Study of Supersonic Deuterium Beams Gianangelo (Nino) Bracco Department of Physics & INFN University of Genoa, Italy FUTUREJET Meeting November 3rd/4th 2011 at GSI Dept. of Physics and Technology & Michelsen Center University of Bergen, Norway

source Supersonic beam Skimmer Parallel velocity distribution Central streamline Perpendicular velocity distribution The back projection of v perpendicular determines the width w s of the virtual source (Beijerinck, 1981). Region of molecular collision: continuum flow Collisionless region: molecular flow Beam velocity V, velocity spread  V (speed ratio S=(2  log 2)V/  V

Magie the Dep.Physics & Techology, Bergen University ~3 m source detector Zone plate

Experimental setup 378mm 1500 mm slit aperture 11- μm x 5-mm scan steps: 500 nm  m TOF measurements without ZP and slit Virtual source size measurements with ZP and slit Focal plane of the ZP

Outer zones 96 nm period 390-μm-diameter SiN ZP SEM image of the zone plate for neutral beams 540-μm-diameter Ni ZP 100 nm period About 2700 free-standing zones. collab. Henry I. Smith NanoStructures Laboratory, MIT Massachusetts USA Stefan Rehbein, BESSY m.b.H., Berlin,Germany Günter Schmahl Univ. of Göttingen, Institute for X-ray Physics, Germany

TOF Meas. Virtual source Meas. VV V Meas. Temp. 310 K 106 K

Model: solution of the Boltzmann eq.with the method of moments Assumed solution (monoatomic gas): Vibrational levels not excited rotation excited but with a small number of levels  rot =39K (monoatomic behavior) Rotation distribution described by a rotational temperature T R and the relaxation (Klots, 1982) described by Spherical symmetric expansion Eq.iteratively solved to get n,u(=V), T||, T ┴, T R

contains Collision integral Viscosity cross section Phase shifts Lennard-Jones potential Buck et al. potential Relaxation rate  =1/Z rot

Results starting with the enthalpy of an ideal gas h=7/2 kT High T Low T Red LJ, green BK Terminal speed V Speed ratio condensation

Result starting with the real gas enthalpy

Evaluation of condensed fraction Enthalpy released during condensation

Cluster content in the beam

Nanophysics Group Dept. of Physics and Technology, Bergen University, Norway Thomas Reisenger Martin Greve Sabrina Eder Prof. Bodil Holst