4D tracking with ultra-fast silicon detectors

Abstract

The evolution of particle detectors has always pushed the technological limit in order to provide enabling technologies to researchers in all fields of science. One archetypal example is the evolution of silicon detectors, from a system with a few channels 30 years ago, to the tens of millions of independent pixels currently used to track charged particles in all major particle physics experiments. Nowadays, silicon detectors are ubiquitous not only in research laboratories but in almost every high-tech apparatus, from portable phones to hospitals. In this contribution, we present a new direction in the evolution of silicon detectors for charge particle tracking, namely the inclusion of very accurate timing information. This enhancement of the present silicon detector paradigm is enabled by the inclusion of controlled low gain in the detector response, therefore increasing the detector output signal sufficiently to make timing measurement possible. After providing a short overview of the advantage of this new technology, we present the necessary conditions that need to be met for both sensor and readout electronics in order to achieve 4D tracking. In the last section, we present the experimental results, demonstrating the validity of our research path.

Comparison of 35 and 50μm thin HPK UFSD after neutron irradiation up to 6 ⋅ 1015 neq/cm2

“…The fluence evolution of the doping concentration in the multiplication layer and the bulk for the 35 μm thick B35 and 50 μm thick 50D (taken from [14]). The curves are simulations described in [1] based on data of [16].…”

Radiation resistant LGAD design

“…The Boron low-diffusion gain layer shows a higher radiation resistance than that of standard Boron implant, indicating a dependence of the initial acceptor removal mechanism upon the implant density.The LGAD design evolves the standard silicon sensors design by incorporating low, controlled gain [1] in the signal formation mechanism. The overarching idea is to manufacture silicon detectors with signals large enough to assure excellent timing performance while maintaining almost unchanged levels of noise [2].Charge multiplication in silicon sensors happens when the charge carriers (electrons and holes) are in electric fields of the order of E ∼ 300 kV/cm [3]. Under this condition, the electrons (and to less extent the holes) acquire sufficient kinetic energy to generate additional e/h pairs by impact ionization.…”

Pixel detectors ... where do we stand?

“…Sub-ns to ps timing was believed to be very difficult with silicon detectors. So-called low gain avalanche diodes, having mm 2 size patterns, have been developed to cope with this challenge (see also [52] and [53]). In order to minimize time fluctuations in the signal generation process, an amplification structure is realized by a p + implantation right underneath the n ++ electrode ( fig.…”