200 kV pulse generator for a power supply of the electron gun for the complex VEPP-5 preinjector
A 200 kV DC power source on the base of a high-voltage cascade generator [1] is used for a power supply of the electron gun for the VEPP-5 complex preinjector. Advantages of the circuit with DC power supply are its relative simplicity and small power consuming from an AC line. However, a fixed volta...
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| Veröffentlicht in: | Вопросы атомной науки и техники |
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| Datum: | 1999 |
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| Sprache: | Englisch |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
1999
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| Zitieren: | 200 kV pulse generator for a power supply of the electron gun for the complex VEPP-5 preinjector / V.E. Akimov, I.V. Kazarezov, A.A. Korepanov // Вопросы атомной науки и техники. — 1999. — № 4. — С. 46-48. — Бібліогр.: 6 назв. — англ. |
Institution
Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1860114403261677568 |
|---|---|
| author | Akimov, V.E. Kazarezov, I.V. Korepanov, A.A. |
| author_facet | Akimov, V.E. Kazarezov, I.V. Korepanov, A.A. |
| citation_txt | 200 kV pulse generator for a power supply of the electron gun for the complex VEPP-5 preinjector / V.E. Akimov, I.V. Kazarezov, A.A. Korepanov // Вопросы атомной науки и техники. — 1999. — № 4. — С. 46-48. — Бібліогр.: 6 назв. — англ. |
| collection | DSpace DC |
| container_title | Вопросы атомной науки и техники |
| description | A 200 kV DC power source on the base of a high-voltage cascade generator [1] is used for a power supply of the electron gun for the VEPP-5 complex preinjector. Advantages of the circuit with DC power supply are its relative simplicity and small power consuming from an AC line. However, a fixed voltage applied to the gun at a beam current of 10 А causes frequent vacuum insulation breakdowns, which decrease its electrical strength. Therefore a problem was stated to develop a high-voltage pulse generator, which will allow us to increase an electrical strength. Furthermore, a small capacitance of the pulse transformer and so less stored energy reduce probability of failure of the gun’s electrodes during its breakdown.
|
| first_indexed | 2025-12-07T17:35:21Z |
| format | Article |
| fulltext |
200 KV PULSE GENERATOR FOR A POWER SUPPLY OF THE
ELECTRON GUN FOR THE COMPLEX VEPP-5 PREINJECTOR
V.E. Akimov, I.V. Kazarezov, A.A. Korepanov
Budker Institute of Nuclear Physics, Novosibirsk, Russia
A 200 kV DC power source on the base of a
high-voltage cascade generator [1] is used for a power
supply of the electron gun for the VEPP-5 complex
preinjector. Advantages of the circuit with DC power
supply are its relative simplicity and small power
consuming from an AC line. However, a fixed voltage
applied to the gun at a beam current of 10 А causes
frequent vacuum insulation breakdowns, which decrease
its electrical strength. Therefore a problem was stated to
develop a high-voltage pulse generator, which will
allow us to increase an electrical strength.
Furthermore, a small capacitance of the pulse
transformer and so less stored energy reduce probability
of failure of the gun’s electrodes during its breakdown.
HIGH-VOLTAGE INSULATION
CHARACTERISTICS IN A PULSE MODE
SF6 gas under pressure of 1.7 atm is used as an
external insulation of the electron gun and main
insulation of the pulse transformer (PT). It is not
dangerous to operate vessels at such pressure and the
legal requirements are reduced in Russia. This choice of
gas insulation is based on its small dielectric
permeability, which provides minimum capacity of
high-voltage elements of the generator. The gas
insulation is easier at repair and setting up in
comparison with liquid (for example, with oil,
especially − at vacuum volume opening), and the
ecological problems of SF6 use are still under
discussion.
The choice of operating pulse duration as well as
operating gradients of SF6 and vacuum insulation was
made in view of electrical strength as a function of pulse
duration.
Empirical voltage applying time t [2] dependence
of a product of breakdown intensity E into a voltage V
was used for vacuum:
)(,100 2
34.0 mm
kV
tVE =⋅ ,
then for a gap of 100 mm breakdown intensity
dependence looks like (see also Fig.1):
cm
kV
tE 17.0
10= .
The data on electric strength for SLAC klystrons
[3] turn out to be close to an estimated curve.
Thus, reducing the voltage applied duration
down to 1 µs and less, it is possible to increase a
breakdown voltage in vacuum at least twice in
comparison with a constant voltage. Vacuum electric
strength along the surface also depends on the applied
voltage duration. According to [4] the electrical strength
for a 20 mm long fluoroplastic insulator grows fourfold
at reduction of a applied constant voltage duration down
to 0.2 µs.
Fig. 1: The breakdown electric field strength in vacuum
versus applied voltage duration.
Time dependence of SF6 insulation electrical
strength for small pressures and gaps is less distinct.
Thus, changing to forming the pulses with
duration up to 1 µs allows us to sharply increase
vacuum insulation gradients or reduce the breakdown
probability for chosen operating gradients.
CIRCUIT OF THE PULSE FORMER
The initial data for a choice and simulation of the
generator's circuit are pulse and load parameters:
Gun cathode voltage of 200 kV;
Beam current of 10 A;
Beam current pulse duration (at half-height) of 2 ns;
Gun capacitance of ~50 pF;
Voltage pulse duration at a gun cathode not longer than
1 µs.
Because the gun capacitance is discharged during
a beam current pulse not more than by 0.2 %, the action
of a beam current on the voltage shape may be ignored,
considering capacitance of the gun and high-voltage
elements of the device as a load of the generator.
Fig. 2: Simulation circuit of the pulse former.
The basic criteria for the choice of the pulse former
circuit were:
Possibility to obtain a pulse with duration no longer
than 1 µs;
Simplicity of manufacturing and compactness of the
generator.
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 1999. № 4.
Серия: Ядерно-физические исследования (35), с. 46-48.
46
Given above, a simple circuit of capacitance
resonant charge through the step-up PT has been taken
as a base.
Fig. 2 represents the circuit of the pulse former
used for simulations. All circuit parameters are referred
to a secondary winding of PT. С1 is a capacitance of the
primary circuit storage, С2 represents the total
capacitance of the gun, PT, and other high-voltage
elements of the generator. For complete energy transfer
from С1 to С2 their values should be equal:
С1=С2~80 pF. Ls is a PT leakage inductance, L1 is an
inductance of the primary contour. The primary circuit
switch is replaced by the diode D1. Parameters of the
contour (Ls, L1, С1) were simulated and chosen so that
the capacitance C2 charge time t did not exceed 0.5 µs,
i.e.
5.022)1( ≤⋅+= CLsLπτ µs.
An operating feature of this circuit is generation
of a pulse fall time by a saturated PT. Both PT core
section and number of turns as well as a reset current
are chosen so that the induction in the core is average
out to the saturation induction in a moment of pulse top.
Then at once after pulse top generation the capacitance
С2 begins to discharge through the magnetization
inductance of a saturated PT satLµ , and pulse fall is
generated. In the simulation circuit on Fig.2 the
phenomenon of saturation is simulated by placing the
inductance satLµ in parallel with PT magnetization
inductance µL . A circuit formed of the resistor R and
diode D2 placed in parallel to the load is used to limit
the subsequent inverse overvoltage on a load. A power
of 100 W is dissipated in resistor R. Its resistance was
chosen such that inverse overvoltage was not more than
40 % from the peak value.
The current and voltage curves in the circuit are
shown on Fig.3a. These drawing show that the
amplitude of a current (referred to the secondary
winding) through the switch makes about 55 А. For PT
with transformation ratio ~20 it will make about 1.1 kA.
Thus, allowing for small duration of a pulse, it is
possible to use thyratron TGI1-1000/25 as the primary
switch. Charging voltage on C1 capacitor will make not
more than 10 kV. The capacitance storage was
assembled from 6 ceramic capacitors К15-10 10000/40,
and the high-voltage diode assembly from 4-th SDL-
type diode stacks was used.
Fig. 3: Current and voltage shapes for the circuit
presented on Fig.2. a) − with D2-R circuit, b) − with
D3-R1 circuit.
Besides the considered circuit with high-voltage
D2-R circuit there was analyzed the similar pulse
former circuit, but with an absorber circuit at the
primary side of PT (on Fig. 2 this circuit (D3-R1) is
represented by a dotted line). In this case high-voltage
design of the generator becomes essentially simpler due
to absence of any elements in the secondary circuit of
PT except for the actual electron gun. Simultaneously
capacitance C2 of the secondary circuit decreases in
some degree that reduces capacitance of the generator.
However, due to rather large value of PT leakage
inductance Ls, comparable with PT inductance in a
saturated mode satLµ , the energy dissipation processes
in a circuit D3-R1 are delayed, and inverse overvoltage
on a load is increased. The simulated curves of voltage
and currents in elements of the circuit are shown on
Fig.3b. The transient process after pulse fall generation
is of oscillating type and it cannot be changed by
choosing R1 resistance. The effective pulse duration in
view of the oscillations can be adjusted by changing a
core reset current. Therefore it is possible to obtain a
rather short pulse at an acceptable inverse overvoltage
by making trade-off. The given variant of the generator
is supposed to be tested hereinafter after manufacturing
the high-voltage high-current diode for the circuit D3-
R1.
DESIGN OF THE GENERATOR
Structurally the generator is carried out from 2
parts: a high-voltage part including PT and diode circuit
and low-voltage block, consisting of charge device,
capacitance storage, and of a primary circuit switch.
Location of the PT and electron gun in the same tank
allows us to simplify high-voltage performance of
elements of the generator and cathode of a gun.
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 1999. № 4.
Серия: Ядерно-физические исследования (35), с. 46-48.
46
Fig. 4: PT design.
The basic part of the generator is PT. The sketch
of the transformer is shown on Fig.4. Structurally PT is
carried out similarly [6]. The core (1) is of continuous
type and carried out from a tape of amorphous alloy
2NSR by thickness of 25 microns. The toroidal shape of
the core allows us to receive the minimum PT leakage
inductance at given length of an average line of the core
at the expense of the best use of its length. The design
of the continuous core with a sound magnetic material
allows us to reduce to a minimum magnetization losses
in PT. The PT secondary winding is carried out from
two symmetric parallel parts (2). The high-voltage
edges of windings rejoin each other, therefore the
electrical field between windings is practically
homogeneous in such design. Using two parallel
branches of a secondary winding allows us to use them
for a feed of a heat circuits of the cathode and grid
control. For reduction of leakage inductance the
secondary winding is of cone type (only in a radial
direction). For the same purpose the primary winding
(3) is carried out of lump of parallel conductors with
return leads (4), which run under lateral cheeks of a
skeleton. Both primary and secondary windings were
reeled up with conductor having polyethylene isolation
by a diameter 1.4 mm for increase of their electrical
strength. The absence of a skeleton on an internal
generating line of the secondary winding excludes an
opportunity of breakdowns along the surface. Fastening
the secondary winding and PT itself is provided with
bars from glass-reinforced dielectric material.
TEST RESULTS
To the present days the nominal parameters of a
pulse were obtained on a dummy load: 200 kV at a
pulse repetition frequency of 50 Hz. The PT output
voltage (Fig.5) was registered by a capacitor divider.
Capacitance of a divider made ~60 pF and played a role
of equivalent capacitance of the gun. PT, diode circuit,
and capacitor divider were located in a SF6 filled tank
under pressure of 1.7 atm.
Fig. 5: Voltage pulse shape on a dummy load.
REFERENCES
[1] The Physical project of a complex VEPP-5,
Budker Institute of Nuclear Physics, Novosibirsk, 1995.
[2] V. Latham High Voltage Vacuum Insulation,
London, Academic press, 1995, 568 p.
[3] Breakdown Phenomena in High Power
Klystrons – ХШ Int. Symp. On Dish. And El. Insul. In
Vacuum, Paris, France, June 27 - 30, 1988.
[4] Kalyatsky I.I., Kassirov G.M. – Research of
pulse surface breakdown of some solid dielectrics in
vacuum, - Journal of Technical Physics, v. XXIV, is. 8,
pp. 1471-1475 (in Russian).
[5] Borin V.N. Volt-second characteristic of the
electrical discharge in elegas. Elektrisity, 1973, N5,
pp.62-67 (in Russian).
[6] I. Kazarezov, G. Krainov, Pulse transformer
for NLC klystron. – Third Annual Klystron-Modulator
Workshop, June 23-25, 1998, Workshop paper.
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 1999. № 4.
Серия: Ядерно-физические исследования (35), с. 46-48.
46
|
| id | nasplib_isofts_kiev_ua-123456789-81528 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-12-07T17:35:21Z |
| publishDate | 1999 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Akimov, V.E. Kazarezov, I.V. Korepanov, A.A. 2015-05-17T16:45:47Z 2015-05-17T16:45:47Z 1999 200 kV pulse generator for a power supply of the electron gun for the complex VEPP-5 preinjector / V.E. Akimov, I.V. Kazarezov, A.A. Korepanov // Вопросы атомной науки и техники. — 1999. — № 4. — С. 46-48. — Бібліогр.: 6 назв. — англ. 1562-6016 https://nasplib.isofts.kiev.ua/handle/123456789/81528 A 200 kV DC power source on the base of a high-voltage cascade generator [1] is used for a power supply of the electron gun for the VEPP-5 complex preinjector. Advantages of the circuit with DC power supply are its relative simplicity and small power consuming from an AC line. However, a fixed voltage applied to the gun at a beam current of 10 А causes frequent vacuum insulation breakdowns, which decrease its electrical strength. Therefore a problem was stated to develop a high-voltage pulse generator, which will allow us to increase an electrical strength. Furthermore, a small capacitance of the pulse transformer and so less stored energy reduce probability of failure of the gun’s electrodes during its breakdown. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники 200 kV pulse generator for a power supply of the electron gun for the complex VEPP-5 preinjector 200-кВ импульсный генератор для питания электронной пушки форинжектора комплекса ВЭПП-5 Article published earlier |
| spellingShingle | 200 kV pulse generator for a power supply of the electron gun for the complex VEPP-5 preinjector Akimov, V.E. Kazarezov, I.V. Korepanov, A.A. |
| title | 200 kV pulse generator for a power supply of the electron gun for the complex VEPP-5 preinjector |
| title_alt | 200-кВ импульсный генератор для питания электронной пушки форинжектора комплекса ВЭПП-5 |
| title_full | 200 kV pulse generator for a power supply of the electron gun for the complex VEPP-5 preinjector |
| title_fullStr | 200 kV pulse generator for a power supply of the electron gun for the complex VEPP-5 preinjector |
| title_full_unstemmed | 200 kV pulse generator for a power supply of the electron gun for the complex VEPP-5 preinjector |
| title_short | 200 kV pulse generator for a power supply of the electron gun for the complex VEPP-5 preinjector |
| title_sort | 200 kv pulse generator for a power supply of the electron gun for the complex vepp-5 preinjector |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/81528 |
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