Precise thermodynamic control of high pressure jet expansions.
We describe an experimental setup for supersonic jet expansions of supercritical fluids. It is characterized by well-defined thermodynamic values to allow systematic investigations of pressure and temperature effects on molecular beam parameters. The design permits stagnation temperatures T(0)=225-425 K with a thermal stability DeltaT(0)<30 mK and stagnation pressures p(0)=0.2-12 MPa that are measured with 0.05% precision. For optimum stability, gas reservoir, pressure transducer, and gauge amplifier are temperature-controlled, and a feedback loop permits active pressure stabilization using a pulseless syringe pump. With this approach stagnation pressures can be reproduced and kept constant to Deltap(0)<2.9 kPa. As a result, flow velocity and kinetic energy of molecular beams can be controlled with maximum accuracy.
Institut für Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Strasse 2, 12489 Berlin, Germany. christen@wolfgang-christen.net
Wolfgang
W
Christen
Tim
T
Krause
Klaus
K
Rademann
D004867:Equipment Design; D019544:Equipment Failure Analysis; D017022:Flow Injection Analysis / Q000295:instrumentation* / Q000379:methods; D006361:Heating / Q000295:instrumentation* / Q000379:methods; D008365:Manometry / Q000295:instrumentation* / Q000379:methods; D044085:Microfluidics / Q000295:instrumentation* / Q000379:methods; D011312:Pressure; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013816:Thermodynamics; D013817:Thermography / Q000295:instrumentation* / Q000379:methods