W. A. Kaufman

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.

Solenoid and sextupole optics of ultra-cold atomic hydrogen beams

Abstract Analytic calculations and particle tracking simulations are presented for a polarized atomic hydrogen beam produced by extraction from a superfluid helium coated cell in a large solenoidal magnetic field. Compression of the beam by the solenoidal field and subsequent focusing by a sextupole are considered.

A helium film coated quasi‐parabolic mirror to focus a beam of ultra‐cold spin polarized atomic hydrogen

A 350 mK helium‐4‐coated mirror was used to increase the intensity of an ultra‐cold electron‐spin‐polarized atomic hydrogen beam. The mirror uses the observed specular reflection of atomic hydrogen from a superfluid‐helium‐covered surface. A quasi‐parabolic polished copper mirror was installed with its focus at the 5 mm diameter exit aperture of an atomic hydrogen stabilization cell in the gradient of an 8 T solenoid field. The four‐coned mirror shape, which was designed specifically for operation in the gradient, increased the beam intensity focused by a sextupole magnet into a compression tube detector by a factor of about 7.5.

Status on the Michigan‐MIT ultra‐cold polarized hydrogen jet target

Progress on the Mark‐II ultra‐cold polarized atomic hydrogen gas Jet target for the experiments NEPTUN‐A and NEPTUN at UNK is presented. We describe the performance and the present status of different components of the jet.

First test of a partial Siberian snake for acceleration of polarized protons

We recently studied the first acceleration of a spin‐polarized proton beam through a depolarizing resonance using a partial Siberian snake. We accelerated polarized protons from 95 to 140 MeV with a constant 10% partial Siberian snake obtained using rampable solenoids. The 10% partial snake suppressed all observable depolarization during acceleration due to the Gγ=2 imperfection depolarizing resonance which occurred near 108 MeV. However, 20% and 30% partial Siberian snakes apparently moved an intrinsic depolarizing resonance, normally near 177 MeV, into our energy range; this caused some interesting, although not‐yet‐fully understood, depolarization.

Spin flipping a stored vertically polarized proton beam with an RF solenoid

A recent experiment in the IUCF cooler ring studied the spin flip of a stored vertically polarized 139 MeV proton beam. This spin flip was accomplished by using an RF solenoid to induce an artificial depolarizing resonance in the ring, and then varying the solenoid’s frequency through this resonance value to induce spin flip. We found a polarization loss after multiple spin flips of about 0.00±0.05% per flip and also losses for very long flip times. This device will be useful for reducing systematic errors in polarized beam‐internal target scattering asymmetry experiments by enabling experimenters to perform frequent beam polarization reversals in the course of the experiment.