The emission of muonium ($\mu^+e^-$) atoms into vacuum from silica aerogel with laser ablation on its surface was studied with various ablation structures at room temperature using the surface muon beams at TRIUMF and Japan Proton Accelerator Research Complex (J-PARC). Laser ablation was applied to produce holes or grooves with typical dimensions of a few hundred $\mu$m to a few mm, except for some extreme conditions. The measured emission rate tends to be higher for larger fractions of ablation opening and for shallower depths. More than a few ablation structures reach the emission rates similar to the highest achieved in the past measurements. The emission rate is found to be stable at least for a couple of days. Measurements of spin precession amplitudes for the produced muonium atoms and remaining muons in a magnetic field determine a muonium formation fraction of $(65.5 \pm 1.8)$% and indicate that the polarization of muonium atoms is preserved in vacuum. A projection of the emission rates measured at TRIUMF to the corresponding rates at J-PARC is demonstrated taking the different beam condition into account. The projected rates agree with the ones measured at J-PARC within the uncertainty of about $\pm$14%.

中文翻译：

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激光烧蚀二氧化硅气凝胶的μ发射研究

使用TRIUMF和日本质子加速器研究中心的表面μ子束在室温下使用各种烧蚀结构研究了从二氧化硅气凝胶表面激光烧蚀的μ（$\mu^+e^-$）原子发射到真空中（ J-PARC）。除了一些极端条件外，激光烧蚀用于产生典型尺寸从几百美元到几毫米的孔或凹槽。对于较大部分的消融开口和较浅的深度，测得的发射率往往更高。超过几个消融结构达到了与过去测量中达到的最高水平相似的发射率。发现排放率至少在几天内是稳定的。对磁场中产生的 μ 原子和剩余 μ 子的自旋进动幅度的测量确定了 $(65.5 \pm 1.8)$% 的 μ 形成分数，并表明 μ 原子的极化在真空中得以保留。考虑到不同的光束条件，演示了在 TRUMF 测量的发射率到 J-PARC 的相应速率的投影。预计利率与 J-PARC 测量的利率一致，不确定性约为 $\pm$14%。