A Simple Nozzle Configuration for the Production of Low Divergence Supersonic Cluster Beam by Aerodynamic Focusing

Abstract

A nozzle con guration for the production of an intense and collimated supersonic cluster beam is presented and characterized by numerical modeling. A simple lens added to a cylindrical nozzle exploits aerodynamic focusing effects. The effect of the focalizing nozzle is an enrichment of the core of the jet with clusters of an arbitrary size interval depending on carrier gas pressure and temperature. The in uence of the source and nozzle geometrical parameters and of the expansion conditions on the cluster focalization is simulated and compared to the experimental results. A collimating effect on particle velocities and the possibility of obtaining a cluster mass selection is also observed.

Pulsed Supersonic Beams from High Pressure Source: Simulation Results and Experimental Measurements

“…Both cone nozzle and parabolic nozzle show a slower expansion rate resulting in higher beam number density (i.e., beam intensity) at a given distance from the nozzle. This slower expansion results in a many more collisions before the beam density becomes too low (the so called sudden freeze model [5,[31][32][33][34][35][36]), enabling more efficient cooling due to two-body collisions, as well as encouraging cluster growth via threebody collisions. One can conclude from these simulations that a conical or parabolic nozzle is much better than a sonic nozzle for obtaining high on-axis beam intensities.…”

Design, Modeling, Optimization, and Experimental Tests of a Particle Beam Width Probe for the Aerodyne Aerosol Mass Spectrometer

“…Aerodynamic lenses were first demonstrated by the group of P.H. McMurry at the University of Minnesota (Liu et al 1995a(Liu et al , 1995b and have been the subject of a number of characterization and customization studies by several groups (Petrucci et al 2000;Schreiner et al 1999;Schreiner et al 1998;Tafreshi et al 2002;Zhang et al 2002;Zhang et al 2004c). A multistage lens consists of a cylindrical tube through which a series of axisymmetric cylindrical constrictions act to compress the gas (and particle) trajectories, while a final nozzle is used for the expansion of the gas and particle beam into the vacuum chamber.…”

“The Even-Lavie valve as a source for high intensity supersonic beam”

“…The adiabatic expansion of the gas can be analytically solved and easily computed either by CFD [25,26] calculation (solving the Navier-Stokes equation) or simulated using a variety of MonteCarlo programs. It was soon realized that shaping the nozzle can shape the expanding gas jet [3,[26][27][28][29] and change the number of collisions before the beam density drops to low value and the expansion and cooling practically "Freezes" [8,9,30]. Most nozzles have small length dimensions (several mm in size due to pumping limitations) and making a complicated and smooth shape is difficult [31].…”