NA61/SHINE facility at the CERN SPS: beams and detector system

Abstract: NA61/SHINE (SPS Heavy Ion and Neutrino Experiment) is a multi-purpose experimental facility to study hadron production in hadron-proton, hadron-nucleus and nucleus-nucleus collisions at the CERN Super Proton Synchrotron. It recorded the first physics data with hadron beams in 2009 and with ion beams (secondary 7Be beams) in 2011. NA61/SHINE has greatly profited from the long development of the CERN proton and ion sources and the accelerator chain as well as the H2 beamline of the CERN North Area. The latter has recently been modified to also serve as a fragment separator as needed to produce the Be beams for NA61/SHINE. Numerous components of the NA61/SHINE set-up were inherited from its predecessors, in particular, the last one, the NA49 experiment. Important new detectors and upgrades of the legacy equipment were introduced by the NA61/SHINE Collaboration. This paper describes the state of the NA61/SHINE facility - the beams and the detector system - before the CERN Long Shutdown I, which started in March 2013.

• The paper presents NA61/SHINE's design featuring advanced beam technologies and a robust detector system to achieve high-precision hadron measurements.
• It describes sophisticated accelerator chains and precise ion fragmentation techniques that ensure reliable beam control and effective particle identification.
• The study outlines upgraded tracking and time-of-flight systems that enhance particle detection, supporting critical experiments in neutrino and cosmic-ray physics.

NA61/SHINE Facility at CERN SPS: Beams and Detector System

The paper presents a detailed description of the NA61/SHINE facility, a multi-purpose experimental setup dedicated to studying hadron production in various collision types, including hadron-proton, hadron-nucleus, and nucleus-nucleus, at the CERN Super Proton Synchrotron (SPS). The integration of advanced beam technologies and detector systems underscores NA61/SHINE's instrumental role in exploring properties at the onset of deconfinement and providing precise hadron measurements vital for neutrino experiments and simulations of cosmic-ray air showers.

Beams and Accelerator Chains

The paper details the intricately developed CERN proton and ion sources as well as the accelerator chain, which have undergone substantial advancements to foster the experimental objectives of NA61/SHINE. The importance of the North Area H2 beamline, now modified to function as a fragment separator essential for Be beam production, is emphasized. The document meticulously outlines the proton and ion acceleration mechanisms, including the use of specialized ion sources and the sequence of acceleration through various CERN facilities culminating in extraction to the NA61/SHINE experiment.

Ion Fragmentation and Beamlines

A significant aspect is the description of the ion fragmentation process, particularly the production of $^7$Be ions through Pb fragmentation. The beamline’s ability to differentiate between various ion species via rigidity selection highlights its precision. This is accompanied by robust detector mechanisms for beam identification, including Cherenkov counters and Z-detectors, ensuring NA61/SHINE’s capability to maintain high precision in ion beam experiments.

Detector System

NA61/SHINE inherits and upgrades components from predecessor experiments, notably NA49, including its Time Projection Chambers (TPCs) that form the backbone of the tracking system. The enhanced TPC set-up, embedded within high-field superconducting magnets, is pivotal in providing high-resolution momentum measurements and particle identification. The inclusion of He beam pipes is a noteworthy development, significantly reducing secondary electron interference.

Additional detectors such as the Low Momentum Particle Detector (LMPD) designated for centrality tagging in p+Pb collisions and the Projectile Spectator Detector (PSD) for spectator energy measurements are described. The PSD's design ensures precise centrality measurements critical for fluctuation studies in nuclei collisions.

Time of Flight Systems

The diverse applications of ToF detectors embedded within the facility cater to extended particle identification and resolution. The document provides an overview of inherited and newly constructed ToF systems, emphasizing advancements like the Forward ToF (ToF-F) wall, crucial for addressing gaps in lower energy hadron detection.

Data Acquisition and Control Systems

The readout electronics and DAQ systems are pivotal for event data synchronization across various detector subsystems, ensuring robustness in real-time measurement and subsequent analysis. The paper also details the Detector Control System's command logic structure, reinforcing NA61/SHINE’s capabilities in monitoring and managing operational parameters efficiently.

Outlook and Implications

The paper identifies ongoing upgrades and future plans for the NA61/SHINE facility, including additional detector constructions and enhanced readout systems. These developments are set to expand the facility's physics goals, promising advancements in understanding hadronic processes and enriching experimental contributions to high-energy physics.

In conclusion, NA61/SHINE's experimental arrangements, thoroughly detailed in this paper, attest to its strategic design catering to high-precision measurements essential for hadron collision studies. The facility's capability to serve both theoretical explorations of deconfinement properties and practical needs for neutrino beam calculations underscores its vital role within CERN's SPS ecosystem.