Voltage pulse generation using CO₂laser irradiated solid target plasmas

Abstract

Voltage pulses generated as a result of electron emission from a CO2 laser-produced solid target plasma have been studied and analysed with the aim of evaluating the suitability of the plasma cell as a pulse-shape detector. The optimum output voltage is found to be relatively insensitive to target chamber geometry and maximises with a background gas pressure of approximately 10-2 kPa, independent of gas species or target material. Voltage-current characteristics for a Cu plasma suggest that the plasma cell behaves as a thermionic generator and a model has been developed which gives a reasonable account of the experimental results. Whilst high voltages (>100 V into 50 Omega ) can be produced using a modest TEA CO2 laser, the nonlinearity of response limits the usefulness of the plasma cell as a pulse-shape detector.