Multi-sector scintillation detector for investigationsof Extensive Air Showers

E.E. YansonBARS-EAS CollaborationIHEP, Protvino, Russia

MEPhI, Moscow, RussiaEEYanson@mephi.ru

BARS-EAS

BARS

In standard technique of EAS registration, the distributed systems of detectors are used. Depending on a solved problem, the shower array is combined with the central detector. For collaboration BARS-EAS the central detector is liquid-argon spectrometer BARS located in IHEP, Protvino.

We tried to create simple and cheap detector.

Shower detector

• Scintillation assembly with area 1 sq. m.• Thickness of plastic is 20 mm. • Light is collected by means of wavelength

shifter bars. • Fast PMT with small diameter photocathode.• Front-end electronics (controller, QDC, TDC,

HV converter, thermosensors, etc.).• Total weight ~ 70 kg. Therefore deployment

of the array on the roofs of the buildings is possible.

Scheme of scintillation assembly• octagonal

shape • 8 sectors• 8 shifter bars

which are fixed between these sectors

• PMT is located in the centre of the detector

570

PMT

Scintillation assembly

Scintillation assemblyThe shifter technique allows to use PMT with small diameter photocathode.

The central location and use of fast PMT provide a good time resolution of our detector. Accuracy of time determination ~ 3 ns.

Shifter bars

Scheme of light collection

100 m m

P M1 1 5 м

Shifter turns light anddirects it exactlyto photocathode

PMT = 30 mm

Central part

• cocraft-type high voltage converter

• preampliphier for anode

• preampliphier for 8th dynode

• preampliphier for 12th dynode

System of temperature stabilization

The system of temperature stabilization must provide a constant temperature inside the detector.

• Thermo-insulating box of rigid polyfoam.• Two thermosensors.• Heater.• Bottom level programme of the heater control (located in

the detector).• Top level programme of the heater control (located in

central computer). This program permanently requests the data of the thermosensors for check correctness of actions of the controller.

Thermo-insulating box

• Rigid polyfoam

• Thickness of the walls is 7 cm

Top of the box, heater

The fan pumps the air through the heating element.

Thermotube for cold air.

Thermotube for hot air.

Temperature stabilization

1415

5 - 7 min

Detector housing

0.7 mm zinced steel

Communication cabie

This detector can work on distance up to 1 km from the central computer.

Communications

Front-end electronics of the detector

Outer electronics of the array

Communication cable

220 V

DAQ

Trigger

Powersupply

twisted pair (CAN)

request

answer

QDC

TDC

LED

HV

Thresh

EAS trigger

The array detector is considered has worked if the anode signal of PMT exceeds the threshold of 0.5 MIP. In this case, the timer is started and signal REQUEST is sent.

The ANSWER signal is initiated by the coincidences of signals shower detectors (then timer stops).

Front-end electronics Front-end electronics of the detector provides the possibility

to work in several operating modes (registration, monitoring, calibration).

It includes:• Controller (microcontroller 8051).• Measuring part. Using two 12-bit QDC (for two dynodes)

allow to provide dynamic range of measured signals from 1 to 104 particles in the detector. 12-bit TDC provides accuracy of time interval ~ 1 ns.

• System of calibration (LED based).• HV-converter.• First-level trigger logics • Communication system is based on CAN-open standard.

Front-end electronics

Outer electronics of the arrayAllows to operate up to 48 detectors

PC for trigger. FreeDOS

PC for DAQ. WinXP

Response of the detector To provide a good energy resolution, it was

necessary: • To reduce a loss of the light from plastic and

shifters. We applied "tyvek" which covers top and bottom sides of each scintillation plate;

• To select the scintillation plates with identical output of light;

• To get the uniformity of the response for any co-ordinate of the scintillation plates. Uniformity of the response was estimated by means of comparison of average values of amplitude spectra for muons passing through different areas of the detector.

Shaded masks

0.96

1.03 1.05 1.01

1.04 1.10 1.01

1.02 1.081.08

1.011.07

0.970.970.84 0.96 0.82

Without a mask, the amplitude in the near-PMT zone is 1.6 times higher than on the edge.

Mapping of shaded masks for sectors is done by means of the ink printer under control of the program with a pre-set table of blacking.

Single vertical muon

• Bicron 404A• 12.7 mm• ~ 50 ph.e.• A = 164• A – Ped = 58• FWHM = 32• FWHM

= 0.55A - Ped

Conclusion

• The multi-sector detector has a good time and amplitude resolution, low weight and low cost.

• Front-end electronics allows to obtain a dynamic range from 1 up to 10000 particles, 1 ns timer clock, and control the temperature inside the detector.

• In the control system, various modes of calibration and operation are foreseen.