- Email: [email protected]
Development of a trigger system with scintillating fibers and SiPM readout for the AMADEUS experiment
ARTICLE IN PRESS Nuclear Instruments and Methods in Physics Research A 617 (2010) 434–435
Contents lists available at ScienceDirect
Nuclear Instruments and Methods in Physics Research A journal homepage: www.elsevier.com/locate/nima
Development of a trigger system with scintillating fibers and SiPM readout for the AMADEUS experiment O. Va zquez Doce , G. Corradi, A. Romero, A. Scordo, D. Tagnani Laboratori Nazionali di Frascati INFN, Frascati, Italy
a r t i c l e in f o
a b s t r a c t
Available online 7 July 2009
A prototype setup of scintillating fibers with silicon photomultipliers (SiPM) readout has been built and successfully operated. The implementation of such a setup as trigger system for the AMADEUS experiment is under study. Dedicated high voltage supply modules and pre-amplification cards have been built for the SiPM detectors and the whole setup has been tested in situ installed at the DAFNE accelerator as well as with a 90Sr beta source. The results of these tests are presented and complemented with Monte Carlo simulation. & 2009 Elsevier B.V. All rights reserved.
Keywords: SiPM Scintillating fibers Trigger system
1. Introduction The AMADEUS experiment [1] will perform for the first time full-acceptance studies of hadronic interactions of K in light nuclei. Special studies of the possible formation of kaonic clusters [2] will be done, which could provide information concerning the modification of the kaon mass and of the K N interaction in the nuclear medium [3]. A specific set of detectors will be integrated inside the inner 50 cm radius gap of KLOE spectrometer at the DAFNE accelerator in the Frascati laboratories. DAFNE [4] is an eþ e collider tuned to be a F meson factory, where kaons coming from the decay of the F are copiously produced in a back to back topology. After its recent upgrade, it has reached a peak luminosity of about 5 1032 cm2 s1 . The KLOE [6] detector is composed by a 4p drift chamber surrounded by an electromagnetic calorimeter. Two main components of an experimental setup are presently under study for the implementation of AMADEUS, a high gaseous density target and a trigger system made of scintillating fibers surrounding the beam pipe of the accelerator around the interaction point. It is planned to instrument a cylindrical double or quadruple-layered scintillating fiber device with a set of SiPM detectors placed at the edges of the fibers for light readout. The task of this trigger is to develop the acquisition for the whole system ðKLOE þ AMADEUSÞ once the signal of two oppositedirection kaons in coincidence are detected. The trigger system requirements include the operation in a high radiation environment, a good energy deposit identification and operation insensitivity under strong magnetic fields, since the
Corresponding author.
E-mail address: [email protected] (O. Va zquez Doce). 0168-9002/$ - see front matter & 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2009.07.001
KLOE spectrometer provides a field of B ¼ 1:6 T. Besides, a good timing resolution is specially important, in order to separate the time-of-flight for kaons with respect to the MIPs produced in the interaction point, with differences in arriving time of around 1 ns. Silicon photomultipliers (SiPM) [5] are recently developed type detectors consisting of hundreds of microsilicon APDs working in Geiger mode. The high gain, low voltage values needed, their good behavior in magnetic fields and high granularity made them ideal for the readout of thin scintillating fibers. In the case of AMADEUS, a single SiPM could read single fibers or bunches of them in function of the final architecture.
2. Test setup and electronics An experimental setup for test purposes has been built and dedicated electronic modules providing the high and low voltages for SiPM have been designed and produced as well, together with small size pre-amplificators for each single SiPM. These dedicated modules, produced under the NIM standard, provide an extremely accurate stability in the HV value. The alimentation source is built in two steps: the first one, of switching type at high regime, raises up the voltages from 12 to 90 V, and in the second stage a linear regulator allows to change from 60 to 80 the nominal values with low current consumption. This brings the possibility for working with different types of SiPM detectors, since the operation voltages differ in tens of volts depending on the chosen device. The output voltage is then stable within C0:1 mV, keeping the gain constant. A single circuit provides the voltages for 5 SiPM contemporaneously, the absorption of each module being 2 mA. Following SwitcherCAD simulation results the temperature does not introduce significative changes in the output voltage.
ARTICLE IN PRESS O. Va zquez Doce et al. / Nuclear Instruments and Methods in Physics Research A 617 (2010) 434–435
435
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34055
events
103
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Fig. 1. Uncovered view of the setup placed over a precision desk during the beta source tests.
The pre-amplificator is a MAXIM bonded chip, with a transimpedance gain of 6 kO. Mechanics dimensions are 10 19 mm of a multilayer card. The NIM modules provide then linear readout in analogic mode for the voltages and discriminator with variable threshold and time window, the control of the output voltage is being operated manually with a trimmer. Hamamatsu S10362-11-050U SiPMs and Bicron BCF-10 fibers were used in these measurements. The SiPM devices chosen have an effective area of 1 mm2 , 400 pixels, a gain of 7:5 105 with a peak sensitivity at 400 nm. Working biases are in the range 69–70 V. The BCF-10 scintillating fibers used are round shape with multiclad, 1 mm diameter and blue light emission (peak at 432 nm). Five fibers have been mounted in a mechanical support that also holds 10 SiPM and its pre-amplificators attached, reading the scintillating fibers from both edges. Two PVC pieces keep the fibers attached and coplanar with a fiber guide that provides the correct coupling with the readout devices—optical gel is applied—by profiting the natural flexibility of the fibers. Electronic crosstalk of the signal is eliminated by instrumenting the 3rd pin of the Hamamatsu SiPMs to the pre-amplificators, and has been proved to be negligible in laboratory tests. A picture of the setup when mounted in a precision table for tests with the 90Sr source can be seen in Fig. 1.
3. DAFNE and
90
Sr beta source tests
The response of the device and the SiPM þ fiber coupling has been characterized and studied both under the radiation coming from a 90Sr beta source and installed at DAFNE accelerator. Silicon photomultipliers are affected by ‘‘dark’’ signals which consist of pixels activated by thermal noise. Rates are very high for the single photoelectron peak ðC2 105 HzÞ and decrease exponentially for higher values. In practice, the energy released by the 546 keV and 2.3 MeV electrons from the 90Sr beta source passing through the fibers develops much higher light signals, where the dark noise rate is drastically reduced and does not
20
40
60
80
100
120
photoelectrons Fig. 2. Signal collected by a single fiber during the DAFNE test run. The bump around 80 photoelectronvolts corresponds to kaons.
disturb the measurement. The results of our studies show how dark count is negligible for peaks corresponding to more than 4C5 photoelectrons, which is the main value for the beta source signal. A Monte Carlo simulation of the whole setup has been tuned with the previous results in terms of energy deposit in the fibers. The simulation shows that the expected signal left by the 127 MeV kaons from the F decay should be a factor of around 8 times higher. This is confirmed with the results of the measurements in DAFNE. The experimental prototype has been recently installed below the SIDDHARTA experiment [7], 10 cm far from the interaction point. For this run the fibers have been covered by a black thin layer in order to avoid optical crosstalk between adjacent fibers. We used as trigger for our acquisition the signal from the kaon monitor of SIDDHARTA, which consists of two scintillators placed over and below the beam pipe. A signal in coincidence in the two scintillators reveals the passage of kaons with a 95% efficiency. As the dimensions of our fibers are small compared with the scintillators ðC100 cm2 Þ, the kaon signal rate in a single fiber is expected to be very low. In Fig. 2 the collected signal for one single fiber is plotted in logarithmic scale. The kaon’s signal is clearly visible around 80 photoelectrons with the expected low rate and high number of photoelectrons. The lower number of photoelectrons region is produced by the signal of MIPs coming from DAFNE, and machine background signals entering the time window (150 ns) of our DAQ. References [1] [2] [3] [4] [5] [6] [7]
AMADEUS Letter of Intent /http://www.lnf.infn.it/esperimenti/siddharta/S. Y. Akaishi, T. Yamazaki, Phys. Rev. C 65 (2002) 044005. A. Dote, T. Hyodo, W. Weise, Nucl. Phys. A 804 (2008) 197. M. Zobov, et al., arXiv:0802.2667. Z. Sadygov, et al., Nucl. Instr. and Meth. A 567 (2006) 70. M. Adinolfi, et al., Nucl. Instr. and Meth. A 488 (2002) 51. C. Curceanu, et al., Eur. Phys. J. A 31 (2007) 537.
Contents lists available at ScienceDirect
Nuclear Instruments and Methods in Physics Research A journal homepage: www.elsevier.com/locate/nima
Development of a trigger system with scintillating fibers and SiPM readout for the AMADEUS experiment O. Va zquez Doce , G. Corradi, A. Romero, A. Scordo, D. Tagnani Laboratori Nazionali di Frascati INFN, Frascati, Italy
a r t i c l e in f o
a b s t r a c t
Available online 7 July 2009
A prototype setup of scintillating fibers with silicon photomultipliers (SiPM) readout has been built and successfully operated. The implementation of such a setup as trigger system for the AMADEUS experiment is under study. Dedicated high voltage supply modules and pre-amplification cards have been built for the SiPM detectors and the whole setup has been tested in situ installed at the DAFNE accelerator as well as with a 90Sr beta source. The results of these tests are presented and complemented with Monte Carlo simulation. & 2009 Elsevier B.V. All rights reserved.
Keywords: SiPM Scintillating fibers Trigger system
1. Introduction The AMADEUS experiment [1] will perform for the first time full-acceptance studies of hadronic interactions of K in light nuclei. Special studies of the possible formation of kaonic clusters [2] will be done, which could provide information concerning the modification of the kaon mass and of the K N interaction in the nuclear medium [3]. A specific set of detectors will be integrated inside the inner 50 cm radius gap of KLOE spectrometer at the DAFNE accelerator in the Frascati laboratories. DAFNE [4] is an eþ e collider tuned to be a F meson factory, where kaons coming from the decay of the F are copiously produced in a back to back topology. After its recent upgrade, it has reached a peak luminosity of about 5 1032 cm2 s1 . The KLOE [6] detector is composed by a 4p drift chamber surrounded by an electromagnetic calorimeter. Two main components of an experimental setup are presently under study for the implementation of AMADEUS, a high gaseous density target and a trigger system made of scintillating fibers surrounding the beam pipe of the accelerator around the interaction point. It is planned to instrument a cylindrical double or quadruple-layered scintillating fiber device with a set of SiPM detectors placed at the edges of the fibers for light readout. The task of this trigger is to develop the acquisition for the whole system ðKLOE þ AMADEUSÞ once the signal of two oppositedirection kaons in coincidence are detected. The trigger system requirements include the operation in a high radiation environment, a good energy deposit identification and operation insensitivity under strong magnetic fields, since the
Corresponding author.
E-mail address: [email protected] (O. Va zquez Doce). 0168-9002/$ - see front matter & 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2009.07.001
KLOE spectrometer provides a field of B ¼ 1:6 T. Besides, a good timing resolution is specially important, in order to separate the time-of-flight for kaons with respect to the MIPs produced in the interaction point, with differences in arriving time of around 1 ns. Silicon photomultipliers (SiPM) [5] are recently developed type detectors consisting of hundreds of microsilicon APDs working in Geiger mode. The high gain, low voltage values needed, their good behavior in magnetic fields and high granularity made them ideal for the readout of thin scintillating fibers. In the case of AMADEUS, a single SiPM could read single fibers or bunches of them in function of the final architecture.
2. Test setup and electronics An experimental setup for test purposes has been built and dedicated electronic modules providing the high and low voltages for SiPM have been designed and produced as well, together with small size pre-amplificators for each single SiPM. These dedicated modules, produced under the NIM standard, provide an extremely accurate stability in the HV value. The alimentation source is built in two steps: the first one, of switching type at high regime, raises up the voltages from 12 to 90 V, and in the second stage a linear regulator allows to change from 60 to 80 the nominal values with low current consumption. This brings the possibility for working with different types of SiPM detectors, since the operation voltages differ in tens of volts depending on the chosen device. The output voltage is then stable within C0:1 mV, keeping the gain constant. A single circuit provides the voltages for 5 SiPM contemporaneously, the absorption of each module being 2 mA. Following SwitcherCAD simulation results the temperature does not introduce significative changes in the output voltage.
ARTICLE IN PRESS O. Va zquez Doce et al. / Nuclear Instruments and Methods in Physics Research A 617 (2010) 434–435
435
Entries
34055
events
103
102
10
1 0
Fig. 1. Uncovered view of the setup placed over a precision desk during the beta source tests.
The pre-amplificator is a MAXIM bonded chip, with a transimpedance gain of 6 kO. Mechanics dimensions are 10 19 mm of a multilayer card. The NIM modules provide then linear readout in analogic mode for the voltages and discriminator with variable threshold and time window, the control of the output voltage is being operated manually with a trimmer. Hamamatsu S10362-11-050U SiPMs and Bicron BCF-10 fibers were used in these measurements. The SiPM devices chosen have an effective area of 1 mm2 , 400 pixels, a gain of 7:5 105 with a peak sensitivity at 400 nm. Working biases are in the range 69–70 V. The BCF-10 scintillating fibers used are round shape with multiclad, 1 mm diameter and blue light emission (peak at 432 nm). Five fibers have been mounted in a mechanical support that also holds 10 SiPM and its pre-amplificators attached, reading the scintillating fibers from both edges. Two PVC pieces keep the fibers attached and coplanar with a fiber guide that provides the correct coupling with the readout devices—optical gel is applied—by profiting the natural flexibility of the fibers. Electronic crosstalk of the signal is eliminated by instrumenting the 3rd pin of the Hamamatsu SiPMs to the pre-amplificators, and has been proved to be negligible in laboratory tests. A picture of the setup when mounted in a precision table for tests with the 90Sr source can be seen in Fig. 1.
3. DAFNE and
90
Sr beta source tests
The response of the device and the SiPM þ fiber coupling has been characterized and studied both under the radiation coming from a 90Sr beta source and installed at DAFNE accelerator. Silicon photomultipliers are affected by ‘‘dark’’ signals which consist of pixels activated by thermal noise. Rates are very high for the single photoelectron peak ðC2 105 HzÞ and decrease exponentially for higher values. In practice, the energy released by the 546 keV and 2.3 MeV electrons from the 90Sr beta source passing through the fibers develops much higher light signals, where the dark noise rate is drastically reduced and does not
20
40
60
80
100
120
photoelectrons Fig. 2. Signal collected by a single fiber during the DAFNE test run. The bump around 80 photoelectronvolts corresponds to kaons.
disturb the measurement. The results of our studies show how dark count is negligible for peaks corresponding to more than 4C5 photoelectrons, which is the main value for the beta source signal. A Monte Carlo simulation of the whole setup has been tuned with the previous results in terms of energy deposit in the fibers. The simulation shows that the expected signal left by the 127 MeV kaons from the F decay should be a factor of around 8 times higher. This is confirmed with the results of the measurements in DAFNE. The experimental prototype has been recently installed below the SIDDHARTA experiment [7], 10 cm far from the interaction point. For this run the fibers have been covered by a black thin layer in order to avoid optical crosstalk between adjacent fibers. We used as trigger for our acquisition the signal from the kaon monitor of SIDDHARTA, which consists of two scintillators placed over and below the beam pipe. A signal in coincidence in the two scintillators reveals the passage of kaons with a 95% efficiency. As the dimensions of our fibers are small compared with the scintillators ðC100 cm2 Þ, the kaon signal rate in a single fiber is expected to be very low. In Fig. 2 the collected signal for one single fiber is plotted in logarithmic scale. The kaon’s signal is clearly visible around 80 photoelectrons with the expected low rate and high number of photoelectrons. The lower number of photoelectrons region is produced by the signal of MIPs coming from DAFNE, and machine background signals entering the time window (150 ns) of our DAQ. References [1] [2] [3] [4] [5] [6] [7]
AMADEUS Letter of Intent /http://www.lnf.infn.it/esperimenti/siddharta/S. Y. Akaishi, T. Yamazaki, Phys. Rev. C 65 (2002) 044005. A. Dote, T. Hyodo, W. Weise, Nucl. Phys. A 804 (2008) 197. M. Zobov, et al., arXiv:0802.2667. Z. Sadygov, et al., Nucl. Instr. and Meth. A 567 (2006) 70. M. Adinolfi, et al., Nucl. Instr. and Meth. A 488 (2002) 51. C. Curceanu, et al., Eur. Phys. J. A 31 (2007) 537.