Fiber-optic Cerenkov Radiation Sensor Research Articles

Monte Carlo simulation of gamma-ray distribution around spent nuclear fuel assembly using a fiber-optic Cerenkov radiation sensor

A fiber-optic Cerenkov radiation sensor (FOCRS), which utilizes transparent core of the optical fiber as a sensing material of gamma ray, has been evaluated a feasibility in application of determining radiation release characteristic of spent nuclear fuel by Monte Carlo simulation with GEANT4 simulation toolkit. A simulation model with Westinghouse type 17 × 17 fuel assembly and the FOCRS were constructed with GEANT4 and the nuclide composition of spent nuclear fuel was evaluated with ORIGEN-ARP. The simulation results exhibit that the FOCRS could describe the gamma ray distribution emitted from spent nuclear fuel assembly. The FORCS, therefore, can be used to evaluate gamma ray distribution at extremely radiation environment around the spent nuclear fuel assembly.

SU‐G‐TeP2‐15: Feasibility Study of Fiber‐Optic Cerenkov Radiation Sensors for in Vivo Measurement: Dosimetric Characterization and Clinical Application in Proton Beams

Purpose:To evaluate the possibility of a fiber‐optic Cerenkov radiation sensor (FCRS) for in vivo dose verification in proton therapy.Methods:The Cerenkov radiation due to the proton beam was measured using a homemade phantom, consisting of a plastic optical fiber (POF, PGSCD1001‐13‐E, Toray, Tokyo, Japan) connected to each channel of a multianode photomultiplier tube (MAPMT:H7546, Hamamatsu Photonics, Shizuoka, Japan). Data were acquired using a multi‐anode photomultiplier tube with the NI‐DAQ system (National Instruments Texas, USA). The real‐time monitoring graphic user interface was programmed using Labview. The FCRS was analyzed for its dosimetrics characteristic in proton beam. To determine the accuracy of the FCRS in proton dose measurements, we compared the ionization chamber dose measurements using a water phantom. We investigated the feasibility of the FCRS for the measurement of dose distributions near the superficial region for proton plans with a varying separation between the target volume and the surface of 3 patients using a humanoid phantom.Results:The dose‐response has good linearity. Dose‐rate and energy dependence were found to be within 1%. Depth‐dose distributions in non‐modulated proton beams obtained with the FCRS was in good agreement with the depth‐dose measurements from the ionization chamber. To evaluate the dosimetric accuracy of the FCRS, the difference of isocenter dose between the delivery dose calculated by the treatment planning system and that measured by the FCRS was within 3%. With in vivo dosimetry using the humanoid phantom, the calculated surface doses overestimated measurements by 4%–8% using FCRS.Conclusion:In previous study, our results indicate that the performance of the array‐type FCRS was comparable to that of the currently used a multi‐layer ion chamber system. In this study, we also believe that the fiber‐optic Cerenkov radiation sensor has considerable potential for use with in vivo patient proton dosimetry.

Calculation of Thermal Neutron Induced Electron Fluxes Generated in a Fiber-Optic Cerenkov Radiation Sensor Using Monte Carlo N-Particle Transport Code

Calculation of Thermal Neutron Induced Electron Fluxes Generated in a Fiber-Optic Cerenkov Radiation Sensor Using Monte Carlo N-Particle Transport Code

Measurements of longitudinal gamma ray distribution using a multichannel fiber-optic Cerenkov radiation sensor

Cerenkov radiation occurs when charged particles are moving faster than the speed of light in a transparent dielectric medium. In optical fibers, Cerenkov radiation can also be generated due to the fiber’s dielectric components. Accordingly, the radiation-induced light signals can be obtained using the optical fibers without any scintillating material. In this study, we fabricated a multichannel, fiber-optic Cerenkov radiation sensor (FOCRS) system using silica optical fibers (SOFs), plastic optical fibers (POFs), an optical spectrometer, multi-anode photomultiplier tubes (MA-PMTs) and a scanning system to measure the light intensities of Cerenkov radiation induced by gamma rays. To evaluate the fading effects in optical fibers, the spectra of Cerenkov radiation generated in the SOFs and POFs were measured based on the irradiation time by using an optical spectrometer. In addition, we measured the longitudinal distribution of gamma rays emitted from the cylindrical type Co-60 source by using MA-PMTs. The result was also compared with the distribution of the electron flux calculated by using the Monte Carlo N-particle transport code (MCNPX).

사용후핵연료 집합체 모사장치를 이용한 광섬유 체렌코프 방사선 센서 시스템의 성능평가

Abstract When the charged particle travels in transparent medium with a velocity greater than that of light in the same medium, the elec-tromagnetic field close to the particle polarizes the medium along its path, and then the electrons in the atoms follow the waveform ofthe pulse which is called as Cerenkov light or radiation. This type of radiation can be easily observed in a spent fuel storage pit. In opticalfibers, the Cerenkov light also can be generated due to their dielectric components. Accordingly, the radiation-induced light signals canbe obtained using optical fibers without any scintillating material. In this study, to measure the intensities of Cerenkov radiation inducedby gamma-rays, we have fabricated the fiber-optic Cerenkov radiation sensor system using silica optical fibers, plastic optical fibers,multi-anode photomultiplier tubes, simulated spent fuel assembly and a scanning system. To characterize the Cerenkov radiation gen-erated in optical fibers, the intensities of Cerenkov radiation generated in the silica and plastic optical fibers were measured. Also, wemeasured the longitudinal distribution of gamma rays emitted from the Ir-192 isotope by using the fiber-optic Cerenkov radiation sensorsystem and simulated spent fuel assembly.Keywords: Cerenkov radiation, Fiber-optic sensor, Gamma ray, Ir-192 isotope, Simulated spent fuel assembly

SU-E-T-111: Development of Proton Dosimetry System Using Fiber-Optic Cerenkov Radiation Sensor Array

Purpose: We had developed and evaluated a new dosimetric system for proton therapy using array of fiber-optic Cerenkov radiation sensor (FOCRS) which can measure a percent depth dose (PDD) instantly. In this study, the Bragg peaks and spread out Bragg peak (SOBP) of the proton beams measured by FOCRS array were compared with those measured by an ion chamber. Methods & Method: We fabricated an optical fiber array of FOCRS in a handmade phantom which is composed of poly-methyl methacrylate (PMMA). There are 75 holes of 1mm diameter inside the phantom which is designed to be exposed in direction of beam when it is emerged in water phantom. The proton beam irradiation was carried out using IBA cyclotron PROTEUS 235 at national cancer center in Korea and a commercial data acquisition system was used to digitize the analog signal. Results: The measured Bragg peak and SOBP for the proton ranges of 7∼ 20 cm were well matched with the result from ion chamber. The comparison results show that the depth of proton beam ranges and the width of SOBP measured by array of FOCRS are comparable with the measurement from multi-layer ion chamber (MLIC) although there are some uncertainty in the measurement of FOCRS array for some specific beam ranges. Conclusion: The newly developed FOCRS array based dosimetric system for proton therapy can efficiently reduce the time and effort needed for proton beam range measurement compared to the conventional method and has the potential to be used for the proton pencil beam application.

Measurement of Cerenkov radiation induced by the gamma-rays of Co-60 therapy units using wavelength shifting fiber.

In this study, a wavelength shifting fiber that shifts ultra-violet and blue light to green light was employed as a sensor probe of a fiber-optic Cerenkov radiation sensor. In order to characterize Cerenkov radiation generated in the developed wavelength shifting fiber and a plastic optical fiber, spectra and intensities of Cerenkov radiation were measured with a spectrometer. The spectral peaks of light outputs from the wavelength shifting fiber and the plastic optical fiber were measured at wavelengths of 500 and 510 nm, respectively, and the intensity of transmitted light output of the wavelength shifting fiber was 22.2 times higher than that of the plastic optical fiber. Also, electron fluxes and total energy depositions of gamma-ray beams generated from a Co-60 therapy unit were calculated according to water depths using the Monte Carlo N-particle transport code. The relationship between the fluxes of electrons over the Cerenkov threshold energy and the energy depositions of gamma-ray beams from the Co-60 unit is a near-identity function. Finally, percentage depth doses for the gamma-ray beams were obtained using the fiber-optic Cerenkov radiation sensor, and the results were compared with those obtained by an ionization chamber. The average dose difference between the results of the fiber-optic Cerenkov radiation sensor and those of the ionization chamber was about 2.09%.

Development of a Cerenkov radiation sensor to detect low-energy beta-particles

We fabricated a novel fiber-optic Cerenkov radiation sensor using a Cerenkov radiator for measuring beta-particles. Instead of employing a scintillator, transparent liquids having various refractive indices were used as a Cerenkov radiator to serve as a sensing material. The experimental results showed that the amount of Cerenkov radiation due to the interaction with beta-particles increased as the refractive index of the Cerenkov radiator was increased as a results of a decrease of the Cerenkov threshold energy for electrons.

Development of a fiber-optic Cerenkov radiation sensor to verify spent fuel: Characterization of the Cerenkov radiation generated from an optical fiber

In this study, we characterized the Cerenkov radiation generated from optical fibers as fundamental research for the development of a fiber-optic Cerenkov radiation sensor to verify spent fuel. We measured the amount of Cerenkov radiation according to OH content and numerical aperture of the optical fiber. Also, we measured the Cerenkov radiation as functions of the length and the diameter of the optical fiber. As a result, the silica optical fibers with high numerical aperture and high OH content were efficient and stable for gathering the Cerenkov radiation generated in the optical fiber. Also, the intensity of the Cerenkov radiation generated in the optical fiber was proportional to the irradiated length and to the square of the irradiated diameter.

Fiber-optic Cerenkov radiation sensor for proton therapy dosimetry

In proton therapy dosimetry, a fiber-optic radiation sensor incorporating a scintillator must undergo complicated correction processes due to the quenching effect of the scintillator. To overcome the drawbacks of the fiber-optic radiation sensor, we proposed an innovative method using the Cerenkov radiation generated in plastic optical fibers. In this study, we fabricated a fiber-optic Cerenkov radiation sensor without an organic scintillator to measure Cerenkov radiation induced by therapeutic proton beams. Bragg peaks and spread-out Bragg peaks of proton beams were measured using the fiber-optic Cerenkov radiation sensor and the results were compared with those of an ionization chamber and a fiber-optic radiation sensor incorporating an organic scintillator. From the results, we could obtain the Bragg peak and the spread-out Bragg peak of proton beams without quenching effects induced by the scintillator, and these results were in good agreement with those of the ionization chamber. We also measured the Cerenkov radiation generated from the fiber-optic Cerenkov radiation sensor as a function of the dose rate of the proton beam.