标题： EAR2中子束在CERN n_TOF设施升级后的特点 显示英文标题

标题： Features of the EAR2 neutron beam following the spallation target upgrade at the n_TOF facility at CERN

摘要： 欧洲核子研究中心 (CERN) 的 n_TOF 设施进行了重大升级，安装了新的散裂靶，旨在提升实验区 1 和 2（EAR1 和 EAR2）中子束线的性能，并启用了新的实验区（NEAR）。由于散裂靶与 EAR2 束线的耦合得到改善，升级后的中子通量和中子能量分辨率显著提高。 本文介绍了升级后的 EAR2 中子束线的调试结果，并验证了 FLUKA 蒙特卡罗模拟结果。本文评估了中子束的主要特性，即中子通量、空间分布和能量分辨率，并与之前的靶进行了比较。中子通量在1 eV以下普遍增加20%，在1 eV至100 keV之间增加40%，在100 keV至10 MeV之间增加50%。 在中子俘获测量的参考位置，测得的束流轮廓宽度为3 cm（半高宽）。新型散裂靶的能量分辨率与之前的相比有显著提高。 此外，FLUKA蒙特卡洛模拟结果与测量的中子通量和轮廓在不确定度范围内具有良好的一致性，并且能量分辨率再现性极佳。 显示英文摘要

摘要： The n_TOF facility at CERN has undergone a major upgrade after the installation of a new spallation target, designed to improve the features of both neutron beamlines at the experimental areas 1 and 2 (EAR1 and EAR2) and the commissioning of a new experimental area (NEAR). Due to improved coupling of the spallation target with the EAR2 beamline, the upgrade resulted in a significantly increased neutron flux and improved neutron energy resolution. This paper presents the results of the commissioning phase that followed to characterise the EAR2 neutron beamline and validate the FLUKA Monte Carlo simulations of the facility. The main features of the neutron beam, namely the neutron flux, spatial profile and energy resolution, are evaluated and compared to the previous target. The neutron flux presents a general increase of 20% below 1 eV, 40% between 1 eV and 100 keV and 50% between 100 keV and 10 MeV. The measured width of the beam profile was 3 cm (FWHM) at the reference position for neutron capture measurements. The energy resolution with the new spallation target shows a significant improvement compared to the previous one. Moreover, FLUKA Monte Carlo simulations present a good agreement with the measured neutron flux and profile within uncertainties, and a remarkable reproduction of the energy resolution.