European Organization for Nuclear Research

Over the past few years, interest in a Muon Collider as a potential post-LHC machine has grown significantly. By colliding muons, it is possible to achieve both precision and high energy, overcoming the limitations of synchrotron radiation in conventional lepton colliders. However, the very short muon lifetime at rest requires high beam intensity and fast acceleration rates limiting the collider ring dimensions. These limitations lead to several challenges in the design of superconducting magnets, which must generate high magnetic fields in large apertures to provide shielding from the radiation due to muon decay. This work explores the design of combined function magnets, which are essential to address the neutrino flux issue in straight sections by bending the particles during focusing/defocusing stages. The superconducting material selected for these magnets is REBCO, a High Temperature Superconductor (HTS), with operating temperatures ranging from 4.5 K to 20 K. Various configurations of combined function magnets are studied and simulated using a Python code interfaced with the Finite Element Method (FEM) software ANSYS, employing the sector coil approximation. The goal is to identify feasible designs that can accommodate substantial internal shielding while continuing to provide the high fields and gradients demanded by the lattice optics. To validate the manufacturability of such concepts, a preliminary winding test has been performed using Nb<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_{3}$</tex-math></inline-formula>Sn in a Canted-Cosine-Theta (CCT) geometry. While REBCO represents the most promising HTS conductor for future high-field applications, Nb<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$_{3}$</tex-math></inline-formula>Sn remains one of the most mature options for large accelerator magnets, providing a valuable feasibility benchmark.

During the Long Shutdown 3 of the LHC, scheduled to start in 2026, the interaction regions will be upgraded to increase the integrated luminosity by about one order of magnitude. Among the components to be replaced are the MBRD (Main Bending Recombination Dipole, also known as D2), which are double-aperture magnets providing aligned magnetic fields to steer the two beams into the ATLAS and CMS experiments and subsequently recombine them onto their nominal trajectories. To meet the demanding requirements of the High-Luminosity LHC, a new magnet design was developed by INFN-Genova, featuring a larger aperture, a higher operating field, and innovative solutions to mitigate the strong electromagnetic cross-talk between the apertures while ensuring mechanical integrity against the large repulsive Lorentz forces. The development program included the construction of a 1.6-m model, a full-length prototype, and six series magnets, of which four will be installed in the LHC and two kept as spares. Series production is ongoing at ASG Superconductors, and the first magnet has been successfully cold-tested at CERN. This contribution reports on the main challenges faced during series production and discusses the first test results.

Time-differential perturbed angular correlation (TDPAC) spectroscopy is a nuclear solid-state technique that requires high energy and coincidence-time resolutions from scintillation crystals and photodetectors. Traditionally, photomultiplier tubes (PMTs) have been coupled to LaBr 3 :Ce crystals; however, they have been replaced by Multi Pixel Photon Counters (MPPCs) for TDPAC experiments conducted under external magnetic fields. In this report, we show that, for TDPAC spectroscopy, the performance of the LaBr 3 :Ce-MPPC detector remains stable under magnetic fields up to 8.5 T (in 1 T steps), as evidenced by the unchanged energy and coincidence-time resolutions of the 511 keV peaks from positron–electron (e + -e - ) annihilation in a sealed 22 Na calibration source.

A novel compact extraction system has been developed at CERN to optimize high-current linacs for medical and industrial use. Replacing the traditional LEBT with a 2 cm-long electrode-based design, it enables efficient proton extraction and acceleration to 45 keV. Tested at the Linac4 test stand, both experimental and simulation results confirm its ability to match to the RFQ acceptance with improved beam quality and reduced footprint, offering a viable solution for next-generation compact linacs.

Acquiring and processing longitudinal beam profiles in the CERN injector complex is essential for maintaining high beam quality for both the Large Hadron Collider and fixed-target experiments. This paper describes a new and common framework across the injector chain to continuously monitor longitudinal profiles, based on digitizers connected to wall current monitors. A new software class has been developed using the Front-End Software Architecture framework to improve real-time monitoring of longitudinal beam quality along the whole beam production cycle. The new implementation supports efficient data acquisition with highly flexible configuration options, including per-profile and per-cycle settings management. This acquisition class reduces data transfer time from the hardware and enables simultaneous beam monitoring and optimization for multiple users across the CERN accelerator complex. Beyond the raw data acquisition layer, real-time processing analyses have been developed on the Unified Controls Acquisition and Processing platform to perform bunch length, bunch-by-bunch intensity, and bunch spacing measurements, and tomographic reconstruction of the longitudinal phase space to provide key longitudinal parameters such as momentum spread and emittance. This new monitoring framework paves the way for preparing and executing the filling of the LHC in an automated manner and for optimizing fixed-target cycles for physics users.

A bstract Two fundamentally distinct types of quantities are both called “eikonal” in present amplitudes literature. The unitarity of the S-matrix ensures it can be written as the exponential of a Hermitian operator. The eikonal generator or Magnusian , which is the classical limit of the expectation value of that operator, generates all scattering observables. The leading order classical behavior of the phase of an S-matrix element is called the classical eikonal phase, and it coincides with a classical on-shell action. We demonstrate that the eikonal generator (Magnusian) and the eikonal phase (classical on-shell action) are inequivalent and find the exact general relationship between them. That relationship explains the special case of integrable scattering in which the two do coincide up to a Legendre transformation and explains why such a correspondence fails in general when spin or radiation are included.

Abstract Real-time scattering dynamics in gauge theories are central to high-energy nuclear physics, but they are notoriously hard to access from first principles. In particular, it remains unclear how a simple propagating probe becomes modified and quantum-mechanically mixed with a dense, dynamical target during a collision. In analogy to high-energy nuclear scattering experiments, we study a real-time scattering process between a propagating state and a dense target in 1 + 1-d massive QED. In our setup, we identify three distinct regimes that qualitatively characterize the evolution: for a dilute medium, the incoming probe state evolves nearly ballistically; in an intermediate setting, it traverses the matter, locally exciting it; and for dense targets, one approaches a black-disk limit, where the matter acts as a strong wall potential. Here we show evidence that the probe’s energy loss rate scales linearly with the path length in the medium, and we study how the entanglement entropy reveals the mixing between the probe and medium states. With the goal of one day replicating high-energy nuclear experiments in quantum devices, we briefly discuss how the current tensor network-based simulations can be translated to a quantum simulator.

The increasing demand for ion beams heavier than protons—particularly carbon and helium ions—for cancer therapy has driven the development of advanced accelerator technologies. Although proton therapy is well established, its physical properties limit its effectiveness against certain tumor types, thereby motivating the use of ions with higher linear energy transfer (LET) and greater biological effectiveness. This study presents the design of an Alvarez-type linear accelerator configuration that combines a Quasi-Alvarez Drift Tube Linac (QA-DTL) and a conventional Alvarez Drift Tube Linac (DTL). The proposed systems are intended for accelerating and injecting carbon or helium ions into a cancer therapy synchrotron, as well as accelerating helium ions for radioisotope production. The optimized QA-DTL and DTL structures provide a versatile and efficient solution for future particle therapy facilities, addressing the growing demand for compact, high-performance, and multifunctional accelerator systems. The proposed linac configurations are designed to operate at 352.2 MHz and consist of three sections. For accelerating low-velocity ions, the first section is a QA-DTL, which is the only section powered during the injection of carbon or helium ions (depending on configuration) into the therapy synchrotron at the energy of 5 MeV/u. The QA-DTL is followed by two DTL cavities forming the second and third sections, which further accelerate helium ions to energies of up to 7.1 MeV/u and 10 MeV/u, respectively. The energy of 7.1 MeV/u is chosen because it represents the production threshold of 211At, one of the most promising alpha emitters for targeted alpha therapy.