Switch Tube Research Articles

A Study on Thyratron Ranging and Diagnosis

Thyratrons have been used as switching tubes in power conditioning systems, primarily for radar and accelerator applications. Their function are to control power pulses to high-frequency oscillators in high-power radar sets, lasers, and other communications equipment. However, it is difficult to diagnose the switching characteristics of the thyratron. From a convection heat transfer, we have discovered the diagnostic factor of the thyratron, where the variation of the heater current occurs according to the variation of the internal gas pressure. By this diagnostic factor, thyratron ranging and diagnosis are possible. We have verified the theoretical propriety of the diagnostic factor and confirmed that the assumption used in the theory is applicable to the thyratron.

Noise currents and noise voltages in ac supply lines due to fluorescent lamp switching

Previous publications have not investigated the mechanism of fluorescent lamp noises, although there have been some observations. This paper reports our observations of the waveforms of noise on a power line when a fluorescent lamp with a glow switch was on and examines the major noise mechanisms. The current and voltage waveforms in fluorescent lamp components when the lamp was switched on and the luminescent waveforms of the glow switch and fluorescent tube were observed in detail to determine the mechanisms of the major noise current and voltage generation. An equivalent circuit in a measurement system was prepared to investigate the noise current and voltage theoretically. An experimental equation to determine the noise current waveform from the properties of the lamp and power line was derived so that the waveform could be easily determined. © 1998 Scripta Technica. Electron Comm Jpn Pt 1, 81(3): 36–46, 1998

Output control of the line type pulse modulator by a duration of "on" state of an additional switch tube

A technique is presented that enables rapid control of the output peak voltage of the line-type pulse modulator by changing the pulsewidth of the gate voltage applied to an additional switch tube in parallel with the thyratron. The current and voltage characteristics of the pulse modulator with an additional switch tube are analyzed to establish design rules. It is shown by a numerical example that output pulse voltages of a modulator with 5 kV DC source can be changed from 5 kV to 15 kV during 1 ms by changing the gate pulsewidth from 0 to 0.693 ms. This technique can be applied to the amplitude modulation or the rapid regulation of output pulses of radars and similar equipment.

Survey of high-voltage pulse technology suitable for large-scale plasma source ion implantation processes

Many new plasma processes ideas are finding their way from the research lab to the manufacturing plant floor. These require high voltage (HV) pulse power equipment, which must be optimized for application, system efficiency, and reliability. Although no single HV pulse technology is suitable for all plasma processes, various classes of high voltage pulsers may offer a greater versatility and economy to the manufacturer. Technology developed for existing radar and particle accelerator modulator power systems can be utilized to develop a modern large scale plasma source ion implantation (PSII) system. The HV pulse networks can be broadly defined by two classes of systems, those that generate the voltage directly, and those that use some type of pulse forming network and step-up transformer. This article will examine these HV pulse technologies and discuss their applicability to the specific PSII process. Typical systems that will be reviewed will include high power solid state, hard tube systems such as crossed-field ‘‘hollow beam’’ switch tubes and planar tetrodes, and ‘‘soft’’ tube systems with crossatrons and thyratrons. Results will be tabulated and suggestions provided for a particular PSII process.

Plasma ion implantation technology for broad industrial application

The recently invented Plasma Ion Implantation (PII) process (1987) [J. R. Conrad, U.S. Patent No. 764394 (August 16, 1988)] is currently under intense industrial engineering investigation and development. A critical component of PII for broad industrial utilization is the availability of an efficient modulator system that applies the high voltage pulse to the workpiece. A modulator technology assessment and selection is carried out. The requirements of the PII process favor the selection of a hard-tube modulator. The PII process favors the application of beam switch tube technology such as the Litton L-5012 and L-5097. These Litton tubes have already been selected by LANL and utilized in their pilot engineering demonstration experiment with GM and the University of Wisconsin. The performance, physical operation, and potential enhancements of the Litton beam switch tubes L-5012 and L-5097 will be discussed in connection with the requirements of the emerging plasma ion implantation industrial modulator technology.

Switching characteristics of the triggered vacuum gap for a high-repetition-rate pulse-power source

Switching characteristics of sealed-off triggered vacuum gaps (TVGs) were examined from the viewpoint of a high repetition rate at high current discharge. With a triggered energy of 11 J, it was possible to fire the main gap in both the anode and cathode modes of operation. In repetitive discharge experiments, the TVG-tube was put in the center of the cylindrical conductor and the switching tube inductance was about 27 nH. The TVG-tube was confirmed to have capabilities for 1000 shots with a pulse current of 120 kA and a high repetition rate of 5 Hz. These experimental results indicated that the TVG-tube is a potential repetitive closing switch for the plasma X-ray source. >

Arc-discharge mode and interruption performance in vacuum switch tubes

Arc phenomena in vacuum switch tubes involving the transition mechanism of the arc-discharge mode, and the relations among the arc-discharge mode, the electrode material, the electrode configuration, and the interruption performance are investigated. It is suggested that the positive ion accumulation near the anode causes the anode-spot mode transition. The floating shield potential and the arc voltage are related to the interrupting ability for the arcs between unslotted flat electrodes and between spiral electrodes, respectively. Through these fundamental research activities, a new line of compact vacuum switch tubes and new types of vacuum circuit breakers carrying them have been developed. >

Glow discharge cleaning of vacuum switch tubes

To clean the surfaces of parts inside a vacuum-switch tube (VST) the authors propose a technique which generates a glow discharge between the inner electrodes and the copper grid surrounding it. Photographic observation reveals that the glow discharge spreads out and cleans the whole surface inside the VST. A breakdown test between the inner electrodes shows the effect of the cleaning with this technique. Higher breakdown voltage between the inner electrodes is attained by performing this glow discharge cleaning in argon rather than hydrogen gas. The difference of the cleaning effect seems to be attributed to that of the energy transfer from ion species to the adsorbed molecules and microprotrusions on the surfaces.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Method and equipment for vacuum monitoring in vacuum switching tubes

Method and equipment for vacuum monitoring in vacuum switching tubes

High-power RF-pulsed modulators for the Los Alamos free electron laser

In the rf-driven free electron laser (FEL) at the Los Alamos National Laboratory, there are two pulsed-power rf modulators as sources for two tandem, side-coupled 20 MeV linear accelerators. The rf power used to control the cavity fields is supplied by two 5.5 MW modulating anode klystrons operating at a center frequency of 1300.2 MHz. The modulation of the 125 kV klystron is achieved by using a triode switch tube that provides a pulse width up to 300 μs and a pulse repetition rate up to 10 Hz. This paper describes the present configuration of these two duplicate systems and presents plans for meeting the requirements of future rf FEL experiments at Los Alamos.

Thomson parabola ion energy analyzer with a coincident and jitter-free applied electric field ramp

A simple Thomson parabola ion energy analyzer for intense pulsed ion beam is demonstrated. Beam ions collimated by two apertures, are deflected by a time ramping electric field and a static magnetic field. The ramping electric field is produced with a stacked cable pulser powered by a voltage divider of the pulse power generator. As there is no additional switching tube and no high-voltage generator other than the main machine, the analyzer has an electric field ramp that is coincident and has no jitter with the ion beam. A temporal history of ion beam energy is measured as an example and a reasonable agreement with the measured diode voltage is obtained.

A high-temperature prototype instrument for downhole acoustic sensing

This paper presents the design for an acoustic instrument which can operate at frequencies of 10–40 kHz and temperatures up to 250°C. It first introduces a high-temperature circuit using Sandia's Sprytron switching tube and an over-voltage gap. Next, the high-temperature performance of a 2-V Permendur magnetostrictive transducer (for the transmitter), and a piezoelectric material (for the receiver) is described. The problems encountered and the corresponding solutions are revealed. The design of an acoustic isolator and the mechanical housing of this instrument are presented.

The Fermilab Injection Kicker

This paper describes the proton injection kicker system designed to accept protons from the Fermilab Conventional Main Ring in the Tevatron Superconducting Ring. The pulse forming network (PFN) based thyratron switch tube pulser delivers a 100 ns rise, 200 ns fall, 40 KV pulse to a 6.25 ohm traveling wave magnet load. The pulse duration is adjustable up to a maximum of ~ 22 μsec. The design philosophy, magnet parameters, and system performance are discussed.

Gridded Cross Field Tube

A triode crossed field tube has been operated as a high voltage on-off switch tube. A third, partially transparent (grid) electrode is interposed between the anode and cathode and electrically tied to the cathode by a grid leak resistor. High voltage is first applied to the anode and cathode; the magnetic field is then raised to the conduction level (~ 0.01 Tesla). Ignition does not occur because the magnetic field is too low in the grid-anode gap and the electric field is zero in the cathode-grid gap. Pulsing the grid positive relative to the cathode (~ 1 kV) then results in breakdown of the cathode-grid gap; plasma comunication between the two gaps then fully ignites the tube and closes the main power circuit. Grid ignition has been achieved at 50 kV as well as grid ignition followed by current interruption against 10 kV. These levels were limited by the use of a modified, laboratory tube and not by the physics of the technique.

The Gamitron - A High Power Crossed-Field Switch Tube for HVDC Interruption

A high power crossed-field discharge device has been developed for use as a high voltage direct current interrupter. This device operates at low pressure (0.05 Torr), conducting current at a fixed voltage (~500 V) only in the presence of a weak magnetic field (~100 G) which is substantially perpendicular to the electric field between the electrodes. When the magnetic field is removed, ionization ceases and current interruption results. Physical phenomena occurring in this device have been investigated, including the glow-to-arc transition, gas cleanup, and high voltage breakdown. Based on the results of these investigations, switch tubes have been developed and successfully tested at the 2 kA, 100 kV level, with recovery rates in excess of 2 kV/?s. The availability of such devices will make possible many applications including HVDC circuit breakers, ac current limiters, and practical inductive energy storage.

A low-impedance high-vacuum switch tube

A low-impedance high-vacuum switch tube

Technology for high-speed ground transport: W. W. Seifert and R. J. Hansen. Massachusetts Inst. of Tech., Cambridge

The report summarizes the research accomplished at the Massachusetts Institute of Technology during the period September 16, 1965 through September 15, 1966. The efforts were on networks and terminals, scheduling, vehicle flow control and switching problems, vehicle-suspension problems, propulsion problems, vehicle and tube aerodynamics, and guideway problems.

Low Distortion RF Amplifier Video Pulses

Modern high energy particle accelerators require that the high power r.f. amplifiers generate r.f. waveforms which are essentially distortion free. This usually is accomplished through the use of very expensive and complicated high power regulation equipment. This paper will discuss an alternate, relatively simple means of obtaining this regulation through the use of a unique high vacuum switch tube used directly in series with the r.f. amplifier.

Experimental Studies of the Omnitron Electrical Components

A prototype resonator has been built and is under study. It tunes from 6.8 to 33 MHz and is designed to produce an accelerating gap voltage of 60 kV at 20 Mc. Sixty 30-in. -diam by 1/2-in.-thick ferrite discs are used. The resonator is excited by a final amplifier using an RCA 4616 tube designed to deliver a peak RF power of 300 kW. The paper also discusses studies of the RF drive train and the master oscillator, which tunes continuously from 1.5 to 33 MHz. It is a beat-frequency oscillator using a crystal-controlled fixed oscillator and a varactor-tuned variable oscillator. A ferrite magnet system, also under study, contains a coaxial, lumped-constant pulse line with a hydrogen thyratron switch tube coupled to a ferrite magnet. The pulse line uses ceramic capacitors and operates at one atmosphere of SF6. The rise time is 100 ns, the pulse width 5 Lsec, and the repetition rate 60 pps. Peak instantaneous power during the pulse is 200 MW; average power is 65 kW.

A decoder-driver system for magnetic-core memories using a 64-position switch tube

This paper describes the design, construction, and operation of a driver-decoder subsystem using a novel 64-position switch tube. The system is designed as part of a 10 Mc/s magnetic-core memory. The switch tube is a type of cathode-ray tube (CRT) using as a target, a 64-position matrix of silicon diodes. A split-plate electrostatic deflection system is used to select one diode out of the matrix, and turn it on with the electron beam. The effect of the beam is to produce a 1.5 ampere, 150 volt, 3 ns rise time pulse. The delay through the system is 25 ns.