124
H. J. Hilke and W. Riegler
and a resolution of 60 μm is obtained [15, p. 178]; in CMS, 75 μm resolution
is achieved with each strip read out at a minimum pitch of 8.4 mm [16, p. 197].
In LHCb, spatial resolution is secondary to fast timing and high efficiency for a
five-fold coincidence trigger. Adjustment to the requirements on spatial resolution,
which change strongly with radius, is achieved by forming readout pads of variable
size (0.5 × 2.5 − 16 × 20 cm 2 ) on the cathodes and by grouping sense wires [17,
p. 130].
4.3.3 Drift Chambers
Already in the very first publications, the basic two types of drift chambers were
described: (i) with the drift volume, through which the particles pass, separated
from the amplification volume [9] and (ii) a geometry, in which the particles pass
directly through the volume containing the anode wires alternating with field wires
to improve the drift field [10], see Fig. 4.20.
The first design finally evolved into the TPC, the second into a large number of
different designs. One can differentiate between planar and cylindrical geometries.
4.3.3.1 Planar Geometries
Most planar geometries are rather similar to each other. To obtain a more homogeneous drift field, additional field shaping electrodes are introduced, see Fig. 4.21.
Also shown is a recent example, one element of a layer for the Barrel Muon system
of CMS. The space resolution per layer is about 250 μm. One muon station consists
of 2 × 4 layers of such tubes fixed to an aluminum honeycomb plate. The other
coordinate is provided by a third set of 4 layers oriented at 90
◦ .
The central detector of UAl used a special arrangement, see Fig. 4.22. In a
horizontal magnetic field, at right angle to the beam, a cylinder 6 m long and 2.2 m in
diameter is filled with planar subelements. In the central part, vertical anode planes
Fig. 4.20 First two drift chamber designs. Left: separate drift and amplification gaps [9]. Right:
Common drift and amplification volume. The additional field wires improve the drift field [10]
H. J. Hilke and W. Riegler
and a resolution of 60 μm is obtained [15, p. 178]; in CMS, 75 μm resolution
is achieved with each strip read out at a minimum pitch of 8.4 mm [16, p. 197].
In LHCb, spatial resolution is secondary to fast timing and high efficiency for a
five-fold coincidence trigger. Adjustment to the requirements on spatial resolution,
which change strongly with radius, is achieved by forming readout pads of variable
size (0.5 × 2.5 − 16 × 20 cm 2 ) on the cathodes and by grouping sense wires [17,
p. 130].
4.3.3 Drift Chambers
Already in the very first publications, the basic two types of drift chambers were
described: (i) with the drift volume, through which the particles pass, separated
from the amplification volume [9] and (ii) a geometry, in which the particles pass
directly through the volume containing the anode wires alternating with field wires
to improve the drift field [10], see Fig. 4.20.
The first design finally evolved into the TPC, the second into a large number of
different designs. One can differentiate between planar and cylindrical geometries.
4.3.3.1 Planar Geometries
Most planar geometries are rather similar to each other. To obtain a more homogeneous drift field, additional field shaping electrodes are introduced, see Fig. 4.21.
Also shown is a recent example, one element of a layer for the Barrel Muon system
of CMS. The space resolution per layer is about 250 μm. One muon station consists
of 2 × 4 layers of such tubes fixed to an aluminum honeycomb plate. The other
coordinate is provided by a third set of 4 layers oriented at 90
◦ .
The central detector of UAl used a special arrangement, see Fig. 4.22. In a
horizontal magnetic field, at right angle to the beam, a cylinder 6 m long and 2.2 m in
diameter is filled with planar subelements. In the central part, vertical anode planes
Fig. 4.20 First two drift chamber designs. Left: separate drift and amplification gaps [9]. Right:
Common drift and amplification volume. The additional field wires improve the drift field [10]