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Scientific Committee Paper
Report number	CERN-LHCC-2024-014 ; LHCC-I-040-ADD-1
Title	Addendum to the AdvancedSND LoI
Project Manager/Technical Coordinator	De Lellis, Giovanni; Jacobsson, Richard
Author(s)	Abbaneo, D ; Albanese, R ; Alexandrov, A ; Alicante, F ; Androsov, K ; Anokhina, A ; Asada, T ; Asawatangtrakuldee, C ; Ayala Torres, M A ; Battilana, C ; Bay, A ; Bertocco, A ; Bertone, C ; Betancourt, C ; Bick, D ; Biswas, R ; Blanco Castro, A ; Boccia, V ; Bogomilov, M ; Boiano, A ; Bonacorsi, D ; Bonivento, W M ; Bordalo, P ; Boyarsky, A ; Bud, T ; Buonocore, L ; Buontempo, S ; Campanelli, M ; Camporesi, T ; Canale, V ; Centanni, D ; Cerutti, F ; Chernyavskiy, M ; Choi, K -Y ; Cholak, S ; Cindolo, F ; Climescu, M ; Conaboy, A P ; Crespo-Lopez, O ; Dallavalle, G M ; Davino, D ; de Bryas, P T ; De Lellis, G ; de Magistris, M ; De Roeck, A ; De Rùjula, A ; De Simone, D ; Di Crescenzo, A ; Di Ferdinando, D ; Di Luca, S ; Di Meo, P ; Dinc, C ; Donà, R ; Durhan, O ; Fabbri, F ; Fedotovs, F ; Ferrillo, M ; Fiorillo, A ; Fresa, R ; Funk, W ; Gaignant, C ; Garay Walls, F M ; Golovatiuk, A ; Golutvin, A ; Graverini, E ; Guiducci, L ; Guler, A M ; Guliaeva, V ; Haefeli, G J ; Hagner, C ; Helo Herrera, J C ; Herty, A ; van Herwijnen, E ; Iengo, P ; Ilieva, S ; Infantino, A ; Iuliano, A ; Jacobsson, R ; Jeangros, H ; Kamiscioglu, C ; Kauniskangas, A M ; Khalikov, E ; Kim, S H ; Kim, Y G ; Klioutchnikov, G ; Komatsu, M ; Konovalova, N ; Kuleshov, S ; Krzempek, L ; Lacker, H M ; Lantwin, O ; Lasagni Manghi, F ; Lauria, A ; Lee, K Y ; Lee, K S ; Lelong, P ; Lerner, G ; Lo Meo, S ; Loschiavo, V P ; Marcellini, S ; Margiotta, A ; Marion, A -P ; Mascellani, A ; Mei, F ; Miano, A ; Mikulenko, A ; Montesi, M C ; Navarria, F L ; Nuntiyakul, W ; Ogawa, S ; Okateva, N ; Osborne, J ; Ovchynnikov, M ; Paggi, G ; Pal, K ; Panigoni, J ; Park, B D ; Passeggio, G ; Pazzini, J ; Pelletier, S ; Perez Ornedo, M ; Perrotta, A ; Podgrudkov, D ; Polukhina, N ; Prota, A ; Prouteau, O ; Quercia, A ; Ramos, S ; Reghunath, A ; Roganova, T ; Ronchetti, F ; Rottoli, L ; Rovelli, T ; Ruchayskiy, O ; Ruf, T ; Sabate Gilarte, M ; Sadykov, Z ; Samoilov, M ; Sanchez Galan , F ; Scalera, V ; Schmidt-Parzefall, W ; Schneider, O ; Sekhniaidze, G ; Serra, N ; Shaposhnikov, M ; Shevchenko, V ; Shchedrina, T ; Shchutska, L ; Shibuya, H ; Siroli, G P ; Sirri, G ; Soares, G ; Sohn, J Y ; Soto Sandoval, O J ; Spurio, M ; Starkov, N ; Steggemann, J ; Szewczyk, M ; Timiryasov, I ; Tioukov, V ; Tramontano, F ; Trippl, C ; Uluwita, A ; Ursov, E ; Ustyuzhanin, A ; Vankova-Kirilova, G ; Vasquez, G ; Vendeuvre, C ; Verguilov, V ; Viegas Guerreiro Leonardo, N ; Vilela, C ; Visone, C ; Wanke, R ; Yaman, E ; Yang, Z ; Yazici, C ; Yoon, C S ; Zaffaroni, E ; Zamora Saa, J ; Zanetti, M
Corporate author(s)	CERN. Geneva. The LHC experiments Committee ; LHCC
Series	(Letter of Intent)
Submitted by	[email protected] on 10 Sep 2024
Subject category	Detectors and Experimental Techniques
Abstract	Over the six months since the submission of the AdvSND LoI \cite{ADVSND_LOI}, the Collaboration has been intensively discussing with the CERN civil engineering team and the High Luminosity LHC (HL LHC) planning officers to fully understand the constraints related to the civil engineering modifications required for TI18. These modifications are necessary to optimize the physics performance of the AdvSND detector and profit of the LHC High-luminosity. Through these discussions, it became evident that the excavation of the TI18 floor must be limited to comply with specific boundaries. Exceeding these boundaries could compromise the tunnel's structural stability, necessitating extensive excavation to restore the integrity of the concrete structures. Additionally, substantial temporary mechanical reinforcements would be required to ensure stability during construction. Addressing these structural stability concerns would make it impossible to meet the schedule constraints of the HL LHC. Given these constraints, the following decisions and modifications have been made compared to the original Letter of Intent. This document outlines these changes in detail

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