Salami, R; Poley, L; Affolder, K; Affolder, T; Bayer, L; Crick, B; Duden, E; Dyckes, IG; Fadeyev, V; Fortman, A; Federič, P; Franconi, L; Gignac, M; Gupta, S; Hallford, J; Helling, C; Hill, E; Hu, M; Kroll, J; Kumari, P; Lacasta, C; Levagood, M; Lopez, H; Morelos-Zaragoza, L; Moshe, MR; Petersen, A; Platero, V; Rajagopalan, AD; Sitnikova, L; Solaz, C; Soldevila, U; Speers, P; Nieuwenhuizen, GV; Wang, AZ, Quality concerns caused by quality control — deformation of silicon strip detector modules in thermal cycling tests,
Journal of Instrumentation, vol. 20 no. 03
(March, 2025),
pp. P03004-P03004, IOP Publishing [doi] .
Abstract:
Abstract
The ATLAS experiment at the Large Hadron Collider (LHC) is
currently preparing to replace its present Inner Detector (ID) with
the upgraded, all-silicon Inner Tracker (ITk) for its
High-Luminosity upgrade (HL-LHC). The ITk will consist of a
central pixel tracker and the outer strip tracker, consisting of
about 19,000 strip detector modules. Each strip module is assembled
from up to two sensors, and up to five flexes (depending on its
geometry) in a series of gluing, wirebonding and quality control
steps. During detector operation, modules will be cooled down to
temperatures of about -35 ∘C (corresponding to the
temperature of the support structures on which they will be mounted)
after being initially assembled and stored at room temperature. In
order to ensure compatibility with the detector's operating
temperature range, modules are subjected to thermal cycling as part
of their quality control process. Ten cycles between
-35 ∘C and +40 ∘C are performed for each
module, with full electrical characterisation tests at each high and
low temperature point. As part of an investigation into the stress
experienced by modules during cooling, it was observed that modules
generally showed a change in module shape before and after thermal
cycling. This paper presents a summary of the discovery and
understanding of the observed changes, connecting them with excess
module stress, as well as the resulting modifications to the module
thermal cycling procedure.