Microwave discharge as a source of light
We try to analyze the ways to optimize microwave discharges in a microwave light source. The problem here is that as the discharge starts glowing, electrodynamic properties of the plasma being the load for the microwave source change significantly. During this, the characteristics of the light radia...
Збережено в:
| Дата: | 2005 |
|---|---|
| Автори: | , , , |
| Формат: | Стаття |
| Мова: | English |
| Опубліковано: |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2005
|
| Назва видання: | Вопросы атомной науки и техники |
| Теми: | |
| Онлайн доступ: | http://dspace.nbuv.gov.ua/handle/123456789/79812 |
| Теги: |
Додати тег
Немає тегів, Будьте першим, хто поставить тег для цього запису!
|
| Назва журналу: | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| Цитувати: | Microwave discharge as a source of light / Yu.Ya. Brodsky, N.F. Kovalev, A.O. Perminov, S.P. Shlepnev // Вопросы атомной науки и техники. — 2005. — № 2. — С. 208-210. — Бібліогр.: 1 назв. — англ. |
Репозитарії
Digital Library of Periodicals of National Academy of Sciences of Ukraine| id |
irk-123456789-79812 |
|---|---|
| record_format |
dspace |
| spelling |
irk-123456789-798122015-04-05T03:02:05Z Microwave discharge as a source of light Brodsky, Yu.Ya. Kovalev, N.F. Perminov, A.O. Shlepnev, S.P. Low temperature plasma and plasma technologies We try to analyze the ways to optimize microwave discharges in a microwave light source. The problem here is that as the discharge starts glowing, electrodynamic properties of the plasma being the load for the microwave source change significantly. During this, the characteristics of the light radiation from the plasma and efficiency of using the microwave energy are far from optimal. We propose a way to solve this problem, which is based on creating a multiresonance electrodynamic system tuning automatically as the value of the plasma load changes, thus providing reasonably good coupling in all regimes of operation of the lamp. Проведено аналіз шляхів оптимізації узгодження мікрохвильового розряду в мікрохвильовому джерелі світла. Проблема зв'язана з тією обставиною, що при розвитку розряду характер навантаження міняється істотно. При цьому відбувається неузгодженість, і енергія не надходить у розряд. Ми пропонуємо шлях рішення цієї проблеми, заснований на використанні багатомодової електродинамічної системи, що автоматично стежить за зміною імпедансу навантаження. Проведен анализ путей оптимизации согласования микроволнового разряда в микроволновом источнике света. Проблема связана с тем обстоятельством, что при развитии разряда характер нагрузки меняется существенным образом. При этом происходит рассогласование, и энергия не поступает в разряд. Мы предлагаем путь решения этой проблемы, основанный на использовании многомодовой электродинамической системы, которая автоматически следит за изменением импеданса нагрузки. 2005 Article Microwave discharge as a source of light / Yu.Ya. Brodsky, N.F. Kovalev, A.O. Perminov, S.P. Shlepnev // Вопросы атомной науки и техники. — 2005. — № 2. — С. 208-210. — Бібліогр.: 1 назв. — англ. 1562-6016 PACS: 52.77.–j http://dspace.nbuv.gov.ua/handle/123456789/79812 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| institution |
Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| collection |
DSpace DC |
| language |
English |
| topic |
Low temperature plasma and plasma technologies Low temperature plasma and plasma technologies |
| spellingShingle |
Low temperature plasma and plasma technologies Low temperature plasma and plasma technologies Brodsky, Yu.Ya. Kovalev, N.F. Perminov, A.O. Shlepnev, S.P. Microwave discharge as a source of light Вопросы атомной науки и техники |
| description |
We try to analyze the ways to optimize microwave discharges in a microwave light source. The problem here is that as the discharge starts glowing, electrodynamic properties of the plasma being the load for the microwave source change significantly. During this, the characteristics of the light radiation from the plasma and efficiency of using the microwave energy are far from optimal. We propose a way to solve this problem, which is based on creating a multiresonance electrodynamic system tuning automatically as the value of the plasma load changes, thus providing reasonably good coupling in all regimes of operation of the lamp. |
| format |
Article |
| author |
Brodsky, Yu.Ya. Kovalev, N.F. Perminov, A.O. Shlepnev, S.P. |
| author_facet |
Brodsky, Yu.Ya. Kovalev, N.F. Perminov, A.O. Shlepnev, S.P. |
| author_sort |
Brodsky, Yu.Ya. |
| title |
Microwave discharge as a source of light |
| title_short |
Microwave discharge as a source of light |
| title_full |
Microwave discharge as a source of light |
| title_fullStr |
Microwave discharge as a source of light |
| title_full_unstemmed |
Microwave discharge as a source of light |
| title_sort |
microwave discharge as a source of light |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2005 |
| topic_facet |
Low temperature plasma and plasma technologies |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/79812 |
| citation_txt |
Microwave discharge as a source of light / Yu.Ya. Brodsky, N.F. Kovalev, A.O. Perminov, S.P. Shlepnev // Вопросы атомной науки и техники. — 2005. — № 2. — С. 208-210. — Бібліогр.: 1 назв. — англ. |
| series |
Вопросы атомной науки и техники |
| work_keys_str_mv |
AT brodskyyuya microwavedischargeasasourceoflight AT kovalevnf microwavedischargeasasourceoflight AT perminovao microwavedischargeasasourceoflight AT shlepnevsp microwavedischargeasasourceoflight |
| first_indexed |
2025-07-06T03:47:04Z |
| last_indexed |
2025-07-06T03:47:04Z |
| _version_ |
1836867780207443968 |
| fulltext |
MICROWAVE DISCHARGE AS A SOURCE OF LIGHT
Yu.Ya. Brodsky, N.F. Kovalev, A.O. Perminov, S.P. Shlepnev
Institute of Applied Physics Russian Science Academy, Nizhniy Novgorod, Russia,
e-mail: brod@appl.sci-nnov.ru
We try to analyze the ways to optimize microwave discharges in a microwave light source. The problem here is that
as the discharge starts glowing, electrodynamic properties of the plasma being the load for the microwave source
change significantly. During this, the characteristics of the light radiation from the plasma and efficiency of using the
microwave energy are far from optimal. We propose a way to solve this problem, which is based on creating a multi-
resonance electrodynamic system tuning automatically as the value of the plasma load changes, thus providing
reasonably good coupling in all regimes of operation of the lamp.
PACS: 52.77.–j
INTRODUCTION
Recently, the interest has appeared for creating highly
efficient sources of visible light, which are based on
microwave discharges in vapors of sulfur and other
substances [1]. Among the merits of such light sources
are sufficiently high luminous efficiency, low level of IR
and UV components in their radiation, quality color
rendition, long lifetime. However, there is a basic
difficulty in realizing such light sources, which is
associated with the dynamic character of the plasma load.
The problem is that the value of the load being (the
plasma of the gas discharge in the tube) changes as the
lamp starts glowing. Whereas this load is comparatively
small before the discharge is ignited and at the initial
stage of lamp glowing, it changes as the lamp comes up to
the stationary operation regime, and achieves some value
which differs from the initial one significantly. In a
simplest single-mode electrodynamic system the
inevitable situations are either a high reflection level at
the beginning of lamp glowing, or a not exactly matched
regime of magnetron operation at the stationary phase of
the discharge. This paper analyses this problem and
proposes a way to solve it, which is based on creating a
multi-resonance electrodynamic system that tunes
automatically as the value of the plasma load changes,
thus providing sufficiently good coupling in all regimes
of lamp operation.
DYNAMIC CHARACTER OF THE PLASMA
LOAD
A characteristic feature of microwave light sources is
the non-stationary character of the load being the plasma
of the lamp gas discharge. This feature is associated with
the fact that after the gas in the tube is broken down and
the discharge starts to glow, the impedance of the load
changes drastically. Further the gas is heated, the working
substance (sulfur, selenium or metal halogens) is
evaporated, and the density of charged particles grows,
which also changes the load impedance [1]. It is
especially important to take into account variations of the
pressure in the tube when pulsed microwave sources are
used, since at the initial stage the gas temperature is low,
and after the end of the microwave pulse the plasma
degenerates in a short time. Hence, it is necessary to
breakdown the gas again at each consequent pulse, but at
a higher density of neutral particles already. However,
increasing density of neutrals makes the frequency of
electron-neutral collisions higher, which, in its turn,
results in the increase in the intensity of the electric field
required for a secondary gas breakdown.
Where as at the stage of discharge ignition and initial
gas breakdown the value of the load is not greate, and the
determining factor is the losses in the resonator walls,
later, as the lamp warms up and comes up to the
stationary operation regime, the share of the power
absorbed in the discharge becomes greater, which is
directly the objective and a necessary requirement for
high luminous efficiency of the lamp.
Coexistence of several lamp operation regimes, which
are very different, and the necessity to have a stable
transition between them makes it necessary to create such
an electrodynamic system, which could change its
properties dynamically as the lamp starts glowing and the
value of the load changes. Additionally, we have to
provide optimal coupling and a stable dynamic transition
from the stage of the initial breakdown to the stage of
stationary glowing.
We think that the most efficient way is to create a multi-
resonance system with the ability to tune dynamically to
the changing load. Principal requirements to such a
system is the possibility to tune the resonance frequency
of the system in the required direction to compensate the
variation of the resonance frequency introduced by the
changing plasma load, on the one hand, and to change the
value of the coupling between the feeder and the
resonator, on the other hand.
The electrodynamic system proposed here has three
operation regimes, which differ in terms of the value of
the coupling between the magnetron and the resonator.
The first of them is the initial breakdown in the tube, the
second provides a reliable transition to the stationary
glowing regime, and the third maintains the regime of
lamp operation. Each of these regimes is characterized by
the position and width of the resonance band. For
example, the ignition regime requires good coupling of
the magnetron with an empty (containing no plasma)
resonator, and achieving of high field intensity in it.
Hence, in this regime it is necessary to produce a high-Q-
factor resonance tuned precisely to the magnetron
frequency. The main regime of operation requires
coupling with the well-absorbing plasma load and,
208 Problems of Atomic Science and Technology. Series: Plasma Physics (11). 2005. № 2. P. 208-210
correspondingly, a significantly lower Q-factor and better
coupling with the resonator. The transition regime should
provide a stable and reliable transition from the ignition
regime to the glowing regime, thus it is necessary to
provide an intermediate value of the magnetron-resonator
coupling, i.e. the resonance should have an intermediate
Q-factor.
ELECTRODYNAMIC SYSTEM
In terms of its design, such a light source is a quartz tube
with the required filling placed in a microwave resonator
made partially of a metal grating with high light
transparence. The microwaves were generated by a
magnetron at the frequency of 2.45 GHz.
Figure 1 shows the scheme of a version of such a
microwave light source. The microwaves are generated
by a magnetron (1), the antenna of which (3) is placed in
a circular waveguide, which is the feeder and via the
coupling slit (7) is coupled with a cylindrical resonator (2)
with a movable wall (6). The resonator is made partially
of a metal grating that is sufficiently transparent for light,
but at the same time screens the microwaves. A quartz
tube (4) on the axis (5) filled with sulfur or a mixture of
metal halogens is placed in the resonator. To provide
ignition and evaporation of solid-state admixture, the tube
is filled also with an inert gas, e.g. argon under the
pressure of 10-20 Torr.
Two polarization-degenerate modes H111 and one E010
mode of a circular resonator are used as working modes
in the proposed electrodynamic system. The latter modes
provides a high coefficient of the feeder's coupling with
the resonator loaded with a plasma load, which is well-
absorbing and, thus, provides good coupling with the
magnetron. Figure 1 shows also force lines of the electric
field (8) for mode H111. Frequency tuning of the
electrodynamic system is performed by selecting the
diameter of the cylinder and changing its height. The
coupling factor is controlled by changing the depth of the
antenna position in the resonator. Thus, the tuning of the
electrodynamic system is an iterative procedure.
Figures 2a and 2b show frequency dependences of the
coefficient of reflection from the resonator for different
values of the load placed in the resonator. In the absence
of absorption (Fig. 2a) one can see that there is a sharp
and deep resonance: a dip in the reflection coefficient.
This regime is for the initial gas breakdown.
209
Fig. 1:
a) schematic drawing of the microwave light source;
b) photography of the microwave light source; there is a
quartz bulb inside of grid resonator
a
b
2350 2400 2450 2500 2550
MHz
-25
-20
-15
-10
-5
0
dB
Fig.2а
Reflection coeff icient (low absorbation)
2350 2400 2450 2500 2550
MHz
-25
-20
-15
-10
-5
0
dB
Fig.2b
Reflection coeff icient (high absorbation)
Fig. 2. Reflection coefficient: a )low absorption;
b) high absorption
a
b
The pronounced dip evidences that the value of the
magnetron-resonator coupling selected by us is close to
the losses in the empty resonator, thus providing, in
accord with our idea, the maximum amplitude of the field
in the resonator required for the breakdown.
Figure 2b shows a similar frequency dependence of the
reflection ratio under the condition of a sufficiently strong
absorption caused by introduction of a model load. It is
seen that a wide and deep resonance takes place here. In
this case we have the regime of operation, in which the
magnetron is strongly coupled with the resonator.
Figure 3 presents the photograph of the working
microwave light source.
CONCLUSIONS
This paper describes the electrodynamic system of a
microwave lamp with a three-mode resonator. The system
is designed to provide stable ignition of the discharge in
the lamp and the transition to the stationary glowing
regime. Optimization of the discharge evolution process
and of the plasma load coupling at the stationary stage
made it possible to achieve high efficiency, up to
140lm/W.
REFERENCES
1. J.T.Dolan, M.G.Ury and C.H.Wood // 6-th Int.Symp.on
Science and Technology of Light Sources, Budapest,
1992.
МИКРОВОЛНОВОЙ РАЗРЯД КАК ИСТОЧНИК СВЕТА
Ю.Я. Бродский, Н.Ф. Ковалев, А.О. Перминов, С.П. Шлепнев
Проведен анализ путей оптимизации согласования микроволнового разряда в микроволновом источнике
света. Проблема связана с тем обстоятельством, что при развитии разряда характер нагрузки меняется
существенным образом. При этом происходит рассогласование, и энергия не поступает в разряд. Мы
предлагаем путь решения этой проблемы, основанный на использовании многомодовой электродинамической
системы, которая автоматически следит за изменением импеданса нагрузки.
МІКРОХВИЛЬОВИЙ РОЗРЯД ЯК ДЖЕРЕЛО СВІТЛА
Ю.Я. Бродський, М.Ф. Ковальов, А.О. Пермінов, С.П. Шлепнєв
Проведено аналіз шляхів оптимізації узгодження мікрохвильового розряду в мікрохвильовому джерелі
світла. Проблема зв'язана з тією обставиною, що при розвитку розряду характер навантаження міняється
істотно. При цьому відбувається неузгодженість, і енергія не надходить у розряд. Ми пропонуємо шлях
рішення цієї проблеми, заснований на використанні багатомодової електродинамічної системи, що автоматично
стежить за зміною імпедансу навантаження.
210
Fig. 3. Working 200 W microwave light source
|