共查询到15条相似文献,搜索用时 62 毫秒
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试验束(testbeam)是高能实验物理中具有广泛用途的实验设施,世界各主要高能物理实验室都建有若干条试验束。它一方面用于对高能加速器潜力的开发利用,另一方面也是为许多试验研究提供一个实验平台,例如为高能探测器提供作“刻度”用的束流。那么什么是刻度呢?打个比方,做一杆秤,把挂钩、秤杆、秤砣等连到一起成了秤的样子后,还并不能用,必须进一步作刻度:在秤杆上把斤两刻出来,才能知道是几斤几两。高能物理实验要用高能探测器来探测粒子,它不仅要能判别正负电子对撞产生的是什么粒子,还要能测定粒子的动量等物理量. 相似文献
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介绍了北京正负电子对撞机直线加速器附设e,p试验束多丝室的结构及工作机理。该室间隙6 mm,窗口面积80 mm×80 mm,位置灵敏面积50 mm×50 mm;阳极丝和阴极丝分别采用直径为20 mm和50 mm镀金钨丝,阳极丝距2 mm,阴极丝距0.7 mm,每6根阴极丝并联构成阴极条,阴极条间距4.2 mm。采用阴极条感应重心读出分辨位置,对5.9 keV的γ光子,获得优于0.3 mm (FWHM)的位置分辨;对1.1 GeV电子束流,获得0.224 mm (FWHM)的位置分辨。 相似文献
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介绍了北京正负电子对撞机直线加速器附设e,p试验束多丝室的结构及工作机理。该室间隙6 mm,窗口面积80 mm×80 mm,位置灵敏面积50 mm×50 mm;阳极丝和阴极丝分别采用直径为20 mm和50 mm镀金钨丝,阳极丝距2 mm,阴极丝距0.7 mm,每6根阴极丝并联构成阴极条,阴极条间距4.2 mm。采用阴极条感应重心读出分辨位置,对5.9 keV的γ光子,获得优于0.3 mm (FWHM)的位置分辨;对1.1 GeV电子束流,获得0.224 mm (FWHM)的位置分辨。 相似文献
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Donghuan Zhao 《Chinese Journal of Lasers》1993,2(4):299-305
In this paper, the effects of physical parameters on the gain and efficiency of Cherenkov type FEL are studied through simulative compute. The results show that the permittivity ε and periodic length λ_(?) of wiggler magnetic filed are two important parameters which influence the properties of laser. The magnitude ε has effect on the properties of gain, and the choice of wigger λ_(?) can increase gain and efficiency of the laser. The calculation results show that the gain and efficiency of Cherenkov type FEL are considerably higher than those of Compton-Raman type FEL under some conditions with proper parameters. 相似文献
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利用自洽线性场理论,导出了薄环形相对论电子注通过填充等离子体的介质同轴波导中的注波互作用色散方程,得到了注波互作用产生切伦科夫辐射的同步条件和波增长率。分析了填充等离子体后的波与电子注之间的能量交换及等离子体密度对色散特性、波增长率和注波能量交换的影响。分析结果表明:切伦科夫辐射是由沿介质同轴波导传播的慢波与沿薄环形相对论电子注传播的负能空间电荷波耦合所致,且其耦合强度与电子注的密度成正比;输出频率和波增长率随着填充等离子体密度的增大而提高;保持一定的输出频率,增大电子注的束流可得到高的微波输出功率。 相似文献
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In this article, we propose a quantum regime for Cherenkov free-electron laser (CFEL) and surface plasmon polaritons (SPPs) excited in dielectric and multilayer graphene waveguides, respectively. This quantum regime is realized when the momentum spread induced in the interaction is smaller than the photon recoil. The discrete momentum exchange characterizing this interaction yields a significantly narrow single emission line. To determine the condition of the quantum regime, we derive an expression for the gain in the Cherenkov effect using a quantum mechanical treatment. It is assumed that the effective spread in momentum is due to the finite interaction length L (or the propagation length in the case of SPPs). For both cases, CFEL and SPPs, the effects of electron beam and waveguide parameters on the possibility of the quantum regime are studied. We conclude that the quantum regime can be basically verified at low electron beam energy (<40 keV) and at emission wavelengths in the near infrared range (<5 μm) when L is in the order of millimeters. In the case of SPPs, we also show that the feasibility to realize quantum SPPs is enhanced by increasing the chemical potential and number of graphene layers. 相似文献
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Cherenkov terahertz radiation from Dirac semimetals surface plasmon polaritons excited by an electron beam 下载免费PDF全文
We demonstrate a physical mechanism for terahertz(THz) generation from surface plasmon polaritons(SPPs). In a structure with a bulk Dirac semimetals(BDSs) film deposited on a dielectric substrate, the energy of the asymmetric SPP mode can be significantly enhanced to cross the light line of the substrate due to the SPP-coupling between the interfaces of the film. Therefore, the SPPs can be immediately transformed into Cherenkov radiation without removing the wavevector mismatch. Additionally, the symmetric SPP mode can also be dramatically lifted to cross the substrate light line when a buffer layer with low permittivity relative to the substrate is introduced. In this case, dual-frequency THz radiation from the two SPP modes can be generated simultaneously. The radiation intensity is significantly enhanced by over two orders due to the field enhancement of the SPPs. The radiation frequency can be tuned in the THz frequency regime by adjusting the beam energy and the chemical potential of the BDSs. Our results could find potential applications in developing room temperature, tunable, coherent, and intense THz radiation sources to cover the entire THz band. 相似文献
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Modern accelerator technologies may provide electron beams consisting of ultrashort bunches with transverse sizes, which are much larger than longitudinal sizes. The spectral-angular characteristics of coherent Cherenkov radiation (CChR) produced by such bunches have thus been considered. We simulated the characteristics of CChR and those from a single charge on the basis of the polarization current model, which allowed us to consider finite sizes for the Cherenkov radiator. We calculated the angular distribution of the CChR from a bunch tilted by angle ψ, with respect to the velocity direction, with the assumption of a 3-D Gaussian charge distribution in the bunch. Contrary to the azimuthally symmetrical distribution of conventional ChR, a strong azimuthal asymmetry was observed in the CChR from the tilted bunch. The maximal yield of the CChR may be achieved if the tilt angle ψ coincides with the Cherenkov angle , βc is the charge velocity and n is the refraction index. 相似文献
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Correlation phenomena occurring in Cherenkov radiation are considered which are related to fluctuations of the charge states
of multiply charged accelerated ions in a medium. The additional correlation contribution to the radiation is determined by
the root-mean-square deviation of the ion charge from its equilibrium value and is responsible for the nonzero radiation yield
in the event that the threshold condition is not fulfilled. Numerical estimates of the radiation yield of heavy ions in the
optical and X-ray frequency ranges are given.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 41–46, January, 2009. 相似文献
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理论分析了无限大引导磁场情况下的薄环形等离子体介质切伦柯夫脉塞。得出了通入相对论电子注时行列式形式的热腔色散方程,并求出了波增长率。针对不同等离子体密度下,对色散方程以及波增长率进行数值计算和模拟验证。研究发现与电子注作用的主要模式为低频等离子体模式中的前两个模式,随着等离子体密度的升高,脉塞中心工作频率升高、增益变大、带宽明显变宽,由模拟结果可以看出:等离子体频率为4.5×1019 m-3时对应着最大的输出功率为80 MW,效率为19.75%,频率为15.55 GHz,继续增大等离子体密度虽然可以使输出频率进一步提高,但是同时会使输出功率迅速下降。 相似文献
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讨论了γ光子在同一种介质中连续产生康普顿散射和切连科夫辐射的条件。这一条件可用产生切连科夫辐射的康普顿电子在介质中的临界散射角的大小来表示。 相似文献