JINR-IAP FEM oscillator with Bragg resonator
A FEM-oscillator with a reversed guide magnetic field and a Bragg resonator as a RF radiation source for collider applications was studied. The configuration with a step of the corrugation phase is proved to be advantageous. It possesses such features as a high efficiency, precise tunability of the...
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| Опубліковано в: : | Вопросы атомной науки и техники |
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| Дата: | 2001 |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2001
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| Назва журналу: | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| Цитувати: | JINR-IAP FEM oscillator with Bragg resonator / N.S. Ginzburg, A.V. Elzhov, A.K. Kaminsky, V.I. Kazacha, E.A. Perelstein, N.Yu. Peskov, S.N. Sedykh, A.P. Sergeev, A.S. Sergeev // Вопросы атомной науки и техники. — 2001. — № 5. — С. 60-62. — Бібліогр.: 7 назв. — англ. |
Репозитарії
Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859991613774757888 |
|---|---|
| author | Ginzburg, N.S. Elzhov, A.V. Kaminsky, A.K. Kazacha, V.I. Perelstein, E.A. Peskov, N.Yu. Sedykh, S.N. Sergeev, A.P. Sergeev, A.S. |
| author_facet | Ginzburg, N.S. Elzhov, A.V. Kaminsky, A.K. Kazacha, V.I. Perelstein, E.A. Peskov, N.Yu. Sedykh, S.N. Sergeev, A.P. Sergeev, A.S. |
| citation_txt | JINR-IAP FEM oscillator with Bragg resonator / N.S. Ginzburg, A.V. Elzhov, A.K. Kaminsky, V.I. Kazacha, E.A. Perelstein, N.Yu. Peskov, S.N. Sedykh, A.P. Sergeev, A.S. Sergeev // Вопросы атомной науки и техники. — 2001. — № 5. — С. 60-62. — Бібліогр.: 7 назв. — англ. |
| collection | DSpace DC |
| container_title | Вопросы атомной науки и техники |
| description | A FEM-oscillator with a reversed guide magnetic field and a Bragg resonator as a RF radiation source for collider applications was studied. The configuration with a step of the corrugation phase is proved to be advantageous. It possesses such features as a high efficiency, precise tunability of the operating frequency and a narrow spectral band. It is demonstrated experimentally that such an oscillator is capable of operating at frequencies of ~30 GHz in single-mode regime with the frequency tuning in interval up to 6%. Frequency and spectrum measurements have been performed with precision of ~0.1%.
|
| first_indexed | 2025-12-07T16:31:47Z |
| format | Article |
| fulltext |
JINR-IAP FEM OSCILLATOR WITH BRAGG RESONATOR
N.S. Ginzburg1, A.V. Elzhov2, A.K. Kaminsky2, V.I. Kazacha2, E.A. Perelstein2,
N.Yu. Peskov1, S.N. Sedykh2, A.P. Sergeev2, A.S. Sergeev1
1 RAS Institute of Applied Physics, Nizhny Novgorod, Russia
2 Joint Institute of Nuclear Research, Dubna, Russia
E-mail: artel@sunse.jinr.ru
A FEM-oscillator with a reversed guide magnetic field and a Bragg resonator as a RF radiation source for collider
applications was studied. The configuration with a step of the corrugation phase is proved to be advantageous. It
possesses such features as a high efficiency, precise tunability of the operating frequency and a narrow spectral
band. It is demonstrated experimentally that such an oscillator is capable of operating at frequencies of ~30 GHz in
single-mode regime with the frequency tuning in interval up to 6%. Frequency and spectrum measurements have
been performed with precision of ~0.1%.
PACS numbers: 41.60.Cr, 52.75.Ms, 84.40.Ik, 84.40.Fe
1 INTRODUCTION
High-efficiency narrow-band free-electron lasers
(masers) (FEL, FEM) can be used for the application as
pulse microwave power sources suitable for testing the
high-gradient accelerating structures of linear colliders.
Recent investigations at JINR on this subject are orient-
ed at the frequencies of ~30 GHz which corresponds to
the frequency of the accelerating microwave field for
the CLIC collider [1].
2 FEATURES OF FEM-OSCILLATORS US-
ING DIFFERENT TYPES OF BRAGG RES-
ONATORS
Since mid-1990s theoretical and experimental inves-
tigations of the FEM-oscillators with the Bragg res-
onators and reversed guide magnetic field are carried
out at JINR in collaboration with RAS Institute of Ap-
plied Physics (N.Novgorod) [2, 3]. The distributed feed-
back in FEM is provided by Bragg reflectors – cylindri-
cal waveguide sections with periodically corrugated in-
ner surface.
Several schemes of the Bragg resonators under in-
vestigation are shown in Fig. 1. Initial experiments de-
voted to the traditional Bragg resonator with a smooth
tube between the reflectors (Fig. 1a) showed that it was
possible to obtain both the single-mode and multi-mode
regimes of generation in such FEM-oscillators at differ-
ent resonator Q-factor values in the steady-state mode of
operation. The applying of such a FEM-oscillator
scheme for supplying the high-gradient accelerating
structures is coupled with certain technical problems.
Particularly, it is difficult to provide fixing and precise
tuning of the FEM frequency [4]. To solve these prob-
lems we investigated a FEM scheme, where the feed-
back was provided by Bragg resonators with a phase
step of the mirror corrugation (Fig. 1b, c) [5, 6].
For a symmetrical resonator (Fig. 1b) with the corru-
gation phase shift equal to π there is the only high-quali-
ty oscillation in the reflection zone of the Bragg struc-
tures, located in the middle of this band (the central
mode). The Q-factors of other oscillations at the edges
of the reflection zone (so-called side modes) are consid-
erably lower than that of the central mode. Thus the
electrodynamic selection in a resonator with a corruga-
tion phase step results in the excitation of only the cen-
tral mode and occurring of the single-mode regime of
operation already at the linear stage of the process.
Fig. 1. The schemes of the Bragg resonators (on the
left): a) double-optical resonator with a section of
regular waveguide; b) symmetrical resonator with
corrugation phase step; c) asymmetrical resonator
with corrugation phase step. The reflection band
and location of the frequencies of the resonator
eigenmodes (on the right).
The equality of the microwave fluxes from the res-
onator in the forward and in the backward directions is a
drawback of the symmetrical Bragg scheme. To en-
hance the power radiated in the forward direction it is
profitable to use the non-symmetrical resonator configu-
ration (Fig. 1c). However in such a scheme the Q-fac-
tors of the side modes grow, so the oscillator can be eas-
ier excited at those parasitic oscillations. Optimizing the
corrugation depth and lengths of the Bragg reflectors we
obtained higher efficiency [7].
3 PRECISE FREQUENCY TUNING IN
FEM-OSCILLATOR
Besides the capability of providing the narrow-band
RF radiation at a fixed frequency, a FEM-oscillator with
a step in the corrugation phase also possesses the possi-
bility of precise tuning of the operating frequency. For
the corrugation phase shift between the Bragg reflectors
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 2001. №5.
Серия: Ядерно-физические исследования (39), с. 60-62.
60
equal to π the fundamental mode is positioned at the
middle of the Bragg reflection zone. If the phase shift is
varied from π to 2π (or to 0) the frequency of the funda-
mental mode drifts to the lower edge (or to the higher
edge) of the Bragg zone. It is important to note that only
one high-Q eigenmode exists inside the Bragg zone at
any value of phase shift (if the value of the phase shift
does not closely approach the limiting values 0 or 2π).
Therefore high selective properties of the resonator are
maintained in the major part of the resonator reflection
band. Its width is proportional to the wave coupling
coefficient of the Bragg structures [5]. As a result, in-
side this zone precise tuning of the oscillation frequency
in an FEM is possible after mechanically changing the
value of the phase shift between the Bragg structures.
The frequency tuning of a FEM oscillator was inves-
tigated by numerical simulations as well as in the exper-
iments [4] for three different values of the phase shift
between Bragg structures: π, π/2 and 3π/2. It was shown
that the measured values of the central frequency and
the frequency shift coincided, with an acceptable preci-
sion, with the simulation results. The experimentally ob-
tained spectral distributions were too broad due to a low
accuracy of the measurements at kW power level due to
RF breakdown in the RF detector setup. To prevent RF-
breakdown in the last series of the experiment the out-
put RF signals were attenuated along the waveguide,
which transmitted the radiation for a distance of ~ 30 m
into the measuring room.
The FEM oscillator with a Bragg resonator is experi-
mentally investigated at JINR using an induction linac
LIU-3000 (electron beam energy 0.8 MeV, current
200 A, pulse duration 350 ns).
A schematic overview of the experimental setup is
presented in Fig. 2. The electron beam was injected
from the linac (1) with a repetition rate of 0.5 Hz into
the FEM oscillator (2) immersed in a solenoid. A wig-
gler with a period of 6 cm producing the transverse hel-
ical magnetic field was used to pump oscillating velo-
city to the beam.
Fig. 2. Scheme of the experiment: 1) accelerator LIU-3000 as the electron beam injector; 2) FEM os-
cillator; 3) Rogowski coil; 4) isolator; 5) deflecting magnet; 6) calorimeter; 7) crystal detector of the
microwave power; 8) attenuator; 9) wavemeter with the precise tuning of the resonant frequency;
10) insertion ring; 11) master oscillator; 12) RF frequency mixer; 13) digital oscilloscope.
The Bragg resonator was composed of two wave-
guide sections of equal lengths of 170 up to 197 mm,
having a rectangular corrugation of period d = 5.64 mm
and depth a1 = 0.5 mm. This corrugation provided a se-
lective feedback at an operating frequency range near
30 GHz by coupling the operating H11-mode and the
backward E11-mode of a circular waveguide. Precise
tuning of the oscillation frequency in the FEM was per-
formed by inserting short sections of a smooth wavegui-
de between the reflectors. For an insertion ring (10) of
length l the value of the phase shift is Δφ = 2πl/d.
After the interaction region the beam was dumped
onto the waveguide under the influence of the transverse
magnetic field produced by the permanent magnet (5).
The beam current was measured by Rogowski coils (3)
at the FEM waveguide input and output. Measurements
of the time dependence of the microwave power were
carried out by calibrated semi-conductor crystalline de-
tectors (6).
Precise measurements of the radiation frequency and
spectrum were carried out after transportation (7) of the
radiation into a measuring room and after attenuation to
the milliwatt level. Two measurement techniques were
used: a narrow-band tunable band-pass waveguide filter
(9) and heterodyne mixing (11, 12).
The accuracy of the frequency measurement with the
tunable filter was about 0.1%. To obtain the radiation
spectrum using the filter consecutive measurements had
to be done by adjusting the resonant frequency of the
filter during a series of RF-pulses. In contrast, the het-
erodyne technique allowed measuring the spectrum of a
single RF-pulse. The accuracy of the heterodyne tech-
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 2001. №5.
Серия: Ядерно-физические исследования (39), с. 61-62.
61
nique was determined by the error in the master oscillat-
or frequency. So, combining both measurement tech-
niques, we can determine the absolute value of the oper-
ating FEM frequency with a precision of about 0.1%
and obtain a precise shape of a RF-pulse spectrum.
0 50 100 150 200 250 300
0,0
0,5
1,0
S
pe
ct
ra
l a
m
pl
itu
de
, a
.u
.
f - f
m.o.
, MHz
Fig. 3. The RF pulse spectrum obtained by the
heterodyne technique (fm.o. is the master oscillator
frequency).
The operating frequency and spectrum of the FEM
output radiation were measured for various lengths of
the insertion ring in the resonator. Figure 3 presents the
spectrum of the output heterodyne signal for a corruga-
tion phase shift Δφ = π. The FEM operating frequency
is measured to be 29.98 GHz in this case. It is in a good
agreement with the value measured using the resonant
filter. The spectral band was found to be about 30 MHz
(FWHM), i.e. close to the spectral resolution of the fil-
ter. This value corresponds to the approximation
Δf/f0 ≈ Q-1 where Q is the resonator quality factor which
is equal to about 103 in our case.
0,4 0,6 0,8 1,0 1,2 1,4 1,6 1,8
28,5
29,0
29,5
30,0
30,5
side mode
central mode
Fr
eq
ue
nc
y,
G
H
z
Corrugation phase shift, in π units
Fig. 4. Dependence of the frequencies of the FEM
oscillator modes on the value of the corrugation
phase shift between Bragg reflectors.
The dependence of the frequency of the “central”
mode on the phase shift between the reflectors is shown
in Fig. 4 (upper curve). The range of phase shift covers
most of the Bragg reflection zone of the resonator, so
the tuning range of about 6% has been achieved. The er-
rors shown in Fig. 4 were defined mainly by mechanical
tolerances in manufacturing and mounting the insertion
ring. They increase the uncertainty of the frequency set-
ting up to ~0.15%. The type of f(Δφ) dependence is
close to linear which is in a good agreement with previ-
ous simulations and preliminary experimental results
[4].
For phase shift values deviating significantly from π,
excitation of “side” eigenmodes of the resonator (i.e.
positioned just outside the Bragg reflection zone) is also
possible [7] and, indeed, was observed in some regimes
at the proper initial mismatches from synchronism (i.e.
proper wiggler and/or guide fields). The results of mea-
surement for the low-frequency side-mode are also pre-
sented in Fig. 4 (lower curve).
4 CONCLUSIONS
A possibility of creating a high-efficiency, precisely
tunable, narrow-band (δf⁄f ~ 0.1%) FEM-oscillator using
the reversed guide magnetic field and Bragg resonator
has been proved. It has been demonstrated experimen-
tally that an oscillator with the step of the corrugation
phase is capable of operating at frequencies of ~30 GHz
in single mode-regime with the frequency tuning in in-
terval up to 6%. Frequency and spectrum measurements
by the tunable band-pass waveguide filter and with the
heterodyne technique have been performed with preci-
sion of ~0.1%. The results on the precise frequency tun-
ing are in a good agreement with the previous simula-
tions and experiments.
This work is supported by grants №№ 00-02-17519,
00-02-17232, 01-02-06249 of Russian Foundation for
Basic Research and partially by INTAS grant
№ 97-32041.
REFERENCES
1. J.-P.Delahaye et al. CLIC, a 0.5 to 5 TeV e± Com-
pact Linear Collider // Proc. of EPAC’98, Stock-
holm, June 1998, p. 58-62.
2. A.K.Kaminsky, A.A.Kaminsky, S.N.Sedykh et al.
Efficiency Optimization of the JINR Narrow-Band
Millimeter Wavelength FEL-Oscillator // Proc. of
the Free Electron Lasers Conference'96. Eds.
G. Dattoly, A. Renieri. Elsevier Science B.V.,
1997, v. II, p. 81-82.
3. N.S.Ginzburg, A.K.Kaminsky, A.A.Kaminsky et al.
Experimental Observation of Mode Competition
and Single-Mode Operation in JINR-IAP Millime-
ter-Wave FEM Oscillator // Nuclear Instrum. and
Meth. 1998, v. A407, p. 167-169.
4. A.V.Elzhov, I.N.Ivanov, A.K.Kaminsky, et al.
JINR Activity in Microwave Sources for TeV
Range Linear Colliders. // Problems of Atomic Sci-
ence and Technology. Issue: Nuclear-Physics Re-
search (36). 2000, № 2, p. 103-106.
5. V.L.Bratman, G.G.Denisov, N.S.Ginzburg, M.I.Pe-
telin. FEL’s with Bragg Reflection Resonators. Cy-
clotron Autoresonance Masers Versus Ubitrons //
IEEE J. of Quant. Electr. 1983, v. QE-19, № 3,
p. 282.
6. A.V.Elzhov, N.S.Ginzburg, I.N.Ivanov et al. Re-
cent Experiments on Free-Electron Maser for Two-
Beam Accelerators // Proc. of HEACC’98, Dubna,
September 1998, p. 160-162.
7. N.S.Ginzburg, A.A.Kaminsky, A.K.Kaminsky et al.
High-Efficiency Single Mode FEM-Oscillator
Based on a Bragg Resonator with Step of Phase of
62
Corrugation // Phys. Rev. Lett. 2000, v. 84, p. 3574-3577.
ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 2001. №5.
Серия: Ядерно-физические исследования (39), с. 63-62.
63
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| id | nasplib_isofts_kiev_ua-123456789-78983 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-12-07T16:31:47Z |
| publishDate | 2001 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Ginzburg, N.S. Elzhov, A.V. Kaminsky, A.K. Kazacha, V.I. Perelstein, E.A. Peskov, N.Yu. Sedykh, S.N. Sergeev, A.P. Sergeev, A.S. 2015-03-24T15:53:52Z 2015-03-24T15:53:52Z 2001 JINR-IAP FEM oscillator with Bragg resonator / N.S. Ginzburg, A.V. Elzhov, A.K. Kaminsky, V.I. Kazacha, E.A. Perelstein, N.Yu. Peskov, S.N. Sedykh, A.P. Sergeev, A.S. Sergeev // Вопросы атомной науки и техники. — 2001. — № 5. — С. 60-62. — Бібліогр.: 7 назв. — англ. 1562-6016 PACS numbers: 41.60.Cr, 52.75.Ms, 84.40.Ik, 84.40.Fe https://nasplib.isofts.kiev.ua/handle/123456789/78983 A FEM-oscillator with a reversed guide magnetic field and a Bragg resonator as a RF radiation source for collider applications was studied. The configuration with a step of the corrugation phase is proved to be advantageous. It possesses such features as a high efficiency, precise tunability of the operating frequency and a narrow spectral band. It is demonstrated experimentally that such an oscillator is capable of operating at frequencies of ~30 GHz in single-mode regime with the frequency tuning in interval up to 6%. Frequency and spectrum measurements have been performed with precision of ~0.1%. This work is supported by grants №№ 00-02-17519, 00-02-17232, 01-02-06249 of Russian Foundation for Basic Research and partially by INTAS grant № 97-32041. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники JINR-IAP FEM oscillator with Bragg resonator МСЭ-генератор с брэгговским резонатором в ОИЯИ-ИПФ Article published earlier |
| spellingShingle | JINR-IAP FEM oscillator with Bragg resonator Ginzburg, N.S. Elzhov, A.V. Kaminsky, A.K. Kazacha, V.I. Perelstein, E.A. Peskov, N.Yu. Sedykh, S.N. Sergeev, A.P. Sergeev, A.S. |
| title | JINR-IAP FEM oscillator with Bragg resonator |
| title_alt | МСЭ-генератор с брэгговским резонатором в ОИЯИ-ИПФ |
| title_full | JINR-IAP FEM oscillator with Bragg resonator |
| title_fullStr | JINR-IAP FEM oscillator with Bragg resonator |
| title_full_unstemmed | JINR-IAP FEM oscillator with Bragg resonator |
| title_short | JINR-IAP FEM oscillator with Bragg resonator |
| title_sort | jinr-iap fem oscillator with bragg resonator |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/78983 |
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