AI 中文总结
本研究利用CMOS探测器，通过反质子湮灭产生的带电粒子簇监测反质子数量，可降低系统误差，误差约10%。
AI 中文摘要
GBAR实验在AD/ELENA处产生反氢，需要准确知晓入射keV反质子的数量，但这一过程存在挑战。我们使用安装在实验真空室周围的商用CMOS数字相机，通过测量微通道板探测器表面（用于束流成像）上湮灭过程产生的电离粒子，来确定反质子数量。考虑周围材料的预算，我们表明出射带电粒子的多重数符合反质子与静止核子单次湮灭的预期；这些粒子大多处于最小电离区域，但在CMOS像素探测器中能以近100%的效率被探测，且因耗尽层较薄，该装置对背景伽马射线不敏感。得益于高粒度和小像素尺寸，可在密集径迹环境中以良好分辨率、大动态范围内重建数百万次反质子湮灭。通过对非垂直径迹的簇长度研究，估算了耗尽区厚度和有效探测面积，簇长度还可用于监测径迹角度。反质子数量通过CMOS传感器中重建的簇数量，结合相对于GBAR装置最上游位置已知束流强度的校准测量所覆盖的立体角来确定；出射湮灭产物的材料效应通过Monte Carlo（Geant4）计算估算，而微通道板复杂表面的湮灭伪影在该方法中被抵消。该方法大幅降低了系统不确定性，最终绝对反质子数量重建的误差约为10%。
英文摘要
The production of antihydrogen by the GBAR experiment at AD/ELENA requires good knowledge of the number of incident keV antiprotons, which can be problematic. We have used a commercial CMOS digital camera mounted around the experimental vacuum chamber to determine antiproton numbers from ionising particles created in the annihilation process on the surface of microchannel plate detectors which are used for beam imaging. We show that the multiplicity of emerging charged particles is as expected for individual annihilations of antiprotons with nucleons at rest, taking into account the surrounding material budget. Most of those particles are in the minimal ionising regime, but can be detected with nearly 100% efficiency in the CMOS pixel detector, while due to the thin depletion layer the device is insensitive to background gammas. Thanks to the high granularity and small pixel size millions of antiproton annihilations can be reconstructed in a dense tracking environment over a large dynamic range with good resolution. From cluster length studies of non perpendicular tracks the thickness of the depletion zone and effective detection area was estimated. The cluster length also allows for a monitoring of track angles. Antiproton numbers are determined from the number of reconstructed clusters in the CMOS sensor by means of the covered solid angle relative to a calibration measurements with well known beam intensities at the most upstream location of the GBAR apparatus. Material effects on the emerging annihilation products were estimated by Monte Carlo (Geant4) calculations, while annihilation artefacts on the complex surface of a microchannel plate are cancelled out in this approach. This method minimises largely systematic uncertainties, leading to a final error of roughly 10% for the reconstruction of absolute antiproton numbers.
