Research on the electroperturbation effects of ultrashort high field pulses in cancer cells requires subnanosecond rise time, high voltage pulses delivered to low impedance biological loads. Here we present a compact solid-state pulse generator developed for this application. The pulse is generated by switching a chain of avalanche transistors configured as a tapered transmission line from high voltage to ground. The system features a built in 1400:1 capacitively compensated resistive voltage divider. The divider, with a 3 dB point at 910 MHz, overcomes challenges in the direct measurement of the high frequency components of the output pulse. The generator is capable of producing a 0.8 ns rise time, 1.3 ns wide, 1.1 kV pulse into a 50 Ω load at a maximum repetition rate of 200 kHz. Techniques to implement physical layouting strategies to achieve subnanosecond rise times are outlined. Problems faced in integrating the subnanosecond pulse generator with a biological load are discussed. This pulse generator will be used in experiments aimed at electromanipulation of intracellular biomolecular structures.
Intracellular electro-manipulation experiments require subnanosecond high voltage pulses delivered to low impedance biological loads. We present here the design and construction of an experimental setup to deliver such subnanosecond high voltage pulses to biological cell solutions. This low-parasitic electronic setup interfaces our avalanche transistor-switched pulse generation system with the imaging and monitoring apparatuses used for bio-photonic studies of pulse-induced intracellular effects. The setup features a custom fabricated microscope slide to hold the cell solution under study, and a printed circuit board designed to carry the output pulse from the pulse generator to micro-machined electrodes on the glass slide. The pc-board and the slide are designed to match the load impedance of the pulse generator. This minimizes reflections back into the pulse generator, and minimizes distortion of pulse shape and pulse parameters. Further, the pc-board contains a custom-made high bandwidth voltage divider to allow for real-time monitoring of pulses delivered to the cell solution.
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