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Dive into the research topics where Ivo Čermák is active.

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Featured researches published by Ivo Čermák.


IEEE Transactions on Plasma Science | 2004

Mass-loss rate for MF resin microspheres

Jiri Pavlu; A. Velyhan; Ivana Richterova; Zdenek Nemecek; J. Šafránková; Ivo Čermák; Peter Zilavy

This paper deals with the influence of experimental conditions on properties of melamine formaldehyde resin particles. Motivation for this study was the fact that many laboratories and experimenters use these particles as samples for dust plasma investigations. We have found that the mass of these grains decreases during long-time exposure in vacuum. This decrease proceeds much faster if the temperature of grains is increased.


Faraday Discussions | 2008

Interaction between single dust grains and ions or electrons: laboratory measurements and their consequences for the dust dynamics

J. Pavlů; Ivana Richterova; Z. Němeček; J. Šafránková; Ivo Čermák

The present paper reviews our latest, and brings several new, results on charging of dust grains of various materials and sizes. Charging processes of dust in space and their influence on the dust dynamics are analyzed in laboratory simulations of secondary emission, field ion and electron emissions, and dust sputtering. Single micrometre-sized grains and grain clusters are stored in a hyperbolic quadrupole field under ultra-high vacuum conditions for long time periods. The charge state of the grain and its evolution are recorded while the grain is exposed to ion or electron beams of various energies and fluxes. The influence of the secondary electron emission on the charge state is measured and compared with a computer model. Limitations on the grain charge by the field electron and ion emission are considered next. The measurements allow analyzing field emission from conductive and dielectric grains. The existence of long-lived surface states on insulating materials, which are probably responsible for the anomalous behavior of field electron emission and the low threshold of the field ion emission, is indicated. The observation of sputtering by energetic ions showing a surprising anisotropic erosion of a conductive grain is analyzed. The sputtering and the field ion emission are discussed as possible sources of the so-called pick-up ions.


Review of Scientific Instruments | 2001

On the combination of a linear field free trap with a time-of-flight mass spectrometer

Alfonz Luca; Stephan Schlemmer; Ivo Čermák; Dieter Gerlich

A new instrument has been developed which combines a rf ring electrode trap and a time-of-flight mass spectrometer (TOF-MS). The wide field free storage volume of such a trap enables the study of low temperature ion-molecule collisions; however it is not straightforward to match the nonlocalized ion cloud to the TOF-MS. For obtaining sufficient mass resolution, a special pulse sequence has been developed to transfer the ions from the whole trap volume to a small region in the vicinity of the exit electrode. Additional compression is achieved via buffer gas relaxation prior to extracting the ions. Using a linear flight path of 57 cm, a mass resolution of about 50 is routinely achieved. The mass range of the whole instrument, which is determined by the operating conditions both of the trap and the TOF-MS, has been estimated to be 3–700 u. The actual characteristics of the instrument such as mass range, resolution, and dynamical range have been determined and the results have been analyzed. As a typical appl...


Review of Scientific Instruments | 2005

Compact radio-frequency power supply for ion and particle guides and traps

Ivo Čermák

In this article, we present a modern compact rf or ac power generator that uses a resonant driving scheme without the necessity for any matching device. The developed unit also does not need any expensive high voltage power supply for generating output voltages in the range of some 100 V typically required for the function of trapping devices. The high efficiency of the generator allows long-term operation at output powers of around 50 W without any performance losses. The frequency range of the device is determined by the output transformer. It can be varied from the megahertz range down to some kilohertz by replacing the output transformer and several capacitors in the control part of the generator. Thus, our device can be used for supplying traps operating with ions as well as with charged nano- or microparticles.


IEEE Transactions on Plasma Science | 2004

Emissions from nonconducting negatively charged dust grains

Jiri Pavlu; Zdenek Nemecek; J. Šafránková; Ivo Čermák

Dust grains immersed into a low-temperature plasma are charged negatively because the electron attachment dominates other charging processes. However, increasing energy of impinging electrons leads to the increase of the yield of secondary emission. When this yield exceeds unity, the grain becomes charged positively. Previous laboratory experiments with electron beams have shown that the surface potential of large grains follows roughly an energy dependence of the secondary emission yield. It means that the grain potential reaches its maximum for hundreds of electronvolts of electron energy and then decreases. Model calculations reveal that the decrease of the grain potential with the electron energy can lead to the reversal of charge sign in a certain range of grain diameters. After this reversal, the grain is charged to the negative potential close to the beam energy. We use of this effect for investigations of electron field emission from nonconducting spheres (glass and melamine formaldehyde resin) with the diameter 4-11 /spl mu/m for glass and 5 and 10 /spl mu/m for resin. Single grains were trapped in a Paul trap and bombarded by the electron beam. The beam energy was changed in a range of 0.3-10 keV. The experimental results confirm the aforementioned expectations and an analysis of these results has shown that: 1) the effective work function for electron field emission from charged nonconducting materials (glass and melamine resin) could be as low as 2 eV, but it can be close to 5 eV as expected for insulating materials. The difference is connected with the charging history. 2) The effect of field dependent secondary emission limits the attainable negative potential.


Czechoslovak Journal of Physics | 2003

Problems of Dust Grains Charging to Negative Potentials

J. Pavlů; Z. Němeček; J. Šafránková; Ivo Čermák

The presence of dust grains is a common phenomenon in the space environment. Grains can be charged by many different processes (e.g., photoemission, attachment of electrons/ions, the secondary emission, etc.). If the grains surface potential becomes high enough, one can observe field emission of ions or electrons. We are trapping a single dust grain in a Paul trap, expose it to a low-energy electron beam, and investigate the evolution of its charge-to-mass ratio with respect to the energy of primary electron beam. We use micron-sized (D = 2–11 μm) glass grains and charge them up to -300 V of surface potentials; it corresponds to the electric field strength of about 108 V/m. Analysis of the charging/discharging processes has shown that (1) the effect of the field enhanced secondary emission is negligible in the case of insulators and (2) the effective work function for electron field emission from charged insulators is as low as ≈ 1 eV.


Review of Scientific Instruments | 2012

Linear trap with three orthogonal quadrupole fields for dust charging experiments

Martin Beranek; Ivo Čermák; Z. Němeček; J. Šafránková; Martin Jeřáb; J. Pavlů

Investigations of charging processes on a single dust grain under controlled conditions in laboratory experiments are the unique way to understand the behavior of dust grains in complex plasma (in space, in laboratory, or in technological applications). An electrodynamic trap is often utilized for both holding a single grain and continuously measuring its charge-to-mass ratio. We propose a modified design of the linear quadrupole trap with the electrodes split into two parts; each of them being supplied by a designated source. The paper presents basic calculations and the results of the trap prototype tests. These tests have confirmed our expectations and have shown that the suggested solution is fully applicable for the dust charging experiments. The uncertainty of determination of the dust grain charge does not exceed 10(-3). The main advantages of the suggested design in comparison with other traps used for dust investigations can be summarized as: The trap (i) is more opened, thus it is suitable for a simultaneous application of the ion and electron beams and UV source; (ii) facilitates investigations of dust grains in a broader range of parameters; and (iii) allows the grain to move along the axis in a controlled way.


Solar System Research | 2015

PLASMA-F experiment: Three years of on-orbit operation

L. M. Zelenyi; G. N. Zastenker; A. Petrukovich; L. S. Chesalin; V. N. Nazarov; V. Prokhorenko; J. Balaz; K. Kudela; I. Strgarski; M. Slivka; V. A. Gladyshev; I. P. Kirpichev; E. T. Sarris; T. Sarris; E. V. Lakutina; L. K. Minskaya; E. V. Krukovskaya; A. V. Beznos; Y. I. Markov; A. E. Tretyakov; O. V. Batanov; F. V. Korotkov; A. P. Melnik; V. V. Konoplev; A. D. Ryabova; E. V. Gevorkova; M. V. Klimenchenko; A. G. Bazhenov; I. E. Belova; E. A. Gavrilova

Composition and tasks of the PLAZMA-F experiment onboard the SPEKTR-R satellite are described in this paper. A record high time resolution is a feature of solar wind plasma flux and energetic particle flux measurements. It allowed detecting a number of new and significant properties and parameters.


DUSTY PLASMAS IN THE NEW MILLENNIUM: Third Conference on the Physics of Dusty Plasmas | 2002

Secondary Emission From Small Spherical Grains

Zdenek Nemecek; Jiri Pavlu; J. Šafránková; Ivana Richterova; Ivo Čermák

A number of phenomena connected with dust grains within the solar system can be explained by their electric charging. In the presented paper, we discuss the influence of the grain diameter on the changes of equilibrium potential of spherical grains from glass and pure SiO 2 in a laboratory experiment which is based on the levitation of a single dust grain in the AC electric field of a quadrupole. The yield of secondary emission derived from the measurements exhibits a strong dependence on the grain diameter. For larger grains, it reveals the properties of planar surfaces, whereas it can be higher for one micron grains and 10 keV of the primary beam energy. The rise of the secondary emission yield was attributed to the emission from the “back side” of the grain which starts when the penetration depth of primary electrons becomes comparable with the grain size. The results are discussed in view of present models of this process and several correction of the models are suggested.


Space Science Reviews | 2013

Fast Solar Wind Monitor (BMSW): Description and First Results

J. Šafránková; Z. Němeček; L. Přech; G. N. Zastenker; Ivo Čermák; Lev Chesalin; Arnošt Komárek; Jakub Vaverka; Martin Beranek; J. Pavlů; Elena Gavrilova; Boris Karimov; Arkadii Leibov

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J. Šafránková

Charles University in Prague

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Z. Němeček

Charles University in Prague

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J. Pavlů

Charles University in Prague

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G. N. Zastenker

Russian Academy of Sciences

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Ivana Richterova

Charles University in Prague

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Jiri Pavlu

Charles University in Prague

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Martin Beranek

Charles University in Prague

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Zdenek Nemecek

Charles University in Prague

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L. S. Chesalin

Russian Academy of Sciences

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L. Přech

Charles University in Prague

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