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Aswin L. Hoffmann - One of the best experts on this subject based on the ideXlab platform.
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technical note experimental verification of magnetic field induced Beam Deflection and bragg peak displacement for mr integrated proton therapy
Medical Physics, 2018Co-Authors: Sonja M Schellhammer, S. Gantz, Armin Lühr, Bradley M Oborn, Michael Bussmann, Aswin L. HoffmannAbstract:PURPOSE Given its sensitivity to anatomical variations, proton therapy is expected to benefit greatly from integration with magnetic resonance imaging for online anatomy monitoring during irradiation. Such an integration raises several challenges, as both systems mutually interact. The proton Beam will experience quasi-continuous energy loss and energy-dependent electromagnetic Deflection at the same time, giving rise to a deflected Beam trajectory and an altered dose distribution with a displaced Bragg peak. So far, these effects have only been predicted using Monte Carlo and analytical models, but no clear consensus has been reached and experimental benchmark data are lacking. We measured proton Beam trajectories and Bragg peak displacement in a homogeneous phantom placed inside a magnetic field and compared them to simulations. METHODS Planar dose distributions of proton pencil Beams (80-180 MeV) traversing the field of a 0.95 T NdFeB permanent magnet while depositing energy in a PMMA slab phantom were measured using EBT3 radiochromic films and simulated using the Geant4 toolkit. Deflected Beam trajectories and the Bragg peak displacement were extracted from the measured planar dose distributions and compared against the simulations. RESULTS The lateral Beam Deflection was clearly visible on the EBT3 films and ranged from 1 to 10 mm for 80 to 180 MeV, respectively. Simulated and measured Beam trajectories and Bragg peak displacement agreed within 0.8 mm for all studied proton energies. CONCLUSIONS These results prove that the magnetic field-induced Bragg peak displacement is both measurable and accurately predictable in a homogeneous phantom at 0.95 T, and allows Monte Carlo simulations to be used as gold standard for proton Beam trajectory prediction in similar frameworks for MR-integrated proton therapy.
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prediction and compensation of magnetic Beam Deflection in mr integrated proton therapy a method optimized regarding accuracy versatility and speed
Physics in Medicine and Biology, 2017Co-Authors: Sonja M Schellhammer, Aswin L. HoffmannAbstract:The integration of magnetic resonance imaging (MRI) and proton therapy for on-line image-guidance is expected to reduce dose delivery uncertainties during treatment. Yet, the proton Beam experiences a Lorentz force induced Deflection inside the magnetic field of the MRI scanner, and several methods have been proposed to quantify this effect. We analyze their structural differences and compare results of both analytical and Monte Carlo models. We find that existing analytical models are limited in accuracy and applicability due to critical approximations, especially including the assumption of a uniform magnetic field. As Monte Carlo simulations are too time-consuming for routine treatment planning and on-line plan adaption, we introduce a new method to quantify and correct for the Beam Deflection, which is optimized regarding accuracy, versatility and speed. We use it to predict the trajectory of a mono-energetic proton Beam of energy E 0 traversing a water phantom behind an air gap within an omnipresent uniform transverse magnetic flux density B 0. The magnetic field induced dislocation of the Bragg peak is calculated as function of E 0 and B 0 and compared to results obtained with existing analytical and Monte Carlo methods. The deviation from the Bragg peak position predicted by Monte Carlo simulations is smaller for the new model than for the analytical models by up to 2 cm. The model is faster than Monte Carlo methods, less assumptive than the analytical models and applicable to realistic magnetic fields. To compensate for the predicted Bragg peak dislocation, a numerical optimization strategy is introduced and evaluated. It includes an adjustment of both the proton Beam entrance angle and energy of up to 25° and 5 MeV, depending on E 0 and B 0. This strategy is shown to effectively reposition the Bragg peak to its intended location in the presence of a magnetic field.
Hirofumi Yamada - One of the best experts on this subject based on the ideXlab platform.
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twin probe atomic force microscopy with optical Beam Deflection using vertically incident lasers by two Beam splitter
Electronics and Communications in Japan, 2016Co-Authors: Kei Kobayashi, Kazumi Matsushige, Nobuo Satoh, Eika Tsunemi, Takashi Komatsubara, Seiji Higuchi, Hirofumi YamadaAbstract:We developed a twin-probe atomic force microscopy AFM system using Si cantilever-probes. The system utilizes the optical Beam Deflection method in order to detect the Deflection of each cantilever-probe mounted on each tube-type actuator. The cantilever-probes mounted on each actuator are able to realize independent control of the probe positions, which are attached to manual sliders. A sensitivity 90 fm/Hz or less is achieved for the displacement sensor activity for the two cantilever-probes. We succeeded in the simultaneous observation of a topographic image in the state in which they approached each other to within 40 µm.
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development of multi environment dual probe atomic force microscopy system using optical Beam Deflection sensors with vertically incident laser Beams
Review of Scientific Instruments, 2013Co-Authors: Eika Tsunemi, Kei Kobayashi, Kazumi Matsushige, Noriaki Oyabu, Masaharu Hirose, Yoshiko Takenaka, Hirofumi YamadaAbstract:We developed a dual-probe atomic force microscopy (DP-AFM) system with two cantilever probes that can be operated in various environments such as in air, vacuum, and liquid. The system employs the optical Beam Deflection method for measuring the Deflection of each cantilever mounted on a probe scanner. The cantilever probes mounted on the probe scanners are attached to inertia sliders, which allow independent control of the probe positions. We constructed three types of probe scanners (tube, shear-piezo, and tripod types) and characterized their performance. We demonstrated AFM imaging in ambient air, vacuum, and ultrapure water, and also performed electrical measurement and pick-up manipulation of a Au nanorod using the DP-AFM system.
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development of dual probe atomic force microscopy system using optical Beam Deflection sensors with obliquely incident laser Beams
Review of Scientific Instruments, 2011Co-Authors: Eika Tsunemi, Kei Kobayashi, Kazumi Matsushige, Hirofumi YamadaAbstract:We developed a dual-probe (DP) atomic force microscopy (AFM) system that has two independently controlled probes. The Deflection of each cantilever is measured by the optical Beam Deflection (OBD) method. In order to keep a large space over the two probes for an objective lens with a large numerical aperture, we employed the OBD sensors with obliquely incident laser Beams. In this paper, we describe the details of our developed DP-AFM system, including analysis of the sensitivity of the OBD sensor for detection of the cantilever Deflection. We also describe a method to eliminate the crosstalk caused by the vertical translation of the cantilever. In addition, we demonstrate simultaneous topographic imaging of a test sample by the two probes and surface potential measurement on an α-sexithiophene (α-6T) thin film by one probe while electrical charges were injected by the other probe.
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frequency modulation atomic force microscopy at high cantilever resonance frequencies using the heterodyne optical Beam Deflection method
Review of Scientific Instruments, 2005Co-Authors: Takeshi Fukuma, Kenjiro Kimura, Kei Kobayashi, Kazumi Matsushige, Hirofumi YamadaAbstract:We have developed a frequency-modulation atomic force microscope (FM-AFM) with a wideband cantilever Deflection sensor using the heterodyne optical Beam Deflection method. The method enhances the bandwidth of the Deflection measurement up to the maximum frequency for the laser power modulation, which can be as high as gigahertz order. The phase and frequency of the cantilever vibration at 5.24MHz are detected with a Deflection noise density of 100fm∕Hz. FM-AFM imaging is performed on a Au(111) surface with a high-frequency cantilever.
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dynamic force microscopy at high cantilever resonance frequencies using heterodyne optical Beam Deflection method
Applied Physics Letters, 2004Co-Authors: Takeshi Fukuma, Kenjiro Kimura, Kei Kobayashi, Kazumi Matsushige, Hirofumi YamadaAbstract:We have developed a dynamic force microscope (DFM) with a wideband cantilever Deflection sensor using heterodyne optical Beam Deflection (HOBD) method. The bandwidth of HOBD method is limited only by the maximum frequency for laser power modulation, which can be as high as gigahertz order. This technique allows us to use high cantilever resonance frequencies for improving the sensitivity and time response of DFM. In this letter, basic principle and experimental setup of HOBD method are described. Deflection measurement of a cantilever vibration at about 7MHz is demonstrated. Using this cantilever, DFM imaging with a relatively fast scanning speed is performed.
W Kohler - One of the best experts on this subject based on the ideXlab platform.
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measurement of diffusion and thermal diffusion in ternary fluid mixtures using a two color optical Beam Deflection technique
Journal of Chemical Physics, 2010Co-Authors: A Koniger, H Wunderlich, W KohlerAbstract:We have developed a highly sensitive two-color Beam Deflection setup to measure diffusion and thermal diffusion in ternary fluid mixtures following a suggestion of Haugen and Firoozabadi [J. Phys. Chem. B 110, 17678 (2006)]. Simultaneous detection of two laser Beams with different wavelengths makes it possible to determine the time dependent concentration profiles of all three components. By comparing the measured Beam Deflection signals to a numerical solution of the coupled heat and mass transport equations, the diffusion matrix, the thermal diffusion, and the Soret coefficients are obtained by a numerical model combined with a nonlinear least-squares fitting routine. The results can be improved by additional thermal diffusion forced Rayleigh scattering experiments, which yield a contrast-weighted average thermal diffusion coefficient. The three Soret coefficients can be obtained independently from the stationary Beam Deflection amplitudes. Measurements have been performed on the symmetric (equal weight...
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measurement of diffusion and thermal diffusion in ternary fluid mixtures using a two color optical Beam Deflection technique
Journal of Chemical Physics, 2010Co-Authors: A Koniger, H Wunderlich, W KohlerAbstract:We have developed a highly sensitive two-color Beam Deflection setup to measure diffusion and thermal diffusion in ternary fluid mixtures following a suggestion of Haugen and Firoozabadi [J. Phys. Chem. B 110, 17678 (2006)]. Simultaneous detection of two laser Beams with different wavelengths makes it possible to determine the time dependent concentration profiles of all three components. By comparing the measured Beam Deflection signals to a numerical solution of the coupled heat and mass transport equations, the diffusion matrix, the thermal diffusion, and the Soret coefficients are obtained by a numerical model combined with a nonlinear least-squares fitting routine. The results can be improved by additional thermal diffusion forced Rayleigh scattering experiments, which yield a contrast-weighted average thermal diffusion coefficient. The three Soret coefficients can be obtained independently from the stationary Beam Deflection amplitudes. Measurements have been performed on the symmetric (equal weight fractions) ternary mixtures dodecane/isobutylbenzene/1,2,3,4-tetrahydronaphthalene and 1-methylnaphthalene/octane/decane. There is only partial agreement between our results and literature data.
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measurement of the soret diffusion and thermal diffusion coefficients of three binary organic benchmark mixtures and of ethanol water mixtures using a Beam Deflection technique
Philosophical Magazine, 2009Co-Authors: A Koniger, B Meier, W KohlerAbstract:We have measured the Soret (S T ), diffusion (D), and thermal diffusion (D T ) coefficients of three binary mixtures of dodecane (DD), isobutylbenzene (IB) and 1,2,3,4-tetrahydronaphthalene (TH) for a concentration of 50 wt% at a temperature of 25°C by means of an optical Beam Deflection cell. This relevant experimental technique was still missing from a recent benchmark campaign for the measurement of the Soret effect. The measured coefficients agree to within a few percent (10% for S T , D of TH/IB) with the proposed benchmark values. A detailed analysis of the measurement process of the Beam Deflection cell, which allows for an elegant extension to include temperature gradients within the windows, is given, and improved benchmark values are suggested. In addition, ethanol–water mixtures have been investigated very carefully over a broad concentration and temperature range. Comparison with data of Kolodner and Wiegand gives a generally good agreement with some systematic deviations. Contrary to theoreti...
Mladen Franko - One of the best experts on this subject based on the ideXlab platform.
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photothermal Beam Deflection spectroscopy for the determination of thermal diffusivity of soils and soil aggregates
International Journal of Thermophysics, 2018Co-Authors: M A Proskurnin, Dorota Korte, Olga Rogova, D S Volkov, Mladen FrankoAbstract:Photothermal Beam Deflection spectroscopy (BDS) with a red He–Ne laser (632.8 nm, 35 mW) as an excitation Beam source and a green He–Ne laser (543.1 nm, 2 mW) as a probe was used for estimating thermal diffusivity of several types of soil samples and individual soil aggregates with small surfaces (2 × 2 mm). It is shown that BDS can be used on demand for studies of changes in properties of soil entities of different hierarchical levels under the action of agrogenesis. It is presented that BDS clearly distinguishes between thermal diffusivities of different soil types: Sod-podzolic [Umbric Albeluvisols, Abruptic], 29 ± 3; Chernozem typical [Voronic Chernozems, Pachic], 9.9 ± 0.9; and Light Chestnut [Haplic Kastanozems, Chromic], 9.7 ± 0.9 cm2·h−1. Aggregates of chernozem soil show a significantly higher thermal diffusivity compared to the bulk soil. Thermal diffusivities of aggregates of Chernozem for virgin and bare fallow samples differ, 53 ± 4 cm2·h−1 and 45 ± 4 cm2·h−1, respectively. Micromonoliths of different Sod-podzolic soil horizons within the same profile (topsoil, depth 10–14 cm, and a parent rock with Fe illuviation, depth 180–185 cm) also show a significant difference, thermal diffusivities are 9.5 ± 0.8 cm2·h−1 and 27 ± 2 cm2·h−1, respectively. For soil micromonoliths, BDS is capable to distinguish the difference in thermal diffusivity resulting from the changes in the structure of aggregates.
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optimized frequency dependent photothermal Beam Deflection spectroscopy
Laser Physics Letters, 2016Co-Authors: Dorota Korte, Humberto Cabrera, J Toro, P Grima, C Leal, A Villabona, Mladen FrankoAbstract:In the letter the optimization of the experimental setup for photothermal Beam Deflection spectroscopy is performed by analyzing the influence of its geometrical parameters (detector and sample position, probe Beam radius and its waist position etc) on the detected signal. Furthermore, the effects of the fluid's thermo-optical properties, for optimized geometrical configuration, on the measurement sensitivity and uncertainty determination of sample thermal properties is also studied. The examined sample is a recently developed CuFeInTe3 material. It is seen from the obtained results, that it is a complex problem to choose the proper geometrical configuration as well as sensing fluid to enhance the sensitivity of the method. A signal enhancement is observed at low modulation frequencies by placing the sample in acetonitrile (ACN), while at high modulation frequencies the sensitivity is higher for measurements made in air. For both, detection in air and acetonitrile the determination of CuFeInTe3 thermal properties is performed. The determined values of thermal diffusivity and thermal conductivity are (0.048 ± 0.002) × 10−4 m2 s−1 and 4.6 ± 0.2 W m−1 K−1 and (0.056 ± 0.005) × 10−4 m2 s−1 and 4.8 ± 0.4 W m−1 K−1 for ACN and air, respectively. It is seen, that the determined values agree well within the range of their measurement uncertainties for both cases, although the measurement uncertainty is two times lower for the measurements in ACN providing more accurate results. The analysis is performed by the use of recently developed theoretical description based on the complex geometrical optics. It is also shown, how the presented work fits into the current status of photothermal Beam Deflection spectroscopy.
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Determination of thermooptical and transport parameters of ε iron(III) oxide-based nanocomposites by Beam Deflection spectroscopy
'Elsevier BV', 2015Co-Authors: Dorota Korte, Carraro Giorgio, Maccato Chiara, Mladen FrankoAbstract:In this work, photothermal Beam Deflection (PBD) experiments have been used to characterize the thermooptical and transport properties of \u3b5-Fe2O3-based nanocomposites. In particular, iron(III) nanostructures have been functionalized with Au, Ag and Cu nanoparticles, tailoring both their nano-organization and their chemical state. In order to elucidate the correlation between the thermooptical and transport parameters, the structural, compositional and morphological properties of Fe2O3-based systems were studied by field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). It was observed that the optothermal and transport parameters were influenced by the nature and oxidation state of the nanoparticles, which can serve as a key tool to master the material properties for their application in light-assisted processes
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application of complex geometrical optics to determination of thermal transport and optical parameters of thin films by the photothermal Beam Deflection technique
Journal of The Optical Society of America A-optics Image Science and Vision, 2015Co-Authors: Dorota Korte, Mladen FrankoAbstract:In this work, complex geometrical optics is, for what we believe is the first time, applied instead of geometrical or wave optics to describe the probe Beam interaction with the field of the thermal wave in photothermal Beam Deflection (photothermal Deflection spectroscopy) experiments on thin films. On the basis of this approach the thermal (thermal diffusivity and conductivity), optical (energy band gap), and transport (carrier lifetime) parameters of the semiconductor thin films (pure TiO2, N- and C-doped TiO2, or TiO2/SiO2 composites deposited on a glass or aluminum support) were determined with better accuracy and simultaneously during one measurement. The results are in good agreement with results obtained by the use of other methods and reported in the literature.
Takeshi Fukuma - One of the best experts on this subject based on the ideXlab platform.
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wideband low noise optical Beam Deflection sensor with photothermal excitation for liquid environment atomic force microscopy
Review of Scientific Instruments, 2009Co-Authors: Takeshi FukumaAbstract:I developed a wideband low-noise optical Beam Deflection sensor with a photothermal cantilever excitation system for liquid-environment atomic force microscopy. The developed sensor has a 10 MHz bandwidth and 4.7 fm/Hz Deflection noise density in water. The theoretically limited noise performance (i.e., the noise level limited only by the photodiode shot noise) has been achieved in liquid for the first time. Owing to the wide bandwidth and the replaceable focus lens design, the sensor is applicable to cantilevers with various dimensions. The Deflection noise densities of less than 7.8 fm/Hz have been achieved in water for cantilevers with lengths from 35 to 125 μm. The ideal amplitude and phase versus frequency curves without distortion are obtained with the developed photothermal excitation system. The excitation system is applicable to relatively stiff cantilevers (>20 N/m) in liquid, making it possible to obtain true atomic-resolution images in liquid. True atomic-resolution imaging of mica in water is...
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frequency modulation atomic force microscopy at high cantilever resonance frequencies using the heterodyne optical Beam Deflection method
Review of Scientific Instruments, 2005Co-Authors: Takeshi Fukuma, Kenjiro Kimura, Kei Kobayashi, Kazumi Matsushige, Hirofumi YamadaAbstract:We have developed a frequency-modulation atomic force microscope (FM-AFM) with a wideband cantilever Deflection sensor using the heterodyne optical Beam Deflection method. The method enhances the bandwidth of the Deflection measurement up to the maximum frequency for the laser power modulation, which can be as high as gigahertz order. The phase and frequency of the cantilever vibration at 5.24MHz are detected with a Deflection noise density of 100fm∕Hz. FM-AFM imaging is performed on a Au(111) surface with a high-frequency cantilever.
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dynamic force microscopy at high cantilever resonance frequencies using heterodyne optical Beam Deflection method
Applied Physics Letters, 2004Co-Authors: Takeshi Fukuma, Kenjiro Kimura, Kei Kobayashi, Kazumi Matsushige, Hirofumi YamadaAbstract:We have developed a dynamic force microscope (DFM) with a wideband cantilever Deflection sensor using heterodyne optical Beam Deflection (HOBD) method. The bandwidth of HOBD method is limited only by the maximum frequency for laser power modulation, which can be as high as gigahertz order. This technique allows us to use high cantilever resonance frequencies for improving the sensitivity and time response of DFM. In this letter, basic principle and experimental setup of HOBD method are described. Deflection measurement of a cantilever vibration at about 7MHz is demonstrated. Using this cantilever, DFM imaging with a relatively fast scanning speed is performed.