Cylindrical Electrostatic Analyzer Research Articles

SE OF COLLIMATION REGIME OF CHARGED PARTICLE BEAM FOR EXPAND THE FUNCTIONAL CAPABILITIES OF CORPUSCULAR OPTICAL SYSTEMS

The approach for the modeling of corpuscular-optical systems for the analysis of charged particle flows is considered. For all the methods considered and used earlier, the condition of spatial focusing of the particle beam was required. However, this strict condition is not always feasible in combination with other requirements. When a cylindrical electrostatic mirror analyzer is used as the main element, spatial focusing ofthe beam is incompatible with focusing in time of flight in terms of energy. In the paper the possibility of using the collimation regime of charged particle beam is considered, thereby eliminating the need to fulfill the focusing condition.

Полевая электронная спектроскопия оксидных катодов

The results of studying the bulk and surface electronic structure of a graphite-oxide field cathode and an oxide thermal cathode using a cylindrical electrostatic dispersive energy analyzer are presented. Oxides based on ternary carbonate of alkaline earth metals were used. The energy spectra of electrons in the auto- and thermal automodes are obtained, and the possibility of studying the energy electronic band structure of an oxide thermal cathode by the method of field electron spectroscopy is shown.

A Coaxial Cylindrical Electrostatic Electronic Energy Analyzer (Spiratron) and Its Characteristics

A Coaxial Cylindrical Electrostatic Electronic Energy Analyzer (Spiratron) and Its Characteristics

Plasma potential and fluctuations measurements by HIBD with 90° cylindrical energy analyzer on the ISTTOK tokamak

The Heavy Ion Beam Diagnostic (HIBD) is known as unique tool for direct measurements of plasma potential in fusion devices such as tokamaks and stellarators. On small ISTTOK tokamak (R = 0.45 m, a = 0.085 m, B = 0.5 T, Ip = 4 kA, <ne> = 4 × 1018 m−3) the HIBD is operated with primary Xe+ ion beam with E = 22−24 keV of energy and a Multiple Cell Array Detector (MCAD) to measure the product of plasma neσ and its fluctuations simultaneously at a number of sample volumes along primary beam trajectory across the plasma. To upgrade the ISTTOK HIBD capabilities to measure the plasma potential and its fluctuations a multichannel 90° cylindrical electrostatic energy analyzer (CEA) operated in a beam deceleration mode has been proposed.This paper presents the first results of the plasma potential and its fluctuations measurements by the one-channel CEA prototype operated in two-times deceleration mode and in real conditions of the HIBD experiments on ISTTOK. Using an indirect CEA calibration approaches, the value of the potential Φ ∼ −350 V has been measured in the plasma core. Also, the plasma potential fluctuations Φ∼ ∼ 40 V have been observed. The obtained results demonstrate and confirm the applicability of the 90° cylindrical electrostatic energy analyzer and its operation in deceleration mode for the plasma potential and its fluctuations measurements by HIBD.

Ion charge state and energy distributions of laser produced plasma from pure metals and their alloy.

A high intensity highly charged laser ion source has been studied at the Institute of Modern Physics for the last few years. In order to investigate the processes of plasma heating and expansion of laser produced plasma, the charge state and energy distributions of the ions from pure copper, silver, and copper-silver alloy, in which the atom number ratio between copper and silver is 2:3, were measured with a 90° cylindrical electrostatic ion analyzer. It was shown that the yields of highly charged copper ions from the pure copper target are higher compared with those of the alloy target. In contrast, higher yields of highly charged silver ions were obtained from the copper-silver alloy target. Moreover, the ion energy distributions were derived from the time-of-flight spectra for the ions with different ion charge states and compared between the pure metal and alloy targets.

Design and optimization of the electrostatic input module for the ISTTOK Tokamak HIBD cylindrical energy analyzer

The Heavy Ion Beam Diagnostic of the ISTTOK Tokamak is based on the injection of a single ionized primary beam (Xe+, Cs+) of energy 20–25 keV and on the collection of all doubly ionized ions emerging from the primary beam due to the impact ionization with the plasma electrons. In the present configuration three local plasma parameters can be retrieved: plasma density (ne), electron temperature (Te), and poloidal magnetic field (Bp). A new detection system is being design in order to determine the plasma potential (Vp) profile via the secondary ions energy measurements. To that end an improved 90̂ cylindrical electrostatic analyzer (CEA) has been designed and optimized to measure the energy of the secondary ions. This paper reports on the design optimization of the input stage of the new detection arrangement to guide and shape 4 secondary beams into the entrance of the CEA. It is composed of a set of four electrostatic cylindrical plates followed by four pairs of steering plates and a multiple aperture Einzel-like electrostatic lens, consisting of four planar vertical electrodes containing four passing slits. Individual secondary beams with dimension of 8 mm × 2.5 mm were obtained without overlapping between the four beams from different slits. By changing the incident beam energy from 20 keV to 20.2 keV (in order to simulate a local plasma potential value of +200 V), without adjusting bias voltage of the input system, results in a vertical beam shift of 1 mm which can be recovered by changing the voltage on the parallel plate arrangement by 40 V. The flexibility and tolerance of the optic system was tested successfully for the expected angular uncertainty of the beam by +/−0.5̂ at the input module entrance and with the expected energy spread of the beam corresponding to different plasma positions inside the tokamak.

Energy spectrum of electrons transmitted through curved dielectric tubes

The transmission coefficients and the energy spectra of electrons with an energy of 10–20 keV transmitted through curved glass and polyurethane tubes are measured with a cylindrical electrostatic analyzer. The spectra of X-ray excited by these electrons at the tube outlet are also measured. At larger beamdeflection angles, the spectral distribution of electrons at the curved tube outlet expands considerably, and the maxima of the spectral curves shift toward lower energies. The obtained results suggest that electrons propagating within a curved tube lose energy in the process of inelastic collisions with walls. The transmission coefficient, which is determined by measuring the electron current at the tube inlet and at its outlet, depends only slightly on the electron energy (in the studied energy range) and drop by a factor of more than two when the deflection angle is increased from 0° to 90°.

Development of a laser ion source for production of high-intensity heavy-ion beams

A laser ion source has been developed as a high-intensity source for the ion implanter and the single pulsed beam of the azimuthally varying field cyclotron at TIARA. Highly charged beams of C5+ and C6+ ions and low-charged beams of heavy ions such as C, Al, Ti, Cu, Au, and Pt are required for the single-pulse acceleration in the cyclotron and for the ion implanter, respectively. In the vacuum chamber of the ion source, a target holder on a three-dimensional linear-motion stage provides a fresh surface for each laser shot. A large-sized target with a maximum size of 300mm×135mm is mounted on the holder for long-term operation. The ion current (ion charge flux) in the laser-produced plasma is measured by a Faraday cup and time-of-flight spectra of each charge state are measured using a 90° cylindrical electrostatic analyzer just behind the Faraday cup. Carbon-plasma-generation experiments indicate that the source produces intense high- and low-charged pulsed ion beams. At a laser energy of 483mJ (2.3×1013W/cm2), average C6+ current of 13mA and average C5+ current of 23mA were obtained over the required time duration for single-pulse acceleration in the cyclotron (49ns for C6+ and 80ns for C5+). Furthermore, at 45mJ (2.1×1012W/cm2), an average C2+ current of 1.6mA over 0.88μs is obtained.

Numerical Simulation of the Geometric Factor of a Cylindrical Electrostatic Analyzer to Monitor Electron Precipitation in the South Atlantic Magnetic Anomaly

This paper simulates the performance of a cylindrical electrostatic analyzer specially devised to measure the energy spectra of electrons precipitating in the South Atlantic Magnetic Anomaly (SAMA). Unlike its counterparts built to operate in the auroral region, the dimensions of this analyzer were designed to maximize the geometric factor, and to be the first experiment dedicated to measure the much lower fluxes in the equatorial ionosphere. The geometric factor of the analyzer was calculated based on the numerical simulation of electron trajectories coming from a calibration beam using the package SIMION 8.0. Positive and negative voltages applied to the inner and outer plates were compared to examine the analyzer’s response, showing small but visible differences. Simulations at the lower and higher ends of the energy spectrum showed similar geometric factors [ $G$ ] as expected with $[G]/E_{\mathrm {peak}} \sim 2.9\times 10^{\mathrm {-3}}$ (cm $^{2}\cdot {\mathrm{ sr}}$ ) and $\Delta E/E_{\mathrm {peak}} \sim 0.29$ . These results are in good agreement with semianalytical and empirical estimates. Comparisons with two analyzers designed for measurements in the auroral region showed that the simulated geometric factors are about one order of magnitude larger. Flux estimates based on aeronomic effects over the SAMA indicate that the number of counts should be sufficiently above noise level with the present analyzer design.

A Satellite-borne Miniature Ion Mass Spectrometer for Space Plasma

The miniature design technology is an important trend in space exploration. Mass spectrometer is used extensively in the space environment detection. The miniature ion mass spectrometer utilizes a 127° cylindrical electrostatic analyzer accompanied with a Time of Flight (TOF) unit based on ultrathin carbon foil to measure the energy spectra and composition of space plasma. The Time of Flight technique has been used broadly in space plasma measurement. A new type of miniature method for the ion mass spectrometer is introduced. The total mass of the instrument is 1.8 kg and the total power consumption is 2.0W. The calibration results show that the energy measurement range is 8.71～43550eV, the energy resolution is 1.86% and the ion mass from 1 amu (1 amu = 1.67 × 10^-27 kg) to 58 amu can be resolved by the miniature mass spectrometer. The miniature ion mass spectrometer also has a potential to be increased in the field of view by an electrostatic deflecting system to extend its application in space plasma detection. The miniature ion mass spectrometer has been selected for pre-study of Chinese Strategic Priority Research Program on Space Science.

A Two-dimensional event-counting detector for HV-CSA electrostatic analyzer at SpLine the Spanish CRG beamline at the ESRF

A novel 2D-detector has been designed, manufactured and installed on the high voltage cylindrical sector electrostatic analyzer (HV-CSA300/15) of the HAXPES station of SpLine the Spanish CRG beamline at the ESRF. This original 2D-detector constitutes an important improvement of the HAXPES station. A drawback of electrostatic analyzer in HAXPES, is that the electron counter must be raised to high voltages (up to 15 kV). Hence the development of a 2D detector system compatible with a high voltage electrostatic analyzer is a scientific instrumentation challenge. The developed two-dimensional event-counting detector consists of a 2D image intensifier (combination of scintillating screen and MCP) optically coupled with a CMOS-camera and a data processing system. The accumulated event image is transferred to the image processing software on the PC, where the events are classified by their position to give single detector readout. The energy window accepted by the area detector ranges from 100 meV to 50 eV, depending on the analyzer pass energy. Hence, for single shot measurements, i.e, without sweeping the pre-retarding lens voltages up to 200 detector channels can be used compared to a single channel. This results in a gain of the analyser transmission of at least a factor of 20. Thus we overcome the limitations imposed by the low count rate when dealing with high excitation energies and high kinetic-energy electrons.

Nickel plasma produced by 532-nm and 1064-nm pulsed laser ablation

A comparison between laser ablation of nickel in vacuum by using 532-and 1064-nm Nd:YAG (Yttrium Aluminium Garnet) laser wavelengths, with an intensity of 5 × 109 W/cm2, is reported. Nanosecond pulsed ablation produces high nonisotropic emission of neutrals and ionic species. For 532-nm laser irradiation, mass quadrupole spectrometry, coupled to electrostatic ion deflection and time-of-flight measurements, allows estimation of the energy distributions of the emitted species from plasma. For 1064-nm laser ablation, a cylindrical electrostatic ion analyzer permits one to measure the yield and the charge state of the emitted ions and reconstruct the ion energy and charge state distributions. Neutrals show typical Boltzmann-like distributions, while ions show Coulomb-Boltzmann-shifted distributions depending on their charge state. Surface profiles of the ablated craters permitted study of the ablation threshold and yields of nickel in vacuum versus the laser fluence. The plasma temperature was evaluated using experimental data. Special regard is given to the ion acceleration process occurring inside the plasma due to the high electrical field generated at nonequilibrium plasma conditions and the angular distribution of the emitted species.

Miniature ion mass analyzer

The Swedish Institute of Space Physics is developing a miniature plasma analyzer for planetary missions (MIPA—Miniature ion precipitation analyzer). MIPA has been accepted to fly on-board both the ESA BepiColombo mission to Mercury (2014) and the Indian Chandrayaan—1 mission to the Moon (2007). The analyzer measures ions in the energy range 10 eV–15 keV and has a sufficient mass resolution to resolve the main groups of ions, namely M / q = 1 , 2 , 4 , 8 , 16 , > 30 . Field of view is 9 ∘ × 180 ∘ . The instrument consists of the sensor head and a separate electronic board whose total mass is 300 g. The sensor head envelope is roughly 53 × 85 × 30 mm 3 in volume and is designed for the extreme operation temperature range of - 100 to + 125 ∘ C . MIPA comprises an electrostatic scanner for angular resolution, a cylindrical electrostatic analyzer for energy discrimination and a time-of-flight (TOF) section for particle velocity measurement. Generic design allows using the instrument on various platforms including nano-satellite and multi-spacecraft missions. This document describes the design of the sensor part including ion optical as well as mechanical aspects.

Coherent error study in a retarding field energy analyzer

A novel cylindrical retarding electrostatic field energy analyzer for low-energy beams has been designed, simulated, and tested with electron beams of several keV, in which space charge effects play an important role. A cylindrical focusing electrode is used to overcome the beam expansion inside the device due to space-charge forces, beam emittance, etc. In this paper, we present the coherent error analysis for this energy analyzer with beam envelope equation including space charge and emittance effects. The study shows that this energy analyzer can achieve very high resolution (with relative error of around 10 −5) if taking away the coherent errors by using proper focusing voltages. The theoretical analysis is compared with experimental results.

Review of laser ion sources developments in Prague and production of q over 50+ ions at Prague Asterix Laser System (invited)

The high-power iodine laser systems PERUN and Prague Asterix Laser System, with a maximum attainable laser intensity IL of up to about 6×1016 W/cm2, were used to generate highly charged ions of various elements (Al,Co,Ni,Cu,Ag,Sn,Ta,W,Pt,Au,Pb,Bi). The properties of ions were investigated mainly on the basis of time-of-flight method using ion collectors, cylindrical electrostatic ion energy analyzer, Thomson parabola spectrometer, and track detectors. Simultaneous x-ray and interferometric measurements were also implemented. Maximum ion charge states of heavy ions above z=50+ were recorded and the maximum energy of emitted ions exceeded Ei=22 MeV. Using laser intensities of about 1×1016 W/cm2 can produce such ions. Due to the convenient pulse length of the iodine laser, part of the pulse may interact with the self-created expanding plasma. It was proved that in this case the conditions for an appearance of the relativistic self focusing may be fulfilled (position of minimum focus spot in front of the target surface and the threshold laser intensity about 3×1014 W/cm2) and the highest charge states above 50+ may be generated, too.

Tungsten ions produced by infrared pulsed laser irradiation

Energetic ions have been obtained irradiating a tungsten target with a Q-switched Nd:Yag laser, 1064 nm wavelength, 9 ns pulse width, 900 mJ maximum pulse energy and power density of the order of 1010 W/cm2. The laser-target interaction induces a strong metal etching with production of plasma in front of the target. The plasma contains neutrals and ions with high charge state. Time-of-flight measurements are presented for qualitative analysis of the ion production. A cylindrical electrostatic ion analyzer permits measuring of the yield of emitted ions, the charge state of detected ions and the ion energy distribution. Measurements indicate that, at a laser fluence of the order of 100 J/cm2, the charge state may reach 9+ and the ion energy reaches about 5 keV. The ion energy distribution is given as a function of the charge state. Experimental results indicate that an electrical field is developed along the normal to the plane of the target surface, which accelerates the ions up to high velocity. The ion velocity distributions follow a “shifted Maxwellian distribution”, which the author has corrected for the Coulomb interactions occurring inside the plasma.

Tantalum ions produced by 1064 nm pulsed laser irradiation

A Q-switched Nd:YAG (yttrium aluminum garnet) laser (1064 nm wavelength) with a 9 ns pulse width, 1–900 mJ pulse energy, and 0.5 mm2 target spot, is employed to irradiate tantalum targets in vacuum. The irradiation produces a strong etching of the metal and forms a plasma in front of the target. The plasma contains neutrals and ions with a high charge state and a wide energy distribution. Time-of-flight measurements are presented for the ionic production. A cylindrical electrostatic ion analyzer permits to measure the yield and the charge state of the emitted ions and to extrapolate the ion energy distribution as a function of the laser fluence in the range 10–100 J/cm2. The measurements indicate that at high laser fluence the tantalum charge state may reach 8+ and the maximum ion energy about 6 keV. The ion energy distribution is presented as a function of the charge state. It follows approximately a “shifted Maxwellian distribution.” A better theoretical approach has been further developed considering the Coulomb interactions occurring inside the plasma, which produce ion acceleration at velocities comparable with thermal ones, according to the so-called “shifted Maxwellian-Coulombian distribution.”

Characteristics of 63.6° cylindrical energy analyzer used as charge exchange neutral particle analyzer

A charge exchange neutral particle analyzer including a newly designed multichannel 63.6° cylindrical electrostatic energy analyzer was constructed. Since the energy analyzer can simultaneously adopt a small radius of cylindrical electrodes and a large width of an entrance slit, high incident current can be analyzed while the size of the analyzer remain compact. Characteristics of the analyzer were investigated using hydrogen beam with energies from about 0.5 to 5 keV. The experimental results are compared well with the numerical analysis.

A multidetection, multicoincidence spectrometer for (e,2e) and (e,3e) electron impact ionization measurements

A new spectrometer for the coincidence study of (e,2e) single ionization, and e,(3-1)e or (e,3e) double ionization by electron impact is described. The system is based on two double toroidal analyzers for the ejected electrons and a cylindrical electrostatic analyzer for the scattered electrons. It allows angular and energy distributions of the ejected electrons to be measured over almost the totality of the collision plane, using dual two-dimensional position sensitive detectors. The design and operation of the spectrometer is described with a special emphasis on the imaging properties of the system. The performance (energy and angular resolutions,…) and the calibration of the spectrometer are discussed and sample results for (e,2e), e,(3-1)e and (e,3e) experiments on the rare gases are presented.

Multiply charged ions from iodine laser-produced plasma of medium- and high-Z targets

Maximum charge states of ions registered in the far expansion zone from laser-produced plasma of Al, Co, Ni, Cu, Ta, W, Pt, Au, Pb, and Bi are presented. The Thomson parabola spectrometer was used to display a general view of the ion species of an expanding plasma while detailed ion charge-energy spectra were determined by the cylindrical electrostatic ion energy analyzer. The current densities of highly charged ion groups above 20 mA/cm2 were measured by use of an ion collector at a distance of ∼1 m from the target. The photodissociation iodine laser system PERUN (λ = 1.315 μm, power density up to ∼1015 W cm−2) was employed as a driver.