Search

The conversion of methane into transportable and storable materials is crucial in the petrochemical sector. In this study, a specially constructed AC‐driven dielectric barrier discharge (DBD) that has charge injector pyramids on one of the electrodes and runs at ambient temperature and pressure was used to evaluate noncatalytic methane conversion. The obtained result was compared with the traditional flat electrode DBD. It was discovered that the product selectivity in direct nonoxidative methane conversion depended on the discharge conditions. Pyramid electrode plasma sources convert methane up to 50% $ \% $ more than flat electrode plasma due to the appearance of more microdischarges. Pyramid electrode plasma generally has a greater production efficiency than flat electrode plasma, while requiring more operational power. The turnkey solutions offered by the sustainable methane coupling method discussed here may be advantageous for the long‐term small‐scale ethylene exploration scenario. [ABSTRACT FROM AUTHOR]

Recently, a bouncing-like mechanism for electron multiplication inside long nano-ruptures during the early stages of nanosecond discharge in liquid water has been proposed in (Bonaventura 2021 Plasma Sources Sci. Technol. 30 065023). This mechanism leads to the formation of electron avalanches within nano-ruptures caused by strong electrostrictive forces. The avalanche propagation is a self-sustaining process: the electrons emitted from the water surface to the cavity support the propagation of the avalanche and the avalanche itself is a source of the parent electrons impinging on the surface of the nano-rupture and causing secondary emission. We analyze the process of the electron secondary emission directly from the simulation results of the electron avalanche propagation. This allow us to perform an in situ study of the secondary emission and related physical processes. We present the results of an extensive parametric study performed using the state-of-the-art simulation toolkit Geant4-DNA for modeling electron-liquid water interactions. It is shown that the typical lifetime of an electron in an avalanche is about 0.1 to 0.2 picoseconds and that the electron experiences about 4 bounces before ending up in liquid water. In addition, it is shown that the secondary electrons are formed in a layer adjacent to the nano-rupture surface that is only a few nanometres thin. The secondary electron velocity distribution at the moment of the electron birth, the velocity space of electrons (re-)emitted from the water, and the velocity space of electrons at the moment of their impact to the cavity surface are analyzed in detail. Electron bouncing and secondary electron generation efficiency are quantified using the secondary emission coefficient, the secondary emission efficiency, and the effective energy consumed to produce new electrons. [ABSTRACT FROM AUTHOR]

The purpose of this work is to study the dielectric charging of polymer fibers with the electron plasma charging effects accompanied by the emergence of waves propagating along the polymer fiber surface. Monitoring of the charge propagation along the single fiber has been performed using dielectric polyhydroxybutyrate (PHB) fibers obtained by the electrospinning (ESP) method under the electron beam inside the scanning electron microscope chamber. The mechanical effect of the electron beam on the polymer fibers has been detected in a time-lapse mode. The influence of the polymer surface irregularities and mechanical defects on the fiber charging has been demonstrated. Plasma mechanism is typical not only for electrophysical phenomena but also for the control of mechanical movement of the fibers by the electron beam and the charge propagation during electron-beam-induced melting and in the presence of hydrodynamic polymer flows. It is assumed that the mechanical effect in the methods using an electron beam (and plasma on the dielectric surface) as an impact source can be determined by the following factors: pressure of the electron beam and the electric field, contribution of the secondary emission, thermal/thermomechanical factors, and dynamic balance or competition between all the forces affecting the sample (electron-beam pressure, gravity pressure, recoil pressure during evaporation, vapor pressure/surface tension, and so on). In addition to purely scientific interest, the above phenomena are also of significant applied interest since the influence of the polymer fiber charging on the separation procedure of aerosols in nonwoven filters is well known, and hence, charging of such polymer fibers is important for some energy storage devices. [ABSTRACT FROM AUTHOR]

The cathode in the magnetron should have good secondary emission property and a certain thermionic property. In this article, ZrH2 was added as an activator to obtain rare earth-doped tungsten matrix impregnated cathode to improve the emission property. Cathodes with ZrH2 (Y15-411-Zr cathode) or without ZrH2 (Y15-411 cathode) were prepared by a spray drying method combined with high-temperature sintering in dry hydrogen atmosphere. The emission properties and emission mechanism have been studied. The results showed that thermionic emission performance and secondary emission performance of Y15-411-Zr cathode are 3.4 times and 1.2 times higher than those of Y15-411 cathode, respectively. With the addition of ZrH2, yttrium was produced during activating process, which contributed to the better emission properties of Y15-411-Zr cathode. Furthermore, the work function of barium and oxygen adsorbed on yttrium oxide and yttrium surface was calculated using the first principle. The results showed that the lowest work function of Ba-O absorbed on Y2O3 and Y is 1.9 and 1.6 eV, respectively. [ABSTRACT FROM AUTHOR]

The test results of the prototype of the secondary-emission probe operating in the mode of self-oscillatory sweep intended for diagnosing nonequilibrium plasma in the presence of epithermal group of electrons are given. Earlier, the method of self-oscillatory probe was tested using an aluminum water-cooled contact surface with formation of a nanoscale thick high-emission oxide coating. The structure of the described probe is peculiar owing to application of refractory tantalum, which is capable of working in the mode of radiation cooling, which simplifies the structure and increases the reliability of the probe. It is shown that, owing to secondary-emission characteristics, oxide-coated tantalum allows under plasma loading obtaining a pronounced N-type current–voltage characteristic with a large excess in the electron-emission current component against the ion saturation current and satisfies all requirements for realization of the method of self-oscillatory probe. [ABSTRACT FROM AUTHOR]

A method of ion saturation current measurement in a nonequilibrium plasma by a self-oscillating voltage sweep on the probe is described. The generation of voltage pulses is possible if a high secondary electron emission from the probe surface is ensured, significantly exceeding unity at a moderate negative potential. The theoretical basis of the self-oscillating probe method has been considered, which made it possible to describe the ways for controlling the repetition rate and pulse amplitude and the effect of plasma parameters on the shape of current and voltage signals. It is shown that the features of the phase trajectory of the signal from the probe on the (U, I) plane allow one to determine the reference points of instantaneous probe characteristic, in particular, the ion saturation current. The results of experiments on testing the self-oscillating probe technique, which were carried out using the PR-2 plasma-beam facility, are presented. [ABSTRACT FROM AUTHOR]

This paper presents a study of the multipactor effect in a partially dielectric-loaded rectangular waveguide. To obtain the simulations presented in this paper, a detailed analysis of the dynamics of the electron inside this waveguide has been performed, taking into account the radio frequency electromagnetic fields propagating in the waveguide and the dc electric field that appears because of the charging of the dielectric layer. This electrostatic field is obtained by computing the electric potential produced by an arbitrary charge distribution on the dielectric layer in a dielectric-loaded waveguide. The electron trajectory is then found by numerically solving the equations of motion. The results obtained show that multipactor discharges do turn off by themselves under certain circumstances when they occur in such dielectric-loaded waveguide. [ABSTRACT FROM AUTHOR]

• Supraharmonic emission differs among single-phase and three-phase installations due to conductor crosstalk. • Four parameters are shown to impact, i.e., the cable used in an installation, length of the conductor and conductor impedance, load impedance of the devices connected in all phases and transformer impedance. • A sensitivity analysis among the influencing parameters is carried out where the type of cable and the length of cable show the highest sensitivity • Induced primary and secondary emission becomes more significant for longer cables for frequencies greater than 100 kHz The induced primary emission leads to changes in the primary emission of a device and the induced secondary emission leads to changes in the propagation of supraharmonics in the adjacent phase due to the connection of single-phase loads spread over three phases in an installation. The induced primary emission and induced secondary emission are shown to give a significant contribution to the total emission measured at a given point in an installation. The induction of the emission is caused by the inductive and capacitive coupling among the conductors within the cables. This paper presents an analysis of four parameters that impact the magnitude of the induced emissions. Simulations carried out in COMSOL, show that the type of cable used impacts the induced emission and studies show that shielded cable with a stranded conductor with the shield grounded will lead to a reduction in the induced emissions. Among the other parameters, i.e., the load and transformer impedance and the length of the cable, the length of the cable is dominating in deciding the magnitude of the induced emissions. Analysis is carried out using Monte Carlo simulation and varying parameters stochastically. For all investigated parameters there is a strong frequency dependency. The stochastic variation of the load impedance in one phase causes a variation of 5% whereas the change in length of the cable leads to a maximum 40% variation in the considered frequency range for induced primary emission. Measurement results are presented to validate the results. [ABSTRACT FROM AUTHOR]

Resistive Plate Chambers (RPCs) are essential active media of large-scale experiments as part of the muon systems and (semi-)digital hadron calorimeters. Among the several outstanding issues associated with the RPCs, the loss of efficiency for the detection of particles when subjected to high particle fluxes, and the limitations associated with the common RPC gases can be listed. In order to address the latter issue, we developed novel RPC designs with special anode plates coated with high secondary electron emission yield materials such as Al 2 O 3 and TiO 2. The proof of principle was obtained for various designs and is in progress for the rest. The idea was initiated following the achievements on the development of the novel 1-glass RPCs. Here we report on the construction of various different RPC designs, and their performance measurements in laboratory tests and with particle beams; and discuss the future test plans. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A simple spectrometer design for pulsed laser ablation plumes. • Distinguish particles with the same mass-to-charge ratio. • Simple design, with no high voltage pulsing. • Reconfigurable to adjust uncertainty and operating energy range. • Prototype demonstration. Abstract A mass spectrometer has been designed to distinguish ions of different mass but identical mass to charge ratio. Separation of mass from charge is based upon secondary particle emission when each ion impacts the detector. The yield of secondary particles is a function of kinetic energy rather than energy-per-charge. Combined with an electrostatic energy gate and time-of-flight, the mass can be determined from kinetic energy, energy-per-charge, and mass-per-charge. The design is of moderate precision but simpler than available alternatives – particles need not be extracted from the vacuum chamber for sizing nor the detector kept at cryogenic temperatures. The prototype is demonstrated on an aluminum ablation plume and an ionic liquid ion source. [ABSTRACT FROM AUTHOR]

A compact introduction to the history and the canonical equations of electron emission is given for thermal emission (Richardson), field emission (Fowler–Nordheim), photoemission (Fowler–DuBridge), and secondary emission (Baroody), as well as the space-charge-limited flow (Child–Langmuir law). A general equation is derived and related to the canonical equations. Processes that affect emission, such as coatings, shielding, excitation and transport, space charge, emittance, and material properties, are considered. Requirements imposed by beam evolution are discussed. [ABSTRACT FROM AUTHOR]

Hundreds of concurrent collisions per bunch crossing are expected at future hadron colliders. Precision timing calorimetry has been advocated as a way to mitigate the pileup effects and, thanks to their excellent time resolution, microchannel plates (MCPs) are good candidate detectors for this goal. We report on the response of MCPs, used as secondary emission detectors, to single relativistic particles and to electromagnetic showers. Several prototypes, with different geometries and characteristics, were exposed to particle beams at the INFN-LNF Beam Test Facility and at CERN. Their time resolution and efficiency are measured for single particles and as a function of the multiplicity of particles. Efficiencies between 50% and 90% to single relativistic particles are reached, and up to 100% in presence of a large number of particles. Time resolutions between 20 ps and 30 ps are obtained. [ABSTRACT FROM AUTHOR]

Influence of electric field of charged spacecraft on secondary emission currents on the spacecraft surface is analyzed in terms of computation of secondary electron trajectories. Dependencies of the recollected electrons number on the electric field intensity at various distances from the emission point for standard secondary electron spectra are calculated. Criteria of the secondary electron emission suppression by the surface electric field which is applied for spacecraft charging modeling using the COULOMB-2 code are proposed. Modeling of the emitted electron trajectories in the electric field of the charged spacecraft having complex surface configuration enables to compute correction factors added to electric current balance equations (electron recollection). [ABSTRACT FROM PUBLISHER]

A size-resolved, one-dimensional resuspension scheme for soil particles from the ground surface is proposed to evaluate the concentration of radioactivity in the atmosphere due to the secondary emission of radioactive material. The particle size distributions of radioactive particles at a sampling point were measured and compared with the results evaluated by the scheme using four different soil textures: sand, loamy sand, sandy loam, and silty loam. For sandy loam and silty loam, the results were in good agreement with the size-resolved atmospheric radioactivity concentrations observed at a school ground in Tsushima District, Namie Town, Fukushima, which was heavily contaminated after the Fukushima Dai-ichi Nuclear Power Plant accident in March 2011. Though various assumptions were incorporated into both the scheme and evaluation conditions, this study shows that the proposed scheme can be applied to evaluate secondary emissions caused by aeolian resuspension of radioactive materials associated with mineral dust particles from the ground surface. The results underscore the importance of taking soil texture into account when evaluating the concentrations of resuspended, size-resolved atmospheric radioactivity. [ABSTRACT FROM AUTHOR]

Abstract The late pulse occurring in photomultiplier tubes (PMTs) is attributed to photoelectron backscattering. The small effective open area of microchannel plates (MCPs) increases the probability of photoelectrons bouncing on the front surface of MCPs and aggravates late pulses. In this work, a three-dimensional MCP-PMT model is developed in CST particle studio, a powerful electromagnetic field simulation program, to evaluate the effects of secondary emission yield (SEY) property of the MCP input facet and electric field on the photoelectron backscattering. Timing properties and the number of collected electrons are extracted without smearing due to electronic noise and finite pulse width. Results predict that the collection efficiency (CE) and the time performance can be improved by coating the MCP Nickel–Chromium input electrode with a high SEY material and operating in a proper photocathode-MCP bias voltage. Highlights • The physical processes leading to an output pulse of the MCP-PMT are analyzed. • The effects of the secondary emission yield (SEY) property of the MCP input facet and the electric field on the photoelectron backscattering are investigated. • Both the timing and the collection efficiency of the later pulses are studied. • Solutions to improve the collection efficiency and the timing performance of the MCP-PMT are discussed. [ABSTRACT FROM AUTHOR]

Purpose: Magnetic resonance imaging-guided radiotherapy (MRIgRT) provides superior soft-tissue contrast and real-time imaging compared with standard image-guided RT, which uses x-ray based imaging. Several groups are developing integrated MRIgRT machines. Reference dosimetry with these new machines requires accounting for the effects of the magnetic field on the response of the ionization chambers used for dose calibration. Here, the authors propose a formalism for reference dosimetry with integrated MRIgRT devices. The authors also examined the suitability of the TPR1020 and %dd(10)x beam quality specifiers in the presence of magnetic fields and calculated detector correction factors to account for the effects of the magnetic field for a range of detectors. Methods: The authors used full-head and point-source Monte Carlo models of an MR-linac along with detailed detector models of an Exradin A19, an NE2571, and several PTW Farmer chambers to calculate magnetic field correction factors for six commercial ionization chambers in three chamber configurations. Calculations of ionization chamber response (performed with GEANT4) were validated with specialized Fano cavity tests. %dd(10)x values, TPR1020 values, and Spencer-Attix water-to-air restricted stopping power ratios were also calculated. The results were further validated against measurements made with a preclinical functioning MR-linac. Results: The TPR1020 was found to be insensitive to the presence of the magnetic field, whereas the relative change in %dd(10)x was 2.4% when a transverse 1.5 T field was applied. The parameters chosen for the ionization chamber calculations passed the Fano cavity test to within ~0.1%. Magnetic field correction factors varied in magnitude with detector orientation with the smallest corrections found when the chamber was parallel to the magnetic field. Conclusions: Reference dosimetry can be performed with integrated MRIgRT devices by using magnetic field correction factors, but care must be taken with the choice of beam quality specifier and chamber orientation. The uncertainties achievable under this formalism should be similar to those of conventional formalisms, although this must be further quantified. [ABSTRACT FROM AUTHOR]

Purpose: Plastic scintillation detectors are promising candidates for the dosimetry of low- to medium-energy photons but quantitative knowledge of their energy response is a prerequisite for their correct use. The purpose of this study was to characterize the energy dependent response of small scintillation detectors (active volume <1 mm³) made from the commonly used plastic scintillator BC400. Methods: Different detectors made from BC400 were calibrated at a number of radiation qualities ranging from 10 to 280 kV and at a 60Co beam. All calibrations were performed at the Physikalisch- Technische Bundesanstalt, the National Metrology Institute of Germany. The energy response in terms of air kerma, dose to water, and dose to the scintillator was determined. Conversion factors from air kerma to dose to water and to dose to the scintillator were derived from Monte Carlo simulations. In order to quantitatively describe the energy dependence, a semiempirical model known as unimolecular quenching or Birks' formula was fitted to the data and from this the response to secondary electrons generated within the scintillator material BC400 was derived. Results: The detector energy response in terms of air kerma differs for different scintillator sizes and different detector casings. It is therefore necessary to take attenuation within the scintillator and in the casing into account when deriving the response in terms of dose to water from a calibration in terms of air kerma. The measured energy response in terms of dose to water for BC400 cannot be reproduced by the ratio of mean mass energy-absorption coefficients for polyvinyl toluene to water but shows evidence of quenching. The quenching parameter kB in Birks' formula was determined to be kB = (12.3±0.9) mg MeV-1 cm-2. Conclusions: The energy response was quantified relative to the response to 60Co which is the common radiation quality for the calibration of therapy dosemeters. The observed energy dependence could be well explained with the assumption of ionization quenching as described by Birks' formula. Plastic scintillation detectors should be calibrated at the same radiation quality that they will be used at and changes of the spectrum within the application need to be considered. The authors results can be used to evaluate the range of validity of a given calibration. [ABSTRACT FROM AUTHOR]

Purpose: A protocol for reference dosimetry for the MR-linac is under development. The 1.5 T magnetic field changes the mean path length of electrons in an air-filled ionization chamber but has little effect on the electron trajectories in a surrounding phantom. It is therefore necessary to correct the response of an ionization chamber for the influence of the magnetic field. Solid phantoms are used for dosimetry measurements on the MR-linac, but air is present between the chamber wall and phantom insert. This study aimed to determine if this air influences the ion chamber measurements on the MR-linac. The absolute response of the chamber and reproducibility of dosimetry measurements were assessed on an MR-linac in solid and water phantoms. The sensitivity of the chamber response to the distribution of air around the chamber was also investigated. Methods: Measurements were performed on an MR-linac and replicated on a conventional linac for five chambers. The response of three waterproof chambers was measured with air and with water between the chamber and the insert to measure the influence of the air volume on absolute chamber response. The distribution of air around the chamber was varied indirectly by rotating each chamber about the longitudinal chamber axis in a solid phantom and a water phantom (waterproof chambers only) and measuring the angular dependence of the chamber response, and varied directly by displacing the chamber in the phantom insert using a paper shim positioned at different orientations between the chamber casing and the insert. Results: The responses of the three waterproof chambers measured on the MR-linac were 0.7%-1.2% higher with water than air in the chamber insert. The responses of the chambers on the conventional linac changed by less than 0.3% when air in the insert was replaced with water. The angular dependence of the chambers ranged from 0.6% to 1.9% in the solid phantom on the MR-linac but was less than 0.5% in water on the MR-linac and less than 0.3% in the solid phantom on the conventional linac. Inserting a shim around the chamber induced changes of the chamber response in a magnetic field of up to 2.2%, but the change in chamber response on the conventional linac was less than 0.3%. Conclusions: The interaction between the magnetic field and secondary electrons in the air around the chamber reduces the charge collected from 0.7% to 1.2%. The large angular dependence of ion chambers measured in the plastic phantom in a magnetic field appears to arise from a change of air distribution as the chamber is moved within the insert, rather than an intrinsic isotropy of the chamber sensitivity to radiation. It is recommended that reference dosimetry measurements on the MR-linac can be performed only in water, rather than in existing plastic phantoms. [ABSTRACT FROM AUTHOR]

Purpose: High dose rate (HDR) brachytherapy for treatment of small skin lesions using the Leipzig and Valencia applicators is a widely used technique. These applicators are equipped with an attachable plastic cap to be placed during fraction delivery to ensure electronic equilibrium and to prevent secondary electrons from reaching the skin surface. The purpose of this study is to report on the dosimetric impact of the cap being absent during HDR fraction delivery, which has not been explored previously in the literature. Methods: GEANT4 Monte Carlo simulations (version 10.0) have been performed for the Leipzig and Valencia applicators with and without the plastic cap. In order to validate the Monte Carlo simulations, experimental measurements using radiochromic films have been done. Results: Dose absorbed within 1 mm of the skin surface increases by a factor of 1500% for the Leipzig applicators and of 180% for the Valencia applicators. Deeper than 1 mm, the overdosage flattens up to a 10% increase. Conclusions: Differences of treating with or without the plastic cap are significant. Users must check always that the plastic cap is in place before any treatment in order to avoid overdosage of the skin. Prior to skin HDR fraction delivery, the timeout checklist should include verification of the cap placement. [ABSTRACT FROM AUTHOR]

Polychlorinated biphenyls (PCBs) are banned worldwide under the Stockholm Convention on Persistent Organic Pollutants. However, PCBs are still emitted in appreciable amounts from remaining primary sources in urban areas or landfills and are ubiquitous environmental contaminants, inter alia in soil and air. Concentrations of PCBs have been measured in various media by numerous studies worldwide. However, monitoring data do not always provide quantitative information about transport processes between different media, deposition fluxes to ground, or distribution of PCBs between environmental compartments. Also future trends in environmental contamination by PCBs cannot be predicted from monitoring data, but such information is highly relevant for decision-makers. Here, we present a new regionally resolved dynamic multimedia mass balance model for Switzerland to investigate the origin of PCBs in air and to investigate their long-term fate and mass balance in the environment. The model was validated with existing field data for PCBs. We find that advective inflow of PCBs from outside Switzerland into the atmospheric boundary layer is responsible for 80% of PCBs present in air in Switzerland, whereas Swiss emissions cause the remaining 20%. Furthermore, we show that the atmospheric deposition of the higher-chlorinated PCBs is dominated by particle-bound deposition, whereas the deposition of the lower-chlorinated PCBs is a combination of particle-bound and gaseous deposition. The volume fraction of particles in air is in both cases an important factor driving the deposition of PCBs to ground and, thus, contributing to the higher concentrations of PCBs generally observed in populated and polluted areas. Regional emissions influence the deposition fluxes only to a limited extent. We also find that secondary emissions from environmental reservoirs do not exceed primary emissions for all PCB congeners until at least 2036. Finally, we use our model to evaluate the effect of chemical regulation on future environmental contamination by PCBs. [ABSTRACT FROM AUTHOR]

Purpose: To report on significant dose enhancement effects caused by magnetic fields aligned parallel to 6 MV photon beam radiotherapy of small lung tumors. Findings are applicable to future inline MRI-guided radiotherapy systems. Methods: A total of eight clinical lung tumor cases were recalculated using Monte Carlo methods, and external magnetic fields of 0.5, 1.0, and 3 T were included to observe the impact on dose to the planning target volume (PTV) and gross tumor volume (GTV). Three plans were 6 MV 3D-CRT plans while 6 were 6 MV IMRT. The GTV's ranged from 0.8 to 16 cm³, while the PTV's ranged from 1 to 59 cm3. In addition, the dose changes in a 30 cm diameter cylindrical water phantom were investigated for small beams. The central 20 cm of this phantom contained either water or lung density insert. Results: For single beams, an inline magnetic field of 1 T has a small impact in lung dose distributions by reducing the lateral scatter of secondary electrons, resulting in a small dose increase along the beam. Superposition of multiple small beams leads to significant dose enhancements. Clinically, this process occurs in the lung tissue typically surrounding the GTV, resulting in increases to the D98% (PTV). Two isolated tumors with very small PTVs (3 and 6 cm³) showed increases in D98% of 23% and 22%. Larger PTVs of 13, 26, and 59 cm³ had increases of 9%, 6%, and 4%, describing a natural fall-off in enhancement with increasing PTV size. However, three PTVs bounded to the lung wall showed no significant increase, due to lack of dose enhancement in the denser PTV volume. In general, at 0.5 T, the GTV mean dose enhancement is around 60% lower than that at 1 T, while at 3 T, it is 5%-60% higher than 1 T. Conclusions: Monte Carlo methods have described significant and predictable dose enhancement effects in small lung tumor plans for 6 MV radiotherapy when an external inline magnetic field is included. Results of this study indicate that future clinical inline MRI-guided radiotherapy systems will be able to deliver a dosimetrically superior treatment to small (PTV < 15 cm³), isolated lung tumors over non-MRI-Linac systems. This increased efficacy coincides with the reimbursement in the United States of lung CT screening and the likely rapid growth in the number of patients with small lung tumors to be treated with radiotherapy. [ABSTRACT FROM AUTHOR]

Purpose: The authors introduce a radiation detection method that relies on high-energy current (HEC) formed by secondary charged particles in the detector material, which induces conduction current in an external readout circuit. Direct energy conversion of the incident radiation powers the signal formation without the need for external bias voltage or amplification. The detector the authors consider is a thin-film multilayer device, composed of alternating disparate electrically conductive and insulating layers. The optimal design of HEC detectors consists of microscopic or nanoscopic structures. Purpose: The authors introduce a radiation detection method that relies on high-energy current (HEC) formed by secondary charged particles in the detector material, which induces conduction current in an external readout circuit. Direct energy conversion of the incident radiation powers the signal formation without the need for external bias voltage or amplification. The detector the authors consider is a thin-film multilayer device, composed of alternating disparate electrically conductive and insulating layers. The optimal design of HEC detectors consists of microscopic or nanoscopic structures. Results: The authors found that in a dual-layer configuration, the signal is in the measurable range. For a defined total detector thickness in a multilayer structure, the signal sharply increases with decreasing thickness of the high-Z conductive layers. This paper focuses on the computational results while a companion paper reports the experimental findings. Conclusions: Significant advantages of the device are that it does not require external power supply and amplification to create a measurable signal; it can be made in any size and geometry, including very thin (sub-millimeter to submicron) flexible curvilinear forms, and it is inexpensive. Potential applications include medical dosimetry (both in vivo and external), radiation protection, and other settings where one or more of the above qualities are desired. [ABSTRACT FROM AUTHOR]

The results of investigating nanostructured mediums are presented; the mediums are formed in carbon-based and semiconductor materials by the methods enabling integration into microelectronic technologies. The investigations are carried out with a wide variety of instruments and diagnostic techniques. The investigation's results are shown to be useful in optimizing parameters of technological processes for the formation of nanostructured mediums. [ABSTRACT FROM AUTHOR]

We report on the response of microchannel plates (MCPs) to single relativistic particles and to electromagnetic showers. Particle detection by means of secondary emission of electrons at the MCP surface has long been proposed and is used extensively in ion time-of-flight mass spectrometers. What has not been investigated in depth is their use to detect the ionizing component of showers. The time resolution of MCPs exceeds anything that has been previously used in calorimeters and, if exploited effectively, could aid in the event reconstruction at high luminosity colliders. Several prototypes of photodetectors with the amplification stage based on MCPs were exposed to cosmic rays and to 491 MeV electrons at the INFN-LNF Beam-Test Facility. The time resolution and the efficiency of the MCPs are measured as a function of the particle multiplicity, and the results used to model the response to high-energy showers. [ABSTRACT FROM AUTHOR]

The negative corona discharge problem for multi-electrode geometries is modeled by a three species model. The equations are solved using domain decomposition, by recognizing that multiple species are only present in a small part of the domain, and hence only need to be incorporated locally in the model. The method is applied to an industrially relevant three wire electrostatic precipitator geometry. The calculated current density is in good agreement with experimental data. To further illustrate applications of the three species solution, it is used for coupled particle, fluid, and electrostatic simulations to analyze particle collection properties. [ABSTRACT FROM AUTHOR]

Purpose: Magnetic fields are known to alter radiation dose deposition. Before patients receive treatment using an MRI-linear accelerator (MRI-Linac), preclinical studies are needed to understand the biological consequences of magnetic-field-induced dose effects. In the present study, the authors sought to identify a beam energy and magnetic field strength combination suitable for preclinical murine experiments. Methods: Magnetic field dose effects were simulated in a mouse lung phantom using various beam energies (225 kVp, 350 kVp, 662 keV [Cs-137], 2 MV, and 1.25 MeV [Co-60]) and magnetic field strengths (0.75, 1.5, and 3 T). The resulting dose distributions were compared with those in a simulated human lung phantom irradiated with a 6 or 8MVbeam and orthogonal 1.5 T magnetic field. Results: In the human lung phantom, the authors observed a dose increase of 45% and 54% at the soft-tissue-to-lung interface and a dose decrease of 41% and 48% at the lung-to-soft-tissue interface for the 6 and 8 MV beams, respectively. In the mouse simulations, the magnetic fields had no measurable effect on the 225 or 350 kVp dose distribution. The dose increases with the Cs-137 beam for the 0.75, 1.5, and 3 T magnetic fields were 9%, 29%, and 42%, respectively. The dose decreases were 9%, 21%, and 37%. For the 2 MV beam, the dose increases were 16%, 33%, and 31% and the dose decreases were 9%, 19%, and 30%. For the Co-60 beam, the dose increases were 19%, 54%, and 44%, and the dose decreases were 19%, 42%, and 40%. Conclusions: The magnetic field dose effects in the mouse phantom using a Cs-137, 3 T combination or a Co-60, 1.5 or 3 T combination most closely resemble those in simulated human treatments with a 6 MV, 1.5 T MRI-Linac. The effects with a Co-60, 1.5 T combination most closely resemble those in simulated human treatments with an 8 MV, 1.5 T MRI-Linac. [ABSTRACT FROM AUTHOR]

The performance of a particle accelerator can be limited by the build-up of an electron cloud (EC) in the vacuum chamber. Secondary electron emission from the chamber walls can contribute to EC growth. An apparatus for in-situ measurements of the secondary electron yield (SEY) in the Cornell Electron Storage Ring (CESR) was developed in connection with EC studies for the CESR Test Accelerator program. The CESR in-situ system, in operation since 2010, allows for SEY measurements as a function of incident electron energy and angle on samples that are exposed to the accelerator environment, typically 5.3 GeV counter-rotating beams of electrons and positrons. The system was designed for periodic measurements to observe beam conditioning of the SEY with discrimination between exposure to direct photons from synchrotron radiation versus scattered photons and cloud electrons. The samples can be exchanged without venting the CESR vacuum chamber. Measurements have been done on metal surfaces and EC-mitigation coatings. The in-situ SEY apparatus and improvements to the measurement tools and techniques are described. [ABSTRACT FROM AUTHOR]

A three species model for steady-state negative corona discharge is studied. Ionization, attachment, and recombination reactions are modeled. A novel unstructured finite volume algorithm to solve the equations is presented, using the secondary emission of electrons from the cathode to set boundary values for the electrons. To show the usefulness of the method for industrial applications it is used to characterize the electrostatic properties of an externally charged rotary powder bell used in the automotive industry. Experimental current density profiles are reconstructed with good accuracy, which validates the model and the method with real experimental data. [ABSTRACT FROM AUTHOR]

Purpose: To find an optimum design of a new high-dose rate ytterbium (Yb)-169 brachytherapy source that would maximize the dose enhancement during gold nanoparticle-aided radiation therapy (GNRT), while meeting practical constraints for manufacturing a clinically relevant brachytherapy source. Methods: Four different Yb-169 source designs were considered in this investigation. The first three source models had a single encapsulation made of one of the following materials: aluminum, titanium, and stainless steel. The last source model adopted a dual encapsulation design with an inner aluminum capsule surrounding the Yb-core and an outer titanium capsule. Monte Carlo (MC) simulations using the Monte Carlo N-Particle code version 5 (MCNP5) were conducted initially to investigate the spectral changes caused by these four source designs and the associated variations in macroscopic dose enhancement across the tumor loaded with gold nanoparticles (GNPs) at 0.7% by weight. Subsequent MC simulations were performed using the EGSnrc and NOREC codes to determine the secondary electron spectra and microscopic dose enhancement as a result of irradiating the GNP-loaded tumor with the MCNP-calculated source spectra. Results: Effects of the source filter design were apparent in the current MC results. The intensity-weighted average energy of the Yb-169 source varied from 108.9 to 122.9 keV, as the source encapsulation material changed from aluminum to stainless steel. Accordingly, the macroscopic dose enhancement calculated at 1 cm away from the source changed from 51.0% to 45.3%. The sources encapsulated by titanium and aluminum/titanium combination showed similar levels of dose enhancement, 49.3% at 1 cm, and average energies of 113.0 and 112.3 keV, respectively. While the secondary electron spectra due to the investigated source designs appeared to look similar in general, some differences were noted especially in the low energy region (<50 keV) of the spectra suggesting the dependence of the photoelectron yield on the atomic number of source filter material, consistent with the macroscopic dose enhancement results. A similar trend was also shown in the so-called microscopic dose enhancement factor, for example, resulting in the maximum values of 138 and 119 for the titanium- and the stainless steel-encapsulated Yb-169 sources, respectively. Conclusions: The current results consistently show that the dose enhancement achievable from the Yb-169 source is closely related with the atomic number (Z) of source encapsulation material. While the observed range of improvement in the dose enhancement may be considered moderate after factoring all uncertainties in the MC results, the current study provides a reasonable support for the encapsulation of the Yb-core with lower-Z materials than stainless steel, for GNRT applications. Overall, the titanium capsule design can be favored over the aluminum or dual aluminum/titanium capsule designs, due to its superior structural integrity and improved safety during manufacturing and clinical use. [ABSTRACT FROM AUTHOR]

Abstract: In 2008, the Cornell Electron Storage Ring (CESR) was reconfigured to serve as a test accelerator (CesrTA) for next generation lepton colliders, in particular for the ILC damping ring. A significant part of this program has been the installation of diagnostic devices to measure and quantify the electron cloud effect, a potential limiting factor in these machines. One such device is the Retarding Field Analyzer (RFA), which provides information on the local electron cloud density and energy distribution. Several different styles of RFAs have been designed, tested, and deployed throughout the CESR ring. They have been used to study the growth of the cloud in different beam conditions, and to evaluate the efficacy of different mitigation techniques. This paper will provide an overview of RFA results obtained in a magnetic field free environment. [Copyright &y& Elsevier]

Purpose: In the scope of reference dosimetry of radiotherapy beams, Monte Carlo (MC) simulations are widely used to compute ionization chamber dose response accurately. Uncertainties related to the transport algorithm can be verified performing self-consistency tests, i.e., the so-called 'Fano cavity test.' The Fano cavity test is based on the Fano theorem, which states that under charged particle equilibrium conditions, the charged particle fluence is independent of the mass density of the media as long as the cross-sections are uniform. Such tests have not been performed yet for MC codes simulating proton transport. The objectives of this study are to design a new Fano cavity test for proton MC and to implement the methodology in two MC codes: Geant4 and PENELOPE extended to protons (PENH). Methods: The new Fano test is designed to evaluate the accuracy of proton transport. Virtual particles with an energy of E0 and a mass macroscopic cross section of [ABSTRACT FROM AUTHOR]

The air concentrations of organophosphate esters (OPEs) were studied in a network of six remote high-mountain areas of the Pyrenees located along an altitudinal profile between 1619 m and 2453 m above sea level on a restricted planar surface to assess their vertical distribution based on long-range atmospheric transport and temperature gradients. Polyurethane foam passive samplers were used in five periods spanning over three years (September 2017–October 2020). The sum of concentrations of five OPEs were between 5.3 and 100 pg m−3, averaging 16–53 pg m−3 across campaigns at the different locations. These concentrations were much lower than those observed in areas under anthropogenic influence but also than those found in low altitude remote continental sites. A significant progressive change in predominant compounds was observed along the altitudinal gradient, with prevalence of tris(1-chloro-2-propyl) phosphate (TCIPP) or tris(2-chloroethyl) phosphate (TCEP) below or above 2300 m above sea level, respectively. This trend was consistent with the higher volatility of TCEP, which was retained at greater extent at lower environmental temperatures (higher altitude). A significant temperature dependence of the gas phase concentrations was observed for TCEP, TCIPP and triphenyl phosphate (TPHP), which could be explained by retention in the cold periods, predominantly adsorbed in snow, and their release to the atmosphere during snowmelt. This mechanism was consistent with the good agreement found between the vaporization enthalpies measured under laboratory conditions and the experimental values obtained from the slopes of the significant linear regressions when representing the vertical gradients. [Display omitted] • Organophosphate esters (OPEs) in air of continental regions are lowest in mountains. • Air tris(1-chloro-2-propyl) phosphate, the most used, predominates at low altitudes. • Tris(2-chloroethyl) phosphate in air predominates at altitudes above 2300 m • The air levels of abundant OPEs are correlated with the reciprocal of temperature. • OPEs are adsorbed on mountain snow and released into the atmosphere during snowmelt. [ABSTRACT FROM AUTHOR]

Purpose: The LIonTrack (Light Ion Track) Monte Carlo (MC) code for the simulation of H+, He2+, and other light ions in liquid water is presented together with the results of a novel investigation of energy-deposition site properties from single ion tracks. Methods: The continuum distorted-wave formalism with the eikonal initial state approximation (CDW-EIS) is employed to generate the initial energy and angle of the electrons emitted in ionizing collisions of the ions with H2O molecules. The model of Dingfelder et al. ['Electron inelastic-scattering cross sections in liquid water,' Radiat. Phys. Chem. 53, 1-18 (1998); 'Comparisons of calculations with PARTRAC and NOREC: Transport of electrons in liquid water,' Radiat. Res. 169, 584-594 (2008)] is linked to the general-purpose MC code PENELOPE/penEasy to simulate the inelastic interactions of the secondary electrons in liquid water. In this way, the extended PENELOPE/penEasy code may provide an improved description of the 3D distribution of energy deposits (EDs), making it suitable for applications at the micrometer and nanometer scales. Results: Single-ionization cross sections calculated with the ab initio CDW-EIS formalism are compared to available experimental values, some of them reported very recently, and the theoretical electronic stopping powers are benchmarked against those recommended by the ICRU. The authors also analyze distinct aspects of the spatial patterns of EDs, such as the frequency of nearest-neighbor distances for various radiation qualities, and the variation of the mean specific energy imparted in nanoscopic targets located around the track. For 1 MeV/u particles, the C6+ ions generate about 15 times more clusters of six EDs within an ED distance of 3 nm than H+. Conclusions: On average clusters of two to three EDs for 1 MeV/u H+ and clusters of four to five EDs for 1 MeV/u C6+ could be expected for a modeling double strand break distance of 3.4 nm. [ABSTRACT FROM AUTHOR]

A 16-vane millimeter-wave spatial-harmonic magnetron (SHM) with a cold secondary emission cathode is examined by the use of a 3-D particle-in-cell (PIC) code embedded in CST Particle Studio. Simulations of the SHM are performed without artificial RF priming and without assuming restrictive assumptions on the mode of operation or on the number of harmonics to be considered. Thus, in our simulations, the electromagnetic oscillations grow naturally from noise. Time-evolved space-charge simulations and gradual formation of a single-frequency RF oscillation are presented. Examination of space-charge profiles at saturation time reveals the presence of two different space-charge distributions that depend on the amount of primary emission current. This current is employed to model a bombarding current, which is used to initialize the cold cathode. It is shown that a small primary emission density results in nonperiodic distribution of space charge at saturation time, which is in accordance with the previously reported space-charge distribution in SHMs. The simulated current, power, and efficiency indicate good correlation with the experimental results. [ABSTRACT FROM PUBLISHER]

Recent communication satellites are designed to cater to a constantly increasing number of users, thus demanding increasingly higher bit rates. This combination implies increasing power levels of RF equipment downstream from the power amplifiers to the OMUXs. In this situation, different discharge phenomena such as multipactor may occur inside the microwave devices, limiting the transmit power of the satellite. Multipactor suppression techniques such as surface treatment tend to degrade with time, and surface geometry modification can be a very complex operation. Due to these limitations, this work investigated, via a mathematical model, the possibility of using a DC magnetic field to effect suppression of multipaction with particular emphasis on waveguides with rectangular geometry. The result of the analysis and simulations of the model using MATLAB and MS Excel Spreadsheet applications suggested that a small magnitude DC magnetic field perpendicular to the electric field and in the wave propagation direction is effective in reducing multipaction. [ABSTRACT FROM AUTHOR]

The surface electric field (SEF) for the quasi-static negative corona discharge in atmospheric pressure air is investigated by the general fluid model which contains the continuity equations of electrons, positive ions, and negative ions coupled with Gauss' equation, considering the secondary electron emission. The SEF for the monopolar ion flow, which assumes that the whole interelectrode gap is filled with monopolar ions, is also investigated by the simplified model under the same boundary conditions at the anode. The results predict that the SEF remains constant at the onset value for both the negative corona plasma and the monopolar ion flow under a low corona current. With the increase of the corona current, the SEF is slightly strengthened for the negative corona plasma and significantly weakened for the monopolar ion flow in a wide range of conductor radii. The results for the monopolar ion flow are consistent with those deduced from the experimental data in the literature. [ABSTRACT FROM AUTHOR]

Abstract: Micro-channel plate (MCP) amplifiers are commonly used in detectors of fast time signals with picosecond resolution. The main parameters of the MCP amplifier, such as the gain factor and time resolution are strongly dependent on the work regime of the device. The saturation effects occur with a high-level input signal. In our paper these effects are studied numerically for large-area fast photo-detectors. It is shown that the saturation effect for short pulses can be reduced by introducing a thin, resistive layer between the bulk material and the emissive coating. A set of 2D and 3D numerical tools (MCP simulator, Monte Carlo simulator) was developed to simulate photo, secondary emission, fringe fields, and saturation phenomena in MCP amplifiers. The gain and time resolution dependencies on the pore size and voltage were studied numerically. The results are compared with the simulations of other authors and available experimental data. [Copyright &y& Elsevier]

Abstract: The first experimental observation of magnetic resonances in electron clouds is reported. The resonance was observed as a modulation in cloud intensity for uncoated as well as TiN-coated aluminum surfaces in the positron storage ring of the PEP-II collider at SLAC. Electron clouds frequently arise in accelerators of positively charged particles, and severely impact the machines’ performance. The TiN coating was found to be an effective remedy, reducing the cloud intensity by three orders of magnitude. [ABSTRACT FROM AUTHOR]

Abstract: To study secondary electron emission from single-walled carbon nanotubes and their visibility in scanning electron microscopy, their electronic structure is investigated in the presence of external electrons using first-principles calculations. By using the obtained nanotube charge density distribution, the energy loss of primary electrons as they pass through the electronic cloud of nanotube orbitals is estimated and it is shown that there could be enough energy transfer via inelastic scattering to allow the emission of secondaries. In addition, it is observed that the primary electron causes a major upward shift in occupied energy levels of the nanotube, effectively reducing the ionization energy and significantly increasing the secondary emission probability. It is also seen that if the nanotube has enough time to relax in response to the electric field of the primary electron, its ionization energy is lowered even more, further enhancing the secondary emission. [Copyright &y& Elsevier]

Abstract: We study herein the charge evolution of a silica amorphous target submitted to an electronic bombardment. During the bombardment, the injected electronic charge and the primary energy as well as the surface bombardment of the target are controlled. The dynamics of the injected charge are described by combining measurements of the secondary electron and X-ray emission using a scanning electron microscope. Thus, we are able to access the evolution of the surface potential and secondary electron yield. Monte-Carlo calculations are used to simulate situations similar to our experiences and to study the effect of certain parameters (density of traps, energy of activation) inaccessible to the measures with our devices. [Copyright &y& Elsevier]

Measurements of longitudinal beam profile in non-relativistic hadron accelerators are usually performed with Bunch Shape Monitors that utilize secondary electron emission to reproduce the shape of a primary ion beam. The existing devices, however, have poor electron collection efficiency from the wire and are limited to one dimensional measurements of the phase coordinate. In this paper we present the performance improvements for a bunch shape monitor for proton beams used in the Spallation Neutron Source accelerator. These improvements were achieved by adding focusing optics between the wire and the entrance slit, which will also allow measurements over a much higher dynamic range. Here we present the design, simulation and experimental test results of the developed new electron beam guidance system for the existing SNS bunch shape monitor that allowed significant improvement in the collection efficiency. [ABSTRACT FROM AUTHOR]

Abstract: Field-emission displays (FEDs) have been studied intensively in recent years as a candidate for flat-display panels in the future. In a FED, electrons emit from field emitters. Some electrons may impinge on the insulator surface between cathode and gate electrodes and cause charging of that surface because the yield of secondary electron emission is usually not equal to one. The charging of the insulator walls between cathode and gate electrodes is one of the important factors influencing the performance of a FED. In this paper, a simulation program is used to calculate this charge deposition, electric field distribution and electron trajectories. From the change of the electric field upon charge deposition in the triode region, it is shown that the insulator surface is negatively charged at a low gate voltage, e.g. 20V. However, positive charge is deposited when the gate voltage is high, e.g. 100V. The simulations also show that the emission current will increase even further after coating the dielectric with a thin film of a material with a high-secondary emission coefficient such as MgO. If a cone-shaped dielectric aperture is used in a triode, the emission current will decrease after charge deposition. However, the focus performance of the electron beam is improving in this case. [Copyright &y& Elsevier]

This study outlined the influence of a number of parameters affecting the emission rate from one of the largest sources of VOC in the building stock in the Nordic countries. This source is flooring systems of polyvinyl chloride or linoleum attached to a substrate of moisture damaged or insufficiently dried concrete. The secondary emission rate of degradation products was measured, with the Field and Laboratory Emission Cell, on different flooring systems consisting of three different floorings and three adhesives, exposed to three different aqueous solutions in the range of 11–13.1 pH. The conclusion drawn in this study is that the great majority of the secondary emission originates from the floor adhesive. The occurrence of adhesive and the amount of adhesive used have a significant influence on the emission rate. A critical pH value for degradation of the adhesive seems to lie somewhere between 11 and 13 pH. Practical Implications When designing a floor system or a renovation of a damaged flooring system, it is important to bear in mind the influence of parameters that may drastically shorten the service life. Flooring adhesive may decompose in a moist alkaline environment and give rise to unacceptable secondary emission rates. [ABSTRACT FROM AUTHOR]

The surface potential of dust grains immersed in surrounding plasma results from the balance of many charging processes such as photoemission, electron/ion attachments, and secondary and field emissions. Since hot electrons are often present in space as well as laboratory plasmas, the understanding of the secondary electron (SE) emission process for small dust grains is of great interest because their size effects modify well-known characteristics of large samples. This paper compares the measured surface potential of SiO2 spherical dust grains with the results of the Monte Carlo model of secondary emission developed for metallic samples. It was found that 1) the model can be used for description of the secondary emission process from cosmic dust, 2) the backscattering of primary beam electrons is the most important factor for the charging of small grains, and 3) the actual value of the surface grain potential is given by the energy spectrum of SEs. [ABSTRACT FROM AUTHOR]

Abstract: Dust grains are common in the space environment and being immersed in plasma, they become charged. It is well known that a motion of grains in space is driven mainly by electrodynamic forces and thus the grain charge is important for processes like the coagulation or dust cloud formations. Among other charging currents, emission processes are very important for setting the dust charge. It is believed that emission processes are connected exclusively with surface properties of dust grains but it is not evident for the surfaces covered by a very thin layer of different material (e.g., oxidized metal). For this reason, we investigate surface effects experimentally. Our experiment is based on an 3D electrodynamic trap. We caught a single dust grain for several days inside the vacuum vessel and exposed it to the electron/ion beam and studied charging/discharging processes. We have chosen spherically shaped melamine formaldehyde resin grains of a diameter 2.35 μm either with a clean surface or covered with a thin nickel film. An advantage of these samples is that the properties of bulk and surface materials are completely different. The effect of a surface modification was studied for ion and electron field emissions. We determined field intensities needed for significant emission currents as well as effective work functions for charged dust grains of particular material. [Copyright &y& Elsevier]

Abstract: The motion, coalescence, and other processes in dust clouds are determined by the dust charge. Since dust grains in the space are bombarded by energetic electrons, the secondary emission is an important process contributing to their charge. It is generally expected that the secondary emission yield is related to surface properties of the bombarded body. However, it is well known that secondary emission from small bodies is determined not only by their composition but an effect of dimension can be very important when the penetration depth of primary electrons is comparable with the grain size. It implies that the secondary emission yield can be influenced by the substrate material if the surface layer is thin enough. We have developed a simple Monte Carlo model of secondary emission that was successfully applied on the dust stimulants from glass and melamine formaldehyde (MF) resin and matched very well experimental results. In order to check the influence of surface layers, we have modified the model for spheres covered by a layer with different material properties. The results of model simulations are compared with measurements on MF spheres covered by a nickel layer. [Copyright &y& Elsevier]

The dynamics of the ramp discharge is studied via kinetic particle-in-cell/Monte Carlo simulations. It is shown that a plasma display panel cell is a fundamentally "small" system and fluctuations of the number of charged particles in the discharge gap strongly influence the dynamics of the ramp discharge and may even lead to its disruption. The common view of ramps based on multicell or time averaged measurements and corresponding fluid theoretical descriptions are inadequate. The role of exoemission as a possible stabilizer of the discharge is clarified. [ABSTRACT FROM PUBLISHER]

Abstract: The feasibility of a metal liner for controlling the wall current has been studied for the positive pulse bias (PPB) method, a new proposing method of the PBII process. In the PPB method, the plasma is positively biased with respect to the grounded workpiece. While it has merits over a negative pulse bias (NPB) method, it requires an enclosure or a liner to suppress the electrical current to the chamber wall. We have tested a floating stainless steel liner in place of the Kapton liner previously used to avoid plasma contamination; the plasma floating potential, the ion energy spectrum on a disc target and the ion current distribution on a trench target have been investigated in an argon plasma of 1015 m−3 supplied into the liner from the ICP source. The results have proved that the metal liner is quite suitable for the PPB method. [Copyright &y& Elsevier]