Measurement of the relative response of small-electrode CMOS sensors at Diamond Light Source

Abstract

This paper outlines the results of investigations into the effects of radiation damage in the mini-MALTA prototype. Measurements were carried out at Diamond Light Source using a micro-focus X-ray beam, which scanned across the surface of the device in 2 µm steps. This allowed the in-pixel photon response to be measured directly with high statistics. Three pixel design variations were considered: one with the standard continuous n − layer layout and front-end, and extra deep p-well and n − gap designs with a modified frontend. Five chips were measured: one unirradiated, one neutron irradiated, and three proton irradiated.

Recent measurements on MiniMALTA, a radiationhard CMOS sensor with small collection electrodesfor ATLAS

“…Coupled with the results from Diamond described in [12], the X-ray irradiations show that MiniMALTA is fully operational after TID above the ALTAS requirement, and efficiencies are expected to be comparable to those of devices without TID.…”

“…There are actually more hits between pixels than in the pixel centers for this sector. The sector with the n-gap substrate and modified front-end had comparable performance, and in both designs the charge collection in the periphery after irradiation has improved with the new substrate and front-end designs [12].…”

“…A more thorough analysis of the test beam is in [12]. In that reference, for the modified sectors of MiniMALTA, proton-irradiated sensors with a total ionizing dose (TID) of 70 MRad have similar photon response to unirradiated and neutron irradiated devices.…”

MALTA: a Monolithic Active Pixel Sensor for tracking in ATLAS

“…In these proceedings, I compare results from two sectors in a neutron irradiated (1e15 n eq /cm 2 ) MiniMALTA sample. A more thorough analysis of the test beam is in [12].…”

X-Ray measurements of radiation hard monolithic CMOS sensors at Diamond Light Source

“…Most recently, the mini-MALTA prototype was developed, implementing design changes which are aimed at improving the pixel performance and achieving higher radiation hardness [3]. In the following, results of an X-Ray test-beam at Diamond Light Source are presented for the different designs and different levels of irradiation [4].…”