Schematic of a molecular beam source employing a non-diaphragm type small shock tube.
A high-speed response valve exploiting the current-loop mechanism. (a) Cross-sectional diagrams (close and open states). 1: High-voltage power supply, 2: thyristor switch, 3: protection diode, and 4: capacitor. (b) Expanded diagram, with minor parts omitted for clarity. 1: Positioning block, 2: spring, 3: piston, 4: actuation plate, 5: contact plate, 6: insulation sheet, 7: face plate, 8: elastomer tube, and 9: high-pressure chamber.
Temporal changes in piston displacement. The shape of the actuation plate (thickness: 0.15 mm) is shown in the inset. The voltage applied to the capacitor is 1800 V and the pulse current (calculated from the change in the capacitor voltage) is about 5000 A.
Response time of the current-loop valve as a function of pulse current. The geometry of the actuation plates is shown in the inset. Plate A: thickness = 0.15 mm, D = 11.7 mm; plate B: thickness = 0.1 mm, D = 9.7 mm.
Schematic of the experimental setup for measurements of shock Mach numbers. The diameter of the convergent shock tube linearly decreases from 4 to 2 mm within the 100 mm length. The temperature sensor is inserted from the tube end and placed at arbitrary positions to measure shock arrival times.
The x-t diagram of the shock front at p 41 = 1000 in the 4-mm-diameter straight shock tube. The error bars are within the symbols. The trace of the contact surface should be on the left of the dashed line. For more details, see text.
Shock Mach number M s at x = 300 mm as a function of the initial pressure ratio p 41 in the convergent shock tube (L = 200 mm).
Shock Mach number M s as a function of the distance x from the current-loop valve at p 41 = 1000. The lengths of the straight sections preceding the converging section are L = 50, 200, 300, and 385 mm. The diameters of the straight tubes are 2 and 4 mm.
Schematic of the experimental setup for the repetitive operation test. The tube comprises a 4-mm-diameter straight section and a subsequent converging section whose diameter linearly decreases from 4 to 2 mm. The temperature sensor is placed at the tube end (x = 300 mm).
Shock Mach number M s at the tube end (x = 300 mm) as a function of supply time of the driven gas t sup. The shock Mach number was estimated from the relationship between the shock arrival time and the Mach number obtained in the single-shot measurements. The error bars were determined from fluctuations of shock arrival time and the uncertainty of the abovementioned relationship. The vertical axis on the right side shows the translational energy of the molecular beam estimated from Eqs. (1) and (2) .
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