靶前高功率质子束束斑成像研究

高功率散裂中子源的打靶质子束流功率一般为百kW到几MW，质子加速器的特点决定靶前质子束流的束斑分布具有一定的不确定性。为了减少打靶束流功率密度，束流传输系统通常还采取一些均匀化束斑的措施，这更增加了靶前束斑形状和密度分布的不确定性。精确测量靶前束斑分布对于高功率散裂靶的稳定运行至关重要。本项目在国际上首次提出基于小孔成像原理的高功率质子束靶前束斑成像研究，利用散裂靶面上反角出射的次级光子或者中子，在几十米外对靶前质子束斑实现快速间接成像，对二维束斑的形状和密度分布进行实时监测。新测量方法根据探测系统需要可以灵活调节准直孔尺寸和测量距离控制测量流强，测量系统远离高功率靶的强辐射区。打靶束流功率越高，此方法越有优势。克服发光涂层成像和多丝束流剖面测量系统寿命或维护的局限性。本项目为靶前束斑监测提出了新思路，为现有具备条件或者未来新建的高功率散裂源靶前束斑测量提供新的解决方案。

The proton beam power of the high-power spallation neutron source is generally from 100 kW to several MW. The characteristics of proton accelerators determine that the beam-spot distribution of the proton beam on target has certain uncertainty. To reduce the beam power density on target, the beam transport system usually takes some measures to homogenize the beam spot, which further increases the uncertainty of the shape and density of the beam distribution on target. Accurate measurement of the beam-spot distribution on target is critical for the stable operation of the high-power spallation target. In the world, this project first proposes a high-power proton beam spot imaging on a target based on the principle of pinhole imaging. Using the secondary photons or neutrons emitted from the backward angle of the spallation target. The fast indirect imaging for the beam spot is achieved at a distance of tens of meters away from the target. And the two-dimensional shape and density distribution of the beam spot is monitored in real time. The new measurement method can flexibly adjust the pinhole size and measurement distance to control the secondary-particle flux intensity according to the needs of detection system. The detection system is away from the high-radiation target area. The higher the power of the beam on target is, the more advantageous this method is. The new imaging method will overcome the limitations of lifetime or maintenance for the luminescent coating imaging and multi-wire beam profile measurement system. This project proposes a new idea for the beam spot monitoring on target and provides a new solution for the existing high-power spallation source or much higher-power spallation source to be constructed in the future.