Köln 2025 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 43: Instrumentation IX

HK 43.1: Group Report

Thursday, March 13, 2025, 14:00–14:30, SR Exp1A Chemie

Material budget imaging for mockup samples of the ALICE ITS3 with an electron beam — •Simon Groß-Bölting for the ALICE Germany collaboration — Physikalisches Institut, Heidelberg, Deutschland

During the Long Shutdown 3, ALICE will replace the inner barrel of its ITS2 detector with the ITS3, which features curved, ultra-thin silicon sensors supported by ultra-light carbon foam. The ITS3 aims for an average material budget of 0.09% in its first layer within a pseudorapidity range |η| < 1.

To study scattering caused by the carbon foam, a mockup was tested using an electron scattering telescope optimized for angular resolution. Scattering angle distributions were analyzed by fitting the inner 98% with a Gaussian, and the material budget was inferred using the Highland formula. Position-based momentum calculations, accounting for momentum gradients in the test beam, enhanced accuracy and eliminated the need for a scaling factor, enabling the creation of a two dimensional material budget map.

The measured material budget for the "half-ring" matched theoretical predictions, while deviations in the "longeron" were linked to excess glue, later confirmed by CT scans.

Keywords: Material budget imaging; ITS3; ALICE; electron tomography