Characterization of a plastic dosimeter based on organic semiconductor photodiodes and scintillator

Posar, Jessie A.; Davis, Joel; Brace, Owen J.; Sellin, P.J.; Griffith, Matthew J.; Dhez, Olivier; Wilkinson, Dean; Lerch, Michael L. F; Rosenfeld, Anatoly B.; Petasecca, Marco

doi:10.1016/j.phro.2020.05.007

Cited by 14 publications

(15 citation statements)

References 19 publications

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“…37 This is significantly below the threshold dose of 500 Gy for which γ-induced degradation has been observed in organic semiconductor photosensors. 38 Conclusions. We have demonstrated a novel organic− inorganic composite material for direct detection of thermal neutrons, based on thick PTAA layers in which boron nanoparticles are homogeneously dispersed.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Boron-Loaded Polymeric Sensor for the Direct Detection of Thermal Neutrons

Chatzispyroglou

Keddie

Sellin

2020

ACS Appl. Mater. Interfaces

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We report the first demonstration of a solid-state, directconversion sensor for thermal neutrons based on a polymer/inorganic nanocomposite. Sensors were fabricated from ultrathick films of poly(triarylamine) (PTAA) semiconducting polymer, with thicknesses up to 100 μm. Boron nanoparticles (NPs) were dispersed throughout the PTAA film to provide the neutron stopping power arising from the high thermal neutron cross section of the isotope 10 B. To maximize the quantum efficiency (QE) of the sensor to thermal neutrons, a high volume fraction of homogeneously dispersed boron nanoparticles was achieved in the thick PTAA film using an optimized processing method. Thick active layers were realized using a high molecular weight of the PTAA so that molecular entanglements provide a high cohesive strength. A nonionic surfactant was used to stabilize the boron dispersion in solvent and hence suppress the formation of agglomerates and associated electrical pathways. Boron nanoparticle loadings of up to ten volume percent were achieved, with thermal neutron quantum efficiency estimates up to 6% resulting. The sensors' neutron responses were characterized under a high flux thermal neutron exposure, showing a linear correlation between the response current and the thermal neutron flux up to ∼10 7 cm −2 s −1 . Polymer-based boron nanocomposite sensors offer a new neutron detection technology that uses low-cost, scalable solution processing and provides an alternative to traditional neutron sensors that use rare isotopes, such as 3 He.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Boron-Loaded Polymeric Sensor for the Direct Detection of Thermal Neutrons

Chatzispyroglou

Keddie

Sellin

2020

ACS Appl. Mater. Interfaces

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“…Such blue wavelengths are also emitted from common plastic scintillators that are used as indirect radiation detectors for dosimetry (Nakamura et al, 2011). Organic semiconductors have been coupled with plastic scintillators for applications in dosimetry, demonstrating their high sensitivity to these wavelengths (Posar et al, 2020a). The effect of spurious light from the surrounding transparent material, similar to the polyethylene barrier film, is a well established phenomenon in scintillation fibre-optic dosimetry (Beddar et al, 1992).…”

Section: Geant4 Simulation Resultsmentioning

confidence: 99%

Towards high spatial resolution tissue-equivalent dosimetry for microbeam radiation therapy using organic semiconductors

Posar

Large

Alnaghy

et al. 2021

J Synchrotron Radiat

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Spatially fractionated ultra-high-dose-rate beams used during microbeam radiation therapy (MRT) have been shown to increase the differential response between normal and tumour tissue. Quality assurance of MRT requires a dosimeter that possesses tissue equivalence, high radiation tolerance and spatial resolution. This is currently an unsolved challenge. This work explored the use of a 500 nm thick organic semiconductor for MRT dosimetry on the Imaging and Medical Beamline at the Australian Synchrotron. Three beam filters were used to irradiate the device with peak energies of 48, 76 and 88 keV with respective dose rates of 3668, 500 and 209 Gy s−1. The response of the device stabilized to 30% efficiency after an irradiation dose of 30 kGy, with a 0.5% variation at doses of 35 kGy and higher. The calibration factor after pre-irradiation was determined to be 1.02 ± 0.005 µGy per count across all three X-ray energy spectra, demonstrating the unique advantage of using tissue-equivalent materials for dosimetry. The percentage depth dose curve was within ±5% of the PTW microDiamond detector. The broad beam was fractionated into 50 microbeams (50 µm FHWM and 400 µm centre-to-centre distance). For each beam filter, the FWHMs of all 50 microbeams were measured to be 51 ± 1.4, 53 ± 1.4 and 69 ± 1.9 µm, for the highest to lowest dose rate, respectively. The variation in response suggested the photodetector possessed dose-rate dependence. However, its ability to reconstruct the microbeam profile was affected by the presence of additional dose peaks adjacent to the one generated by the X-ray microbeam. Geant4 simulations proved that the additional peaks were due to optical photons generated in the barrier film coupled to the sensitive volume. The simulations also confirmed that the amplitude of the additional peak in comparison with the microbeam decreased for spectra with lower peak energies, as observed in the experimental data. The material packaging can be optimized during fabrication by solution processing onto a flexible substrate with a non-fluorescent barrier film. With these improvements, organic photodetectors show promising prospects as a cost-effective high spatial resolution tissue-equivalent flexible dosimeter for synchrotron radiation fields.

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“…The flexibility makes organic film based electronic devices superior over its inorganic counter parts. For flexible device applications such as power sources [74,75], displays [76], electronics [77], super capacitors [78], gas sensors [79][80][81], thermoelectric power generators [82,83], organic light emitting diodes [84,85], radiation dosimeters [86][87][88] etc., organic semiconductors are promptly used. The nature of interaction between high energy EB and organic materials depends on the energy as well as dose of the incident EB [7].…”

Section: Organic Semiconductors and Its Interaction With Electron Beammentioning

confidence: 99%

Electron Beam Induced Tailoring of Electrical Characteristics of Organic Semiconductor Films

et al. 2020

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Tailoring the characteristics of organic semiconductors including molecular semiconductor and conducting polymers is the frontline area of research for improving the performance of organic electronic devices. Electron beam treatment has been established as one of the easiest method in comparison to others like chemical doping, thermal processing, ozonolysis, UV and other ionizing radiation treatment, to tune the physico-chemical properties of organic semiconductors. High energy electron beam (EB) generated from an accelerators impinges energy to the material and causes several phenomena including doping, crosslinking, chain degradation, gas evolution, molecular structural modifications, oxidation and unsaturation. Such modifications lead to variation in electrical characteristics and consequently affect the overall device performances. In the present review we have focused on the different interaction processes of EB with organic semiconductors and its implications to tailor the performance of device comprising of it mainly gas sensors, field effect transistors, thermoelectric power generators and radiation dosimeters.

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Characterization of a plastic dosimeter based on organic semiconductor photodiodes and scintillator

Cited by 14 publications

References 19 publications

Boron-Loaded Polymeric Sensor for the Direct Detection of Thermal Neutrons

Boron-Loaded Polymeric Sensor for the Direct Detection of Thermal Neutrons

Towards high spatial resolution tissue-equivalent dosimetry for microbeam radiation therapy using organic semiconductors

Electron Beam Induced Tailoring of Electrical Characteristics of Organic Semiconductor Films

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