Signal enhancement due to high‐Z nanofilm electrodes in parallel plate ionization chambers with variable microgaps

Brivio, Davide; Sajo, Erno; Zygmanski, Piotr

doi:10.1002/mp.12636

Cited by 2 publications

(1 citation statement)

References 40 publications

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“…A full understanding of this behavior requires further investigation. In this manuscript we simply note that the contribution of ionization to the signal is negligible (about 60 times smaller) if compared to a parallel plate ionization chamber with the same thickness [34] and we will focus on the signal formation for null external potential when ionization is not collected.…”

Section: Iv-characteristic Curvementioning

confidence: 99%

Nanoporous aerogel-based periodic high-energy electron current x-ray sensors

Brivio

Albert

Gagne

et al. 2020

J. Phys. D: Appl. Phys.

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We developed a novel platform of self-powered radiation sensors based on high-energy electron currents in multi-layer thin-film geometry. A periodic structure of N elemental modules consisting of (high-Z electrode/nano-porous aerogel/low-Z electrode) layers was investigated. 10 and 50 μm thick high-Z (Cu, Ta) and low-Z (Al) electrodes were separated by 50 μm thick polyimide aerogel insulating films. Sensors were tested with 120 kV, 2.5 MV and 6 MV x-rays. The sensors’ characteristics were investigated by obtaining current-voltage (IV) curves for different low-Z/high-Z electrode combinations. Experimentally measured currents from each electrode were compared to radiation transport simulations using the CEPXS/ONEDANT computer model with nanometer-to-micrometer spatial resolution. The main features of the IV-curves are: (a) non-zero current at zero external voltage bias (b) S-like shape at small voltages, and (c) a linear increase of current dominant at large voltages. Signals scale with the total effective area of all electrodes, as well as the number of electrodes and their thicknesses. The yield of a multi-element sensor made with N = 10 elemental modules (10 μm-thick Ta) compared to a single N = 1 (double N = 2) elemental module (made with 50 μm-thick Ta layers) reveals an increase of the total signal of about 4.3 (2.9) times for 6 MV beam and 8.2 (5.8) times for 120kVp. Beam attenuation in the detector is about 0.5%, 3% and 46% respectively for 6 MV, 2,5 MV and 120kVp beams per single elemental structure with 50 μm Ta. We investigated the characteristics of aerogel-based high-energy current x-ray detectors in multi-layered configurations. We envision its implementation for real-time monitoring of radiation dose/flux in areas of homeland security, interventional radiology and radiotherapy.

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Section: Iv-characteristic Curvementioning

confidence: 99%

Nanoporous aerogel-based periodic high-energy electron current x-ray sensors

Brivio

Albert

Gagne

et al. 2020

J. Phys. D: Appl. Phys.

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Toward a multi‐layer micro‐structured detector for high‐energy electron radiotherapy

Brivio,

Liles,

Gagne

et al. 2024

Medical Physics

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BackgroundThe use of electron beams has been rekindled by the advent of ultra‐high‐dose rate radiotherapy (FLASH) and very high energy electrons (VHEE). The need for development of novel technology for beam monitoring and dosimetry of such beams is of paramount importance prior to their clinical translation.PurposeIn this work we explore the potential of a multi‐layer nanoporous aerogel High‐Energy‐Current (HEC) detector as a dosimeter for electron beam. The detector does not suffer from radiation damage or signal saturation, making it suitable for very‐high‐dose‐rate applications. Standard dose rates and energies are used to establish reference for FLASH and VHEE. We explore detector response to electron energy and residual range both experimentally and computationally.MethodsMultilayer HEC detectors were constructed using 1×–10× basic modules of Aluminum(Al)_aerogel(A)_Tantalum(Ta) with 10–70 µm layer thicknesses. Signals are collected from all electrodes (3–21, depending on module multiplicity) with zero external voltage bias. Measurements are acquired as a function of depth(z) in water equivalent plastic using Varian TrueBeam for energies E = 6,9,12,15 MeV (SAD = 105 cm, 6 × 6 cone, 1000 MU/min). Computational simulations of identical detector geometries are performed using the 1D deterministic code CEPXS/ONEDANT. Additionally, percent‐depth‐doses PDD(z), measured with diode in water, are used to explore the response of HEC for various energies and residual ranges.ResultsThe current measured from Ta electrodes resembles the shape of deposited charges in water and it is proportional to the derivative of the clinical PDD corrected for contribution from photon contamination. The signal is positive on the surface, and it decreases with depth reaching a negative local minimum at z = R50, before increasing again, reaching zero at about the practical range z = Rp. In contrast, the signal from Al electrodes is shaped like the electron PDD(z) shape but with lower signal at the surface and higher bremsstrahlung tail. By subtracting the signal from Ta and Al electrodes we obtained a curve resembling PDD(z,E) after Bremsstrahlung contamination correction.ConclusionsMulti‐layer HEC sensors exhibit characteristic responses to electron beams that are unlike responses of ion chambers or diodes. Since the sensor structures are sensitive to electronic disequilibrium, high‐Z electrodes give a signal proportional to the charge deposition pattern and can be modeled using the derivative of PDD(z).

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Signal enhancement due to high‐Z nanofilm electrodes in parallel plate ionization chambers with variable microgaps

Cited by 2 publications

References 40 publications

Nanoporous aerogel-based periodic high-energy electron current x-ray sensors

Nanoporous aerogel-based periodic high-energy electron current x-ray sensors

Toward a multi‐layer micro‐structured detector for high‐energy electron radiotherapy

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