B. Vuaridel

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.

New constraints on D-state contributions to the trinucleon wave functions

Abstract Cross-section and polarization data of the 4 He(d, 3 He) 3 H reaction measured at 5 energies have been analysed. The vertex constants for the neutron transfer G n , the proton transfer G p and the asymptotic normalization constant C s 2 , for the S-state of the 3 H wave function have been determined. New constraints on the D- to S-state asymptotic normalization ratio η t , and η 3 He for the triton and 3 He wave functions are obtained from the tensor analyzing powers. The method of the analytic extrapolation in the angular variable to the transfer poles was used. Implications of this method and its application are discussed. Criteria for the reliability of the results are presented. The result of the analysis is C s 2 = 2.95 ±0.15, η t = 0.050 ± 0.006 and η 3 He = 0.035 ± 0.006. The ratio η t / η 3 He shows a significant deviation from unity suggesting a substantial isospin breaking effect.

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.

Energy change of a depolarizing resonance due to a type-3 Siberian snake

The authors measured the photon beam polarization in the IUCF (Indiana University Cyclotron Facility) Cooler Ring at five energies. They found that the G/sub lambda /=2 imperfection depolarizing resonance occurred about 1.9 MeV below the expected resonance energy of 108.4 MeV. This energy shift could be due to a shift of about +0.0036 in the spin time, nu /sub s/, which is the number of spin rotations in each turn around the ring. It was then demonstrated that this spin tune shift is consistent with the cooler ring containing a partial type-3 Siberian snake, which is apparently caused by the magnets that confine the electron and proton beams in the cooling region.<<ETX>>

Investigation of Polarization Transfer in p-d Scattering at E p = 22.7 MeV

The polarization transfer in p-d elastic scattering was shown to be sensitive to the details of the tensor force in the N-N interaction. Therefore measurements of the polarization transfer coefficients in this scattering have been carried out at an incident proton energy of 22.7 MeV. The data are compared to rigorous Faddeev calculations using different N-N potentials. The observable most sensitive to details of the potentials is the nucleon-nucleon polarization transfer coefficient K y y′ (Wolfenstein’s depolarization parameter D). The agreement of the K y y′ data with the calculations using the Bonn A potential is much better than with the Paris or Bonn B potentials. Results of recent measurements of K z x′ are presented and compared to the calculations. Measurements of the polarization transfer to the recoil deuterons are in progress.