Charged particle tracking with the Timepix ASIC

A prototype particle tracking telescope was constructed using Timepix and Medipix ASIC hybrid pixel assemblies as the six sensing planes. Each telescope plane consisted of one 1.4 cm2 assembly, providing a 256 ×256 array of 55 μ m square pixels. The telescope achieved a pointing resolution of 2.4 μ m at the position of the device under test. During a beam test in 2009 the telescope was used to evaluate in detail the performance of two Timepix hybrid pixel assemblies; a standard planar 300 μ m thick sensor, and 285 μ m thick double sided 3D sensor. This paper describes a charge calibration study of the pixel devices, which allows the true charge to be extracted, and reports on measurements of the charge collection characteristics and Landau distributions. The planar sensor achieved a best resolution of 4.0 ± 0.1 μ m for angled tracks, and resolutions of between 4.4 and 11 μ m for perpendicular tracks, depending on the applied bias voltage. The double sided 3D sensor, which has significantly less charge sharing, was found to have an optimal resolution of 9.0 ± 0.1 μ m for angled tracks, and a resolution of 16.0 ± 0.2 μ m for perpendicular tracks. Based on these studies it is concluded that the Timepix ASIC shows an excellent performance when used as a device for charged particle tracking.