20 ps Time Resolution with a Fully-Efficient Monolithic Silicon Pixel Detector without Internal Gain Layer

Abstract

A: A second monolithic silicon pixel prototype was produced for the MONOLITH project. The ASIC contains a matrix of hexagonal pixels with 100 µm pitch, readout by a low-noise and very fast SiGe HBT frontend electronics. Wafers with 50 µm thick epilayer of 350 Ωcm resistivity were used to produce a fully depleted sensor. Laboratory and testbeam measurements of the analog channels present in the pixel matrix show that the sensor has a 130 V wide bias-voltage operation plateau at which the efficiency is 99.8%. Although this prototype does not include an internal gain layer, the design optimised for timing of the sensor and the front-end electronics provides a time resolutions of 20 ps.

Testbeam results of irradiated SiGe BiCMOS monolithic silicon pixel detector without internal gain layer

“…detection efficiency and time resolution of this prototype was measured [16] at the CERN SPS teastbeam facility with minimum ionising particles, and the time resolution as a function of the deposited charge was measured [17] with a femtosecond laser. Several samples of this ASIC were irradiated at the CYRIC facility [18] in Japan with 70 MeV protons up to a fluence of 1 × 10 16 n eq /cm 2 .…”

“…Several samples of this ASIC were irradiated at the CYRIC facility [18] in Japan with 70 MeV protons up to a fluence of 1 × 10 16 n eq /cm 2 . The time jitter of the single-ended output of the analog pixels was measured using a 90 Sr radioactive source [19]. In this paper, we present the efficiency and time resolution before and after proton irradiation measured with this prototype without gain layer using a beam of pions of 120 GeV/c at the CERN SPS.…”

“…Given the limited time availability during the testbeam experiment, data were taken only with four irradiated boards out of the seven characterised in [19]. In addition, data were taken also with the board not irradiated previously characterised in [16].…”

“…Given the limited time availability during the testbeam experiment, data were taken only with four irradiated boards out of the seven characterised in [19]. In addition, data were taken also with the board not irradiated previously characterised in [16]. Table 1 gives a summary of the power density of the frontend and of the sensor bias voltage of the 18 datasets taken at the testbeam.…”

“…A second prototype of the MONOLITH project containing an improved electronics [16] was produced in 2022. As for the first prototype, the new device contains four pixels where the amplifier was connected to an analog driver and could be read directly by an oscilloscope.…”