Characterizing the response of Timepix solid state detectors to dust impacts

Abstract

Timepix Solid State Detectors (TSSDs) are used in a range of applications, including high energy particle physics, x-ray imaging spectroscopy, medical imaging, radiation monitors and compact dosimeters. In space sciences, such detectors have been used for characterizing the radiation environments of the Earth and lunar surface. This study is a pilot investigation of the response of TSSDs to high-velocity dust impacts. The setup used for the measurements is a silicon slab with 500μm thickness combined with the Timepix 2 read-out chip with a pixel size of 55×55 μm2. The outer surface of the SSD is coated with a 150 nm thick layer of aluminum to eliminate the sensitivity to light. The dust accelerator facility operated at the University of Colorado is used to expose the TSSD to micron- and sub-micron sized iron particles in a velocity range of 1–10 km/s. A fraction (5%) of the impacting dust particles were detected by the TSSD. The primary mechanism of the detection is through the light generated upon the impact and the charge signal spreads over multiple pixels. The fraction of dust particles kinetic energy that is converted to detectable charge on the TSSD is small, in the range of 10−3−10−6. The largest craters generated by the dust impacts were examined using a scanning electron microscope (SEM). The SEM images confirm that the particles penetrated the aluminum layer and the craters contain iron residue from the dust material. Over the investigated impact parameter range, the TSSD does not suffer a permanent damage from the dust impacts. Due to their small size and relatively low sensitivity to dust impacts, TSSDs could be used as dust detectors only in environments with high dust fluxes (e.g., in cometary trails), or where the precision measurements of the impact location are desired.