DE1079233B - Circuit arrangement for generating high current ring discharges in a gas-filled reaction chamber - Google Patents

Description

The invention relates to circuit arrangements for a gas-filled reaction chamber, in which by transmitting a brief high voltage pulse from a first excitation control circuit A heavy current ring discharge via a primary winding of a pulse transformer which forms the secondary winding of the pulse transformer. Such heavy current ring discharges are used in systems for studying the conditions for bringing about thermonuclear processes.

In the case of a system described elsewhere, the electrical control circuit consists mainly of from a capacitor, which is charged from an external power source and then via the Primary winding of a transformer is discharged. When the voltage in the capacitor reverse starts, an ignitron, which is connected to the winding, is ignited, so that both the primary is the discharge currents also drop exponentially. It is difficult to get involved with such a steering committee achieve thermal equilibrium in the plasma.

The purpose of the invention is therefore to provide a device through which it is possible to have a maintain high quality ring discharge current for a longer period of time.

This is achieved according to the invention in that a second excitation control circuit for generation a low voltage pulse of relatively long duration and switching means for the coupling of the mentioned second excitation circuit to the secondary winding are provided to the ring discharge current hold high for a longer period of time when the high voltage pulse has already dropped to a low value.

The aforementioned first and second excitation control circuits can be connected in series to the same primary winding of the first pulse transformer to which the aforementioned low voltage pulse is connected of a relatively long period of time is applied before the start of the short high voltage pulse. It switching devices can be provided for short-circuiting the first excitation control circuit, when the high voltage pulse from this excitation control circuit has dropped to a low value is.

The aforementioned first excitation control circuit may consist of a capacitor and a second switching device exist for discharging the capacitor through the primary winding of the aforementioned pulse transformer. The aforementioned second excitation control circuit may consist of a charging delay line and be set up so that it can store a high-voltage energy, while a second Im-Sctialtungsanordnung for generation

of heavy current ring discharges

in one filled with gas

Reaction chamber

Applicant:

United Kingdom Atomic Energy Authority, London

Representative: Dipl.-Ing. E. Schubert, patent attorney,
Siegen (Westphalia), Oranienstr. 14th

^X 5 Claimed priority:

Great Britain October 11th and December 6th 1957

Robert Carruthers, Abingdon, Berkshire,
and Peter Clive Thonemann, Cumnor Hill, Oxford

(Great Britain),
have been named as inventors

a _{5 2}

Pulse transformer intended for reducing the high voltage mentioned to the required low voltage is.

The invention advantageously makes use of the fact that when the discharge occurs once is constructed, its impedance is resilient to a large extent and of very small value, so that a primary current is generated by a relatively low voltage, which is sufficient to the To keep the ring discharge current at a high value.

The invention will now be explained in more detail with reference to the drawing showing it for example will.

Fig. 1 shows a circuit arrangement according to the invention in a semi-schematic representation, and

FIG. 2 shows the waveforms occurring in the circuit arrangement according to FIG.

Reference is first made to FIG. 1, in which the reference number 1 denotes a reaction chamber which consists of a metal torus which contains gas (deuterium or a deuterium-tritium mixture). A constricted ring discharge is induced in the gas space by a transformer T 1. The torus 1 is equipped with a winding LIl which is connected to a power source 2; this arrangement serves to build up an axial magnetic field which reduces the spatial instabilities of the ring discharge. The transformer Tl has a bias

909 769/452

winding L 10, which is fed from a power source 4 via a choke coil L 12, as has already been described elsewhere.

The primary winding of the transformer T1 is divided into five separate sub-windings LB, L 9, L 13, L14 and L 15, which are connected to five identical excitation control circuits. Only one of these five control circuits is shown in more detail, namely that control circuit which is connected to the winding L 8. The other four control circuits are illustrated schematically as blocks 11, 12., 13 and 14 which are connected to windings L 9, L 13, L14 and L 15, respectively.

The control circuit shown in more detail consists of a capacitor C 6 of 1820 μ ¥ (operating load 24 kV), which can be charged from a power source 3 via a resistor i? 6 of 250 ohms and a Jenning high vacuum switch S 8. The current source 3 consists of a six-phase transformer and a rectifier, the input of the transformer being controlled by an induction regulator so that the current source delivers a constant charging current of IA until the capacitor C 6 is fully charged to 24 kV. A smaller current is then used to maintain this voltage. Parallel to C 6 is a Jenning switch SlO in series with a resistor R8 of 250 ohms as a safety short-circuit switch. The capacitor C 6 is discharged through the winding L 8 by igniting a series-connected ignitrone / 1. A second Ignitron / 2 is connected between the cathode of Jl and the earth point of the control circuit, while a capacitor C 7 of 2 μΉ and a mechanical switching mechanism S7 are connected between the anode of / 1 and the earth side of the control circuit. The switchgear S7 is a switchgear of the high-speed, compressed air-operated type with a response time of around 57 milliseconds and has contacts that can be loaded with around 35 kA. A series-connected protective resistor R 7 of 0.08 ohms is built into this discharge circuit in order to protect C 6 by damping all vibrations that may occur as a result of an unforeseen interruption of / 2.

Return lines or return connections from the five primary windings of Tl are via the five secondary windings L 6, L 16, L17, L 18 and L 19 of a pulse transformer T 2, which, like Tl, has a bias winding L 7 , which to achieve a maximum flow of one Current source 5 is excited her via a resistor R 10, placed on the earth sides of the five control circuits. The primary winding L 5 of T 2 is connected to a delay line via a mechanical switching mechanism S 6 (similar to S 7). This consists of four inductors Ll to L 4 and five capacitors Cl to C 5, each of which has a value of 1820 μ ¥ and an operating load of 24 kV. To these capacitors safety short-circuit switches are Sl connected in series with resistors Rl through R5 of 250 ohms to 6 "5 Jenningschen type. The Lockaustrittsinduktivität the primary, winding Ls forms a fifth inductor in the delay line. The delay line capacitors C 1 to C 5 are from a power source 11, which is similar to the power source 3, charged via a Jenning switchgear 5 "9 and a resistor .R 9 of 250 ohms. The Ignitrone 13 and / 4 are connected to C1 and C5, respectively. The control circuit, which is connected to the primary winding of T 2, forms a second excitation control circuit.

The transformer TI has taps for voltage divider ratios of 6/12/24/36/48/72/96/144/192: 1. The inductors Ll to L 4 have taps which allow their inductances to be changed between 5 and 320 mH. The five primary windings of Tl are distributed on the surface of the torus. You can

ίο connected in three series-parallel circuit arrangements to give voltage divider ratios of 6/12/24: 1.

The operation of the control circuit shown in Fig. 1 is illustrated in Fig. 2, which shows waveforms of the voltage V across the five primary windings and the current I in these windings. Fig. 2 is not drawn to scale. If it is assumed that the capacitors C 6 in each of the five control circuits and also the capacitors C 1 to C 5 in the delay line circuit are charged, that all switching mechanisms are open and all Ignitrons are not fired, the switching mechanism S6 is closed at a time ti and the Transformer T 2 energized. Because of the voltage division ratio of T 2 a \ ^r erhältnismäßig low voltage on the secondary winding L 6 is thus available, which is not transmitted to the primary windings, since II, 12 is not ignited and S are open. 7 At a point in time 1 2, approximately 2 milliseconds after ti, / 1 is fired so that the full voltage of C 6 plus the voltage of L 6 is applied to L 8, L 9, and so on. The current in these windings and the ring discharge current in the torus rise rapidly, the voltage at C 6 begins to drop, and the delay line begins to discharge.

Most of the energy initially stored in C 6 is used to build up the discharge in the torus and is stored in the discharge's magnetic field. Once the ring discharge is established, its reflected impedance becomes resilient to a large extent and has a very low value, so that a low voltage across the primary windings is sufficient to generate a primary current sufficient to hold the ring discharge current at its peak value . At time 1 3, when the current J has essentially reached its peak value and when the voltage across C 6 has dropped to essentially zero, the ignitron / 2 is ignited, whereby C 6 is connected. This prevents the voltage across C 6 from reversing, which would damage the capacitor. However, the voltage at L 6 is still transmitted to L 8, which for the reasons mentioned above is now sufficient to maintain the ring discharge current. Since / 1 and / 2 do not have sufficient current capacity to allow the peak current to pass for a longer period of time, the mechanical switching mechanism S 7 is closed shortly after / 2 ignites (about 2 milliseconds afterwards) at time i4. The peak current is now maintained for the time it takes to discharge the delay line. At time f5, / 4 is fired, so that the current and voltage drop exponentially.

Since S6 and S7 take a relatively long time to respond (40 and 57 milliseconds respectively), the discharge cycle will actually begin at time i6. This is done by closing 6 * 7, with closing 56 shortly after time i7

The voltage does not drop immediately across the remaining four Ignitrones, thus preventing these remaining four from igniting. The capacitor C 7 , together with the inductance of the line that is located between it and the transformer primary winding L 8, exerts a short delay on a pulse which arrives at the anode of II from one of the four other control circuits, and thus results sufficient time to ignite.

In order to reduce the control circuit inductance, connections that receive current pulses are coaxial cables used.

It should be noted that the above-mentioned described embodiment is only an inventive

begins. Closing these derailleurs is done by
■ a timer unit 6 controlled, which in turn
is controlled by a main timer 7, which the
Charging switchgear S8 and 6 * 9 actuated. An electromechanical lock ensures that S 6 is 5
is closed and that S 7 closes before Jl ignites
will. / 2 is ignited by a control circuit 8,
which triggered by a potentiometer RIl
connected to C 6. / 4 is replaced by a
similar control circuit 9 ignited, which of a to
Potentiometer R12 is triggered, which is connected to the
Delay line is connected near switch ^ 6. To prevent the possibility
that the voltage across the capacitors Cl bis
C5 then reverses when the voltage wave from the circuit arrangement according to the invention and that other far end of the line is reflected, ie due to possibilities in which the invention uses a short circuit at the 5 "6 ~ end, the Ignitron can be easily conceivable. The reason / 3 is connected to the remote end.This is triggered by a control circuit 10 for the use of five primary windings, which can be looked for by a potentiometer, for example, in that the current consumption 13 is triggered, which is connected to this connection capacity of the Ignitron With a discharge current of The repetition period or frequency of the discharge is ΙΟ ⁸ amperes, with a winding ratio of charges, the total primary current varies between 50 and 150 seconds. This is considerable Since this is a comparatively long period of time, more than a single ignitron can hold, it is preferred that the reaction chamber be between 25 ° C. By using five primary windings and five ignid discharges through a series of smaller discharge trons, the current in each is reduced to about 35 kA operating at a higher repetition frequency,

keep effective. For this reason, the trans- Another possible modification is to

formator Tl control circuit 12 is connected to a further primary coil L 20 separate primary windings for establishing derRingentausgestattet, which legally obtained at a low energy excitation charge 30 (period 12-1 5) and on. This is essentially to be used for this discharge (period i4 to i5).

borrowed the same steering committee as described elsewhere is. The repetition period of the control circuit 12 is controlled by the timer 7 so that that it is about 10 seconds.

The holding voltage, which is generated via the secondary windings L 6, L 16, L 17, L 18 and L 19, can be increased by regulating the taps on the transformer T 2 and / or by the voltage

In fact, there is an advantage with the control circuits according to the invention that the two functions (a) the build-up of the discharge current and (b) the maintenance of the discharge current while that the reactions are supposed to take place are separated from each other. For the first function, an a A control circuit with a short time constant and a strong electric field are required to generate the magnetic

which the capacitors Cl to CS are charged by the current source 11 40 energy which is assigned to the discharge channel, are changed. To build up quickly. This current is largely determined by the impedance of the delay line, the countermeasure, by the control circuit inductance, and the standing impedance is adapted to the ring discharge, and relatively little energy is lost. Has been although after last impedance across Tl and T2 environmentally begewandelt for maintaining the ring discharge, the values of the induction can 45 urged energy by means determined by the losses in the ring gates Ll to L4 of the discharge located on them (radiation , Derivation after the taps can be adjusted. In this way torus walls, etc.), so that one can change the impedance of the delay line between a relatively small electric field, which, however, can be changed between 1.8 and 14.35 ohms. As a result, the delay line discharge has to be maintained over a relatively long period of time, of course, changes the charging time, ie the time between i2 and tS,. The hold circuit does not necessarily have to have a connection between a minimum value of 30 multi-delay line. With him can beiseconds and a maximum value of 230 milliseconds. For example, if no current waveform is flat, it is also possible to adjust the impedance by changing the peak value, a simple capacitor of the values of capacitors Cl to C 5, 55 of which can be used, and transformer T 2 , each of a plurality of smaller ones connected in parallel - when the holding charge of low voltage in teter capacitors is to change. When a larger capacitor is stored, they are omitted. Ratio of 6: 1 to Tl can Enladeimpedanzen However, this is an uneconomical process in the range of 7.7 × 10 ^-5 to 1.17 x ΙΟ ^"6 Ohm by the storage of the charge represents Alternatively, a regulating the induction can Ll to L. are obtained 4, 60 homopolar generator, or other device, wherein the range of the voltage divider ratios which a high current at low voltage to T2 account must be taken to write the case of a, be used, the transformer ratio. 6: 1 to Tl , the pulse rise T2 is again omitted, it is also mögzeit (from t2 to i3) about 1.8 milliseconds during lent to make the assembly so that the construction of voltage divider ratios. 12: 1 and 24: 1, depending - 65 control circuit and the hold circuit relative to the primary because rise times of 3.6 and 7.2 milliseconds development are connected in parallel instead of in series, as is the case in the exemplary embodiment described The capacitor C7 located within the is; In such circuit arrangements there is a control circuit, so that if one of the five ignitrones should trigger the switching mechanism and ignitron time setting somewhat before the others, the chip 70 is more critical.

Throughout the description of the invention, the term "switching device" refers to both mechanical switchgear as well as discharge devices, for example Ignitrone.

Claims (6)

Patent claims: 1. Circuit arrangement for a gas-filled reaction chamber in which by transmission a brief high-voltage pulse ίο from a first excitation control circuit a primary winding of a pulse transformer caused a heavy current ring discharge which forms the secondary winding of the pulse transformer, characterized in that a second excitation control circuit for generating a low voltage pulse of relatively long duration and switching means for coupling the mentioned second control circuit to the mentioned secondary winding are provided to the ring discharge current for a longer period Time to keep at a high value if the high voltage pulse is already on a low value has fallen. 2. Circuit arrangement according to claim 1, characterized in that the two mentioned Excitation control circuits are placed in series on the same primary winding as the one mentioned low voltage pulse of relatively long duration before the start of the short one High voltage pulse is applied. 3. Circuit arrangement according to claim 2, characterized by switching devices for the Short-circuiting said first excitation control circuit when the high voltage pulse from this control circuit has dropped to a low value. 4. Circuit arrangement according to claim 1, 2 or 3, characterized in that the first excitation control circuit a capacitor and a second switching device for discharging the Has capacitor across the primary winding of the pulse transformer. 5. Circuit arrangement according to claims 1 to 4, characterized in that said second excitation control circuit comprises a charge delay line. 6. Circuit arrangement according to claims 1 to 5, characterized in that the second excitation control circuit is set up in such a way that it can store energy at high voltage, and that he has a second pulse transformer for reducing the high voltage to: has required low voltage. 1 sheet of drawings © S09 769/452 3.