Study of a 38 mm x 38 mm fluorine-based plastic scintillator
19
for fast neutron detection by means of F activation
1)
1,2)
1)
1)
1)
Pawel Sibczynski , Jan Kownacki , Marek Moszynski , Agnieszka Syntfeld-Kazuch , Michal Gierlik ,
3)
3)
3)
3)
4)
5)
Matthieu Hamel , Frederick Carrel , Eva Montbarbon , Amelie Grabowski , Paul Schotanus , Alessandro Iovene ,
5)
Carlo Tintori
1)
National Centre for Nuclear Research (NCBJ), 05-400 Otwock-Swierk, Poland
2)
Heavy Ion Laboratory (HIL), 02-093 Warsaw, Poland
3)
CEA, LIST, Laboratoire Capteurs et Architectures Électroniques, F-91191 Gif-sur-Yvette, France.
4)
Scionix Holland, Bunnik, The Netherlands
5)
CAEN S.p.A., Via Vetraia 11, 55049 - Viareggio (LU) - Italy
IEEE NSS/MIC Conference 2015, San Diego, California, USA
e-mail: [email protected]
Introduction
Pulse shape discrimination (PSD)
We present the performance of novel pentafluorostyrene-based plastic
scintillator. The first prepared sample with size of dia. 32 × 4 mm3
was introduced in [1]. Motivation of the research is to find an alternative to hexafluorobenzene-based liquid scintillators, which are toxic and
flammable. The Fluorine-based scintillators were proposed for prompt
photofission neutron detection by means of Threshold Activation Detection [2]. The method relies on activation of specific types of nuclei (such
as 19F), with appropriate reaction threshold (greater than 2.5 MeV), considerable cross section and half-life in the range of seconds. These nuclei,
after activation, can decay into successors, which emit high-energy β − particles, even with the energy endpoint at 10.4 MeV. In the case of the 19F,
such reactions can occur:
The pulse shape discrimination was measured with use of a CAEN DT5720
digitizer with implemented DPP-PSD firmware for pulse charge integration.
The scintillators were exposed to neutrons from a 252Cf source. The 2D
plots are presented below.
n + 19F → 16N + α
n + 19F → 19O + p
The 16N decays within the half-life of 7.1 s, emitting β − particles with energy endpoint at 10.4 MeV or 6.1 MeV γ-rays in coincidence with the β −
particles with maximum energy of 4.3 MeV.
General description of the scintillator
The F-plastic scintillator is based on pentafluorostyrene (C8F5H3) and
two wavelength-shifting dyes.
The first sample, size of 32 × 4 mm was developed and tested, results
were published in [1].
The scintillator is exceptionally heavy, with density of 1.56 g/cm3.
Possible application in prompt photofission neutrons detection by
activation of 19F, proposed in [2] and investigated further in [3] and [4].
Figure: PSD histograms of the dia. 32 × 4 mm3 F-plastic scintillator (left) and dia. 38 ×
38 mm3 F-plastic (right).
In the case of the smaller F-plastic modest n/γ discrimination was observed, in contrast to the larger sample. This is due to its lower light output
and turbidity of the larger scintillator.
Exposition to 14 MeV neutrons
The scintillators were exposed to 14 MeV neutrons emitted from NSD
Gradel fusion-chamber type DT neutron generator. The fast neutrons
are registered by activation of 19F in the scintillator medium, resulting in
−
emission of β particles. The exposition lasted 300 s, then after 1 s of
cooling time the acquisition was running for 60 s. The net spectra for
2” × 2” EJ-313 and F-plastic show increased amount of counts in the energy region between 6.0 and 10.5 MeV comparing to the EJ-200.
5
C o u n ts
1 0
1 0
4
1 0
3
1 0
2
1 0
1
1 0
0
E J -3 1 3
E J -2 0 0
F -p la s tic
0
1
2
3
4
5
6
7
8
9
1 0
1 1
1 2
1 3
E n e rg y (M e V )
Figure: Photography of small and large F-plastic scintillators together with a PVT-based
2” × 2” EJ-200.
Acknowledgement
Photoelectron yield
The photoelectron yield of the investigated scintillators, measured by
means of single photoelectron method, is presented in Table below.
Scintillator
Size
PMT
F-plastic 32 × 4 mm
Photonis XP5212B
F-plastic 38 × 38 mm
Photonis XP5212B
EJ-313
2” × 2”
Hamamatsu R6233-100
EJ-200
2” × 2”
Photonis XP5212B
This scientific work was partly supported by:
C-BORD EU project no. 653323 in the frame of Horizon 2020 Program,
Nphe /MeV References
Grant for realization of scientific program by young scientists from
internal funds of NCBJ,
870 ± 50
320 ± 40
230 ± 20
2200 ± 110
POLONIUM 2015-2016 staff exchange Project between Polish and
French scientific laboratories,
[1]
[4]
-
One-month scientific stay in CEA LIST, Saclay, France, funded by French
Embassy in Poland and Campus France,
Table: Photoelectron yield of the tested scintillators.
Ram-ScaN Project no. PBS2/B2/11/2014 realized by NCBJ.
Summary and outlook
The first version of larger F-plastic scintillator was prepared, allowing for
registration of γ-rays and neutrons. Currently we are working on improvement of the scintillator uniformity and transparency in order to increase the
scintillator light output and reduce turbidity.
Pawel Sibczynski (National Centre for Nuclear Research, Poland)
Figure: Energy spectra obtained after exposition of the scintillators to neutrons from the
DT generator.
References
[1] M. Hamel, P. Sibczynski et al., NIM A 768 (2014) 26-31
[2] T. Gozani et al., NIM A 652 (2011) 334-337
[3] J. Stevenson et al., NIM A 652 (2011) 124-128
[4] P. Sibczynski et al., JINST (2015) 010T 0215
IEEE NSS/MIC 2015
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