**2. Principle of operation and designs**

A general scheme for the generation of optical radiation in the visible wavelength range (visible light) using plasma illuminating devices based on an electrodeless sulfur lamp with microwave excitation is shown in **Figure 2**. It is necessary to note that these devices use the transformation of electrical energy into the energy of light waves by stages. In the first stage, the secondary power source 1 converts the alternating voltage of 220 V and the frequency of 50 Hz into a constant voltage of 3.8–4.2 kV, which is fed to the anode of the magnetron.

In the second stage, the magnetron generator 2 converts the DC energy into the energy of electromagnetic oscillations. As a result, at the output of the magnetron in the waveguide 4, there are oscillations having the frequency of 2.45 GHz and the output power of about ~900 W. These oscillations excite the electromagnetic field in the electrodynamic structure 5, at the maximum of the electric field of which the sulfur lamp is placed.

At the third stage, physicochemical processes proceed in the inner space of the sulfur lamp under the influence of an electromagnetic field, as a result of which is the generation of optical radiation in the visible wavelength range (380–780 nm). This radiation is focused and output into the free space.

In order to determine the energy efficiency of the lighting system, the power consumed by the magnetron generator from the external (primary) network was investigated. The results of these studies are shown in **Figure 3**. It can be seen that the power consumed from the network by the lighting system is constantly increasing until the appearance of the primary glow of the lamp, which corresponds to 1700–1750 W of power consumption. Thereafter the power consumption from the network is stopped; the energy of the electromagnetic field is absorbed at once by the argon-sulfur mixture. As result, the generation of optical radiation takes place. The lighting system consumes ~2000 W in a stationary mode providing stable light emission.

The main elements of the lighting device and values of its main parameters are shown in **Figure 4**.

An important element of the lighting device on the basis of the sulfur lamp is the construction of an electrodynamic structure, the main purpose of which is to form a special structure of the electromagnetic field required to excite (pump) an electrodeless sulfur lamp. A bulb of the sulfur lamp is placed at the maximum of the electrical component of the electromagnetic field excited in the electrodynamic structure.

As an electrodynamic structure, one is usually used optically transparent (mesh) cylindrical microwave cavity, inside of which a quartz bulb of the sulfur lamp is placed [4]. The outside surface of the cavity is done from thin wire and has mesh surface for free passage of optical radiation. A general view of the cavity with a bulb of the sulfur lamp is shown in **Figure 5**.

**Figure 4.** List of basic parameters of the elements of the lighting device based on an electrodeless sulfur lamp with

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The main requirement for a resonant method of excitation of the electrodeless sulfur lamp is to maintain a mode of stable oscillations of the electromagnetic field in the cavity (resonance) (for example, for cylindrical cavity, one can use the following modes of oscillations: TE111, TЕ112, TE011, TM010 and TM111). The use of a cylindrical cavity allows reasonably simply to hold the sulfur lamp along its longitudinal axis, to ensure its stable rotation for uniform cooling of

In addition to the resonant method of exciting the sulfur lamp, of great interest is the method enabling to form an electromagnetic field in a waveguide by adding two counter-propagating coher-

of the lighting device in which used this excitation method of the sulfur lamp is shown in **Figure 6**.

possessing the identical linear polarization [5]. The general view

its surface and thus to select an optimum temperature regime for its operation.

ent monochromatic waves *E*

microwave excitation.

→ 1 and *E* → 2

**Figure 3.** Dynamics of the power consumed by the magnetron generator.

**Figure 2.** General scheme of converting energy in the plasma lighting device.

Microwave Energy and Light Energy Transformation: Methods, Schemes and Designs http://dx.doi.org/10.5772/intechopen.73755 79

**Figure 3.** Dynamics of the power consumed by the magnetron generator.

**2. Principle of operation and designs**

into the free space.

excited in the electrodynamic structure.

**Figure 2.** General scheme of converting energy in the plasma lighting device.

A general scheme for the generation of optical radiation in the visible wavelength range (visible light) using plasma illuminating devices based on an electrodeless sulfur lamp with microwave excitation is shown in **Figure 2**. It is necessary to note that these devices use the transformation of electrical energy into the energy of light waves by stages. In the first stage, the secondary power source 1 converts the alternating voltage of 220 V and the frequency of 50 Hz into a constant voltage of 3.8–4.2 kV, which is fed to the anode of the magnetron.

In the second stage, the magnetron generator 2 converts the DC energy into the energy of electromagnetic oscillations. As a result, at the output of the magnetron in the waveguide 4, there are oscillations having the frequency of 2.45 GHz and the output power of about ~900 W. These oscillations excite the electromagnetic field in the electrodynamic structure 5,

At the third stage, physicochemical processes proceed in the inner space of the sulfur lamp under the influence of an electromagnetic field, as a result of which is the generation of optical radiation in the visible wavelength range (380–780 nm). This radiation is focused and output

In order to determine the energy efficiency of the lighting system, the power consumed by the magnetron generator from the external (primary) network was investigated. The results of these studies are shown in **Figure 3**. It can be seen that the power consumed from the network by the lighting system is constantly increasing until the appearance of the primary glow of the lamp, which corresponds to 1700–1750 W of power consumption. Thereafter the power consumption from the network is stopped; the energy of the electromagnetic field is absorbed at once by the argon-sulfur mixture. As result, the generation of optical radiation takes place. The lighting system consumes ~2000 W in a stationary mode providing stable light emission. The main elements of the lighting device and values of its main parameters are shown in **Figure 4**. An important element of the lighting device on the basis of the sulfur lamp is the construction of an electrodynamic structure, the main purpose of which is to form a special structure of the electromagnetic field required to excite (pump) an electrodeless sulfur lamp. A bulb of the sulfur lamp is placed at the maximum of the electrical component of the electromagnetic field

at the maximum of the electric field of which the sulfur lamp is placed.

78 Emerging Microwave Technologies in Industrial, Agricultural, Medical and Food Processing

**Figure 4.** List of basic parameters of the elements of the lighting device based on an electrodeless sulfur lamp with microwave excitation.

As an electrodynamic structure, one is usually used optically transparent (mesh) cylindrical microwave cavity, inside of which a quartz bulb of the sulfur lamp is placed [4]. The outside surface of the cavity is done from thin wire and has mesh surface for free passage of optical radiation. A general view of the cavity with a bulb of the sulfur lamp is shown in **Figure 5**.

The main requirement for a resonant method of excitation of the electrodeless sulfur lamp is to maintain a mode of stable oscillations of the electromagnetic field in the cavity (resonance) (for example, for cylindrical cavity, one can use the following modes of oscillations: TE111, TЕ112, TE011, TM010 and TM111). The use of a cylindrical cavity allows reasonably simply to hold the sulfur lamp along its longitudinal axis, to ensure its stable rotation for uniform cooling of its surface and thus to select an optimum temperature regime for its operation.

In addition to the resonant method of exciting the sulfur lamp, of great interest is the method enabling to form an electromagnetic field in a waveguide by adding two counter-propagating coherent monochromatic waves *E* → 1 and *E* → 2 possessing the identical linear polarization [5]. The general view of the lighting device in which used this excitation method of the sulfur lamp is shown in **Figure 6**.

In this case, there is a condition satisfied for the frequencies of these waves to be the same (*ω*<sup>1</sup> <sup>=</sup> *<sup>ω</sup>*<sup>2</sup> <sup>=</sup> *<sup>ω</sup>*) and their propagation constant to be complex and equal to *<sup>γ</sup>* <sup>=</sup> *<sup>α</sup>* <sup>+</sup> *<sup>j</sup>*, where *α* is the attenuation constant determined by plasma parameters and *β* is the phase constant of the traveling electromagnetic wave. According to the principle of superposition, the intensity of

> <sup>→</sup> = *E* → <sup>1</sup> + *E* →

> = < *E*<sup>1</sup>

**Figure 8.** Schematic diagram of lighting device based on an electrodeless sulfur lamp with microwave excitation.

Herein consider the energy description of the wave processes and put the first expression (1)

<sup>2</sup> > +< *E*<sup>1</sup>

<sup>2</sup> > +2 ⋅ < *E*

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→ <sup>1</sup> ⋅ *E* →

<sup>2</sup> (1)

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<sup>2</sup> > (2)

the resultant electromagnetic field is

< *E*<sup>2</sup> > = < (*E*

*E*

in the square. After averaging over time, we finally obtain

→ <sup>1</sup> + *E* → 2) 2

**Figure 5.** General view of the cavity with a sulfur lamp bulb.

**Figure 6.** Schematic of the sulfur lamp in a waveguide. 1—a bulb of the sulfur lamp; 2—a waveguide; 3—optical radiation (light).

**Figure 7.** The distribution of energies of the electromagnetic waves in a waveguide.

In this case, there is a condition satisfied for the frequencies of these waves to be the same (*ω*<sup>1</sup> <sup>=</sup> *<sup>ω</sup>*<sup>2</sup> <sup>=</sup> *<sup>ω</sup>*) and their propagation constant to be complex and equal to *<sup>γ</sup>* <sup>=</sup> *<sup>α</sup>* <sup>+</sup> *<sup>j</sup>*, where *α* is the attenuation constant determined by plasma parameters and *β* is the phase constant of the traveling electromagnetic wave. According to the principle of superposition, the intensity of the resultant electromagnetic field is

$$
\vec{E} = \vec{E}\_1 + \vec{E}\_2 \tag{1}
$$

Herein consider the energy description of the wave processes and put the first expression (1) in the square. After averaging over time, we finally obtain

**Figure 8.** Schematic diagram of lighting device based on an electrodeless sulfur lamp with microwave excitation.

**Figure 7.** The distribution of energies of the electromagnetic waves in a waveguide.

**Figure 6.** Schematic of the sulfur lamp in a waveguide. 1—a bulb of the sulfur lamp; 2—a waveguide; 3—optical

**Figure 5.** General view of the cavity with a sulfur lamp bulb.

80 Emerging Microwave Technologies in Industrial, Agricultural, Medical and Food Processing

radiation (light).

In the second expression (2), the total average total energy < *E*<sup>2</sup> > depends on the value of the interference term < *E* → <sup>1</sup> ⋅ *E* → <sup>2</sup> <sup>&</sup>gt;. In the case when <sup>&</sup>lt; *<sup>E</sup>* → <sup>1</sup> ⋅ *E* → <sup>2</sup> <sup>&</sup>gt; <sup>=</sup> <sup>0</sup> (there is no interference), the total energy in the waveguide is equal to the sum of the energies of the main and counter electromagnetic waves. When the condition is fulfilled, when < *E* → <sup>1</sup> ⋅ *E* → <sup>2</sup> <sup>&</sup>gt; <sup>≠</sup> 0, the total energy is not equal to the sum of the energies of the waves running toward each other, but in the waveguide, there is interference of the waves.

**Figure 9** presents a comparison of the spectral characteristics of extra-atmospheric solar radiation and the simulators of solar radiation on the basis of lamps of the artificial lighting.

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For testing the photoelectric converters and solar batteries, as a rule, the incandescent and gasdischarger lamps are applied in the SSRs as the light sources. This is due to the requirements to get the values of parameters such as the identity of the SSRs emission spectrum and spectrum of solar radiation, the color temperature (the color temperature of the extra-atmospheric solar radiation is ∼5900 K), the high stability of the radiation flux and the small nonuniformity of energy illumination that determines the adequacy of measuring the parameters of the photoelectric converters and solar cells [8]. At the same time, for example, a necessity of temporal stability of the radiation flux is a significant limiting factor for using a number of arc sources in photovoltaic investigations, although their spectral composition is most consistent with the solar emission under conditions of zero atmospheric mass (AM0). The use of pulse gas-discharge lamps having a satisfactory spectral composition, in addition to the indicated temporary instability associated with the characteristics of their launch systems, requires to use high-speed measuring equipment, which significantly increases the expenses for creating the entire installation. According to

**1.** The mirror incandescent and quartz halogen lamps that provide a satisfactory spectral composition of the radiation located in the range of 0.4–1.1 μm. These lamps are used in simple SSRs in order to simulate solar radiation for research and technological purposes in

**2.** The arc-shaped gas-discharge xenon lamps (including with combined gas filling) for highquality SSRs, used in precise measurements of the photovoltaic convertors parameters. **3.** The most widely used are arc xenon spherical lamps, which have a spectrum very close to the solar one (see **Figure 9**); however, owing to an energy release in the infrared region of its spectrum, it is necessary to use corrective optical filters in the SSRs that use the lamps

**Figure 9.** Spectral emission curves of the extra-atmospheric solar emission and sources of radiation for SSRs.

the above parameters, the greatest interest can be found in such sources as:

the tests of photovoltaic cells.

of this type.

Of practical interest for exciting a sulfur lamp in a waveguide causes is the case when the condition < *E* → <sup>1</sup> ⋅ *E* → <sup>2</sup> <sup>&</sup>gt; <sup>=</sup> 0 is fulfilled. As a result, it is possible to ensure a uniform distribution of the total electromagnetic field in the region of the electrodeless lamp location and a stable gas discharge in the lamp by creating a standing wave in a waveguide of arbitrary length *L* with optically transparent outside surface (mesh surface).

**Figure 7** shows the distributions of full energy of the electromagnetic waves <sup>&</sup>lt; *<sup>E</sup>*<sup>1</sup> <sup>2</sup> <sup>&</sup>gt; +< *<sup>E</sup>*<sup>2</sup> <sup>2</sup> >, which is introduced from different ends of the waveguide as fundamental <sup>&</sup>lt; *<sup>E</sup>*<sup>1</sup> <sup>2</sup> > and counterpropagating <sup>&</sup>lt; *<sup>E</sup>*<sup>2</sup> <sup>2</sup> > electromagnetic waves. **Figure 8** schematically presents diagram of lighting devices on the basis of the electrodeless sulfur lamp with microwave excitation.

**Figure 8** demonstrates a schematic diagram of lighting device based on an electrodeless sulfur lamp in the case excitation by adding two counter-propagating coherent monochromatic waves. For this excitation method, an electromagnetic wave is generated by a magnetron 5 and through a waveguide tee 4 through waveguide 3 enters a mesh waveguide 2 within which an electrodeless sulfur lamp 1 is located.
