T. Roser

Microwave driven extraction of stabilized spin polarized atomic hydrogen

Abstract The storage of ultracold spin-polarized hydrogen atoms offers the possibility of producing a high intensity nuclear polarized atomic hydrogen jet. We stored electron spin polarized atomic hydrogen at 0.4 K in an open 5 T magnetic storage cell. We also observed directly, for the first time, the extraction of hydrogen atoms from the storage cell by flipping their spins using a microwave driven transition. The results are being used to design a high intensity jet of nuclear polarized atomic hydrogen to be used as an internal target in the 400 GeV to 3 TeV UNK accelerator.

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 ↓ 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↑ 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↑ beam.

CONTINUOUS DENSITY MEASUREMENT OF ATOMIC HYDROGEN BY MEANS OF A BOLOMETER

We developed a device which allows continuous measurement of the density of low‐temperature stabilized atomic hydrogen by means of a bolometer. This density monitor was tested in a large open‐storage cell during microwave‐induced extraction of polarized atoms.

Cryopumping of atomic hydrogen

The pumping speed for the cryopumping of an atomic hydrogen beam was measured. Measurements were made for cryocondensation, cryosorption, and differential pumping. The pumping speed for atomic hydrogen was observed to be much smaller than the pumping speed for molecular hydrogen. It is believed that this is due to the energy released during the recombination of the atomic hydrogen.

The ultra-cold polarized hydrogen jet project

Research is described on a jet of polarized atomic hydrogen. Atoms in the two lower hyperfine states are trapped at 0.4 k in a 5 T magnetic field. Microwaves at 140 GHz then drive transitions to the upper hyperfine states and these atoms are expelled from the field to form the beam. Atoms have been trapped, transitions driven, and atoms detected outside the trapping field, but preliminary measurements are not fully understood. Studies are continuing.

Spontaneous nuclear polarization of atomic hydrogen at low magnetic field

The known spin‐exchange rates of atomic hydrogen lead to fast spontaneous buildup of high nuclear polarization at low magnetic field. We propose to use the nuclear polarized atomic hydrogen gas to produce an intense ultracold nuclear polarized beam of atomic hydrogen.

An ultra‐cold jet of polarized atomic hydrogen

Equipment is being tested to determine the applicability of cryogenic atomic physics techniques to the production of dense polarized atomic hydrogen beams. Such beams, with expected densities of 1014/cm3, would be useful for internal targets.