Schematic view of principle of the Nijmegen Pulsed Valve: (a) no current passing through the aluminum, valve is closed. (b) Lorentz force lifts the strip up, opening the valve. The distortion of the aluminum strip due to the Lorentz force is exaggerated for clarity.
Schematic view of the actual construction of the Nijmegen Pulsed Valve. The left picture shows an overview and the right picture displays a cross section view of the valve.
Block diagram of the electronics used to drive the NPV.
Schematic view of the experimental setup using two lasers crossing the molecular beam at two points A and B. The double resonantly ionized NO+ ions are detected by VMI.
Total NO+ ion yield, as measured by the CCD camera of the light from the phosphor screen behind the MCP detector, of two different skimmed beams of 0.1% NO in helium and 0.5% NO in argon at 6 bar backing pressure. The intensities of NO (J = 1/2) are presented. The distance between nozzle and laser ionization region was 12 cm. Pulsed beams with FWHM duration as short as 20 μs can be made with the NPV. Each curve was normalized individually and the top curve (0.5% NO in argon) was shifted vertically by one unit for clarity.
REMPI spectrum acquired for NPV molecular beam using (a) 0.1% NO/He, (b) 0.5% NO/Ar, and comparison with simulation.
Results from 0.1% NO in He. (a) 3D image taken using a pump-probe scheme: pump-probe delay at the horizontal axis, and NPV-pump delay at the vertical axis. Measured ion intensities are represented in false color representation. The curve above the image (derived from integration of ion intensities along vertical axis) presents the travelling time distribution of the whole pulse packet between pump and probe position. The curve on the right side of the image (from integration of ion intensities along the horizontal axis) displays the molecular pulse profile at the pump position. (b) Overall speed distribution at the pump position: the mean speed is about 1850 m/s and the speed spread in the form of Δv FHWM = 96 m/s, the speed ratio is 32 (S = 1.66 · v/Δv FWHM ). The curves drawn through the dat points are only meant to guide the eye. (c) Molecular beam pulse profile at the pump position (left curve of bottom figure) and probe position (right curve of bottom figure). Corresponding distributions of the speed ration S are shown in the upper figure.
Speed ratio measurement for NPV produced molecular beam of 0.5% NO/Ar: (a) original 3D image for pump position and (b) derived one for probe position.
Speed ratio measurement for NPV produced molecular beam of 0.5% NO/Ar: (see also caption of Fig. 7 ) (a) Overall speed distribution, (b) molecular beam pulse profile at the pump position (left curve of bottom figure) and probe position (right curve of bottom figure). Corresponding distributions of the speed ration S are shown in the upper figure.
Results of the FIG measurements comparing the NPV with two other pulsed valves (standard operation, not specifically optimized for short pulse duration) in pure helium. The uncertainty in all values is 20% or higher.
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