Calculations of acoustic resonances in arc lamp discharge vessels

Summary form only given. Improvements in switched-mode power electronics have increased the use of electronic power supplies for lighting discharges. An issue of concern for the designers of supplies for high-pressure discharge lamps is the excitation of acoustic resonances by the electrical ripple generated by the switching electronics. These resonances of the gas in the arc discharge vessel have been well known since the 1960´s, with detrimental effects ranging from minor perturbations in the shape or position of the arc, to severe instability and extinguishing the arc. This paper presents calculations of the frequencies and wavefunctions of the acoustic modes in discharge vessels, complete with the distortion of the modes caused by the thermal distribution in the gas. It also shows the techniques used to make these calculations, which allow for vessel walls which are arbitrarily shaped surfaces of rotation.