Pulse modulators for the VEPP-5 injection complex klystron power supply
In the complex VEPP-5 preinjector the klystrons are supplied by the modulators with a pulse power of 150 MW, a voltage of 47.5 kV, a primary current of 6.3 kA and a pulse duration of 3.5 ms. During the long time operation some disadvantages in the design have been revealed and proper improvements we...
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irk-123456789-792222015-03-31T03:02:01Z Pulse modulators for the VEPP-5 injection complex klystron power supply Akimov, A.V. Akimov, V.E. Bak, P.A. Kazarezov, I.V. Kot, N.H. Chupyra, A.G. Rezakov, A.M. Yudin, V.D. In the complex VEPP-5 preinjector the klystrons are supplied by the modulators with a pulse power of 150 MW, a voltage of 47.5 kV, a primary current of 6.3 kA and a pulse duration of 3.5 ms. During the long time operation some disadvantages in the design have been revealed and proper improvements were made. The modulator design with the taking into account all the resent changes is described and test results are presented. At present, three modulators are supplying three klystrons 5045 (production of SLAC Lab., USA) and the forth modulator is tested with a dummy load in the nominal mode of operation. 2001 Article Pulse modulators for the VEPP-5 injection complex klystron power supply / A.V. Akimov, V.E. Akimov, P.A. Bak, I.V. Kazarezov, N.H. Kot, A.G. Chupyra, A.M. Rezakov, V.D. Yudin // Вопросы атомной науки и техники. — 2001. — № 3. — С. 92-94. — Бібліогр.: 4 назв. — англ. 1562-6016 PACS numbers: 29.17.+w, 84.40.Fe http://dspace.nbuv.gov.ua/handle/123456789/79222 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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| description |
In the complex VEPP-5 preinjector the klystrons are supplied by the modulators with a pulse power of 150 MW, a voltage of 47.5 kV, a primary current of 6.3 kA and a pulse duration of 3.5 ms. During the long time operation some disadvantages in the design have been revealed and proper improvements were made. The modulator design with the taking into account all the resent changes is described and test results are presented. At present, three modulators are supplying three klystrons 5045 (production of SLAC Lab., USA) and the forth modulator is tested with a dummy load in the nominal mode of operation. |
| format |
Article |
| author |
Akimov, A.V. Akimov, V.E. Bak, P.A. Kazarezov, I.V. Kot, N.H. Chupyra, A.G. Rezakov, A.M. Yudin, V.D. |
| spellingShingle |
Akimov, A.V. Akimov, V.E. Bak, P.A. Kazarezov, I.V. Kot, N.H. Chupyra, A.G. Rezakov, A.M. Yudin, V.D. Pulse modulators for the VEPP-5 injection complex klystron power supply Вопросы атомной науки и техники |
| author_facet |
Akimov, A.V. Akimov, V.E. Bak, P.A. Kazarezov, I.V. Kot, N.H. Chupyra, A.G. Rezakov, A.M. Yudin, V.D. |
| author_sort |
Akimov, A.V. |
| title |
Pulse modulators for the VEPP-5 injection complex klystron power supply |
| title_short |
Pulse modulators for the VEPP-5 injection complex klystron power supply |
| title_full |
Pulse modulators for the VEPP-5 injection complex klystron power supply |
| title_fullStr |
Pulse modulators for the VEPP-5 injection complex klystron power supply |
| title_full_unstemmed |
Pulse modulators for the VEPP-5 injection complex klystron power supply |
| title_sort |
pulse modulators for the vepp-5 injection complex klystron power supply |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2001 |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/79222 |
| citation_txt |
Pulse modulators for the VEPP-5 injection complex klystron power supply / A.V. Akimov, V.E. Akimov, P.A. Bak, I.V. Kazarezov, N.H. Kot, A.G. Chupyra, A.M. Rezakov, V.D. Yudin // Вопросы атомной науки и техники. — 2001. — № 3. — С. 92-94. — Бібліогр.: 4 назв. — англ. |
| series |
Вопросы атомной науки и техники |
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| fulltext |
PULSE MODULATORS FOR THE VEPP-5 INJECTION COMPLEX
KLYSTRON POWER SUPPLY
A.V. Akimov, V.E. Akimov, P.A. Bak, I.V. Kazarezov, N.H. Kot, A.G. Chupyra,
A.M. Rezakov, V.D. Yudin
The Budker Institute of Nuclear Physics, 630090 Novosibirsk, Russia, Lavrentiev Ave., 11,
e-mail: I.V.Kazarezov@inp.nsk.su
In the complex VEPP-5 preinjector the klystrons are supplied by the modulators with a pulse power of 150 MW, a
voltage of 47.5 kV, a primary current of 6.3 kA and a pulse duration of 3.5 µs. During the long time operation some
disadvantages in the design have been revealed and proper improvements were made. The modulator design with
the taking into account all the resent changes is described and test results are presented. At present, three modulators
are supplying three klystrons 5045 (production of SLAC Lab., USA) and the forth modulator is tested with a dum-
my load in the nominal mode of operation.
PACS numbers: 29.17.+w, 84.40.Fe
1 FEATURES OF MODULATOR DESIGN
The basic circuit of modulators used for the VEPP-5
preinjector klystrons power supply is presented in
Fig. 1. Some features of the modulator operation (of the
first version) were described in [1, 2]. Basic changes in-
troduced into the circuit of the modulator with taking
into account the maintenance experience of over 5 years
are given below.
In a new version of the modulator circuit, instead of
two thyratrons TGI1-2500/50 connected in series, one
thyratron TGI1-5000/50 is used. The use of two thyra-
trons was complicated by the necessity of equalizing of
the currents flowing through each thyratron and with the
use of special synchronizing circuit for providing their
simultaneous operation. The shift to the single thyratron
enabled the synchronizing circuit removal, the simplifi-
cation of the trigger circuit, water cooling, power sys-
tems for filament and hydrogen generator (HG) as well
as the pulse forming network (PFN) circuit (see below).
At the same time, a new circuit of the thyratron fila-
ment was developed. It was designed for reducing the
thermal shock of the thyratron cathode in the process of
filament switching on. As is indicated in technical re-
port for thyratron TGI1-5000/50, the guaranteed number
of thermal cycles (heating of cold cathode), which
thyratron can withstand is limited by 500. The use of the
standby regime of the filament enables the increasing of
the thyratron resource time. In this case, the thyratron
filament voltage reduces down to 60% level of its nomi-
nal value. In addition, the operational resource of thyra-
tron increases by the choice of the most optimal process
of cathode heating. As the thyratron developers indicat-
ed, the nominal filament voltage should be applied to
the cathode by a jump and wait after that for 8 minutes
for the guaranteed heating of cathode. However, provid-
ing the smoother way of reaching the operational fila-
ment regime seems to be led to the decrease in thermal
shock at the cathode and, therefore, to the increase in
the thyratron lifetime. The circuit developed envisages
the standby regime and provides the automated smooth
process of reaching the nominal thyratron filament
regime. A high power voltage stability makes also the
positive effect on the thyratron lifetime.
Fig.1. Schematic diagram of the pulse modulator
used for klystron 5045 power supply.
In the developed filament circuit, an individual pow-
er supply for HG is not envisaged. In the process of the
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 2001. №3.
Серия: Ядерно-физические исследования (38), с. 92-94. 92
long-term operation the hydrogen pressure in thyratron
is reduced. In this connection, one has to make the cor-
rection of the HG operation voltage. A wrong choice of
HG operating voltage can put substantial changes into
operation of the entire modulator circuit as well as lead
to the destruction of thyratron because of an increase in
losses. In order to avoid critical regimes of thyratron op-
eration, it is recommended a periodical search for the
operating point of HG. Such a procedure at SLAC is
called "Ranging" [3]. In the process of the long-term op-
eration of modulators at the VEPP-5 complex, the thyra-
tron premature deionization was found (see below), it
led to the necessity of using "Ranging" for thyratrons
TGI1-5000/50.
According to SLAC recommendations, "Ranging"
procedure represents the search for the lower and upper
limit of HG. The operating point is determined as mean
of these values. The experience of "Ranging" procedure
realization at thyratrons TGI-5000/50 has shown that
such an approach is not optimal. For example, the upper
limit characterizing by the spontaneous opening of the
thyratron with the further loss of its deionizing proper-
ties and as a consequence, with an increase in the PFN
charge current (Fig.2), for one of thyratrons was found
out at the HG voltage level of 8.8 V (the search was per-
formed at lowered voltage level (Upfn = 30 kV), which
was determined by danger of the critical load to the
thyratron and other modulator components at the thyra-
tron loss of its deionizing properties). The lower level
for the same thyratron characterizing by the occurrence
of instability on the tail of the grid voltage pulse, was
found out at the HG voltage level of 5.5 V. The mean
value of 7.2 V is too high. HG operation at this voltage
will lead to its fast exhaust and further decrease of hy-
drogen pressure. Therefore, as an operating point for
this thyratron was chosen to be such a voltage, at which
the instability at the tail of the grid voltage was not ob-
served, of 6.7 V.
The procedure of searching the HG operating point
enabled a study of influence of the HG voltage level on
the delay time of thyratron switching on. With an in-
crease in HG voltage from 5.4 V up to 7.5 V the time
delay was decreased from 280 ns down to 100 ns. Fur-
ther increase in voltage does not influence much on the
change of time delay.
Fig. 2. Determining the HG upper limit by the in-
crease of the PFN charge current. Ich is PFN
charge current, Upfn is PFN voltage.
With the shift to the modulator operation with single
thyratron, the use of one PFN became possible. Before
there were used two PFN’s connected in parallel and
operated each to its thyratron. Both PFN’s were placed
into one tank filled with oil. New PFN made in air with
the use of high voltage pulse capacitors of the type
KMKI 50-0.04 of Sank-Petersburg production. Capaci-
tors are made in an insulated body at a voltage of 50 kV
and capacitance of 0.04 µF. The overall dimensions are
315x110x235, mass is 10.5 kg, specific energy is 10 kA,
inductance of the capacitor is 80 nH, resource is 10
pulses. The operation regime is the oscillating discharge
with voltage reverse up to 50%. In capacitors KMKI
50-0.004 the combined dielectric based on the
polypropylene film and paper insulation is used.
The shift to the air version of PFN substantially fa-
cilitated its design, made simpler its maintenance. How-
ever, it is worth mentioning that in oil version of FL the
heat removal from the line capacitors was provide what,
in principle, does not eliminate the possibility of raising
the modulator operating frequency. In the former ver-
sion of PFN the metal tank, playing role of the tank for
oil, reduced simultaneously the level of noise produced
by the PFN. In the new circuit, the noise level turned
out to be much higher and for its reduction we had to
take additional measures.
For the protection of the klystron and PFN against
energy release in the case of breakdown as well as for
dissipation the energy stored in the magnetizing induc-
tance (Lµ) during the pulse duration the clipper circuit
is used. It is connected in parallel to the last capacitor of
the PFN and is consisting of the diode, resistor and
varistor set. (Fig. 1). The absence of varistors leads to
prolongation of the magnetizing energy dissipation peri-
od up to 500 µs, which in its turn, produces a negative
effect on the thyratron deionization. At the same time,
with the long process of magnetizing energy dissipation
(>100 µs) in the thyratron with the lowered hydrogen
pressure the premature deionization can occur. It will
lead to the undesirable inverse voltage applying to the
klystron cathode. In order to avoid this effect one should
simultaneously increase HG voltage and make an opti-
mal choice of the varistor set parameters. It should pro-
vide the complete dissipation of the magnetizing energy
in less than 120 µs.
In the first modulator version, the high voltage
thyristor switch (HVS) was used. The small time of
thyratron deionization (~100-120 µs) enabled one to
avoid HVS and use the diode for the PFN resonant
charge. This made the modulator operation simpler and
reliable. The diode (or HVS) should be placed in the cir-
cuit only after the charge choke (Fig. 1) and not before
it. In this case, voltage applied to the diode does not ex-
ceed 24 kV. Otherwise, because of the reverse resonant
charge of the choke capacitance from the PFN capaci-
tance the higher inverse voltage of 72 kV is applied at
the diod, that can lead to its breakdown.
In the former modulator circuit a very expensive
nonstandard stepping up three-phase transformer of the
BINP production was used. At present it is replaced by
the standard transformer TM-100/35 designed at a pow-
er of 100 kWA. Inside the transformer tank the high
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 2001. №3.
Серия: Ядерно-физические исследования (38), с. 92-94.
93
voltage rectifier was installed that enabled the use only
one insulator instead of three one. For the charge of the
reasonable placement of the transformer frame, its over-
all dimensions were reduced.
As a result of experiments and calculations, we de-
cided not to use additional chokes located in phases of
the power mains. There were oriented to decrease the
efficient current at the modulator circuit input and to re-
duce the power consumed. However, in spite of the re-
duction of the efficient current value in phases, the ex-
cessive heating of power transformer was observed. It
was explained by an increase of constant component of
the phase current in the case with chokes that led to
magnetizing of the transformer and to its further over-
heating. In addition, the computer analysis of power
consumed by the modulator has shown that with the use
of chokes the consumed power is reduced insignificant-
ly. Further tests have proven these calculations and we
rejected the use of chokes.
2 MODULATOR CONTROL, MONITORING
AND PROTECTION SYSTEMS
For the successful maintenance of the modulator the
reliable control system, protection and diagnostics is re-
quired, which combines the whole complex of systems
related to the provision of the operability of the modula-
tor. Such a system was developed and manufactured at
BINP. The main functions of the modulator and
klystron control and protection are carried out by the
signaling and blocking system, the matching and fast
protection units.
The signaling and blocking unit receives information
on the blocking state controlling various parameters re-
sponsible for the safe operation of the modulator and
klystron, namely, water pressure in cooling system of
the main units of the modulator, the readiness of thyra-
tron filament power supply, the position of rods, modu-
lator doors and the high voltage turn on key. In the case
of normal conditions of all the blockings the unit gives
the permission for switching on the high voltage. Other-
wise, the unit issues a signal on the deviation by the
light diode signaling on the front panel and issues prohi-
bition for switching on high voltage.
The main function of the fast protection unit is pre-
ventive protection of the modulator and klystron at devi-
ations from the normal operation regime. In the case of
deviation of one ore more modulator or klystron param-
eters it might block the thyristor regulator, turn off the
thyratron trigger and call the high voltage switching off,
depending on the certain deviation. Information on any
deviation is displayed with the light diode indication on
the front panel of the unit. The possibility of transferring
this information to the control room is also envisaged.
The matching unit transforms the levels of signals
applying from measuring circuits of the modulator in or-
der to provide their acceptable values for the fast protec-
tion unit, ADC, and standard oscilloscope.
The control system enables the control of the modu-
lator operation both in the manual regime and with com-
puter from the control room. The control system, moni-
toring and protection systems are described in more de-
tail in [4].
3 MEASUREMENT RESULTS
Fig.3 shows the curves of current and voltage of the
klystron taken at the modulator operation in the nominal
regime.
Fig. 3. The klystron 5045 current and voltage
curves. Ikl - klystron current, Ukl - klystron voltage.
4 CONCLUSION
Modulators used for the VEPP-5 injection complex
klystron 5045 power supply for the operation period
over 5 years have shown to be the reliable and safe sys-
tems. The main advantage of modulators is its simple,
well-studied and broadly used scheme of pulse forming.
The main disadvantage of modulators should consider
their out-dated elemental base. The use of the modern
powerful semi-conducting devices and the use of im-
proved principles of pulse forming enables a substantial
improvement of many modulator parameters. At
present, the new modulator circuit with the improved
characteristics is under way now.
REFERENCES
1. V.E.Akimov, N.S.Dikansky et. al. Modulator for
klystron 5045 // Proceedings of the 1995 Particle
Accelerator Conference and International Confer-
ence on High Energy Accelerators. Dallas, USA.
1-5 May 1995, v. 2, p. 1263-1265.
2. В.Е.Акимов, П.А.Бак и др. Модуляторы для пи-
тания мощных импульсных клистронов санти-
метрового диапазона. // ВАНТ, серия: Ядерно-
физические исследования (29,30). 1997, выпуск
2-3, т. 2, с. 21.
3. W.A.Benjamin. The Stanford Two-Mile Accelera-
tor / R.B.Neal, ed., 1968, N.Y.
4. К.М.Губин и др. Система управления, защиты и
контроля модулятора клистрона 5045 и кли-
стронного поста” // Труды XVII Совещания по
ускорителям заряженных частиц, Протвино,
2000.
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