Response of the pixel detector Timepix to heavy ions

The response of the pixel detector Timepix to ions in the 4-110 MeV kinetic energy range and A=3-136 mass range has been studied at the fission-fragment separator Lohengrin of the Institute Laue Langevin in Grenoble. Timepix detects single ions measuring their position, kinetic energy, and time of arrival. Heavy ions with energy above several tens of 10 MeV produce a distortion of the electronic pixel signal response which arises when the energy collected is, under conventional detector settings, of around ∼1 MeV per pixel. This effect can be suppressed, and the detector energy range extended, by suitable pixel signal baseline and threshold levels, together with optimally low sensor chip bias voltage. Reasonable results are achieved within the range of ion mass and energy studied extending the linearity level of per pixel measured energy up to ∼2 MeV.