Pulsed Valve Research Articles

Experimental Study of Flow Structures of Circular Pulsating Air Jet

Problem Statement: Applications of impingement jets in industry for heating and cooling purposes requires a high convective heat transfer coefficient. Numerous studies have been conducted to improve the convective heat transfer coefficient for a steady impinging jet. A pulsating jet has a very high potential in replacing steady jet after it been found able to increase the heat transfer coefficients at certain pulsating frequencies. The objectives of this study were to; (i) determine the velocity profile of a circular pulsating air jet at different pulse frequencies and Reynolds Number using a rotating valve pulse jet system and (ii) to compare the normalized steady and pulsed jet velocity at highest Reynolds number of 32 000 and highest pulsating frequency of 80Hz. Approach: Pulsation of the air jet was produced by a rotating cylinder valve mechanism at frequencies between 10-80 Hz. Flow structures of the heated steady and pulse single circular axisymmetric air jet velocity were measured using a calibrated hot-wire anemometer and presented in non-dimensional form. The measurements were carried out at three different Reynolds numbers which was set at 16000, 23300 and 32000. The jet exit velocity profile for all the test frequency is determined by plotting the graph of radial distance against the non-dimensional jet exit velocity. Results: The corresponding Reynolds number in this test is based on time-averaged centerline velocity. The results of the velocity measurement were plotted side by side using non-dimensional parameters in order to make direct comparison of the velocity profile at different frequencies and Reynolds numbers. Stagnation point velocities are the same for steady and pulsating jet for all pulse frequencies. As the radial distance from the stagnation point increases, pulsating velocity increases between 20-30% from radial distance of 2-22 mm. Conclusion: Results of the flow structures plotted show a distinctive exit air jet profile which can affect the impingement heat transfer characteristics. This was the result of enhanced turbulence intensity due to pulsating jet produced by the rotating cylinder. From the jet exit velocity profile obtained, it is found that mass flow rate for different test frequencies are slightly different due to the difference in the local velocity measurement affected by the pulses. The jet exit velocity profile data will be used to form a correlation between the pulsating jet velocity and heat transfer data.

Transient analysis of reactions between NO and H2 with Pt-Al2O3 thin film catalyst

Transient pulse techniques using time-of-flight mass spectrometry were used to investigate the reduction of NO by H 2 over Pt/Al 2 O 3 thin film. A typical result measured at 400 °C shows different behaviors of N 2 , NH 3 and N 2 O. Changing the temperature with corresponding numerical simulations, we elucidated that N 2 O was produced via a consecutive process of NO reduction with NH 3 molecules. A specially designed apparatus employing (1) pulse valves for injection of reactant molecules onto catalysts and (2) a time-of-flight mass spectrometer was used to investigate processes of NO + H 2 reaction using Pt-Al 2 O 3 thin film on Si substrate. First, the planar layer of the catalyst was located in a vacuum chamber and the reactants were supplied onto the surface by pulse valves. This process is considered to involve few consecutive reactions. There, the transient production of N 2 and NH 3 was observed simultaneously. Second, the reactants were supplied into the micro reactor filled with square pieces of planar catalysts spaced with SiC balls. Here, N 2 O was observed as well as NH 3 and N 2 . The experiments and the numerical simulation of the NO and H 2 reaction rates clearly elucidated some aspects of NO reduction passes, i.e., while N 2 and NH 3 were directly produced from N and H adatoms dissociated from NO and H 2 admolecules, N 2 O was produced via consecutive process of NO reduction with NH 3 molecules which were produced in transient reactions.

Research on cluster-assistant multiple ionization of acetonitrile by intense nanosecond laser

To further investigate the relation between cluster and multi-charged ions, the photo-ionization of acetonitrile molecular beam carried by helium was studied by time-of-flight mass spectrometry using 25 ns, 532 nm and 1 064 nm Nd-YAG laser with an intensity of 10(10) W x cm(-2). When the effused beam of CH3CN at a pressure of about 11 kPa was irradiated by a 532 nm laser, only a few mono-charged ions appeared in the mass spectrum and were clearly resolved, While the pulsed molecular beam seeded in 0.15 MPa He, multi-charged species appeared between H+ and C+, and parent ions containing one or more acetonitrile molecules were also discovered. The intrinsical difference between effused beam and pulsed one was that for the latter it was easier to generate molecule clusters. Adjusting delay time between laser and pulsed valve to shine the laser on different potions of pulsed beam, the change tendency of integral intensity of different multi-charged ions was found to remain similar to that of acetonitrile cluster, and the highest intensity of different ion species appeared at the same 0.75 ms delay time. When the wavelength of laser was changed from 532 nm to 1064 nm, the type of ions and their proportion from effused beam were alike except intensity, but the result of pulsed beam altered obviously. Multi-charged ions showed peak splitting, which characters CE (Coulomb explode). As a powerful tool to understand some chemical physics processes involved, correlation analysis of the time of flight mass spectrum was used. The spectrum of 532 nm was selected owing to its multi-charged ions distinguished easily. The correlations among N(n+) (n = 2-5) and C(n+) (n = 2-4) were all above 0.25, with some even above 0.7, indicating that these ions are highly correlated and probably come from the CE events simultaneously. An electron re-scattering and re-colliding ionization model was proposed to explain the appearances of those multiple charged ions under such low laser intensity. From the theory, the longer wavelength facilitates the energy absorption rate during inverse bremsstrahlung, which leads to the resulting wavelength dependence of the multi-charged atomic ions.

집진기의 공기소모량과 백 필터내의 압력전파에 대한 실험적 연구

이 연구는 필터 백을 사용하는 집진기에서 펄스밸브에 부착된 솔레노이드 밸브의 통전 시간과 공기소모량 사이의 관계를 실험적으로 규명하였으며 이 때 필터 백에 작용하는 압력파의 전달과정을 고찰하였다. 펄스당 공기소 모량이 집진기 운전비용의 주요 요소이므로 펄스제트의 전파과정을 관찰하고 압력파형과 공기소모량을 측정하였다. 또 주어진 조건하에서 필터 백의 길이의 영향을 고찰하고 효율적인 탈진작용을 할 수 있는 통전시간과 충격량 사이의 관계를 규명하였다 주어진 실험조건 범위에서는 통전시간이 짧을수록 더 큰 충격량을 얻을 수 있으며 동일한 통전 시간에 대하여는 여러 번의 짧은 펄스를 발생시키는 것이 더 효율적인 것으로 나타났다. This experimental investigation is concerned with the relationship between the electrical-on time of a solenoid which is located on the top of a pulse valve and air consumption of a dust collector. For the air consumption per pulse would be one of major factors affecting the operating cost of a dust collector, more attention is needed on the behaviour of a pulse valve. A pulse jet is blasted into a bag filter as the diaphragm valve opens and inflates a bag filter. This air-blast breaks up the dust layer and cleans the filter by dislodging dust cake. It is interpreted in this research that the cleaning filter is done by the impulse of a pulse jet. Hence, the magnitude and fluctuation of the dynamic pressure is measured using by a dynamic pressure sensor and the impulse is obtained by integrating dynamic pressure variation against time. Through this experimental work, conclusions are drawn implementing magnitude of averaged impulsive pressure per pulse or pressure impulse per unit volume of consumed air.

Laser-rf creation and diagnostics of seeded atmospheric pressure air and nitrogen plasmas

A laser initiation and radio frequency (rf) sustainment technique has been developed and improved from our previous work to create and sustain large-volume, high-pressure air and nitrogen plasmas. This technique utilizes a laser-initiated, 15 mTorr partial pressure tetrakis (dimethylamino) ethylene seed plasma with a 75 Torr background gas pressure to achieve high-pressure air/nitrogen plasma breakdown and reduce the rf power requirement needed to sustain the plasma. Upon the laser plasma initiation, the chamber pressure is raised to 760 Torr in 0.5 s through a pulsed gas valve, and the end of the chamber is subsequently opened to the ambient air. The atmospheric-pressure plasma is then maintained with the 13.56 MHz rf power. Using this technique, large-volume (1000 cm3), high electron density (on the order of 1011–12 cm−3), 760 Torr air and nitrogen plasmas have been created while rf power reflection is minimized during the entire plasma pulse utilizing a dynamic matching method. This plasma can project far away from the antenna region (30 cm), and the rf power budget is 5 W/cm3. Temporal evolution of the plasma electron density and total electron-neutral collision frequency during the pulsed plasma is diagnosed using millimeter wave interferometry. Optical emission spectroscopy (OES) aided by SPECAIR, a special OES simulation program for air-constituent plasmas, is used to analyze the radiating species and thermodynamic characteristics of the plasma. Rotational and vibrational temperatures of 4400–4600±100 K are obtained from the emission spectra from the N2(2+) and N2+(1−) transitions by matching the experimental spectrum results with the SPECAIR simulation results. Based on the relation between the electron collision frequency and the neutral density, utilizing millimeter wave interferometry, the electron temperature of the 760 Torr nitrogen plasma is found to be 8700±100 K (0.75±0.1 eV). Therefore, the plasma deviates significantly from local thermal equilibrium.

A modification of the laser detonation-type hyperthermal oxygen atom beam source for a long-term operation

It has been an impedimental problem, for the laser detonation-type atom beam generator, that a poppet in the pulsed supersonic valve is rapidly eroded by the irradiation of powerful laser light and high temperature plasma. In order to operate the atom beam source for a long duration, a modification was made to hide the poppet from direct irradiation of laser and plasma. The alteration of device configuration resulted in great improvement in endurance of poppet more than 300,000 repetitions. Morphology of a polyimide film exposed to approximately 200,000 pulses of hyperthermal oxygen atom beam showed a shaglike carpet structure, which is a characteristic to that exposed to energetic oxygen atoms. A flux of the oxygen atom beam was estimated to be 5x10(14) atoms/cm2/pulse at a location of 30 cm away from the nozzle throat.

Pulsed-field-ionization zero-kinetic-energy photoelectron spectroscopy of metastable He2: Ionization potential and rovibrational structure of He2+

A supersonic beam of metastable He(*) atoms and He(2) (*) a (3)Sigma(u) (+) molecules has been generated using a pulsed discharge at the exit of a pulsed valve prior to the gas expansion into vacuum. Pulsed-field-ionization zero-kinetic-energy photoelectron spectra of the He(2) (+) X(+) (2)Sigma(u) (+) (v(+)=0-2)<--He(2) (*) a (3)Sigma(u) (+) (v(")=0-2) transitions and photoionization spectra of He(2) (*) in the vicinity of the lowest ionization thresholds have been recorded. The energy level structures of (4)He(2) (+) X(+) (2)Sigma(u) (+) (v(+)< or =2,N(+)< or =23) and (3)He(2) (+) X(+) (2)Sigma(u) (+) (v(+)=0,N(+)< or =11) have been determined, and an accurate set of molecular constants for all isotopomers of He(2) (+) has been derived in a global analysis of all spectroscopic data reported to date on the low vibrational levels of He(2) (+). The analysis of the photoionization spectrum by multichannel quantum defect theory has provided a set of parameters describing the threshold photoionization dynamics.

Coupling of ion‐molecule reactions with liquid chromatography on a quadrupole ion trap mass spectrometer

We report for the first time a coupling of gas-phase ion-molecule reactions with chromatographic separations on a quadrupole ion trap mass spectrometer. The interface was accomplished by using a pulsed valve for the introduction of a volatile neutral into the ion trap. The pulsed valve controller is synchronized with the mass spectrometer software. The setup requires some minor modifications to the vacuum system of the commercial quadrupole ion trap but most of the modifications are external to the mass spectrometer. Two applications of this interface are described: differentiation between two phosphoglucose positional isomers and detection of a phosphopeptide in a peptide mixture. Both applications are using the reactivity of trimethoxyborate towards a phosphate moiety in the negative ion mode. The detection of phosphopeptides hinges on our findings that non-phosphorylated peptide anions do not react with trimethoxyborate. This LC/MS detection can be easily visualized in terms of selected reaction monitoring.

超臨界流体ジェット分光法の開発と高次系分子分光への応用

We developed a supercritical fluid jet technique, which enables the vaporization and the jet-cooling of non-vola-tile molecules by supersonic expansion of their supercritical solutions to vacuum directly. For its purpose, a new high-pressure pulsed valve was developed. By using this pulsed valve, we could introduce the high-pressure fluid. over 25MPa into vacuum as a short gaseous pulse, and confirmed that we can obtain an enough jet-cooling condi-tion. In this review, we will introduce a detail of the high-pressure pulsed valve and its application for the super-critical fluid jet spectroscopy.

Selecting the size of helium nanodroplets using time-resolved probing of a pulsed helium droplet beam

We show that helium nanodroplets generated using a pulsed valve undergo velocity dispersion according to their size. This makes it possible to use temporal selection to probe nanodroplets of a particular size within the pulsed gas profile rather than changing the expansion conditions as is done when using continuous helium nanodroplet sources. The variation in mean droplet size achievable within a single gas pulse can extend over more than an order of magnitude.

The best of both worlds – A novel approach to macromolecular STM studies

The advent of scanning tunnelling microscopy (STM) and its younger sibling atomic force microscopy (AFM) have fundamentally changed the way we investigate phenomena on the molecular scale. Direct visualisation is routine and atomic and molecular level imaging is an expectation of most researchers, if not their supervisors. It might therefore be surprising to learn that whole classes of systems cannot be readily visualised using either technique. AFM is in principle the more versatile technique and ultrahigh vacuum (UHV) studies have demonstrated atomic resolution on surfaces [1] and more recently an ability to distinguish between different surface atoms [2]. However, without significant advances in force sensor technology [3] the prospect for routine molecular (not to mention sub-molecular) imaging is poor. STM, the elder sibling, is itself not without limitations. Apart from the obvious requirement of conducting substrates, it is also important to minimise resolution loss due to unwanted mixing between molecular and substrate electronic levels. In the quest to image large molecular and polymer systems using STM most researchers are faced with deciding between an ambient or UHV approach, including the oftentimes difficult task of developing appropriate sample handling and preparation procedures. Ambient STM studies typically employ gold or graphite substrates and for which samples are typically deposited directly from solution. This approach works well for a broad range of soluble molecular and polymer systems but imaging is often unstable and contamination and artefacts can be problematic [4]. The alternative UHV approach offers more stable tunnelling conditions, together with an atomically clean substrate lattice that provides an in-situ reference for structure analysis. The latter approach, however, is not amenable to systems with ultra-low vapour pressures or which decompose or denature at elevated preparation temperatures. On page XXX of this issue Laracuente and co-workers [5] describe an innovative approach to this problem that combines the best of UHV STM imaging with solution-based sample processing. Starting from a UHV prepared Si(100) surface, the authors formed a passivated H-termination by exposure to atomic hydrogen [6]. H-terminated Si(100) surfaces are stable, exceptionally well ordered and are routinely imaged with atomic resolution [7]. Transferring the H-terminated Si(100) substrate to a nitrogen-purged load-lock, samples were then drop-cast from solution onto the surface, and quickly transferred back to the STM for analysis. CDCl3 was found to be the most suitable solvent for their particular system (a pentiptycene-based polymer) and was chosen following a careful study of the contamination and oxidation levels on the H-terminated Si(100) surface after treatment with different solvents [5]. The beauty of this approach is that it overcomes the vexing problem of sample deposition by eliminating the need for Knudsen cells or even more sophisticated pulsed valve delivery systems, while at the same time provides the full benefits of

Photochemical and Discharge-Driven Pathways to Aromatic Products from 1,3-Butadiene

A detailed study of the photochemical and discharge-driven pathways taken by gas-phase 1,3-butadiene has been carried out. Photolysis or discharge excitation was initiated inside a short reaction tube attached to the outlet of a pulsed valve. Bath gas temperatures near 100 K were achieved in the reaction tube by the constrained expansion of the gas mixture into the tube, simulating temperatures of relevance in Titan's atmosphere. Photolysis of 1,3-butadiene was initiated at 218 nm with a laser pulse that counter-propagated the reaction tube. Discharge excitation was carried out using discharge electrodes imbedded in the reaction tube walls, enabling the study of the photochemical and discharge products under similar conditions. Products were detected using either single-photon VUV photoionization (118 nm = 10.5 eV) or resonant two-photon ionization (R(2)PI) spectroscopy in a time-of-flight mass spectrometer. Emphasis was placed on characterization of the aromatic products formed, since these may be of particular relevance to Titan's atmosphere, where benzene has been positively identified and 1,3-butadiene is projected as the principle pathway to its formation. Consistent with previous studies of the photodissociation of 1,3-butadiene, C(3)H(3) + CH(3) is the dominant primary product formed. Under the temperature-pressure conditions present in the reaction tube (T approximately 75-100 K, P = 50 mbar), C(6)H(6) is the dominant secondary photochemical product formed. A 1:1 C(4)H(6):C(4)D(6) mixture was used to prove that the C(6)H(6) product was formed by recombination of two C(3)H(3) radicals; however, a careful search for benzene revealed none, indicating that less than 1% of the C(6)H(6) formed in the reaction tube is benzene. This is consistent with expectations for these temperatures and pressures based on previous modeling of propargyl recombination. Two aromatic products were observed from the photochemistry: ethylbenzene and 3-phenylpropyne. Plausible pathways leading to these products are proposed. In the discharge, C(3)H(3) + CH(3) are also identified as significant primary neutral products and C(6)H(6) as a dominant higher-mass product. In this case, the C(6)H(6) was identified as benzene via its R2PI spectrum, appearing with intensity about 10 times larger than any other aromatic formed in the discharge. R2PI spectra of a total of about 15 aromatic products were recorded from the 1,3-butadiene discharge, among them toluene; styrene; phenylacetylene; o-, m-, and p-xylene; ethylbenzene; indane; indene; beta-methylstyrene; and naphthalene. Previously unidentified spectra in the m/z 142 and 144 mass channels were positively identified as the 1,3- and 1,4-isomers of phenylcyclopentadiene and the analogous 1-phenylcyclopentene.

Design and characterization of a temporal analysis of products reactor

We describe an improved temporal analysis of products (TAP) reactor design whose main new features in comparison to the recent TAP-2 design of Gleaves et al. [Appl. Catal. A 160, 55 (1997)] are the use of a turbomolecular pump, piezoelectrically driven pulse valves, and a newly designed, differentially pumped gate valve. The gate valve allows fast and simple changes between high pressure operation, in which in situ catalyst treatment can be performed, and the analytic mode with a direct line-of-sight connection to the analysis chamber and the mass spectrometer. The heating system and pulse valves are located outside the vacuum chamber, resulting in a system that is easy to operate and modify. The high stability and reproducibility of the pulse intensity allows for direct, quantitative evaluation of single-pulse and multipulse experiments. The performance of the system is demonstrated using the CO oxidation over a Au/TiO(2) catalyst as test reaction.

An Effective Method of Producing Small Neutral Carbon Clusters

An effective method of producing small neutral carbon clusters Cn(n = 1–6) is described. The small carbon clusters (positive ornegative charge or neutral) are formed by plasma which are produced bya high power 532 nm pulse laser ablating the surface of the metal Mn rodto react with small hydrocarbons supplied by a pulse valve, then theneutral carbon clusters are extracted and photo-ionized by anotherlaser (266 nm or 355 nm) in the ionization region of a lineartime-of-flight mass spectrometer. The distributions of the initialneutral carbon clusters are analysed with the ionic species appeared inmass spectra. It is observed that the yield of small carbon clusterswith the present method is about 10 times than that of the traditionalwidely used technology of laser vaporization of graphite.

Laser spectroscopy and dynamics of the jet-cooled AsH2 free radical

The A (2)A(1)-X (2)B(1) electronic transition of the jet-cooled AsH(2) free radical has been studied by laser-induced fluorescence (LIF), wavelength-resolved emission, and fluorescence lifetime measurements. The radical was produced by a pulsed electric discharge through a mixture of arsine (AsH(3)) and high pressure argon at the exit of a pulsed valve. Nine vibronic bands were identified by LIF spectroscopy in the 505-400 nm region, including a long progression in the bending mode and two bands (1(0) (1) and 1(0) (1)2(0) (1)) involving the excited state As-H symmetric stretch. Single vibronic level emission spectra showed similar activity in the bending and symmetric stretching frequencies of the ground state. High-resolution spectra of the 0(0) (0) band exhibited large spin splittings and small, resolved arsenic hyperfine splittings, due to a substantial Fermi contact interaction in the excited state. The rotational constants obtained in the analysis gave effective molecular structures of r"(0)=1.5183(1) A, theta"(0)=90.75(1) degrees and r'(0)=1.4830(1) A, theta'(0)=123.10(2) degrees . The excited state fluorescence lifetimes vary dramatically with rovibronic state, from a single value of 1.4 micros to many with lifetimes less than 10 ns, behavior which the authors interpret as signaling the onset of a predissociative process near the zero-point level of the ground state.

Time Resolved Measurement of Intermediate Chemical Products in Homogeneous Charge Compression Ignition Using an Improved Pulse Sampling Method

A diagnostic method has been developed to detect transient intermediate species in reciprocal engine cycles and applied to homogeneous charge compression ignition (HCCI) processes. In-cylinder gas is sampled into a vacuum chamber through an electrically actuated pulse valve mounted on an engine head and analyzed by a quadrupole mass spectrometer. Based on the observation that the quenched volume near the cylinder wall is sampled within 1 ms from the valve open, a correction scheme extracting the reactive core component is employed. The crank-angle resolved measurement of HCCI with dimethyl ether as a fuel demonstrated that intermediate species such as aldehyde and hydrogen peroxide appear at the first stage cool ignition and disappear at the last stage hot ignition. This result is a validation to the detailed chemistry model predictions for the two-stage ignition.

Role of rotational temperature in adiabatic molecular alignment

One-dimensional alignment of molecules in the adiabatic limit, where the pulse duration greatly exceeds the molecular rotational periods, is studied experimentally. Four different asymmetric top molecules (iodobenzene, p-diiodobenzene, 3,4-dibromothiophene, and 4,4'-dibromobiphenyl), rotationally cooled through a high pressure supersonic pulsed valve, are aligned by a 9-ns-long pulse. Their orientations are measured through Coulomb explosion, induced by a 130-fs-long pulse, and by recording the direction of the recoiling ions. The paper focuses on the crucial role of the initial rotational temperature for the degree of alignment. In particular, we show that at molecular temperatures in the 1 K range very strong alignment is obtained already at intensities of a few times 10(11) W/cm2 for all four molecules. At the highest intensities (approximately 10(12) W/cm2) the molecules can tolerate without ionizing <cos2 theta> >or=0.92 in the case of iodobenzene. This is the strongest degree of alignment ever reported for any molecule.

On the performance of copper foaming metal in the heat exchangers of pulse tube refrigerator

As key components in pulse tube refrigerators (PTRs), heat exchangers have great influence on the performance of the PTRs, especially the cold end heat exchangers which dominate the cooling effect between the cold gas and heat load. Filling copper screens are widely used to improve the performance of heat exchange and laminar flow. Whereas, the heat transfer rate of copper screens is still not good enough for the actual requirements of PTRs. Furthermore, the flow resistance of the copper screen is growing up quickly with the increase of screen mesh. In this paper, we propose a new type of copper foaming metal with high heat transfer area and low flow resistance in the heat exchanger instead of the copper screens. The heat transfer performances of the copper screens and the copper foaming metal are firstly compared by theoretical calculation, which shows that the performance of the copper foaming metal with 600 μm pore size is better than that of 20 and 80 mesh copper screens, verified by experimental results. A four valve pulse tube refrigerator (FVPTR) with copper foaming metal of 600 μm pore size as filling material of the heat exchanger achieved 69.5 K, 2.5 K lower than that of using 20 mesh copper screens, 1.7 K lower than that of using 80 mesh copper screens.

Characteristics and diagnostics of an ultrahigh vacuum compatible laser ablation source for crossed molecular beam experiments

We present the design and the characteristics of an ultrahigh vacuum compatible laser ablation source which can be operated in a crossed molecular beam machine at pressures as low as 10−9Torr. This unit provides intense supersonic beams of up to 3×1013cm−3 reactant species (carbon atoms, dicarbon, and tricarbon) in the interaction region of a crossed molecular beam machine. Practical delay time windows between the pulsed valve releasing the seeding gas and the laser have been determined to be between 16 630 and 16645μs, i.e., firing the laser 150–165μs after the 80μs pulsed valve trigger. The concentration of the dicarbon and tricarbon clusters can be maximized/minimized by adjusting the laser focus (a tighter laser focus leads to an enhanced atomic carbon component) and the laser power (multiphoton dissociation). We achieved stable peak velocities between 800 and 3800ms−1 and speed ratios S of up to 6.

SiC-DACFET

The nm-range abrupt doping profiles in SiC epitaxial layers are stable even after the high temperature process because SiC crystal exhibits little diffusion of impurities. Growth of the SiC delta-doped layers have been reported by our group and the others. We believe that the well-designed delta-doped epitaxial layers for the FET channels extend possibility of the power SiC FET. We proposed the SiC Delta-doped Accumulation Channel MOSFET (DACFET) consisting of the delta-doped layers for MOS channel and reported its high MOS-channel mobility. The vertical hot-wall-type CVD system was used to grow SiC epitaxial layers. The pulse valve, which supplied short (<ms) gas pulse flow, was directly connected to the CVD reactor to introduce the doping gases N 2. The pulse-doping technique enabled formation of the delta-doped-layer structure during SiC epitaxial growth. The n-type delta-doped layer as thin as 2 nm was fabricated with a peak N concentration of 1 × 10 19 cm −3. The electrical characteristics of the DACFET, for example threshold voltage and R on, can be tuned by controlling the delta-doped-layer structures in MOS channel. MOS-channel mobility of the normally-off lateral DACFET was measured to be >100 cm 2/V s. The vertical DACFET, whose blocking voltage was >600 V, was fabricated with the double-implantation MOS process. R on of the normally-off 2 μm-gate DACFET was measured to be 13 mΩ cm 2. Current density was observed to be >140 A cm −2 larger than Si-IGBT. Shortening of gate length and unit cell size of the SiC-DACFET using high-resolution lithography will result in R on <7 mΩ cm 2.