Timewalk correction for the Timepix3 chip obtained with real particle data

Abstract

In this work we have developed a prototype gaseous pixel detector by combining a micromegas grid with a Timepix3 chip for the readout. The micromegas foil supported by a matrix of pillars about 50 µm high was manually placed on top the chip. By placing a cathode foil above the chip an ionisation detector was created with a drift gap of 13.5 mm.The Timepix3 chip, thanks to the simultaneous measurement of the time-of-arrival (ToA) and charge via time-overthreshold (ToT) allows corrections to remaining timewalk effects, improving further the position resolution along the drift direction. We present the timewalk correction for Timepix3 chip obtained with real data from a particle beam and its impact on the tracking performance. The results obtained show a significant improvement on the position resolution for single-hits and tracks along the drift direction compared to previous experiments. In a previous work [1] we measured the tracking performance of a gaseous pixel detector using the Gossipo2 chip and featuring a high-resolution TDC (1.8 ns) per pixel. The performance of this prototype chip technology led to a significant improvement to the position resolution in the drift direction. Its successor, the Timepix3 chip [2], implements a TDC per pixel with a better resolution of 1.56 ns, which enhances the performance. In addition, the simultaneous measurement of charge via time-overthreshold (ToT) and drift time via time-of-arrival (ToA) allows corrections to remaining timewalk effects, improving further the resolution. These facts encourage the realisation of gaseous pixel detectors based on the Timepix3chip. Therefore we assembled a gaseous pixel detector based on the Timepix3 chip that we called GasPix and installed it in a particle beam. Our aim was to study the correction for the remaining timewalk effects and measure the impact on the tracking performance.

A simulator for Timepix-like pixel front-ends

“…Figure 5 shows the simulated ToA for input charge values ranging from the used threshold level of 2.9 ke-to 10 ke-. The result is consistent with published results [7,8]. Also visible is the effect of the system noise of 80 e-ENC r.m.s, 7 e-r.m.s threshold noise and the long peaking time of the Timepix3 of ~35 ns for low charge inputs.…”

Shot-by-shot 250 kHz 3D ion and MHz photoelectron imaging using Timepix3

“…The position was defined as the center of mass of the individual blobs of triggered pixels. For determination of the ToF, the temporal information of the individual pixels was time-walk corrected by a pixel-based correlation curve between ToT and ToA [91][92][93]. The correlation curve was obtained from electron data for both detectors using the assumption that all electrons arrive at the same time within the resolution of the Timepix3 camera.…”

Spatial and Temporal Detection of Ions Ejected from Coulomb Crystals

“…This effect is explained by the specific response characteristics of the in-pixel amplifiers and thresholding process. 49,50 The relative error introduced by these time-walk effects is not significant for the results in this work, and so no time-walk correction is performed. To illustrate the effect, a representative Ca + peak is shown in Figure S4 in the Supporting Information.…”