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An analysis of gain-decreasing over a long plasma medium for recombination X-ray laser
Published in S Svanberg, C-G Wahlström, X-ray Lasers 1996, 2020
R X Li, Z Z Xu, Z Q Zhang, P Z Fan, S S Han, Y Q Liu, W Yu
As was stated in the second part of the paper, the measured nonuniformity of the laser irradiation of the focal line is small Why can it then cause so serious effects on the plasma parameters in the gain region? There are a few explanations of the evolution of the nonuniformity, such as the development of several kinds of plasma instabilities. Here we put them aside, only consider the result of a pure fluid expansion. We use a simple model assuming adiabatic self-similar expansion following laser heating[9] to address this question and found that the difference in density is not limited to the initial value of 10%, it dramatically increases when the plasma expands.
Investigating the impact of the latitudinal velocity profile on nonlinear gradient drift instability development in the subauroral ionosphere
Published in Radiation Effects and Defects in Solids, 2022
Lujain Almarhabi, Chirag R. Skolar, Wayne Scales, Bhuvana Srinivasan
The corresponding power spectra of the normalized density and perturbed potential is shown in Figure 3. In Figure 3, we notice that all different values of follow the same power laws in the inertial range with spectral indices of and for the normalized density and perturbed potential, respectively. From non-linear theory [9], a spectral index of is expected for the power spectra of the density fluctuations for the GDI which is in accordance with past observations [10–12]. In particular, we refer to Table I in Ref. [12], listing density and electric field fluctuations spectral slopes for different plasma instabilities. The spectral slopes for the different simulations in Figure 3 are taken at four different times since each one of these simulations have a different growth rate based on Equation (4). Therefore, we conclude that the neutral wind direction has minimal to no impact on the density and electric potential power spectra.
Homoclinic tangle of the primary separatrix in the compact and closed versus open and unbounded magnetic topologies for divertor tokamaks
Published in Radiation Effects and Defects in Solids, 2018
The plasma in a modern tokamak (1) is bounded by a separatrix between magnetic field lines that form toroidal magnetic surfaces, on which the plasma is confined, and open field lines that divert the plasma exhaust to the divertor plates (see Figure 1). An ideal tokamak is axisymmetric, and its separatrix is a sharp surface. Asymmetries in the magnetic field cause the last confining magnetic surface to lie inside the ideal separatrix and create a layer of open field lines between the last confining surface and the ideal separatrix, which we call the stochastic layer. Plasmas flow rapidly along magnetic field lines and diffuse slowly across. Near the X-point, the width of the stochastic layer is proportional to the square root of the toroidally asymmetric part of the magnetic field (2). The asymmetric part of the field may be caused by deviations in the tokamak coils from axisymmetry, magnetic perturbations due to plasma instabilities, or the effects of special coils introduced to control the width of the stochastic region.
Standard variable short period microwave-plasma undulator
Published in Waves in Random and Complex Media, 2023
Mansour Hadad, Sirous Yousefnejad, Farhad Saeidi, Javad Rahighi, Babak Shokri
Insertion devices, regardless of their types, might change beam characteristics such as emittance and energy spread. These effects could be useful and desirable or detrimental and undesirable. For example, their effect on reducing beam emittance, in the storage ring of third-generation light sources where dispersion is equal to zero in straight sections, paved the way for the development of devices such as damping wigglers. In conventional undulators, electron beam moves through very high vacuum chambers and therefore there is no concern about electron beam interactions with the environment. In plasma, though, beam–plasma interactions might change beam dynamics’ parameters and degrade electron beam quality. Degradation of electron beam quality could be resulted from plasma instabilities or electron beam wakefields. For tiny beams, plasma instabilities are ignorable. For example, the growth rate of two-stream instability, which exists in plasma with relativistic electron beams, has the form of , where and are electron beam and plasma densities. If the e-folding length of instability is larger than beam length, i.e. , then the two-stream instability will not grow. A single bunch of 3 GeV (γ = 5870) electrons in the ILSF storage ring has a length of about 8 mm. For plasma density of and plasma frequency of , the length of instability is about 183 mm which means the two-stream instability will not grow.