Filament Cathode Research Articles

Online Packaging Method of Filament Cathode for Intelligent Manufacturing

It is challenging to automatically package spiral shaped filament cathodes that are widely used in worldwide microwave ovens. The difficulties include a fast packaging speed of over one parts per second and the dexterity required to handle tangling and embedding between spiral filaments’ multiple circles. In order to convert conventional labor intensive packaging lines of filament cathodes into automatic ones, an online fast automatic packaging method is reported. The method converts the fast incoming sequential flow of filament spirals into a batch of twenty-parallel queues with two stopping levers. The proposed method using two levers to release only the front twenty filaments at a time, one from each queue to fill one complete row of the plastic packaging tray. In this way, it speeds up packaging speed twenty times over conventional sequential packaging method. The inner diameter of the queue tube matches the outer diameter of the filament. It is this dimeter matching to eliminate the embedding problem occurred between neighboring filaments. The proposed method uses vibrating brush to decouple tangled filaments. Large number of validating experiments indicate that the proposed method could automatically package 200 filaments spirals within 2 minutes, with positional accuracy of over 97%. Thus, the proposed packaging method could meet the manufacturing requirement of filament cathodes, releasing four labors out of every production line at every work-shift. Further, this method also simultaneously improves the surface quality of the filaments by eliminating scratch caused by their sharp fresh-cutting cross sections.

Positive ion impediment across magnetic field in a partially magnetized plasma column

The radial characteristic of a partially magnetized plasma column created by a hot cathode filament is presented. It is found that in the absence of a magnetic field, plasma potential and density profiles follow the Boltzmann distribution. However when a magnetic field is introduced, a clear divergence from Boltzmannian is seen as the plasma density becomes more pronounced in the centre whereas a corresponding minima is observed in plasma potential. This radial potential profile impedes the radial diffusion of positive ions towards the grounded sidewalls. A phenomenological model based on short-circuiting effect is developed, which fairly explains this contrasting behaviour.

Measurement of photoionization cross-section of Li (2p, 3d) excited states using thermionic diode detector

Studies on photoionization cross-section measurement of lithium 2p and 3d excited states selectively populated by single and two photons are reported. The photoionization is carried out in a heat-pipe cum thermionic diode detector using nitrogen laser pumped pulsed dye laser. Rhodamine perchlorate (Rh-640) dye is used to generate the desired tunable laser output in the range of 635 to 675 nm. Both, the thermionic diode detector and dye laser are developed in-house. A negative space charge region formed around diode cathode filament is illuminated by dye laser exciting pulse followed by ionizing UV radiation from nitrogen laser. The effect of ionizing laser pulse energy and precise tuning of dye laser on photoionization signal, across 670.780 nm (2S1/2 → 2P1/2,3/2) single-photon transition and 639.145 nm (2S1/2 → 2D3/2,5/2) two-photon transition are studied. The results obtained are compared with model calculations of photoionization signal saturation curve. The ionization cross-section for both the states (2P1/2, 2D5/2) are determined as 15.40 ± 2.8 Mb and 8.04 ± 1.6 Mb, respectively and atomic number density N ∼ 5.6 × 108 (cm−3).

Solid Electrolyte, Flexible Li-ion Fiber Batteries for Compliant Energy Storage and Wearable Applications

In my talk, I would present advances in fabrication of the solid electrolyte-based flexible li-ion fiber batteries, as well as their numerous potential applications in compliant energy storage and wearable devices. In particular, I would detail fabrication of the fiber-shaped lithium ion batteries assembled by twisting a cathode filament together with an anode filament. The cathode filament is fabricated by depositing a LiFePO4 (LFP)-composite layer onto a steel-filled polyester conductive thread (SPCT). As anode filaments, we propose several scenarios including a Li4Ti5O12 (LTO)-composite coated SPCT (dip-and-dry deposition), a tin-coated SPCT (PVD deposition) as well as a bare tin wire. An electrolyte composite layer consisting of LiPF6 and polyethylene oxide is then deposited onto both the anode and cathode filament before the battery assembly. To characterize the electrochemical and mechanical properties of the proposed batteries, we performed charge-discharge tests with different C-rates, electrical impedance tests and mechanical bending tests. The fabrication of the proposed LIBs is simple and cost-effective, as compared to the fiber-shaped LIBs using carbon nanotube fibers. Moreover, the reported LIBs are well suitable for the wearable applications as they feature all-solid electrodes and electrolyte, unlike the majority of other currently existing LIBs that utilize liquid organic solution-based electrolytes that may cause leakage and cause safety concerns. Among other advantages of the proposed LIB are light weight, ease of fabrication, high specific capacitance, high energy density, and good durability.

All-Solid Flexible Fiber-Shaped Lithium Ion Batteries

We propose fabrication of the fiber-shaped lithium ion batteries assembled by twisting a cathode filament together with an anode filament. The cathode filament is fabricated by depositing a LiFePO4 (LFP)-composite layer onto a steel-filled polyester conductive thread (SPCT). As anode filaments, we propose several scenarios including a Li4Ti5O12 (LTO)-composite coated SPCT (dip-and-dry deposition), a tin-coated SPCT (PVD deposition) as well as a bare tin wire. An electrolyte composite layer consisting of LiPF6 and polyethylene oxide is then deposited onto both the anode and cathode filament before the battery assembly. To characterize the electrochemical and mechanical properties of the proposed batteries, we performed charge-discharge tests with different C-rates, electrical impedance tests and mechanical bending tests. The fabrication of the proposed LIBs is simple and cost-effective, as compared to the fiber-shaped LIBs using carbon nanotube fibers. Moreover, the reported LIBs are well suitable for the wearable applications as they feature all-solid electrodes and electrolyte, unlike the majority of other currently existing LIBs that utilize liquid organic solution-based electrolytes that may cause leakage and cause safety concerns. Among other advantages of the proposed LIB are light weight, ease of fabrication, high specific capacitance, high energy density, and good durability.

Analysis and Design of Filament Power Supply with Voltage-Fed Single-Switch ZVS Inverter

In this paper, an off-line voltage-fed single-switch zero-voltage-switching (ZVS) inverter is analyzed and designed for the filament power supply of cooker magnetrons. Due to the low resistance of cathode filament, an isolation transformer with large turn ratio is used. To obtain the ZVS operation, a parallel-resonant capacitor is connected to the primary of transformer. The capacitor, transformer and filament constitute a parallel resonant tank. Both the transformer leakage inductance and the transistor output capacitance are merged into the resonant tank. The resonant energy provides the ZVS operation of the inverter switch, and the secondary voltage drives the cathode filament. To verify the analysis, a prototype inverter is built and tested. Experimental results validate the circuit design.

Helical-Cathode Bulb-Shaped Field Emission Lamps Using Carbon Nanocoil Electron Emitters.

Bulb-shaped field emission lamps (FELs) with a helical cathode filament were simulated and fabricated in this research. The light bulbs comprised a helical stainless steel filament cathode grown with carbon nano-coils (CNCs) and an Al anode deposited on the bottom hemisphere of a 60-mm-diameter glass bulb. White light was generated when the field-emitted electrons bombarded a layer of three-color phosphor coated on the anode. A numerical simulation model for the helical-cathode FELs was constructed, and the field emission (FE) performance was carefully studied. Due to the screening effect, the electric field strength as well as the FE current density on the inner side of the helix dramatically decreased with decreasing helical pitch. Real FELs using cathodes with various helical radii and pitches were fabricated and their FE currents were measured. The theoretical and experimental results were in good agreement. A maximum total FE current was found at a pitch of 16 mm (helical radius = 2 mm), where the optimum trade-off between a large total surface area and a small screening effect was obtained. The optimized FEL showed a total luminous flux of about 220 lm at an applied voltage of 8 kV and a color rendering index of 94. Compared to a straight filament cathode, a helical cathode offered a higher total FE current or, alternatively, a lower current density and a longer cathode life, if we fix the total current by using a lower voltage.

Pressure gauge filament for neutral gas density measurement using alternating current as source power

In plasma fusion research the in-vessel neutral gas density is often measured using hot cathode ionisation gauges which are modified for the application in high magnetic fields and for a measurement range between 10−3Pa and 20Pa. To obtain sufficient electron emission, the cathode (filament) is heated to high temperatures in the range of 1800K by direct ohmic heating. To compensate for the induced Lorentz-forces, the filament must be relatively thick to provide sufficient mechanical stability which implicates increases of heating currents up to 20A.The heating current could be reduced by using a thinner filament in combination with alternating current with suitably chosen frequency to reduce mechanical stresses. The benefit of such a technique is besides saving of heating power, especially space-saving by applying thinner power supply cables. To estimate the suitability of such a solution a feasibility study by means of numerical methods has been carried out. The main subject of the investigation was the hot-filament for which alternating current has been used as power source. This paper provides first of all the main guidelines and features important in developing a pressure gauge filament heated by alternating current from the mechanical point of view.

Radiofrequency and 2.45 GHz electron cyclotron resonance H− volume production ion sources

The volume production of negative hydrogen ions () in plasma ion sources is based on dissociative electron attachment (DEA) to rovibrationally excited hydrogen molecules (H2), which is a two-step process requiring both, hot electrons for ionization, and vibrational excitation of the H2 and cold electrons for the formation through DEA. Traditionally ion sources relying on the volume production have been tandem-type arc discharge sources equipped with biased filament cathodes sustaining the plasma by thermionic electron emission and with a magnetic filter separating the main discharge from the formation volume. The main motivation to develop ion sources based on radiofrequency (RF) or electron cyclotron resonance (ECR) plasma discharges is to eliminate the apparent limitation of the cathode lifetime. In this paper we summarize the principles of volume production dictating the ion source design and highlight the differences between the arc discharge and RF/ECR ion sources from both, physics and technology point-of-view. Furthermore, we introduce the state-of-the-art RF and ECR volume production ion sources and review the challenges and future prospects of these yet developing technologies.

Beam deflection induced by E×B near a linear filament cathode

Beam deflection induced by E×B near a linear filament cathode in a two grid electron gun is presented theoretically and experimentally. The experimental results are consistent with the calculation based on the theoretical equations. The influences upon performance and design of electron gun with linear filament cathode, which is used broadly in electrocurtain accelerators, are discussed in detail.

Device for timing and power level setting for microwave applications

Nowadays, the microwaves are widely used for various technological processes. The microwaves are emitted by magnetrons, which have strict requirements concerning power supplies for anode and filament cathodes, intensity of magnetic field, cooling and electromagnetic shielding. The magnetrons do not tolerate any alteration of their required voltages, currents and magnetic fields, which means that their output microwave power is fixed, so the only way to alter the power level is to use time-division, by turning the magnetron on and off by repetitive time patterns. In order to attain accurate and reproducible results, as well as correct and safe operation of the microwave device, all these requirements must be fulfilled. Safe, correct and reproducible operation of the microwave appliance can be achieved by means of a specially built electronic device, which ensures accurate and reproducible exposure times, interlocking of the commands and automatic switch off when abnormal operating conditions occur. This driving device, designed and realized during the completion of Mr.Ursu's doctoral thesis, consists of a quartz time-base, several programmable frequency and duration dividers, LED displays, sensors and interlocking gates. The active and passive electronic components are placed on custom-made PCB's, designed and made by means of computer-aided applications and machines. The driving commands of the electronic device are delivered to the magnetron power supplies by means of optic zero-passing relays. The inputs of the electronic driving device can sense the status of the microwave appliance. The user is able to enter the total exposure time, the division factor that sets the output power level and, as a novelty, the clock frequency of the time divider.

Generation of low-temperature plasma by low-pressure arcs for synthesis of nitride coatings

Experiments were performed to study gas, metal, and mixed metal-gas plasmas. The plasmas were generated with the use of an arc evaporator and a gas-plasma source with a hot filament and hollow cathode that were operated independently or simultaneously. It has been revealed that the arc current of gas-plasma source affects the parameters of the metal-gas plasma and the element concentrations in the coatings. It has been demonstrated that the characteristics of the nitride coatings produced by plasma-assisted vacuum-arc deposition can be controlled by varying the parameters of the arc in the gas-plasma source.

Effect of magnetic field on dust charging and corresponding probe measurement

The effect of external magnetic field on the Langmuir probe measurement and dust charging are studied in low-pressure hydrogen plasma. The experiment is performed in a dusty plasma device where plasma is created by the hot cathode filament discharge technique. A strong Strontium ferrite magnet is used inside the plasma, near the dust zone. The plasma parameters are measured at different distances from the magnet with the help of Langmuir probe system. It is observed that even at “low magnetic field case,” where rLe≥rP, rLi〉〉rP; the electron collection by the probe deviates strongly from the actual value, until rLe≥10rP. The observations of electron energy probability function show that at higher magnetic field, the Langmuir probe collects only the higher energy electrons compared to the low energy electrons. Both Quasi-neutrality condition and capacitance model are used separately to calculate the charge accumulated on the dust grain. Introducing the reduction factor on quasi-neutrality condition, it is observed that the influence of magnetic field on dust charge is almost negligible for “low magnetic field” case. The dust charge calculated from quasi-neutrality condition matches well with the experimentally observed dust current results, within the experimental error range. However, capacitance model deviates from the experimental results at higher magnetic field.

Field Emission Lamps Prepared with Dip-Coated and Nickel Electroless Plated Carbon Nanotube Cathodes.

Fabrication and efficiency enhancement of tubal field emission lamps (FELs) using multi-walled carbon nanotubes (MWNTs) as the cathode field emitters were studied. The cathode filaments were prepared by eletrolessly plating a nickel (Ni) film on the cathode made of a 304 stainless steel wire dip-coated with MWNTs. The 304 wire was dip-coated with MWNTs and nano-sized Pd catalyst in a solution, and then eletrolessly plated with Ni to form an MWNT-embedded composite film. The MWNTs embedded in Ni not only had better adhesion but also exhibited a higher FE threshold voltage, which is beneficial to our FEL system and can increase the luminous efficiency of the anode phosphor. Our results show that the FE cathode prepared by dipping three times in a solution containing 400 ppm Pd nano-catalysts and 0.2 wt.% MWNTs and then eletrolessly plating a Ni film at a deposition temperature of 60 °C, pH value of 5, and deposition time of 7 min has the best FE uniformity and efficiency. Its emission current can stay as low as 2.5 mA at a high applied voltage of 7 kV, which conforms to the high-voltage-and-low-current requirement of the P22 phosphor and can therefore maximize the luminous efficiency of our FEL. We found that the MWNT cathodes prepared by this approach are suitable for making high-efficiency FELs.

유한요소법을 이용한 X-선관 양극각도에 의존하는 전자빔 초점 특성 연구

The focal spot of electron beam depending on the anode angle in the structure and major parts of the X-ray tube was investigated by the OPERA-3D/SCALAR simulation program. The simulation worked on four spaces with with two spaces, including anode and cathode of X-ray tube, by applying the finite element method analysis. The analytical model and dimension for the emission orbit of thermal electrons made from one filament of the focused X-ray cathode is affected to the penumbra of detector for the X-ray depending on any real focal spot size. The model shape of focusing cap and focusing tube with an anode target angle and a cathode filament is analyzed by the current density distribution of thermal electrons. The focusing width of thermal electrons for the X-ray tube depended on the anode angle (θ). The focusing value of electron beams at a region of anode angle having 10 ~17 maintained to below value of 70 μm. The minimum focal size of the electron beam was 40 μm at an anode angle of 15 . The focused X-ray tube of many variables depended on the thermionic emission of hot electrons from the target trajectory. The focusing tube will contribute to

Improvement of Lighting Uniformity and Phosphor Life in Field Emission Lamps Using Carbon Nanocoils

The lighting performances and phosphor degradation in field emission lamps (FELs) with two different kinds of cathode materials—multiwalled carbon nanotubes (MWCNTs) and carbon nanocoils (CNCs)—were compared. The MWCNTs and CNCs were selectively synthesized on 304 stainless steel wire substrates dip‐coated with nanosized Pd catalysts by controlling the growth temperature in thermal chemical vapor deposition, and the film uniformity can be optimized by adjusting the growth time. FELs were successfully fabricated by assembling these cathode filaments with a glass bulb‐type anode. The FEL with the CNC cathode showed much higher lighting uniformity and light‐spot density and a lower current at the same voltage than that with the MWCNT cathode filament, and its best luminous efficiency was as high as 75 lm/W at 8 kV. We also found that, for P22, the phosphor degradation can be effectively suppressed by replacing MWCNTs with CNCs in the cathode, due to the much larger total bright spot area and hence much lower current density loading on the anode.

Investigation of parameters and uninterrupted service of a generator of gas-discharge plasma based on a nonsustained hot-cathode arc discharge in gas

The design of an electrode system and the characteristics of a gas-discharge plasma source (generator) based on an arc discharge in gas sustained by thermionic emission are presented. The results of an experimental investigation of the service life of a thermionic (hot) cathode of the plasma generator are reported as a function of the discharge current and voltage and the cathode filament power. It is shown that an increase in the burning voltage from 28 to 60 V considerably reduces the service life of the hot cathode, while the discharge current and the cathode filament power exert a less critical effect on its lifetime. The conditions necessary for achieving long-term service life parameters and high efficiency of plasma generation are found out.

Investigation of Hot Cathode and Hollow Anode of Argon Glow Discharge Plasma

Hot cathode and hollow anode argon DC glow discharge plasma at different pressures of (0.04, 0.05, 0.06, 0.07, 0.09, 0.2, 0.4, and 0.8 mbar) has been investigated. The experiments were carried out under the influence of pressure and filament cathode current on voltage – current characteristics of glow discharge and its breakdown voltage. Plasma parameters have been measured and obtained using single probe method at fixed discharge current (Id=1.88 mA) and hollow anode diameter. A computer MATLAB program is performed for this purpose. It was shown that the discharge voltage – current characteristics curve has a positive resistance and represents an abnormal glow region at pressure (0.04 and 0.06) mbar for different filament current. The breakdown voltage increases as the filament current is increased. In different pressure, electron temperature shows different behavior with increasing filament current. Electron density varies nearly inversely with the filament current, but it is increase due to increase of pressure from (1 to 3 mbar), then tends to decrease for the higher pressure. There are two groups of electrons according to the two peaks of (EEDFs), and the peaks amplitude decrease, with the increases of both filament current and gas pressure.

Hot Cathode’s Working Voltage Impacts on the Operation of High Current Ion Source

High power ion source is one of the important parts of the neutral beam injection. It produces high energy beam by extracting and accelerating ions from its arc chamber. The hot cathode (filaments) in the arc chamber of the ion source operates in two modes. Operation mode of the cathode has great effect on the stable operation of the ion source. Based on the theory of hot cathode and experimental results, this paper presents the operation results (beam current, arc efficiency) of an ion source with various cathode temperatures (controlled by voltage applied to the cathode).

Development of Cathode Filament Power Supply for EBW Based on ARM

The electron beam welding has high energy density, and has been widely applied in air space, the car and shipping industry. Traditional electron beam welding machine power supply system adopts the technology of the power frequency or medium frequency, with high volume, low efficiency and poor stability of electron beam. I put forward a digital filament power control scheme based on STM32, and introduce the hardware and software implementation method in detail. Experiments show that it can realize soft-start and soft-down process, and also be quickly identified and promptly forbid the output when filament fracture, which realize the intellectualization of filament power supply.