UA9
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| UA9 | |
|---|---|
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| Name | UA9 |
| Location | CERN, Meyrin, Switzerland |
| Established | 2009 |
| Focus | Crystal-based beam collimation, channeling, volume reflection |
| Operators | CERN, INFN, University of Geneva |
UA9
The UA9 experiment at CERN investigated crystal-assisted beam manipulation using bent silicon crystals for hadron beam collimation and extraction in accelerator facilities. Located in the Super Proton Synchrotron region, UA9 combined expertise from CERN and numerous European institutions to test concepts relevant to the Large Hadron Collider and future machines. The collaboration integrated instrumentation, accelerator physics, and materials science to demonstrate channeling, volume reflection, and coherent scattering of high-energy protons and ions.
Overview
UA9 aimed to explore coherent interactions between charged particles and oriented crystalline lattices to improve beam loss control in high-energy accelerators. The project tested bent silicon and germanium crystals as primary collimators to deflect halo particles into secondary absorbers, reducing activation of accelerator components such as those in the Super Proton Synchrotron and feeding into strategies for the Large Hadron Collider. Key physics phenomena studied included planar channeling, quasi-channeling, volume reflection, and multiple volume reflection in bent lattices under conditions of the CERN SPS beam. The collaboration addressed challenges of crystal mounting, alignment, radiation hardness, and diagnostics vital to applications at facilities like Fermilab or proposals for future colliders.
Experimental Setup
UA9 installed a compact experimental facility in the 60 GeV–400 GeV proton environment of the SPS North Area and the SPS extraction line, integrating beam instrumentation and vacuum equipment from partnering laboratories. The setup employed goniometers to orient bent single-crystal silicon devices with microradian precision relative to the circulating beam, positioning systems designed with contributions from groups at INFN, CERN mechanical engineering, and university accelerator laboratories. Detection systems included scintillators, Cherenkov counters, Medipix pixel detectors, and beam loss monitors developed with teams from University of Geneva, Paul Scherrer Institute, and IHEP. Secondary absorbers composed of tungsten or copper and diagnostics such as Timepix trackers allowed tracking of deflected halo particles and measurement of deflection angles, channeling efficiencies, and induced activation of nearby components.
Beam Tests and Operations
Beam campaigns were conducted during dedicated runs and parasitic operation periods in the SPS cycle, involving proton beams at various energies and occasionally low-intensity ion or antiproton tests coordinated with accelerator divisions at CERN. Operations required synchronization with the CERN Accelerator Complex schedule and integration with safety systems overseen by the SPS operators and beam instrumentation groups. Goniometer scans explored angular acceptance windows for planar channeling and volume reflection, while multi-turn beam dynamics were evaluated with loss maps and collimation simulations from collaborating accelerator physics groups. Teams compared experimental loss distributions with computational models using codes developed at CERN, INFN, and partner universities, enabling iterative improvements to crystal geometry and mount design.
Results and Publications
UA9 produced experimental demonstrations of high channeling efficiencies for bent silicon crystals, robust volume reflection behaviors across wide angular ranges, and evidence for multiple volume reflection enhancing deflection performance. Measurements quantified deflection angles, channeling acceptance, and survival rates under sustained irradiation, informing theoretical models from lattice dynamics and particle-matter interaction research groups. Results were disseminated through conference proceedings at venues such as International Particle Accelerator Conference, European Physical Society meetings, and publications in journals supported by community publishers, with authorship spanning CERN, INFN, University of Geneva, Paul Scherrer Institute, and other institutes. Notable outputs included detailed beam loss maps, comparisons between experimental data and simulation frameworks, and engineering reports guiding the deployment of crystal collimation systems.
Applications and Impact
Outcomes from UA9 influenced collimation strategies considered for the Large Hadron Collider upgrade programs and proposals for next-generation machines, where reducing component activation and improving beam halo control are critical for reliable operation. Crystal-assisted extraction concepts informed designs for fixed-target experiments at facilities such as SPS Fixed Target programs and potential implementations at Fermilab Main Injector or proposed Future Circular Collider studies. The experiment advanced detector technologies (e.g., Timepix/Medipix arrays) and precision mechanics applicable to other accelerator instrumentation projects, while training early-career scientists and engineers who later contributed to initiatives at CERN and partner laboratories. The UA9 legacy includes validated simulation tools, protocols for in situ crystal alignment, and evidence supporting incorporation of bent-crystal elements in strategic accelerator upgrade roadmaps.
Collaborations and Funding
The UA9 collaboration comprised research groups and institutes across Europe and beyond, including CERN, INFN, University of Geneva, Paul Scherrer Institute, Budker Institute of Nuclear Physics, and multiple university departments specializing in accelerator physics and materials science. Funding and in-kind contributions derived from national research agencies such as INFN, European project frameworks, and institutional resources at participating laboratories. Technical contributions—crystal fabrication, detector development, mechanics, and modelling—were coordinated through memoranda of understanding among partners, while oversight and beam time allocation were managed in cooperation with CERN accelerator committees and the SPS machine coordinators.