Slow muon experiment by laser resonant ionization method at RIKEN-RAL muon facility
Slow muon experiment by laser resonant ionization method at RIKEN-RAL muon facility
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RIKEN-RAL muon 设施的激光共振电离法慢 muon 实验
DOI：
10.1016/s0584-8547(03)00062-4
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发表时间：
2003
期刊：
影响因子：
--
通讯作者：
K. Nagamine
中科院分区：
文献类型：
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作者：
P. Bakule;Y. Matsuda;Y. Miyake;P. Strasser;K. Shimomura;S. Makimura;K. Nagamine
我们首次报道了用共振激光电离μ素的方法从脉冲表面μ子束中产生慢μ子的结果。在加热到2100 K的薄钨箔表面附近，通过电子捕获从μ子束产生μ素。利用真空紫外（VUV）辐射与μ素2 P态（λ 1 S-2 P = 122.09nm）共振，共振增强了电离。使用355 nm的脉冲束从2 P态进行有效电离。在相位匹配的氪气和氩气缓冲气体中，利用谐振三阶和差频率变换（ωVUV=2ωR−ωT）产生脉宽为4 ns、带宽超过100 GHz的真空紫外光束，以匹配μ介子的多普勒展宽（200 GHz）。将ω R束调谐到氪4p 55 p [1/2，0]态的双光子共振，以增强转换过程。研究了不同入射光束能量和共焦参数下的真空紫外辐射产额。整个装置，包括用于传输和检测电离粒子的光束线，已经通过在1.1×10− 9 hPa的超高真空水平下电离剩余氢原子进行了测试，效率优于10−3。在第一束时间内获得的慢μ子产额为0.03 μ+/s。
We report first results of the slow muon generation from pulsed surface muon beam using a method of resonant laser ionization of muonium. The muonium is produced from the muon beam by electron capture near the surface of thin tungsten foil heated to 2100 K. The ionization is resonantly enhanced by using a vacuum-ultraviolet (VUV) radiation resonant with 2P state of muonium (λ1S–2P=122.09 nm). A pulsed beam at 355 nm is used for an efficient ionization from the 2P state. The VUV beam with pulse duration of 4 ns and with bandwidth of over 100 GHz to match the Doppler broadening of muonium (200 GHz) is generated by resonant third-order sum-difference frequency conversion (ωVUV=2ωR−ωT) in krypton gas phase-matched with argon buffer gas. The ωRbeam has been tuned to the two-photon resonance of 4p55p[1/2,0] state in krypton to enhance the conversion process. Yield of the VUV radiation has been investigated for different energies and confocal parameters of the incident beams. The whole apparatus, including a beamline for transport and detection of ionized particles, has been tested by ionizing residual hydrogen atoms at an ultra-high vacuum level of 1.1×10−9hPa with efficiency better than 10−3. The yield of slow muons obtained during the first beamtime was 0.03 μ+/s.