OSA's Digital Library

Optics Express

Optics Express

  • Editor: Andrew M. Weiner
  • Vol. 21, Iss. 12 — Jun. 17, 2013
  • pp: 14573–14582
« Show journal navigation

Feasibility of fiber-optic radiation sensor using Cerenkov effect for detecting thermal neutrons

Kyoung Won Jang, Takahiro Yagi, Cheol Ho Pyeon, Wook Jae Yoo, Sang Hun Shin, Tsuyoshi Misawa, and Bongsoo Lee  »View Author Affiliations


Optics Express, Vol. 21, Issue 12, pp. 14573-14582 (2013)
http://dx.doi.org/10.1364/OE.21.014573


View Full Text Article

Acrobat PDF (1303 KB)





Browse Journals / Lookup Meetings

Browse by Journal and Year


   


Lookup Conference Papers

Close Browse Journals / Lookup Meetings

Article Tools

Share
Citations

Abstract

In this research, we propose a novel method for detecting thermal neutrons with a fiber-optic radiation sensor using the Cerenkov effect. We fabricate a fiber-optic radiation sensor that detects thermal neutrons with a Gd-foil, a rutile crystal, and a plastic optical fiber. The relationship between the fluxes of electrons inducing Cerenkov radiation in the sensor probe of the fiber-optic radiation sensor and thermal neutron fluxes is determined using the Monte Carlo N-particle transport code simulations. To evaluate the fiber-optic radiation sensor, the Cerenkov radiation generated in the fiber-optic radiation sensor by irradiation of pure thermal neutron beams is measured according to the depths of polyethylene.

© 2013 OSA

1. Introduction

During the past several decades fiber-optic radiation sensors (FORSs) have been developed to detect neutron fluxes in nuclear facilities [1

1. T. K. McKnight, J. B. Czirr, K. Littrell, and B. J. Campbell, “The flexible embedded-fiber neutron detector,” Nucl. Instrum. Meth. A 586(2), 246–250 (2008). [CrossRef]

3

3. E. Takada, T. Iguchi, H. Takahashi, M. Nakazawa, M. Sasao, M. Osakabe, and Y. Ikeda, “Distributed sensing of fusion neutrons by plastic scintillating fibers,” Fusion Eng. Des. 34-35, 591–594 (1997). [CrossRef]

]. FORSs offer many advantages for applications in the hazardous environments of nuclear facilities. Their most favorable capability is remote sensing without significant diminution of the signal. In this process, optical fibers are relatively immune to environmental influences, including pressure, temperature, humidity, and electromagnetic fields [4

4. A. F. Fernandez, B. Brichard, S. O’Keeffe, C. Fitzpatrick, E. Lewis, J.-R. Vaille, L. Dusseau, D. A. Jackson, F. Ravotti, M. Glaser, and H. El-Rabii, “Real-time fiber optic radiation dosimeters for nuclear environment monitoring around thermonuclear reactors,” Fusion Eng. Des. 83(1), 50–59 (2008). [CrossRef]

9

9. B. Lee, K. W. Jang, D. H. Cho, W. J. Yoo, S. H. Shin, H. S. Kim, J. H. Yi, S. Kim, H. Cho, B. G. Park, J. H. Moon, and S. Kim, “Measurement of two-dimensional photon beam distributions using a fiber-optic radiation sensor for small field radiation therapy,” IEEE Trans. Nucl. Sci. 55(5), 2632–2636 (2008). [CrossRef]

]. In addition, small radii or thicknesses of FORSs make it possible to measure neutron fluxes with high spatial resolution in narrow spaces [10

10. T. Yagi, H. Unesaki, T. Misawa, C. H. Pyeon, S. Shiroya, T. Matsumoto, and H. Harano, “Development of a small scintillation detector with an optical fiber for fast neutrons,” Appl. Radiat. Isot. 69(2), 539–544 (2011). [CrossRef] [PubMed]

]. Also, specific optical fibers such as metal coated optical fibers allow fiber-optic sensors to be exploited in high temperature conditions (up to 700°C) [11

11. S. M. Popov, V. V. Voloshin, I. L. Vorobyov, G. A. Ivanov, A. O. Kolosovskii, V. A. Isaev, and Y. K. Chamorovskii, “Optical loss of metal coated optical fibers at temperatures up to 800°C,” Opt. Mem. Neural. Networks 21(1), 45–51 (2012) (Information Optics). [CrossRef]

].

As sensor probes of FORSs, scintillators with neutron converters are generally employed to detect neutrons. Since neutrons rarely interact with media, converting materials having high cross sections for neutrons and emitting charged particles or gamma rays upon interacting with neutrons are required. It is well known that 157Gd and 6Li can be used as converters for thermal neutrons [12

12. D. A. Abdushukurov, A. A. Dzhuraev, S. S. Evteeva, P. P. Kovalenko, V. A. Leskin, V. A. Nikolaev, R. F. Sirodzhi, and F. B. Umarov, “Model calculation of efficiency of gadolinium based converters of thermal neutrons,” Nucl. Instrum. Meth. B 84(3), 400–404 (1994). [CrossRef]

,13

13. M. L. Crow, J. P. Hodges, and R. G. Cooper, “Shifting scintillator prototype large pixel wavelength-shifting fiber detector for the POWGEN3 powder diffractometer,” Nucl. Instrum. Meth. A 529(1-3), 287–292 (2004). [CrossRef]

]. Scintillators have been used to convert the charged particles or gamma rays emitted from neutron converters into measurable light signals [14

14. C. Mori, A. Uritani, H. Miyahara, T. Iguchi, S. Shiroya, K. Kobayashi, E. Takada, R. F. Fleming, Y. K. Dewaraja, D. Stuenkel, and G. F. Knoll, “Measurement of neutron and γ-ray intensity distributions with an optical fiber-scintillator detector,” Nucl. Instrum. Meth. A 422(1-3), 129–132 (1999). [CrossRef]

,15

15. M. Cinausero, M. Barbui, G. Prete, V. Rizzi, A. Andrighetto, S. Pesente, D. Fabris, M. Lunardon, G. Nebbia, G. Viesti, S. Moretto, M. Morando, A. Zenoni, F. Bocci, A. Donzella, G. Bonomi, and A. Fontana, “A proton recoil telescope for neutron spectroscopy,” J. Phys. Conf. Ser. 41, 219–224 (2006). [CrossRef]

]. The scintillators developed to date through a variety of studies have high scintillation efficiencies and short decay times. These types of materials, however, have some defects under specific conditions. In high ionization density, scintillation molecules can be temporarily damaged by high energy charged particles. This phenomenon, which is known as the quenching effect, causes non-proportionality between energy losses of charged particles and scintillation outputs [16

16. S. Mouatassim, G. J. Costa, G. Guillaume, B. Heusch, A. Huck, and M. Moszynski, “The light yield response of NE213 organic scintillators to charged particles resulting from neutron interactions,” Nucl. Instrum. Meth. A 359(3), 530–536 (1995). [CrossRef]

]. This kind of quenching effect depends on the scintillator quenching factor and it varies with material, the type and energy of incident particle. Furthermore, the scintillators have a temperature limitation and this restricts their use in high temperature conditions [17

17. Y. Furukawa, M. Tanaka, T. Nakazato, T. Tatsumi, M. Nishikino, H. Yamatani, K. Nagashima, T. Kimura, H. Murakami, S. Saito, N. Sarukura, H. Nishimura, K. Mima, Y. Kagamitani, D. Ehrentraut, and T. Fukuda, “Temperature dependence of scintillation properties for a hydrothermal-method-grown zinc oxide crystal evaluated by nickel-like silver laser pulses,” J. Opt. Soc. Am. B 25(7), B118–B121 (2008). [CrossRef]

,18

18. M. Danang Birowosuto, P. Dorenbos, G. Bizarri, C. W. E. van Eijk, K. W. Krämer, and H. U. Güdel, “Temperature dependent scintillation and luminescence characteristics of GdI3: Ce3+,” IEEE Trans. Nucl. Sci. 55, 1164–1169 (2008).

]. Generally, the ZnS:Ag having a density of 4.09 g/cm3 is employed for detecting charged particles generated from the neutron converters [10

10. T. Yagi, H. Unesaki, T. Misawa, C. H. Pyeon, S. Shiroya, T. Matsumoto, and H. Harano, “Development of a small scintillation detector with an optical fiber for fast neutrons,” Appl. Radiat. Isot. 69(2), 539–544 (2011). [CrossRef] [PubMed]

]. Although this kind of scintillator has a relatively high melting point such as 1700°C, its scintillation output varies with the temperatures and decreases steeply over 300°C [19

19. R. L. Boivin, Z. Lin, A. L. Roquemore, and S. J. Zweben, “Calibration of the TFTR lost alpha diagnostic,” Rev. Sci. Instrum. 63(10), 4418–4426 (1992). [CrossRef]

]. Plastic scintillating fibers also can be used to detect neutrons. Unfortunately, operating temperatures of theses scintillators are below 50°C therefore they cannot be used in high temperature conditions. Thus a novel sensor probe is required to exploit FORSs in extremely harsh environments such as in molten salts used for pyroprocessing and in the nuclear reactor core where ambient temperatures are about 550°C and 300°C, respectively.

Meanwhile, when a charged particle passes through a dielectric medium with a phase velocity greater than that of light, the electromagnetic field close to the particle polarizes the medium along its path, and then the electrons in the atoms follow the waveform of the pulse. Here, the waveform and the medium are called Cerenkov radiation and a Cerenkov radiator, respectively [20

20. J. V. Jelly, “Cerenkov radiation and its applications,” J. Appl. Phys. 6, 227–232 (1955).

]. In the case of gamma rays, Cerenkov radiation is produced by electrons generated by interactions between gamma rays and a medium. The Cerenkov radiation can be easily observed as a shimmer of blue light from the water in boiling- and pressurized-water reactors, and spent fuel storage pools [21

21. M. Kuribara and K. Nemoto, “Development of new UV-1.1. Cerenkov viewing device,” IEEE Trans. Nucl. Sci. 41(1), 331–335 (1994). [CrossRef]

]. This type of radiation has emission angles according to the particle energies and refractive indices of the media, and therefore the energies and incident angles of the particles can be determined by measuring the Cerenkov radiation [22

22. B. A. Khrenov, I. H. Park, and H. Salazar, “Detection of scattered Cherenkov radiation in cosmic ray observations from space,” Nucl. Instrum. Meth. A 553(1-2), 304–307 (2005). [CrossRef]

]. Also, in contrast to scintillation generated in scintillators, the Cerenkov radiation produced from the radiator can be exploited in high temperature and high ionization density conditions. In a high temperature tokamak, electron fluxes can be obtained by measuring the Cerenkov radiation generated from some crystals [23

23. L. Jakubowski, M. J. Sadowski, J. Zebrowski, M. Rabinski, K. Malinowski, R. Mirowski, Ph. Lotte, J. Gunn, J.-Y. Pascal, G. Colledani, V. Basiuk, M. Goniche, and M. Lipa, “Cherenkov-type diamond detectors for measurements of fast electrons in the TORE-SUPRA tokamak,” Rev. Sci. Instrum. 81(1), 013504 (2010). [CrossRef] [PubMed]

]. Also, the Cerenkov radiation generated in optical fibers allows us to measure relative depth doses without the quenching effect induced by heavy charged particles in a radiotherapy dosimetry [24

24. K. W. Jang, W. J. Yoo, S. H. Shin, D. Shin, and B. Lee, “Fiber-optic Cerenkov radiation sensor for proton therapy dosimetry,” Opt. Express 20(13), 13907–13914 (2012). [CrossRef] [PubMed]

]. Since this kind of quenching effect is induced by damaged scintillator molecules, non-scintillating materials do not have the quenching effect. The Cerenkov radiation has different mechanism from that of the scintillation; while the scintillation is produced from the excited scintillator molecule, the Cerenkov radiation is generated from temporally polarized atoms in the dielectric. Using some transparent dielectrics, it is possible to obtain the light signal without the quenching effect. Therefore, the Cerenkov radiation presents an attractive solution for employing FORSs in hazardous radiation conditions.

The objective of this study is to evaluate the feasibility of a FORS using the Cerenkov effect for detecting thermal neutrons. The FORS was fabricated with a Gd-foil, a rutile (TiO2) crystal, and a plastic optical fiber (POF). By using the Monte Carlo N-particle transport code (MCNPX) simulations, the relationship between fluxes of electrons inducing Cerenkov radiation in the sensor probe of the FORS and thermal neutron fluxes was determined. Also, the Cerenkov radiation generated in the FORS by irradiation of pure thermal neutron beams produced by the Kyoto University Research Reactor (KUR) was measured according to depths of polyethylene.

2. Cerenkov radiation in the radiator

As mentioned above, to produce Cerenkov radiation, charged particles should have energies over a threshold. The Cerenkov threshold energy (CTE; ETh) of a charged particle can be calculated using the special theory of relativity, as given in Eq. (1) [25

25. Z. W. Bell and L. A. Boatner, “Neutron detection via the Cherenkov effect,” IEEE Trans. Nucl. Sci. 57, 3800–3806 (2010).

].
ETh=m0c2(nn211),
(1)
where m0 is the rest mass of the charged particle, c is the phase velocity of light, and n is the refractive index of the Cerenkov radiator. Assuming the charged particles are electrons, CTE only varies according to the refractive index of the Cerenkov radiator.

The intensity of Cerenkov radiation (IC) generated by a charged particle per unit path can be obtained using the Frank-Tamm formula as follows [26

26. B. Brichard, A. F. Fernandez, H. Ooms, and F. Berghmans, “Fiber-optic gamma-flux monitoring in a fission reactor by means of Cerenkov radiation,” Meas. Sci. Technol. 18(10), 3257–3262 (2007). [CrossRef]

]:
IC=2παz2dλλ2(11β2n2),
(2)
where α is the fine structure constant ( = 1/137), z is the charge of the particle, λ is the wavelength of Cerenkov radiation, n is the refractive index of the medium, and β is the velocity of the particle relative to light. As seen in Eq. (2), the intensity of Cerenkov radiation is proportional to (1 1 / β2n2) and the value of β is close to ‘1’ for relativistic electrons. Accordingly, the intensity of Cerenkov radiation is nearly independent of the energies of relativistic electrons [27

27. A. S. Beddar, T. R. Mackie, and F. H. Attix, “Cerenkov radiation generated in optical fibres and other light pipes irradiated by electron beams,” Phys. Med. Biol. 37(4), 925–935 (1992). [CrossRef]

].

In the case of relativistic electrons, the intensity of Cerenkov radiation is proportional to electron flux. Since the electrons are directly or indirectly emitted by interactions between a neutron converter and neutrons, the electron flux is proportional to the neutron flux and the neutron capture cross section of the converter. Therefore, the total intensity of Cerenkov radiation (IC_total) generated in the radiator per unit volume can be expressed as follows:
IC_totalNe=kσϕρ,
(3)
IC_total=2παz2kσϕρdλλ2(11β2n2),
(4)
where Ne is the number of electrons per unit volume, k is a proportional factor, σ is the neutron capture cross section of the converter, φ is the neutron flux, and ρ is the density of the converter.

3. Materials and methods

To apply the Cerenkov effect for neutron detection, a neutron converter should satisfy several qualifications. When the neutrons interact with the converter, charged particles or gamma rays with sufficient energies should be emitted from the converter to generate Cerenkov radiation in the radiator. Also, the converter should have a high cross section for the neutrons to increase the number of Cerenkov photons because the Cerenkov radiation is a supersubtle light signal that is difficult to measure. Taking these requirements into consideration, in these experiments, a Gd-foil (GD-143220, Nilaco Co., Tokyo, Japan) with 99.9% 157Gd composition is employed as a neutron converter. The cross section of the isotope for thermal neutron capture is about 255,000 barns (10−24 cm2), which is among the highest nuclear cross sections found in any material [28

28. G. F. Knoll, Radiation Detection and Measurement (John Wiley & Sons, New York 1999), p.509.

]. As a result of thermal neutron capture, gamma rays with energies up to 7.8 MeV and 72 keV conversion electrons are emitted from the isotope [28

28. G. F. Knoll, Radiation Detection and Measurement (John Wiley & Sons, New York 1999), p.509.

,29

29. G. De Stasio, P. Casalbore, R. Pallini, B. Gilbert, F. Sanità, M. T. Ciotti, G. Rosi, A. Festinesi, L. M. Larocca, A. Rinelli, D. Perret, D. W. Mogk, P. Perfetti, M. P. Mehta, and D. Mercanti, “Gadolinium in human glioblastoma cells for gadolinium neutron capture therapy,” Cancer Res. 61(10), 4272–4277 (2001). [PubMed]

]. These energies are sufficient to produce Cerenkov radiation in a radiator having a high refractive index. Also, the Gd-foil can be used in high temperature conditions up to its melting point (1312°C). The dimensions and density of the Gd-foil used in this research are 5 × 5 × 0.025 mm3 and 7.9 g/cm3, respectively.

Throughout this study, a rutile crystal (Shinkosha Co. Ltd., Yokohama, Japan) was used as a Cerenkov radiator. For electrons with low energies, the Cerenkov radiator should have a high refractive index to produce Cerenkov radiation. The rutile crystal has a refractive index of 2.87 for 430 nm wavelength, and therefore the CTE of electrons in the rutile crystal to produce Cerenkov radiation is calculated as 34 keV by using Eq. (1). Thus, Cerenkov radiation can be produced by the electrons emitted from the Gd-foil. The melting point of the crystal is about 1843°C and its density is 4.23 g/cm3. The dimensions of the crystal used in this research are 10 × 10 × 0.1 mm3.

A photomultiplier tube (PMT; R1635, Hamamatsu Photonics K.K., Hamamatsu, Japan) was used to measure the Cerenkov radiation. The measurable wavelength range of the PMT is 300 ~650 nm and its peak sensitive wavelength is 420 nm. The dark current is about 1 nA. To analyze the electric pulse height of the PMT, a multichannel analyzer (MCA; 2100C/MCA, Laboratory Equipment Corporation Co. Ltd., Tsuchiura, Japan) was employed in our experiments.

As a neutron source, we used pure thermal neutron beams generated by the KUR. The neutrons obtained from the E3 port of KUR had a wavelength of 2.8 Å and this wavelength could be converted to energy of 0.01 eV. The flux and beam size of the neutron beams were 2 × 106 cm−2sec−1 and 10 × 10 mm2, respectively.

Figure 1
Fig. 1 Experimental setup with FORS to detect thermal neutrons.
shows the experimental setup with the FORS to detect thermal neutrons. In the experiments, the thermal neutron fluxes were obtained by measuring Cerenkov radiation generated from the FORS according to depths of the polyethylene. The sensor probe of the FORS consists of the rutile crystal and Gd-foil, as shown in Fig. 1. When the sensor probe is irradiated by the neutron beams, the electrons and gamma rays emitted from the Gd-foil pass through the rutile crystal. In this process, Cerenkov radiation is generated in the crystal and is then transmitted by a 5 m POF to the PMT. The amplified electric signals are then measured using the MCA and the supporting software (MCAWinUC, Laboratory Equipment Corporation Co. Ltd., Tsuchiura, Japan).

For relativistic electrons, the intensity of Cerenkov radiation is proportional to the fluxes of electrons whose energies are over the CTE. In the case of the rutile crystal, the CTE of electrons is about 34 keV. To detect the thermal neutrons using a FORS with the Cerenkov effect, the relationship between fluxes of electrons over the CTE in the rutile crystal and thermal neutron fluxes should be determined. Also, we should clarify whether the electrons generated in the rutile crystal by interactions between the Gd-foil and thermal neutrons have sufficient energies to produce Cerenkov radiation. To answer the above queries, the energies and fluxes of electrons generated in the rutile crystal were calculated using MCNPX simulations.

The MCNPX simulation scheme can be found in Fig. 2
Fig. 2 MCNPX simulation scheme.
. In this simulation, the plane source which emits thermal neutrons with a negative normal vector was used. The energy distribution of thermal neutrons had the Maxwell fission spectrum with a peak at the energy of 0.01 eV and size of the plane source was 10 × 10 mm2. The polyethylene block with a thickness from 0 mm to 12 mm was placed between the source and the sensor probe which consists of the Gd-foil and rutile crystal. Also, only the rutile crystal without Gd-foil was simulated to compare with the simulation result of the sensor probe.

4. Experimental results and discussion

4.1 MCNPX simulations

Figure 3
Fig. 3 Calculated fluxes of gamma photons and electrons in a rutile crystal with and without a Gd-foil.
shows the fluxes of gamma photons and electrons in the rutile crystal with and without the Gd-foil by irradiation of thermal neutron beams. Because the thermal neutrons could produce electrons over the CTE in a single rutile crystal in the absence of the Gd-foil, gamma photons and electron fluxes in the rutile crystal should be calculated according to the existence of the Gd-foil. As shown in the results, fluxes of gamma photons and electrons generated in only the rutile crystal are insignificant, because thermal neutrons do not have many chances to interact with this material. The total cross section of the rutile crystal for thermal neutrons is about 4.1 barns; this is an extremely small cross-section, particularly compared to that of 157Gd. In Fig. 3, the rates for fluxes of gamma photons and electrons in the crystal only to those with the Gd-foil are 1.9% and 2.6%, respectively; therefore the fluxes of gamma photons and electrons in the sensor probe consisting of the rutile crystal and the Gd-foil are mostly induced by interactions between the Gd-foil and the thermal neutrons. This result shows that the sensitivity of the FORS used in this study depends very strongly on the neutron capture cross section of 157Gd.

In the MCNPX simulations, to produce reliable confidence intervals, the relative error (R) of calculated result should be less than 0.10. In this simulation, the quantities of ‘R’ for electron fluxes of the rutile crystal with Gd-foil and only the rutile crystal are 0.0073 and 0.0235 (for gamma photons, 0.0044 and 0.0177), respectively, and therefore these results can be regarded as reliable datum.

The energy distribution of electrons generated in the rutile crystal can be found in Fig. 4
Fig. 4 Calculated electron fluxes for energy in a rutile crystal with and without a Gd-foil.
. Although the energy distribution of electrons generated in the rutile crystal is very broad, the peak electron flux is in an energy range below 34 keV. The electrons in this range cannot contribute to producing Cerenkov radiation in the rutile crystal because the CTE of electrons in the crystal is about 34 keV, as mentioned above. Most of these electrons are derived from conversion electrons with energy of 72 keV emitted from the Gd-foil, and the conversion electrons can lose their energy gradually to a level below the CTE by passing through the Gd-foil and the rutile crystal. On the other hand, since the gamma rays generated from the Gd-foil have relatively high energies of up to 7.8 MeV, the electrons subsequently induced by interactions between the gamma rays and the rutile crystal have sufficient energies to produce Cerenkov radiation in the crystal. Throughout the MCNPX simulations, the electron fluxes over the CTE were used to estimate the electron fluxes inducing Cerenkov radiation in the rutile crystal.

Figure 5
Fig. 5 Normalized electron fluxes and average energies of electrons according to depths of polyethylene ((a) normalized electron fluxes, (b) average energies of electrons).
shows normalized electron fluxes and average energies of electrons according to depths of polyethylene. In general, the intensity of Cerenkov radiation varies with the electron energy. For a proportional relationship between the electron flux generated in the rutile crystal and the intensity of Cerenkov radiation, the electrons should be relativistic electrons or they should have the same energy distribution in different neutron flux conditions. In the simulations, the electron energies were distributed in a rather wide range, whereas the energy distributions were nearly the same for different depths of polyethylene, as shown in Fig. 5(a). Moreover, in Fig. 5(b), the average energies of the electrons were maintained uniformly as 1.2 MeV; electrons with this energy can be regarded as relativistic electrons. These results indicate that the intensity of Cerenkov radiation generated in the probe of the FORS merely varies with the electron fluxes.

The relationship between electron fluxes in the rutile crystal and thermal neutron fluxes can be found in Fig. 6
Fig. 6 Relationship between electron fluxes in the rutile crystal and thermal neutron fluxes according to depths of polyethylene ((a) calculated electron fluxes in the rutile crystal and thermal neutron fluxes, (b) linearity between electron fluxes in the rutile crystal and thermal neutron fluxes).
. In the simulations, the electron fluxes in the rutile crystal and the fluxes of thermal neutron in an energy range between 0.01 eV and 1.0 eV were obtained at different depths of polyethylene. The fluxes of electrons over the CTE present good agreement with those of thermal neutrons, as shown in Fig. 6(a). The mean difference between the electron fluxes and thermal neutron fluxes was 0.95 ± 0.54%. In this simulation, the mean relative errors of calculated electron and thermal neutron fluxes according to different depths of polyethylene are 0.0089 and 0.0004, respectively.

Figure 6(b) shows linearity between the electron fluxes in the rutile crystal and the thermal neutron fluxes. This result was obtained by one-to-one correspondence of the electron fluxes and the thermal neutron fluxes. Here, the linear fitting equation is near to an identity function having a gradient of ‘1’. The R-square value, which is often called the coefficient of determination, of the fitting line was 0.9986. The results of the simulation revealed that electron fluxes in the probe of the FORS are directly correlated to the thermal neutron fluxes.

4.2 Detection of thermal neutrons using FORS

Figure 8
Fig. 8 Intensities of Cerenkov radiation generated in FORS by irradiation of thermal neutron beams according to depths of polyethylene.
shows the intensities of Cerenkov radiation generated in the FORS by irradiation of thermal neutron beams according to depths of polyethylene. In the results, the intensities of Cerenkov radiation generated in the FORS decreased with increasing polyethylene thickness. Although neutrons rarely interact with matter, they have relatively high cross sections for hydrogen materials such as polyethylene and water. Therefore, the thermal neutron fluxes gradually decreased according to the polyethylene thickness. The results of gold-foil activation method also can be found in Fig. 8. When the neutrons are irradiated on the gold-foil which is made of the 197Au, this material becomes a radioactive isotope emitting 411 keV gamma-rays; here, the neutron flux can be estimated by measuring the activity of gold-foil. This method is normally used for measuring the neutron fluxes in the nuclear facilities. The results obtained by the FORS have small discrepancies from the thermal neutron fluxes calculated by the MCNPX simulation and results of the gold-foil activation method due to the instrumental error (10%), but show a similar trend to those of the simulation and the activation method.

4. Conclusion

Scintillators have been widely used as sensor probes of FORSs. However, there are some limitations to their use in extremely harsh environments. We proposed a novel method for detecting thermal neutrons with a FORS using the Cerenkov effect, which makes it possible to measure some radiation without any scintillation material. A FORS for detecting thermal neutrons was fabricated using a Gd-foil, a rutile crystal, and a POF. The relationship between electron fluxes in the sensor probe of the FORS and thermal neutron fluxes was determined using MCNPX simulations. The simulation results show that the electron fluxes in the sensor probe linearly increased in proportion to the thermal neutron fluxes. Also, the Cerenkov radiation generated in the FORS by irradiation of pure thermal neutron beams was measured in different depths of polyethylene. The results obtained by the FORS were close to those of the MCNPX simulations and the gold-foil activation method.

Further study should be carried out to exploit FORSs for detecting thermal neutrons in high temperature conditions. In this study, we used the POF to transmit the Cerenkov radiation generated in the rutile crystal. Unfortunately, since the maximum operating temperature of POF is about 70°C, this fiber cannot be used in extremely high temperatures. In the following study, therefore, a metal coated optical fiber which can stand high temperatures (up to 700°C) will be used as a transmitting fiber. In addition, the sensor probe will be covered with quartz or pyrex glass for thermal protection. It is anticipated that the novel and simple FORS using the Cerenkov effect proposed here can be effectively used to measure radiation in hazardous nuclear facilities.

Acknowledgments

This work was supported by Konkuk University.

References and links

1.

T. K. McKnight, J. B. Czirr, K. Littrell, and B. J. Campbell, “The flexible embedded-fiber neutron detector,” Nucl. Instrum. Meth. A 586(2), 246–250 (2008). [CrossRef]

2.

M. Ishikawa, K. Ono, Y. Sakurai, H. Unesaki, A. Uritani, G. Bengua, T. Kobayashi, K. Tanaka, and T. Kosako, “Development of real-time thermal neutron monitor using boron-loaded plastic scintillator with optical fiber for boron neutron capture therapy,” Appl. Radiat. Isot. 61(5), 775–779 (2004). [CrossRef] [PubMed]

3.

E. Takada, T. Iguchi, H. Takahashi, M. Nakazawa, M. Sasao, M. Osakabe, and Y. Ikeda, “Distributed sensing of fusion neutrons by plastic scintillating fibers,” Fusion Eng. Des. 34-35, 591–594 (1997). [CrossRef]

4.

A. F. Fernandez, B. Brichard, S. O’Keeffe, C. Fitzpatrick, E. Lewis, J.-R. Vaille, L. Dusseau, D. A. Jackson, F. Ravotti, M. Glaser, and H. El-Rabii, “Real-time fiber optic radiation dosimeters for nuclear environment monitoring around thermonuclear reactors,” Fusion Eng. Des. 83(1), 50–59 (2008). [CrossRef]

5.

S. O’Keeffe, C. Fitzpatrick, E. Lewis, and A. I. Al-Shamma’a, “A review of optical fibre radiation dosimeters,” Sensor Rev. 28(2), 136–142 (2008). [CrossRef]

6.

B. Lee, W. Y. Choi, and J. K. Walker, “Polymer-polymer miscibility study for plastic gradient index optical fiber,” Polym. Eng. Sci. 40(9), 1996–1999 (2000). [CrossRef]

7.

G. Bartesaghi, V. Conti, M. Prest, V. Mascagna, S. Scazzi, P. Cappelletti, M. Frigerio, S. Gelosa, A. Monti, A. Ostinelli, A. Mozzanica, R. Bevilacqua, G. Giannini, P. Totaro, and E. Vallazza, “A real time scintillating fiber dosimeter for gamma and neutron monitoring on radiotherapy accelerators,” Nucl. Instrum. Meth. A 572(1), 228–230 (2007). [CrossRef]

8.

B. Lee, K. W. Jang, D. H. Cho, W. J. Yoo, S. H. Shin, G.-R. Tack, S.-C. Chung, S. Kim, H. Cho, B. G. Park, J. H. Moon, and S. Kim, “Characterization of one-dimensional fiber-optic scintillating detectors for electron-beam therapy dosimetry,” IEEE Trans. Nucl. Sci. 55(5), 2627–2631 (2008). [CrossRef]

9.

B. Lee, K. W. Jang, D. H. Cho, W. J. Yoo, S. H. Shin, H. S. Kim, J. H. Yi, S. Kim, H. Cho, B. G. Park, J. H. Moon, and S. Kim, “Measurement of two-dimensional photon beam distributions using a fiber-optic radiation sensor for small field radiation therapy,” IEEE Trans. Nucl. Sci. 55(5), 2632–2636 (2008). [CrossRef]

10.

T. Yagi, H. Unesaki, T. Misawa, C. H. Pyeon, S. Shiroya, T. Matsumoto, and H. Harano, “Development of a small scintillation detector with an optical fiber for fast neutrons,” Appl. Radiat. Isot. 69(2), 539–544 (2011). [CrossRef] [PubMed]

11.

S. M. Popov, V. V. Voloshin, I. L. Vorobyov, G. A. Ivanov, A. O. Kolosovskii, V. A. Isaev, and Y. K. Chamorovskii, “Optical loss of metal coated optical fibers at temperatures up to 800°C,” Opt. Mem. Neural. Networks 21(1), 45–51 (2012) (Information Optics). [CrossRef]

12.

D. A. Abdushukurov, A. A. Dzhuraev, S. S. Evteeva, P. P. Kovalenko, V. A. Leskin, V. A. Nikolaev, R. F. Sirodzhi, and F. B. Umarov, “Model calculation of efficiency of gadolinium based converters of thermal neutrons,” Nucl. Instrum. Meth. B 84(3), 400–404 (1994). [CrossRef]

13.

M. L. Crow, J. P. Hodges, and R. G. Cooper, “Shifting scintillator prototype large pixel wavelength-shifting fiber detector for the POWGEN3 powder diffractometer,” Nucl. Instrum. Meth. A 529(1-3), 287–292 (2004). [CrossRef]

14.

C. Mori, A. Uritani, H. Miyahara, T. Iguchi, S. Shiroya, K. Kobayashi, E. Takada, R. F. Fleming, Y. K. Dewaraja, D. Stuenkel, and G. F. Knoll, “Measurement of neutron and γ-ray intensity distributions with an optical fiber-scintillator detector,” Nucl. Instrum. Meth. A 422(1-3), 129–132 (1999). [CrossRef]

15.

M. Cinausero, M. Barbui, G. Prete, V. Rizzi, A. Andrighetto, S. Pesente, D. Fabris, M. Lunardon, G. Nebbia, G. Viesti, S. Moretto, M. Morando, A. Zenoni, F. Bocci, A. Donzella, G. Bonomi, and A. Fontana, “A proton recoil telescope for neutron spectroscopy,” J. Phys. Conf. Ser. 41, 219–224 (2006). [CrossRef]

16.

S. Mouatassim, G. J. Costa, G. Guillaume, B. Heusch, A. Huck, and M. Moszynski, “The light yield response of NE213 organic scintillators to charged particles resulting from neutron interactions,” Nucl. Instrum. Meth. A 359(3), 530–536 (1995). [CrossRef]

17.

Y. Furukawa, M. Tanaka, T. Nakazato, T. Tatsumi, M. Nishikino, H. Yamatani, K. Nagashima, T. Kimura, H. Murakami, S. Saito, N. Sarukura, H. Nishimura, K. Mima, Y. Kagamitani, D. Ehrentraut, and T. Fukuda, “Temperature dependence of scintillation properties for a hydrothermal-method-grown zinc oxide crystal evaluated by nickel-like silver laser pulses,” J. Opt. Soc. Am. B 25(7), B118–B121 (2008). [CrossRef]

18.

M. Danang Birowosuto, P. Dorenbos, G. Bizarri, C. W. E. van Eijk, K. W. Krämer, and H. U. Güdel, “Temperature dependent scintillation and luminescence characteristics of GdI3: Ce3+,” IEEE Trans. Nucl. Sci. 55, 1164–1169 (2008).

19.

R. L. Boivin, Z. Lin, A. L. Roquemore, and S. J. Zweben, “Calibration of the TFTR lost alpha diagnostic,” Rev. Sci. Instrum. 63(10), 4418–4426 (1992). [CrossRef]

20.

J. V. Jelly, “Cerenkov radiation and its applications,” J. Appl. Phys. 6, 227–232 (1955).

21.

M. Kuribara and K. Nemoto, “Development of new UV-1.1. Cerenkov viewing device,” IEEE Trans. Nucl. Sci. 41(1), 331–335 (1994). [CrossRef]

22.

B. A. Khrenov, I. H. Park, and H. Salazar, “Detection of scattered Cherenkov radiation in cosmic ray observations from space,” Nucl. Instrum. Meth. A 553(1-2), 304–307 (2005). [CrossRef]

23.

L. Jakubowski, M. J. Sadowski, J. Zebrowski, M. Rabinski, K. Malinowski, R. Mirowski, Ph. Lotte, J. Gunn, J.-Y. Pascal, G. Colledani, V. Basiuk, M. Goniche, and M. Lipa, “Cherenkov-type diamond detectors for measurements of fast electrons in the TORE-SUPRA tokamak,” Rev. Sci. Instrum. 81(1), 013504 (2010). [CrossRef] [PubMed]

24.

K. W. Jang, W. J. Yoo, S. H. Shin, D. Shin, and B. Lee, “Fiber-optic Cerenkov radiation sensor for proton therapy dosimetry,” Opt. Express 20(13), 13907–13914 (2012). [CrossRef] [PubMed]

25.

Z. W. Bell and L. A. Boatner, “Neutron detection via the Cherenkov effect,” IEEE Trans. Nucl. Sci. 57, 3800–3806 (2010).

26.

B. Brichard, A. F. Fernandez, H. Ooms, and F. Berghmans, “Fiber-optic gamma-flux monitoring in a fission reactor by means of Cerenkov radiation,” Meas. Sci. Technol. 18(10), 3257–3262 (2007). [CrossRef]

27.

A. S. Beddar, T. R. Mackie, and F. H. Attix, “Cerenkov radiation generated in optical fibres and other light pipes irradiated by electron beams,” Phys. Med. Biol. 37(4), 925–935 (1992). [CrossRef]

28.

G. F. Knoll, Radiation Detection and Measurement (John Wiley & Sons, New York 1999), p.509.

29.

G. De Stasio, P. Casalbore, R. Pallini, B. Gilbert, F. Sanità, M. T. Ciotti, G. Rosi, A. Festinesi, L. M. Larocca, A. Rinelli, D. Perret, D. W. Mogk, P. Perfetti, M. P. Mehta, and D. Mercanti, “Gadolinium in human glioblastoma cells for gadolinium neutron capture therapy,” Cancer Res. 61(10), 4272–4277 (2001). [PubMed]

30.

Y. M. Protopopov and V. G. Vasil’chenko, “Radiation damage in plastic scintillators and optical fibers,” Nucl. Instrum. Meth. B 95(4), 496–500 (1995). [CrossRef]

OCIS Codes
(060.2370) Fiber optics and optical communications : Fiber optics sensors
(350.5610) Other areas of optics : Radiation
(280.4788) Remote sensing and sensors : Optical sensing and sensors

ToC Category:
Sensors

History
Original Manuscript: April 30, 2013
Revised Manuscript: June 5, 2013
Manuscript Accepted: June 5, 2013
Published: June 11, 2013

Citation
Kyoung Won Jang, Takahiro Yagi, Cheol Ho Pyeon, Wook Jae Yoo, Sang Hun Shin, Tsuyoshi Misawa, and Bongsoo Lee, "Feasibility of fiber-optic radiation sensor using Cerenkov effect for detecting thermal neutrons," Opt. Express 21, 14573-14582 (2013)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-21-12-14573


Sort:  Author  |  Year  |  Journal  |  Reset  

References

  1. T. K. McKnight, J. B. Czirr, K. Littrell, and B. J. Campbell, “The flexible embedded-fiber neutron detector,” Nucl. Instrum. Meth. A586(2), 246–250 (2008). [CrossRef]
  2. M. Ishikawa, K. Ono, Y. Sakurai, H. Unesaki, A. Uritani, G. Bengua, T. Kobayashi, K. Tanaka, and T. Kosako, “Development of real-time thermal neutron monitor using boron-loaded plastic scintillator with optical fiber for boron neutron capture therapy,” Appl. Radiat. Isot.61(5), 775–779 (2004). [CrossRef] [PubMed]
  3. E. Takada, T. Iguchi, H. Takahashi, M. Nakazawa, M. Sasao, M. Osakabe, and Y. Ikeda, “Distributed sensing of fusion neutrons by plastic scintillating fibers,” Fusion Eng. Des.34-35, 591–594 (1997). [CrossRef]
  4. A. F. Fernandez, B. Brichard, S. O’Keeffe, C. Fitzpatrick, E. Lewis, J.-R. Vaille, L. Dusseau, D. A. Jackson, F. Ravotti, M. Glaser, and H. El-Rabii, “Real-time fiber optic radiation dosimeters for nuclear environment monitoring around thermonuclear reactors,” Fusion Eng. Des.83(1), 50–59 (2008). [CrossRef]
  5. S. O’Keeffe, C. Fitzpatrick, E. Lewis, and A. I. Al-Shamma’a, “A review of optical fibre radiation dosimeters,” Sensor Rev.28(2), 136–142 (2008). [CrossRef]
  6. B. Lee, W. Y. Choi, and J. K. Walker, “Polymer-polymer miscibility study for plastic gradient index optical fiber,” Polym. Eng. Sci.40(9), 1996–1999 (2000). [CrossRef]
  7. G. Bartesaghi, V. Conti, M. Prest, V. Mascagna, S. Scazzi, P. Cappelletti, M. Frigerio, S. Gelosa, A. Monti, A. Ostinelli, A. Mozzanica, R. Bevilacqua, G. Giannini, P. Totaro, and E. Vallazza, “A real time scintillating fiber dosimeter for gamma and neutron monitoring on radiotherapy accelerators,” Nucl. Instrum. Meth. A572(1), 228–230 (2007). [CrossRef]
  8. B. Lee, K. W. Jang, D. H. Cho, W. J. Yoo, S. H. Shin, G.-R. Tack, S.-C. Chung, S. Kim, H. Cho, B. G. Park, J. H. Moon, and S. Kim, “Characterization of one-dimensional fiber-optic scintillating detectors for electron-beam therapy dosimetry,” IEEE Trans. Nucl. Sci.55(5), 2627–2631 (2008). [CrossRef]
  9. B. Lee, K. W. Jang, D. H. Cho, W. J. Yoo, S. H. Shin, H. S. Kim, J. H. Yi, S. Kim, H. Cho, B. G. Park, J. H. Moon, and S. Kim, “Measurement of two-dimensional photon beam distributions using a fiber-optic radiation sensor for small field radiation therapy,” IEEE Trans. Nucl. Sci.55(5), 2632–2636 (2008). [CrossRef]
  10. T. Yagi, H. Unesaki, T. Misawa, C. H. Pyeon, S. Shiroya, T. Matsumoto, and H. Harano, “Development of a small scintillation detector with an optical fiber for fast neutrons,” Appl. Radiat. Isot.69(2), 539–544 (2011). [CrossRef] [PubMed]
  11. S. M. Popov, V. V. Voloshin, I. L. Vorobyov, G. A. Ivanov, A. O. Kolosovskii, V. A. Isaev, and Y. K. Chamorovskii, “Optical loss of metal coated optical fibers at temperatures up to 800°C,” Opt. Mem. Neural. Networks21(1), 45–51 (2012) (Information Optics). [CrossRef]
  12. D. A. Abdushukurov, A. A. Dzhuraev, S. S. Evteeva, P. P. Kovalenko, V. A. Leskin, V. A. Nikolaev, R. F. Sirodzhi, and F. B. Umarov, “Model calculation of efficiency of gadolinium based converters of thermal neutrons,” Nucl. Instrum. Meth. B84(3), 400–404 (1994). [CrossRef]
  13. M. L. Crow, J. P. Hodges, and R. G. Cooper, “Shifting scintillator prototype large pixel wavelength-shifting fiber detector for the POWGEN3 powder diffractometer,” Nucl. Instrum. Meth. A529(1-3), 287–292 (2004). [CrossRef]
  14. C. Mori, A. Uritani, H. Miyahara, T. Iguchi, S. Shiroya, K. Kobayashi, E. Takada, R. F. Fleming, Y. K. Dewaraja, D. Stuenkel, and G. F. Knoll, “Measurement of neutron and γ-ray intensity distributions with an optical fiber-scintillator detector,” Nucl. Instrum. Meth. A422(1-3), 129–132 (1999). [CrossRef]
  15. M. Cinausero, M. Barbui, G. Prete, V. Rizzi, A. Andrighetto, S. Pesente, D. Fabris, M. Lunardon, G. Nebbia, G. Viesti, S. Moretto, M. Morando, A. Zenoni, F. Bocci, A. Donzella, G. Bonomi, and A. Fontana, “A proton recoil telescope for neutron spectroscopy,” J. Phys. Conf. Ser.41, 219–224 (2006). [CrossRef]
  16. S. Mouatassim, G. J. Costa, G. Guillaume, B. Heusch, A. Huck, and M. Moszynski, “The light yield response of NE213 organic scintillators to charged particles resulting from neutron interactions,” Nucl. Instrum. Meth. A359(3), 530–536 (1995). [CrossRef]
  17. Y. Furukawa, M. Tanaka, T. Nakazato, T. Tatsumi, M. Nishikino, H. Yamatani, K. Nagashima, T. Kimura, H. Murakami, S. Saito, N. Sarukura, H. Nishimura, K. Mima, Y. Kagamitani, D. Ehrentraut, and T. Fukuda, “Temperature dependence of scintillation properties for a hydrothermal-method-grown zinc oxide crystal evaluated by nickel-like silver laser pulses,” J. Opt. Soc. Am. B25(7), B118–B121 (2008). [CrossRef]
  18. M. Danang Birowosuto, P. Dorenbos, G. Bizarri, C. W. E. van Eijk, K. W. Krämer, and H. U. Güdel, “Temperature dependent scintillation and luminescence characteristics of GdI3: Ce3+,” IEEE Trans. Nucl. Sci.55, 1164–1169 (2008).
  19. R. L. Boivin, Z. Lin, A. L. Roquemore, and S. J. Zweben, “Calibration of the TFTR lost alpha diagnostic,” Rev. Sci. Instrum.63(10), 4418–4426 (1992). [CrossRef]
  20. J. V. Jelly, “Cerenkov radiation and its applications,” J. Appl. Phys.6, 227–232 (1955).
  21. M. Kuribara and K. Nemoto, “Development of new UV-1.1. Cerenkov viewing device,” IEEE Trans. Nucl. Sci.41(1), 331–335 (1994). [CrossRef]
  22. B. A. Khrenov, I. H. Park, and H. Salazar, “Detection of scattered Cherenkov radiation in cosmic ray observations from space,” Nucl. Instrum. Meth. A553(1-2), 304–307 (2005). [CrossRef]
  23. L. Jakubowski, M. J. Sadowski, J. Zebrowski, M. Rabinski, K. Malinowski, R. Mirowski, Ph. Lotte, J. Gunn, J.-Y. Pascal, G. Colledani, V. Basiuk, M. Goniche, and M. Lipa, “Cherenkov-type diamond detectors for measurements of fast electrons in the TORE-SUPRA tokamak,” Rev. Sci. Instrum.81(1), 013504 (2010). [CrossRef] [PubMed]
  24. K. W. Jang, W. J. Yoo, S. H. Shin, D. Shin, and B. Lee, “Fiber-optic Cerenkov radiation sensor for proton therapy dosimetry,” Opt. Express20(13), 13907–13914 (2012). [CrossRef] [PubMed]
  25. Z. W. Bell and L. A. Boatner, “Neutron detection via the Cherenkov effect,” IEEE Trans. Nucl. Sci.57, 3800–3806 (2010).
  26. B. Brichard, A. F. Fernandez, H. Ooms, and F. Berghmans, “Fiber-optic gamma-flux monitoring in a fission reactor by means of Cerenkov radiation,” Meas. Sci. Technol.18(10), 3257–3262 (2007). [CrossRef]
  27. A. S. Beddar, T. R. Mackie, and F. H. Attix, “Cerenkov radiation generated in optical fibres and other light pipes irradiated by electron beams,” Phys. Med. Biol.37(4), 925–935 (1992). [CrossRef]
  28. G. F. Knoll, Radiation Detection and Measurement (John Wiley & Sons, New York 1999), p.509.
  29. G. De Stasio, P. Casalbore, R. Pallini, B. Gilbert, F. Sanità, M. T. Ciotti, G. Rosi, A. Festinesi, L. M. Larocca, A. Rinelli, D. Perret, D. W. Mogk, P. Perfetti, M. P. Mehta, and D. Mercanti, “Gadolinium in human glioblastoma cells for gadolinium neutron capture therapy,” Cancer Res.61(10), 4272–4277 (2001). [PubMed]
  30. Y. M. Protopopov and V. G. Vasil’chenko, “Radiation damage in plastic scintillators and optical fibers,” Nucl. Instrum. Meth. B95(4), 496–500 (1995). [CrossRef]

Cited By

Alert me when this paper is cited

OSA is able to provide readers links to articles that cite this paper by participating in CrossRef's Cited-By Linking service. CrossRef includes content from more than 3000 publishers and societies. In addition to listing OSA journal articles that cite this paper, citing articles from other participating publishers will also be listed.


« Previous Article  |  Next Article »

OSA is a member of CrossRef.

CrossCheck Deposited