- Email: [email protected]
Multi-sector scintillation detector for investigations of extensive air showers
ARTICLE IN PRESS Nuclear Instruments and Methods in Physics Research A 598 (2009) 296–299
Contents lists available at ScienceDirect
Nuclear Instruments and Methods in Physics Research A journal homepage: www.elsevier.com/locate/nima
Multi-sector scintillation detector for investigations of extensive air showers E.E. Yanson a,, S.P. Denisov b, Yu.V. Gilitsky b, V.V. Kindin a, R.P. Kokoulin a, K.G. Kompaniets a, V.V. Lipaev b, A.A. Matyushin b, A.V. Ovchinnikov a, A.A. Petrukhin a, N.N. Prokopenko b, M.M. Soldatov b, A.N. Sytin b a b
Moscow Engineering Physics Institute (State University), Moscow 115409, Russian Federation Institute for High Energy Physics, Protvino 142284, Russian Federation
a r t i c l e in f o
a b s t r a c t
Available online 19 August 2008
A new type of scintillation detector for shower arrays is considered. The detector represents an octagonal scintillation assembly with total area 1 m2 divided into sectors. Thickness of the plastic is 20 mm. The light is collected by wavelength shifter bars to the photomultiplier, which is located in the center of the detector. A solution to ensure the uniformity of light collection for any coordinate is proposed. Front-end electronics of the detector consists of the controller, the measuring part (QDC, TDC), the system of calibration and the HV converter. The data acquisition system is based on CAN-open standard. There is also a system of temperature stabilization that guarantees not more than 0.51 deviation of the temperature of measuring part elements. Measuring electronics allows obtaining the dynamic range from 1 up to 104 particles and 1 ns time digitization. The time resolution of the detector is about 3 ns. & 2008 Elsevier B.V. All rights reserved.
Keywords: Scintillation detector Shower array Uniformity of the response
1. Introduction Investigations of extensive air showers (EAS) give information about primary cosmic-ray flux and some characteristics of hadron interactions (cross-section, multiplicity, etc.) at energies that are not accessible currently and cannot be reached in nearest accelerator experiments (more than 14 TeV in the center of mass system). Usually EAS at small zenith angles (near-vertical direction) are investigated by using distributed systems of standard scintillation counters with thicknesses of 5 cm. Investigations of inclined EAS are more complicated taking into account the following circumstances. Firstly, the flux of inclined showers with the same particle number is less than in the vertical direction, and decreases with the increase of zenith angle. Secondly, the ratio between the muon number and the electron number increases while the total number of particles decreases. Thirdly, traditional (horizontal) orientation of scintillation detectors does not allow one to correctly measure the number of shower particles in inclined EAS. At the same time, investigations of inclined showers allow one to obtain new information about EAS development and to explore higher energies of primary particles. For conduction of such type of experiments, two main conditions are required: the presence of the central detector, which allows evaluating the energy of muons
Corresponding author. Tel.: +7495 323 9040; fax: +7 495 324 8780.
E-mail address: [email protected] (E.E. Yanson). 0168-9002/$ - see front matter & 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2008.08.026
in inclined showers, and a shower array of scintillation detectors, which can change orientation from horizontal to vertical. Suitable central detectors for this purpose exist in IHEP, Protvino (liquid-argon spectrometer BARS) and in Moscow Engineering Physics Institute (MEPhI), Moscow (Cherenkov water detector NEVOD). Firstly, the project of BARS-EAS was developed and then another project NEVOD-EAS appeared.
2. EAS-BARS project The EAS-BARS experiment (MEPhI, IHEP, INR) is aimed at measurements of various EAS component characteristics in the ‘‘knee’’ region (1015–1017 eV). Shower array includes 48 detectors deployed over the area of 220 m 60 m around liquid-argon ionization calorimeter BARS (18 m length and 3 m in diameter) located at the neutrino channel of the IHEP accelerator (Protvino). Arrangement of detectors of the electron–photon component and of the BARS spectrometer is shown in Fig. 1. Large area of registration (450 m2), a high spatial resolution (6 cm), the ability to register separate particles and cascades, an opportunity to trace their development in depth (thickness of the detector ranges from 500 up to 3000 g/cm2) and low threshold calorimetry allow the use of the spectrometer BARS for the solution of problems of cosmic ray physics [1]. Event registration by the combined setup (spectrometer BARS+shower array) is triggered by the signal from a scheme of coincidences of shower detectors. The setup can detect not only near-vertical EAS (up to 401) but also inclined EAS, which gives a possibility of
ARTICLE IN PRESS E.E. Yanson et al. / Nuclear Instruments and Methods in Physics Research A 598 (2009) 296–299
297
Fig. 1. Shower array and BARS spectrometer.
investigating transition from usual electron–photon showers to pure muon showers.
3. NEVOD-EAS project The NEVOD-EAS setup will be deployed in the MEPhI campus. The total area of the shower array is about 3 104 m2, which is determined by the intensity of cosmic rays at the knee energies. Experimental complex NEVOD for studies of new physical processes around the knee of the energy spectrum of cosmic rays is located in MEPhI and includes a water Cherenkov calorimeter (2000 m3) intended for the detection of basic components of cosmic rays at the Earth’s surface [2] and the coordinate-tracking detector DECOR [3] with large area (115 m2), and high spatial (1 cm) and angular (o11) resolution for investigations of spatialangular characteristics of the muon component of cosmic rays in a whole range of zenith angles. The results of the study of muon bundles in a wide range of zenith angles and muon multiplicities showed that this compact complex is able to provide information about the spectra of primary cosmic ray particles in the range of 1015–1019 eV [4]. Deployment of the shower array for detection of inclined EAS in the knee energy interval will significantly increase capabilities of the NEVOD–DECOR complex.
Fig. 2. Scintillation assembly of the shower detector.
4. Construction of the scintillation detector The shower detector is a scintillation assembly with a total area of 1 sqm2, with the octagonal shape divided into sectors (Fig. 2). The thickness of the plastic is 20 mm. The light is collected by wavelength shifter bars fixed between the sectors and is transmitted to the photomultiplier located in the center of the detector. The shifter technique allows using fast PMT with a smalldiameter photocathode (PM-115M) in order to provide a good time resolution. The scheme of light collection is shown in Fig. 3. The accuracy of time determination for a single muon crossing the detector is better than 3 ns. The radius of curvature of shifter bars is equal to 100 mm; this is a minimal possible radius, when losses of light do not exceed 20%. Scintillation light output and PMT noise depend on the temperature; therefore, a powerful system of temperature stabilization, which includes a thermo-insulating box, two thermosensors, a heater and a program of the heater control, is used in the detector. The thermo-insulating box is made of rigid polyfoam. Thickness of the walls of the box is 7 cm. The scintillation assembly, PMT and front-end electronics units (QDC, TDC, HV converter, etc.) are installed inside this box. We can set any level of stabilization by changing the thresholds for switching the heater on and off. A lower level of the heater control is located in the detector, and the controller (once per second) fixes the data of the thermosensors and compares them with preset values. If the temperature decreases below the minimal
Fig. 3. Light collection in the detector.
allowed value, the heater is switched on, while on reaching the upper boundary of the temperature range, it is switched off. The top level of the heater control is located in the central computer of the shower array, which permanently requests the data of thermosensors in order to check the correctness of actions of the controller. The accuracy of temperature stabilization is equal to 0.5 1C. The housing of the detector is made of 1 mm-zinced steel and provides protection against atmospheric influences (Fig. 4). The detector is fastened on a rotating frame, which allows one to change the orientation of the detector plane (horizontally–vertically), and to conduct measurements of the flux in different directions (Fig. 5). Compared with a traditional EAS array detector, in the given construction the thickness of plastic is reduced by a factor of 2.5; in the detector design, light and inexpensive synthetic materials are used. This allows one to considerably reduce the weight and cost of the detector. A full mass of the detector is about 70 kg;
ARTICLE IN PRESS 298
E.E. Yanson et al. / Nuclear Instruments and Methods in Physics Research A 598 (2009) 296–299
To select the shifter bars with identical output of light. The
same test facility and the same selection criteria (75%) are used. To reach the uniformity of the response for any coordinate of the scintillation plates.
Uniformity of the response of the plates was estimated by the comparison of average values of amplitude spectra for muons passing through limited areas of the detector selected by a counter telescope. Application of shaded masks on the light reflection material (tyvek sheets) allows one to achieve practically full equalization of signals. Relative amplitudes for various points of the plate and the shaded mask are shown in Fig. 6. Without a mask, the amplitude in the near-PMT zone is 1.5 times higher than on the edge. Mapping of the shaded masks is performed by means of the large-format ink printer under control of the program with a preset table of blacking. Fig. 4. EAS scintillation detector.
Fig. 5. Vertical and horizontal positions of the detector.
6. Electronics The central electronics of the shower array operates the central trigger logic and CAN, carries out the fast analysis and storage of the data. It can serve from 1 up to 48 detectors. The logic of coincidences is realized on the ISA-compatible plate and based on the ALTERA microcircuit. The program interface of the trigger plate allows one to set any level of coincidences of detectors in the array. There is a possibility of monitoring the noise of the detectors and the time differences of the received trigger signals. Operation system of the triggering computer is FreeDOS. The main program operates all controllers depending on the mode set (registration, monitoring, and calibration). In the main computer, the ISA-compatible CAN adapter is installed, which can operate 8–10 detectors, at a frequency of events up to 200 Hz. In one computer, up to 6 such adapters can be included. Front-end electronics of the detector provides the possibility of working in several operating modes (registration, monitoring, and calibration) and consists of the following:
Detector controller (8051 microcontroller), which provides the traffic of the data from the measuring part of the detector to the central machine and receives from it the control data (to vary the reference voltages of threshold schemes and of
Fig. 6. Relative response and the shaded mask used in the detector.
therefore the deployment of the array on the roofs of the buildings is possible.
5. Uniformity of the detector response To provide a good energy resolution of the scintillation counter, the following were necessary:
To reduce a loss of the light from plastic and shifters. We
applied ‘‘tyvek’’ as the reflecting material, which covers the top and bottom sides of each scintillation plate of the assembly. To select scintillation plates with a similar light output. The response for all plates is measured with a specialized test facility, and the plates that are different not more than by 5% from the average are used in each detector.
Fig. 7. The spectrum of signals for single vertical muons (A ¼ 164; A–Ped ¼ 58; FWHM ¼ 32).
ARTICLE IN PRESS E.E. Yanson et al. / Nuclear Instruments and Methods in Physics Research A 598 (2009) 296–299
high voltage converter). A required range of the temperature is maintained by the controller automatically. Measuring part (PMT, QDC, TDC). The use of two 12-bit QDC (for two dynodes) allows one to provide a dynamic range of measured signals from 1 to 104 particles in the detector; 12-bit TDC ensures 1 ns accuracy of time measurements. LED-based calibration system. In the inner calibration system of the detector, two blue LEDs and a flasher controller, which allows regulating independently the control voltage in the range from 0 up to 10 V with a good accuracy, are used. Common start signal initiates a flash of LED and QDC strobe. Cross-talks between the controller channels are negligibly small, which allows one to perform the linearity test of PMT. Cocraft-type high-voltage converter with preamplifiers. The voltage is regulated in the range from 500 to 2000 V with a 7 V step. Adjustment may be implemented any time by the control program of the central computer. First-level trigger logic. The array detector is considered to have worked if the anode signal of PMT exceeds the threshold (of about 0.3 MIP). Communication system is based on the CAN-open standard and is used to receive and send service data and data from the measuring part. Two coaxial cables are used to transmit trigger logical signals REQUEST and ANSWER. As a power supply, 220 V AC is used in each detector.
299
(2000 ns) the answer appears, the timer stops (STOP_TDC), and the signals are digitized. Digital data of QDC1, QDC2 and TDC are recorded in FIFO. The digitization of signals and recording them in the memory requires 10 ms; during this time period the detector is busy.
7. Response of the detector In Fig. 7, the spectrum of signals from the detector for single vertical muons selected with a telescope is shown. The average signal corresponds to about 30 photoelectrons (channel 168). Response of the detector for a single muon is characterized by FWHM/(A-Ped) ¼ 0.55. Though the light yield of the used scintillator is less than, f.e., of Bicron 404A plastic, the detector parameters are still acceptable. The available amount of the plastic of this type is sufficient for the construction of a full-scale shower array.
Acknowledgement This work was carried out with the support of the Russian Foundation for Basic Research (Grant no. 07-02-13650-ofi-ts). References
In the registering part of the detector, an asynchronous process of event data acquisition and storage is realized. For temporary storage of the data, a FIFO-type memory with a capacity of 128 events is used. In case the first-level trigger appears, the timer is started (START_TDC), signals of 12th and 9th dynodes are memorized and signal REQUEST is sent. If during a waiting time
[1] S.P. Denisov, et al., in: Proceedings of the 29th ICRC, Pune, India, vol. 8, 2005, p. 267. [2] V.M. Aynutdinov, et al., Astrophys. Space Sci. 258 (1998) 105. [3] M.B. Amelchakov, et al., in: Proceedings of the 27th ICRC, Hamburg, Germany, vol. 3, 2001, p. 1267. [4] I.I. Yashin, et al., in: Proceedings of the 29th ICRC, Pune, India, vol. 6, 2005, p. 373.
Contents lists available at ScienceDirect
Nuclear Instruments and Methods in Physics Research A journal homepage: www.elsevier.com/locate/nima
Multi-sector scintillation detector for investigations of extensive air showers E.E. Yanson a,, S.P. Denisov b, Yu.V. Gilitsky b, V.V. Kindin a, R.P. Kokoulin a, K.G. Kompaniets a, V.V. Lipaev b, A.A. Matyushin b, A.V. Ovchinnikov a, A.A. Petrukhin a, N.N. Prokopenko b, M.M. Soldatov b, A.N. Sytin b a b
Moscow Engineering Physics Institute (State University), Moscow 115409, Russian Federation Institute for High Energy Physics, Protvino 142284, Russian Federation
a r t i c l e in f o
a b s t r a c t
Available online 19 August 2008
A new type of scintillation detector for shower arrays is considered. The detector represents an octagonal scintillation assembly with total area 1 m2 divided into sectors. Thickness of the plastic is 20 mm. The light is collected by wavelength shifter bars to the photomultiplier, which is located in the center of the detector. A solution to ensure the uniformity of light collection for any coordinate is proposed. Front-end electronics of the detector consists of the controller, the measuring part (QDC, TDC), the system of calibration and the HV converter. The data acquisition system is based on CAN-open standard. There is also a system of temperature stabilization that guarantees not more than 0.51 deviation of the temperature of measuring part elements. Measuring electronics allows obtaining the dynamic range from 1 up to 104 particles and 1 ns time digitization. The time resolution of the detector is about 3 ns. & 2008 Elsevier B.V. All rights reserved.
Keywords: Scintillation detector Shower array Uniformity of the response
1. Introduction Investigations of extensive air showers (EAS) give information about primary cosmic-ray flux and some characteristics of hadron interactions (cross-section, multiplicity, etc.) at energies that are not accessible currently and cannot be reached in nearest accelerator experiments (more than 14 TeV in the center of mass system). Usually EAS at small zenith angles (near-vertical direction) are investigated by using distributed systems of standard scintillation counters with thicknesses of 5 cm. Investigations of inclined EAS are more complicated taking into account the following circumstances. Firstly, the flux of inclined showers with the same particle number is less than in the vertical direction, and decreases with the increase of zenith angle. Secondly, the ratio between the muon number and the electron number increases while the total number of particles decreases. Thirdly, traditional (horizontal) orientation of scintillation detectors does not allow one to correctly measure the number of shower particles in inclined EAS. At the same time, investigations of inclined showers allow one to obtain new information about EAS development and to explore higher energies of primary particles. For conduction of such type of experiments, two main conditions are required: the presence of the central detector, which allows evaluating the energy of muons
Corresponding author. Tel.: +7495 323 9040; fax: +7 495 324 8780.
E-mail address: [email protected] (E.E. Yanson). 0168-9002/$ - see front matter & 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2008.08.026
in inclined showers, and a shower array of scintillation detectors, which can change orientation from horizontal to vertical. Suitable central detectors for this purpose exist in IHEP, Protvino (liquid-argon spectrometer BARS) and in Moscow Engineering Physics Institute (MEPhI), Moscow (Cherenkov water detector NEVOD). Firstly, the project of BARS-EAS was developed and then another project NEVOD-EAS appeared.
2. EAS-BARS project The EAS-BARS experiment (MEPhI, IHEP, INR) is aimed at measurements of various EAS component characteristics in the ‘‘knee’’ region (1015–1017 eV). Shower array includes 48 detectors deployed over the area of 220 m 60 m around liquid-argon ionization calorimeter BARS (18 m length and 3 m in diameter) located at the neutrino channel of the IHEP accelerator (Protvino). Arrangement of detectors of the electron–photon component and of the BARS spectrometer is shown in Fig. 1. Large area of registration (450 m2), a high spatial resolution (6 cm), the ability to register separate particles and cascades, an opportunity to trace their development in depth (thickness of the detector ranges from 500 up to 3000 g/cm2) and low threshold calorimetry allow the use of the spectrometer BARS for the solution of problems of cosmic ray physics [1]. Event registration by the combined setup (spectrometer BARS+shower array) is triggered by the signal from a scheme of coincidences of shower detectors. The setup can detect not only near-vertical EAS (up to 401) but also inclined EAS, which gives a possibility of
ARTICLE IN PRESS E.E. Yanson et al. / Nuclear Instruments and Methods in Physics Research A 598 (2009) 296–299
297
Fig. 1. Shower array and BARS spectrometer.
investigating transition from usual electron–photon showers to pure muon showers.
3. NEVOD-EAS project The NEVOD-EAS setup will be deployed in the MEPhI campus. The total area of the shower array is about 3 104 m2, which is determined by the intensity of cosmic rays at the knee energies. Experimental complex NEVOD for studies of new physical processes around the knee of the energy spectrum of cosmic rays is located in MEPhI and includes a water Cherenkov calorimeter (2000 m3) intended for the detection of basic components of cosmic rays at the Earth’s surface [2] and the coordinate-tracking detector DECOR [3] with large area (115 m2), and high spatial (1 cm) and angular (o11) resolution for investigations of spatialangular characteristics of the muon component of cosmic rays in a whole range of zenith angles. The results of the study of muon bundles in a wide range of zenith angles and muon multiplicities showed that this compact complex is able to provide information about the spectra of primary cosmic ray particles in the range of 1015–1019 eV [4]. Deployment of the shower array for detection of inclined EAS in the knee energy interval will significantly increase capabilities of the NEVOD–DECOR complex.
Fig. 2. Scintillation assembly of the shower detector.
4. Construction of the scintillation detector The shower detector is a scintillation assembly with a total area of 1 sqm2, with the octagonal shape divided into sectors (Fig. 2). The thickness of the plastic is 20 mm. The light is collected by wavelength shifter bars fixed between the sectors and is transmitted to the photomultiplier located in the center of the detector. The shifter technique allows using fast PMT with a smalldiameter photocathode (PM-115M) in order to provide a good time resolution. The scheme of light collection is shown in Fig. 3. The accuracy of time determination for a single muon crossing the detector is better than 3 ns. The radius of curvature of shifter bars is equal to 100 mm; this is a minimal possible radius, when losses of light do not exceed 20%. Scintillation light output and PMT noise depend on the temperature; therefore, a powerful system of temperature stabilization, which includes a thermo-insulating box, two thermosensors, a heater and a program of the heater control, is used in the detector. The thermo-insulating box is made of rigid polyfoam. Thickness of the walls of the box is 7 cm. The scintillation assembly, PMT and front-end electronics units (QDC, TDC, HV converter, etc.) are installed inside this box. We can set any level of stabilization by changing the thresholds for switching the heater on and off. A lower level of the heater control is located in the detector, and the controller (once per second) fixes the data of the thermosensors and compares them with preset values. If the temperature decreases below the minimal
Fig. 3. Light collection in the detector.
allowed value, the heater is switched on, while on reaching the upper boundary of the temperature range, it is switched off. The top level of the heater control is located in the central computer of the shower array, which permanently requests the data of thermosensors in order to check the correctness of actions of the controller. The accuracy of temperature stabilization is equal to 0.5 1C. The housing of the detector is made of 1 mm-zinced steel and provides protection against atmospheric influences (Fig. 4). The detector is fastened on a rotating frame, which allows one to change the orientation of the detector plane (horizontally–vertically), and to conduct measurements of the flux in different directions (Fig. 5). Compared with a traditional EAS array detector, in the given construction the thickness of plastic is reduced by a factor of 2.5; in the detector design, light and inexpensive synthetic materials are used. This allows one to considerably reduce the weight and cost of the detector. A full mass of the detector is about 70 kg;
ARTICLE IN PRESS 298
E.E. Yanson et al. / Nuclear Instruments and Methods in Physics Research A 598 (2009) 296–299
To select the shifter bars with identical output of light. The
same test facility and the same selection criteria (75%) are used. To reach the uniformity of the response for any coordinate of the scintillation plates.
Uniformity of the response of the plates was estimated by the comparison of average values of amplitude spectra for muons passing through limited areas of the detector selected by a counter telescope. Application of shaded masks on the light reflection material (tyvek sheets) allows one to achieve practically full equalization of signals. Relative amplitudes for various points of the plate and the shaded mask are shown in Fig. 6. Without a mask, the amplitude in the near-PMT zone is 1.5 times higher than on the edge. Mapping of the shaded masks is performed by means of the large-format ink printer under control of the program with a preset table of blacking. Fig. 4. EAS scintillation detector.
Fig. 5. Vertical and horizontal positions of the detector.
6. Electronics The central electronics of the shower array operates the central trigger logic and CAN, carries out the fast analysis and storage of the data. It can serve from 1 up to 48 detectors. The logic of coincidences is realized on the ISA-compatible plate and based on the ALTERA microcircuit. The program interface of the trigger plate allows one to set any level of coincidences of detectors in the array. There is a possibility of monitoring the noise of the detectors and the time differences of the received trigger signals. Operation system of the triggering computer is FreeDOS. The main program operates all controllers depending on the mode set (registration, monitoring, and calibration). In the main computer, the ISA-compatible CAN adapter is installed, which can operate 8–10 detectors, at a frequency of events up to 200 Hz. In one computer, up to 6 such adapters can be included. Front-end electronics of the detector provides the possibility of working in several operating modes (registration, monitoring, and calibration) and consists of the following:
Detector controller (8051 microcontroller), which provides the traffic of the data from the measuring part of the detector to the central machine and receives from it the control data (to vary the reference voltages of threshold schemes and of
Fig. 6. Relative response and the shaded mask used in the detector.
therefore the deployment of the array on the roofs of the buildings is possible.
5. Uniformity of the detector response To provide a good energy resolution of the scintillation counter, the following were necessary:
To reduce a loss of the light from plastic and shifters. We
applied ‘‘tyvek’’ as the reflecting material, which covers the top and bottom sides of each scintillation plate of the assembly. To select scintillation plates with a similar light output. The response for all plates is measured with a specialized test facility, and the plates that are different not more than by 5% from the average are used in each detector.
Fig. 7. The spectrum of signals for single vertical muons (A ¼ 164; A–Ped ¼ 58; FWHM ¼ 32).
ARTICLE IN PRESS E.E. Yanson et al. / Nuclear Instruments and Methods in Physics Research A 598 (2009) 296–299
high voltage converter). A required range of the temperature is maintained by the controller automatically. Measuring part (PMT, QDC, TDC). The use of two 12-bit QDC (for two dynodes) allows one to provide a dynamic range of measured signals from 1 to 104 particles in the detector; 12-bit TDC ensures 1 ns accuracy of time measurements. LED-based calibration system. In the inner calibration system of the detector, two blue LEDs and a flasher controller, which allows regulating independently the control voltage in the range from 0 up to 10 V with a good accuracy, are used. Common start signal initiates a flash of LED and QDC strobe. Cross-talks between the controller channels are negligibly small, which allows one to perform the linearity test of PMT. Cocraft-type high-voltage converter with preamplifiers. The voltage is regulated in the range from 500 to 2000 V with a 7 V step. Adjustment may be implemented any time by the control program of the central computer. First-level trigger logic. The array detector is considered to have worked if the anode signal of PMT exceeds the threshold (of about 0.3 MIP). Communication system is based on the CAN-open standard and is used to receive and send service data and data from the measuring part. Two coaxial cables are used to transmit trigger logical signals REQUEST and ANSWER. As a power supply, 220 V AC is used in each detector.
299
(2000 ns) the answer appears, the timer stops (STOP_TDC), and the signals are digitized. Digital data of QDC1, QDC2 and TDC are recorded in FIFO. The digitization of signals and recording them in the memory requires 10 ms; during this time period the detector is busy.
7. Response of the detector In Fig. 7, the spectrum of signals from the detector for single vertical muons selected with a telescope is shown. The average signal corresponds to about 30 photoelectrons (channel 168). Response of the detector for a single muon is characterized by FWHM/(A-Ped) ¼ 0.55. Though the light yield of the used scintillator is less than, f.e., of Bicron 404A plastic, the detector parameters are still acceptable. The available amount of the plastic of this type is sufficient for the construction of a full-scale shower array.
Acknowledgement This work was carried out with the support of the Russian Foundation for Basic Research (Grant no. 07-02-13650-ofi-ts). References
In the registering part of the detector, an asynchronous process of event data acquisition and storage is realized. For temporary storage of the data, a FIFO-type memory with a capacity of 128 events is used. In case the first-level trigger appears, the timer is started (START_TDC), signals of 12th and 9th dynodes are memorized and signal REQUEST is sent. If during a waiting time
[1] S.P. Denisov, et al., in: Proceedings of the 29th ICRC, Pune, India, vol. 8, 2005, p. 267. [2] V.M. Aynutdinov, et al., Astrophys. Space Sci. 258 (1998) 105. [3] M.B. Amelchakov, et al., in: Proceedings of the 27th ICRC, Hamburg, Germany, vol. 3, 2001, p. 1267. [4] I.I. Yashin, et al., in: Proceedings of the 29th ICRC, Pune, India, vol. 6, 2005, p. 373.