When we were studying the vacuum switch,we found that the vacuum diode can radiate a broadband microwave.The vacuum diode is comprised of a cathode with a trigger device and planar anode,there is not a metallic bellow...When we were studying the vacuum switch,we found that the vacuum diode can radiate a broadband microwave.The vacuum diode is comprised of a cathode with a trigger device and planar anode,there is not a metallic bellows waveguide structure in this device,so the radiation mechanism of the vacuum diode is different from the plasma filled microwave device.It is hard to completely imitate the theory of the plasma filled microwave device.This paper analyzes the breakdown process of the vacuum diode,establishes the mathematical model of the radiating microwave from the vacuum diode.Based on the analysis of the dispersion relation in the form of a refractive index,the electromagnetic waves generated in the vacuum diode will resonate.The included angle between the direction of the electromagnetic radiation and the initial motion direction of electron beam is 45 degrees.The paper isolates the electrostatic effect from the beam-plasma interaction when the electromagnetic radiation occurs.According to above analyses,the dispersion relations of radiation are obtained by solving the wave equation.The dispersion curves are also obtained based on the theoretical dispersion relations.The theoretical dispersion curves are consistent with the actual measurement time-frequency maps of the radiation.Theoretical deduction and experiments indicate that the reason for microwave radiating from the vacuum diode can be well explained by the interaction of the electron beam and magnetized plasma.展开更多
Pseudowaves, known as burst-ion signals, which are different from plasma normal modes, exist frequently in ion- wave excitation experiments when launching the waves by applying a pulsed voltage to a negatively biased ...Pseudowaves, known as burst-ion signals, which are different from plasma normal modes, exist frequently in ion- wave excitation experiments when launching the waves by applying a pulsed voltage to a negatively biased grid. In previous experiments, only one kind of the pseudowave was observed. In this paper, we report the observation and identification of double pseudowaves in an ion-beam-plasma system. These pseudowaves originate from two ion groups： the burst of the beam ions and the burst of the background ions. It was observed that the burst of the background ions was in the case of high ion beam energy, while the burst of the beam ions was in the case of low ion beam energy. By observing the dependence of the signal velocities on the characteristics of the excitation voltage, these pseudowaves can be identified. It was also observed that the burst ion signal originating from the background ions can interact with slow beam mode and that originating from the beam ions can interact with fast beam mode.展开更多
The stabilization effect of a strong HF electric field on beam-plasma instability in a cylindrical warm plasma waveguide is discussed. A mathematical technique “separation method” applied to the two-fluid plasma mod...The stabilization effect of a strong HF electric field on beam-plasma instability in a cylindrical warm plasma waveguide is discussed. A mathematical technique “separation method” applied to the two-fluid plasma model to separate the equations, which describe the system, into two parts, temporal and space parts. Plasma electrons are considered to have a thermal velocity. It is shown that a HF electric field has no essential influence on dispersion characteristics of unstable surface waves excited in a warm plasma waveguide by a low-density electron beam. The region of instability only slightly narrowing and the growth rate decreases by a small parameter and this result has been reduced compared to cold plasma. Also, it is found that the plasma electrons have not affected the solution of the space part of the problem.展开更多
偶极磁场约束等离子体特性及其与带电粒子束的相互作用研究是近地空间磁层等离子体研究领域关心的一类重要问题.本研究采用粒子模拟(particle in cell, PIC)方法,通过开源的Smilei程序,研究了电子束注入偶极磁场约束等离子体的三维动力...偶极磁场约束等离子体特性及其与带电粒子束的相互作用研究是近地空间磁层等离子体研究领域关心的一类重要问题.本研究采用粒子模拟(particle in cell, PIC)方法,通过开源的Smilei程序,研究了电子束注入偶极磁场约束等离子体的三维动力学演化行为.模拟了不同注入角度电子束对等离子体的影响,给出了电子束及等离子体的时空演化过程和行为解释.结果显示,偶极磁场中的等离子体沿磁场线形成“新月形”壳结构分布,壳中形成内外相反方向的环形电流.当电子束的注入角度与磁场方向的夹角过大(超过20°),且漂移速度方向未对准偶极场中心时,大多数电子束粒子将在偶极磁场中漂移,散射并弹出模拟区域,无法与偶极磁场约束的等离子体发生相互作用.未来我国的偶极磁场约束等离子体研究装置在开展电子束与等离子体相互作用的实验时,有必要选择适当的电子束入射方向,以确保电子束能够进入偶极磁场的核心区域并与原来约束的等离子体进行相互作用.同时模拟结果显示电子束注入会使得等离子体环形电流在环向上变得不均匀.本研究有助于深入了解偶极磁场中的等离子体动力学行为特性,对于保障我国空间等离子体研究装置完成预期科学目标具有实际价值.展开更多
目的:观察Plasma等离子束联合强脉冲光治疗面部烧伤瘢痕的疗效及对瘢痕评分、疼痛程度的影响。方法:本次研究为前瞻性研究,采用随机数字表法将茂名市人民医院2024年3月至2024年8月期间收治的92例面部烧伤瘢痕患者分为对照组(接受强脉冲...目的:观察Plasma等离子束联合强脉冲光治疗面部烧伤瘢痕的疗效及对瘢痕评分、疼痛程度的影响。方法:本次研究为前瞻性研究,采用随机数字表法将茂名市人民医院2024年3月至2024年8月期间收治的92例面部烧伤瘢痕患者分为对照组(接受强脉冲光治疗,46例)和研究组(对照组的基础上接受Plasma等离子束治疗,46例)。对比两组疗效、相关量表评分、瘢痕恢复情况和不良反应发生率。结果:和对照组治疗后相比,研究组的临床总有效率和中文版简易烧伤健康量表(chinese version of the simplified burn health scale, BSHS-B)评分更高,温哥华瘢痕量表(vancouver scar scale, VSS)、视觉模拟疼痛量表(visual analogue scale, VAS)评分和瘢痕厚度、瘢痕血流灌注量更低(P<0.05)。两组不良反应发生率组间对比未见差异(P>0.05)。结论:应用Plasma离子束联合强脉冲光治疗面部烧伤瘢痕患者,可提高临床疗效,改善瘢痕厚度和血流灌注量,缓解瘢痕瘙痒及疼痛程度,安全性较好。展开更多
基金Supported by National Nature Science Foundation of China(No.11075123)the Young Scientists Fund of Nature Science Foundation of China(No.51207171)
文摘When we were studying the vacuum switch,we found that the vacuum diode can radiate a broadband microwave.The vacuum diode is comprised of a cathode with a trigger device and planar anode,there is not a metallic bellows waveguide structure in this device,so the radiation mechanism of the vacuum diode is different from the plasma filled microwave device.It is hard to completely imitate the theory of the plasma filled microwave device.This paper analyzes the breakdown process of the vacuum diode,establishes the mathematical model of the radiating microwave from the vacuum diode.Based on the analysis of the dispersion relation in the form of a refractive index,the electromagnetic waves generated in the vacuum diode will resonate.The included angle between the direction of the electromagnetic radiation and the initial motion direction of electron beam is 45 degrees.The paper isolates the electrostatic effect from the beam-plasma interaction when the electromagnetic radiation occurs.According to above analyses,the dispersion relations of radiation are obtained by solving the wave equation.The dispersion curves are also obtained based on the theoretical dispersion relations.The theoretical dispersion curves are consistent with the actual measurement time-frequency maps of the radiation.Theoretical deduction and experiments indicate that the reason for microwave radiating from the vacuum diode can be well explained by the interaction of the electron beam and magnetized plasma.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11575183 and 11705201)
文摘Pseudowaves, known as burst-ion signals, which are different from plasma normal modes, exist frequently in ion- wave excitation experiments when launching the waves by applying a pulsed voltage to a negatively biased grid. In previous experiments, only one kind of the pseudowave was observed. In this paper, we report the observation and identification of double pseudowaves in an ion-beam-plasma system. These pseudowaves originate from two ion groups： the burst of the beam ions and the burst of the background ions. It was observed that the burst of the background ions was in the case of high ion beam energy, while the burst of the beam ions was in the case of low ion beam energy. By observing the dependence of the signal velocities on the characteristics of the excitation voltage, these pseudowaves can be identified. It was also observed that the burst ion signal originating from the background ions can interact with slow beam mode and that originating from the beam ions can interact with fast beam mode.
文摘The stabilization effect of a strong HF electric field on beam-plasma instability in a cylindrical warm plasma waveguide is discussed. A mathematical technique “separation method” applied to the two-fluid plasma model to separate the equations, which describe the system, into two parts, temporal and space parts. Plasma electrons are considered to have a thermal velocity. It is shown that a HF electric field has no essential influence on dispersion characteristics of unstable surface waves excited in a warm plasma waveguide by a low-density electron beam. The region of instability only slightly narrowing and the growth rate decreases by a small parameter and this result has been reduced compared to cold plasma. Also, it is found that the plasma electrons have not affected the solution of the space part of the problem.
文摘偶极磁场约束等离子体特性及其与带电粒子束的相互作用研究是近地空间磁层等离子体研究领域关心的一类重要问题.本研究采用粒子模拟(particle in cell, PIC)方法,通过开源的Smilei程序,研究了电子束注入偶极磁场约束等离子体的三维动力学演化行为.模拟了不同注入角度电子束对等离子体的影响,给出了电子束及等离子体的时空演化过程和行为解释.结果显示,偶极磁场中的等离子体沿磁场线形成“新月形”壳结构分布,壳中形成内外相反方向的环形电流.当电子束的注入角度与磁场方向的夹角过大(超过20°),且漂移速度方向未对准偶极场中心时,大多数电子束粒子将在偶极磁场中漂移,散射并弹出模拟区域,无法与偶极磁场约束的等离子体发生相互作用.未来我国的偶极磁场约束等离子体研究装置在开展电子束与等离子体相互作用的实验时,有必要选择适当的电子束入射方向,以确保电子束能够进入偶极磁场的核心区域并与原来约束的等离子体进行相互作用.同时模拟结果显示电子束注入会使得等离子体环形电流在环向上变得不均匀.本研究有助于深入了解偶极磁场中的等离子体动力学行为特性,对于保障我国空间等离子体研究装置完成预期科学目标具有实际价值.
文摘目的:观察Plasma等离子束联合强脉冲光治疗面部烧伤瘢痕的疗效及对瘢痕评分、疼痛程度的影响。方法:本次研究为前瞻性研究,采用随机数字表法将茂名市人民医院2024年3月至2024年8月期间收治的92例面部烧伤瘢痕患者分为对照组(接受强脉冲光治疗,46例)和研究组(对照组的基础上接受Plasma等离子束治疗,46例)。对比两组疗效、相关量表评分、瘢痕恢复情况和不良反应发生率。结果:和对照组治疗后相比,研究组的临床总有效率和中文版简易烧伤健康量表(chinese version of the simplified burn health scale, BSHS-B)评分更高,温哥华瘢痕量表(vancouver scar scale, VSS)、视觉模拟疼痛量表(visual analogue scale, VAS)评分和瘢痕厚度、瘢痕血流灌注量更低(P<0.05)。两组不良反应发生率组间对比未见差异(P>0.05)。结论:应用Plasma离子束联合强脉冲光治疗面部烧伤瘢痕患者,可提高临床疗效,改善瘢痕厚度和血流灌注量,缓解瘢痕瘙痒及疼痛程度,安全性较好。
