Speaker
Description
This work presents a detailed study of the timing performance and its spatial variation within the pixel of planar sensors, using the high-resolution TimePix4 beam telescope for precise, track-referenced measurements. Sensors of 200, 100, and 50 um thickness were coupled to the trigger-less TDCpix ASIC with 100 ps timestamping, originally developed for the NA62 GigaTracker at CERN. Tests were performed at the Super Proton Synchrotron H8 beamline, where the TimePix4 telescope provided tracks with ~2 um spatial resolution. Hardware-level synchronization between the telescope and TDCpix combined with large hybrid pixel pitch of 300 um enabled accurate pixel-level timing studies and made it easier to observe and characterise timing non-uniformity.
Dependencies of the mean matrix time resolution on bias voltage and discriminator threshold were measured for each sensor thickness. Since TDCpix is optimised for charge deposition in a 200 um sensor, for thinner hybrids runs with rotated devices were conducted. The rotation increases hadron path length in material which improves charge deposition and enables reasonable comparison between sensors of different thicknesses. The results show better time resolution of thinner hybrids down to ~90 ps. Combining testbeam results with laboratory ASIC calibration allowed extraction of intrinsic sensor time resolution, reaching values below 50 ps in good agreement with theoretical expectations.
A key focus of the study was the spatial dependence of time resolution within a pixel. A dedicated space-time alignment algorithm was developed to integrate telescope tracks with TDCpix data, enabling intra-pixel maps of Time-of-Arrival and time resolution with sub-micron precision. These maps reveal non-uniform timing behavior correlated with the analytical solution for the weighting field of the pixel electrode, showing up to 100 ps variations in charge collection time and tens of ps differences in time resolution. The results highlight the significant influence of the weighting field on intra-pixel timing uniformity, particularly when the pixel pitch approaches the sensor thickness, underscoring the importance of optimized electrode design for future development of fast timing detectors.
| Type of presentation (in-person/online) | in-person presentation |
|---|---|
| Type of presentation (I. scientific results or II. project proposal) | I. Presentation on scientific results |
