CDF (Collider Detector at Fermilab) calorimetry Page: 4 of 12
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The calorimeters are all of the sampling type. The
EM calorimeters contain lead as the absorber, whereas
the hadron calorimeters have steel plates. The active
medium is scintillator in the region of large polar
angles, 0, to the beams (central and endwall
calorimeters), and proportional tube chambers with
cathode pad readout at small angles to the beams
(endplug and forward calorimeters). A summary of
calorimeter properties is given in Table 1. Note that
typical calorimeter signals are, by design, quite
similar for all the calorimeter systems.
The angular coverage of the calorimeters is 2 x in
the azimuthal angle 0, and from -4.2 to +4.2 in
pseudorapidity q, which is defined as 7 = -lntan(6/2),
except that the forward hadron calorimeter in the
interval 3.6 < q < 4.2 (and -4.2 < q < -3.6) has
incomplete O-coverage. Expressed in 0, the coverage
is 2* < 9 < 178 .
The calorimeters are all subdivided into many
cells. Each cell is a matching "tower" or solid angle
element of EM and hadron calorimeter. Such a geometry
facilitates the reconstruction of energy patterns in
the detector for physics analysis. The calorimeter
tower segmentation can be represented as rectangles in
the q-O plane. The tower size is given by A q*A # =
0.1*0.09 (approximately) for the pad readout of the
proportional tube chambers, while A q*A 0 = 0.1 * 0.26
(approximately) for the scintillator calorimeters. The
density of particles in typical inelastic collisions
is more or less uniform in q-O space. Fig. 4 shows the
grid of hadron calorimeter towers in one quadrant of
the detector, together with module or chamber
boundaries. In the endplug EM calorimeter, the
chambers cover 900 in 0, but the grid of EM
calorimeter towers is otherwise essentially the same
as that shown in Fig. 4. The boundaries between
calorimeter systems are at 9 = 10 (endplug -
forward), 8 = 30* (endplug hadron calorimeter -
endwall hadron calorimeter) and 6 = 360 (endplug EM
calorimeter - central EM calorimeter). The separation
between calorimeter arches at 0 = 90* is 1 cm.
The interaction region is rather long at the
Tevatron, about 70 cm full width at half maximum,
leading to an effective smearing of the 9 boundaries
in the calorimetry. A less pronounced smearing occurs
in the O-direction for charged particles bent in the
solenoid field. Characteristic sizes of the azimuthal
boundary regions are indicated in Table 1.
The proportional tube chamber calorimeters provide
not only the tower (cathode pad) signals described
above, but also some wire pulse height information.
Individual wires are not read out, but sums of wire
signals, either from a section of a chamber or from a
full chamber, are. The detailed information about
longitudinal shower development coming from these wire
sums can be very useful, both for diagnostic purposes,
and for physics analysis, whenever particles are,
"isolated".
3. Electronics tri eri and readout
Crates of RABBIT (Redundant Analog Based Bus
Information Transfer, see [8}) electronics are located
on the detector on or near the respective
calorimeters. These crates contain charge sensitive
amplifiers [9], sample-and-hold capacitors and
multiplexed 16 bit Analog to Digital Converters.
"Scanners" located in the counting room are used to
read out the ADC information and the channel
addresses. Separate cables carry signals to the COF
trigger system [10].A clock, synchronized to the accelerator radio
frequency system, delivers timing signals to the
electronics. The integration times currently used for
the calorimeter signals are quite long, about 0.5 ps
for the phototube signals and about 1.6 ps for the pad
signals, some of which have large source capacitances
(up to 110 nF). Amplifier gain shifts of up to 15%
are observed for the channels connected to the largest
source capacitances. An on-card calibration system is
used to measure the overall electronics gain, so that
such effects can be corrected for in the data
processing.
The rms electronics noise on an individual channel
is equivalent to about 0.03 CeV of energy deposit in
the tower, whereas full scale is set at about 400 GeV.
The readout of the phototubes on the scintillator
hadron calorimeters includes the digitized value of
the time at which the energy is deposited. This
information is useful for rejection of events in which
cosmic rays deposit large amounts of energy within the
calorimeter signal integration time of a normal pp
event (overlap of cosmic ray and pp event).
Fig. 5 Cutaway view of a proportional tube chamber in
the forward EM calorimeter
4. Proportional tube chamber calorimeters
4.1 Description
The signal in the endplug and forward calorimeters
is generated in sets of proportional tube chambers.
These chambers cover 90* in # (a quadrant), except in
the endplug hadron calorimeter, where structural
supports are spaced at 300 intervals in 0. The
desired tower readout of these calorimeters is
obtained by measuring the induced signals on cathode
pads formed on the printed circuit boards of the
chambers. The signals from corresponding pads at
different depths are added together to form the total
tower signal. A cutaway view of one of the chambers
of the forward EM calorimeter [5], in which the
cathode pads together with the readout lines that
carry the signals from the pads to edge connectors on
the side of the chamber, can be seen in Fig. 5. A
chamber cross section is shown in Fig. 6. These
chambers are made by gluing aluminum T's together to
form U-channels, as shown in Fig. 6. The surface of
the printed circuit board closes the U-channel.
The proportional tube chambers in the endplugs
[3,4] are made from layers of individual conductive
plastic tubes (extruded polystyrene mixed with carbon
grains), which are glued to printed circuit boards.
The tube resistivity (about 100 kfd per square) is
high enough that the induced cathode signal will form
on the pads of the printed circuit board beyond the
3
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Jensen, H.B. CDF (Collider Detector at Fermilab) calorimetry, article, March 1, 1987; Batavia, Illinois. (https://digital.library.unt.edu/ark:/67531/metadc1207749/m1/4/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.