We demonstrate a cryogenic buffer gas-cooled molecular beam source capable of producing bright, continuous beams of cold and slow free radicals via laser ablation over durations of up to 60 seconds. The source design uses a closed liquid helium reservoir as a large thermal mass to minimize heating and ensure reproducible beam properties during operation. Under typical conditions, the source produces beams of our test species SrF, containing $5\times {10}^{12}$~molecules per steradian per second in the X${}^2\Sigma (v=0,N=1)$ state with a rotational temperature of 1.0(2)~K and a forward velocity of $140$m/s. The beam properties are robust and unchanged for multiple cell exit geometries but depend critically on the helium buffer gas flow rate, which must be $\ge 10$~standard cubic centimeters per minute to produce bright, continuous beams of molecules for an ablation repetition rate of 55 Hz.

中文翻译：

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明亮，连续的冷自由基束

我们展示了一种低温缓冲气体冷却分子束源，能够通过长达60秒的激光烧蚀产生明亮，连续的冷，慢速自由基束。源设计使用封闭的液态氦气储存器作为较大的热量，以最大程度地减少热量并确保在操作过程中可重现的射束特性。在典型条件下，光源会产生我们测试物种SrF的光束，其中包含$5\times {10}^{12}$〜X中每Steradian每秒的分子${}^2\Sigma （v=0，ñ=\mathrm{1个}）$ 旋转温度为1.0（2）〜K且前进速度为 $140$多发性硬化症。对于多种电池出口几何形状，束流特性是坚固且不变的，但关键取决于氦缓冲气体的流速，该流速必须为$\ge 10$每分钟约标准立方厘米，以产生55 Hz的消融重复率的明亮，连续的分子束。