Thick CrN coatings were deposited on Si （111） substrates by electron source assisted mid-frequency magnetron sputtering working at 40 kHz. The deposition rate, structure, and microhardness of the coatings were stron...Thick CrN coatings were deposited on Si （111） substrates by electron source assisted mid-frequency magnetron sputtering working at 40 kHz. The deposition rate, structure, and microhardness of the coatings were strongly influenced by the negative bias voltage （Vb）. The deposition rate reached 8.96 μm/h at a Vb of -150 V. X-ray diffraction measurement revealed strong CrN （200） orientation for films prepared at low bias voltages. At a high bias voltage of Vb less than -25 V both CrN （200） and （111） were observed. Large and homogeneous grains were observed by both atomic force microscopy and scanning electron microscopy in samples prepared under optimal conditions. The samples exhibited a fibrous microstructure for a low bias voltage and a columnar structure for VD less than -150 V.展开更多
Objective:In this study,we try to establish an initial electron beam model by combining Monte Carlo simulation method with particle dynamic calculation(TRSV)for the single 6 MV X-ray accelerating waveguide of BJ-6 med...Objective:In this study,we try to establish an initial electron beam model by combining Monte Carlo simulation method with particle dynamic calculation(TRSV)for the single 6 MV X-ray accelerating waveguide of BJ-6 medical linac.Methods and Materials:1.We adapted the treatment head configuration of BJ-6 medical linac made by Beijing Medical Equipment Institute(BMEI)as the radiation system for this study.2.Use particle dynamics calculation code called TRSV to drive out the initial electron beam parameters of the energy spectrum,the spatial intensity distribution,and the beam incidence angle.3.Analyze the 6 MV X-ray beam characteristics of PDDc,OARc in a water phantom by using Monte Carlo simulation(BEAMnrc,DOSXYZnrc)for a preset of the initial electron beam parameters which have been determined by TRSV,do the comparisons of the measured results of PDDm,OARm in a real water phantom,and then use the deviations of calculated and measured results to slightly modify the initial electron beam model back and forth until the deviations meet the error less than 2%.Results:The deviations between the Monte Carlo simulation results of percentage depth doses at PDDc and off-axis ratios OARc and the measured results of PDDm and OARm in a water phantom were within 2%.Conclusion:When doing the Monte Carlo simulation to determine the parameters of an initial electron beam for a particular medical linac like BJ-6,modifying some parameters based on the particle dynamics calculation code would give some more reasonable and more acceptable results.展开更多
1 Mechanism of s-SNOM The concept of utilizing a near-field technique to circumvent the diffraction limit dates back to the early 20th century,proposed by Edward Synge[1].After the first demonstration of this idea,in ...1 Mechanism of s-SNOM The concept of utilizing a near-field technique to circumvent the diffraction limit dates back to the early 20th century,proposed by Edward Synge[1].After the first demonstration of this idea,in 1972 in microwaves[2]and 1984 in visible light[3,4],various practices with similar near-field approaches emerged.Hillenbrand et al.[5]recently reviewed scattering-type scanning near-field optical microscopy(s-SNOM)as a specific type of near-field scanning technique.The detection limit of this near-field scanning technique is characterized by the sharpness of the metallic tip,rather than the wavelength of the electromagnetic wave.Thus,the potential to scan with a very broad frequency range while maintaining an extremely high spatial resolution(nominally 10-100 nm)makes this proposal extremely promising.By analyzing the local dielectric constantϵ(x)as a function of scanning frequency and controlling other environmental parameters,a wealth of physical information can be extracted.展开更多
基金supported by National Natural Science Foundation of China(Nos.10435060,10675095)
文摘Thick CrN coatings were deposited on Si （111） substrates by electron source assisted mid-frequency magnetron sputtering working at 40 kHz. The deposition rate, structure, and microhardness of the coatings were strongly influenced by the negative bias voltage （Vb）. The deposition rate reached 8.96 μm/h at a Vb of -150 V. X-ray diffraction measurement revealed strong CrN （200） orientation for films prepared at low bias voltages. At a high bias voltage of Vb less than -25 V both CrN （200） and （111） were observed. Large and homogeneous grains were observed by both atomic force microscopy and scanning electron microscopy in samples prepared under optimal conditions. The samples exhibited a fibrous microstructure for a low bias voltage and a columnar structure for VD less than -150 V.
文摘Objective:In this study,we try to establish an initial electron beam model by combining Monte Carlo simulation method with particle dynamic calculation(TRSV)for the single 6 MV X-ray accelerating waveguide of BJ-6 medical linac.Methods and Materials:1.We adapted the treatment head configuration of BJ-6 medical linac made by Beijing Medical Equipment Institute(BMEI)as the radiation system for this study.2.Use particle dynamics calculation code called TRSV to drive out the initial electron beam parameters of the energy spectrum,the spatial intensity distribution,and the beam incidence angle.3.Analyze the 6 MV X-ray beam characteristics of PDDc,OARc in a water phantom by using Monte Carlo simulation(BEAMnrc,DOSXYZnrc)for a preset of the initial electron beam parameters which have been determined by TRSV,do the comparisons of the measured results of PDDm,OARm in a real water phantom,and then use the deviations of calculated and measured results to slightly modify the initial electron beam model back and forth until the deviations meet the error less than 2%.Results:The deviations between the Monte Carlo simulation results of percentage depth doses at PDDc and off-axis ratios OARc and the measured results of PDDm and OARm in a water phantom were within 2%.Conclusion:When doing the Monte Carlo simulation to determine the parameters of an initial electron beam for a particular medical linac like BJ-6,modifying some parameters based on the particle dynamics calculation code would give some more reasonable and more acceptable results.
文摘1 Mechanism of s-SNOM The concept of utilizing a near-field technique to circumvent the diffraction limit dates back to the early 20th century,proposed by Edward Synge[1].After the first demonstration of this idea,in 1972 in microwaves[2]and 1984 in visible light[3,4],various practices with similar near-field approaches emerged.Hillenbrand et al.[5]recently reviewed scattering-type scanning near-field optical microscopy(s-SNOM)as a specific type of near-field scanning technique.The detection limit of this near-field scanning technique is characterized by the sharpness of the metallic tip,rather than the wavelength of the electromagnetic wave.Thus,the potential to scan with a very broad frequency range while maintaining an extremely high spatial resolution(nominally 10-100 nm)makes this proposal extremely promising.By analyzing the local dielectric constantϵ(x)as a function of scanning frequency and controlling other environmental parameters,a wealth of physical information can be extracted.
