities at future colliders, such as a e + e −
Linear Collider, with Centre of Mass energy up to several hundreds of GeV.
Electromagnetic and hadronic calorimeters with extreme granularity and up to 100
million channels are being considered [97]. For such devices the use of Silicon
sensors is one technology of choice. The cost of this option may be an obstacle,
to be weighted against the potential performance advantages (see Sect. 6.5). In
the forward direction, where the level of electromagnetic radiation from the beams
is expected to be high, more radiation resistant sensors, like diamond, are being
considered [98].