München 2019 – wissenschaftliches Programm

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SYPP: Symposium Pulsed Power für Medizin und Biotechnologie

SYPP 1: Pulsed Power für Medizin und Biotechnologie I

SYPP 1.2: Hauptvortrag

Donnerstag, 21. März 2019, 11:15–11:45, HS 3

30 years of Pulsed Power in medical Excimer laser — •Claus Strowitzki — MLase AG

This paper gives an overview of the development of pulsed power in medical excimer lasers. Pulsed power in medical excimer lasers is quite challenging. The load is a discharge; this means the impedance changes from open to virtually a short circuit in some ns. Hence a matching of the pulsed power module to the load is not possible. In the last 30 years 3 development big steps were made. First circuits work with a Thyratron. These circuits were quite simple, but suffer from low lifetime. About 50 % of the energy is reflected by the discharge. The reflected Energy produces oscillation in the circuit. The next step was the replacement of the Thyratron by a Thyristor. Due to the lower voltage and switching capability, the voltage has to be raised by a pulse transformer and the pulse has to be compressed by magnetic pulse compression (usually 3 stages). IGBT modules became more powerful and enable faster switching than Thyristors. Hence, the pulse compression network became smaller (only 2 compression stages) and due to a blocking diode together with an energy recovery circuit, reflected energy could be restored. These modules avoid oscillating and enable excellent live time. The live time of the laser is also extended because total charge through the discharge is reduced. This is the current state of the art. Current development is a new circuit topology based on a full bridge primary switch configuration. These circuits have smaller part count and uses standard phase legs IGBT modules. They are especially suited for high repetition rate operation (above one kHz).