The Experts below are selected from a list of 42 Experts worldwide ranked by ideXlab platform

T Suwada - One of the best experts on this subject based on the ideXlab platform.

  • design manufacture and operation of the Beam Spoiler for positron target protection
    IPAC 2014: Proceedings of the 5th International Particle Accelerator Conference, 2014
    Co-Authors: Lei Zang, K Kakihara, T Kamitani, K Mikawa, Fusashi Miyahara, T Suwada
    Abstract:

    In order to produce positrons, intensive pulsed electron Beam is used to strike on a tungsten target. The energy deposition is distributed non-uniformly over the target, leading to a mechanical stress. As a result of large thermal gradient, the target could be potentially damaged. To avoid the target destruction, the peak energy deposition density (PEDD) in the target should be well below the critical limit (35J/g) based on the SLAC operational experience. With an expected primary electron spot size on the target of SuperKEKB positron source, the PEDD will exceeds the limit. We will introduce a Beam Spoiler to enlarge the spot size by multiple scattering in thin Beam screen and aluminum plate. ItreducesthePEDDdowntohalfofthelimit. Thispaperdescribes the design of the Spoiler and the Beam screen system used in the positron Beam commissioning of SuperKEKB positron source started in 2014.

Lei Zang - One of the best experts on this subject based on the ideXlab platform.

  • design manufacture and operation of the Beam Spoiler for positron target protection
    IPAC 2014: Proceedings of the 5th International Particle Accelerator Conference, 2014
    Co-Authors: Lei Zang, K Kakihara, T Kamitani, K Mikawa, Fusashi Miyahara, T Suwada
    Abstract:

    In order to produce positrons, intensive pulsed electron Beam is used to strike on a tungsten target. The energy deposition is distributed non-uniformly over the target, leading to a mechanical stress. As a result of large thermal gradient, the target could be potentially damaged. To avoid the target destruction, the peak energy deposition density (PEDD) in the target should be well below the critical limit (35J/g) based on the SLAC operational experience. With an expected primary electron spot size on the target of SuperKEKB positron source, the PEDD will exceeds the limit. We will introduce a Beam Spoiler to enlarge the spot size by multiple scattering in thin Beam screen and aluminum plate. ItreducesthePEDDdowntohalfofthelimit. Thispaperdescribes the design of the Spoiler and the Beam screen system used in the positron Beam commissioning of SuperKEKB positron source started in 2014.

  • superkekb positron source target protection scheme
    2013
    Co-Authors: Lei Zang, T Kamitani
    Abstract:

    The SuperKEKB requires an intense Beam with a large number of positrons, which is generated by a high energy electron Beam strike on a solid tungsten target. The pulsed electron Beam distributed the energy non-uniformly over the target. In that case, a mechanical stress appears due to the large thermal gradient during each pulse, which could potentially destroy the target. Based on the analysis of the SLAC damaged target, peak energy deposition density (PEDD) should not exceed 35J/g to ensure a long term of safe operation. One way of reducing PEDD is increasing the Beam spot size. Hence we proposed a target protection scheme, in which a Beam Spoiler is placed upstream of a generation target. The aim is to maintain the generation targets PEDD below 35J/g even with a very small size primary electron Beam. In this paper, we will introduce graphite, aluminum and copper as the protection target material candidates. And also present the PEDD and positron yield evaluation as a function of various parameters such as protection target thickness and drift space.

T Kamitani - One of the best experts on this subject based on the ideXlab platform.

  • design manufacture and operation of the Beam Spoiler for positron target protection
    IPAC 2014: Proceedings of the 5th International Particle Accelerator Conference, 2014
    Co-Authors: Lei Zang, K Kakihara, T Kamitani, K Mikawa, Fusashi Miyahara, T Suwada
    Abstract:

    In order to produce positrons, intensive pulsed electron Beam is used to strike on a tungsten target. The energy deposition is distributed non-uniformly over the target, leading to a mechanical stress. As a result of large thermal gradient, the target could be potentially damaged. To avoid the target destruction, the peak energy deposition density (PEDD) in the target should be well below the critical limit (35J/g) based on the SLAC operational experience. With an expected primary electron spot size on the target of SuperKEKB positron source, the PEDD will exceeds the limit. We will introduce a Beam Spoiler to enlarge the spot size by multiple scattering in thin Beam screen and aluminum plate. ItreducesthePEDDdowntohalfofthelimit. Thispaperdescribes the design of the Spoiler and the Beam screen system used in the positron Beam commissioning of SuperKEKB positron source started in 2014.

  • superkekb positron source target protection scheme
    2013
    Co-Authors: Lei Zang, T Kamitani
    Abstract:

    The SuperKEKB requires an intense Beam with a large number of positrons, which is generated by a high energy electron Beam strike on a solid tungsten target. The pulsed electron Beam distributed the energy non-uniformly over the target. In that case, a mechanical stress appears due to the large thermal gradient during each pulse, which could potentially destroy the target. Based on the analysis of the SLAC damaged target, peak energy deposition density (PEDD) should not exceed 35J/g to ensure a long term of safe operation. One way of reducing PEDD is increasing the Beam spot size. Hence we proposed a target protection scheme, in which a Beam Spoiler is placed upstream of a generation target. The aim is to maintain the generation targets PEDD below 35J/g even with a very small size primary electron Beam. In this paper, we will introduce graphite, aluminum and copper as the protection target material candidates. And also present the PEDD and positron yield evaluation as a function of various parameters such as protection target thickness and drift space.

W Xiong - One of the best experts on this subject based on the ideXlab platform.

  • su ff t 276 is it still necessary to use a Beam Spoiler for breast radiation
    Medical Physics, 2007
    Co-Authors: L Jin, W Xiong
    Abstract:

    Purpose: The aim of this study is to find out whether it is still necessary to use a Beam Spoiler for breast treatment especially with IMRT technique. Materials and methods: Full Monte Carlo simulations were performed with and without a Beam Spoiler for 11 breast patients treated using 10MV photon Beams and another 10 patients using 18MV photon Beams with IMRT technique employed. CTV was defined as the breast volume which started from 5mm away of the skin and the build‐up‐region was defined from 2mm to 5mm depth from skin.Doses to CTV, build‐up‐region, skin and contralateral breast were compared with and without a Beam Spoiler. Results: Comparison of dose distributions show that the Beam Spoiler increases dose at the build‐up‐region where the patient surface is perpendicular to the Beam and thus improves the dose homogeneity inside the breast. After the dose distributions were normalized to ensure 95% volume of CTV receives at least 95% of the prescription dose, the difference on the minimum and maximum dose of CTV is 100% by using a Beam Spoiler. Conclusions: The Monte Carlo simulation results show that the Beam Spoiler can improve dose homogeneity in the breast. But it is not clinical significant especially when the IMRT technique is used to limit the dose heterogeneity. And thus it is suggested that a Beam Spoiler may not be necessary when breast patient is treated using two opposite tangential 10MV or 18MV Beams if the build‐up‐region is not a big concern.

H Amols - One of the best experts on this subject based on the ideXlab platform.

  • radiation therapy of large intact breasts using a Beam Spoiler or photons with mixed energies
    Medical Dosimetry, 2007
    Co-Authors: E Lief, Margie Hunt, L Hong, H Amols
    Abstract:

    Abstract Radiation treatment of large intact breasts with separations of more than 24 cm is typically performed using x-rays with energies of 10 MV and higher, to eliminate high-dose regions in tissue. The disadvantage of the higher energy Beams is the reduced dose to superficial tissue in the buildup region. We evaluated 2 methods of avoiding this underdosage: (1) a Beam Spoiler: 1.7-cm-thick Lucite plate positioned in the blocking tray 35 cm from the isocenter, with 15-MV x-rays; and (2) combining 6- and 15-MV x-rays through the same portal. For the Beam with the Spoiler, we measured the dose distribution for normal and oblique incidence using a film and ion chamber in polystyrene, as well as a scanning diode in a water tank. In the mixed-energy approach, we calculated the dose distributions in the buildup region for different proportions of 6- and 15-MV Beams. The dose enhancement due to the Beam Spoiler exhibited significant dependence upon the source-to-skin distance (SSD), field size, and the angle of incidence. In the center of a 20 × 20-cm 2 field at 90-cm SSD, the Beam Spoiler raises the dose at 5-mm depth from 77% to 87% of the prescription, while maintaining the skin dose below 57%. Comparison of calculated dose with measurements suggested a practical way of treatment planning with the Spoiler—usage of 2-mm “Beam” bolus—a special option offered by in-house treatment planning system. A second method of increasing buildup doses is to mix 6- and 15-MV Beams. For example, in the case of a parallel-opposed irradiation of a 27-cm-thick phantom, dose to D max for each energy, with respect to midplane, is 114% for pure 6-, 107% for 15-MV Beam with the Spoiler, and 108% for a 3:1 mixture of 15- and 6-MV Beams. Both methods are practical for radiation therapy of large intact breasts.

  • xrt of large intact breasts using mixed energy Beams and or a Beam Spoiler
    International Conference of the IEEE Engineering in Medicine and Biology Society, 2000
    Co-Authors: E Lief, Thomas Losasso, Margie Hunt, L Hong, H Amols
    Abstract:

    Breasts with separations over 24 cm are often treated with external Beam with energies of 10 MV and higher, in order to reduce the magnitude of the hot spots. The disadvantage of the higher energy Beams is the reduced dose to superficial breast tissue in the buildup region. The authors evaluated 2 methods for avoiding this underdosage: 1) a Beam Spoiler with 15 MV X-rays and 2) combining 6 MV and 15 MV X-rays. For the Beam Spoiler, a 1.7 cm thick slab of PMMA positioned at 35 cm from isocenter, the authors measured the dose distribution in the build-up region using film in a polystyrene phantom and an ion chamber in a water tank. For the mixed Beam, the authors calculated the dose distributions in the buildup region for different proportions of 6 MV and 15 MV photons. Both methods are practical for radiation therapy of large intact breasts.