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Preliminary tests of a new shower detector
Nuclear Instruments and Methods 173 (1980) 259-260 © North-Holland Publishing Company
PRELIMINARY TESTS OF A NEW SHOWER DETECTOR Andrzej K. DRUKIER Zentralinstitut f. Tieftemperaturenforschung, 8046 Garching b. Munich, FR G Received 4 February 1980
The preliminary tests of superheated superconducting colloid (SSC) as the shower detector have been performed using relativistic electrons with energies between 0.1 and 6.0 GeV. These tests confkm that: the total number of grains which change state is proportional to the energy of the electrons and that the number of grains which flip is very big, e.g. for a single electron with an energy of 6.0 GeV some 5 × l0 s grains of diameter of a few microns change state.
(iii) easier electrons versus hadrons identification; (iv) is more compact (by factor 3 - 5 ) and may be cheaper. Recently, the preliminary tests o f SSC as the shower detector have been performed using the relativistic electrons with energies between 1.0 and 6.0 GeV. These tests essentially confirm that the total number of grains which change state is proportional to the energy of electrons, and that the number of grains which flip is very big, e.g. for a single electron of 6.0 GeV some 5 × 10 s grains of a few microns diameter change state. Thus it should be relatively easy to see the signal due to a single particle and the energy resolution should be excellent.
1. Introduction Superheated superconducting colloid (SSC) is a new particle detector which consists of small, few microns diameter, superconducting grains immersed in dielectric. The transition of grains to the normal state has been observed under irradiation. This effect is due to local heating caused by the passage of particle. SSC was tested with radioactive sources [1 ] and successfully used to detect the transition radiation of relativistic electrons [2]. We have suggested that SSC be used as a shower detector [3]. It is expected that SSC will have an energy resolution comparable with or better than NaI shower detectors i.e. about 3%/E where E is in GeV. Even at relatively low energies, E ~< 500 MeV, SSC should have energy resolution better than 5%. Furthermore, an SSC shower detector may be cheaper and bigger than NaI detectors. Due to the very high density, 1 0 - 1 5 g cm -a, and very high atomic number, Z / > 70, the radiation length of SSC is very short, Xo = 5 - 8 ram. Taking into account the submillimetric intrinsic spatial resolution of SSC, spatial resolution as good as 1 m m seems to be possible. Detailed information about the longitudinal and transverse development of the shower can be obtained and electron versus hadron identification should be easier in SSC than in existing calorimeters. When compared with sandwich detectors, e.g. lead + liquid argon, the SSC shower detector has the following advantages: (i) much better energy resolution; (ii) excellent spatial resolution;
2. Experimental The SSC sample consisted of 225 g of HgO, 45 g of paraffme wax and 3.5 g of indium grains. It was a cylinder i0 cm long and 2.8 cm in diameter. The radiation length for this medium is about 0.8 cm, i.e. the sample was only 12.5 radiation lengths which permits only partial confiment of the shower. The average' diameter of the grains was 4.2/am and about 80% of grains had a diameter between 3.0 and 6.0/am. The filling factor, i.e. the ratio of the volume of the grains to the volume of the sample, was 0.7% thus there were about 2.0 × I0 la grains in the sample. The filling factor of 0.7% is far from optimal and in practical detectors the filling factors of 2 0 - 3 0 % will be used. 259
260
A.K. Drukier / Preliminary tests o f a n e w shower detector
3. Discussion In indium, the transition between the superconducting and normal states is of the first order, i.e. the superheated state exists. Due to an energy barier which is much higher than the temperature fluctuations in a liquid helium bath, the grains remain in the metastable state when in a magnetic field He ~
- 21 A/d/b/ ~ 21 V * /Vsample - -
where V* is the total volume of the grains which change state. The beam which we used was of low intensity, about 40 electrons/min at 1.0 GeV and about 100 electrons/min at 6.0 GeV. The total number of particles which enter the sample has been measured using the triple coincidence hodoscope of plastic scintillators. We studied the effect of irradiation at 2.5 K. The temperature fluctuations was about 0.05 K which accounts for frequency drift of about 0.5 Hz min -1, whereas the oscillator frequency was 1.2 Mhz. The effects of irradiation have been integrated for 10 min, after which the magnetic field has been recycled and further measurement without the beam has followed. The change of the frequency per one particle versus the particle energy is plotted in fig. 1.
A~ ( H z/erect ron ) ,0.6
[
05
[
0~
t
0.3
t
t
0.2
[
t t 0.1
!
2
3
~. ,s 6.
E(aeV)
Fig. 1.
The measurement without the beam gives the error bars as presented in the figure. The development of a shower due to an electron with energy of 6.0 GeV changes the state of about 5 X l0 s grains. Both, the linear dependence of the magnetic permeability and the big number of grains which flips, are in agreement with the calculus presented in ref. [3]. We would like to thank Drs. Kessler, Koch and Schultz of DESY for help during the experiment.
References [1] C. Valette, PhD, thesis, Orsay 1972; A.K. Drukier, PhD, thesis, Copenhagen 1973; A.K. Drukier and C. Valette, Nucl. Instr. and Meth. 105 (1972) 285; D.I. Chase et al. Proc. 2nd ISPRA Nuclear Electronics Symp. Stessa (1975) p. 29. [2] A.K. Drukier et al. Lett. Nuovo Cim. 14 (1975) 300; A.K. Drukier and L.C.L. Yuan Nucl. Instr. and Meth. 138 (1976) 213; A.K. Drukier, Proc. Int. Symp. Transition Radiation, Erevan (1977) Nucl. Instr. and Meth. [3] A.K. Drukier, Nucl. Instr. and Method. 154 (1978) 83.
PRELIMINARY TESTS OF A NEW SHOWER DETECTOR Andrzej K. DRUKIER Zentralinstitut f. Tieftemperaturenforschung, 8046 Garching b. Munich, FR G Received 4 February 1980
The preliminary tests of superheated superconducting colloid (SSC) as the shower detector have been performed using relativistic electrons with energies between 0.1 and 6.0 GeV. These tests confkm that: the total number of grains which change state is proportional to the energy of the electrons and that the number of grains which flip is very big, e.g. for a single electron with an energy of 6.0 GeV some 5 × l0 s grains of diameter of a few microns change state.
(iii) easier electrons versus hadrons identification; (iv) is more compact (by factor 3 - 5 ) and may be cheaper. Recently, the preliminary tests o f SSC as the shower detector have been performed using the relativistic electrons with energies between 1.0 and 6.0 GeV. These tests essentially confirm that the total number of grains which change state is proportional to the energy of electrons, and that the number of grains which flip is very big, e.g. for a single electron of 6.0 GeV some 5 × 10 s grains of a few microns diameter change state. Thus it should be relatively easy to see the signal due to a single particle and the energy resolution should be excellent.
1. Introduction Superheated superconducting colloid (SSC) is a new particle detector which consists of small, few microns diameter, superconducting grains immersed in dielectric. The transition of grains to the normal state has been observed under irradiation. This effect is due to local heating caused by the passage of particle. SSC was tested with radioactive sources [1 ] and successfully used to detect the transition radiation of relativistic electrons [2]. We have suggested that SSC be used as a shower detector [3]. It is expected that SSC will have an energy resolution comparable with or better than NaI shower detectors i.e. about 3%/E where E is in GeV. Even at relatively low energies, E ~< 500 MeV, SSC should have energy resolution better than 5%. Furthermore, an SSC shower detector may be cheaper and bigger than NaI detectors. Due to the very high density, 1 0 - 1 5 g cm -a, and very high atomic number, Z / > 70, the radiation length of SSC is very short, Xo = 5 - 8 ram. Taking into account the submillimetric intrinsic spatial resolution of SSC, spatial resolution as good as 1 m m seems to be possible. Detailed information about the longitudinal and transverse development of the shower can be obtained and electron versus hadron identification should be easier in SSC than in existing calorimeters. When compared with sandwich detectors, e.g. lead + liquid argon, the SSC shower detector has the following advantages: (i) much better energy resolution; (ii) excellent spatial resolution;
2. Experimental The SSC sample consisted of 225 g of HgO, 45 g of paraffme wax and 3.5 g of indium grains. It was a cylinder i0 cm long and 2.8 cm in diameter. The radiation length for this medium is about 0.8 cm, i.e. the sample was only 12.5 radiation lengths which permits only partial confiment of the shower. The average' diameter of the grains was 4.2/am and about 80% of grains had a diameter between 3.0 and 6.0/am. The filling factor, i.e. the ratio of the volume of the grains to the volume of the sample, was 0.7% thus there were about 2.0 × I0 la grains in the sample. The filling factor of 0.7% is far from optimal and in practical detectors the filling factors of 2 0 - 3 0 % will be used. 259
260
A.K. Drukier / Preliminary tests o f a n e w shower detector
3. Discussion In indium, the transition between the superconducting and normal states is of the first order, i.e. the superheated state exists. Due to an energy barier which is much higher than the temperature fluctuations in a liquid helium bath, the grains remain in the metastable state when in a magnetic field He ~
- 21 A/d/b/ ~ 21 V * /Vsample - -
where V* is the total volume of the grains which change state. The beam which we used was of low intensity, about 40 electrons/min at 1.0 GeV and about 100 electrons/min at 6.0 GeV. The total number of particles which enter the sample has been measured using the triple coincidence hodoscope of plastic scintillators. We studied the effect of irradiation at 2.5 K. The temperature fluctuations was about 0.05 K which accounts for frequency drift of about 0.5 Hz min -1, whereas the oscillator frequency was 1.2 Mhz. The effects of irradiation have been integrated for 10 min, after which the magnetic field has been recycled and further measurement without the beam has followed. The change of the frequency per one particle versus the particle energy is plotted in fig. 1.
A~ ( H z/erect ron ) ,0.6
[
05
[
0~
t
0.3
t
t
0.2
[
t t 0.1
!
2
3
~. ,s 6.
E(aeV)
Fig. 1.
The measurement without the beam gives the error bars as presented in the figure. The development of a shower due to an electron with energy of 6.0 GeV changes the state of about 5 X l0 s grains. Both, the linear dependence of the magnetic permeability and the big number of grains which flips, are in agreement with the calculus presented in ref. [3]. We would like to thank Drs. Kessler, Koch and Schultz of DESY for help during the experiment.
References [1] C. Valette, PhD, thesis, Orsay 1972; A.K. Drukier, PhD, thesis, Copenhagen 1973; A.K. Drukier and C. Valette, Nucl. Instr. and Meth. 105 (1972) 285; D.I. Chase et al. Proc. 2nd ISPRA Nuclear Electronics Symp. Stessa (1975) p. 29. [2] A.K. Drukier et al. Lett. Nuovo Cim. 14 (1975) 300; A.K. Drukier and L.C.L. Yuan Nucl. Instr. and Meth. 138 (1976) 213; A.K. Drukier, Proc. Int. Symp. Transition Radiation, Erevan (1977) Nucl. Instr. and Meth. [3] A.K. Drukier, Nucl. Instr. and Method. 154 (1978) 83.