Journal ArticleTechnical design report for the CODEX- <i>β</i> demonstratorAielli, Giulio; Alimena, Juliette; Balcarcel-Salazar, Saul; Beacham, James; Haim, Eli Ben; Burucs, András Barnabás; Cardarelli, Roberto; Charles, Matthew J; Vidal, Xabier Cid; Roeck, Albert De; Dey, Biplab; Dobrescu, Silviu; Durmus, Ozgur; Elashri, Mohamed; Gligorov, Vladimir V; Suarez, Rebeca Gonzalez; Gorordo, Thomas; Gray, Zarria; Henderson, Conor; Henry, Louis; Ilten, Philip; Johnson, Daniel; Kautz, Jacob; Knapen, Simon; Liu, Bingxuan; Liu, Yang; Soliño, Saul López; Pérez, Pablo_Eduardo Menéndez-Valdés; Mombächer, Titus; Nachman, Benjamin; Northacker, David T; Nowak, Gabriel M; Papucci, Michele; Pásztor, Gabriella; Rial, Eloi Pazos; Martínez, María Pereira; Peters, Michael; Pfaller, Jake; Pizzimento, Luca; Casasús, Máximo Pló; Rassati, Gian Andrea; Robinson, Dean J; Fernández, Emilio_Xosé Rodríguez; Sahoo, Debashis; Simsek, Sinem; Sokoloff, Michael D; Subash, Joeal; Suresh, Aditya; Swallow, Paul; Swanson, James; Upadhyay, Abhinaba; Vari, Riccardo; Sierra, Carlos Vázquez; Veres, Gábor; Watson, Nigel; Wilkinson, Michael K; Williams, Michael; Winkler, EleanorThe_CODEX-b_collaboration<title>Abstract</title> <p>The CODEX-<italic>β</italic>apparatus is a demonstrator for the proposed future CODEX-b experiment, a long-lived-particle detector foreseen for operation at IP8 during HL-LHC data-taking. The demonstrator project, intended to collect data in 2025, is described, with a particular focus on the design, construction, and installation of the new apparatus.</p>JINST2025-07-0110621402Journal of Instrumentation2007T070071748-0221https://doi.org/10.1088/1748-0221/20/07/T070072209769National Science Foundation