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The Pulsed Energetic Electrons for Research (PEER) beamline at the ANSTO Australian Synchrotron comprises a 100 MeV linac injector that is currently being developed for ultra-high dose-rate, very high-energy electron radiotherapy research. Previously, dosimetry studies discovered a lack of reliable charge measurement to the in-air end station, though no change in response was recorded in fast current transformer measurements, the only available diagnostic device for measuring charge. This work describes the process of simulating and then commissioning a purpose-built Faraday cup to ascertain absolute in-air charge measurements at PEER. By combining simulation data with experimental results, the PEER Faraday cup is shown to possess a primary electron capture efficiency of (99.22 ± 0.10)%, with a net capture efficiency due to secondary electron emission of (97.87 ± 0.24)%. These results show the PEER Faraday cup performs as intended and, when scaled against simulations, will be suitable for measuring absolute charge at PEER. [ABSTRACT FROM AUTHOR]

The Pulsed Energetic Electrons for Research (PEER) beamline at the ANSTO Australian Synchrotron comprises a 100 MeV linac injector that is currently being developed for ultra-high dose-rate, very high-energy electron radiotherapy research. Previously, dosimetry studies discovered a lack of reliable charge measurement to the in-air end station, though no change in response was recorded in fast current transformer measurements, the only available diagnostic device for measuring charge. This work describes the process of simulating and then commissioning a purpose-built Faraday cup to ascertain absolute in-air charge measurements at PEER. By combining simulation data with experimental results, the PEER Faraday cup is shown to possess a primary electron capture efficiency of (99.22 ± 0.10)%, with a net capture efficiency due to secondary electron emission of (97.87 ± 0.24)%. These results show the PEER Faraday cup performs as intended and, when scaled against simulations, will be suitable for measuring absolute charge at PEER.

Objective. Ionization chambers, mostly used for beam calibration and for reference dosimetry, can show high recombination effects in pulsed high dose rate proton beams. The aims of this paper are: first, to characterize the linearity response of newly designed asymmetrical beam monitor chambers (ABMC) in a 100–226 MeV pulsed high dose rate per pulse scanned proton beam; and secondly, to calibrate the ABMC with a PPC05 (IBA Dosimetry) plane parallel ionization chamber and compare to calibration with a home-made Faraday cup (FC). Approach. The ABMC response linearity was evaluated with both the FC and a PTW 60019 microDiamond detector. Regarding ionometry-based ABMC calibration, recombination factors were evaluated theoretically, then numerically, and finally experimentally measured in water for a plane parallel ionization chamber PPC05 (IBA Dosimetry) through k s saturation curves. Finally, ABMC calibration was also achieved with FC and compared to the ionometry method for 7 energies. Main results. Linearity measurements showed that recombination losses in the new ABMC design were well taken into account for the whole range of the machine dose rates. The two-voltage-method was not suitable for recombination correction, but Jaffé's plots analysis was needed, emphasizing the current IAEA TRS-398 reference protocol limitations. Concerning ABMC calibration, FC based absorbed dose estimation and PPC05-based absorbed dose estimation differ by less than 6.3% for the investigated energies. Significance. So far, no update on reference dosimetry protocols is available to estimate the absorbed dose in ionization chambers for clinical high dose rate per pulse pulsed scanned proton beams. This work proposes a validation of the new ABMC design, a method to take into account the recombination effect for ionometry-based ABMC calibration and a comparison with FC dose estimation in this type of proton beams. [ABSTRACT FROM AUTHOR]

The feasibility of measuring the surface potential decay of polystyrene (PS) film is investigated at room temperature by using Kelvin probe force microscopy (KPFM). The PS film was charged by an ion injection method utilizing Bruker's atomic force microscope (AFM) Nanoman module with a pulse duration of 1 ms, SCM‐PIT electrically conductive probe, and a voltage pulse of −250 mV. The surface potential decayed linearly on a semi‐log scale with time, where the time decay constant was quantified for relative humidity (RH) = 5% by KPFM at room temperature. The surface potential decayed due to the interaction of the PS film with the hydronium ions available in the environment. Furthermore, the effect of the material forms (film vs. microspheres) on the time decay constant at RH = 5% was investigated. The time decay constants measured using different methods exhibited excellent correlation with the AFM‐KPFM. This also confirmed that the results are independent of the material form (microspheres vs. film form). As a result, the proposed method can be used to measure the effect of RH for any PS surface (i.e., particles of various sizes and films) exposed to these environmental conditions. [ABSTRACT FROM AUTHOR]

Background: A Faraday cup (FC) facilitates a quite clean measurement of the proton fluence emerging from clinical spot‐scanning nozzles with narrow pencil‐beams. The utilization of FCs appears to be an attractive option for high dose rate delivery modes and the source models of Monte‐Carlo (MC) dose engines. However, previous studies revealed discrepancies of 3%–6% between reference dosimetry with ionization chambers (ICs) and FC‐based dosimetry. This has prevented the widespread use of FCs for dosimetry in proton therapy. Purpose: The current study aims at bridging the gap between FC dosimetry and IC dosimetry of proton fields delivered with spot‐scanning treatment heads. Particularly, a novel method to evaluate FC measurements is introduced. Methods: A consistency check is formulated, which makes use of the energy balance and the reciprocity theorem. The measurement data comprise central‐axis depth distributions of the absorbed dose of quasi‐monochromatic fields with a width of about 28.5 cm and FC measurements of the reciprocal fields with a single spot. These data are complemented by a look‐up of energy‐range tables, the average Q‐value of transmutations, and the escape energy carried away by neutrons and photons. The latter data are computed by MC simulations, which in turn are validated with measurements of the distal dose tail and neutron out‐of‐field doses. For comparison, the conventional approach of FC evaluation is performed, which computes absorbed dose from the product of fluence and stopping power. The results from the FC measurements are compared with the standard dosimetry protocols and improved reference dosimetry methods. Results: The deviation between the conventional FC‐based dosimetry and the IC‐based one according to standard dosimetry protocols was −4.7 (±$\pm$ 3.3)% for a 100 MeV field and −3.6 (±$\pm$3.5)% for 200 MeV, thereby agreeing within the reported uncertainties. The deviations could be reduced to −4.0 (±$\pm$ 2.9)% and −3.0 (±$\pm$ 3.1)% by adopting state‐of‐the‐art reference dosimetry methods. The alternative approach using the energy balance gave deviations of only −1.9% (100 MeV) and −2.6% (200 MeV) using state‐of‐the‐art dosimetry. The standard uncertainty of this novel approach was estimated to be about 2%. Conclusions: An alternative concept has been established to determine the absorbed dose of monoenergetic proton fields with an FC. It eliminates the strong dependence of the conventional FC‐based approach on the MC simulation of the stopping‐power and of the secondary ions, which according to the study at hand is the major contributor to the underestimation of the absorbed dose. Some contributions to the uncertainty of the novel approach could potentially be reduced in future studies. This would allow for accurate consistency tests of conventional dosimetry procedures. [ABSTRACT FROM AUTHOR]

Background: Experiments with ultra‐high dose rates in proton therapy are of increasing interest for potential treatment benefits. The Faraday Cup (FC) is an important detector for the dosimetry of such ultra‐high dose rate beams. So far, there is no consensus on the optimal design of a FC, or on the influence of beam properties and magnetic fields on shielding of the FC from secondary charged particles. Purpose: To perform detailed Monte Carlo simulations of a Faraday cup to identify and quantify all the charge contributions from primary protons and secondary particles that modify the efficiency of the FC response as a function of a magnetic field employed to improve the detector's reading. Methods: In this paper, a Monte Carlo (MC) approach was used to investigate the Paul Scherrer Institute (PSI) FC and quantify contributions of charged particles to its signal for beam energies of 70, 150, and 228 MeV and magnetic fields between 0 and 25 mT. Finally, we compared our MC simulations to measurements of the response of the PSI FC. Results: For maximum magnetic fields, the efficiency (signal of the FC normalized to charged delivered by protons) of the PSI FC varied between 99.97% and 100.22% for the lowest and highest beam energy. We have shown that this beam energy‐dependence is mainly caused by contributions of secondary charged particles, which cannot be fully suppressed by the magnetic field. Additionally, it has been demonstrated that these contributions persist, making the FC efficiency beam energy dependent for fields up to 250 mT, posing inevitable limits on the accuracy of FC measurements if not corrected. In particular, we have identified a so far unreported loss of electrons via the outer surfaces of the absorber block and show the energy distributions of secondary electrons ejected from the vacuum window (VW) (up to several hundred keV), together with electrons ejected from the absorber block (up to several MeV). Even though, in general, simulations and measurements were well in agreement, the limitation of the current MC calculations to produce secondary electrons below 990 eV posed a limit in the efficiency simulations in the absence of a magnetic field as compared to the experimental data. Conclusion: TOPAS‐based MC simulations allowed to identify various and previously unreported contributions to the FC signal, which are likely to be present in other FC designs. Estimating the beam energy dependence of the PSI FC for additional beam energies could allow for the implementation of an energy‐dependent correction factor to the signal. Dose estimates, based on accurate measurements of the number of delivered protons, provided a valid instrument to challenge the dose determined by reference ionization chambers, not only at ultra‐high dose rates but also at conventional dose rates. [ABSTRACT FROM AUTHOR]

The plasma focus device is a simple, inexpensive, and precious device that can be considered as a source of high-energy ions for researches relevant to interactions of ions with widely used materials such as titanium. Regarding exclusive properties such as a high degree of hardness and resistance to corrosion, titanium nitride alloy is considered to be one of the most essential materials with a wide range of industrial applications. In the present study, the characteristics of titanium nitride alloys were studied using a 1.5 kJ Mather-type plasma focus device. To do this, a Faraday cup detector is used to measure the current density of the ion beam in order to determine the energy spectrum of nitrogen ions using time of flight approach. The optimal operational condition of the device for nitrogen ions emission, in terms of gas pressure and voltage of discharge were also determined. Titanium samples were situated on the top of the anode of the device and were exposed to nitrogen ion radiation considering 5, 10, and 20 shots of the device. To simulate the penetration depth of nitrogen ions inside the titanium samples, the SRIM code is used. The obtained energy of ions from the time of flight technique was set as input of the SRIM code, and it was found that nitrogen ions, with an average energy of 50 keV can penetrate about 110 nm inside the titanium sample. It was understood that the finding results of the penetration depth are in good agreement with the SEM micrographs of the titanium samples. The sputtering yield of titanium atoms was determined using the SRIM simulation code, and it was found that the yield of the surface of the samples is less than 0.2 atoms per individual nitrogen atom.

Triboelectrification between a liquid and a solid is a common phenomenon in our daily life and industry. Triboelectric charges generated at liquid/solid interfaces have effects on energy harvesting, triboelectrification-based sensing, interfacial corrosion, wear, lubrication, etc. Knowing the amount of triboelectric charge transfer is very useful for studying the mechanism and controlling these phenomena, in which an accurate method is absolutely necessary to measure the triboelectric charge generated at the solid—liquid interface. Herein, we established a method for measuring the charge transfer between different solids and liquids. An equipment based on the Faraday cup measurement was developed, and the leakage ratio (rl) was quantified through simulation based on an electrostatic field model. Typical experiments were conducted to validate the reliability of the method. This work provides an effective method for charge measurement in triboelectrification research. [ABSTRACT FROM AUTHOR]

Beam diagnostics is one of the main tasks during the operation of charged particle accelerators. The work presents the concept of a beam instrumentation system that provides diagnostic procedures and allows measurement and adjustment of the key beam parameters in a linear resonant proton accelerator of the DARIA compact neutron source: current, position, profile, emittance, energy, and phase characteristics. An important requirement is to carry out measurements during the accelerator adjustment procedure, when the beam parameters can be changed in a wide range. It is proposed to include in the main structure of the system such types of diagnostic devices as beam current transformers, stripline beam position monitors, wire scanners, ionization beam cross-section monitor, slit emittance meter, bunch shape monitor, and a water-cooled Faraday cup. Particular attention is paid to nondestructive methods of diagnostics taking into account a high pulse and average beam intensity in conjunction with a relatively low beam energy to provide continuous operational control of the beam parameters. The main physical principles of operation, typical characteristics, as well as features of the practical implementation of the devices are included. The possible layout of diagnostic units in the accelerator is proposed, taking into account the peculiarities of using the proposed types of detectors in various parts of the accelerator. [ABSTRACT FROM AUTHOR]

Abstract Triboelectrification between a liquid and a solid is a common phenomenon in our daily life and industry. Triboelectric charges generated at liquid/solid interfaces have effects on energy harvesting, triboelectrification-based sensing, interfacial corrosion, wear, lubrication, etc. Knowing the amount of triboelectric charge transfer is very useful for studying the mechanism and controlling these phenomena, in which an accurate method is absolutely necessary to measure the triboelectric charge generated at the solid—liquid interface. Herein, we established a method for measuring the charge transfer between different solids and liquids. An equipment based on the Faraday cup measurement was developed, and the leakage ratio (r l) was quantified through simulation based on an electrostatic field model. Typical experiments were conducted to validate the reliability of the method. This work provides an effective method for charge measurement in triboelectrification research.

A magnetically insulated transmission line (MITL) is an inevitable choice for ultra-high power density energy transmissions. Its working process is complex, with an obvious influence on the working process of electron beam diodes and other load devices. The power coupling process of an electron beam diode driven by an MITL is a difficult problem in pulse power applications. No research is available on the electron beam characteristics of its anode. In this paper, a fast time response full absorption Faraday cup was developed. An intense electron beam measurement waveform showing the multi-stage characteristics was obtained through measurements using the Faraday cup absorber as the anode of the electron beam diode. The stage characteristics of the beam were in good agreement with the vacuum transmission, magnetic insulation formation, and multi-stage process of the stable magnetic insulation. The beam intensity corresponded with the conduction current of the cathode. It was obviously smaller than the current of the anode. The results reflected the influence of the different processes of the magnetic insulation on the transmission line on the beam waveforms in the diode area and provided a reference for the power transmission of the power device and the load system design. [ABSTRACT FROM AUTHOR]

In this research, the effect of ions produced in deuterium plasma on Tungsten (W) and Aluminum (Al) plates has been investigated using a plasma focus device with the specifications of (C=10.4 μF, V=23 kV, E=2.75 kJ). The W samples used because it is one of the key elements in the Tokamak device. Because we wanted to put the W samples at the distance from the anode top with maximum plasma produced ions, we should find the optimum place. Due to the high cost of W samples, we used Al samples to find the optimal conditions. The samples were irradiated at 8 cm distance from the anode top with deuterium ions produced by a plasma focus device. The sample analyses were done by the SEM and EDX methods. The sample irradiation by deuterium plasma ions caused a lot of damages and bubble formation on the sample surfaces. The analyses showed the extent of surface damage and the number of ions deposited on the surface. The number of damages on the Al surface was much higher than W. Bubbles were formed on the surface were due to the impact of deuterium ions on the W and Al samples. Also, the deuterium ion energy was measured with a Faraday cup as about 50 keV. [ABSTRACT FROM AUTHOR]

This paper presents the experimental results on electron, ion temperatures and densities in a pulsed plasma accelerator. The values of electron densities and temperatures were computed using the methods of relative intensities of Hα and Hβ lines, Hβ Stark broadening, and the technique is based on Faraday cup beam current measurements. In this work, a linear optical spectrometer S-100 was used to acquire the emission spectra of hydrogen and air plasmas. In this spectrum, there are some lines due to Fe, Cu, N2, O2, and H2. The series of visible lines in the hydrogen atom spectrum are named the Balmer series. The spectral emissions of iron and copper occur throughout the gas breakdown and ignition of an arc discharge, during the erosion and sputtering of materials. The vacuum chamber and coaxial electrodes were made. The electron temperatures and densities in a pulsed plasma accelerator, measured via relative intensities of spectral lines and Stark broadening, at a charging voltage of a capacitor bank of 3 kV and a working gas pressure in a vacuum chamber of 40 mTorr, were 2.6 eV and 1.66 · 1016 cm−3 for hydrogen plasma. These results were compared with the Faraday cup beam current measurements. However, no match was found. Considering and analyzing this distinction, we concluded that the spectral method of plasma diagnostics provides more accurate results than electrical measurement. The theory of probe measurements can give approximate results in a moving plasma.

We report a comparative study of a single plasma and a colliding laser produced plasma, investigated using a Faraday cup. An enhancement in ion emission and stagnation is observed in colliding plasma plume compared to single plasma plume. We observed that fast ion generation in laser ablated plasma can be achieved at large laser intensity on to the target. As laser intensity increases ionic yield increases for both colliding and single plume and at a fixed laser intensity ionic yield decreases with increase in ambient pressure. The double peak structure is observed in the ion signal at large fluence where the peaks correspond to fast and slow species. A Faraday cup composed of nine collectors is used to measure the spatial/angular distribution of ion of expanding plasma plume. Ionic yield is found to be larger in the colliding plasma plume than the single plasma plume at all spatial/angular positions.

For the characterisation of an electric propulsion system, the determination of the thrust has a crucial role. The thrust of an Indium FEEP Multiemitter (IFM) Nano Thruster laboratory model is measured directly with a thrust balance and indirectly via beam diagnostics. Both measurements are carried out simultaneously to enable mutual verification with high accuracy. The novel mN-torsion thrust balance by FOTEC resolves six different thrust magnitudes, ranging from 10 μ N to 1 N. It is based on the so-called force-feedback method using a voice coil actuator to determine the thrust, which leads to an accuracy of better than 2 %. The indirect thrust measurements were performed with a high-precision beam diagnostics system by FOTEC. A semi-circular diagnostics arm equipped with 23 digital Faraday cups is used to measure the ion current density distribution of the entire beam. The thrust results of both systems show an agreement with a deviation less than 5 % for thruster operation points ranging from 50 to 450 μ N. This proves that the performance of a FEEP thruster can be characterised very precisely by indirect trust measurements. • Presentation of FOTEC's newly developed high-precision mN-thrust balance for electric propulsion thrusters. • FEEP thruster beam characterisation using FOTEC's high-precision digital beam diagnostics system. • High degree of agreement between direct and indirect thrust measurements. [ABSTRACT FROM AUTHOR]

This review details the state of the art in in-space plasma diagnostics for characterizing the Earth’s ionosphere. The review provides a historical perspective, focusing on the last 20 years and on eight of the most commonly used plasma sensorsâ€"most of them for in situ probing, many of them with completed/in-progress space missions: (a) Langmuir probes, (b) retarding potential analysers, (c) ion drift meters, (d) Faraday cups, (e) integrated miniaturized electrostatic analysers, (f) multipole resonance probes, (g) Fourier transform infrared spectrometers, and (h) ultraviolet absorption spectrometers. For each sensor, the review covers (a) a succinct description of its principle of operation, (b) highlights of the reported hardware flown/planned to fly in a satellite or that could be put in a CubeSat given that is miniaturized, and (c) a brief description of the space missions that have utilized such sensor and their findings. Finally, the review suggests tentative directions for future research. [ABSTRACT FROM AUTHOR]

A new multi-pinhole Faraday cup (MPFC) device was designed, fabricated and tested to measure ion beam uniformity over a range of centimeters. There are 32 collectors within the device, and each of those is used as an individual Faraday cup to measure a fraction of the beam current. Experimental data show that the device is capable of measuring a charged particles distribution - either in the form of a raster scanned focused beam or a defocused beam.

A proton source for calibrating electrostatic analyzers of charged particles by low-energy protons is developed on the basis of a standard A1 analyzer of an MX-6407P type radio-frequency mass spectrometer. The initial design of the A1 analyzer includes a thermionic cathode, an electron-impact gas ionization ion source, a three-stage multigrid selection system, an ion collector, and an electrometric head with a radio-frequency generator. The mass analyzer is transformed into a proton source by bringing ions outside the analyzer. To do that, the analyzer design is modified by removing the collector and electrometric head. The radio-frequency generator is removed from the head and located directly on the analyzer case. To form the output proton beam, accelerate it, and monitor the running value of the beam current, the analyzer collector and electrometric head are replaced by an ion receiver with a ring electrode and a microelectronic electrometric amplifier. The amplifier measures the current of ions incident onto the electrode. A part of the ions passing through the central aperture of the electrode forms an output proton beam. The design of the source and the procedure for its manufacture from the original analyzer are described. A technique is developed for tuning the output of a proton beam through a ring electrode and measuring the initial energy (70‒87 eV) by the retarding-potential technique. Using the Faraday-cup method, absolute calibration of the beam current by the ring-electrode current is carried out and the calibration characteristics of the source at energies from 0.3 to 5 keV are obtained. It is found that, upon a change in the beam current from 5 to 120 fA, the calibration characteristics are linear. [ABSTRACT FROM AUTHOR]

A magnetically insulated transmission line (MITL) is an inevitable choice for ultra-high power density energy transmissions. Its working process is complex, with an obvious influence on the working process of electron beam diodes and other load devices. The power coupling process of an electron beam diode driven by an MITL is a difficult problem in pulse power applications. No research is available on the electron beam characteristics of its anode. In this paper, a fast time response full absorption Faraday cup was developed. An intense electron beam measurement waveform showing the multi-stage characteristics was obtained through measurements using the Faraday cup absorber as the anode of the electron beam diode. The stage characteristics of the beam were in good agreement with the vacuum transmission, magnetic insulation formation, and multi-stage process of the stable magnetic insulation. The beam intensity corresponded with the conduction current of the cathode. It was obviously smaller than the current of the anode. The results reflected the influence of the different processes of the magnetic insulation on the transmission line on the beam waveforms in the diode area and provided a reference for the power transmission of the power device and the load system design.

The characteristic emission features of a laser-produced plasma depend strongly on the laser fluence. We investigated the spatial and temporal dynamics of neutrals and ions in a femtosecond laser (800 nm, ~40 fs, Ti:Sapphire) induced copper plasma in vacuum using both optical emission spectroscopy (OES) and spectrally resolved two-dimensional (2D) imaging over a wide fluence range of 0.5-77.5 J/cm2. 2D fast gated monochromatic images showed a distinct plume splitting between the neutrals and ions, especially at moderate to higher fluence. OES studies at low to moderate laser fluence confirm intense neutral line emission over ion emission, whereas this trend changes at higher laser fluence with dominance of the latter. This evidences a clear change in the physical processes involved in the femtosecond laser-matter interaction at high input laser intensity. The obtained ion dynamics resulting from OES and spectrally resolved 2D imaging are compared with charged particle measurement employing Faraday cup and Langmuir probe; results showed good correlation. [ABSTRACT FROM AUTHOR]

The dynamics of ions in ultrafast laser ablation of metals is studied over fluences ranging from the ablation threshold up to ≈75 J/cm2 by means of three well-established diagnostic techniques. Langmuir probe, Faraday cup, and spectrally resolved intensified charge coupled device imaging simultaneously monitored the ions produced during ultrafast laser ablation of a pure copper target with 800 nm, ≈50 fs, Ti: Sapphire laser pulses. The fluence dependence of ion yield is analyzed, resulting in the observance of three different regimes. The specific ion yield shows a maximum at about 4-5 J/cm2, followed by a gradual reduction and a transition to a high-fluence regime above ≈50 J/cm2. The fluence dependence of the copper ions angular distribution is also analyzed, observing a gradual increase in forward-peaking of Cu ions for fluences up to ≈10 J/cm2. A broader ion component is observed at larger angles for fluences larger than ≈10 J/cm2. Finally, an experimental characterization of the ionic angular distribution for several metallic targets (Mg, Al, Cr, Fe, Cu, and W) is carried out at a relatively high fluence of ≈66 J/cm2. Interestingly, the ion emission from the volatile metals shows a narrow, forward-peaked distribution, and a high peak ion yield compared to the refractory metals. Moreover, the width of ionic angular distributions presents a striking correlation with the peak ion yield. [ABSTRACT FROM AUTHOR]

Featured Application: Over the last decade electric propulsion devices have evolved from laboratory units to qualified space hardware. Due to the diversity of concepts numerous electric thruster technologies are available on the new space market. Each technology has a specific working principle which implies a wide variety of plasma discharges and ion beams. Currently, it is still difficult to compare, without bias, these plasmas to each other with standard devices and procedures. This work aims at contributing to the effort towards standardization of a specific type of plasma diagnostic called a Faraday cup. This instrument is of great importance as it measures the ion current density in electric thruster plumes. This physical quantity provides information on key parameter for thruster development and production such as thrust, beam divergence, ionization degree and propellant use. In this contribution we describe and validate the optimization of a Faraday cup collimator in the case of Hall thrusters. A Faraday cup (FC) is an instrument dedicated to current measurement in beams, jets and plasmas. It consists of a set of polarized electrodes mounted in such a way plasma sheath effect can be neglected, yielding accurate and reliable results. A FC is composed of three main parts, namely a collector or cup, which collects the current, a collimator, which defines the collection area and can contribute to limit electrons from entering the cup and a housing which protects the instrument from perturbation caused by the surrounding medium. In this paper, we provide experimental results of the effect of the collimator upon the measured ion current within the beam of a low-power Hall thruster. Different collimator materials, aperture diameters and polarization voltages are studied to determine the optimum design. Minimum dimension as well as appropriate materials are given as a conclusion in the case of low-power Hall thruster beam investigation. [ABSTRACT FROM AUTHOR]

Important tasks of modern space research are the study and continuous observations of the processes of cosmic and meteorological «weather». One of the electronic devices for carrying out such researches is a plasma sensor based on Faraday cup. The purpose of the work was to develop a constructive variant of the Faraday cup with precision sensitive (selective) elements in the form of metal grid microstructures and a four-sector collector, which has no analogues in the world technology.For the formation of grid nickel microstructures, a process has been developed for creating a matrix of nanoporous anodic aluminum oxide by photolithography as a precision shape (template) for depositing nanostructured metal layers. Methods for conducting testing for mechanical (vibrational) and thermocyclic impact that satisfies the requirements for space instruments have been developed.The grid microstructures are formed in a unified technological cycle with the production of ring-holders along the perimeter of the grid, with a square 20 × 20 μm2 section of the web and square cells with a size of 1 × 1 mm2. The transparency of each of the grids was more than 90 % for the normal incidence of light. Dimensions of holders and grid microstructures: internal diameters (34, 47, 60) ± 0.1 mm, external diameters of rings (42, 55, 68) ± 0.1 mm, respectively. The weight of one grid was less than 50 mg.The test results demonstrated the operability of the developed grid microstructures with multiple thermocyclic actions from –50 to +150 °C and vibrational and static overloads specific for space flights. Instruments for plasma measurements in the near of the Earth and in the interplanetary space will comprise six sensors with different angular orientations. This will make it possible to detect ions of cosmic plasma in a solid angle of about 180°.

The final as-built version of the DTL4 Faraday cup for the ESS proton accelerator is presented; the beam-interceptive device acted as beam dump to support the commissioning and tuning of the ESS proton accelerator up to the DTL4 section. The DTL4 Faraday cup was designed, optimized and validated via MCNPX/ANSYS simulations in order to dump [21, 74] MeV protons, proton pulses up to 50 μ s long, repetition rates up to 14 Hz and an unprecedented proton beam current up to 62.5 mA. The maximum volumetric power density was computed to be 20 GW/cm3 and 25 MW/cm3 for 21 MeV and 74 MeV protons, respectively. During the DTL4 commissioning, the DTL4 Faraday cup absorbed and safely dissipated the proton beam power, measured in real-time the proton beam current as well as the pulse duration. Examples of measured proton pulses are included to demonstrate the transport and acceleration of the high-power proton beam all the way down to the ESS DTL4 section. The control system for the data acquisition, operation under vacuum, motion control and cooling water system was based on EPICS. The operational parameters are presented following the results of thermo-mechanical calculations. In the most demanding operational condition, the predicted temperature of the core was around 1010 °C. The cooling water temperature was continuously monitored and remained below 23 °C during the operational period. Neutronics simulations were performed in order to quantify the activation, residual dose rates, radiation shielding and necessary decay time to be waited after the end of the commissioning. After four weeks of decay, a residual dose rate of 1.1 mSv/h was measured at 30 cm from the device. The DTL4 Faraday cup and its shielding were uninstalled in order to proceed with the installation of the DTL5 section. The Faraday cup is planned to be permanently installed in the DTL4 intertank once the DTL5 section is in place. [ABSTRACT FROM AUTHOR]

A Faraday cup (FC) is an instrument dedicated to current measurement in beams, jets and plasmas. It consists of a set of polarized electrodes mounted in such a way plasma sheath effect can be neglected, yielding accurate and reliable results. A FC is composed of three main parts, namely a collector or cup, which collects the current, a collimator, which defines the collection area and can contribute to limit electrons from entering the cup and a housing which protects the instrument from perturbation caused by the surrounding medium. In this paper, we provide experimental results of the effect of the collimator upon the measured ion current within the beam of a low-power Hall thruster. Different collimator materials, aperture diameters and polarization voltages are studied to determine the optimum design. Minimum dimension as well as appropriate materials are given as a conclusion in the case of low-power Hall thruster beam investigation.

Abstract The design, construction, installation, and testing of a Faraday Cup intended to measure the current of a 3 MeV, 1 μ A electron beam is described. Built as a current monitor for a Møller scattering measurement at the MIT High Voltage Research Laboratory, the device combines a large angular acceptance with the capability to measure a continuous, low energy beam. Bench studies of its performance demonstrate current measurements accurate to the percent level at 1 μ A. The Faraday Cup was designed and constructed at MIT and has been in use at the HVRL since 2017, providing a significantly more detailed measurement of beam current than was previously available. [ABSTRACT FROM AUTHOR]

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Abstract Faraday cups are widely used to characterize ion beam current. A deep canonical Faraday cup for determining ion beam currents from a helicon ion source has been designed, built and tested with beam. In this paper, CST Studio code is used to design the Faraday cup. The precise operation of a Faraday cup relies on its capability to recapture the ejected electrons when energetic particles collide with interior cup. The interior geometry of the Faraday cup is designed to minimize the loss of particles. In addition, a biased ring is embedded in front of the cup collector at voltages up to −300 V with respect to the collector. The collector is made of copper while the suppressor ring and the Faraday cup body are made of stainless steel. The measurements are utilized at RF powers and extraction voltages up to 1300 W and 20 kV, respectively. The measured ion beam current is an indirect way to demonstrate mode transition from inductively coupling plasma (ICP) to helicon mode of operation in the constructed helicon ion source. We have detected a sharp increase in the measured ion beam as the mode transition is reached. In addition, Optical emission spectroscopy (OES) method was also employed for demonstrating the mode transition. Highlights • The construction of a conical Faraday cup was performed to measure the ion current with the 2-kW helicon device. • In different values of the RF power and extraction voltage, the beam current was investigated. • Inductive-helicon mode transition was studied. [ABSTRACT FROM AUTHOR]

• The effects of nitrogen ions irradiation on the surface of the titanium sample were investigated using a 1.5 kJ Mather-type plasma focus device. • The time of flight and hence the energy of nitrogen ions emitted from the plasma focus device were measured by a Faraday cup. • Considering the spectrum profile of nitrogen ions in the plasma focus device, penetration depth and its correlation with the energy of ions are discussed. • The sputtering yield of titanium ions was determined using the SRIM simulation code. The plasma focus device is a simple, inexpensive, and precious device that can be considered as a source of high-energy ions for researches relevant to interactions of ions with widely used materials such as titanium. Regarding exclusive properties such as a high degree of hardness and resistance to corrosion, titanium nitride alloy is considered to be one of the most essential materials with a wide range of industrial applications. In the present study, the characteristics of titanium nitride alloys were studied using a 1.5 kJ Mather-type plasma focus device. To do this, a Faraday cup detector is used to measure the current density of the ion beam in order to determine the energy spectrum of nitrogen ions using time of flight approach. The optimal operational condition of the device for nitrogen ions emission, in terms of gas pressure and voltage of discharge were also determined. Titanium samples were situated on the top of the anode of the device and were exposed to nitrogen ion radiation considering 5, 10, and 20 shots of the device. To simulate the penetration depth of nitrogen ions inside the titanium samples, the SRIM code is used. The obtained energy of ions from the time of flight technique was set as input of the SRIM code, and it was found that nitrogen ions, with an average energy of 50 keV can penetrate about 110 nm inside the titanium sample. It was understood that the finding results of the penetration depth are in good agreement with the SEM micrographs of the titanium samples. The sputtering yield of titanium atoms was determined using the SRIM simulation code, and it was found that the yield of the surface of the samples is less than 0.2 atoms per individual nitrogen atom. [ABSTRACT FROM AUTHOR]

The 100 W-class ISCT100-v2 Hall Thruster (HT) has been characterized in terms of far-field plume properties. By means of a Faraday Cup and a Retarding Potential Analyzer, both the ion current density and the ion energy distribution function have been measured over a 180 ∘ circular arc for different operating points. Measurements are compared to far-field plume characterizations performed with higher power Hall thrusters. The ion current density profiles remain unchanged whatever the HT input power, although an asymptotic limit is observed in the core of the plume at high discharge voltages and anode mass flow rates. In like manner, the ion energy distribution functions reveal that most of the beam energy is concentrated in the core of the plume [ − 40 ∘ ; 40 ∘ ] . Moreover, the fraction of low energy ion populations increases at large angles, owing to charge exchange and elastic collisions. Distinct plume regions are identified; they remain similar to the one described for high-power HTs. An efficiency analysis is also performed in terms of current utilization, mass utilization, and voltage utilization. The anode efficiency appears to be essentially affected by a low voltage utilization, the latter originating from the large surface-to-volume ratio inherent to low-power HTs. Experimental results also show that the background pressure clearly affects the plume structure and content.

A series of experimental measurements of fast ions generated in a tungsten conical wire array are presented. The ions are detected using a set of negatively biased Faraday cups located on axis above the array at distances between 10 and 67 cm. Significant differences in the signals from the probes are found on varying the background atmospheric pressure between 10−2 and 10−5 Torr. At 10−5 Torr, a pulse of ions moving at 106 m/s is collected by the cups. In contrast, at intermediate (10−4 Torr) and high (10−2 Torr) pressures, both electrons and ions are detected with a velocity of order 106 m/s. The differences with pressure are ascribed to the ionization of the background gas by the tungsten ions. Time-of-flight measurements show the emission of fast ions during the ablation phase of wire array dynamics. Comparing the temporal behavior of the ions and their velocity of propagation with the dynamics observed using UltraViolet / eXtreme UltraViolet imaging allows us to conclude that the ions and the dense plasma jet are different phenomena. Moreover, the application of a transverse electric field establishes the presence of massive ions in the outflow, suggesting also the presence of MeV tungsten ions with ionization of five or less. The observation of a fast particle outflow from a conical wire array and a possible ejection mechanism is discussed. [ABSTRACT FROM AUTHOR]

Measurement of runaway electron beam (REB) is essential to investigate behavior of runaway electrons produced in nanosecond-pulse gas discharge. A Faraday cup is designed to measure the REB current in nanosecond-pulse discharge when the applied d V /d t is 75 kV/ns. The Faraday cup considers the impendence match with the oscilloscope and the design of the receiving part. The experimental results show that the measured REB current has a rise time of 348 ps and a full width at half maximum of 510 ps. The comparison of the measurement results by the Faraday cup and a REB collector confirm that the Faraday cup is able to measure REB current in nanosecond-pulse discharge. Furthermore, consecutive waveforms of the REB currents show stable results by using the designed Faraday cup. In addition, effects of the interelectrode gap, gas pressure, and cathode material on the REB current are investigated by the designed Faraday cup, and the measurement results provide characteristics of REB current under different conditions. The REB current decreases when the gap spacing or gas pressure increases. REB current increases with the cathode diameter. It indicates that the high-energy electrons are generated not only at the edge of the cathode but also on the side surface of the cathode. [ABSTRACT FROM AUTHOR]

A Faraday cup aerosol electrometer based electrical aerosol instrument calibration setup from nanometers up to micrometers has been designed, constructed, and characterized. The set-up utilizes singly charged seed particles, which are grown to the desired size by condensation of diethylhexyl sebacate. The calibration particle size is further selected with a Differential Mobility Analyzer (DMA). For micrometer sizes, a large DMA was designed, constructed, and characterized. The DMA electrical mobility resolution was found to be 7.95 for 20 L/min sheath and 2 L/min sample flows. The calibration is based on comparing the instrument’s response against the concentration measured with a reference Faraday cup aerosol electrometer. The set-up produces relatively high concentrations in the micrometer size range (more than 2500 1/cm3 at 5.3 µm). A low bias flow mixing and splitting between the reference and the instrument was constructed from a modified, large-sized mixer and a four-port flow splitter. It was characterized at different flow rates and as a function of the particle size. Using two of the four outlet ports at equal 1.5 L/min flow rates, the particle concentration bias of the flow splitting was found to be less than ±1% in the size range of 3.6 nm-5.3 µm. The developed calibration set-up was used to define the detection efficiency of a condensation particle counter from 3.6 nm to 5.3 µm with an expanded measurement uncertainty (k = 2) of less than 4% over the entire size range and less than 2% for most of the measurement points. Copyright © 2018 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

Transient clouds of a plasma generated by hypervelocity dust particles impacting onto the spacecraft were observed in-situ by many experiments over the last 20 years. The reported observations analyze sensitive measurements of plasma waves that are transmitted to the Earth with a sufficient time resolution. The detection is based on a fact that hypervelocity impacts generate plumes of the ionized gas expanding into a space. The present paper analyzes five years of the operation of the Bright Monitor of the Solar Wind (BMSW) onboard the Spektr-R spacecraft with a motivation to demonstrate that such type of the instruments is capable to observe the dust impacts into its detectors. The results of analysis are compared with Wind electric field measurements used for a detection of hypervelocity dust impacts. [ABSTRACT FROM AUTHOR]

Nowadays, laser wakefield acceleration is considered to be one of the perspective methods for GeV electron beam production. The combination of laser accelerated electrons and Compton backscattering of a probe light beam opens the possibility of creating the tabletop source of a femtosecond light beam in x-ray and gamma ranges. The project is aimed at creating a laser-driven Compton light source in ILP SB RAS in collaboration with BINP SB RAS. Production of 1–10 pC electron beams in sub-ps time range duration with energies up to 100 MeV is expected to be a result of the first stage of the project. Since the energy of electrons does not exceed 100 MeV, it allows the use of the Faraday cup (FC) with reasonable dimensions, instead of the commonly used integrating current transformer. The geometry of the FC has been optimized taking into account beam stopping simulation as well as a low capacity requirement. Simulation of high-frequency properties of the entire system was carried out. The system has been tested at the VEPP-5 electron linac. The results of developing and testing this FC are presented. [ABSTRACT FROM AUTHOR]

We report a new method for calibrating the current gain of 1013 Ω amplifiers in both positive and negative mode used in thermal ionisation mass spectrometry (TIMS). This method uses any isotopic standard or sample to calibrate the gain factor as long as it can produce a stable current signal. It is simpler and more flexible than that recommended by Thermo-Fisher (the manufacture of the TIMS). In these analyses, the gains of five 1013 Ω amplifiers were assessed. The precision of gain factors was better than 100 ppm (2 RSD) in a day, and the long-term reproducibility was better than 300 ppm (2 RSD) within 2 to 8 months. After a gain was calibrated, the ratio accuracy and precision in the positive mode for 87Sr/88Sr of NIST 987 Sr and 143Nd/144Nd of La Jolla Nd were 0.710242 ± 60 (2 SD, n = 14) and 0.511842 ± 10 (2 SD, n = 22), respectively, at intensities of 88Sr 0.3 V and 142Nd 0.4 V, while in the negative mode for 187Os/188Os of Merck Os was 0.120229 ± 34 (2 SD, n = 23) at an intensity of 187OsO3 0.01 mV. In addition, a difference in the gain factors between the negative modeTIMS (NTIMS) and positive modeTIMS (PTIMS) has been recognized. The values of the gain factor for NTIMS and PTIMS show a deviation of 0.54% on the Triton and 0.31% on the Triton Plus TIMS in this study; therefore, gain calibration should be carried out on both NTIMS and PTIMS. Moreover, a bias of ~ 1.5 × 10-5 between H and L Faraday cups for the same 1013 Ω amplifier has been detected, hinting that the efficiency of different Faraday cups may affect the gain factors, which can be eliminated through the new method of "cross-calibration" discribed in this study. [ABSTRACT FROM AUTHOR]

The development, performance, and testing of the longitudinal bunch shape monitor, namely, the Fast Faraday Cup (FFC), are presented in this paper. The FFC is an invasive instrument controlled by a stepper motor, and its principle of operation is based on a strip line structure. The longitudinal bunch shape was determined by sampling a small part of the beam hitting the strip line through a 1-mm hole. The rise time of the detector reached 24 ps. To accommodate experiments that utilize high-intensity beams, the materials of the bunch shape monitor were chosen to sustain high temperatures. Water cooling was also integrated in the detector system to enhance heat transfer and prevent thermal damage. We also present an analysis of the heating caused by the beam. The bunch shape monitor has been installed and commissioned at the China ADS proton LINAC Injector II. [ABSTRACT FROM AUTHOR]