Drift Velocity Vd Research Articles

Gas-phase ion mobility of protonated aldehydes in helium measured using a selected ion flow-drift tube.

In soft chemical ionization mass spectrometry, analyte ions are produced via ion-molecule reactions in the reactor. When an electric field E is imposed, the ion drift velocity vd determines the reaction time and the effective ion temperature. Agreement between experimental ion mobilities and theoretical predictions confirms the accuracy of the ion residence time measurement procedure. A selected ion flow-drift tube (SIFDT), an instrument with a chemical ionization source, was used to produce protonated aldehydes and selectively inject them into the resistive glass drift tube filled with He. Arrival-time distributions of ions were obtained using the Hadamard modulation. Reduced ion mobilities were then obtained at a pressure of 2hPa in the E/N range of 5-15 Td. Theoretical ion mobility values were calculated using two methods: hard-sphere approximation and trajectory modelling. The measured mobilities of three saturated and three unsaturated protonated aldehydes do not show substantial variation across the studied E/N range. Effective temperatures calculated using the Wannier formula from measured gas temperatures ranged from 300 to 315 K. Experimentally obtained values of the near-zero- E/N-reduced ion mobilities agree with both methods of calculations typically within ±3% standard deviation (maximum ±5%). The experimental SIFDT values of reduced mobilities in He of protonated aldehyde molecules generated from a chemical ionization source are in close agreement with two different theoretical methods based on the density functional theory calculations of ion geometries and partial atomic charges. Besides its fundamental importance, the ion mobility results validate the correct operation of the drift tube reactor and the ion residence time measurement procedure. Diffusion losses can also be determined from these results.

High frequency amplification of acoustic phonons in fluorine-doped single-walled carbon nanotubes

Herein, we report on a strong high-frequency induced amplification of coherent acoustic phonons in a non-degenerate fluorine-doped single-walled carbon nanotubes (FSWCNTs) by utilising a tractable analytical approach in the hypersound regime, ql≫1 (where q is the acoustic wavenumber and l is the carrier mean free path). The acoustoelectric gain obtained is highly nonlinear and is due to stimulated Cerenkov phonon emission by electrically driven carriers undergoing intraminiband transport and capable of performing Bloch oscillations. The transport process causes the carriers to undergo population inversion leading to intraminiband phonon-assisted processes. The generation rate (phonon emission) is expansive and surpasses phonon losses. The threshold field (Eo), at which attenuation switches over to amplification (gain) depends on the FSWCNT parameters (Δs&Δz), carrier drift velocity (vd=μEo), sound velocity (vs) and the ratio ζs,z. This result has potential for intense sources of reasonable acoustic phonons in the sub-THz regime and is vital for the generation of SASER (sound amplification by stimulated emission of acoustic radiation). The amplified phonons also have THz frequencies with wavelengths in the nanometer range, and depends on high spatial parameters which has potential applications for phonon filters and spectrometers.

Measurement of Ion Energy Distribution Function of Fast Plasma Flow Driven by Plasma Focus Device Using Retarding Field Energy Analyzer

To understand the mechanism of particle acceleration in collisionless shocks, generating a collisionless plasma flowing through dilute gas is required. We have proposed a compact plasma focus (CPF) device to generate collisionless plasma by using pulsed-power discharge. To discuss a particle acceleration process in collisionless shocks, it is necessary to evaluate an ion energy distribution function (IEDF) of the plasma. In this study, we measured the IEDF of the plasma flow using a retarding field energy analyzer (RFA). The experimental results measured by the RFA showed that ions with a few eV are dominant in the plasma flow generated by the CPF device. The IEDF could be fitted with the shifted Maxwellian distribution. The plasma parameters were estimated to be the ion number density ni = 4.6+−00..28 × 1019 m−3, the ion temperature Ti = 0.8+−00..64 eV, and the drift velocity vd = 11+−03..55 km/s. The estimated velocity approximately agreed with the result of a time-of-flight method calculated by the ion current waveform.

Nighttime morphology of vertical plasma drifts over Vietnam during different seasons and phases of sunspot cycles

This study is the first to provide the nighttime morphology of vertical plasma drifts over Vietnam at the equatorial trough and the northern tropical crest of ionization anomaly in the Asian sector. We use the h’F data in Vietnam from Bac Lieu observatory (9.28°N, 105.73°E, dip: 1.73°N) during the 2006–2019 period and Phu Thuy observatory (21.03°N, 105.96°E, dip: 14.49°N) for the 1964–2011 period, to calculate the vertical plasma drift velocity (Vd) and analyze the annual, seasonal, sunspot cycle, and sunspot cycle (SC) phase evolutions. For Bac Lieu, the PRE and minimum reversal peaks evolve according to the sunspot cycles. The seasonal average of the drift pattern shows that the PRE peak appears earlier one hour in summer (1800 LT) than in equinoxes and winter (1900 LT) and the minimum reversal peak occurred about 2100–2200 LT, except in summer, in which this peak identifies around 0100 LT. This drift pattern exhibits a semiannual asymmetry during PRE/minimum reversal periods with peaks in March and September/October. The evening-time pre-reversal enhancement (PRE)at Bac Lieu is dependent on the phase of the sunspot cycle. For Phu Thuy, the mean annual peak magnitudes of Vd during the PRE and minimum reversal periods exhibit a poor correlation with the sunspot number (Rz). For the SC seasonal variation, the lowest PRE peak magnitude in autumn appeared one hour later compared with winter, one hour earlier than summer, and the same time as spring, while the minimum reversal peak is larger in summer for SCs 20–23 and in autumn for SCs 20, 23, and 24 at around 0200–0300 LT than in another season at about 2000, 2200, and 2300 LT. The morphology of the seasonal average variations of Vd is rather similar for all SCs except SC 24 at Phu Thuy. The PRE peak during the high solar activity years (2000 LT) appears earlier about 4 h than that during the low solar years (at 2300 LT/0000 LT). The monthly average of plasma drift also exhibits semiannual asymmetry during PRE events for cycles 22, 24, and minimum reversal period for cycle 24 with peaks in March and September. In addition, it shows an annual variation for the remaining cycles during PRE/minimum reversal periods with peaks in the summer months. The pre-sunrise enhancement characteristic (0500 LT) was observed during all seasons and phases (ascending, descending, minimum) at Bac Lieu, summer for all SCs, equinoxes for SC 24, the ascending and minimum phases for the SC 24, and the descending phase for the SC 23 at Phu Thuy.

Electrical properties of a newly synthesized potassium ion conducting solid polymer electrolytes

Electrical properties of a newly synthesized K+ ion conducting solid polymer electrolytes (SPEs): (1-x)PEO: xKCl, where 0 ≤ x ≤ 50 in wt%., are reported. Electrical properties of newly synthesized SPEs have been investigated with the help of ionic conductivity (σ), ionic mobility (µ), mobile ion concentration (n), ionic transference number (tion) and ionic drift velocity (vd) studies at room temperature and above. Polymer-salt complexation has been carried out with the help of scanning electron micrograph (SEM) and thermo-gravimetric analysis (TGA). The overall increase in ionic conductivity of the current SPE is due to the increase in both µ and n.

Temperature dependent ionic parameter studies of a newly synthesized Na+ ion conducting nanocomposite polymer electrolytes

Temperature dependent ionic parameter studies of a newly synthesized Na+ ion conducting nanocomposite polymer electrolytes (NCPEs): 95[75PEO:25NaPO3] + 5TiO2 where 0 ≤ x ≤ 18 wt%, are reported. The present NCPEs films have been synthesized using a recently developed hot-press method. The some important basic ionic parameters viz. ionic conductivity (σ), ionic mobility (μ), mobile ion concentration (n), ionic transference number (tion) and ionic drift velocity (vd) have been calculated with the help of various experimental techniques. Ion conduction behaviour has been explained by various models.

Comparative analysis of ionosonde spread F and GPS ionospheric scintillations over Hyderabad

Investigation of the relationship between ionospheric scintillations and equatorial spread F (ESF) during adverse space weather conditions is of paramount significance for developing ionospheric scintillation mitigation strategies for Global Navigation Satellite System (GNSS) receivers. In this paper, we present correlation analysis between equatorial spread F (ESF) and L-band amplitude scintillations conducted at low-latitude Hyderabad station (17.47° N, 78.57° E) during the severe geomagnetic storm event of 17 March 2015 (St. Patrick's Day). Hyderabad location comes under the region between the magnetic equator and the northern crest of equatorial ionization anomaly (EIA). ESF information is derived from ionograms of ionosonde located at the Tata Institute of Fundamental Research (TIFR) Balloon Facility, Hyderabad, whereas amplitude scintillation index (S4) data have been obtained from the GPS receiver at Hyderabad (GAGAN network). Intense spread F (SSF) signatures were observed during post-sunset hours of 16 March (pre-storm day) and 17 March (storm day), 2015, where the spread F (SF) index is higher than 1 MHz. GPS satellite vehicle with pseudo-random noise code (PRN) 24 experienced strong scintillation (S4 = 1.06) at 18:53 UT on the pre-storm day of 16 March 2015. GPS PRN 30 satellite was affected severely on 17 March (storm day), when the observed S4 index is 0.99. Development of ESF and subsequent scintillations are due to the strong eastward prompt penetration electric fields over the Indian region. The inhibition of spread F and scintillations noticed on 18 March 2015 are because of disturbance dynamo electric fields and disturbance winds. The SSF occurrences were well correlated with scintillation index values at Hyderabad station, India. Variations of the virtual height of the F layer (h′F) and drift velocity (Vd) are related to the S4 values during the period of interest. The outcome of the preliminary results would be useful for development of ionospheric scintillation prediction algorithms for GPS users.

Sodium-ion-conducting solid polymer electrolyte: temperature-dependent ionic parameters and solid-state polymer battery fabrication

Temperature-dependent ionic parameters and solid-state polymer battery studies of a newly synthesized sodium-ion-conducting solid polymer electrolytes (SPEs): (1 − x) PEO: x NaCl, where 0 ≤ x ≤ 50 in wt%, are reported. The present SPEs are synthesized by a recently developed hot-press/dry technique in place of traditional solution-cast method. The room temperature conductivity (σ) of the optimum conducting composition (OCC), i.e., (70PEO:30NaCl) is ~ 4.5 × 10–6 Scm−1. The ion transport behavior has been explained with the help of some basic ionic parameters viz. ionic conductivity (σ), ionic mobility (μ), mobile ion concentration (n), ionic transference number (tion) and ionic drift velocity (vd) by using various experimental as well as theoretical models. The conductivity enhancement and polymer–salt complexations have been confirmed by X-ray diffraction, differential scanning calorimetric and thermogravimetric analysis. A new solid-state polymer battery is also fabricated by using the optimum conducting composition of solid polymer electrolyte (SPE OCC) as an electrolyte, and their cell parameters have been calculated at room temperature.

Effect of gas concentration on the electron transport and the plasma parameters of the CO2 gas mixture

Electron Swarm Parameters in plasma gas mixtures of Co2 have been calculated. Studies focused on four gas mixtures with Co2, He, and N2 in the ratio 5%: 55%: 40%, 2.5%: 45%: 52.5%, 10%: 50%: 40% and 40%: 40%: 20% respectively. Calculations of the electron energy distribution function f (ε), drift velocity Vd, mobility μ, electron diffusion D, D/μ, electron average energy <ε> and electric field E in the range of electric field to gas number density ratio E/N from 1×10−19 to 5×10−15 at 300 0K were reported in this work. The theoretical calculations shown helium has a good effect on the electrons transition parameters of Co2 laser. Furthermore, at low energy, the total collision rate is increasing slowly for higher electron energy.

Drift velocity saturation and large current density in intrinsic three-dimensional Dirac semimetal cadmium arsenide

Transport of electrons at high electric fields is investigated in intrinsic three-dimensional Dirac semimetal cadmium arsenide, considering the scattering of electrons from acoustic and optical phonons. Screening and hot phonon effect are taken in to account. Expressions for the hot electron mobility μ and power loss P are obtained as a function of electron temperature Te. The dependence of drift velocity vd on electric field E and electron density ne has been studied. Hot phonon effect is found to set in the saturation of vd at relatively low E and to significantly degrade its magnitude. The drift velocity is found to saturate at a value vds ∼ 107 cm s−1 and it is weakly dependent on ne. A large saturation current density ∼ 106 A cm−2 is predicted.

ELECTRICAL PROPERTIES OF CdxSe1-x FILMS AT DIFFERENT THICKNESS AND ANNEALING TEMPERATURES

CdxSe1-xalloy has been prepared successfully. The prepared alloy were used to produce CdxSe1-x films. CdxSe1-x films with different thickness (0.5, 1, 1.5, 2)μm have been prepared by thermal evaporation on glass substrates. The deposited films have been annealed at different temperatures (373, 423 and 473)K. From studying the electrical properties of CdxSe1-xfilms deposited on glass with different thickness and annealing temperature, we found that D.C conductivity increases from 1.511 × 10-5 to 67.6 × 10-5 (Ω.cm)-1 at R.T with thickness increasing (0.5–2)μm and decreases from 1.511 × 10-5 to 1.4×10-7 (Ω.cm)-1 with increasing of annealing temperatures (R.T–473)K for 0.5μm thick. There are two activation energies for D.C conductivity Ea1 and Ea2 decrease from 0.151 to 0.107 eV and from 0.446 to 0.188 eV at R.T, respectively, with increasing of thickness form 0.5 to 2μm. Ea1 and Ea2 increase from 0.151 to 0.231 eV and from 0.446 to 0.570 eV at 0.5 μm thick, respectively, with increasing of annealing temperatures (R.T–473)K. Hall measurements confirmed that all the intrinsic films are n-type, carriers concentration decreases from 11.16 × 1014 cm-3 to 8.333 × 1014 cm-3 at R.T with increasing of thickness (0.5–2)μm, and decrease form 1.116 × 1015 cm-3 to 0.096 × 1014 cm-3 for 0.5μm thick with increasing of annealing temperatures (R.T– 473)K. The mobility is found to increase with increasing of thickness and annealing temperatures. The drift velocity (Vd), carrier lifetime () and mean free path (ℓ) increase with increasing of annealing temperatures and thickness.A.C conductivity measurements for CdxSe1-xfilms with different thickness and annealing temperatures consistent with correlated barrier hopping model (CBH).

Toward an Integrated View of Ionospheric Plasma Instabilities: 3. Explicit Growth Rate and Oscillation Frequency for Arbitrary Altitude

AbstractGeneral analytic expressions are derived for the growth rate γ and oscillation frequency in the ion frame of unstable plasma waves generated by ionospheric plasma instabilities including the Farley‐Buneman instability (FBI) and the gradient‐drift instability (GDI). The explicit expressions are developed for arbitrary altitude and scales in the local approximation. Limits of applicability are carefully considered focusing on the dependence on the electron density gradients G=∇n/n and wavelengths λ. It is shown that the key parameter that controls the applicability is the growth rate γ normalized to the ion collision frequency νi, with the developed expressions being valid for slow growths γ/νi&lt;0.1. It is also shown that the commonly used assumption about the equivalency of the wave phase velocity Vph and the plasma drift velocity Vd fails in the F region at gradients as weak as G=10−5m−1. The developed analytic expressions for arbitrary altitude/scale offer a straightforward way of reconciling various altitude‐ and scale‐specific cases (e.g., FBI/GDI modes in the E region), with the often‐neglected ion inertia shown to play a critical role in the reconciliation. The new ion inertia effect is found to be represented by the quantity in the growth rate expression. The effect is found to reduce the standard FBI factor and amplify the GDI factor, and, due to the inverse relationship with the ion inertia, the effect becomes progressively stronger at larger altitudes and/or wavelengths.

Morphology and electrical properties of Cu X Zn1-XO thin films prepared by PLD technique

Cu X Zn1-XO films with different x content have been prepared bypulse laser deposition technique at room temperatures (RT) anddifferent annealing temperatures (373 and 473) K. The effect of xcontent of Cu (0, 0.2, 0.4, 0.6, 0.8) wt.% on morphology andelectrical properties of CuXZn1-XO thin films have been studied.AFM measurements showed that the average grain size values forCuXZn1-xO thin films at RT and different annealing temperatures(373, 473) K decreases, while the average Roughness values increasewith increasing x content. The D.C conductivity for all filmsincreases as the x content increase and decreases with increasing theannealing temperatures. Hall measurements showed that there aretwo types of conductance (n- type and p-type charge carriers). Alsothe variation of drift velocity (vd), carrier life time (), and free meanpath (l) with different x content and annealing temperatures weremeasured.

Ion conduction behavior of hot-pressed nanocomposite polymer electrolytes: (1 − x) [70PEO:30NaBr] + xSiO2

Ion conduction behavior of a new Na+ ion-conducting nanocomposite polymer electrolytes (NCPEs): (1 − x) [70PEO:30NaBr] + xSiO2, where 0 < x < 20 wt%, is reported. NCPEs have been synthesized using a hot-press technique. Materials characterization, polymer-salt/nanofiller SiO2 complexation and thermal properties characterization were done with the help of XRD, FTIR, SEM, DSC and TGA studies. The ion conduction behavior in the present NCPEs has been discussed by the experimental measurements on some basic ionic parameters viz. conductivity (σ), ionic mobility (μ), mobile ion concentration (n), ionic transference number (tion), ionic drift velocity (vd) etc.

Current conduction mechanism and electrical break-down in InN grown on GaN

Current conduction mechanism, including electron mobility, electron drift velocity (vd) and electrical break-down have been investigated in a 0.5 μm-thick (0001) InN layer grown by molecular-beam epitaxy on a GaN/sapphire template. Electron mobility (μ) of 1040 cm2/Vs and a free electron concentration (n) of 2.1 × 1018 cm−3 were measured at room temperature with only a limited change down to 20 K, suggesting scattering on dislocations and ionized impurities. Photoluminescence spectra and high-resolution X-ray diffraction correlated with the Hall experiment showing an emission peak at 0.69 eV, a full-width half-maximum of 30 meV, and a dislocation density Ndis ∼ 5.6 × 1010 cm−2. Current-voltage (I-V) characterization was done in a pulsed (10 ns-width) mode on InN resistors prepared by plasma processing and Ohmic contacts evaporation. Resistors with a different channel length ranging from 4 to 15.8 μm obeyed the Ohm law up to an electric field intensity Eknee ∼ 22 kV/cm, when vd ≥ 2.5 × 105 m/s. For higher E, I-V curves were nonlinear and evolved with time. Light emission with a photon energy &amp;gt; 0.7 eV has been observed already at modest Erad of ∼ 8.3 kV/cm and consequently, a trap-assisted interband tunneling was suggested to play a role. At Eknee ∼ 22 kV/cm, we assumed electron emission from traps, with a positive feed-back for the current enhancement. Catastrophic break-down appeared at E ∼ 25 kV/cm. Reduction of Ndis was suggested to fully exploit InN unique prospects for future high-frequency devices.

Amplification of terahertz frequency acoustic phonons by drifting electrons in three-dimensional Dirac semimetals

The amplification coefficient α of acoustic phonons is theoretically investigated in a three-dimensional Dirac semimetal (3DDS) driven by a dc electric field E causing the drift of the electrons. It is numerically studied as a function of the frequency ωq, drift velocity vd, electron concentration ne, and temperature T in the Dirac semimetal Cd3As2. We find that the amplification of acoustic phonons (α ∼ hundreds of cm-1) takes place when the electron drift velocity vd is greater than the sound velocity vs. The amplification is found to occur at small E (∼few V/cm) due to large electron mobility. The frequency dependence of α shows amplification in the THz regime with a maximum αm occurring at the same frequency ωqm for different vd. The αm is found to increase with increasing vd. α vs ωq for different ne also shows a maximum, with αm shifting to higher ωq for larger ne. Each maximum is followed by a vanishing α at nearly “2kf cutoff,” where kf is the Fermi wave vector. It is found that αm/ne and ωqm/ne1/3 are nearly constant. The αm ∼ ne can be used to identify the 3DDS phase as it differs from αm ∼ ne1/3 dependence in conventional bulk Cd3As2 semiconductor.

Cerenkov emission of acoustic phonons electrically generated from three-dimensional Dirac semimetals

Cerenkov acoustic phonon emission is theoretically investigated in a three-dimensional Dirac semimetal (3DDS) when it is driven by a dc electric field E. Numerical calculations are made for Cd3As2 in which mobility and electron concentration are large. We find that Cerenkov emission of acoustic phonons takes place when the electron drift velocity vd is greater than the sound velocity vs. This occurs at small E (∼few V/cm) due to large mobility. Frequency (ωq) and angular (θ) distribution of phonon emission spectrum P(ωq, θ) are studied for different electron drift velocities vd (i.e., different E) and electron concentrations ne. The frequency dependence of P(ωq, θ) shows a maximum Pm(ωq, θ) at about ωm ≈ 1 THz and is found to increase with the increasing vd and ne. The value of ωm shifts to higher region for larger ne. It is found that ωm/ne1/3 and Pm(ωq, θ)/ne2/3 are nearly constants. The latter is in contrast with the Pm(ωq, θ)ne1/2 = constant in conventional bulk semiconductor. Each maximum is followed by a vanishing spectrum at nearly “2kf cutoff,” where kf is the Fermi wave vector. Angular dependence of P(ωq, θ) and the intensity P(θ) of the phonon emission shows a maximum at an emission angle 45° and is found to increase with increasing vd. P(θ) is found to increase linearly with ne giving the ratio P(θ)/(nevd) nearly a constant. We suggest that it is possible to have the controlled Cerenkov emission and generation of acoustic phonons with the proper choice of E, θ, and ne. 3DDS with large ne and mobility can be a good source of acoustic phonon generation in ∼THz regime.

Development of a Laser Induced Fluorescence (LIF) system on thePlasma Material Interaction System (PLAMIS-II) device

A laser induced fluorescence (LIF) system has been developed for the plasma material interaction system (PLAMIS-II) device, which is equipped with a unique plasma gun composed of a LaB6 cathode and two anodes with electromagnets to generate a focused dense plasma. PLAMIS-II simulates the interactions of plasma with different materials and is to be used for the test of plasma facing components of fusion devices. The LIF system is composed of a seed laser with Littmann/Metcalf cavity and a master oscillator power amplifier to pump 3d4F7/2 metastable argon ion to 4p4D5/2 level at the wavelength of 668.61 nm, which has the following input parameters: laser power = 20 mW, line width < 100 kHz, and a mode-hop free tuning range > 70 GHz. For in-situ measurement of laser wavelength, the wavelength spectrum of an iodine cell was measured by a photo-transistor during LIF measurement. To measure argon ion temperature (Ti) and drift velocity (vd) in PLAMIS-II, the fluorescence light with the wavelength of 442.72 nm, emitted from 4p4D5/2 level to 4s4P3/2 level and passing through 1 nm band-width filter, was collected by the photomultiplier tube combined with a lock-in amplifier and a chopper with frequency of 3 kHz. Initial data of Ti and vd were analysed in terms of gas flow rate and applied power.

High field transport properties of a bilayer graphene

The high electric field transport properties namely, hot electron energy loss rate P, momentum loss rate Q, electron temperature Te and drift velocity Vd are studied theoretically in a bilayer graphene (BLG) by employing the momentum and energy balance technique. P and Q are investigated as a function of Te by considering the electron interaction with the acoustic phonons (APs) and the surface polar phonons (SPPs). In the Bloch–Grüneisen regime P (Q) due to APs is ~Te4 (Te2.5), with a new feature of a kink appearing due to the chiral nature of the electrons. The predicted Te4 is consistent with the recent experimental observation of heat resistance (Yan et al. Nature Nanotechnology 3 (2012) 472 [35]). Hot phonon effect is taken into account for SPPs. A dip has been observed in the hot phonon distribution of SPPs, a new feature, which is not found in conventional two-dimensional electron gas, and this can be attributed to the chiral nature of the electrons. P (Q) due to SPPs is found to be dominant at about Te>150 (180)K for a lattice temperature T=4.2K. It is observed that the hot phonon effect is found to reduce P and Q due to SPPs significantly. Te and Vd are calculated as a function of the electric field E by taking into account the additional channels for momentum relaxation due to Coulomb impurity (CI) and short-range disorder (SD). Te is found to increase with the increasing electric field and is significantly enhanced by the hot phonon effect. Low field Vd is found to be limited by CI, SD and APs and in the high field region it reaches a near saturation value. The hot phonon effect tends to reduce the value of Vd. The presence of disorders CI and SD reduces Vd significantly and in clean samples larger saturation velocity can be achieved at a relatively smaller E.

Kinetic Alfvén wave instability driven by field‐aligned currents in a low‐β plasma

Kinetic Alfvén waves (KAWs) can play an important role in the energization of plasma particles and the formation of filamentous structures, which commonly are encountered and frequently accompanied by field‐aligned currents in various magneto‐plasmas, such as laboratory, auroral, and coronal plasmas. Based on a low‐frequency kinetic dispersion equation in frequency ω&lt;ωci (the ion cyclotron frequency), KAW instability driven by a field‐aligned current, which is carried by the field‐aligned drift of electrons at velocity VD, is investigated in a low‐β plasma of β&lt;Q≪1, where β is the kinetic‐to‐magnetic pressure ratio and Q (≡me/mi≪1) is the mass ratio of electrons to ions. An instability condition and the corresponding growth rate are obtained, which depends on the plasma β parameter as well as the drift velocity VD. The results show that the KAW instability occurs in the perpendicular wave number range of , in which the growth rate reaches its maximum at for fixed VD and β. As VD increases, this growing wave number range widens and the growth rate increases, but the maximal‐growing wave number decreases. On the other hand, as the plasma βparameter decreases, the growing wave number range also widens, and the maximal‐growing wave number and growth rate both increase. These results have potential importance in understanding the physics of the electric current dissipation and plasma active phenomena since the field‐aligned current is one of the most active factors in space and astrophysical plasmas.