Laser system of microwave picosecond pulse trains used for emission initiation in the photogun
The scheme of picosecond pulse train formation by scanning of a laser ray across the adjustable diaphragm by means of a microwave traveling-wave optical deflector is presented. After amplification and conversion these pulses can be used for photoemission obtaining in photoguns. Представлена схема...
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| Published in: | Вопросы атомной науки и техники |
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| Date: | 2006 |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2006
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| Cite this: | Laser system of microwave picosecond pulse trains used for emission initiation in the photogun / V.S. Dyomin, A.N. Dovbnya, L.V. Reprintsev, V.A. Shendrik // Вопросы атомной науки и техники. — 2006. — № 3. — С. 98-100. — Бібліогр.: 2 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859649242332659712 |
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| author | Dyomin, V.S. Dovbnya, A.N. Reprintsev, L.V. Shendrik, V.A. |
| author_facet | Dyomin, V.S. Dovbnya, A.N. Reprintsev, L.V. Shendrik, V.A. |
| citation_txt | Laser system of microwave picosecond pulse trains used for emission initiation in the photogun / V.S. Dyomin, A.N. Dovbnya, L.V. Reprintsev, V.A. Shendrik // Вопросы атомной науки и техники. — 2006. — № 3. — С. 98-100. — Бібліогр.: 2 назв. — англ. |
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| container_title | Вопросы атомной науки и техники |
| description | The scheme of picosecond pulse train formation by scanning of a laser ray across the adjustable diaphragm by
means of a microwave traveling-wave optical deflector is presented. After amplification and conversion these pulses
can be used for photoemission obtaining in photoguns.
Представлена схема формирования серии пикосекундных оптических импульсов путем сканирования лазерного луча с помощью СВЧ-дефлектора бегущей волны по регулируемой диафрагме. После усиления и преобразования эти импульсы можно использовать для получения эмиссии в фотопушках.
Приведена схема формування серії пікосекундних оптичних імпульсів шляхом сканування лазерного
променя за допомогою НВЧ-дефлектора бігучої хвилі по діафрагмі, що регулюється. Після підсилення і
перетворення ці імпульси можна використовувати для одержання емісії в фотогарматах.
|
| first_indexed | 2025-12-07T13:31:31Z |
| format | Article |
| fulltext |
LASER SYSTEM OF MICROWAVE PICOSECOND PULSE TRAINS
USED FOR EMISSION INITIATION IN THE PHOTOGUN
V.S. Dyomin, A.N. Dovbnya, L.V. Reprintsev, V.A. Shendrik
NSC KIPT, Kharkov, Ukraine
The scheme of picosecond pulse train formation by scanning of a laser ray across the adjustable diaphragm by
means of a microwave traveling-wave optical deflector is presented. After amplification and conversion these pulses
can be used for photoemission obtaining in photoguns.
PACS: 29.27 Fh,41.85.Qg
As a rule, to form trains of optical picosecond puls-
es (OPP) designed for obtaining a photoemission in mi-
crowave guns, one uses the method with passive mode
locking (PML), the block-diagram of which is shown in
Fig.1,a, or the method with active mode locking (AML),
Fig.1,b. Both methods use the intercavity modulation of
laser radiation requiring an exact adjustment and a very
stable construction.
LPML Amp. FCH МP PG
LAML PC WFS Amp. FCH
RFO
PGМP
1:32 Кl
L
Кl1:16
RFO
WFS Amp.
500 Мc x 6 3000Мc
Fig. 1а
Fig. 1b
Fig. 1c
89,25 Мc 2856 Мc
х16178,5 МГц
2797 Мc
174.81 Мc
DS ОS DS PGFCH
Fig.1. Block-diagram of forming microwave trains of
optical picosecond pulses.
Fig.1,a - the method with passive mode locking (PML).
Fig.1,b - the method with active mode locking (AML).
Fig.1,c - the method of laser radiation deflection.
Designations: L - laser. LPML - laser with PML,
LAML - laser with AML, AMP - amplifier, FCH - fre-
quency converter into harmonics, MP - multiplexer, PG
- photogun, RFO - radio-frequency oscillator, Kl -
klystron, PC - pulse compressor, WFS - waveform
shaper, DS - deflector system, OS - optical system
In paper [1] the authors consider the method of
OPP formation being not inferior by parameters than
previous method, but more simple by design and con-
struction and more profitable economically. The block-
diagram of the method offered is presented in Fig.1,c.
As a master oscillator one can use either a pulsed laser,
as in the first case, or a continuous-beam laser, as in the
second case. The radiation from the laser is directed into
the deflector system (DS) consisting of deflectors with
vertical and horizontal deflection, after into the optical
system composed of two lenses and a disk (placed be-
tween them) having cut slit diaphragms, then again into
the analogous DS, after that the formed train of optical
pulses is amplified, is converted into the third harmonic
and directed onto the photocathode of the microwave
gun energized from the klystron. This scheme, similarly
to the previous one, is designed in order to separate the
16th klystron subharmonics and to synchronize its opera-
tion with a high-voltage radio-frequency oscillator from
which DS are energized.
The layout of the setup for forming OPP trains is
shown in Fig.2.
∼
π /2
∼
π /2
View B-B
АААА
B
B
1 2 3 4 5 6 7 8 9
10
View A-A
Fig.2. Setup for forming OPP by the deflection method.
1 - laser; 2, 6 - deflector systems; 3, 5 - lenses; 4 - disk
with radial slit diaphragms; 7 - amplifier; 8 - convert-
er; 9 - microwave photogun; light trap
This layout shows also the laser and the DS in more
detail. A circular laser beam scanning is reached as a re-
sult of applying the driving sinusoidal electric voltage,
being phase-shifted by π/2 as compared to the voltage at
the first deflector. At the DS output there is formed a
laser light beam, deflected from the axis by an angle α
defl, which rotates about the cone. By means of the lens 3
the rotating laser beam is collimated and focused in the
plane B-B. In this plane placed is the metallic disc 4 in
which radial slit diaphragms and hole in the middle are
cut. The hole is used to pass a nondeflected laser beam
into the light trap 10. During rotation of the focused
laser beam over the slit diaphragms behind the latter a
spatially- separated OPP train is formed that is convert-
ed, by the lens 5, analogous to the lens 3, and by the DS
6, analogous to the DS 2, into the light beam being
collinear with the axis of the laser 1. Then this light
beam is amplified by amplifier the 7, is converted into
the 3,d harmonic and directed onto the microwave pho-
tocathode of the gun 9.
Basic parameters of the optical pulse train include:
a pulse frequency, as well as, duration and energy of a
pulse in the train. It is obvious, that the frequency of mi-
crowave pulses ƒmw is determined by the frequency of
deflector system scanning and by a number p of the slit
diaphragms on the circle. To provide a given frequency
of the train ƒmw a necessary number of radial holes is
determined by the formula of [1]:
p = ƒmw/ƒscan , (1)
where ƒscan. is the frequency of circular scanning of the
deflector system.
____________________________________________________________
PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2006. № 3.
Series: Nuclear Physics Investigations (47), p.98-100.98
A peculiarity of work [1], as well as, of all the stan-
dard schemes of OPP formation consists in that the radi-
ation of the master optical generator is either modulated,
or scanned at a frequency ƒscan.= ƒmw/p, where generally
p>10, and then, after amplification and multiplication of
light pulses with the help of the multiplexer by a factor
of p the frequency is increased up to ƒmw.
In the present work, due to the condition that the
laser beam scanning is performed at the klystron fre-
quency f =3 GHz, the layout of the setup is considerably
simpler. The block-diagram of the setup is shown in
Fig.3.
OSC TWD AMPS ω 3, ω 4 PGL1 L2D
Kl At ϕ
Fig.3. Block-diagram of the setup for forming picosec-
ond electron bunches in the electron linac. OSC - mas-
ter oscillator, TWD - travelling wave detector, L1, L2 -
telescope 1:2, D - adjustable diaphragm, AMPs - ampli-
fiers, ω3, ω4 - converter into 3d or 4th harmonics, PG -
photogun, K1 - klystron, At - attenuator, ϕ - phase
shifter
As a master oscillator OSC one can use a pulsed
Q-switched laser with an active element Nd:YLF or
Nd:YAG, being triggered with a repetition rate
ν = 10 Hz synchronously with a klystron and generating
optical pulses of a duration τ = 7 ns and an energy of
0.03 J at a wavelength λ = 1047 or 1064 nm. An optical
ray from the master oscillator comes into the traveling
wave deflector TWD, being energized via the attenuator
from the klystron. TWD performs the scanning of the
ray with a frequency 3 Ghz across the adjustable slit di-
aphragm. The lens L1 with a focal distance of ~30 cm
converts the light beams scanned by the deflector into
ones being parallel to the optical axis of the system and
being convergent into the plane of the diaphragm D.
The laser beam after passing the diaphragm D is colli-
mated by the lens L2 with a focal distance of 60 cm and
comes onto the amplifiers AMP and the frequency con-
verter ω3 or ω4, triplicating or multiplying by a factor of
4 the frequency of the master generator depending on
the cathode type of the microwave gun.
TWD is a multiple-prism system made on the base
of electrooptical crystals having a considerable elec-
trooptical effect. To such crystals pertaining are the
crystals of a tetragonal symmetry 42m: KH2PO4(KDP),
KD2PO4 (DKDP), NH4 H2PO4 (ADP), as well as, the
crystals of a trigonal symmetry 3m: LiNbO3 and
LiTaO3.
For pass-through deflectors the deflection angle α is
determined by the formula:
α = tgβ n3
rij E, (2)
where n is an index of crystal refraction, rij is an electro-
optical coefficient, E is an electric field strength, β is an
angle at electrooptical prism top.
Achievement of a large angle α in the pass-through
deflectors is hampered by the phenomenon of total in-
ternal reflection limiting tgβ by a unit. To exclude the
total internal reflection, the prisms are dipped into the
immersion, the refraction index of which is close to the
quantity n. Thus, the value of tgβ can reach 8-10 [2].
Optical and electrooptical parameters of crystals, usual-
ly applied in deflectors are given in Table.
Optical and electrooptical parameters of crystals ADP,
DKDP, KDP, LiNbO3 and LiTaO3
C
ry
st
al Electrooptical
constants
Index of
refraction
Ef
fe
ct
iv
e
el
ec
tro
op
tic
al
co
ns
ta
nt
s
r411012
m/v
r631012
m/v
r331012
m/v n0 ne
n3rij1
012m
/v
ADP 24.5 1.48 1.52 83
DKDP 26.4 1.47 1.51 90
KDP 8.6 1.47 1.51 32
LiNb03 35.8 2.176 2.18 371
LiTaO3 30.08 2.28 2.2 351
It is seen from the table that the large deflection an-
gle α can be obtained on the crystal of a trigonal sym-
metry having a high value of the effective electrooptical
constant n3rij. For crystals of the 42m symmetry n = no,
and for crystals of the 3m symmetry n = ne.
The phase shifter ϕ is used for shifting the phase of
microwave radiation taken from the klystron. The phase
is selected so that the maximum of microwave power be
coincident by the phase with the photocurrent pulse on
the photocathode of the gun. In this case, the photocath-
ode pulse, generated due to the reverse run of the laser
beam across the diaphragm will be in the opposite phase
with a maximum value of the microwave field and will
be not captured by this field. The light pulse duration τ
depends on the relation between the laser beam diameter
in the focal plane of the lens L1 and the width δ of the
slit diaphragm [1]
2
scanT d
N d
δτ
π
+= . (3)
Here N = αdefl/αdiverg, where αdefl and αdiverg, are the
deflection angle and the divergence angle of the laser
beam, respectively. If we select the TWD length
l = 40 cm and δ = 2d = 0.3 mm, taking into account that
F = 30 cm and αdiverg, = 0.0005 rad, and αdefl =2°, then
τ = 2.5 ps will be obtained. At a macropulse duration of
7 ns and a micropulse repetition rate of 3 GHz, behind
the diaphragm, 20 light micropulses of an energy ~10 µJ
every will follow. At the exit of the amplifier AMP,
comprising three amplification cascades, the micropulse
energy can be increased up to 1 mJ (Kampl. =100). After
____________________________________________________________
PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2006. № 3.
Series: Nuclear Physics Investigations (47), p.98-100.99
conversion of the optical radiation into 3d or 4th har-
monics one can obtain the light pulse energy on the pho-
tocathode of the order of 10 µJ that allows one to obtain
the electron bunch charge of ~0.25 ncoul at a quantum
efficiency of a copper photocathode η =10-4 on the
wavelength of 266 nm. The advantages of the scheme
offered for formation of optical pulses are:
1) possibility to form micropulses of any required du-
ration in the wide range from subpicosecond to tens of
subpicoseconds;
2) possibility of obtaining two or more pulses during
the microwave period due to the installation of several
diaphragms in the D plane.
REFERENCES
1. V.S. Dyomin, A.A. Chertkov. Formation of a train
of microwave optical picosecond pulses for obtain-
ing the photoemission in microwave guns. Proc. of
the Conference on Charged Particle Accelerators.
Protvino. 1994, v.3, p.103-111.
2 A.B. Van’kov, V.M. Volynkin, A.A. Chertkov.
Electrooptical deflectors of optical deflection for
the intense laser radiation // Izvestiya Akademii
Nauk SSSR, Ser. Phys. 1991, v.55, №2, p.253-259.
ЛАЗЕРНАЯ СИСТЕМА СВЧ-СЕРИЙ ПИКОСЕКУНДНЫХ ИМПУЛЬСОВ ДЛЯ ИНИЦИИРОВАНИЯ
ЭМИССИИ В ФОТОПУШКЕ
В.С. Демин, А.Н. Довбня, Л.В. Репринцев, В.А. Шендрик
Представлена схема формирования серии пикосекундных оптических импульсов путем сканирования ла-
зерного луча с помощью СВЧ-дефлектора бегущей волны по регулируемой диафрагме. После усиления и
преобразования эти импульсы можно использовать для получения эмиссии в фотопушках.
ЛАЗЕРНА СИСТЕМА НВЧ-СЕРІЙ ПІКОСЕКУНДНИХ ІМПУЛЬСІВ ДЛЯ ІНІЦІЮВАННЯ ЕМІСІЇ
В ФОТОГАРМАТІ
В.С. Дьомін, А.М. Довбня, Л.В. Репринцев, В.А. Шендрик
Приведена схема формування серії пікосекундних оптичних імпульсів шляхом сканування лазерного
променя за допомогою НВЧ-дефлектора бігучої хвилі по діафрагмі, що регулюється. Після підсилення і
перетворення ці імпульси можна використовувати для одержання емісії в фотогарматах.
100
В.С. Демин, А.Н. Довбня, Л.В. Репринцев, В.А. Шендрик
В.С. Дьомін, А.М. Довбня, Л.В. Репринцев, В.А. Шендрик
|
| id | nasplib_isofts_kiev_ua-123456789-79730 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-12-07T13:31:31Z |
| publishDate | 2006 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Dyomin, V.S. Dovbnya, A.N. Reprintsev, L.V. Shendrik, V.A. 2015-04-04T12:06:33Z 2015-04-04T12:06:33Z 2006 Laser system of microwave picosecond pulse trains used for emission initiation in the photogun / V.S. Dyomin, A.N. Dovbnya, L.V. Reprintsev, V.A. Shendrik // Вопросы атомной науки и техники. — 2006. — № 3. — С. 98-100. — Бібліогр.: 2 назв. — англ. 1562-6016 PACS: 29.27 Fh,41.85.Qg https://nasplib.isofts.kiev.ua/handle/123456789/79730 The scheme of picosecond pulse train formation by scanning of a laser ray across the adjustable diaphragm by means of a microwave traveling-wave optical deflector is presented. After amplification and conversion these pulses can be used for photoemission obtaining in photoguns. Представлена схема формирования серии пикосекундных оптических импульсов путем сканирования лазерного луча с помощью СВЧ-дефлектора бегущей волны по регулируемой диафрагме. После усиления и преобразования эти импульсы можно использовать для получения эмиссии в фотопушках. Приведена схема формування серії пікосекундних оптичних імпульсів шляхом сканування лазерного променя за допомогою НВЧ-дефлектора бігучої хвилі по діафрагмі, що регулюється. Після підсилення і перетворення ці імпульси можна використовувати для одержання емісії в фотогарматах. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Ускорители заряженных частиц Laser system of microwave picosecond pulse trains used for emission initiation in the photogun Лазерная система СВЧ-серий пикосекундных импульсов для инициирования эмиссии в фотопушке Лазерна система НВЧ-серій пікосекундних імпульсів для ініціювання емісії в фотогарматі Article published earlier |
| spellingShingle | Laser system of microwave picosecond pulse trains used for emission initiation in the photogun Dyomin, V.S. Dovbnya, A.N. Reprintsev, L.V. Shendrik, V.A. Ускорители заряженных частиц |
| title | Laser system of microwave picosecond pulse trains used for emission initiation in the photogun |
| title_alt | Лазерная система СВЧ-серий пикосекундных импульсов для инициирования эмиссии в фотопушке Лазерна система НВЧ-серій пікосекундних імпульсів для ініціювання емісії в фотогарматі |
| title_full | Laser system of microwave picosecond pulse trains used for emission initiation in the photogun |
| title_fullStr | Laser system of microwave picosecond pulse trains used for emission initiation in the photogun |
| title_full_unstemmed | Laser system of microwave picosecond pulse trains used for emission initiation in the photogun |
| title_short | Laser system of microwave picosecond pulse trains used for emission initiation in the photogun |
| title_sort | laser system of microwave picosecond pulse trains used for emission initiation in the photogun |
| topic | Ускорители заряженных частиц |
| topic_facet | Ускорители заряженных частиц |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/79730 |
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