Magnetron Coupling to Sulfur Plasma Bulb

Koulakis, John P.; Thornton, Alexander L. F.; Putterman, Seth

doi:10.1109/tps.2017.2759122

Cited by 6 publications

(5 citation statements)

References 7 publications

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“…(14). The effect this has can be seen in the low temperature side of Figure 2 where Q c and A were set to 1000 and 1 respectively [11]. In general, both acoustic time scales depend on the gas, its density, and its temperature.…”

Section: Coupling Sufficient Microwave Powermentioning

confidence: 99%

“…In order to assess whether this amplification mechanism can generate acoustic energy sufficient to exceed the acoustic losses, we will solve Eq. (11) in the simplest representative case, a spherical cavity with rigid walls and a uniform temperature. Following the technique presented in [14], we will compare the growth time constant due to amplification to the decay constant due to acoustic damping.…”

Section: Self-oscillation In a Spherical Cavitymentioning

confidence: 99%

“…In this letter, we present a type of acoustic selfoscillation that may occur in an acoustic cavity filled with partially ionized gas located within a microwave cavity as shown in Figure 1. For the present analysis, the configuration is assumed similar to that found in [9][10][11], where the acoustic cavity was a sealed quartz sphere with a radius around 2 cm, and the surrounding microwave cavity was a thin-walled metallic cavity with a resonance near 2.45 GHz. Future implementations may include a means to couple the sound out of the acoustic cavity, for example by attaching a horn shaped outlet.…”

Section: Introductionmentioning

confidence: 99%

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Acoustic self-oscillation in a spherical microwave plasma

2019

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We present a method of sound amplification and self-oscillation in high pressure partially ionized gas. Continuous microwaves incident on partially ionized gas may sustain and amplify an acoustic field if increased ionization during the sound field's adiabatic compression enhances RF power absorption. Amplifying sound in this way enables the generation of high amplitude sound in a cavity containing partially ionized gas without mechanical driving or precise knowledge of its resonance frequency. This method of amplification may open opportunities within thermoacoustics such as using 3D geometries and volumetric gain mechanisms.

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Section: Coupling Sufficient Microwave Powermentioning

confidence: 99%

Section: Self-oscillation In a Spherical Cavitymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Acoustic self-oscillation in a spherical microwave plasma

2019

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“…To solve the problem of the startup, many methods are proposed for different kinds of plasma lamps. For instance, traditional methods usually rely on a high-power magnetron with a single frequency to excite plasma [8][9][10], but the instantaneous huge, reflected power due to the impedance mismatch will damage the magnetron circuit even if there are external adjusted impedance-matched elements, and the energy conversion efficiency is extremely low. Recently, solid-state RF driver technical solutions using voltage-controlled oscillators (VCO) as RF excitation signal sources for plasma light are mainly adopted [11,12].…”

Section: Introductionmentioning

confidence: 99%

A Startup Control Method for Plasma Lamps by Using Fractional-N Phase-Locked Loop Microwave Driver

Jia

Huan

et al. 2022

Electronics

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The microwave-driven plasma light source has the feature of the full spectrum, similar to sunlight, and has broad application prospects. Startups of plasma lamps are very difficult since the plasma density and the resonator impedance are changing constantly with the warm-up process and the RF driver can hardly couple the power to the plasma efficiently. This paper presents a startup control method for plasma lamps by using an integrated fractional-N phase-locked loop (PLL) as the RF signal source. An RF control module including a 21 dBm RF source with a band of 430–460 MHz and detection circuits for the RF driver is developed, and the startup process of the plasma lamp is further studied by analyzing the return loss of the resonator under the plasma load. According to the test result, the maximum frequency deviation of the RF control module is 3.3 kHz over the working temperature range of −40–80 °C. The designed RF control module is used to drive a high-power amplifier to start the plasma lamp automatically. It takes 79 s to achieve the stable arc operation from the gas breakdown. The return loss of the resonator is −26 dB, with an incident power of 171 W and reflected power of 418 mW, indicating that the RF driver and the plasma achieve good coupling. Compared with continuous wave, the luminous flux of the lamp powered by RF pulse improves by 18% under the same electric power. This startup control method has stable performance, small temperature drift, and an effective control function for plasma lamps.

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“…In order to drive acoustic resonances within the bulb, our magnetron power supply has been modified to be able to pulse at frequencies between 5-100 kHz, and 5-95% duty cycle, according to a design by S. Gavin et al [17,18]. We have described our waveguide circuit elsewhere [19].…”

mentioning

confidence: 99%

Trapping of plasma enabled by pycnoclinic acoustic force

et al. 2018

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Sound can hold partially ionized sulfur at the center of a spherical bulb. We use the sulfur plasma itself to drive a 180 dB re 20 µPa sound wave by periodically heating it with microwave pulses at a frequency that matches the lowest order, spherically symmetric acoustic resonance of the bulb. To clarify the trapping mechanism, we generalize acoustic radiation pressure theory to include gaseous inhomogeneities and find an interaction of highamplitude sound with density gradients in the gas through which it propagates. This is the pycnoclinic acoustic force (PAF). Though generated by rapidly oscillating sound waves, it has a finite time average and manipulates the plasma through density gradients at its boundary. The PAF is essential for the description of the trap holding a plasma against its own buoyancy as well as understanding convection in the region outside the plasma. It has implications for pulse tubes, thermoacoustic engines, thermal vibrational convection in microgravity, combustion in the presence of sound, and the modeling of Cepheid variable stars

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Magnetron Coupling to Sulfur Plasma Bulb

Abstract: Sulfur plasma lamps are a convenient, table-top system for the study of acoustics in dense, weakly ionized plasmas. Herein we describe the construction and tuning of a passive waveguide circuit capable of igniting and sustaining the sulfur plasma and exciting acoustic modes within it.

Cited by 6 publications

References 7 publications

Acoustic self-oscillation in a spherical microwave plasma

Acoustic self-oscillation in a spherical microwave plasma

A Startup Control Method for Plasma Lamps by Using Fractional-N Phase-Locked Loop Microwave Driver

Trapping of plasma enabled by pycnoclinic acoustic force

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