Advanced hybrid sensors tested at CERN
by Iván Vila Álvarez (Instituto de Física de Cantabria - CSIC) &
Anna Macchiolo (Max-Planck-Institut für Physik), 20/12/2016
From left to right: Marcos Fernández, Javier González, Richard Jarmillo and Iván Vila at SPS H6 line (Image: Iván Vila Álvarez)
The AIDA-2020 Networking Activity (NA) on advanced hybrid sensors (WP7) aims to pave the way for a new generation of hybrid sensor technologies for recording where particles interact (also known as vertexing) and pinning the timing down with ultrahigh precision. WP7 members conducted a successful beam test on the sensors which aim to help meet the requirements of the high-luminosity LHC and CLIC colliders.
The primary goal of WP7 is to assess sensors through detailed device simulations and experimental characterization. The sensors will be produced in dedicated Multi Project Wafer (MPW) manufacturing runs on the three technologies under consideration: planar pixel sensors with active edges, pixel detectors with cylindrical electrodes that penetrate the silicon substrate (so called 3D detectors) and Low Gain Avalanche Detectors (LGAD).
A test beam at the CERN Super Proton Synchrotron (SPS) H6 line was carried out in July 2016 to test the pre-production prototypes of the three targeted technologies. The prototypes were produced by both foundries contributing to this work package (CSIC-CNM and FBK) and external foundries (CiS, ADVACAM). The groups of INFN (Florence), MPI (Munich) and CSIC-IFCA (Santander) were involved in the actual device characterization.
Planar pixel sensors of 100 and 130 μm thickness produced at FBK and interconnected to the CMS PSI46dig chips were tested before and after irradiation. An ad-hoc set-up was assembled to deliver clock and preselected synchronous trigger for the chips, and full integration of the PSI46dig in EUDAQ was achieved.
Planar pixel sensors with active edges, manufactured at ADVACAM, were tested, after interconnection to the ATLAS FE-I4 chip. The hit efficiency in the area between the last pixel column and the dicing line was determined for sensors of 50, 100 and 150 μm thickness. The 100-and 150-μm sensors had very high hit efficiency up to the sensor edge while the 50-μm-thick sensors were only sensitive up to the last pixel implant.
The initial characterization for the n-in-p sensors with columnar electrodes (3D sensors) was carried out in devices manufactured at CNM-CSIC with cell sizes of both 50x50x230 μm3 and 25x100x230 μm3, and proton-irradiated up to a fluence of 1016 neq/cm2 at CERN. The sensors were read-out in a strip-like configuration with the pixel cells shorted with a metal strip along the direction of the longest pixel base side, resulting in a strip pitch of 50 and 25 microns for the two elementary pixel cell studied.
In addition, the MIP response and tracking performance of a strip-like p-in-p LGAD sensor (i-LGAD) manufactured at CNM was studied for the first time. An i-LGAD sensor follows the original design of the LGAD detector but differs with the segmentation of the ohmic contact, making the i-LGAD position-sensitive and able to determine the hit position of MIP particles in the detector. Here, a 300-μm-thick i-LGAD with a pitch of 160 μm was characterized.
For the first time, signal amplification was observed on this novel kind of device with a signal gain of ~3, which translates into a signal-to-noise ratio of about 50; which is 250% larger than the expected value for a standard PIN strip with the same thickness. This is a very promising result towards a very thin strip LGAD-based sensor presenting both excellent tracking and timing performance.