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Hybrid shower counters for CDF
Nuclear Instruments and Methods 176 (1980) 345-347 © North-Holland Publshing Comapny
HYBRID SHOWER COUNTERS FOR CDF
Lawrence NODULMAN * Argonne National Laboratory, Argonne, Illinois 60439, U.S.A.
A hybrid scintillator/strip chamber electromagnetic calorimeter has been proposed for the Collider Detector Facility at Fermilab. Large modules of lead/scintillator with wavebar readout are to contain one or more bidimensional wire chambers near shower maximum. Results of the ongoing program of computer simulation and prototype testing are discussed.
This paper describes a part o f a series o f design studies for the Collider Detector Facility to be established at Fennilab. The superconducting 1 TeV ring now under construction will be" used as a storage ring to study proton antiproton collisions at up to 2 TeV in the center o f mass. A group o f physicists from several institutions in the USA, Japan, and Italy [1] is developing a design for the large scale facility to be installed in the first available interaction region. The design of the Collider Detector Facility is based on a large 1.5 T solenoid instrumented with tracking, electromagnetic and hadron calorimetry, and muon identification [2]. A preliminary version is shown in fig. 1. The hybrid design has been developed for the central electromagnetic shower c o u n t e r system. The design o f a hybrid module is shown in fig. 2. Each module covers one eighth o f the azimuth and one fifth o f the length o f the solenoid and is backed b y a hadron calorimeter module. Lead sheets and acrylic scintillator alternate, with the scintillator divided into eight azimuthal bands which are read out by means o f wave shifters at b o t h longitudinal ends o f each strip. Two multiwire proportional chambers are inserted at depths o f approximately 3 and 6 radiation lengths. The wire chambers have two dimensional analog readout to provide measurements o f the position o f conversions and a crude energy determination which can be used to sort out the scintillator information in detail and aid in hadron/electron discrimination. The hybrid design was developed by a group from Argonne and Fermilab [3] following test beam
studies at Fermilab. Individually instrumented scintillators or wire chambers were alternated with lead sheets and exposed to pions and electrons at momenta from 5 to 45 GeV/c. A single chamber at 6 radiation lengths, near shower maximum, was found to measure electron position to +4 mm, energy to -+30%, and in conjunction with total pulse height, to give a pion rejection o f ( 2 - 3 ) × 10 -4. The second chamber was added to the design after tests at the ZGS with radiator and one chamber [4] exposed to pions and electrons from 1 to 5 GeV/c showed problems o f nonlinearity and inefficiency for low energy as shower maximum occurs at shallower depth. In addition the combination o f two chambers can be used to point back to the event vertex in order to discriminate against non b e a m - b e a m background. An important issue is whether this design, using strip chambers with pulse height matchings, will pro-
D
AP CALORIMETRY
LTRACKING SYSTEM CENTRAL CALORIMETRY
* Work perlbrmed under the auspices of the United States Department of Energy.
Fig. 1. Preliminary design of the Collider Detector Facility. 345
VIII. PARTICLE IDENTIFICATION
L.Nodulman / Hybrid shower counters
346 END VIEW
SIDE VIEW LEAD AND SCINTILLATOR
WAVE SHIFTER BARS STRIP CHAMBERS I"
lm
"1
Fig. 2. Design of the hybrid shower counter module.
vide adequate information for high energy jets. One strategy to measure jets accurately is to combine the .charged particle magnetic measurement (6p/p= 0.2% × p in GeV) with the shower counter measurements (6E/E = 12%/x/E in GeV). Preliminary Monte Carlo studies reconstructing the energy and moments of 35, 50 and 100 GeV F i e l d - F e y n m a n jets [5], with internal p± set to 400 MeV/c, reveal the systematics of the shower counter [6]. In general the worst source of errors, other than the jet defining algorithm, comes in sorting out energy from charged particle interactions in the shower counter. This effect is serious enough for these compact jets at 100 GeV that a reasonably simple hadron calorimeter (100%/ x/E in GeV) becomes competitive. At 35 GeV, with a chamber at 6 radiation lengths only, the low energy photon systematics dominate. The two view matching with assumed pulse height correlation o f -+6-8% is not a limiting factor. Further studies are continuing. A strip chamber with one centimeter spacing, approximately shower size, needed to be developed for this application. Since one layer o f chamber corresponds to 48 m 2, the chambers should be inexpensive and easy to construct. Access to the chambers will be extremely painful, so reliability is very important. Dead space along edges must be kept minimal. These requirements may be met by adding strips
to a chamber of ribbed construction as shown in fig. 3. The ease of such construction and possible undesirable effects of the large capacitance between the strips and ribs have been studied by constructing and testing a 50 cm 2 prototype. Ribs were machined in an aluminum plate for the prototype; mass production would use extrusions. After cleaning and stringing wires, a first layer of epoxy was applied to the ribs and later tested for electrical insulation. Then two 1.6 mm G10 strip boards were glued to tire ribs. A 1 mm crack between boards was left for source tests. The resulting cells are 9 mm by 6 mm with 25 #m gold coated tungsten wire at the center as is shown in fig. 3. The capacitance of one 50 cm by 1 cm strip was measured to be 800 pF. For testing, pairs of strips were connected together to simulate the capacitance of a 1 m strip. Individual wires are connected to high voltage by 1 M ~ and read out through 200 pF. A mixture with equal parts of argon and ethane gas was used for testing. Charge sensitive amplifiers based on a design o f M. Hibbard of Fermilab as part o f a CDF prototype system were used [7]. The gate for both ADC and computer interrupt
t, °
+ ~ t ,,t"~,~'"
~
PEDESTAL ANODE
ISOOtlbl
I I I r I I I I
r-r rr
i ' r I
4
E 1000 V
~
GIO
,,.5-,
J
P
N T
STRIPS
S 500 f ~O,2 mrn/~
I
*
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"
£rnmRIB-Jz~, £rnm RIB -J
z~,
oir o4
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ALUM I NUM
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Fig. 3. Prototype strip chamber cross section.
EJ~_lllllJ o 6
r 0.8
II
I
I
i~1
~.o
,2
,
I i, ,4
J,
I I
CATHODE/ANODE
Fig. 4. Chamber response to ss Fe source: (a) cathode versus anode pulse height, (b) cathode/anode pulse height ratio.
L.Nodulman / ttybrid shower counters
was generated b y resistively splitting a wire signal for discrimination. Source tests were typically conducted at 1.8 k V giving a gas gain o f 10 4. Cathode signal rise time is not significantly degraded compared to wire signals and the amplitude ratio is approximately 1 : 3. Uniformity o f response was measured at points along the crack between the cathode boards and found to be within -+4%. Resolution and pulse height correlation are illustrated in fig. 4. The two bands in cathode versus anode pulse height correspond to the 5.9 and 3.0 keV photons from SSFe on the near and far side o f the wire from the strip cathode. The full width at half maximum for the wire response to the 5.9 keV X-ray is 16% and the correlation, taken from one peak o f the pulse height ratio distribution, is +-5%. Current plans call for tests o f the chamber as part o f a hybrid shower counter in the M5 beam at Fermilab. Monte Carlo studies to determine the suitability o f the hybrid design for Collider physics are continuing.
347
R. Thatcher and E. Walschon for their help in this work.
References [1] Participating institutions presently include Fermilab, Argonne National Laboratory, California Institute of Technology, Purdue, University of Chicago, University of Illinois, University of Wisconsin, KEK, Tsukuba University, Tokyo University, Frascati, and INFN Pisa. [2] C. Ankenbrandt et al., Femilab internal report (May 1979) (unpublished). [3] M. Atac, R. Diebold, R. Loveless, B. Mnsgrave, J. Sauer and R. Singer, Fermilab internal report CDF-27 (1978) (unpublished). [4] L. Nodulman, CDF-33 (1979) (unpublished). [5] R.D. Field, R.P. Feynman, Nucl. Phys. B136 (1978) 1. [6] L. Nodulman, CDF-41 (1979) (unpublished). [7] T.F. Droege, F. Lobkowicz and Fukushima, IEEE Trans. Nucl. Sci. NS-25 1 (t978); T.F. Droege, M.C. Hibbard, C.A. Nelson, P.A. Thompson, Y. Makdisi and R. Lipton, Proc. 1979 Nuclear science Syrup., IEEE Trans. Nucl. Sci. (to be publsihed).
I would like to thank M. Atac, D.S. Ayres, R. Diebold, I. Gaines, L. Filips, B. Musgrave, J. Sauer,
VIII. PARTICLE IDENTIFICATION
HYBRID SHOWER COUNTERS FOR CDF
Lawrence NODULMAN * Argonne National Laboratory, Argonne, Illinois 60439, U.S.A.
A hybrid scintillator/strip chamber electromagnetic calorimeter has been proposed for the Collider Detector Facility at Fermilab. Large modules of lead/scintillator with wavebar readout are to contain one or more bidimensional wire chambers near shower maximum. Results of the ongoing program of computer simulation and prototype testing are discussed.
This paper describes a part o f a series o f design studies for the Collider Detector Facility to be established at Fennilab. The superconducting 1 TeV ring now under construction will be" used as a storage ring to study proton antiproton collisions at up to 2 TeV in the center o f mass. A group o f physicists from several institutions in the USA, Japan, and Italy [1] is developing a design for the large scale facility to be installed in the first available interaction region. The design of the Collider Detector Facility is based on a large 1.5 T solenoid instrumented with tracking, electromagnetic and hadron calorimetry, and muon identification [2]. A preliminary version is shown in fig. 1. The hybrid design has been developed for the central electromagnetic shower c o u n t e r system. The design o f a hybrid module is shown in fig. 2. Each module covers one eighth o f the azimuth and one fifth o f the length o f the solenoid and is backed b y a hadron calorimeter module. Lead sheets and acrylic scintillator alternate, with the scintillator divided into eight azimuthal bands which are read out by means o f wave shifters at b o t h longitudinal ends o f each strip. Two multiwire proportional chambers are inserted at depths o f approximately 3 and 6 radiation lengths. The wire chambers have two dimensional analog readout to provide measurements o f the position o f conversions and a crude energy determination which can be used to sort out the scintillator information in detail and aid in hadron/electron discrimination. The hybrid design was developed by a group from Argonne and Fermilab [3] following test beam
studies at Fermilab. Individually instrumented scintillators or wire chambers were alternated with lead sheets and exposed to pions and electrons at momenta from 5 to 45 GeV/c. A single chamber at 6 radiation lengths, near shower maximum, was found to measure electron position to +4 mm, energy to -+30%, and in conjunction with total pulse height, to give a pion rejection o f ( 2 - 3 ) × 10 -4. The second chamber was added to the design after tests at the ZGS with radiator and one chamber [4] exposed to pions and electrons from 1 to 5 GeV/c showed problems o f nonlinearity and inefficiency for low energy as shower maximum occurs at shallower depth. In addition the combination o f two chambers can be used to point back to the event vertex in order to discriminate against non b e a m - b e a m background. An important issue is whether this design, using strip chambers with pulse height matchings, will pro-
D
AP CALORIMETRY
LTRACKING SYSTEM CENTRAL CALORIMETRY
* Work perlbrmed under the auspices of the United States Department of Energy.
Fig. 1. Preliminary design of the Collider Detector Facility. 345
VIII. PARTICLE IDENTIFICATION
L.Nodulman / Hybrid shower counters
346 END VIEW
SIDE VIEW LEAD AND SCINTILLATOR
WAVE SHIFTER BARS STRIP CHAMBERS I"
lm
"1
Fig. 2. Design of the hybrid shower counter module.
vide adequate information for high energy jets. One strategy to measure jets accurately is to combine the .charged particle magnetic measurement (6p/p= 0.2% × p in GeV) with the shower counter measurements (6E/E = 12%/x/E in GeV). Preliminary Monte Carlo studies reconstructing the energy and moments of 35, 50 and 100 GeV F i e l d - F e y n m a n jets [5], with internal p± set to 400 MeV/c, reveal the systematics of the shower counter [6]. In general the worst source of errors, other than the jet defining algorithm, comes in sorting out energy from charged particle interactions in the shower counter. This effect is serious enough for these compact jets at 100 GeV that a reasonably simple hadron calorimeter (100%/ x/E in GeV) becomes competitive. At 35 GeV, with a chamber at 6 radiation lengths only, the low energy photon systematics dominate. The two view matching with assumed pulse height correlation o f -+6-8% is not a limiting factor. Further studies are continuing. A strip chamber with one centimeter spacing, approximately shower size, needed to be developed for this application. Since one layer o f chamber corresponds to 48 m 2, the chambers should be inexpensive and easy to construct. Access to the chambers will be extremely painful, so reliability is very important. Dead space along edges must be kept minimal. These requirements may be met by adding strips
to a chamber of ribbed construction as shown in fig. 3. The ease of such construction and possible undesirable effects of the large capacitance between the strips and ribs have been studied by constructing and testing a 50 cm 2 prototype. Ribs were machined in an aluminum plate for the prototype; mass production would use extrusions. After cleaning and stringing wires, a first layer of epoxy was applied to the ribs and later tested for electrical insulation. Then two 1.6 mm G10 strip boards were glued to tire ribs. A 1 mm crack between boards was left for source tests. The resulting cells are 9 mm by 6 mm with 25 #m gold coated tungsten wire at the center as is shown in fig. 3. The capacitance of one 50 cm by 1 cm strip was measured to be 800 pF. For testing, pairs of strips were connected together to simulate the capacitance of a 1 m strip. Individual wires are connected to high voltage by 1 M ~ and read out through 200 pF. A mixture with equal parts of argon and ethane gas was used for testing. Charge sensitive amplifiers based on a design o f M. Hibbard of Fermilab as part o f a CDF prototype system were used [7]. The gate for both ADC and computer interrupt
t, °
+ ~ t ,,t"~,~'"
~
PEDESTAL ANODE
ISOOtlbl
I I I r I I I I
r-r rr
i ' r I
4
E 1000 V
~
GIO
,,.5-,
J
P
N T
STRIPS
S 500 f ~O,2 mrn/~
I
*
Gram
"
£rnmRIB-Jz~, £rnm RIB -J
z~,
oir o4
"~'~
ALUM I NUM
tcm
Fig. 3. Prototype strip chamber cross section.
EJ~_lllllJ o 6
r 0.8
II
I
I
i~1
~.o
,2
,
I i, ,4
J,
I I
CATHODE/ANODE
Fig. 4. Chamber response to ss Fe source: (a) cathode versus anode pulse height, (b) cathode/anode pulse height ratio.
L.Nodulman / ttybrid shower counters
was generated b y resistively splitting a wire signal for discrimination. Source tests were typically conducted at 1.8 k V giving a gas gain o f 10 4. Cathode signal rise time is not significantly degraded compared to wire signals and the amplitude ratio is approximately 1 : 3. Uniformity o f response was measured at points along the crack between the cathode boards and found to be within -+4%. Resolution and pulse height correlation are illustrated in fig. 4. The two bands in cathode versus anode pulse height correspond to the 5.9 and 3.0 keV photons from SSFe on the near and far side o f the wire from the strip cathode. The full width at half maximum for the wire response to the 5.9 keV X-ray is 16% and the correlation, taken from one peak o f the pulse height ratio distribution, is +-5%. Current plans call for tests o f the chamber as part o f a hybrid shower counter in the M5 beam at Fermilab. Monte Carlo studies to determine the suitability o f the hybrid design for Collider physics are continuing.
347
R. Thatcher and E. Walschon for their help in this work.
References [1] Participating institutions presently include Fermilab, Argonne National Laboratory, California Institute of Technology, Purdue, University of Chicago, University of Illinois, University of Wisconsin, KEK, Tsukuba University, Tokyo University, Frascati, and INFN Pisa. [2] C. Ankenbrandt et al., Femilab internal report (May 1979) (unpublished). [3] M. Atac, R. Diebold, R. Loveless, B. Mnsgrave, J. Sauer and R. Singer, Fermilab internal report CDF-27 (1978) (unpublished). [4] L. Nodulman, CDF-33 (1979) (unpublished). [5] R.D. Field, R.P. Feynman, Nucl. Phys. B136 (1978) 1. [6] L. Nodulman, CDF-41 (1979) (unpublished). [7] T.F. Droege, F. Lobkowicz and Fukushima, IEEE Trans. Nucl. Sci. NS-25 1 (t978); T.F. Droege, M.C. Hibbard, C.A. Nelson, P.A. Thompson, Y. Makdisi and R. Lipton, Proc. 1979 Nuclear science Syrup., IEEE Trans. Nucl. Sci. (to be publsihed).
I would like to thank M. Atac, D.S. Ayres, R. Diebold, I. Gaines, L. Filips, B. Musgrave, J. Sauer,
VIII. PARTICLE IDENTIFICATION