1. Organic Scintillators for Neutrons
Alberto Quaranta
Laboratori Nazionali di Legnaro - INFN
University of Trento – Dept. Materials Engineering Ind. Technologies (DIMTI)

2. Scintillators for thermal neutrons
Scintillators for thermal neutrons are based on the detection of the reaction products between neutrons and few nucleus which can be dispersed in the scintillating matrix.

3. Scintillators for thermal neutrons
Liquid scintillators: high efficiency, pulse shape for n-g discrimination.
Toxic, corrosive, flammable, explosive...
Inorganic scintillators: high radiation hardness
Cryst. growth technology, pressed unhomogenous powders.
Plastic scintillators: different shapes and volumes
Low radiation resistance. New polymers have to be studied.

4. Needs of new scintillators for neutrons
Neutron counting and monitoring.
Complex geometries and high volumes.

5. State of art Commercial plastic scintillators. BC-454/EJ-245 (B).
14 €/g for B containing.
Carborane as boron disperser in PS
Volatile, not always soluble and 100 €/g.
Plastic and microcrystal mixed scintillators.
Unhomogeneous.
Gd and B containing silicone rubbers.
Studies are still at a preliminar stage (Oak-Ridge).

6. ORIONE – ORganic scIntillators for NEutrons
LNL – LNS
The aim of ORIONE experiment is develop rubber scintillators for the detection of thermal neutrons.
Selection of the luminescent silicone rubber matrix.
Selection of the luminescent dye molecule converting in light the excited states of the matrix.
Selection of a suitable organic compound containing the reactive nucleus.

7. Why silicone rubbers? Good radiation hardness.
Dimethyl-diphenyl-polysiloxane
Good radiation hardness.
Thermal stability (-55 up to 290 °C) and workability (easy to cut and to handle).
Fluorescence and refractive index can be tailored by varying the amount of diphenyl groups.
3-D cross linking can be attained to improve the radiation hardness.

8. M. Bowen et al. IEEE Trans. Nucl. Sci. 36 (1989) 562
Pre-irradiation
PS irradiated in air
600 Ci 60Co source
Transmittance
After 3 Mrads
Pre-irradiation
SR irradiated in air
600 Ci 60Co source
Transmittance
After 18 Mrads
M. Bowen et al. IEEE Trans. Nucl. Sci. 36 (1989) 562

9. Good solubility in the polymer matrix. Good radiation hardness.
Suited dye molecules
Overlap between dye absorption spectrum and polymer fluorescence spectrum.
Good solubility in the polymer matrix.
Good radiation hardness.
2,5 diphenyloxazole - PPO

10. Preliminary tests
Photoluminescence and radioluminescence measurements on silicone rubber doped with only PPO show the dye emission band as the main luminescence feature.

11. Preliminary tests
Pulse height spectra show a higher light yield of silicone doped scintillator (1% PPO) with respect to NE102 under excitation with a particles.

12. 2009 planned activity
New organic compounds for dispersing Gd and B in the silicone polymer.
Gadolinium and Boron compounds requirements
Highly soluble in the siloxane fluids.
Inert to the cross-linking reaction and to the light yield.
Thermally resistant (up to 100°C, final annealing for the cross-linking completion).

13. a and g radiation sources and ion beams at LNL and LNS.
2009 planned activity
Test on the radiation hardness of the silicone scintillators (crosslinking as an improvement).
Scintillation degradation during ion irradiation. Formation of color centers after exposure to the “Gamma Knife” 60Co source at LNS (3 Gy/min).
Test on the effect of the compounds on the scintillation yield and pulse shape.
a and g radiation sources and ion beams at LNL and LNS.

14. First scintillation tests with neutrons.
2009 planned activity
First scintillation tests with neutrons.
LNS neutron converter
Graphite cylinder + lead shield for gamma background + PEHD for moderating the neutrons.
After the preparation of the neutron converter the first n detection tests will be performed at LNS.

15. Planned activity
2010
Full characterization for n detection capabilities of the produced scintillators.
Pulse shape and height analyses for studying the capabilitiels for n-g discrimination.

16. Staff Nat. Resp. Alberto Quaranta LNL Resp. Sara Carturan
Fabiana Gramegna
Vladimir Kravchuk
Gianantonio Della Mea
Michele Tonezzer
Gabrio Valotto
Sandro Sassi
Mauro Masiol
LNS Resp. Maurizio Re
Giacomo Cuttone
Gianluigi Cosentino
Alfio Pappalardo

17. Thank you for your attention