High sensitivity calorimeter for measuring wakefields energy excited by a train of electron bunches
The special calorimeter for measuring total energy of HF-wakefields excited in plasma or dielectric by relativistic electron bunches has been elaborated. Simple by design calorimeter operates in the energy range from 0.02 J up to 780 J. Water is used as an absorbing material. For measuring irradiate...
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| Cite this: | High sensitivity calorimeter for measuring wakefields energy excited by a train of electron bunches / V.A. Kiselev, A.F. Linnik, N.I. Onishchenko, V.V. Uskov // Вопросы атомной науки и техники. — 2005. — № 2. — С. 232-234. — Бібліогр.: 10 назв. — англ. |
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nasplib_isofts_kiev_ua-123456789-798192025-02-23T18:16:15Z High sensitivity calorimeter for measuring wakefields energy excited by a train of electron bunches Калориметр високої чутливості для виміру енергії кільватерних полів, збуджуваних послідовністю електронних згустків Калориметр высокой чувствительности для измерения энергии кильватерных полей, возбуждаемых последовательностью электронных сгустков Kiselev, V.A. Linnik, A.F. Onishchenko, N.I. Uskov, V.V. Plasma diagnostics The special calorimeter for measuring total energy of HF-wakefields excited in plasma or dielectric by relativistic electron bunches has been elaborated. Simple by design calorimeter operates in the energy range from 0.02 J up to 780 J. Water is used as an absorbing material. For measuring irradiated water volume change the capacitive ferroceramic sensor was applied. Sensor sensitivity is 8.7 pF/J that two orders exceeds sensitivity of capacitor-sensor used in our experiments before. The calorimeter is not sensitive to nonuniformity of radiation field, and its response on HFradiation is high enough. Calorimeter design allows along with measuring radiation energy simultaneously controlling the current of bunches sequence. Розроблено спеціальний калориметр для виміру енергії НВЧ–кільватерних полів, збуджуваних в плазмі або діелектрику релятивістськими електронними згустками. Простий по конструкції калориметр працює в діапазоні енергій 0,02-780 Дж. Як поглинаючий матеріал використана вода. Зміна її об’єму вимірюється ємнісним сегнетокерамічним датчиком, чутливість якого складає 8,7 пФ/Дж, що на два порядки перевищує чутливість ємнісних датчиків, які використовувались раніше. Разработан специальный калориметр для измерения полной энергии СВЧ–кильватерных полей, возбуждаемых в плазме или диэлектрике релятивистскими электронными сгустками. Простой по конструкции калориметр работает в диапазоне энергий 0,02-780 Дж. В качестве поглощающего материала использована вода. Для измерения изменения ее объема применен емкостной сегнетокерамический датчик, чувствительность которого составляет 8,7 пФ/Дж, что на два порядка превышает чувствительность применявшихся ранее емкостных датчиков. This work was supported by grants CRDF UP2-2569- KH-04 and DFFD №02.07/325 2005 Article High sensitivity calorimeter for measuring wakefields energy excited by a train of electron bunches / V.A. Kiselev, A.F. Linnik, N.I. Onishchenko, V.V. Uskov // Вопросы атомной науки и техники. — 2005. — № 2. — С. 232-234. — Бібліогр.: 10 назв. — англ. 1562-6016 PACS: 41.75.Lx, 41.85.Ja, 41.60.Bq https://nasplib.isofts.kiev.ua/handle/123456789/79819 en Вопросы атомной науки и техники application/pdf Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Plasma diagnostics Plasma diagnostics |
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Plasma diagnostics Plasma diagnostics Kiselev, V.A. Linnik, A.F. Onishchenko, N.I. Uskov, V.V. High sensitivity calorimeter for measuring wakefields energy excited by a train of electron bunches Вопросы атомной науки и техники |
| description |
The special calorimeter for measuring total energy of HF-wakefields excited in plasma or dielectric by relativistic electron bunches has been elaborated. Simple by design calorimeter operates in the energy range from 0.02 J up to 780 J. Water is used as an absorbing material. For measuring irradiated water volume change the capacitive ferroceramic sensor was applied. Sensor sensitivity is 8.7 pF/J that two orders exceeds sensitivity of capacitor-sensor used in our experiments before. The calorimeter is not sensitive to nonuniformity of radiation field, and its response on HFradiation is high enough. Calorimeter design allows along with measuring radiation energy simultaneously controlling the current of bunches sequence. |
| format |
Article |
| author |
Kiselev, V.A. Linnik, A.F. Onishchenko, N.I. Uskov, V.V. |
| author_facet |
Kiselev, V.A. Linnik, A.F. Onishchenko, N.I. Uskov, V.V. |
| author_sort |
Kiselev, V.A. |
| title |
High sensitivity calorimeter for measuring wakefields energy excited by a train of electron bunches |
| title_short |
High sensitivity calorimeter for measuring wakefields energy excited by a train of electron bunches |
| title_full |
High sensitivity calorimeter for measuring wakefields energy excited by a train of electron bunches |
| title_fullStr |
High sensitivity calorimeter for measuring wakefields energy excited by a train of electron bunches |
| title_full_unstemmed |
High sensitivity calorimeter for measuring wakefields energy excited by a train of electron bunches |
| title_sort |
high sensitivity calorimeter for measuring wakefields energy excited by a train of electron bunches |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2005 |
| topic_facet |
Plasma diagnostics |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/79819 |
| citation_txt |
High sensitivity calorimeter for measuring wakefields energy excited by a train of electron bunches / V.A. Kiselev, A.F. Linnik, N.I. Onishchenko, V.V. Uskov // Вопросы атомной науки и техники. — 2005. — № 2. — С. 232-234. — Бібліогр.: 10 назв. — англ. |
| series |
Вопросы атомной науки и техники |
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2025-11-24T08:19:24Z |
| last_indexed |
2025-11-24T08:19:24Z |
| _version_ |
1849659085832585216 |
| fulltext |
HIGH SENSITIVITY CALORIMETER
FOR MEASURING WAKEFIELDS ENERGY EXCITED
BY A TRAIN OF ELECTRON BUNCHES
V.A. Kiselev, A.F. Linnik, N.I. Onishchenko, V.V. Uskov
NSC Kharkov Institute of Physics and Technology, Kharkov, Ukraine
The special calorimeter for measuring total energy of HF-wakefields excited in plasma or dielectric by relativistic
electron bunches has been elaborated. Simple by design calorimeter operates in the energy range from 0.02 J up to 780
J. Water is used as an absorbing material. For measuring irradiated water volume change the capacitive ferroceramic
sensor was applied. Sensor sensitivity is 8.7 pF/J that two orders exceeds sensitivity of capacitor-sensor used in our
experiments before. The calorimeter is not sensitive to nonuniformity of radiation field, and its response on HF-
radiation is high enough. Calorimeter design allows along with measuring radiation energy simultaneously controlling
the current of bunches sequence.
PACS: 41.75.Lx, 41.85.Ja, 41.60.Bq
1. INTRODUCTION
For measuring the total pulsed energy of HF-radiation
excited by a train of electron bunches in plasma or
dielectric structure [1-3] calorimeter is needed that could
work in a wide frequency band and a considerable range
of measured energies. Requirements to such calorimeter
become even more rigid at measuring a frequency
spectrum of radiation [4], because for this purpose
calorimeter sensitivity should be higher (0.01-0.03 J).
Besides the fast response of the calorimeter to change of
absorbed energy and simplicity of operation are desirable.
From our point of view all these requirements are fulfilled
by the calorimeter with capacitive ferroceramic sensor
that is represented in this work. Due to high permittivity
the ferroceramic sensor allows increasing essentially the
sensitivity of the calorimeter and at most simplifying its
design.
A lot of calorimeters described earlier [5-9] allow to
measure energy of HF-radiation in a range from several
mJ up to kJ over the frequency range from one GHz up to
several hundreds GHz. Most frequently used working
substance is a solid absorber (metal ceramics, resistive
textile, graphite plates) [5-7], and a measurand is the
increase of temperature that is measured, by thermo-
batteries, thermistors, wire-wound resistors. The shortages
of such calorimeters are their time delay and non-
isothermality. It is especially essential at large volumes of
working substance and non-uniformity of radiation fields
in various points of the calorimeter. Very likely these
shortages in the even greater measure are proper in flow
calorimeters [8] which working substance is water, as a
rule. In the work [9] a broadband HF-calorimeter of large
square (1200 cm2) is described which working substance
is ethanol (С2Н6О) and a measurand is increase of its
volume. The calorimeter is not sensitive to non-
uniformity of heating of ethanol. However it is intended
for measuring energy of a plane wave and is settled down
outside of the HF-oscillator.
In the work [10] the simple calorimeter for measuring
the total energy of pulsed and continuous HF-radiation is
described. Measured energy of HF-radiation is in the
range from 0.5 J up to 6 кJ. The calorimeter is placed in
the circular waveguide. The absorptance of energy of HF-
radiation in the range of 3-60 GHz is not worse of 0.9.
The calorimeter is not sensitive to nonuniformity of the
radiation field over volume of working substance, and its
response to HF-radiation is practically instantaneous. But
its shortage is rather low sensitivity ≈0,025 pF/J, that
makes difficult measuring, especially at low energy of
HF-radiation.
The idea of sensor sensitivity increasing concludes to
the enhancement of accuracy of volume change ΔV
measuring. For this goal the coaxial condenser with high
permittivity ε was used that provides perceptible its
capacity change at small water volume change.
2. CALORIMETER DESIGN
The design of the proposed calorimeter is similar to
that realized in [10] but it has a capacitive ferroceramic
sensor that is more sensitive and simpler in work. The
scheme of the calorimeter is pictured in Fig. 1.
Fig. 1. Scheme of calorimeter:
1-absorbing section, 2-reflecting cone, 3-connecting
pipe from stainless steel, 4-Faraday cap, 5-ebonite
flange, 6-glass branch tubes, 7-ferroceramic tube, 8-
piston for regulation of water level, 9-copper
conductor, 10-connecting dielectric tube, 11-copper
tube, 12-to device for capacity measuring
232 Problems of Atomic Science and Technology. Series: Plasma Physics (11). 2005. № 2. P. 234-234
The absorbing section 1 is a matched load. It represents
a cylinder of diameter 75 mm and length 250 mm with a
conic interior surface and a hole along the axis. Walls of
the absorbing section are manufactured from quartz glass
of thickness 1 mm. The section is filled by water. Its
volume is 606.5 сm3. For improving of HF-radiation
absorption in a wide frequency band, the metal cone 2
manufactured from titanium foil of thickness 50µ is
located inside absorbing section. Such foil is "transparent"
for relativistic electron beam.
Behind titanium foil a Faraday cap 3 is arranged. Such
placing allows simplifying researches of dielectric
wakefield generator, avoiding the problem of deflection
of relativistic electron beam on the walls of generator
encasement at measuring output HF-energy. The foil cone
is fastened on a segment of stainless steel tube 4 in which
there are holes for pumping of Faraday cap volume. It
serves as a thermal screen too.
Absorbing section and Faraday cap are fastened on
ebonite flange 5 through which two glass branch tubes 6
from the absorbing section are brought out. At the exit of
one of them measuring ferroceramic tube 7 is mounted.
Inside ferroceramic tube the non-insulated copper
conductor 9 of thickness 0.1 mm is extended, providing
contact to device for capacity measuring. Such
arrangement results in linearity of measuring. The second
glass branch tube is ended by an adjusting piston for
regulation of water level. From it also the wires of the
warmer placed inside the absorbing section are also
brought out. At breaks in-process, and also if fast
performance of repeated measuring is necessary the initial
level of water in the measuring tube is reestablished with
the help of the adjusting piston. Outlet of the calorimeter,
the measuring tube and the adjusting piston were located
for thermo-insulation in the foam plastic casing of
thickness 15 mm.
3. PRINCIPLE OF OPERATION
Measurand is the increase of volume of the water,
caused by a thermal expansion at HF-energy absorption.
The increase of water volume ΔV is equal:
ΔV=V0α0ΔT, (1)
where V0 is initial volume of water, α0 is coefficient of
volume expansion at initial temperature, ΔT is change of
temperature of water which is proportional to the value of
the absorbed energy ΔW:
ΔT=
ΔW
mc0
= ΔW
V 0 ρ0 c0
, (2)
where m is mass of water, ρ0 – a denseness and с0 –
specific heat of water at initial temperature. Substituting
value ΔT from (2) in (1), we shall obtain the expression
for the increase of water volume ΔV in dependence on
absorbed HF-energy ΔW:
ΔV=
α0 ΔW
ρ0c0
. (3)
The increase of water volume is proportional to absorbed
energy ΔW and also does not depend on initial volume of
water and distribution of the absorbed energy over water
volume. From (3) the ratio of change of water volume to the
absorbed energy is equal ΔV / ΔW ≈0,048 mm 3 /J.
For solving the main problem of measuring of the
increase of water volume the sensor was used which basic
element is ferroceramic tube with inner diameter
а=1,8mm and a working length l=11 mm was used. In
ferroceramic tube the increase of water volume
transforms in the increase of length of water column. The
tube from ferroceramic condenser KT-1 was taken with
admissible change of capacity at 20 in the temperature
interval -60 - +85° less than 10 % (group H10). The
conductive coating of interior surface of the condenser
was carefully etched.
The length of water column in ferroceramic tube was
determined by the value of the capacity formed by water
inside tube and the conductive coating on the outside of
tube. Change of capacity was determined from relation
ΔС=2πεε0Δl/ln(b/a) (4)
where Δl=ΔV/πа2/4 is change of length of water column
in the tube, b is outer diameter of the tube. As the
ferroelectric ceramics has large permittivity (in our case
permittivity ε ≈3100), capacitive sensitivity of the sensor
was ΔС/ Δl ≈ 620 pF/mm.
4. DIELECTRIC WAKEFIELD ENERGY
MEASUREMENTS
Calorimeter was designed so that it can be mounted
directly into dielectric waveguide to envelop the total
generated HF-energy. Energy sensitivity of the sensor at
using water as a working substance is ΔС/ΔW≈8,7 pF/J
that is 350 times higher than sensitivity of the usual
capacitive sensor proposed in [10.] Minimum registered
energy is determined by minimum measured change of
capacity. At accuracy of measuring of capacity by our
device ΔСmin =0.1 pF the minimum registered energy of
HF-radiation is Wmin≤0,02 J.
Permittivity of ferroelectric ceramics strongly depends
on temperature, therefore both good stabilization of initial
temperature of the calorimeter and its careful calibration
is necessary. Stabilization of initial temperature was
achieved by the continuous heating water preliminary
heated to the temperature above ambient temperature.
Needed heating should provide zero velocity of change of
water volume and therefore the velocity of change of
initial capacity of the sensor.
The maximum energy registered by the calorimeter is
proportional to the total length of ferroceramic tube. At
the length of the tube 11mm taken from ferroceramic
condenser KT-1 (maximum capacity at full filling by
water ~ 6800 pF) maximum measured energy makes
Wmax≈785 J. The increase of length of measuring tube
twice reduces in increase of maximum measured energy
233
up to 1,5 kJ. At absorption of such energy the temperature
of water in the calorimeter on the average increases on 0.6
0K that ensures the constancy of its specific heat of water,
coefficient of volume expansion, etc. The increase of
maximum measured energy due to increase of length of
the tube is not desirable because of increase of
hydrostatical pressure The upper limit of measured energy
can be increased considerably when having used a
measuring tube of greater diameter, though with
sensitivity decreasing.
Precise measuring capacity of ferroceramic sensor is a
complicated problem. Firstly, it is necessary to exclude
heating of water in the sensor during measuring. In our
case measuring of capacity was performed by multimeter
DT9208А at frequency 1МHz with amplitude of
oscillations 0.02 V in pulsed mode (τpulse = 1ms) that did
not lead to essential heating of water in sensor. Secondly,
measuring of capacity by measuring of its capacitive
resistance is correct under condition Rw<<(2πfС)-1 where
Rw is active resistance of water in sensor, f is frequency
on which measurement is being performed. In our case
the value (2πfС)-1 changes from 105 Ω (at Сmin=10 pF) up
to ≈150 Ω (at Сmax=6800 pF). If distilled water is used then
Rw is in limits 103 – 104 Ω that allows to use water at
measuring with a low level of energy. In other cases it is
necessary to use preliminary obtained calibration curve of
the absorbed energy determination from the measured
value of capacity or to reduce active resistance of the
sensor by adding in water of a small amount of copper
vitriol to make it conducting. In the third, it is necessary
to prevent formation water film on an interior surface
ferroceramic sensor by wiping with glycerine before
performance of measurements.
Calibration of the calorimeter was carried out both
with the help of magnetron oscillator with pulsed power
200 kW and with heater located inside the absorbing
section and having resistance 8 Ω. Both methods have
shown good agreement of the calculated and measured
values of absorbed energy
Calorimeter has been used for measuring energy of
wakefields excited in cylindrical dielectric waveguide
(length 70cm, inner and outer diameters 2.2 cm and 8.4 cm,
correspondingly, ε=2.1) by a sequence of relativistic
electron bunches, obtained at linear electron accelerator
"Almaz-2" with REB parameters: energy 4 MeV, pulsed
current 0.5 A, pulse duration 2 µs, modulation frequency
2805 MHz (so one pulse consists of 6⋅103 cylindrical
electron bunches of diameter 1cm and length 1.7cm),
repetitive frequency 3 Hz. Experimental results concludes
to measured wakefields energy 0.4 J excited by one pulse
of 4 J.
This work was supported by grants CRDF UP2-2569-
KH-04 and DFFD №02.07/325
REFERENCES
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V.V.Uskov // Instruments and Experimental
Techniques (in press).
КАЛОРИМЕТР ВЫСОКОЙ ЧУВСТВИТЕЛЬНОСТИ ДЛЯ ИЗМЕРЕНИЯ ЭНЕРГИИ КИЛЬВАТЕРНЫХ
ПОЛЕЙ, ВОЗБУЖДАЕМЫХ ПОСЛЕДОВАТЕЛЬНОСТЬЮ ЭЛЕКТРОННЫХ СГУСТКОВ
В.А. Киселев, А.Ф. Линник, H.И. Онищенко, В.В. Усков
Разработан специальный калориметр для измерения полной энергии СВЧ–кильватерных полей, возбуждаемых
в плазме или диэлектрике релятивистскими электронными сгустками. Простой по конструкции калориметр
работает в диапазоне энергий 0,02-780 Дж. В качестве поглощающего материала использована вода. Для
измерения изменения ее объема применен емкостной сегнетокерамический датчик, чувствительность которого
составляет 8,7 пФ/Дж, что на два порядка превышает чувствительность применявшихся ранее емкостных
датчиков.
КАЛОРИМЕТР ВИСОКОЇ ЧУТЛИВОСТІ ДЛЯ ВИМІРУ ЕНЕРГІЇ КІЛЬВАТЕРНИХ ПОЛІВ,
ЗБУДЖУВАНИХ ПОСЛІДОВНІСТЮ ЕЛЕКТРОННИХ ЗГУСТКІВ
В.О. Кисельов, А.Ф. Лінник, М.І. Онищенко, В.В. Усков
Розроблено спеціальний калориметр для виміру енергії НВЧ–кільватерних полів, збуджуваних в плазмі або
діелектрику релятивістськими електронними згустками. Простий по конструкції калориметр працює в діапазоні
енергій 0,02-780 Дж. Як поглинаючий матеріал використана вода. Зміна її об’єму вимірюється ємнісним
234
сегнетокерамічним датчиком, чутливість якого складає 8,7 пФ/Дж, що на два порядки перевищує чутливість
ємнісних датчиків, які використовувались раніше.
235
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