High resolution gas ionization chamber in proportional mode for low energy applications

The operation of the ETH gas ionization detector as a proportional chamber, where a secondary ionization avalanche is initiated between the Frisch grid and anode, was investigated for ions covering the mass range from H to ¹²⁷I. By amplifying the detector electron signal through secondary ionization, the limitations due to the sensitivity of the detector electronics are minimized. It could be demonstrated that in the energy range of a few hundreds of keV and below a proportional chamber clearly outperforms a conventionally used gas ionization detector. Protons below 10 keV were measured with a resolution better than 1.4 keV and a good linearity of the particle energy and detector signal was found in the energy range between 50 and 1000 keV. At higher energies almost no difference in resolution for the two operation modes could be found.