Ion Tail Research Articles

Semiconductor WO3 thin films deposited by pulsed reactive magnetron sputtering

A pulsed reactive magnetron sputtering system with a tungsten target and a gas mixture of argon and oxygen was investigated as a source for the deposition of semiconductor WO3 thin films on soda lime glass substrates and on the glass with transparent conductive SnO2:F (FTO) electrode. The reactive sputtering process was performed in HiPIMS mode with low pulse repetition frequency fp ≈ 50–100 Hz and short pulse duration in HiPIMS discharge Ton = 100 μs. The second mode investigated was the mid-frequency (MF) magnetron discharge with pulse frequency fp = 40 kHz and pulse length Ton = 15 μs. The plasma parameters were investigated for both HiPIMS and MF modes using the planar RF probe operating at the frequency fprobe = 350 kHz and the grid QCM with biased collector electrode. Ion density ni and tail electron temperature (Te) were determined in both pulsed reactive magnetron sputtering discharge modes with time resolution. The maximum value ni ≈ 5 · 1017 m−3 was found in the reactive HiPIMS mode, and the maximum value ni ≈ 7 · 1016 m−3 was found in the reactive MF (40 kHz) mode. The degree of ionization of sputtered particles in reactive HiPIMS was determined for different values of (QO2) and was found to be in the range of ri ≈ 0.1–0.3. The deposition rate determined by QCM in reactive HiPIMS was practically independent on (QO2), but in the case of reactive MF, the measured deposition rate decreased significantly with increasing (QO2). The WO3 films deposited in both modes have a predominantly monoclinic crystal structure. The light and dark conductivity and the light/dark conductivity ratio (Ld) were measured under dark conditions and UV light illumination. At higher (QO2), the maximum value of Ld ≈ 300 was found for MF deposited WO3 and the maximum value of Ld ≈ 30 was found for HiPIMS deposited WO3. The photoelectrochemical measurement of WO3 deposited on FTO electrodes confirmed the n-type conductivity, and these films functioned as photoanodes in photoelectrochemical cells. MF deposited WO3 films systematically exhibited slightly higher photocurrents than HiPIMS deposited WO3. It was shown that these optimum photocurrents for HiPIMS and MF were found at QO2 ≈ 80 sccm and could not be improved by further increasing of (QO2).

Prospects for the Crossing by Earth of Comet C/2023 A3 Tsuchinshan-ATLAS’s Ion Tail

The Earth will pass approximately downstream of the previous position of comet C/2023 A3 (Tsuchinshan-ATLAS) during 2024 October 10–13. We predict that spacecraft at the Sun–Earth Lagrange Point 1, L1, have a significant likelihood to detect pickup ions from the comet, as well as changes in the solar wind associated with the crossing of the comet’s ion tail. Given the Earth’s magnetosphere is also likely to cross the ion tail, it is possible that geomagnetic signatures associated with this will be observed by spacecraft within the magnetosphere and possible at ground-based magnetometers, as observed during Comet 1P/Halley’s apparition in 1910.

New evidence supporting past dust ejections from active asteroid (4015) Wilson–Harrington

Context. (4015) Wilson-Harrington (hereafter, WH) was discovered as a comet in 1949 but has a dynamical property consistent with that of a near-Earth asteroid. Although there is a report that the 1949 activity is associated with an ion tail, the cause of the activity has not yet been identified. Aims. This work aims to reveal the mysterious comet-like activity of the near-Earth asteroid. Methods. We conducted new polarimetric observations of WH from May 2022 to January 2023, reanalyses of the photographic plate images taken at the time of its discovery in 1949, and dust tail simulation modelings, where the dust terminal velocity and ejection epoch are taken into account. Results. We found that this object shows polarization characteristics similar to those of low-albedo asteroids. We derived the geometric albedo ranging from pV = 0.076 ± 0.010 to pV = 0.094 ± 0.018 from our polarimetry (the values vary depending on the data used for fitting and the slope-albedo relationship coefficients). In addition, the 1949 image showed an increase in brightness around the nucleus. Furthermore, we found that the color of the tail is consistent with sunlight, suggesting that the 1949 activity is associated with dust ejection. From the dust tail analysis, ~9 × 105 kg of material was ejected episodically at a low velocity equivalent to or even slower than the escape velocity. Conclusions. We conclude that WH is most likely an active asteroid of main belt origin and that the activity in 1949 was likely triggered by mass shedding due to fast rotation.

A physics-informed deep learning description of Knudsen layer reactivity reduction

A physics-informed neural network (PINN) is used to evaluate the fast ion distribution in the hot spot of an inertial confinement fusion target. The use of tailored input and output layers to the neural network is shown to enable a PINN to learn the parametric solution to the Vlasov–Fokker–Planck equation in the absence of any synthetic or experimental data. As an explicit demonstration of the approach, the specific problem of Knudsen layer fusion yield reduction is treated. Here, the predictions from the Vlasov–Fokker–Planck PINN are used to provide a non-perturbative solution of the fast ion tail in the vicinity of the hot spot, thus allowing the spatial profile of the fusion reactivity to be evaluated for a range of collisionalities and hot spot conditions. Excellent agreement is found between the predictions of the Vlasov–Fokker–Planck PINN and the results from traditional numerical solvers with respect to both the energy and spatial distribution of fast ions and the fusion reactivity profile, demonstrating that the Vlasov–Fokker–Planck PINN provides an accurate and efficient means of determining the impact of Knudsen layer yield reduction across a broad range of plasma conditions.

Ion kinetic effects on the formation of intense laser-driven shock waves

The ion kinetic effect on the formation of intense laser-driven collisional shock waves is investigated via hybrid fluid-particle-in-cell simulations. It is found that the ion heat flux dominates the shock formation, which is considerably larger than the electron heat flux in the shock region. The rise of the temperature due to the laser energy deposition drives a heatwave into the overdense plasma, creating an electron–ion energy exchange zone between the critical surface and heat wave front. The heated ions, which are generated at the electron–ion energy exchange zone via the friction force, are found to travel to the high-density region and cause a tail distribution gain. Despite the small quantity, the heated tail ions contribute most of the ion heat flux during the shock formation. Additionally, as the electron heat flux decreases, the population of the heated tail ions is reduced, leading to a fall in the ion heat flux. This results in the delay or even suppression of the shock formation, because the ions are in a non-equilibrium state in the vicinity of the shock region, the ratio of the downstream ion temperature to the upstream ion temperature tends to a modestly decrease in comparison to the theory. The study provides a clear picture of the formation process of laser-driven shock waves.

Signal shapes in multiwire proportional chamber-based TPCs

A large-volume Time Projection Chamber (TPC) is the main tracking and particle identification (PID) detector of the ALICE experiment at the CERN LHC. PID in the TPC is performed via specific energy-loss measurements (dE/dx), which are derived from the average pulse-height distribution of ionization generated by charged-particle tracks traversing the TPC volume. During Runs 1 and 2, until 2018, the gas amplification stage was based on multiwire proportional chambers (MWPC). Signals from the MWPC show characteristic long negative tails after an initial positive peak due to the long ion drift times in the MWPC amplification region. This so-called ion tail can lead to a significant amplitude loss in subsequently measured signals, especially in the high-multiplicity environment of high-energy Pb-Pb collisions, which results in a degradation of the dE/dx resolution. A detailed study of the signal shapes measured with the ALICE TPC with the Ne-CO2 (90-10) and Ar-CO2 (90-10) gas mixtures is presented, and the results are compared with three-dimensional Garfield simulations. The impact of the ion tail on the PID performance is studied employing the ALICE simulation framework and the feasibility of an offline correction procedure to account for the ion tail is demonstrated.

Suprathermal H+ Pickup Ion Tails in the Outer Heliosphere

This study provides a detailed analysis of five distant interplanetary shocks observed by the Solar Wind Around Pluto instrument on board New Horizons, which exhibit the signature of a suprathermal H+ pickup ion (PUI) tail in the downstream distribution. These shocks were observed with a PUI data cadence of approximately 24 hr, covering a heliocentric distance range of 23.71–36.75 au. The shock compression ratio varies between approximately 1.4 and 3.2. The H+ PUI density and temperature show a gradual increase across the shock, while the H+ solar wind density shows erratic behavior without a distinct downstream compression. The H+ PUI cooling index variation across the shock displays different characteristics in each shock. This study demonstrates, for the first time, the variation of the number density of downstream H+ PUI tails with the shock compression ratio, revealing an increase in tail density with stronger shocks. Additionally, theoretical estimates of reflected PUI number densities derived from the electrostatic cross-shock potential agree very well with the observed H+ PUI tail densities for stronger shocks.

Correction of the baseline fluctuations in the GEM-based ALICE TPC

To operate the ALICE Time Projection Chamber in continuous mode during the Run 3 and Run 4 data-taking periods of the Large Hadron Collider, the multi-wire proportional chamber-based readout was replaced with gas-electron multipliers. As expected, the detector performance is affected by the so-called common-mode effect, which leads to significant baseline fluctuations. A detailed study of the pulse shape with the new readout has revealed that it is also affected by ion tails. Since reconstruction and data compression are performed fully online, these effects must be corrected at the hardware level in the FPGA-based common readout units. The characteristics of the common-mode effect and of the ion tail, as well as the algorithms developed for their online correction, are described in this paper. The common-mode dependencies are studied using machine-learning techniques. Toy Monte Carlo simulations are performed to illustrate the importance of online corrections and to investigate the performance of the developed algorithms.

Experiments in high-performance JET plasmas in preparation of second harmonic ICRF heating of tritium in ITER

The reference ion cyclotron resonance frequency (ICRF) heating schemes for ITER deuterium–tritium (D-T) plasmas at the full magnetic field of 5.3 T are second harmonic heating of T and 3He minority heating. The wave-particle resonance location for these schemes coincide and are central at a wave frequency of 53 MHz at 5.3 T. Experiments have been carried out in the second major D-T campaign (DTE2) at JET, and in its prior D campaigns, to integrate these ICRF scenarios in JET high-performance plasmas and to compare their performance with the commonly used hydrogen (H) minority heating. In 50:50 D:T plasmas, up to 35% and 5% larger fusion power and diamagnetic energy content, respectively, were obtained with second harmonic heating of T as compared to H minority heating at comparable total input powers and gas injection rates. The core ion temperature was up to 30% and 20% higher with second harmonic T and 3He minority heating, respectively, with respect to H minority heating. These are favourable results for the use of these scenarios in ITER and future fusion reactors. According to modelling, adding ICRF heating to neutral beam injection using D and T beams resulted in a 10%–20% increase of on-axis bulk ion heating in the D-T plasmas due to its localisation in the plasma core. Central power deposition was confirmed with the break-in-slope and fast Fourier transform analysis of ion and electron temperature in response to ICRF modulation. The tail temperature of fast ICRF-accelerated tritons, their enhancement of the fusion yield and time behaviour as measured by an upgraded magnetic proton recoil spectrometer and neutral particle analyser were found in agreement with theoretical predictions. No losses of ICRF-accelerated ions were observed by fast ion detectors, which was as expected given the high plasma density of n e ≈ 7–8 × 1019 m−3 in the main heating phase that limited the formation of ICRF-accelerated fast ion tails. 3He was introduced in the machine by 3He gas injection, and the 3He concentration was measured by a high-resolution optical penning gauge in the sub-divertor region. The DTE2 experiments with 3He minority heating were carried with a low 3He concentration in the range of 2%–4% given the fact that the highest neutron rates with 3He minority heating in D plasmas were obtained at low 3He concentrations of ∼2%, which also coincided with the highest plasma diamagnetic energy content. In addition to 3He introduced by 3He gas injection, an intrinsic concentration of 3He of the order of 0.2%–0.4% was measured in D-T plasmas before 3He was introduced in the device, which is attributed to the radioactive decay of tritium to 3He. According to modelling, even such low intrinsic concentrations of 3He lead to significant changes in ICRF power partitioning during second harmonic heating of T due to absorption of up to 30% of the wave power by 3He.

On the characteristics of DA shock waves in a polarized electron-depleted plasma with a mixed nonextensive high energy-tail ion distribution

A first theoretical attempt is made to understand the characteristics of dust acoustic shock waves (DASWs) in a polarized electron-depleted plasma with a mixed nonextensive high energy–tail ion distribution and to examine the impact of the generalized nonthermal polarization force on DASWs in an electron-depleted dusty plasma. First, a short numerical investigation illustrating the behavior of the mixed nonextensive high energy–tail (or Cairns–Tsallis) ion distribution and the domain of validity of its two parameters (q and [Formula: see text]) is carried out. Next, the generalized nonthermal polarization acting on dust grain in electron-depleted dusty plasma is determined within the context of Tsallis’ statistical mechanics. The behavior of this generalized polarization force is significantly affected by the nonextensive character of the nonthermal ions. Specifically, we have shown that, for both space and experimental dusty plasmas, the magnitude of the polarization force (in the case where [Formula: see text]) decreases as the nonextensivity of the nonthermal ions becomes significant. As an application, we have analyzed the changes caused by the nonthermal nonextensive polarization force on the main characteristics of DASW (viz. phase velocity, polarity, amplitude, width, etc.). Numerical results showed that our plasma model supports rarefactive and compressive DASWs that are significantly affected by the effects of nonthermal ion nonextensivity and polarization force. In particular, we have shown that for large values of the nonthermal parameter [Formula: see text], the increase in q allows the transition from rarefactive to compressive DASW structures. The present theoretical investigation is helpful to fully understand electrostatic disturbances in space and experimental dusty plasmas.

N2/CO ratio in comets insensitive to orbital evolution

ABSTRACT Comets are seen as depleted in nitrogen compared to the protosolar value, but a small number exhibit significantly higher than typical N2/CO ratios: C/1908 R1 (Morehouse), C/1940 R2 (Cunningham), C/1947 S1 (Bester), C/1956 R1 (Arend–Roland), C/1957 P1 (Mrkos), C/1961 R1 (Humason), C/1969 Y1 (Bennett), C/1973 E1 (Kohoutek), C/1975 V1-A (West), C/1986 P1 (Wilson), C/1987 P1 (Bradfield), C/2001 Q4 (NEAT), C/2002 VQ94 (LINEAR), C/2016 R2 (PanSTARRS), and periodic comets 1P/Halley, 29P/Schwassmann–Wachmann 1, and 67P/Churyumov–Gerasimenko. This study examines the composition and dynamical histories of these N2-‘rich’ comets to unearth insights into their formation processes. Using updated N2 fluorescence factors, we re-estimate the N2/CO ratios of this sample and find that they are consistent with the expected values for comets based on estimations of the protosolar nebula. These also often display larger nucleus sizes and show rapid tail morphology variations due to their ionic nature. Numerical simulations reveal no common dynamical history, suggesting that the N2/CO ratio is independent of the number of inner Solar System passages and that N2 is homogeneously distributed within these comets. These volatile-rich comets share an Oort Cloud origin which is consistent with their survival over the past 4.5 Gyr. Our study also suggests that there may be a bias using modern high-resolution spectrometers with narrow slits, which could potentially overlook the ion tail of comets. We advocate for the use of long-slit spectroscopy to potentially detect a wider range of N2-rich comets, thereby enriching our understanding of comet compositions and origins.

Influence of ICRF-NBI synergy on fast ion distribution and plasma performance in second harmonic heating experiments with deuterium NBI at EAST

Ion Cyclotron Range of Frequencies (ICRF) heating and Neutral Beam Injection (NBI) can have synergy due to the acceleration of NBI beam ions by ICRF wave fields at their harmonics. To understand the influence of ICRF-NBI synergy on fast ion distribution and plasma performance, dedicated experiments and TRANSP simulations have been carried out on EAST. The simulation results are consistent with the experimental results. They show that the ICRF-NBI synergy not only accelerates the NBI beam ions with energy lower than 80 keV to energy larger than 300 keV, but also generates fusion neutrons with energy larger than 3 MeV. Moreover, ICRF-NBI synergy improves the plasma performance by increasing the poloidal beta, plasma stored energy, core ion temperature, total neutron yield and kinetic pressure. In a typical H-mode plasma with 1.0 MW NBI and 1.5 MW ICRF power, it was observed that ICRF-NBI synergy increases the poloidal beta, plasma stored energy, core ion temperature and neutron yield by ∼35%, 33%, 22% and 80%, respectively. Various parameter scans show that the ICRF-NBI synergetic effects can be enhanced by decreasing the minority ion concentration or the distance between the harmonic resonance and magnetic axis, or by increasing the ICRF heating power or NBI beam energy. Consequently, this leads to a generation of fast ions with higher energy. For instance, the maximum energy of the fast ion tail increases from 300 to 600 keV as n(H) decreases from 5% to 0.1%.

Fast ion generation by combined RF-NBI heating in W7-X

Good fast ion confinement in quasi-isodynamic stellarators still has to be demonstrated experimentally. In the absence of fusion alphas, auxiliary heating systems can be used to generate fast ions. For this purpose, W7-X has neutral beam injection and its newly installed ion cyclotron heating system. In practice, both systems can run simultaneously, the synergetic running of both is the focus of the current modelling development. With the upgrades to the SCENIC code described here, we find that, compared with pure neutral beam injection (NBI), the fast ion tail is significantly enhanced when radio frequency (RF) heating is enabled. But the effectiveness of heating and fast ion tail generation strongly depends on the plasma parameters and antenna frequency, which calls for further study, both numerical and experimental.

First results from third harmonic ion cyclotron acceleration of deuterium beams in EAST ion heating studies experiments

Recent Experimental Advanced Superconductivity Tokamak experiments have been dedicated to the studies of increasing ion temperature using Neutral Beam Injection (NBI) in synergy with radio-frequency waves in the Ion Cyclotron Range of Frequencies (ICRFs) in third harmonic. They showed that this scenario effectively accelerates fast deuterium ions and produces a larger tail of fast neutrons with E > 3.0 MeV, as measured by Neutron Energy Spectrum. Comparing to the scenario with 2.2 MW NBI alone, adding an addition of 0.3 MW ICRF power leads to an enhancement of fusion yield by 67% (from to ) and an increase of core ion temperature by . Besides, the simulation results of TRANSP show that the neutron yield produced by 0.2 MW ICRF in third harmonic with NBI synergy is roughly consistent with the experimental results. Meanwhile, the 80 keV fast ion tail generated by NBI can be heated up to 400 keV and 600 keV by the 0.2 MW and 1.0 MW ICRF with the synergistic effect, respectively. In addition, it is observed for the first time that this ICRF-NBI synergy leads to the excitation of fishbone instabilities with characteristic frequencies of (10–20) kHz. Furthermore, parameter scans of ICRF/NBI power and plasma density were performed for third harmonic ICRF and NBI synergetic heating schemes. It is found that the neutron yield increases nonlinearly as the ICRF power or plasma density increases.

Cometary ions detected by the Cassini spacecraft 6.5 au downstream of Comet 153P/Ikeya–Zhang

During March–April 2002, while between the orbits of Jupiter and Saturn, the Cassini spacecraft detected a significant enhancement in pickup proton flux. The most likely explanation for this enhancement was the addition of protons to the solar wind by the ionization of neutral hydrogen in the corona of comet 153P/Ikeya–Zhang. This comet passed relatively close to the Sun–Cassini line during that period, allowing pickup ions to be carried to Cassini by the solar wind. This pickup proton flux could have been further modulated by the passage of the interplanetary counterparts of coronal mass ejections past the comet and spacecraft. The radial distance of 6.5 Astronomical Units (au) traveled by the pickup protons, and the implied total tail length of >7.5 au make this cometary ion tail the longest yet measured.

Solar Wind Velocities at Comets C/2011 L4 Pan‐STARRS and C/2013 R1 Lovejoy Derived Using a New Image Analysis Technique

AbstractThe ion tails of bright comets have long been considered as a natural tracers of the solar wind (SW) near these objects. Studies of comets and their ion tails allow inexpensive monitoring of key SW structures in the inner heliosphere, much of which is otherwise only accessible by in situ SW spacecraft measurements. Here, we present a novel technique to mine the rich archive of amateur, professional and spacecraft observations of cometary ion tails. To demonstrate this, we focus on Near‐Sun comet C/2011 L4 (Pan‐STARRS) during Carrington Rotations (CR) 2134 and 2135 and comet C/2013 R1 (Lovejoy) during CR 2118. We outline the technique’s shortcomings, including its geometric limitations, and present a catalog of radial SW velocities derived in the near‐comet environment and information on the heliospheric conditions inferred from the measured SW. Complementary measurements, derived from folding ion rays and a velocity profile map built from consecutive images, are provided as an alternative means of quantifying the SW ‐cometary ionosphere interaction. We find that comets are generally good indicators of SW structure, but the quality of the results is strongly dependent on the observing geometry.

Ultraviolet Observations of Comet 96/P Machholz at Perihelion

Abstract Ultraviolet spectra of Comet 96/P Machholz were obtained during its 2002 perihelion with the UltraViolet Coronagraph Spectrometer instrument on board the SOHO satellite. Emission from H i, C ii, C iii, and O i is detected near the nucleus. The outgassing rate is in line with the value extrapolated from rates at larger distances from the Sun, and abundances of C and O are estimated. Reconstructed images show a nearly spherical cloud of H i Lyα emission and an ion tail seen in C iii. Radiation pressure on the hydrogen atoms produces a modest distortion of the shape of the Lyα cloud as seen from SOHO and Doppler shifts up to 30 km s−1 in the outer parts of the cloud. We estimate a ratio of C to H2O similar to what is observed in other comets, so low carbon abundance does not account for the anomalously low C2 and C3 ratios to NH2 observed at optical wavelengths.

Space‐Ground Observations of Dynamics of Substorm Onset Beads

AbstractWe present observations during two substorms using simultaneous Time History of Events and Macroscale Interactions During Substorms satellites and all‐sky imagers to determine plasma sheet dynamics associated with substorm auroral onset beads. The multi‐satellite observations showed that the cross‐tail current decreased and the field‐aligned currents increased at the substorm auroral onset, indicating that the satellites detected an initiation of the currents being deflected to the ionosphere. For duskward‐propagating beads, the electric field was tailward, and ions were accumulated closer to the Earth than electrons. The mapped bead propagation speed was close to energetic ion drift speed. The and electron drift speeds increased duskward and reduced the cross‐tail current at the onset. For dawnward‐propagating beads, the electric field was equatorward/earthward, and electrons were inferred to accumulate earthward of ions. The mapped bead propagation speed was comparable to the dawnward and electron drift speeds. The duskward ion drift and tail current were reduced, and electrons became the dominant current carrier. We suggest that the plasma species that is responsible for the bead propagation changes with the electric field configuration and that the tail current reduction by the enhanced drift at onset destabilizes the plasma sheet. Ion and electron outflows substantially increased low‐energy plasma density and may have increased the role of drifts. The bead wavelength was comparable to ion gyroradius and thus ion kinetic effects are important for determining the wavelength. In the dawnward‐propagating event, the mode of oscillation in the plasma sheet was suggested to be the sausage‐mode flapping oscillations.

ICRF modelling in 2D and 3D magnetic configurations using a hot plasma model

The generation of energetic trapped ions is important for experiments investigating their confinement in 3D magnetic fields, for plasma heating, for studies into unwanted drive of instabilities, and improved transport regimes. An effective way to generate such energetic ions is with ion cyclotron resonance heating. SCENIC is a tool built to self consistently model the magnetic equilibrium, the radio frequency wave, and the minority distribution function in steady state. In this paper the impact of higher order finite Larmor radius corrections in the dielectric tensor will be described. The RF electric field and the power deposition in the new hot model are compared against the previously used warm model for several JET plasmas. Considerable differences are found in some of the scenarios. The new version of the wave code LEMan also supports the direct use of particle-in-cell marker data to compute the dielectric tensor. An expression for the dielectric tensor is derived, and it is applied to a test case in JET. The power deposition profile agrees very well with that of a Maxwellian reference case, which is promising for future applications. Moreover, a full SCENIC run shows a significantly enhanced fast ion tail. In a demonstration of the novel features of LEMan, it is also applied to minority heating in the intrinsically 3D plasma of W7-X.

Numerical investigation of a new ICRF heating scenario in D-T plasma on CFETR

For a fusion device, plasma pre-heating is required before the self-sustaining burning-state reactions of deuterium (D) and tritium (T) commence. Plasma heating with waves in the ion-cyclotron range of frequencies (ICRF) is effective in tokamaks. A new three-ion ICRF heating scheme for plasmas in the Chinese Fusion Engineering Test Reactor (CFETR) that require an increase in the bulk ion temperature via heating the lithium impurities in the D–T plasmas, was studied numerically. Our simulations show that the radio-frequency wave power is strongly absorbed by very few 7Li ions with concentrations of 0.01%–0.2% in a suitable mixture of D–T plasmas, the enhanced minority ion heating is related to that the 7Li fundamental resonance layer is very close to the two mode conversion layers. In adjusting the mixtures over a wide range of composition, an oscillatory behaviour in the 7Li absorption efficiency arises because of interference. Moreover, from estimates of the 7Li ion tail energy, most of the tail energy of the minority ions is found to be transferred to background ions via collisions. Compared with the routine (3He)-D–T scheme, the ICRF power is absorbed more effectively by the 7Li ions in the (7Li)-D–T heating scenario, and after the Fokker–Planck equations were solved, a large fraction of bulk ion heating was evident in the (7Li)-D–T heating scenario. The new three-ion scenario may therefore be an attractive proposition for bulk ion heating during the activated phase of the reactor.