Performance of a small high-speed liquid jet apparatus

The performance of a small high-speed liquid jet apparatus is described. Water jets of 200m/s to 700m/s have been obtained by firing a deformable lead slug from an air rifle into a stainless steel nozzle containing water sealed with a rubber diaphragm. Nozzle devices of using the impact extrusion (IE) method and cumulation (CU) method are designed to generate jets. The injection sequences are visualized using schlieren photography. The difference between the IE and CU methods in the jet generation is found.

Laser-Induced Particle Jet And Its Ignition Application In Premixed Combustible Gases

A hot particle jet is induced as a laser pulse from a free oscillated Nd:YAG laser focused on a coal target. The particle jet successfully initiates combustion in a premixed combustible gas consisting of hydrogen, oxygen, and air. The experiment reveals that the ionization of the particle jet is enhanced during the laser pulse. This characteristic is attributed to the electron cascade process and the ionization of the particles or molecules of the target. The initial free electrons, which are ablated from the coal target, are accelerated by the laser pulse through the inverse Bremsstrahlung process and then collide with the neutrals in the jet, causing the latter to be ionized.

Investigation on mechanism of critical cavitating flow in liquid jet pumps under operating limits

The critical cavitating flow in liquid jet pumps under operating limits is investigated in this paper. Measurements on the axial pressure distribution along the wall of jet pumps indicate that two-phase critical flow occurs in the throat pipe under operating limits. The entrained flow rate and the distribution of the wall pressure upstream lowest pressure section does not change when the outlet pressure is lower than a critical value. A liquid-vapor mixing shockwave is also observed under operating limits. The wave front moves back and forth in low frequency around the position of the lowest pressure. With the measured axial wall pressures, the Mach number of the two-phase cavitating flow is calculated. It's found that the maximum Mach number is very close to I under operating limits. Further analysis infers a cross-section where Mach number approaches to I near the wave front. Thus, the liquid-vapor mixture velocity should reach the local sound velocity and resulting in the occurrence of operating limits.

Fluctuation characteristics of arc voltage and jet flow in a non-transferred dc plasma generated at reduced pressure

A torch with a set of inter-electrode inserts between the cathode and the anode/nozzle with a wide nozzle exit was designed to generate plasma jets at chamber pressures of 500–10 000 Pa. The variation of the arc voltage was examined with the change in working parameters such as gas flow rate and chamber pressure. The fluctuation in the arc voltage was recorded with an oscilloscope, and the plasma jet fluctuation near the torch exit was observed with a high-speed video camera and detected with a double-electrostatic probe. Results show that the 300 Hz wave originated from the tri-phase rectified power supply was always detected under all generating conditions. Helmholtz oscillations over 3000 Hz was detected superposed on the 300 Hz wave at gas flow rates higher than 8.8 slm with a peak to valley amplitude lower than 5% of the average voltage value. No appreciable voltage fluctuation caused by the irregular arc root movement is detected, and mechanisms for the arc voltage and jet flow fluctuations are discussed.

Measured temperature of a laminar plasma jet by using thermocouple at reduced pressure

Attempts were made to measure the gas temperature of a DC arc laminar plasma jet generated at reduced pressure by using a pair of WRe-5/26 thermocouple. Results show that the measured temperature is much lower than the value measured by using the spectral method. Theoretical work considering rarefied-gas heat transfer effects has been carried out to analyze the measured error of the thermocouple.

Fluctuations in a direct current argon plasma jet at reduced pressure

Dynamic measurements of the ion saturation current in the plasma plume by a double-electrostatic probe system were carried out. Regular signals obtained by the electros- tatic probe show good agreement with the stable plasma flow state. Dependence of the flow steadiness on the plasma generation parameters was discussed. As a fast response method, the double-electrostatic probe system is feasible to characterize the fluctuations in the plasma jet.

The calculation of photoelectron angular distributions with jet-like structure from scattering theory

Photoelectron angular distributions produced in above-threshold ionization (ATI) are analysed using a nonperturbative scattering theory. The numerical results are in good qualitative agreement with recent measurements. Our study shows that the origin of the jet-like structure arises from the inherent properties of the ATI process and not from the angular momentum of either the initial or the excited states of the atom.

Interactions of a femtosecond intense laser with rare gas clusters in a dense jet\

A study on the interactions of high intensity (similar to 10(16) W/cm(2)) femtosecond laser pulses with rare gas clusters in a dense jet is performed. Energy absorption by Ar and Xe clusters is measured and it can be as high as 90%. Very energetic ions produced in the laser interaction with a dense cluster jet are detected by time-of-flight spectrometry and the maximum ion energy of Xe is up to 1.3 MeV. The average ion energies are found to increase with increasing cluster size and get saturated gradually. The average ion energies also show a strong directionality and the average ion energy in the direction parallel to the laser polarization vector is 40% higher than that perpendicular to it. The findings are discussed in terms of a model of charge-dependent ion acceleration.

A plasma channel scheme for the interaction of an intense femtosecond laser pulse with a deuterium cluster jet

We propose a plasma channel scheme to obtain an improved table-top laser driven fusion neutron yield as a result of explosions of large deuterium clusters irradiated by an intense laser pulse. A cylindrical plasma channel is created by two moderate intensity laser prepulses at the edge of a deuterium cluster jet along which an intense main laser pulse propagates several nanoseconds later. With the aid of this plasma channel, the main laser pulse will be allowed to deposit its energy into the central region of the deuterium gas jet where the cluster sizes are larger and the atomic density is higher. The plasma channel formation and its impact on the deuterium ion energy spectrum and the consequent fusion neutron yield have been investigated. The calculated results show that a remarkable increase of the table-top laser driven fusion neutron yield would be expected.

A study of W boson properties with four-jet W^+W^- events at LEP

In this thesis I present a study of W pair production in e⁺e^- annihilation using fully hadronic W⁺W^- events. Data collected by the L3 detector at LEP in 1996-1998, at collision center-of-mass energies between 161 and 189 GeV, was used in my analysis.

Analysis of the total and differential W⁺W^- cross sections with the resulting sample of 1,932 W⁺W^- → qqqq event candidates allowed me to make precision measurements of a number of properties of the W boson. I combined my measurements with those using other W⁺W^- final states to obtain stringent constraints on the W boson's couplings to fermions, other gauge bosons, and scalar Higgs field by measuring the total e⁺e^- → W⁺W^- cross section and its energy dependence

σ(e⁺e^- → W⁺W^-) =

{2.68^+0.98_-0.67(stat.)± 0.14(syst.) pb, √s = 161.34 GeV

{12.04^+1.38_-1.29(stat.)± 0.23(syst.) pb, √s = 172.13 GeV

{16.45 ± 0.67(stat.) ± 0.26(syst.) pb, √s = 182.68 GeV

{16.28 ± 0.38(stat.) ± 0.26(syst.) pb, √s = 188.64 GeV

the fraction of W bosons decaying into hadrons

invisible non-SM width of the W boson

the mass of the W boson

the total width of the W boson

the anomalous triple gauge boson couplings of the W

Δg^Z₁ = 0.16^+0.13_-0.20(stat.) ± 0.11(syst.)

Δk_γ = 0.26^+0.24_-0.33(stat.) ± 0.16(syst.)

λ_γ = 0.18^+0.13_-0.20(stat.) ± 0.11(syst.)

No significant deviations from Standard Model predictions were found in any of the measurements.