Selective Excitation of Low Frequency Drift Waves by Density Modulation and Parametric Excitation of Higher Frequency Mode

Biswas, Subir; Basu, Debjyoti; Pal, Rabindranath; Chakrabarti, Nikhil

doi:10.1103/physrevlett.111.115004

Cited by 11 publications

(10 citation statements)

References 26 publications

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“…4(d). The similar results were also observed by the Biswas et al [37,38], who studied the floating potential measurement in ECR produced plasmas and found the low-frequency oscillations. It may also be explained by nonlinear coupling [39] of wave propagation, neutral and plasma density, microwave power absorption and plasma temperature.…”

Section: Theoretical Justificationsupporting

confidence: 87%

Experimental investigation of plasma instabilities by Fourier analysis in an electron cyclotron resonance ion source

Kumar

Sharma

et al. 2018

Phys. Rev. Accel. Beams

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The plasma instabilities play an important role in an electron cyclotron resonance (ECR) ion source for the production of intense heavy ion beams in high charge states for particle accelerators. The geometrical and operational constraints of ECR sources hinder the trapping of ions for a sufficient time to get fully ionized with maximum efficiency. This problem is looked at in detail by studying the plasma instabilities in ECR ion sources. The ECR environment is full of complex rearrangements of various electric and magnetic fields to define a sustainable trap for the ions. The maximum frequency of plasma instability has been observed to be of 122.5 kHz under a set of sustainable plasma parameters. However, this limit may be pushed further if the plasma is overdriven in terms of source parameters. The instabilities cover a full regime of few tens of Hz to few hundreds of kHz under various operating conditions of radio frequency (rf), negative bias voltage, rf power and injection gas pressure. The rigorous details of frequencies and amplitudes of plasma instabilities are being reported by studying the Fourier spectrum of extracted and analyzed beam intensity. The plasma instabilities are attributed as drift waves in an inhomogeneous ECR plasma generated by the application of radio-frequency fields.

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Section: Theoretical Justificationsupporting

confidence: 87%

Experimental investigation of plasma instabilities by Fourier analysis in an electron cyclotron resonance ion source

Kumar

Sharma

et al. 2018

Phys. Rev. Accel. Beams

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“…Our review of taxa that retain a basipterygoid process, including basal turtles, most meiolaniforms, xinjiangchelyids, sinemydids, and macrobaenids reveals that these taxa possess poorly developed otic trochlea (if any) in form of a rugose surface or a low ridge that only barely protrudes anteriorly, unlike in taxa where the basipterygoid process is absent, including plesiochelyids, eurysternids, baenids, and most crown-group cryptodires, where the otic trochlea is robust and protrudes significantly (Figure 9). The condition in pleurodires is also consistent with this correlation as they have an advanced trochlear process formed by the pterygoid and the basipterygoid process is absent even in the earliest known extinct species, Notoemys laticentralis (Figures 9 and 10I) [101]. …”

Section: Resultsmentioning

confidence: 53%

“…The basisphenoid of this species shows a very reduced lateral protrusion just anterior to the foramen posterius canalis carotici interni ([100], Figure 2B; [101], pl. 1C).…”

Section: Resultsmentioning

confidence: 99%

A new xinjiangchelyid turtle from the Middle Jurassic of Xinjiang, China and the evolution of the basipterygoid process in Mesozoic turtles

et al. 2013

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BackgroundMost turtles from the Middle and Late Jurassic of Asia are referred to the newly defined clade Xinjiangchelyidae, a group of mostly shell-based, generalized, small to mid-sized aquatic froms that are widely considered to represent the stem lineage of Cryptodira. Xinjiangchelyids provide us with great insights into the plesiomorphic anatomy of crown-cryptodires, the most diverse group of living turtles, and they are particularly relevant for understanding the origin and early divergence of the primary clades of extant turtles.ResultsExceptionally complete new xinjiangchelyid material from the ?Qigu Formation of the Turpan Basin (Xinjiang Autonomous Province, China) provides new insights into the anatomy of this group and is assigned to Xinjiangchelys wusu n. sp. A phylogenetic analysis places Xinjiangchelys wusu n. sp. in a monophyletic polytomy with other xinjiangchelyids, including Xinjiangchelys junggarensis, X. radiplicatoides, X. levensis and X. latiens. However, the analysis supports the unorthodox, though tentative placement of xinjiangchelyids and sinemydids outside of crown-group Testudines. A particularly interesting new observation is that the skull of this xinjiangchelyid retains such primitive features as a reduced interpterygoid vacuity and basipterygoid processes.ConclusionsThe homology of basipterygoid processes is confidently demonstrated based on a comprehensive review of the basicranial anatomy of Mesozoic turtles and a new nomenclatural system is introduced for the carotid canal system of turtles. The loss of the basipterygoid process and the bony enclosure of the carotid circulation system occurred a number of times independently during turtle evolution suggesting that the reinforcement of the basicranial region was essential for developing a rigid skull, thus paralleling the evolution of other amniote groups with massive skulls.

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“…It is observed that whereas there is a drifting component at 3 and 5 cm, no such component exists at r = 8 cm. Also in a previous experiment 22 at low microwave power a mach probe diagnostic showed that there is no drifting component at r = 0 cm. Interestingly, at r = 0 and 8 cm of the launcher position no wave propagation is observed (Fig.…”

Section: Discussion and Theoretical Analysismentioning

confidence: 99%

Experimental observation of electron-acoustic wave propagation in laboratory plasma

et al. 2017

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In the field of fundamental plasma waves, direct observation of electron-acoustic wave (EAW) propagation in laboratory plasmas remains a challenging problem, mainly because of heavy damping. In the MaPLE device, the wave is observed and seen to propagate with phase velocity ∼ 1.8 times the electron thermal velocity. A small amount of cold, drifting electrons, with moderate bulk to cold temperature ratio (≈ 2 − 3), is present in the device. It plays a crucial role in reducing the damping. Our calculation reveals that the drift relaxes the stringent condition on the temperature ratio for wave destabilization. Growth rate becomes positive above a certain drift velocity even if the temperature ratio is moderate. The observed phase velocity agrees well with the theoretical estimate. Experimental realization of the mode may open up a new avenue in EAW research.

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Selective Excitation of Low Frequency Drift Waves by Density Modulation and Parametric Excitation of Higher Frequency Mode

Cited by 11 publications

References 26 publications

Experimental investigation of plasma instabilities by Fourier analysis in an electron cyclotron resonance ion source

Experimental investigation of plasma instabilities by Fourier analysis in an electron cyclotron resonance ion source

A new xinjiangchelyid turtle from the Middle Jurassic of Xinjiang, China and the evolution of the basipterygoid process in Mesozoic turtles

Experimental observation of electron-acoustic wave propagation in laboratory plasma

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