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The RD50-MPW4 is the latest HV-CMOS pixel sensor from the CERN-RD50-CMOS working group, designed to evaluate the HV-CMOS technology in terms of spatial resolution, radiation hardness and timing performance. Fabricated by LFoundry using a 150nm process, it features an improved architecture to mitigate crosstalk, which has been an issue with the predecessor RD50-MPW3, allowing more sensitive threshold settings and full matrix operation. Enhancements include separated power domains for peripheral and in-pixel digital readout, a new backside-biasing step, and an improved guard ring structure supporting biasing up to 500V, significantly boosting radiation hardness. Laboratory measurements and test beam results presented in this paper show significant improvements over its predecessor regarding noise behavior, spatial resolution, and efficiency., Comment: Preprint version of Proceedings of Pisa meeting 2024

Results in this paper present an in-depth study of time resolution for active pixels of the RD50-MPW2 prototype CMOS particle detector. Measurement techniques employed include Backside- and Edge-TCT configurations, in addition to electrons from a $^{90}\mathrm{Sr}$ source. A sample irradiated to $5\cdot 10^{14}\,\mathrm{n}_\mathrm{eq}/\mathrm{cm}^2$ was used to study the effect of radiation damage. Timing performance was evaluated for the entire pixel matrix and with positional sensitivity within individual pixels as a function of the deposited charge. Time resolution obtained with TCT is seen to be uniform throughout the pixel's central region with approx. $220\,\mathrm{ps}$ at $12\,\mathrm{ke}^-$ of deposited charge, degrading at the edges and lower values of deposited charge. $^{90}\mathrm{Sr}$ measurements show a slightly worse time resolution as a result of delayed events coming from the peripheral areas of the pixel.

The DESY II Test Beam Facility is a key infrastructure for modern high energy physics detector development, providing particles with a small momentum spread in a range from 1 to 6 GeV to user groups e.g. from the LHC experiments and Belle II as well as generic detector R&D. Beam telescopes are provided in all three test beam areas as precise tracking reference without time stamping, with triggered readout and a readout time of > 115 $\mu$s. If the highest available rates are used, multiple particles are traversing the telescopes within one readout frame, thus creating ambiguities that cannot be resolved without additional timing layers. Several upgrades are currently investigated and tested: Firstly, a fast monolithic pixel sensor, the TelePix, to provide precise track timing and triggering on a region of interest is proposed to overcome this limitation. The TelePix is a 180 nm HV-CMOS sensor that has been developed jointly by DESY, KIT and the University of Heidelberg and designed at KIT. In this publication, the performance evaluation is presented: The difference between two amplifier designs is evaluated. A high hit detection efficiency of above 99.9 % combined with a time resolution of below 4 ns at negligible pixel noise rates is determined. Finally, the digital hit output to provide region of interest triggering is evaluated and shows a short absolute delay with respect to a traditional trigger scintillator as well as an excellent time resolution. Secondly, a fast LGAD plane has been proposed to provide a time resolution of a few 10 ps, which is foreseen to drastically improve the timing performance of the telescope. Time resolutions of below 70 ps have been determined in collaboration with the University of California, Santa Barbara.