Experimental study of the adaptive gain feature for improved position-sensitive ion spectroscopy with Timepix2

AbstraktAbstract

In the present work, we study the Timepix2 pixels' high energy response in the so-called adaptive gain mode. Therefore, Timepix2 with a 500 mu m thick silicon sensor was irradiated with protons of energies in the range from 400 keV to 2 MeV and alpha-particles of 5.5 MeV from 241Am. A novel method was developed to determine the energy deposit in single pixels of particle imprints, which are spread out over a set of neighbor pixels (cluster). We show that each pixel is capable of measuring the deposited energy from 4 keV up to similar to 3.2 MeV. Reconstructing the full energy content of the clusters, we found relative energy resolutions (sigma/E) better than 2.7% and better than 4% for proton and alpha-particle data, respectively. In a simple experiment with a 5.5 MeV alpha-particle source, we demonstrate that energy losses in thin (organic) specimen can be spatially resolved, mapping out sample thickness variations, with a resolution around 1-2 mu m, across the sensor area. The inherent spatial resolution of the device was determined to be 350 nm in the best case.

In the present work, we study the Timepix2 pixels' high energy response in the so-called adaptive gain mode. Therefore, Timepix2 with a 500 mu m thick silicon sensor was irradiated with protons of energies in the range from 400 keV to 2 MeV and alpha-particles of 5.5 MeV from 241Am. A novel method was developed to determine the energy deposit in single pixels of particle imprints, which are spread out over a set of neighbor pixels (cluster). We show that each pixel is capable of measuring the deposited energy from 4 keV up to similar to 3.2 MeV. Reconstructing the full energy content of the clusters, we found relative energy resolutions (sigma/E) better than 2.7% and better than 4% for proton and alpha-particle data, respectively. In a simple experiment with a 5.5 MeV alpha-particle source, we demonstrate that energy losses in thin (organic) specimen can be spatially resolved, mapping out sample thickness variations, with a resolution around 1-2 mu m, across the sensor area. The inherent spatial resolution of the device was determined to be 350 nm in the best case.