Facile time-of-flight methods for characterizing pulsed superfluid helium droplet beams

Journal Article · Sat Aug 15 04:00:00 EDT 2015 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.4928107· OSTI ID:22482750

He, Yunteng; Zhang, Jie; Li, Yang; Freund, William M.; Kong, Wei ^[1]

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1. Department of Chemistry, Oregon State University, Corvallis, Oregon 97331 (United States)

We present two facile time-of-flight (TOF) methods of detecting superfluid helium droplets and droplets with neutral dopants. Without an electron gun and with only a heated filament and pulsed electrodes, the electron impact ionization TOF mass spectrometer can resolve ionized helium clusters such as He{sub 2}{sup +} and He{sub 4}{sup +}, which are signatures of superfluid helium droplets. Without ionizing any helium atoms, multiphoton non-resonant laser ionization of CCl{sub 4} doped in superfluid helium droplets at 266 nm generates complex cluster ions of dopant fragments with helium atoms, including (He){sub n}C{sup +}, (He){sub n}Cl{sup +}, and (He){sub n}CCl{sup +}. Using both methods, we have characterized our cryogenic pulsed valve—the Even-Lavie valve. We have observed a primary pulse with larger helium droplets traveling at a slower speed and a rebound pulse with smaller droplets at a faster speed. In addition, the pickup efficiency of dopant is higher for the primary pulse when the nozzle temperature is higher than 13 K, and the total time duration of the doped droplet pulse is only on the order of 20 μs. These results stress the importance of fast and easy characterization of the droplet beam for sensitive measurements such as electron diffraction of doped droplets.

• OSTI ID: 22482750
• Journal Information: Review of Scientific Instruments, Journal Name: Review of Scientific Instruments Journal Issue: 8 Vol. 86; ISSN 0034-6748; ISSN RSINAK
• Country of Publication: United States
• Language: English

Related Subjects

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
BEAMS
CARBON TETRACHLORIDE
DOPED MATERIALS
DROPLETS
EFFICIENCY
ELECTRODES
ELECTRON DIFFRACTION
ELECTRON GUNS
FILAMENTS
HELIUM
ION PAIRS
LASERS
MASS SPECTROMETERS
MULTI-PHOTON PROCESSES
NOZZLES
PULSES
SUPERFLUIDITY
TIME-OF-FLIGHT METHOD
VALVES