Ultra-cold atomic hydrogen beam

Abstract

We investigated two methods of producing a continuous free beam of electron-spin polarized atomic hydrogen, using a 7.5 T solenoid magnetic field and a helium film-coated cell. The first method involves accumulating H [downwards arrow] at high field in a 300 mK storage cell and flipping the electron spin by using microwaves to drive a hyperfine transition. The resulting H[short up arrow] atoms are accelerated and focused by the solenoid gradient to form an extracted beam. The second method uses the helium film-coated cell as an ultra-cold nozzle. Unpolarized hydrogen is thermalized in high field by collisions with the cell walls; the field gradient subsequently separates the atoms of different spin states to produce an H[short up arrow] beam.