We demonstrate efficient transverse compression of a $12.5\mathrm{MeV}/\mathrm{c}$ muon beam stopped in a helium gas target featuring a vertical density gradient and crossed electric and magnetic fields. The muon stop distribution extending vertically over 14 mm was reduced to a 0.25 mm size (rms) within $3.5\mu \mathrm{s}$. The simulation including cross sections for low-energy ${\mu }^{+}$-He elastic and charge exchange (${\mu }^{+}\leftrightarrow$ muonium) collisions describes the measurements well. By combining the transverse compression stage with a previously demonstrated longitudinal compression stage, we can improve the phase space density of a ${\mu }^{+}$ beam by a factor of ${10}^{10}$ with ${10}^{-3}$ efficiency.

中文翻译：

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Muon-Beam横向相空间压缩演示

我们展示了有效的横向压缩 $12.5\mathrm{病毒}/\mathrm{C}$on子光束停在具有垂直密度梯度和交叉电场和磁场的氦气目标中。垂直延伸超过14毫米的μ子光阑分布减小到0.25毫米大小（rms）$3.5\mu \mathrm{s}$。模拟包括低能耗的横截面${\mu }^{+}$-他弹性和电荷交换（${\mu }^{+}\leftrightarrow$碰撞）很好地描述了测量结果。通过将横向压缩阶段与先前演示的纵向压缩阶段相结合，我们可以提高相变密度。${\mu }^{+}$ 光束因数 ${10}^{10}$ 与 ${10}^{-3}$ 效率。