GB2252463A

GB2252463A - Electrical pulse generator of the saturable inductance type

Info

Publication number: GB2252463A
Application number: GB9126176A
Authority: GB
Inventors: Patrick Eyl; Patrick Baudoin
Original assignee: Commissariat a lEnergie Atomique CEA
Current assignee: Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Priority date: 1990-12-21
Filing date: 1991-12-10
Publication date: 1992-08-05
Anticipated expiration: 2011-12-10
Also published as: FR2670963A1; FR2670963B1; GB9126176D0; DE4141516A1; GB2252463B

Description

ELECTRICAL PULSE GENEPATOR OF THE SATURATABLE INDUCTANCE TYPE

DESCRIPTION

The present invention relates to an electrical pulse generator ccmprising a pulse shaping coaxial line, which has at least two coaxial electrodes, whereof one is an internal electrode, magnetic ca-npression means for charging said shaping line and which have a capacitor and a saturatable inductance located within the coaxial line and therefore surrounded by the internal electrode of said coaxial line, an electrical conducting means electrically connected to one end of the saturatable inductance and in contact with a substantially median part of the inter- nal electrode of the coaxial line and a magnetic switch with a satura- table inductance for discharging said coaxial line.

It more particularly applies to the formation of high power electrical pulses, e.g. with a view to supplying induction cells for producing and accelerating electron beams in induction accelerators.

The diagram of a known electrical pulse generator of the saturatable inductance type is given in fig. 1. The latter is shown and described in French patent application 8802865 of March 7 1988, which is referred to hereinafter as docunent I and to which reference should be made (cf. also application %U 89/08950, published on SeptEmber 21 1989).

The electrical pulse generator diagramatically shown in fig. 1 ccm prises a coaxial pulse shaping line Zo, which has two coaxial electrodes, magnetic carpression means for charging the coaxial line Zo, said mag netic carpression means incorporating a capacitor C2 and a saturatable inductance Ll connecting the capacitor C2 to the coaxial line Zo and a magnetic switch with a saturatable inductance L2 for discharging the coaxial line Zo.

Fig. 1 also shows a capacitor Cl, which initially contains the energy necessary for producing a pulse at the terminals of a load R connected to the coaxial line Zo by means of the switch L2. Fig. 1 also shows an inductance L3 making it possible to dEmagnetize the respective cores of the transformer T, the saturatable inductance Ll and the inductance L2 after the formation of an electrical pulse. This inductance L3 is supplied by a d.c. voltage of an apprepriate polarity for ensuring the demagnetization of said cores.

A known electrical pulse generator of the saturatable inductance type is diagrannatically shown in fig. 2. The generator of fig. 2 is already shown and described in EP-A-0292345, which is hereinafter called docunent II and to which reference should be made (cf. also US-A-4849649 of R3CHE et al and French patent application 8706015 of April 28 1987).

in the generator diagrannatically shown in fig. 2 are successively pro vided the transformer T, the magnetic =pression means incorporating the capacitor C2 (whose dielectric can be water) and the saturatable inductance Ll, the coaxial line Zo haiing two coaxial electrodes, nanely an internal electrode and an external electrode and the magnetic switch with the saturatable inductance L2.

It is therefore possible to obtain electrical pulses at the output of the generator diagramatically shown in fig. 2 on a series of coaxial cables CC.

It should also be noted that in the generator diagraffmatically shown in fig. 2, the saturatable inductance Ll is positioned within the coaxial line Zo (said saturatable inductance Ll being surrounded by the internal electrode of the coaxial line Zo) and the saturatable inductance L1 is electrically connected to a substantially median part of said internal electrode.

The coaxial line Zo is imnersed in an electrically insulating liquid such as water, as is permitted by the structure of the generator diagrannatically shawn in fig. 2. The saturatable inductance Ll is irrmersed in a liquid such as oil, the structure of the generator diag rannatically shown in fig. 2 preventing the mixing of these two liquids.

The generator shown in fig. 2 and that forming the object of docunent I make it possible to obtain voltages V, whose variations as a function 3 of time t form "square waves" of the type shown in dotted line form in fig. 3 and carrying the reference I. This square wave voltage I is in accordance with what would be obtained through charging the shaping line Zo by one end.

Thus, in the generator shown in fig. 2, everything happens as if the line Zo was charged by its end (end located on the side of the capacitor C2).

The arrows F in fig. 2 show the flow of the current corresponding to the charging of the line Zo and which takes place by the wall effect. Such a charging of the shaping line Zo by one end does not make it possible to obtain true voltage square waves having true "voltage plateaus".

The present invention aims at obviating this disadvantage. The problem solved by the present invention is the provision of an electrical pulse generator of the saturatable inductance type, in which the charging of the coaxial pulse shaping line takes place as close as possible to the centre of this line.

To solve this problem, the electrical pulse generator of the saturatable inductance type forming the subject matter of the present invention is characterized in that the internal electrode of the coaxial line thereof is perforated by a plurality of holes in the vicinity of the substantially median part of the internal electrode.

These holes make it possible to approach a charging of the coaxial line by its centre and improve the planeity of the voltage pulses.

The electrically conductive means can coaprise an electrically conductive plate electrically connected to said end of the saturatable inductance and whose periphery is in contact with the substantially median part of the internal electrode of the coaxial line.

The holes in the internal electrode of the coaxial line are preferably distributed over the entire periphery of said internal electrode with a 4 view to a uniform charging of the coaxial line.

According to a preferred embodiment of the generator according to the invention permitting an even closer approach to a charging of the coaxial line by its centre, the electrically conductive plate has at least one opening and the holes in the internal electrode of the coaxial line are located on either side of said substantially median part.

on either side of said substantially median part, the holes in the internal electrode are preferably distributed aver the entire periphery of the internal electrode with a view to a uniform charging of the coaxial line.

preferably, in order to arrive at a tzue charging of the coaxial line by its centre, the electrically conductive plate has a plurality of openings, on either side of said substantially median part, the holes are uniformly distributed over the corresponding periphery of the internal electrode and the openings in the plate are uniformly distributed around the axis of said plate.

The electrically conductive means can also have a plurality of flexible, electrically conductive foils fixed to the periphery of the electrically conductive plate in order to permit contact with the substantially median part of the internal electrode of the coaxial line.

The internal electrode of the coaxial line can have a cylinder of revolution shape and the electrically conductive plate can be diskshaped.

Finally, in a preferred embodiment of the generator according to the invention, the saturatable inductance located within the coaxial line is Immersed in a liquid such as liquid freon or oil, the coaxial line being bnersed in an electrically insulating liquid such as water and the generator also has electrically insulating, tight separating means 35 for preventing any contact between these liquids.

These separating means can be constituted by a tight, electrically insulating enclosure filled with liquid such as liquid freon or oil, placed within the coaxial line and containing the saturatable inductance.

The invention is described in greater detail hereinafter relative to nonlimitative embodiments and with reference to the attached drawings, wherein show:

Fig. 1 A diagram of a known electrical pulse generator of the saturatable inductance type described hereinbefore.

Fig. 2 A diagramatic view of a known electrical pulse generator of the saturatable inductance type which has already been described.

Fig. 3 The voltage pulses respectively obtained with the generator of fig. 2 and with a generator according to the invention.

Fig. 4 A diagramatic view of a special Embodiment of the generator according to the invention.

Fig. 5 A diagrammatic view of an electrically conductive plate forming part of the generator of fig. 4 and which makes it possible to connect to one another the saturatable inductance and the internal electrode of the coaxial line of said generator.

Fig. 6 Diagrannatically the current flow in the generator of fig. 4 during the charging of its coaxial line The electrical pulse generator according to the invention and diagrammatically shown in fig. 4 constitutes an iffprovement to the generator shown in fig. 2.

Fig. 4 shows the transformer T, the capacitor C2, the saturatable inductance Ll, the coaxial line Zo, the magnetic switch L2 and the coaxial line CC. The transformer T, the saturatable inductance Ll and the magnetic switch with the saturatable inductance L2 are all imnersed in oil H (transformer oil). Oil circulation means are provided in the generator of fig. 4, but are not shown therein.

Inter alia, the oil permits the cooling of the cores of the transformer T, the saturatable inductance Ll and the magnetic switch L2, said cores becaning heated when working at high frequencies (e.g. approximately 1 to 5 kHz). In place of oi-1, it would also be possible to use liquid freon.

The capacitor C2 and the coaxial line Zo are Innersed in water E (deionized water).

In order to prevent mixing between the oil H in which is immersed the saturatable inductance Ll and the water E in which is immersed the coaxial line Zo, the generator of fig. 4 has an electrically insulating, tight enclosure 2 located within the coaxial line zo and which houses the saturatable inductance Ll, as can be seen in fig. 4. Moreover, according to the invention, the internal electrode El of the coaxial line Zo has holes 4.

These holes 4 are located in the vicinity of and on either side of the electrically conductive plate MC, whose periphery is in contact with a substantially median part of the internal electrode EI and which is electrically connected to one end of the coil of the saturatable inductance Ll.

on either side of the plate MC, the holes 4 are uniformly distributed over the circanference of the internal electrode EI which, in the generator of fig. 4, is shaped like a cylinder of revolution, whose axis is the axis of the generator shown in fig. 4.

The plate MC is perpendicular to said axis. In the generator of fig. 4, the plate MC, which is outside the enclosure 2, is fixed to the latter by electrically insulating means 6. The plate MC, which is used in the generator shown in fig. 4, is diagrammatically shown in fig. 5. This diskshaped plate MC and whose axis is the axis of the generator of fig. 4 has a plurality of cpenings 8 uniformly distributed around the said axis.

Moreover, the disk-shaped plate MC is peripherally provided with a plurality of elastic, flexible, curved foils 10, which are electrically conductive and permit contact between the plate MC and the internal electrode EI, as can be seen in fig. 4. It can be seen in fig. 5 that the foils 10 are uniformly distributed over the periphery of the diskshaped plate MC.

As can be seen in fig. 4, in the diagrammatically shown generator thereof, the assembly canprising the enclosure 2, the saturatable inductance Ll and the plate MC forms an assembly which is mechanically independent of the remainder of the generator, which facilitates generator maintenance.

The apenings 8 of the plate MC in the generator of fig. 1 enable the current IC for charging the coaxial line Zo to flow in surface manner on the two faces of said plate MC. Moreover, the uniform distribution of these epenings 8 and holes 4 in the generator of fig. 4 permits a uniform distribution of the current flawing during the charging of the coaxial line Zo.

The arrows Fl in the diagram of fig. 6 indicate the flow of the current IC during the charging of the coaxial line Zo and it can be seen that the charging does take place through the centre of the coaxial line Zo in the case of the generator of fig. 4.

In fig. 4, the ratio DV/V, in which DV represents the fluctuation of the mean value of the maximum voltage (voltage plateau) of the pulses supplied by the generator and V represents said mean value, is significantly improved.

This is made clear in fig. 3, where it can be seen that the planeity of the square wave pulse is better in the case of the generator of fig. 4 (curve II) than in the case of the generator of fig. 2 (curve I).

The voltage square waves supplied by the generator of fig. 4 can be applied to induction cells used for producing and accelerating an electron bean usable in a free electron laser.

The fact that very flat voltage square waves are obtained makes it possible to produce a larger number of monoenergy electrons and conse quently significantly improve the efficiency of said free electron laser.

Obviously, the present invention is usable not only in a generator whose coaxial line has two coaxial electroMs, but also in a double coaxial Line generator, which is also known as a "Blumlein coaxial line" and which has three coaxial electrodes, namely a centre electrode between an internal electrode and an external electrode (cf. docunent I).

t

Claims

1. Electrical pulse generator ccnprising a coaxial pulse shaping line (Zo), which has at least two coaxial electrodes, one being an internal electrode (EI), magnetic caTpression means for charging said shaping line, said magnetic campression means having a capacitor (C2) and a saturatable inductance (L1) located within the coaxial line, an electrically conductive means (MC) electrically connected to one end of the saturatable inductance and which is in contact with a substantially median part of the internal electrode of the coaxial line and a magnetic switch with a saturatable inductance (L2) for discharging said coaxial line, said generator being characterized in that the internal electrode of the coaxial line has a plurality of holes (4) in the vicinity of said substantially median,part of said internal electrode.

2. Generator according to claim 1, characterized in that the electri cally conductive means rises an electrically conductive plate (MC) electrically connected to said end of the saturatable inductance (L1) and whereof the periphery is in contact with the substantially median part of the internal electrode (EI) of the coaxial line.

3. Generator according to claim 2, characterized in that the holes (4) in the internal electrode of the coaxial line are distributed over the entire periphery of said internal electrode.

4. Generator according to claim 2, characterized in that the electri cally conductive plate (MC) has at least one cpening (8) and in that the holes (4) in the internal electrode of the coaxial line are located on either side of said substantially median part.

5. Generator according to claim 4, characterized in that on either side of said substantially median part, the holes (4) in the internal elec- trode (EI) are distributed aver the entire periphery of said internal electrode.

6. Generator according to claim 5, characterized in that the electri- 9i cally conductive plate (MC) has a plurality of openings, in that on either side of said substantially median par-t, the said holes are uniformly distributed aver the corresponding periphery of the internal electrode and in that the openings (8) in the plate (MC) are uniformly distributed around the axis of said plate.

7. Generator according to any one of the claims 2 to 6, characterized in that the electrically conductive means also have a plurality of f lexible and electrically conductive foils (10) fixed to the periphery of the electrically conductive plate (MC) to permit contact with said substantially median part of the internal electrode (EI) of the coaxial line (Zo).

8. Generator according to any one of the claims 2 to 7, characterized in that the internal electrode (EI) of the coaxial line is in the form of a cylinder of revolution and in that the electrically conductive plate (MC) is disk-shaped.

9. Generator according to any one of the claims 1 to 8, characterized in that the saturatable inductance (L1) located within the coaxial line (Zo) is imersed in a liquid (H) such as liquid freon or oil, in that the coaxial line (Zo) is imersed in an electrically insulating liquid (E) such as water and in that the generator also has tight, electrically insulating separating means (2) for preventing any contact between these liquids (E, H).

10. Generator according to claim 9, characterized in that the separating means carprise an electrically insulating, tight enclosure (2) filled with liquid (H) such as oil or liquid freon, placed within the coaxial line (Zo) and containing the saturatable inductance (L1).

11. The electrical pulse generator of the saturatable inductance type substantially as herein described with reference to and as shown in the accompanying drawings.