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1.
屈卫星  徐至展 《物理学报》1988,37(6):892-898
本文根据介质的宏观极化理论,导出了中能量相对论电子穿越单一介质箔和介质箔组时产生的渡越辐射量子微分谱公式,并利用该公式对铍箔及铍箔组的情况进行了计算。计算结果与实验符合。 关键词:  相似文献   

2.
超短脉冲激光辐照固体靶背向光发射的测量   总被引:3,自引:0,他引:3  
利用光学CCD相机和OMA光学多道分析仪,分别在金属箔背表面法线方向测量了光发射的积分成像光谱和散射光光谱。积分成像光谱测量结果显示,光谱呈圆环状,在圆环边缘附近出现局部化明亮光信号确定为超热电子输运穿越固体靶引起的光学渡越辐射(OTR);散射光光谱测量结果显示,光谱在300~500 nm之间出现一系列非周期锐利尖峰,在400 nm(2ω)附近出现的尖峰归结于v×B加热机制产生的超热电子束中的聚束引起的相干渡越辐射(CTR)。渡越辐射光强随靶厚度的增加而减小。  相似文献   

3.
从金属箔背表面测量了超热电子穿越固体靶产生的光发射.光发射积分成像图案呈圆环状,在圆环边缘附近出现局部化明亮光信号确定为光学渡越辐射;光发射光谱在300—500nm之间出现一系列非周期锐利尖峰,在400nm(2ω)附近的尖峰较明显,这个光发射取决于v×B加 热机制产生的超热电子束的微束团引起的相干渡越辐射,(v为电子电度,B为磁场强度),光 强随靶厚度的增加而减小. 关键词: 超热电子 光发射 光学渡越辐射 v×B加热机制 相干渡越辐射  相似文献   

4.
利用相干渡越辐射(CTR)测量短和超短电子束团长度是国际上束测领域新发展的频域测量技术.文中理论分析和数值计算了北京自由电子激光装置的皮秒级的射频电子束团序列产生的CTR,当辐射波长在长于束长(4ps)时,渡越辐射发生相干增强效应;与非相干渡越辐射相比,当λ≥2πσz时,增强的倍数约等于束团中粒子的数目(108);CTR从亚毫米波到毫米波段呈宽带连续谱特性;渡越辐射能量主要集中在轴线附近,宏脉冲辐射能量高达几毫焦.设计采用偏振型束团长度测量系统,利用CTR自相关技术,实验测量该束团序列的纵向长度,并藉助傅里叶变换光谱法,推求束团电子分布.  相似文献   

5.
由波荡器渡越辐射公式和电子通过wiggler边界产生的长波长辐射公式, 解析给出了电子通过光学速调管时产生的长波长辐射公式. 根据基本的电动力学公式数值计算出合肥同步辐射装置光学速调管的长波辐射, 并将其结果与解析公式的结果进行比较. 计算合肥同步辐射装置的光学速调管和弯转磁铁在红外波段范围内辐射的强度和通量, 表明光学速调管有很好的性能.本文说明, 光学速调管不但可以用来进行相干谐波的试验研究, 也可以兼用作储存环中的红外辐射光源.  相似文献   

6.
利用惠更斯-菲涅耳衍射积分公式,推导了高斯-谢尔模型光束经非线性克尔介质的表面缺陷调制后的交叉谱密度公式,研究了受调制高斯-谢尔光束的光强演化特性。数值模拟表明:缺陷也可导致部分相干光束在介质后表面产生一个极强点,缺陷越大,极强点越远离介质。非线性折射率为正值或负值的介质也分别使部分相干光束发生会聚或发散现象。空间相干长度越长以及附加相移和缺陷尺寸越大,光场受调制越厉害。  相似文献   

7.
利用惠更斯-菲涅耳衍射积分公式,推导了高斯-谢尔模型光束经非线性克尔介质的表面缺陷调制后的交叉谱密度公式,研究了受调制高斯-谢尔光束的光强演化特性。数值模拟表明:缺陷也可导致部分相干光束在介质后表面产生一个极强点,缺陷越大,极强点越远离介质。非线性折射率为正值或负值的介质也分别使部分相干光束发生会聚或发散现象。空间相干长度越长以及附加相移和缺陷尺寸越大,光场受调制越厉害。  相似文献   

8.
利用渡越辐射研究超热电子束的传输特性   总被引:3,自引:3,他引:0       下载免费PDF全文
 为了探索超热电子束的传输特性,利用光学CCD相机在靶背法线方向测量了光学渡越辐射积分成像图案。实验在100 TW掺钛蓝宝石激光器上进行,飞秒激光与固体靶作用后,靶表面发光信号由空间分辨装置聚焦成像并引到CCD狭缝上。在厚度为20 μm的Ta靶背表面观测到渡越辐射光斑呈现较平滑的圆形结构,而且中心亮度高于周围,这包含了非相干与相干渡越辐射的成分,与理论模拟结果接近;在厚度为100 μm的Ta靶背表面观测到渡越辐射光斑呈现出星状结构,光斑较小,与高能质子发射出现的星状结构极其相似;在复合靶背表面观测到渡越辐射光斑虽然也呈现大致的圆形结构,但光斑较大,而且极不均匀,中间有很明显的光斑分裂。  相似文献   

9.
为了探索超热电子束的传输特性,利用光学CCD相机在靶背法线方向测量了光学渡越辐射积分成像图案。实验在100 TW掺钛蓝宝石激光器上进行,飞秒激光与固体靶作用后,靶表面发光信号由空间分辨装置聚焦成像并引到CCD狭缝上。在厚度为20 μm的Ta靶背表面观测到渡越辐射光斑呈现较平滑的圆形结构,而且中心亮度高于周围,这包含了非相干与相干渡越辐射的成分,与理论模拟结果接近;在厚度为100 μm的Ta靶背表面观测到渡越辐射光斑呈现出星状结构,光斑较小,与高能质子发射出现的星状结构极其相似;在复合靶背表面观测到渡越辐射光斑虽然也呈现大致的圆形结构,但光斑较大,而且极不均匀,中间有很明显的光斑分裂。  相似文献   

10.
在超强脉冲激光与固体靶相互作用中,利用光学CCD相机和光学多道分析仪,分别在固体薄膜靶背表面法线方向测量了渡越辐射(TR)积分成像图案和光谱。测量结果显示:TR空间分布图案呈圆环状,而辐射区域有发散角和光强分布;TR光谱在800 nm附近出现尖峰,是激光的基频波,这一现象归因于超热电子束在输运的过程中产生的微束团而引起的相干渡越辐射;如果考虑超热电子的产生和加热机制,共振吸收和真空加热对超热电子都有贡献,其中占主导地位的加热机制则是共振吸收对电子的加热。  相似文献   

11.
The interference of transition radiation coherently produced from a periodic stack of four polyimide foils of 7.2 μm thickness and a separation of 162 μm was investigated. This stack has been brought into the low emittance (3 π nm rad) electron beam of the 855 MeV Mainz Microtron MAMI. Transition radiation was observed in the energy range from 2 to 15 keV with a LN2-cooled pin photodiode. A good energy resolution of 0.8 keV and angular resolution of 0.15 mrad was achieved simultaneously allowing for the first time to quantitatively study the interference pattern. Good agreement with theoretical calculations is found. Prospects to exploit transition radiation in the x-ray region from a low emittance electron beam as a high brilliant radiation source are discussed.  相似文献   

12.
Measurements have been made of X-ray transition radiation spectra, which were produced by relativistic electrons traversing periodic stacks of mylar and lithium foils. The dependence of the spectral yield on the stack parameters and on the momentum of the electrons establishes the influence of long-range coherence in the emission of transition radiation.  相似文献   

13.
We directly follow the evolution of the absorption spectrum from a single molecule to a dimer and further to a one-dimensional molecular stack: We determine the optical absorption properties of ordered monolayer to multilayer films of PTCDA (3,4,9,10-perylenetetracarboxylic dianhydride) on muscovite mica(0001) surfaces by in situ differential reflectance spectroscopy. The data clearly show the transition from the single molecule to a dimer spectrum, followed by the exciton delocalization to a molecular crystal exciton. The accompanying spectral shifts compare favorably with recent model concepts.  相似文献   

14.
《Current Applied Physics》2015,15(3):242-247
A theoretical examination on coherent transition radiations (CTR) from the surface of thin solid density target irradiated by high intensity laser is presented. The theory is extended to consider the expansion dynamics of thin foils. The motion of target surfaces leads to the modulation on the temporal structure of micro bunches in the electron beam as well as the spectrum of CTR. The spectral shifts of radiation are owing to the enhancement of electron bunch separation and the relativistic Doppler effects. The radiation power distribution is strongly affected by the temporal coherence of electron beam structure, so thus the electron temperature and velocity dispersions. With these effects accounted for, the spectral properties of coherent transition radiation can provide insights into the expansion of thin foil targets irradiated by intense laser pulse as well as the fast electron transport through it.  相似文献   

15.
Semiclassical relativistic energy losses and the transition radiation are calculated for fast charged particles (e.g. electrons) traversing a thin dielectric foil at oblique incidence. The transition radiation formula is generalized for foils with spatial dispersion. This formula for oblique electron incidence is of particular interest for the observation of Cerenkov radiation, emitted from a dielectric foil. The emission of Cerenkov radiation is discussed for varying electron incidence angle and foil thickness by the aid of numerical computations.  相似文献   

16.
Results of experiments conducted at the Tomsk synchrotron to study resonant X-ray transition radiation generated by relativistic electrons in periodic multifoil radiators are reviewed. Both the internal synchrotron beam and the external secondary electron beam from the pair magnetic γ-spectrometer with energies ranging from 300 to 900 MeV were used in the experiments. The radiators consisted of many thin amorphous foils of various materials. The generation of X-ray radiation in a compound radiator consisting of a multifoil radiator and a crystal is also studied. In this case, the resonant X-ray transition radiation generated in the multifoil radiator is diffracted in the crystal and emitted at Bragg angles, together with the parametric X-ray radiation generated in the crystal. Spectral and angular properties of the resonant X-ray transition radiation and diffracted resonant X-ray transition radiation are investigated. The ratio between the contributions from the diffracted resonant X-ray transition radiation and other types of radiation to the total coherent X-ray radiation flux generated by electrons in periodic structures and crystals is estimated.  相似文献   

17.
For wavelengths near 5000 Å the index of light refraction in silicon is so large, that a considerable amount of Cerenkov radiation is generated by 50 keV electrons. We discuss experimental radiation pattern of transition radiation including Cerenkov radiation emitted from 50 keV electrons traversing thin silicon foils of 2000 Å thickness at different angles of electron incidence. There is good agreement of the experimental results with theory.  相似文献   

18.
The electromagnetic radiation of a quantum semiconductor nanorod (considered in a dipole model), placed into a multilayered microsphere with alternative spherical stack, is studied. We found that the frequency spectrum consists of series of narrow and well separated peaks even in a lossy case. In the band of such peaks the great part of the field energy is located in the structure of the stack and practically does not leave the microsphere. A possibility of resonant coupling of photon states in the area of nanorods is discussed.  相似文献   

19.
Using the method of the elastic recoil detection (ERD) of hydrogen nuclei and a Plasma Focus setup (PF-4), we study the processes of the storage and redistribution of hydrogen and deuterium atoms in a stack of two tantalum foils and a deuterated polyethylene film sandwiched between them under pulsed irradiation with hot nitrogen plasma. It is established that the redistribution of implanted deuterium and hydrogen occurs at greater depths in both tantalum foils after 30 pulses of nitrogen plasma. The maximum concentrations of hydrogen and deuterium, namely 7 and 45 at % are observed on the surface of the second tantalum foil which is more distant from the PF-4 setup. The redistribution of deuterium from deuterated polyethylene onto the surface and volume of both Ta foils is observed. The observed phenomenon can be explained by the breaking of chemical bonds in the deuterated polyethylene and the transfer of freed deuterium into the Ta foils under the action of strong shock waves formed in the structure, as well as the accelerated diffusion of hydrogen and deuterium in the stress field caused by the shock wave.  相似文献   

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