TRIUMF cyclotron RF system reliability enhancement
This paper presents recent RF system improvements related to the cyclotron resonators, RF amplifiers, and transmission lines. Although the program is not complete, the downtime due to rf sparking has already been reduced by a factor of 5.
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| Дата: | 2004 |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2004
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| Назва видання: | Вопросы атомной науки и техники |
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| Назва журналу: | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| Цитувати: | TRIUMF cyclotron RF system reliability enhancement / Yu. Bylinsky, S. Calic, G. Dutto, K. Fong, R. Poirier // Вопросы атомной науки и техники. — 2004. — № 1. — С. 69-70. — Бібліогр.: 3 назв. — англ. |
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irk-123456789-787002015-03-21T03:01:37Z TRIUMF cyclotron RF system reliability enhancement Bylinsky, Yu. Calic, S. Dutto, G. Fong, K. Poirier, R. Элементы ускорителей This paper presents recent RF system improvements related to the cyclotron resonators, RF amplifiers, and transmission lines. Although the program is not complete, the downtime due to rf sparking has already been reduced by a factor of 5. Обсуждаются усовершенствования ВЧ-системы: резонаторов циклотрона, ВЧ-генераторов, питающего волновода. Часть работ к настоящему времени завершена, что привело к уменьшению простоев из-за ВЧ- пробоев в 5 раз. Обговорюються удосконалення ВЧ-системи: резонаторів циклотрона, ВЧ-генераторів, що живить хвилевід. Частина робіт вже виконана, що дало зменшення простоїв через ВЧ-пробої у 5 разів. 2004 Article TRIUMF cyclotron RF system reliability enhancement / Yu. Bylinsky, S. Calic, G. Dutto, K. Fong, R. Poirier // Вопросы атомной науки и техники. — 2004. — № 1. — С. 69-70. — Бібліогр.: 3 назв. — англ. 1562-6016 PACS: 29.17+w http://dspace.nbuv.gov.ua/handle/123456789/78700 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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English |
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Элементы ускорителей Элементы ускорителей |
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Элементы ускорителей Элементы ускорителей Bylinsky, Yu. Calic, S. Dutto, G. Fong, K. Poirier, R. TRIUMF cyclotron RF system reliability enhancement Вопросы атомной науки и техники |
| description |
This paper presents recent RF system improvements related to the cyclotron resonators, RF amplifiers, and transmission lines. Although the program is not complete, the downtime due to rf sparking has already been reduced by a
factor of 5. |
| format |
Article |
| author |
Bylinsky, Yu. Calic, S. Dutto, G. Fong, K. Poirier, R. |
| author_facet |
Bylinsky, Yu. Calic, S. Dutto, G. Fong, K. Poirier, R. |
| author_sort |
Bylinsky, Yu. |
| title |
TRIUMF cyclotron RF system reliability enhancement |
| title_short |
TRIUMF cyclotron RF system reliability enhancement |
| title_full |
TRIUMF cyclotron RF system reliability enhancement |
| title_fullStr |
TRIUMF cyclotron RF system reliability enhancement |
| title_full_unstemmed |
TRIUMF cyclotron RF system reliability enhancement |
| title_sort |
triumf cyclotron rf system reliability enhancement |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2004 |
| topic_facet |
Элементы ускорителей |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/78700 |
| citation_txt |
TRIUMF cyclotron RF system reliability enhancement / Yu. Bylinsky, S. Calic, G. Dutto, K. Fong, R. Poirier // Вопросы атомной науки и техники. — 2004. — № 1. — С. 69-70. — Бібліогр.: 3 назв. — англ. |
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Вопросы атомной науки и техники |
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2025-07-06T02:46:15Z |
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2025-07-06T02:46:15Z |
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| fulltext |
TRIUMF CYCLOTRON RF SYSTEM RELIABILITY ENHANCEMENT
Yu. Bylinsky, S. Calic, G. Dutto, K. Fong, R. Poirier
TRIUMF, 4004 Wesbrook Mall, Vancouver, V6T 2A3, Canada;
E-mail: bylinsky@triumf.ca
This paper presents recent RF system improvements related to the cyclotron resonators, RF amplifiers, and trans-
mission lines. Although the program is not complete, the downtime due to rf sparking has already been reduced by a
factor of 5.
PACS: 29.17+w
1. INTRODUCTION
The TRIUMF cyclotron [1] is powered by a
23.06 MHz, 2 MW multistage amplifier. The final stage
is based on 8 EIMAC 4CW250000B tubes arranged in 4
power amplifiers (PA) running in parallel. The output
power is obtained through 3 combiners. There is another
accelerating cavity [2] operating at the 4th harmonic of
fundamental frequency that boosts the energy gain per
turn at the outer radii. The rf system causes two types of
downtime, due to rf sparking in the cavity and hardware
failures. Considerable effort was devoted to improve
equipment reliability and to reduce sparking.
2. HARDWARE SERVICING AND UPGRADE
The cyclotron operation does not leave much time
for detailed tests, troubleshooting, and upgrades of the
RF system. Basically, the system is available for service
for about 2 months a year.
In the past we experienced a few failures due to wa-
ter leaks in different locations, for example in the trans-
mission line section containing water-cooled capacitors.
In some cases the problem was traced to the aggressive
behavior of the low conductivity water with respect to
copper components. Solutions were applied: gold plat-
ing of rf contacts exposed to water; an introduction of
electrochemically active (zinc) dummy electrodes and
improved water connections. We have changed the de-
sign for all 3 capacitor stations in the matching section.
The new modular approach allows fast access to the ca-
pacitors for visual inspection and high voltage tests.
Another major activity in the rf refurbishing pro-
gram was related to the redesign of 3 powerful (up to
1 MW) combiners. The original units required a sub-
stantial effort to suppress parasitic oscillations, and
were difficult to maintain and adjust. Two new combin-
ers were fabricated and commissioned at full power.
The third is scheduled for installation this autumn.
A substantial effort was dedicated to a 500 kW resis-
tive load development. This is an essential tool for high
power testing of rf combiners and PA tuning and trou-
bleshooting. The load was commissioned in 2002 at full
power. Next year we plan to install an rf switch at the
output of the final combiner. This will allow a prompt
switch from the cyclotron resonator to the dummy load
for diagnostic purposes and eventually will permit 2 PA
operation in emergency situations, while 2 others can be
serviced. The device is being commissioned.
The output circuit of the Intermediate Power Ampli-
fier (IPA) was recently equipped with two directional
couplers and a 100 kW resistive load that provides easy
IPA tuning and matching to the following RF power
splitter, simplifying system troubleshooting.
So far, power metering between amplifier stages, as
well as in the rf splitter and in the combiner branches,
has been performed manually. This summer an automat-
ic data acquisition system was developed. In addition to
monitoring the power balance, it will feature a watch-
dog function to prevent operation under high reverse
power conditions in any section of the transmission
lines between PA’s and combiners. To improve trou-
bleshooting efficiency, we have also built a first event
detector system. It receives rf signals from as many as
24 voltage pickups and resolves which one drops out
first, in the case of sparking. This allows us to localize a
hardware failure in the rf chain from the frequency syn-
thesizer to the cyclotron cavity, and to log it for a post-
mortem analysis. The system resolution between two
subsequent signals is 0.1 µs.
The original copper chore pads installed in the cy-
clotron tank to dampen the mechanical vibrations of the
bellows in the resonator cooling circuit gave trouble on
at least 3 recent occasions. Typically, they cause an rf
arc, punching a hole in the stainless steel bellow. Res-
onator panel removal from the tank was required to fix
the leak, with considerable time and effort. We are in
the middle of a program to replace copper pads with
fiberglass ones. The total number of locations is about
160. The work will progress gradually over a few shut-
downs.
3. REDUCTION OF SPARKING EVENTS
Operational rf gradients in the rf cavity do not nor-
mally ignite vacuum breakdowns. However, theoretical
studies and model measurements [3] show, that in the
cyclotron vacuum chamber there are parasitic resonant
modes other than the fundamental. Some oscillate at fre-
quencies relatively close to the operational mode and at
voltages that could enhance multipactoring events. The
TM310 and TM410 modes are the closest ones. Rf field
propagation in the beam gap was found to be associated
mostly with these modes. Multipactoring in the cy-
clotron was observed indirectly from the load of the
main rf field and the vacuum deterioration connected to
the leakage. Evidence of secondary electron emission
discharge could also be observed from discolorations on
the resonator panels. Some areas are particularly vulner-
able to multipactoring. Therefore a lot of effort was put
into leakage field measurement and adjustment. The
leakage field amplitude is measured with 36 capacitive
___________________________________________________________
PROBLEMS OF ATOMIC SIENCE AND TECHNOLOGY. 2004. № 1.
Series: Nuclear Physics Investigations (42), p.69-70.
69
probes, installed on the resonator panels. So the leakage
field level can be adjusted and minimized by varying
the rf gap between ground arms and hot arms. After the
new refurbished control system for the ground arm tip
(GAT) position was installed, we performed extensive
tip tuning to reduce the leakage field. As a result, the
cyclotron downtime due to sparking was lowered by a
factor of 5. The weekly downtime graph is presented in
Figure.
0,00
5,00
10,00
15,00
20,00
25,00
15 17 19 21 23 25 27 29 31 33 35 37 40 42 44 46 48
Week #
RF
D
ow
nt
im
e,
h
ou
rs
Year 2002 weekly rf downtime graph. GAT system was upgraded on week 41
It was also noticed that sparking itself does not nec-
essarily have to cause significant interruptions as long
as the rf power is automatically turned off at every
spark. In the old system, within a few seconds delay, the
control system automatically started ramping up the
voltage. In total it took about 15 seconds before voltage
came back to the nominal value. However, by that time
the cyclotron thermal balance was lost because of the
substantial rf power removed from the structure by effi-
cient cooling. Temperature variations will affect the res-
onant frequency. In the operational mode, automatic
control of the resonant frequency is performed by vary-
ing the cooling water pressure. This system is very effi-
cient, but works within a very limited tuning range of
about 3 kHz. Thermal unbalance due to the above re-
covery time caused cyclotron frequency shifts above
10 kHz, requiring about 3 minutes for the system to
come back to the driven mode. Beam restart added 10-
20 seconds. So a total spark recovery used to cause 4-
5 minutes of machine downtime. The new procedure is
as follows. Spark detection is based on voltage drop
analysis. When the drop rate exceeds 10 kV/µs, the
event is recognized as a spark. At this point the rf drive
turns off for 300 ms to allow the ions migrate away
from the arc channel. The rf drive then instantly comes
back to its original value and automatic amplitude and
phase regulation are turned on. The only thing left is to
switch the system back to the driven mode, which is
done manually by the cyclotron operator. In such a sce-
nario the rf resonators return to operational conditions
right away and typically the spark recovery downtime
shrinks to 10...20 seconds.
REFERENCES
1. J.B. Warren // The TRIUMF Project, Proc. of 5th
Int. Cyclotron Conf. 1969, p.73-84.
2. G. Dutto et al. // Proc. of 16th Int. Conf. On Cy-
clotrons and their Applications, East Lansing,
USA. 2001, p.288-292.
3. D. Dohan, K. Fong, V. Pacak // Proc. of 11th Int.
Conf. On Cyclotrons and their Applications, Tokyo.
1987, p.345-348.
ПОВЫШЕНИЕ НАДЁЖНОСТИ ВЧ-СИСТЕМЫ ЦИКЛОТРОНА ТРИУМФ
Ю. Былинский, С. Калик, Р. Пуарье, К. Фонг
Обсуждаются усовершенствования ВЧ-системы: резонаторов циклотрона, ВЧ-генераторов, питающего
волновода. Часть работ к настоящему времени завершена, что привело к уменьшению простоев из-за ВЧ-
пробоев в 5 раз.
ПІДВИЩЕННЯ НАДІЙНОСТІ ВЧ-СИСТЕМИ ЦИКЛОТРОНА ТРІУМФ
Ю. Билінський, С. Калик, Р. Пуарьє, К. Фонг
Обговорюються удосконалення ВЧ-системи: резонаторів циклотрона, ВЧ-генераторів, що живить
хвилевід. Частина робіт вже виконана, що дало зменшення простоїв через ВЧ-пробої у 5 разів.
70
REFERENCES
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