Analysis of 400 kV pulse generator operation
The injector provides linac by 400 keV protons with energy stability ±0.1%, pulsed ion current - up to 100 mA, 50 Hz pulse repetition rate (PRR) with 200 μs duration. The results of the high-voltage pulse generator operation analysis which have been done with the aim of pulse repetition rate increas...
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| Zitieren: | Analysis of 400 kV pulse generator operation / E.S. Nikulin, A.S. Belov, O.T. Frolov, L.P. Nechaeva, A.V. Turbabin, V.N. Zubets // Вопросы атомной науки и техники. — 2015. — № 3. — С. 123-126. — Бібліогр.: 6 назв. — англ. |
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irk-123456789-1121152017-01-18T03:03:42Z Analysis of 400 kV pulse generator operation Nikulin, E.S. Belov, A.S. Frolov, O.T. Nechaeva, L.P. Turbabin, A.V. Zubets, V.N. Теория и техника ускорения частиц The injector provides linac by 400 keV protons with energy stability ±0.1%, pulsed ion current - up to 100 mA, 50 Hz pulse repetition rate (PRR) with 200 μs duration. The results of the high-voltage pulse generator operation analysis which have been done with the aim of pulse repetition rate increasing up to 100 Hz are given. Special attention is paid to operation of the multi-cascade capacitance-diode discriminator with inductances. Інжектор постачає лінійний прискорювач протонами з енергією 400 кеВ, стабільністю енергії ±0.1%, тривалістю імпульсів 200 мкс і частотою повторення 50 Гц. Приводяться результати аналізу роботи генератора високовольтних імпульсів, проведеного з метою підвищення частоти проходження імпульсів до 100 Гц. Особлива увага приділена роботі багатокаскадного ємкістно-діодного дискримінатора з індуктивностями. Инжектор снабжает линейный ускоритель протонами с энергией 400 кэВ, стабильностью энергии ±0.1%, длительностью импульсов 200 мкс и частотой повторения 50 Гц. Приводятся результаты анализа работы генератора высоковольтных импульсов, проведённого с целью повышения частоты следования импульсов до 100 Гц. Особое внимание уделено работе многокаскадного ёмкостно-диодного дискриминатора с индуктивностями. 2015 Article Analysis of 400 kV pulse generator operation / E.S. Nikulin, A.S. Belov, O.T. Frolov, L.P. Nechaeva, A.V. Turbabin, V.N. Zubets // Вопросы атомной науки и техники. — 2015. — № 3. — С. 123-126. — Бібліогр.: 6 назв. — англ. 1562-6016 PACS: 29.17.+w http://dspace.nbuv.gov.ua/handle/123456789/112115 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Теория и техника ускорения частиц Теория и техника ускорения частиц |
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Теория и техника ускорения частиц Теория и техника ускорения частиц Nikulin, E.S. Belov, A.S. Frolov, O.T. Nechaeva, L.P. Turbabin, A.V. Zubets, V.N. Analysis of 400 kV pulse generator operation Вопросы атомной науки и техники |
| description |
The injector provides linac by 400 keV protons with energy stability ±0.1%, pulsed ion current - up to 100 mA, 50 Hz pulse repetition rate (PRR) with 200 μs duration. The results of the high-voltage pulse generator operation analysis which have been done with the aim of pulse repetition rate increasing up to 100 Hz are given. Special attention is paid to operation of the multi-cascade capacitance-diode discriminator with inductances. |
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Article |
| author |
Nikulin, E.S. Belov, A.S. Frolov, O.T. Nechaeva, L.P. Turbabin, A.V. Zubets, V.N. |
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Nikulin, E.S. Belov, A.S. Frolov, O.T. Nechaeva, L.P. Turbabin, A.V. Zubets, V.N. |
| author_sort |
Nikulin, E.S. |
| title |
Analysis of 400 kV pulse generator operation |
| title_short |
Analysis of 400 kV pulse generator operation |
| title_full |
Analysis of 400 kV pulse generator operation |
| title_fullStr |
Analysis of 400 kV pulse generator operation |
| title_full_unstemmed |
Analysis of 400 kV pulse generator operation |
| title_sort |
analysis of 400 kv pulse generator operation |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Теория и техника ускорения частиц |
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http://dspace.nbuv.gov.ua/handle/123456789/112115 |
| citation_txt |
Analysis of 400 kV pulse generator operation / E.S. Nikulin, A.S. Belov, O.T. Frolov, L.P. Nechaeva, A.V. Turbabin, V.N. Zubets // Вопросы атомной науки и техники. — 2015. — № 3. — С. 123-126. — Бібліогр.: 6 назв. — англ. |
| series |
Вопросы атомной науки и техники |
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2025-07-08T03:25:06Z |
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1837047594199547904 |
| fulltext |
THEORY AND TECHNICS OF PARTICLE ACCELERATION
ANALYSIS OF 400 kV PULSE GENERATOR OPERATION
E.S.Nikulin∗, A.S.Belov, O.T.Frolov, L.P.Nechaeva,
A.V.Turbabin, V.N.Zubets
Institute for Nuclear Research of RAS, 117312, Moscow, Russia
(Received February 16, 2015)
The injector provides linac by 400 keV protons with energy stability ±0.1%, pulsed ion current – up to 100 mA,
50 Hz pulse repetition rate (PRR) with 200 µs duration. The results of the high-voltage pulse generator operation
analysis which have been done with the aim of pulse repetition rate increasing up to 100 Hz are given. Special
attention is paid to operation of the multi-cascade capacitance-diode discriminator with inductances.
PACS: 29.17.+w
INTRODUCTION
The INR linac proton injector provides at the ac-
celerating tube exit a hydrogen ion beam with the
following parameters: ion energy 400 keV ; energy
(pulse amplitude of accelerating voltage) stability
±0.1%; pulse top duration 200 µs, pulse repetition
rate 50 Hz; pulsed ion current 100 mA; normalized
transverse emittance 0.15 π cm · mrad for 90% of
beam current. PRR of the injector has been doubling
with goal of linac average beam current increasing [1].
The abbreviations made in the text:
HVPG - high-voltage pulse generator;
PRR - pulse repetition rate;
HV - high voltage;
MD - multi-cascade capacitance-diode
discriminator with inductances;
PTSCS - pulse top slope compensation system;
PFN - pulse forming network;
PT-400 - 400 kV pulse transformer.
Currently, a project of increasing of proton
linac average beam current is realized now by
PRR doubling [2]. This requires a correspond-
ing increasing of the proton injector PRR. How-
ever, tests conducted earlier [3] have shown that
pulse shape of the accelerating voltage produced
by the high-voltage pulse generator (HVPG)
at 100 Hz PRR has been distorted (Fig.1).
Fig.1. Oscillogram of the HVPG pulse at 100 Hz
PRR (the pulse with smaller amplitude is the top of
the HV pulse on a larger scale)
It is seen that the high voltage (HV) value change in
last forty microseconds of pulse duration is approxi-
mately 3% of the total pulse amplitude.
Fig.2. The proton injector HVPG electrical circuit
∗Corresponding author E-mail address: nikulin@inr.ru
ISSN 1562-6016. PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY, 2015, N3(97).
Series: Nuclear Physics Investigations (64), p.123-126.
123
This is unacceptable because the specified voltage
change during pulse for the proton injector is ±0.1%.
Besides achieving a desired shape of HV pulse at
100 Hz PRR we have revealed two additional prob-
lems to be solved: first - instability of pulse amplitude
and shape, associated with presence of a second 50 Hz
series of pulses (”doubling of pulses”) and second -
overheating of the HVPG individual components and
elements. This article contains, basically, the infor-
mation relating to achievement of desired HV pulse
shape. The HVPG circuit diagram is shown in Fig.2.
The HVPG consists of: the PT-400; the MD,
which stabilizes amplitude of HV pulses; the submod-
ulator providing pulses with amplitude up to 20 kV
to the PT-400 primary winding and made on the
PFN basis. The HVPG structure also includes three-
phase 0. . . 380 V , 100 kV A auto transformer; step-up
380 V/22 kV , 100 kV A transformer; the stabiliza-
tion system of accelerating voltage which is intended
to compensate 50 Hz power supply slow changes and
the PTSCS system. HVPG voltage pulse is measured
using the precision capacitive voltage divider embed-
ded in the PT-400. Switching of sub-modulator volt-
age pulses is carried out with HV thyratrons.
HVPG voltage pulse is measured using the preci-
sion capacitive voltage divider embedded in the PT-
400. Switching of the sub-modulator voltage pulses
is carried out with high-voltage thyratrons.
The HVPG is developed in the 1970’s at the
D.V.Efremov Scientific Research Institute of Electro-
physical Apparatus (NIIEFA, St. Petersburg) [4].
The HVPG operates as follows: C4 storage capac-
itor of 11 µF is charged up to 12.5 kV by full-wave
doubler. C11 leading edge shaper storage capacitor of
2.5 µF is charged up to 6 kV by six phase rectifier.
The PFN capacitors are charged in a quasires-
onant way from C4 storage capacitor through 8 H
choke to a voltage of about 1.6 UC4 .
When T2 thyratron is opened then C11 capacitor
is discharged through D19, D20 diodes and L9, R9
buffer circuit to the PT-400 primary winding. As a
result, the forced charge of constructive capacitance
connected with the PT-400 secondary winding is oc-
curred and the pulse leading edge of 40 µs base du-
ration and of 400 kV amplitude is formed.
The trailing edge of pulse is formed by T1 thyra-
tron triggering. The charge which is stored in the
constructive capacitance of the injector equipment is
recurred in C11 capacity.
HV pulse voltage is applied to the accelerating
tube which has the capacitive-resistive (water) volt-
age divider (R11 and C13) as well as to the MD via
R12 resistor and C14 capacitor.
200 µs HV pulse top is formed during the PFN
discharge to the PT-400 primary winding through T3
thyratron, L10 choke and D21 diode assembly. Pa-
rameters of C5 . . . C10 capacitors (0.15 µF ), L2 . . . L7
inductivities (2.5 mH) and amount of the PFN cells
(6) are selected so as to provide the required 200 µs
pulse top duration.
The MD stabilizes HVPG pulse top as follows:
when HV pulse is supplied to the MD and provid-
ing that the PT-400 pulse voltage amplitude exceeds
C49 . . . C80 capacitors sum voltage, D31 . . . D62 diodes
are opened and C49 . . . C80 capacitors are connected
in series, giving the stable (as a first approximation)
400 kV total voltage. During the HV pulse top there
is a current in the MD. It is limited by inner HVPG
impedance and proportional to difference between the
PT-400 secondary winding open-circuit voltage and
the MD voltage. But: current passage charges the
capacitors. The MD voltage increasing is determined
during the pulse flattop by the relation:
UMD ∼
32∑
j=1
(IjT )/CMD, (1)
where j — the MD cascade number (amount of cas-
cades equals to 32), Ij – capacitor current in j-th cas-
cade, T — HV pulse flattop duration (T = 200 µs),
CMD – capacity of cascade capacitor (CMD =
0.5 µF ).
The MD voltage rise that has been occurred dur-
ing pulse flattop is compensated by the PTSCS which
represents decreasing sawtooth voltage generator [5].
The amplitude of sawtooth voltage is chosen for the
most complete MD voltage rise compensation.
L12 . . . L43 series-connected chokes are connected
in parallel to C49 . . . C80 capacitors during the pulse
top. Choke currents increase under influence of the
UCi pulse voltage, which value is determined by rela-
tion:
ICi = (UCi∆T )/LMD, (2)
where: ICi – current change in the ith MD choke
during the pulse, ∆T – pulse duration, LMD - choke
inductivity.
Between pulses MD state is changed:
- D31 . . . D62 diodes are closed, D63 . . . D94 diodes
are opened and serial connection of C49 . . . C80 ca-
pacitors during pulse top is switched into PFN type
circuit;
- an energy stored during pulse top in the MD
chokes and capacitors is recurred to C4 storage ca-
pacitor. Herewith some energy is lost, mainly in R7
resistor.
Reactive energy stored during the pulse top
in C49 . . . C80 capacitors and L12 . . . L43 chokes at
10. . . 100 Hz PRR does not have time to recur be-
tween pulses to C4 storage capacitance due to the MD
discharge time constant which is exceeding 100 ms.
So at the beginning of a new pulse there is a current
in the most part of the MD chokes. It is associated
with energy recuperation from previous pulses. As a
result, at higher PRR the chokes average current is
increased.
Advanced analysis of the HVPG circuit has been
performed with the software package Micro-Cap 9.0
[6]. It makes possible to receive information about
processes in the HVPG which is not available by
means of direct measurements when using the real
HV equipment.
124
In particular it has been found that voltage of
the MD capacitors is redistributed during a pulse:
voltage of C65 . . . C80 capacitors (”upper” MD ca-
pacitors) decreases relative to the middle MD capac-
itor voltage, while voltage of C49 . . . C64 capacitors
(”lower” MD capacitors) increases. C49 capacitor
voltage reaches 18 kV amplitude at 100 Hz PRR,
while C80 capacitor voltage is about 7 kV . I.e., the
non-uniformity of the capacitors voltage distribution
reaches a significant value. The MD element’s volt-
ages/currents non-uniform distribution leads to a re-
distribution of the MD total current between capaci-
tor and choke in each cascade so that the MD capac-
itors current decreases as we move from the ”upper”
cascades to the ”lower” ones during the pulse flattop.
This process can lead to failure of the MD normal op-
eration if ”lower” cascades capacitor current has been
vanished before the end of 200 µs pulse top duration.
After tuning of the Micro-Cap model at the 4-
core CPU, 3.8 GHz, 8 GB RAM personal computer
with 64-bit Win7 OS the standard account times are
as follows: the conventional operating mode release
schedule takes up to 30 minutes and the process of
obtaining of results (for example, a HV pulse wave-
form) when a single key circuit element parameter is
changed – up to 3 minutes.
A cascade capacitor voltage has been decreased
to the C4 capacitor voltage value if transition pro-
cesses are ending before next HV pulse begin-
ning. The example of simulation at 100 Hz PRR
with 7 H choke inductivity is shown in Fig.3.
Fig.3. Simulation results for HV pulse top (3a)
and for ”upper“ and ”lower“ MD capacitors current
shape (3b upper and lower curve, respectively)
From the HVPG simulation results for 100 Hz
PRR and 7 H choke inductivity it follows that at the
end of pulse flattop there is a ”decline” with a volt-
age difference of about 10 kV . This decline begins
at ≈ 160-th microsecond of the 200 µs pulse flattop
duration (Fig.3, a). At this moment the ”lower” ca-
pacitor current is vanished to zero. It means closure
of the corresponding ”direct” diode and failure of the
MD normal operation. That leads to appearance of
HVPG pulse flattop ”decline”. But we do not ob-
serve the HVPG pulse flat-top ”decline” (Fig.4, a) as
well as vanishing of the MD ”lower” capacitor cur-
rent (Fig.4, b) when increasing choke inductivity up
to 20 H.
In Fig.4 – similar curves for 20 H choke induc-
tivity (PTSCS system is ”OFF” in those simulation
variants).
We do not observe the HVPG pulse top ”decline”
(Fig.4, a) as well as vanishing of the MD ”lower” ca-
pacitor current (Fig.4, b) when increasing choke in-
ductivity up to 20 H.
The MD chokes were replaced by the new ones
(Fig.5) which have parameters as follows: L = 20 H;
operating voltage — 25 kV ; magnetic core – type
of PL40x45-120; core material – cold-rolled 3408
electro-technical steel of 0.3 mm thick; coil body ma-
terial – caprolon (PA6), the number of turns – 6000
for two coils (one choke); copper wire – ⊘ 0.67 mm.
Fig.4. Simulation results with choke inductivity of
20 H
Fig.5. General view of two installed MD cascades
with the new chokes
The HVPG tests have been carried out at 100 Hz
PRR after installing the new MD chokes. The
HV pulse oscillograms are shown in Fig.6. From
the tests conducted it follows that the changes
have improved the stability during HV pulse flat-
top at 100 Hz PRR to a desired value of ±0.1%.
125
Fig.6. The HVPG pulse oscillograms at 100 Hz
PRR and the MD 20 H chokes (pulse with smaller
amplitude - HV pulse waveform on a larger scale,
the PTSCS system is ”ON“)
CONCLUSIONS
The model of the high-voltage pulse generator is de-
veloped. We have achieved satisfying accuracy and
reliability of simulation results. Simulation allows
us to get information about processes in the HVPG
which is difficult to obtain by direct measurements.
The analysis has identified a number of necessary
HVPG constructive changes. Its realization has al-
lowed us to get 100 Hz PRR operation mode with
200 µs pulse duration and energy instability less than
±0.1%.
ACKNOWLEDGEMENTS
Work is supported by PhEI, Obninsk, contract # 7-
2011/5722 under the auspices of Russian Federation
Ministry of Education and Science. We would like to
thank A.V. Feshenko and V.L. Serov for support and
help. The crucial assistance of A.V. Turbabin and
Yu.Ya. Gavrilyuk in construction of the equipment is
gratefully acknowledged.
References
1. A.N.Drugakov, A.V. Feschenko, A. I.Kvasha,
A.N.Naboka, V. L. Serov. Investigation of INR
DTL RF system operation of 100 Hz repeti-
tion rate // Proc. of RuPAC-2012, St. Peterburg,
Russia, September 24-28, p.296.
2. A.V. Feschenko, A. I.Kvasha, V. L. Serov. Some
peculiarities of the INR DTL RF system oper-
ation at doubling of average RF power level //
PAST. Series ”Nuclear Physics Investigations”.
2014, N3(91), p.32.
3. V. I. Derbilov, S.K. Esin, E. S.Nikulin,
O.T. Frolov, V. P.Yakushev. Average pro-
ton beam current increasing at the MMFL
injector // PAST. Series ”Nuclear Physics
Investigations”. 2004, N1(42), p.13.
4. Yu.V.Belov et al. // Proc. of VIII All-Union
Conference on charged particle accelerators,
Dubna, 1983, v.2, p.159 (in Russian).
5. V.N. Zubetz, V. I. Derbilov, S.K. Esin,
E. S.Nikulin, O.T. Frolov, V. P.Yakushev.
The stabilization system of 400...750 kV pulsed
accelerating voltage // PAST. Series ”Nuclear
Physics Investigations”. 1999, N3(34), p.52.
6. Micro-Cap 9.0, Electronic Circuit Analysis Pro-
gram. Spectrum Software. 1021, South Wolfe
Road, Sunnyvale, CA, 94086, www.spectrum-
soft.com.
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Èíæåêòîð ñíàáæàåò ëèíåéíûé óñêîðèòåëü ïðîòîíàìè ñ ýíåðãèåé 400 êýÂ, ñòàáèëüíîñòüþ ýíåðãèè
±0, 1%, äëèòåëüíîñòüþ èìïóëüñîâ 200 ìêñ è ÷àñòîòîé ïîâòîðåíèÿ 50 Ãö. Ïðèâîäÿòñÿ ðåçóëüòàòû àíà-
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òðèâàëiñòþ iìïóëüñiâ 200 ìêñ i ÷àñòîòîþ ïîâòîðåííÿ 50 Ãö. Ïðèâîäÿòüñÿ ðåçóëüòàòè àíàëiçó ðîáîòè
ãåíåðàòîðà âèñîêîâîëüòíèõ iìïóëüñiâ, ïðîâåäåíîãî ç ìåòîþ ïiäâèùåííÿ ÷àñòîòè ïðîõîäæåííÿ iìïóëü-
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126
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