Irimia Daniel, Dobrikov Dimitar, Kortekaas Rob, Voet Han, van den Ende Daan A, Groen Wilhelm A, Janssen Maurice H M
Department of Chemistry and Laser Centre, Vrije Universiteit, de Boelelaan 1083, Amsterdam 1081 HV, The Netherlands.
Rev Sci Instrum. 2009 Nov;80(11):113303. doi: 10.1063/1.3263912.
In this paper we report on the design and operation of a novel piezovalve for the production of short pulsed atomic or molecular beams. The high speed valve operates on the principle of a cantilever piezo. The only moving part, besides the cantilever piezo itself, is a very small O-ring that forms the vacuum seal. The valve can operate continuous (dc) and in pulsed mode with the same drive electronics. Pulsed operation has been tested at repetition frequencies up to 5 kHz. The static deflection of the cantilever, as mounted in the valve body, was measured as a function of driving field strength with a confocal microscope. The deflection and high speed dynamical response of the cantilever can be easily changed and optimized for a particular nozzle diameter or repetition rate by a simple adjustment of the free cantilever length. Pulsed molecular beams with a full width at half maximum pulse width as low as 7 micros have been measured at a position 10 cm downstream of the nozzle exit. This represents a gas pulse with a length of only 10 mm making it well matched to for instance experiments using laser beams. Such a short pulse with 6 bar backing pressure behind a 150 microm nozzle releases about 10(16) particles/pulse and the beam brightness was estimated to be 4x10(22) particles/(s str). The short pulses of the cantilever piezovalve result in a much reduced gas load in the vacuum system. We demonstrate operation of the pulsed valve with skimmer in a single vacuum chamber pumped by a 520 l/s turbomolecular pump maintaining a pressure of 5x10(-6) Torr, which is an excellent vacuum to have the strong and cold skimmed molecular beam interact with laser beams only 10 cm downstream of the nozzle to do velocity map slice imaging with a microchannel-plate imaging detector in a single chamber. The piezovalve produces cold and narrow (Delta v/v=2%-3%) velocity distributions of molecules seeded in helium or neon at modest backing pressures of only 6 bar. The low gas load of the cantilever valve makes it possible to design very compact single chamber molecular beam machines with high quality cold and intense supersonic beams. The high speed cantilever piezovalve may find broad applicability in experiments where short and strong gas pulses are needed with only modest pumping, the effective use of (expensive) samples, or the production of cold atomic and molecular beams.
在本文中，我们报告了一种用于产生短脉冲原子或分子束的新型压电阀的设计与运行情况。该高速阀基于悬臂式压电原理工作。除了悬臂式压电元件本身外，唯一的运动部件是一个用于形成真空密封的非常小的O形环。该阀可使用相同的驱动电子设备以连续（直流）和脉冲模式运行。已在高达5 kHz的重复频率下测试了脉冲运行情况。使用共聚焦显微镜测量了安装在阀体中的悬臂的静态挠度与驱动场强的函数关系。通过简单调整自由悬臂长度，可轻松改变并优化悬臂的挠度和高速动态响应，以适应特定的喷嘴直径或重复频率。在喷嘴出口下游10 cm处测量到半高宽低至7微秒的脉冲分子束。这代表着长度仅为10 mm的气体脉冲，使其非常适合例如使用激光束的实验。在150微米喷嘴后6 bar的背压下，这样一个短脉冲释放约10¹⁶个粒子/脉冲，并且束流亮度估计为4×10²²个粒子/(秒·立体角)。悬臂式压电阀的短脉冲使得真空系统中的气体负载大大降低。我们展示了在由520升/秒涡轮分子泵抽气的单个真空腔中，带有分离器的脉冲阀的运行情况，该真空腔维持5×10⁻⁶托的压力，这是一个极好的真空度，可使强而冷的分离分子束在喷嘴下游仅10 cm处与激光束相互作用，以便在单个腔室中使用微通道板成像探测器进行速度映射切片成像。该压电阀在仅6 bar的适度背压下，能产生在氦气或氖气中种子化分子的冷且窄（Δv/v = 2% - 3%）的速度分布。悬臂阀的低气体负载使得设计具有高质量冷且强的超音速束的非常紧凑的单腔分子束装置成为可能。高速悬臂式压电阀可能在需要短而强的气体脉冲且只需适度抽气、有效利用（昂贵）样品或产生冷原子和分子束的实验中找到广泛应用。
