US3105027A - Gas discharge apparatus - Google Patents

Gas discharge apparatus Download PDF

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Publication number
US3105027A
US3105027A US766124A US76612458A US3105027A US 3105027 A US3105027 A US 3105027A US 766124 A US766124 A US 766124A US 76612458 A US76612458 A US 76612458A US 3105027 A US3105027 A US 3105027A
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Prior art keywords
discharge
circuit
current
voltage
winding
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Expired - Lifetime
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US766124A
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English (en)
Inventor
Carruthers Robert
Thonemann Peter Clive
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UK Atomic Energy Authority
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UK Atomic Energy Authority
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14—Circuit arrangements
    • H05B41/30—Circuit arrangements in which the lamp is fed by pulses, e.g. flash lamp
    • H05B41/32—Circuit arrangements in which the lamp is fed by pulses, e.g. flash lamp for single flash operation
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H1/00—Generating plasma; Handling plasma
    • H05H1/02—Arrangements for confining plasma by electric or magnetic fields; Arrangements for heating plasma
    • H05H1/04—Arrangements for confining plasma by electric or magnetic fields; Arrangements for heating plasma using magnetic fields substantially generated by the discharge in the plasma
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H1/00—Generating plasma; Handling plasma
    • H05H1/02—Arrangements for confining plasma by electric or magnetic fields; Arrangements for heating plasma
    • H05H1/20—Ohmic heating

Definitions

  • This invention relates to gas discharge apparatus and I38 one application in apparatus of the type in which a ugh-current ring discharge is induced in a gas contained n a torus, the discharge forming the single-turn secndary winding of a pulse transformer.
  • Apparatus of his kind, for use in research into the production of conrollcd thermonuclear reactions is described in the specilcation of co-pending application No. 692,500, filed )ctober 25, 1957, now Patent 3,054,742.
  • the electrical circuit of the apparatus described in the pecification of the aforementioned application consists ssentially of a capacitor which is charged from an exernal source and then discharged through the primary vinding of the transformer.
  • an ignitron connected cross the winding is fired and both the primary and the lischarge currents die away exponentially from their eak values.
  • the object of firing the ignitron at this ime is to prevent the voltage on the capacitor reversing.
  • thermonuclear fusion reactions will take lace between ions of the gas in the torus as a result f these ions being heated by the collisions they make rith electrons in the ring discharge.
  • a finite true is required for the ions and electrons to come into iermal equilibrium and, under some conditions, the type f circuit described above may not maintain the disharge current at a suificiently high value for a sufficiently mg time for this equilibrium to be achieved.
  • a gas discharge apparatus wherein a high-current ring discharge is induced 1 gas in a vessel by the application of a short higholtage pulse from a first energising circuit to a primary 'inding of a pulse transformer whereof said ring disharge forms a single-turn secondary winding is charcterised in that there is provided a second energising ircuit adapted to produce a relatively low voltage outut of relatively long duration and means for coupling aid second energising circuit to said secondary winding 1 order to maintain the discharge current at a high alue for a prolonged period when the high voltage pulse as fallen to zero.
  • Said first energising circuit may comprise a capacitor 1d switch means for discharging said capacitor through re primary winding of said pulse transformer.
  • Said second energising circuit may comprise a changed :lay line and may be adapted to store energy at high )ltage, a second pulse transformer being provided for educing said high voltage to the required low voltage.
  • the present invention takes advantage of the fact that ice the discharge is established its impedance is largely :sistive and of very low value, so that a relatively small voltage provides a primary current sufiicient to maintain the discharge current at a high value.
  • FIG. I is a semi-schematic circuit diagram of one embodiment of the invention as applied to an experimental gas discharge apparatus of the type described in the specification of the above-mentioned copending application.
  • FIG. 2 shows waveforms in the circuit of FIG. 1.
  • a gas discharge apparatus of the kind set forth is shown as comprising a metal torus 1 containing gas (deuterium or a deuterium/tritium mixture) in which a pinched ring discharge is induced by a transformer T1.
  • the torus 1 is provided with. a toroidal winding L11 through which a current is fed from a source 2 to establish an axial magnetic field for reducing spatial instabilities of the discharge, as explained in the aforementioned specification.
  • the transformer T1 is provided with a bias winding L10 fed from a source 4 through a choke L12, as is also described in the aforementioned specification.
  • transformer T1 The primary winding of transformer T1 is divided into five separate sub-windings L8, L9, L13, L14 and L15 fed in parallel from five identical cncrgising circuits. Only one of these five circuits is shown in detail, viz. the circuit connected to winding L8. The other four circuits are shown schematically as blocks 11, 12, 13 and 14 connected respectively to windings L9, L13, L14 and L15.
  • the circuit shown in detail comprises a capacitor C6 of l820 f., 24 kv. working, which is chargeable through a resistor R6 of 250 ohms and a Jennings high vacuum switch S8 from a source 3.
  • Source 3 comprises a sixphase transformer and rectifier, the input to the transformer being servo-controlled by an induction regulator so that the source delivers a constant charging circuit of 1a. until capacitor C6 is fully charged to 24kv., and thereafter a trickle charge to maintain the voltage.
  • Across C6 is connected a Jennings switch S10 in series with a resistor R8 of 250 ohms as a safety shorting switch.
  • Capacitor C6 is discharged through winding L8 by firing a series ignitron 11 (BTH type BKl94).
  • a second ignitron l2 (BTH type BK194) is connected between the cathode of 11 and the earth point of the circult, and a capacitor C7 of 2 d.
  • a mechanical switch S7 are connected between the anode of II and the earthy side of the circuit.
  • the switch S7 is of the high-speed compressed-air operated type, with an operating time of about 57 milliseconds and contacts capable of carrying about ka.
  • a protective series resistor R7 of 0.08m is included in the discharge circuit to protect C6 by damping any oscillations resulting from the accidental breakdown of l2.
  • Return connections from the five primary windings on T1 are taken to the earthy sides of the five circuits through the five secondary windings L6, L16, L17, L18 and L19 of a pulse transformer T2, having like T1 a bias winding L7 energised from a source 5 through a resistor Rlt) in order to achieve the maximum flux swing.
  • the primary winding L5 of T2 is connected through a mechanical switch S6, similar to S7, to a delay line comprising four inductors l-1L4 and five capacitors C1-C5 each of 1820 f, 24 RV. working. Across these capacitors are connected safety shorting switches 51-55 of the Jennings type, in series with resistors Rl-RS of 250 ohms.
  • the leakage inductance of the primary winding L constitutes a fifth inductor in the delay line.
  • the delay line capacitors C1C5 are charged from a source 18, similar to source 3, through a Jennings switch S9 and a resistor R9 or" 250 ohms. Ignitrons I3 and I4 are connected across C1 and C5 respectively.
  • the circuit connected to the primary winding of T2 constitutes a second energising circuit.
  • Transformer T2 has tappings providing step down ratios of 6/12/24/36/48/72/96/144/192:1.
  • Inductors L1L4 have tappings enabling their inductances to be varied between 5 and 320 rnh.
  • the five primary windings on T1 are distributed windings wound on the surface of the torus and can be connected in three series-parallel arrangements to give step-down ratios of 6/ 12/ 24:1.
  • FIG. 2 The operation of the circuit of FIG. 1 is shown in FIG. 2, which displays waveforms of the voltage V across the five primary windings and the current I in these windings.
  • FIG. 2 is not drawn to scale. Assuming the capacitors C6 in each of the five circuits and also the capacitors C1-C5 in the delay line circuit to be charged, all switches to be open and all ignitrons unfired, the switch S6 is closed at a time :1 and the transformer T2 is energised. Because of the step-down ratio of T2, a relatively small voltage is thus made available across the secondary winding L6 which is not however applied to the primary windings since I1, 12 and S7 are open-circuit.
  • the discharge cycle is actually started, at time t6, by initiating the closure of S7, the closure of S6 being initiate-d shortly after at time 17.
  • the closure of these switches is controlled by a timing unit 6 which is controlled in turn by a master timer 7 which operates the charging switches S8 and S9.
  • An electromechanical interlock ensures that 56 has closed and that $7 is closing before 11 is fired.
  • I2 is fired by a control circuit 8 which is tripped from a potentiometer R11 connected across C6.
  • 14 is fired by a similar control circuit 9 tripped from a potentiometer R12 connected across the delay line adjacent to switch S6.
  • ignitron I3 is connected across the far end and h fired by a control circuit 10 tripped from a potentiometer R13 connected across the line.
  • the repetition period of the discharges is variable between 50 and seconds. Since this is a relatively long period, it is preferred to keep the reactor conditioned between discharges by a series of smaller discharges at a higher repetition frequency, and for this reason the transformer T1 is provided with a further primary winding L20 connected to a lower energy energising circuit 12 substantially the same as that described in the aforementioned specification.
  • the repetition period of circuit 12 is controlled by the timer 7 to be about 10 seconds, as in the reactor described in said specification.
  • the maintaining voltage developed across the secondary windings L6, L16, L17, L18 and L19 can be varied by adjusting the tappings on transformer T2 and/ or the voltage to which capacitors C1-C5 are charged by source 18.
  • the values of the inductors L1L4 can be adjusted by means of tappings thereon. In this way the impedance of the line can be varied between 1.8 and 14.35 ohms. This of course also varies the delay line discharge time, i.e. the time between 12 and t5, between a minimum of 30 milliseconds and a maximum of 230 milliseconds.
  • capacitors C1-C5 each of which consists of a plurality of smaller capacitors connected in parallel.
  • discharge impedances in the range 7.7x 10 to 117x101 ohms can be matched by adjusting inductors Ll-L4, taking into account the range of step-down ratios on T2.
  • the pulse rise time, i.e. 12-13 is about 1.8 milliseconds; the 12:1 and 24:1 ratios give rise times of 3.6 and 7.2 milliseconds respectively.
  • Capacitor C7 is included in the circuit so that if one of the five ignitrons I1 fires slightly before the others, the voltage across the remaining four will not fall immediately and prevent them firing. Capacitor C7, together with the inductance of the lead between it and the transformer primary winding L8, impose a short delay on a pulse arriving at the anode of I1 from one of the other four circuits, and so give it time to fire.
  • coaxial cables are used for connections carrying the current pulses.
  • the above described embodiment is only one arrangement according to the invention, and that there are other ways in which the invention can be carried out.
  • the reason for using five primary windings is that the current-carrying capacity of ignitrons is at present limited. With a discharge current of 10 a., the total primary current with a 6:1 turns ratio is ka., which is much more than a single ignitron could handle. By using five primary windings, and five ignitrons, the current in each is reduced to about 35 ka.
  • circuits according to the invention are that the two functions of (a) building-up the discharge current and (b) maintaining it while reactions take place, are separated.
  • the first function requires a short timeconstant circuit and a high electric field to build up rapidly the magnetic energy associated with the discharge channel; this current is determined largely by the circuit inductance and relatively little energy is dissipated.
  • the energy to be supplied is determined by the losses from the discharge (radiation, conduction to the torus walls, etc); the current is resistive and only requires a small electric field which must, however, be maintained for a relatively long time.
  • switch means includes both mechanical switches and discharge devices such as ignitrons.
  • said second energising circuit comprises a delay line adapted to store energy at a high voltage and a step-down pulse transformer for coupling said delay line to said primary winding and hence to said secondary winding.

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Generation Of Surge Voltage And Current (AREA)
  • Plasma Technology (AREA)
US766124A 1957-10-11 1958-10-08 Gas discharge apparatus Expired - Lifetime US3105027A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB31855/57A GB854246A (en) 1957-10-11 1957-10-11 Improvements in or relating to gas discharge apparatus

Publications (1)

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US3105027A true US3105027A (en) 1963-09-24

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US766124A Expired - Lifetime US3105027A (en) 1957-10-11 1958-10-08 Gas discharge apparatus

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US (1) US3105027A (hu)
BE (1) BE571937A (hu)
DE (1) DE1079233B (hu)
FR (1) FR1211151A (hu)
GB (1) GB854246A (hu)
NL (2) NL109864C (hu)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3290219A (en) * 1963-09-19 1966-12-06 Gen Electric Plasma containment method and apparatus
US4494043A (en) * 1981-07-02 1985-01-15 Physics International Company Imploding plasma device

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2780750A (en) * 1951-01-26 1957-02-05 Westinghouse Electric Corp Heat control for frequency converter control
US3016342A (en) * 1957-08-29 1962-01-09 Kruskal Martin Controlled nuclear fusion reactor

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2780750A (en) * 1951-01-26 1957-02-05 Westinghouse Electric Corp Heat control for frequency converter control
US3016342A (en) * 1957-08-29 1962-01-09 Kruskal Martin Controlled nuclear fusion reactor

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3290219A (en) * 1963-09-19 1966-12-06 Gen Electric Plasma containment method and apparatus
US4494043A (en) * 1981-07-02 1985-01-15 Physics International Company Imploding plasma device

Also Published As

Publication number Publication date
DE1079233B (de) 1960-04-07
NL109864C (hu)
GB854246A (en) 1960-11-16
BE571937A (hu)
FR1211151A (fr) 1960-03-14
NL232098A (hu)

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