1. Vladimir Rykalin NRC KI IHEP Baksan - 50, Nalchik, 06 - 08 June, 2017.
Characteristics of large - size scintillating detectors on the basis of polystyrene and scintillating polystyrene granules
Vladimir Rykalin
NRC KI IHEP
Baksan - 50, Nalchik,
June, 2017.

2. Outline • Scintillators produced by the known technologies:
polymerization, molding under pressure, extrusion,
detectors.
polystyrene granules in mirror forms, characteristics of
• New technology - melting of powdered
Scintillating bars and strips.
Scintillators with large sizes and thickness.
• New technology - scintillators on the basis of scintillating granules, detectors.

3. NRC KI IHEP Polystyrene scintillator FACILITY
Producing of scintillators at IHEP was began around 30 years ago. In an initial production stage the polymerized scintillators (polymerization of big blocks, machining) was mastered. Then the technology of extruding of bars and strips from length to 5 meters from big blocks of the scintillator was developed. High transparency of scintillators (2m at 10×200mm2 cross section) allowed to use them in experiments at IHEP and CERN (DELFI, NA-12, DIRAC).
Just in 2000 the industrial extruder for production of scintillating bars and strips (WLS light collection) started working.

4. Scintillators produced by molding under pressure, detectors
Production of IHEP diecasting machines (scintillating plates and short bars) is the most demanded now. A number of the detectors on the basis of such plates are used in experiments at accelerators (electromagnetic and hadron calorimeters, guard systems) and for registration of cosmic particles (scintillating counters of the big sizes).

5. Scintillators produced by molding under pressure, detectors
Scintillating element of EM calorimeter
(Shashlyk type) with WLS light collection. At IHEP it was designed the optimal configuration of that сalorimeters then they started being used widely.
Scintillating element of large sizes counters with WLS light collection. Total number counters with square more 1×1 m2 delivered in different Laboratories is around ,5 ton elements was used in guard systems. Typical
photoelectron number Nph.e. for assembly of two plate (10mm thickness) is 40 ph.e./MeV.

6. The Main characteristics of plastic scintillators
Type of
scintillator
Production
power,
kg/hour
Max. sizes, cm
Attanuation length, cm
Lihgth
Output,
ph.e./MeV
Cost,
$/kg
Length
Width
Thickness
Polymerization 1
300±0,01
50±0,01
400
100
 Molding under pressure
 50
 50±0,01
 10±0,03
 40
50 
30 
 Extrusion
 100
 1000
 50±0,05
 10±0,05
40   

7. Products of the NEW Technology – the melting of POWDERED polystyrene granules in metal mirror forms
The construction of the mirror forms is very simple – a box with walls from mirror stainless. Around 1300 scintillating bars of 15×100×2000mm3 and 10×60×2600mm3 were delivered in European universities. At a use of 4 WLS Y-11 fibers of Ø 1mm and a photomultiplier Nph.e from MIP at the scintillator far ends was 10 and 13 respectively.
More 1000 scintillating plates of 50×500×500mm3 were delivered in Baksan neutrino observatory. Light output at length of light propagation 5 cm makes 90% from output of polystyrene polymerized scintillators, but the cost – in 3 times less. Just now it is possible to produce scintillating plates of 50×1000×1000mm3.

8. THE MELTING OF POWDERED POLYSTYRENE GRANULES IN METAL MIRROR FORMS
Relative light output of ~1100 pcs of 5 cm
scintillation plates supplied to Baksan Observatory.
Green dash line – Kharkov ordinary PS scintillator.
The main parts of scintillating counter of 30×300×1500mm3
on the base of PMT FEU-KC with photocathode of 15×200mm2.To increase uniformity of light collection a соncentration of the scintillating adds was changed from center of the counter to its ends in a process of the melting. Nph.e. from MIP at ends of the scintillator was around 30.

9. THE MELTING OF POWDERED POLYSTYRENE GRANULES IN METAL MIRROR FORMS
Photo of the 20 ×500 × 500 mm3 counter on the base of WLS fibers and SiPM (left) and the sketches of 1 mm Y11 WLS fibers (green) placed inside the grooves (1.52 mm2) in the scintillator of this counter (right). Nph.e. from MIP on all square of the counters is more 30.
Максимальные размеры сцинтилляторов составляют до 50×200×2600 мм3 для полос и 60×1000×1000 мм3 для пластин. Сцинтилляторы изготовляются на основе гранулированного полистирола по новой, запатентованной, технологии, обеспечивающей их существенно меньшую стоимость по сравнению с полимеризованными сцинтилляторами.
Светосбирание может осуществляться с помощью WLS волокон, в качестве фотоприёмников используются кремниевые фотоумножители, работающие в режиме Гейгеровского разряда, или обычные фотоумножители. В случае использованиия кремниевых фотоумножителей при регистрации MIP по всей поверхности счётчика с размерами, например, 50×500×500 мм3 обеспечивается количество фотоэлектронов не менее 40.

10. THE MELTING OF POWDERED POLYSTYRENE GRANULES IN METAL MIRROR FORMS
Photo of the 10×60×2000 mm3 counter (upper) and sketches of 1 mm Y11 WLS fibers placed inside the grooves (1.52 mm2) in the scintillator of this counter (lower). Nph.e. from MIP on all square of the counters is more 30.

11. THE MELTING OF POWDERED POLYSTYRENE GRANULES IN METAL MIRROR FORMS
Cosmic ray amplitude spectrum with external trigger: distance from SiPM is 150 сm, Nph.e. from MIP is 45; signal attenuation along the strip (max/min) not exceeding 30%
Decay muon amplitude spectrum obtained at U-70 setup OKA kaon beam.

12. Muon Detector at OKA Experimental Set-up
THE MELTING OF POWDERED POLYSTYRENE GRANULES IN METAL MIRROR FORMS
Muon Detector at OKA Experimental Set-up
The hodoscope of 2×2,5 m2 consisting of 47 scintillating strips with sizes of 10×60×2000 mm3

13. Scintillating polystyrene granules – the substance
for large and extra large scintillating detectors
The first mention about scintillating granules Yu.A.Tsirlin et al., Zhurnal Prikladnoi Spectroskopii (Soviet Journal of Applied Spectroscopy), Vol.6, No.1, pp 85-89, 1967.
Typical sizes of scintillating granules are Ø3×3 mm3

14. Scintillating polystyrene granules – the substance
G.Bitsadze and V.I.Rykalin, Particle Detectors Based on Scintillating Granules
08/18/16
Scintillating polystyrene granules – the substance
for large and extra large detectors
The scheme of the first scintillating counter on the basis of polystyrene scintillating granules and WLS fibers readout, air immersion media inside granules volume.
IHEP, Protvino

15. Scintillating polystyrene granules – the substance
G.Bitsadze and V.I.Rykalin, Particle Detectors Based on Scintillating Granules
08/18/16
Scintillating polystyrene granules – the substance
for large and extra large detectors
Amplitude spectrums of scintillating counters from MIP: the counter consisting of 200x200x20 mm3 volume of scintillating granules and a layer of WLS fiber placed at middle of granule layer thickness. Gaps between WLS fibers are 10 mm, Nph.e. from MIP is 25.5 (left); the counter consisting of 200x200x10 mm3 polystyrene scintillating plate with fish tail light guide Nph.e.= 19,5 (right). 15
IHEP, Protvino

16. Scintillating polystyrene granules – the substance
for large and extra large detectors
Scintillating granules exited by charged particles emit the scintillating radiation that is absorbed by two WLS fibers and transported to the silicon photomultiplier with sensitive square of 2,52,5 mm2. Thanks to the large attenuation length of the WLS fibers (up to 5 m) the dimensions of the scintillation counters on the basis of such scintillators can reach several meters. Manufacturing of counters of any shape does not require extrusion processing or injection molding. For the counter with the size of the working area of 500×500×50 mm3, the number of photoelectrons from MIP is not less than 50, for the size of the working area 1000×1000×50 mm3 – at least 40.

17. Scintillating polystyrene granules – the substance
for large and extra large detectors
Amplitude spectrum of the scintillating counter (slide 16) from MIP.

18. Scintillating polystyrene granules – the medium
for large and extra large detectors
Amplitude spectrum
of the lower part of the double (two floor) counter of 500×500×25mm3 received with outside trigger, Nph.e=32 from MIP.
Amplitude spectrum of this part of the counter received with self triggering.
Amplitude spectrum of this part of the counter received with the trigger from the counter of the upper part.
Amplitude spectrum of the counter on basis of Bicron 408
1000×250×25mm3 scintillator and two
two-inch PM counter received with self triggering.

19. Scintillating polystyrene granules – the medium
for large and extra large detectors
Scintillating counter of 2000×250×150 mm3 on the basis of scintillating granules, WLS Y11 Ø 1 mm and russian PM 184. Light output is around 50 ph.e./MeV.

20. Scintillating polystyrene granules – the medium
for large and extra large detectors
Advantages of scintillating granules as a material for scintillation counters.
Possible very big production power of scintillating granules - one industrial
plant for manufacturing polystyrene granules can produce around 100 Thousand tons of scintillation granules per year. This can be useful for mega projects.
2. Scintillating granules are currently the cheapest type of plastic scintillators. Further significant reduction in the cost of detectors based on the scintillating granules can be achieved by reducing the cost of WLS fibers, which in some cases make up about half the cost of the detector. Down with the monopoly of Kuraray and Bicron!
3. Possibility to create homogeneous scintillators of any forms and sizes without any empty gaps.
4. The presence of commercial granules will allow the production of scintillating counters of any shape and size by small groups of experimenters.

21. The Main characteristics of plastic scintillators
Type of
scintillator
Production
power,
kg/hour
Max. sizes, cm
Attanuation length, m
Lihgth
Output,
ph.e./MeV
Cost,
$/kg
Length
Width
Thickness
Polymeryzation 1
300±0,01
50±0,01 4
100
 Molding under pressure
 20
 50±0,01
 10±0,03
 0,4
50 
30 
 Extrusion
 100
 1000
 50±0,03
 10±0,05
0,4 
 50 20
Melting in metal mirror forms
 15
 300±0,01
 100±01
70±01
 0,5
Scintillating polystyrene granules 
100 -  104
(104 for
Industrial
production)
a few m. 
 a few m.
 around 4
(as for WLS
fiber)
 less 15
(for industrial

22. CONCLUSION – OUR PLANS
The increasing of light attenuation of extruded, and melted scintillators for the purpose of replacement too expensive polymerized polystyrene scintillators.
The optimization of scintillating granules characteristics and detectors on the basis of granules.
The producing and study of the characteristics of polystyrene scintillation granules with a metal core.
The study of the radiation hardness of
scintillating polystyrene granules.