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C Goma - One of the best experts on this subject based on the ideXlab platform.

  • reference dosimetry of proton pencil beams based on dose area product a proof of concept
    Physics in Medicine and Biology, 2017
    Co-Authors: C Goma, S Safai, Sando Voros
    Abstract:

    This paper describes a novel approach to the reference dosimetry of proton pencil beams based on dose-area product (). It depicts the calibration of a large-diameter plane-parallel ionization chamber in terms of dose-area product in a 60Co beam, the Monte Carlo Calculation of beam quality correction factors—in terms of dose-area product—in proton beams, the Monte Carlo Calculation of nuclear halo correction factors, and the experimental determination of of a single proton pencil beam. This new approach to reference dosimetry proves to be feasible, as it yields values in agreement with the standard and well-established approach of determining the absorbed dose to water at the centre of a broad homogeneous field generated by the superposition of regularly-spaced proton pencil beams.

  • reference dosimetry of proton pencil beams based on dose area product a proof of concept
    Physics in Medicine and Biology, 2017
    Co-Authors: C Goma, S Safai, Sandor Voros
    Abstract:

    This paper describes a novel approach to the reference dosimetry of proton pencil beams based on dose-area product ([Formula: see text]). It depicts the calibration of a large-diameter plane-parallel ionization chamber in terms of dose-area product in a 60Co beam, the Monte Carlo Calculation of beam quality correction factors-in terms of dose-area product-in proton beams, the Monte Carlo Calculation of nuclear halo correction factors, and the experimental determination of [Formula: see text] of a single proton pencil beam. This new approach to reference dosimetry proves to be feasible, as it yields [Formula: see text] values in agreement with the standard and well-established approach of determining the absorbed dose to water at the centre of a broad homogeneous field generated by the superposition of regularly-spaced proton pencil beams.

  • Monte Carlo Calculation of beam quality correction factors in proton beams using detailed simulation of ionization chambers
    Physics in Medicine and Biology, 2016
    Co-Authors: C Goma, J Sempau
    Abstract:

    This work calculates beam quality correction factors (kQ) in monoenergetic proton beams using detailed Monte Carlo simulation of ionization chambers. It uses the Monte Carlo code penh and the electronic stopping powers resulting from the adoption of two different sets of mean excitation energy values for water and graphite: (i) the currently ICRU 37 and ICRU 49 recommended Iw = 75 eV and Ig = 78 eV and (ii) the recently proposed Iw = 78 eV and Ig = 81.1 eV. Twelve different ionization chambers were studied. The k Q factors calculated using the two different sets of I-values were found to agree with each other within 1.6% or better. k Q factors calculated using current ICRU I-values were found to agree within 2.3% or better with the k Q factors tabulated in IAEA TRS-398, and within 1% or better with experimental values published in the literature. k Q factors calculated using the new I-values were also found to agree within 1.1% or better with the experimental values. This work concludes that perturbation correction factors in proton beams--currently assumed to be equal to unity--are in fact significantly different from unity for some of the ionization chambers studied.

Sando Voros - One of the best experts on this subject based on the ideXlab platform.

  • reference dosimetry of proton pencil beams based on dose area product a proof of concept
    Physics in Medicine and Biology, 2017
    Co-Authors: C Goma, S Safai, Sando Voros
    Abstract:

    This paper describes a novel approach to the reference dosimetry of proton pencil beams based on dose-area product (). It depicts the calibration of a large-diameter plane-parallel ionization chamber in terms of dose-area product in a 60Co beam, the Monte Carlo Calculation of beam quality correction factors—in terms of dose-area product—in proton beams, the Monte Carlo Calculation of nuclear halo correction factors, and the experimental determination of of a single proton pencil beam. This new approach to reference dosimetry proves to be feasible, as it yields values in agreement with the standard and well-established approach of determining the absorbed dose to water at the centre of a broad homogeneous field generated by the superposition of regularly-spaced proton pencil beams.

Sandor Voros - One of the best experts on this subject based on the ideXlab platform.

  • reference dosimetry of proton pencil beams based on dose area product a proof of concept
    Physics in Medicine and Biology, 2017
    Co-Authors: C Goma, S Safai, Sandor Voros
    Abstract:

    This paper describes a novel approach to the reference dosimetry of proton pencil beams based on dose-area product ([Formula: see text]). It depicts the calibration of a large-diameter plane-parallel ionization chamber in terms of dose-area product in a 60Co beam, the Monte Carlo Calculation of beam quality correction factors-in terms of dose-area product-in proton beams, the Monte Carlo Calculation of nuclear halo correction factors, and the experimental determination of [Formula: see text] of a single proton pencil beam. This new approach to reference dosimetry proves to be feasible, as it yields [Formula: see text] values in agreement with the standard and well-established approach of determining the absorbed dose to water at the centre of a broad homogeneous field generated by the superposition of regularly-spaced proton pencil beams.

M S Shur - One of the best experts on this subject based on the ideXlab platform.

  • Monte Carlo Calculation of velocity field characteristics of wurtzite gan
    Journal of Applied Physics, 1997
    Co-Authors: Udayan V Bhapkar, M S Shur
    Abstract:

    We present velocity-field simulations of n-doped, wurtzite-phase GaN for temperatures between 77 and 1000 K using an ensemble Monte Carlo technique. A three-valley model of the band structure is assumed, and the ionized impurity, polar optical phonon, acoustic phonon, piezoelectric, and intervally scattering mechanisms are considered. Electron degeneracy and heating are also accounted for. Properties of the two dimensional electron gas in AlGaN/GaN heterostructures are also estimated by performing simulations on bulk GaN in which the electron concentration exceeds the ionized donor concentration by factors of ten to one hundred. The simulations predict that peak steady-state drift velocities ranging from 3.3×107 to 2.1×107 cm/s for temperatures between 77 and 1000 K can be achieved in both the two dimensional electron gas and in the bulk material with an ionized donor concentration of 1016 cm−3. Furthermore, the simulations predict that the two-dimensional electron gas in GaN will exhibit a low-field mobility an order of magnitude greater than the bulk material, in agreement with experimental results.

  • Monte Carlo Calculation of velocity field characteristics of wurtzite gan
    Journal of Applied Physics, 1997
    Co-Authors: Udayan V Bhapkar, M S Shur
    Abstract:

    We present velocity-field simulations of n-doped, wurtzite-phase GaN for temperatures between 77 and 1000 K using an ensemble Monte Carlo technique. A three-valley model of the band structure is assumed, and the ionized impurity, polar optical phonon, acoustic phonon, piezoelectric, and intervally scattering mechanisms are considered. Electron degeneracy and heating are also accounted for. Properties of the two dimensional electron gas in AlGaN/GaN heterostructures are also estimated by performing simulations on bulk GaN in which the electron concentration exceeds the ionized donor concentration by factors of ten to one hundred. The simulations predict that peak steady-state drift velocities ranging from 3.3×107 to 2.1×107 cm/s for temperatures between 77 and 1000 K can be achieved in both the two dimensional electron gas and in the bulk material with an ionized donor concentration of 1016 cm−3. Furthermore, the simulations predict that the two-dimensional electron gas in GaN will exhibit a low-field mobi...

  • Monte Carlo simulation of electron transport in gallium nitride
    Journal of Applied Physics, 1993
    Co-Authors: B Gelmont, Kisang Kim, M S Shur
    Abstract:

    The results of an ensemble Monte Carlo simulation of the electron transport in gallium nitride (GaN) are presented. The Calculation shows that intervalley electron transfer plays a dominant role in GaN in high electric fields leading to a strongly inverted electron distribution and to a large negative differential conductance. An analytic expression for the polar optical momentum relaxation time for phonon energies larger than the thermal energy is also derived. This expression applies to many wide‐gap semiconductors, such as GaN and SiC, at room temperature since these semiconductors have large polar optical‐phonon energies (on the order of 100 meV). The calculated mobility agrees well with the results of the Monte Carlo Calculation.

S Safai - One of the best experts on this subject based on the ideXlab platform.

  • reference dosimetry of proton pencil beams based on dose area product a proof of concept
    Physics in Medicine and Biology, 2017
    Co-Authors: C Goma, S Safai, Sando Voros
    Abstract:

    This paper describes a novel approach to the reference dosimetry of proton pencil beams based on dose-area product (). It depicts the calibration of a large-diameter plane-parallel ionization chamber in terms of dose-area product in a 60Co beam, the Monte Carlo Calculation of beam quality correction factors—in terms of dose-area product—in proton beams, the Monte Carlo Calculation of nuclear halo correction factors, and the experimental determination of of a single proton pencil beam. This new approach to reference dosimetry proves to be feasible, as it yields values in agreement with the standard and well-established approach of determining the absorbed dose to water at the centre of a broad homogeneous field generated by the superposition of regularly-spaced proton pencil beams.

  • reference dosimetry of proton pencil beams based on dose area product a proof of concept
    Physics in Medicine and Biology, 2017
    Co-Authors: C Goma, S Safai, Sandor Voros
    Abstract:

    This paper describes a novel approach to the reference dosimetry of proton pencil beams based on dose-area product ([Formula: see text]). It depicts the calibration of a large-diameter plane-parallel ionization chamber in terms of dose-area product in a 60Co beam, the Monte Carlo Calculation of beam quality correction factors-in terms of dose-area product-in proton beams, the Monte Carlo Calculation of nuclear halo correction factors, and the experimental determination of [Formula: see text] of a single proton pencil beam. This new approach to reference dosimetry proves to be feasible, as it yields [Formula: see text] values in agreement with the standard and well-established approach of determining the absorbed dose to water at the centre of a broad homogeneous field generated by the superposition of regularly-spaced proton pencil beams.