In the NUMEN Experiment, Double Charge Exchange (DCE) reactions will be studied to get very precise measurements of their cross sections and final state levels. The interest for these reactions lies in the possibility for some nuclides to have DCE with initial and final states identical to those of the Neutrinoless Double β-Decay. To reach a good precision in the energy measurements, high statistics is needed and severe constraints about the target thickness must be satisfied. A 50 μA intense ion beam will provide the desired statistics, while posing the problem of dissipating the massive heat generated in the target. It is therefore necessary to design a suitable cooling system, which must affect the particles’ energy as little as possible. Said energy is already influenced by the current setup. The Superconducting Cyclotron (SC) and the MAGNEX Spectrometer introduce an error on the particles’ energy by 1/1000th (FWHM value) of its average energy. In the target, the main sources of error are straggling of projectiles and reaction products, and the dispersion effect. Both closely depend on the target thickness, which must be of the order of few hundred nanometres. In addition, the two effects are worsened if the target thickness is not uniform. The solution to these problems has been found by backing the target isotope with relatively thin substrate of Highly Oriented Pyrolytic Graphite (HOPG). Its thermodynamic properties fit the cooling requirements and can be as thin as 450 μg cm−2. The further straggling suffered by the ejectiles is tolerable, falling within the resolution requirements. Samples are deposited by using Electron Beam Evaporation: results obtained for Sn and Te are checked by Scanning Electron Microscopy (SEM). A quantitative evaluation of the samples’ thickness has been performed by Alpha-Particle Transmission (APT) and Rutherford Backscattering Spectrometry (RBS) measurements. A Monte Carlo code has been implemented to estimate the ejectiles energy distribution using the experimental measurements as input. Results from characterization and simulations help in optimizing the target thickness and the energy resolution of reaction products.

中文翻译：

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在 NUMEN 实验中评估目标非均匀性和色散对能量测量分辨率的影响

在 NUMEN 实验中，将研究双电荷交换 (DCE) 反应，以非常精确地测量其横截面和最终状态水平。这些反应的兴趣在于某些核素可能具有初始和最终状态与无中微子双 β-衰变相同的 DCE。为了在能量测量中达到良好的精度，需要高统计量并且必须满足对目标厚度的严格限制。50 μA 的强离子束将提供所需的统计数据，但会带来目标产生的大量热量的消散问题。因此，有必要设计一个合适的冷却系统，该系统必须尽可能少地影响粒子的能量。所述能量已经受到当前设置的影响。超导回旋加速器 (SC) 和 MAGNEX 光谱仪将粒子能量引入其平均能量的 1/1000（FWHM 值）误差。在目标中，误差的主要来源是弹丸和反应产物的散乱以及分散效应。两者都密切依赖于目标厚度，目标厚度必须在几百纳米的数量级。此外，如果目标厚度不均匀，这两种影响就会恶化。通过使用相对较薄的高取向热解石墨 (HOPG) 基材支撑目标同位素，已经找到了解决这些问题的方法。其热力学特性符合冷却要求，可薄至 450 μg cm-2。弹射物的进一步散乱是可以忍受的，符合分辨率要求。通过使用电子束蒸发沉积样品：通过扫描电子显微镜 (SEM) 检查 Sn 和 Te 获得的结果。通过阿尔法粒子透射 (APT) 和卢瑟福背散射光谱 (RBS) 测量对样品的厚度进行了定量评估。已实施蒙特卡罗代码以使用实验测量作为输入来估计弹射物能量分布。表征和模拟的结果有助于优化目标厚度和反应产物的能量分辨率。已实施蒙特卡罗代码以使用实验测量作为输入来估计弹射物能量分布。表征和模拟的结果有助于优化目标厚度和反应产物的能量分辨率。已实施蒙特卡罗代码以使用实验测量作为输入来估计弹射物能量分布。表征和模拟的结果有助于优化目标厚度和反应产物的能量分辨率。