In February 2023, two new crystal primary collimators, called TCPCs, were installed in IR7. Crystal collimation will be used as a means to improve the collimation performance for lead ion beams as of 2023. The new devices replace two test horizontal crystal devices used during Run 2 for beam tests. Together with the installation in March 2022, when two vertical TCPC were installed, this intervention successfully completes the baseline upgrade planned by HL-LHC. In addition to the total of four units for the tunnel, two additional TCPC devices were also built that will serve as spare units.

Each TCPC has a 4mm-long crystal bent to a curvature radius of 80m that produces a designed 50 micro-radian transverse kick to halo particles that, if special impinging conditions are respected, are trapped in the potential well of the periodic crystal's lattice structure. The particles are then steered onto, and safely disposed of, by downstream secondary collimators and showers absorbers. The crystal angular alignment with respect to the circulating beam is performed thanks to an interferometric system that stabilises the crystal’s angle to better than 1 micro-radian. The two vertical TCPC were used in 2022 in a dedicated beam test with ion beams at 6.8 Z TeV and provided very promising results, as reported at Chamonix.

By Stefano Redaelli, WP5 Leader, and Mario di Castro, WP5.4 Leader.

Oliver Aberle, Regis Seidenbinder, Quentin Joel Demassieux, Eloise Matheson, Santiago Solis Paiva.

Related photo collection: link.