Peaking capacitor layout

Details Peaking capacitor layout Peaking capacitor layout

2000-09-08

2002-04-23

Scott, Jr., Leon (Department: 2881)

Coherent light generators

Particular component circuitry

Power supply

Reexamination Certificate

active

06377595

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a peaking capacitor layout used for a power-supply unit of a laser device.
2. Description of the Related Art
Recently, a lot of magnetic pulse compression circuits are used for the power-supply unit of a high power pulse laser device. The durability of main switches such as a thyratron and GTO is improved by using the magnetic pulse compression circuit. The magnetic pulse compression circuit of such a type is known described in Japanese Patent Application Laid-Open Publication No. 5-167158.
FIG. 10
shows a capacitance transit type magnetic pulse compression circuit used for the power -supply unit of a pulse laser device. As shown in
FIG. 10
, one of plates of peaking capacitor Cp
1
is connected to discharge electrode
2
(cathode) through electric signal line
11
a
. The other plate of the peaking capacitor Cp
1
is connected to another discharge electrode
3
(anode) through electric signal line
11
b
. In other words, the peaking capacitor Cp
1
is electrically connected in parallel to the discharge electrodes
2
,
3
through loop (current circuit) Lp
1
. The discharge electrodes
2
,
3
are disposed in a laser medium.
FIG. 11
shows a layout of peaking capacitors Cp
1
.
FIG. 11
is a diagram showing the discharge electrodes
2
,
3
viewed from their sides.
As shown in
FIG. 11
, a plurality of peaking capacitors Cp
1
having the same capacitance are disposed in a row along the longitudinal directions of the discharge electrodes
2
,
3
. The peaking capacitors Cp
1
are connected to conductor
9
. The conductor
9
is electrically connected to the discharge electrode
2
. A discharge is caused in discharge area
4
between the discharge electrodes
2
,
3
.
Then, when an unshown main switch is turned on in
FIG. 10
, electric charges are supplied to and accumulated in charging capacitor Cn. When a time integral of a recharging voltage of the charging capacitor Cn reaches a limiting value which depends on a predetermined characteristic of magnetic switch Ln, the magnetic switch Ln is saturated, and the electric charges are transferred to and accumulated in the peaking capacitor Cp
1
. The recharging voltage of the peaking capacitor Cp
1
increases as the transfer of electric charges progresses. Then, when the recharging voltage of the peaking capacitor Cp
1
reaches a predetermined main discharge start voltage, a laser gas between the discharge electrodes
2
,
3
is undergone an electric breakdown, and the main discharge is started. The laser medium is excited by the main discharge, and laser light is emitted in several nsec.
Then, the recharging voltage of the peaking capacitor Cp
1
is quickly lowered by the main discharge, and the state before starting the charging is resumed after a lapse of a predetermined period of time.
Such a discharge operation as above is repeated by the switching operation of the main switch, and a pulse laser is oscillated at a predetermined repetition frequency (pulse oscillation frequency).
FIG. 5
shows the waveform of electric current i flowing through the loop Lp
1
of the peaking capacitors Cp
1
and the discharge electrodes
2
,
3
. The horizontal axis in
FIG. 5
indicates time t. The electric charges are transferred from the peaking capacitors Cp
1
to the discharge electrodes
2
,
3
over time &tgr;
1
, and the discharge is caused between the electrodes
2
,
3
. The area surrounded by the current waveform in
FIG. 5
corresponds to a magnitude (laser light power) of discharge energy between the discharge electrodes
2
,
3
.
The discharge energy becomes larger as a rising inclination of the current waveform becomes large and the transition time &tgr;
1
becomes shorter. It is known that the rising inclination of the current waveform can be made larger and the transition time &tgr;
1
shorter by reducing the capacitance of each peaking capacitor Cp
1
in FIG.
11
.
To decrease the capacitance of each peaking capacitor Cp
1
in
FIG. 11
, it is necessary to increase the number of peaking capacitors Cp
1
in one row so to have the same discharge energy.
But, the peaking capacitors Cp
1
must be disposed in two rows in order to arrange many of them because the discharge electrodes
2
,
3
have a limited length in their longitudinal directions.
FIG. 12
shows an example that the peaking capacitors Cp
1
are disposed in a first row close to the discharge electrode
2
and the peaking capacitors Cp
2
are disposed in a second row distant from the discharge electrode
2
. The respective peaking capacitors Cp
1
, Cp
2
have the same capacitance in
FIG. 12
which is smaller than that of the each peaking capacitor Cp
1
of FIG.
11
.
FIG. 6
shows the waveform of electric current i flowing through the loop Lp
1
of the peaking capacitors Cp
1
in the first row and the discharge electrodes
2
,
3
and the waveform of electric current i flowing through loop Lp
2
of the peaking capacitors Cp
2
in the second row and the discharge electrodes
2
,
3
of FIG.
12
.
The loop Lp
2
is longer than the loop Lp
1
because the peaking capacitors Cp
2
in the second row are distant from the discharge electrodes
2
,
3
as compared with the peaking capacitors Cp
1
in the first row.
Because the peaking capacitors Cp
1
in the first row of
FIG. 12
have the capacitance smaller than the peaking capacitors Cp
1
of
FIG. 11
, the electric charges are transferred to the discharge electrodes
2
,
3
with an arising inclination larger and transition time &tgr;
2
smaller than those of the current waveform of FIG.
5
. But, the peaking capacitors Cp
2
in the second row of
FIG. 12
have the capacitance smaller than the peaking capacitors Cp
1
of
FIG. 11
, but the rising inclination of the current waveform is small and transition time &tgr;
3
becomes larger than the transition time &tgr;
2
because the loop Lp
2
is longer than the loop Lp
1
.
Therefore, there is a problem that the discharge energy is canceled in the time &tgr;
3
−&tgr;
2
and the discharge energy is lowered.
Accordingly, it is a first object of the present invention to prevent the discharge energy from lowering even when the peaking capacitors are disposed in a plurality of rows with their capacitance lowered and their quantity increased.
Where the peaking capacitors are disposed in two rows as shown in
FIG. 12
, the disposed intervals and quantity of the peaking capacitors become different between the first and second rows. The disposed intervals of the peaking capacitors Cp
2
in the second row of
FIG. 12
are larger than those of the peaking capacitors Cp
1
in the first row, and the quantity of the peaking capacitors Cp
2
in the second row is smaller than that of the peaking capacitors Cp
1
in the first row.
Therefore, the peaking capacitors Cp
1
, Cp
2
have nonuniform capacitance at the respective points in the longitudinal directions of the discharge electrodes
2
,
3
. The nonuniform capacitance of the peaking capacitors Cp
1
, Cp
2
results in nonuniform dispersion of the discharge energy.
FIG. 9
is a conceptual diagram showing dispersion of discharge A when it was caused by the layout shown in FIG.
12
.
As shown in
FIG. 9
, because the peaking capacitors Cp
1
, Cp
2
have nonuniform capacitance at the respective points in the longitudinal directions of the discharge electrodes
2
,
3
, the discharge A also has a nonuniform dispersion as indicated by slanted lines. The nonuniform discharge means that stable laser power cannot be obtained.
Accordingly, it is a second object of the present invention to make the discharge energy dispersion uniform so to obtain stable laser power even when the peaking capacitors are lowered their capacitance, increased their quantity and disposed in a plurality of rows.
OBJECTS AND SUMMARY OF THE INVENTION
It is a first object of the first aspect of the invention to prevent discharge energy from lowering even when the peaking capacitors are decreased their capacitance, increased their quantity and disposed in a plurality of rows.
The first

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