D. DeSchepper

Spin-dependent scattering of polarized protons from a polarized 3He internal gas target

We describe the first experiment to use a polarized internal gas target and polarized beam in a storage ring. A laser optically pumped polarized 3He internal gas target has been used with circulating beams of 197–414 MeV polarized protons to carry out an extensive set of measurements of spin dependent scattering. A large acceptance non-magnetic detector system consisting of wire-chambers, scintillators and microstrip detectors was used to detect protons, neutrons, deuterons, and 3He nuclei from the beam-target interaction. It is demonstrated that these techniques result in low backgrounds (< 1%) due to scattering from species other than the polarized target gas and allow detection of low energy recoiling nuclei. Specific issues such as interfacing the experiment to the storage ring and monitoring the luminosity and polarizations are discussed in detail.

THE HERMES POLARIZED 3HE INTERNAL GAS TARGET

Abstract The HERMES experiment is investigating the spin structure of the proton and neutron via deep-inelastic scattering of polarized positrons from polarized nuclear targets. The polarized positrons are provided by the HERA positron storage ring at DESY, Hamburg, Germany. The targets are pure internal gas targets. Data acquisition began in 1995, utilizing a polarized 3 He internal gas target to study the spin structure of the neutron. The target gas was polarized using the metastability-exchange optical-pumping technique and then injected into a cryogenically cooled target cell. The target was designed to operate with either longitudinal or transverse directions of polarization. Operating conditions included polarizations of up to 54% and target thicknesses of 1×10 15 nucleons/cm 2 . In this paper the HERMES polarized 3 He internal gas target is described in detail.

Temperature dependence of 3He polarization in aluminum storage cells

Abstract The temperature dependence of the polarization of 3 He atoms in an internal target cell has been studied. Metastable optically pumped polarized 3 He atoms with typical polarization values of 40% were injected into a thin-walled aluminum cell of 40 cm length and a 29.0 × 9.8 mm 2 elliptical cross-section. The cell temperature was varied between 5 and 85 K. The polarization inside the target cell was measured via an asymmetry in the 3 He → (d,p) 4 He reaction at a deuteron energy of 4 MeV. An exponential decrease of the polarization was found for temperatures less than 15 K. For a temperature of ∼6 K a polarization consistent with zero was measured.

An internal polarized 3He target for electron storage rings

We describe an internal polarized 3He target under construction which will be used in several electron storage ring experiments. The target is based on the technique of metastability exchange laser optical pumping, where the polarized atoms flow into a cryogenically‐cooled storage cell. This novel technique allows for high precision measurements where the beam interacts with the pure atomic species. Both the HERMES experiment at DESY and the BLAST detector at the MIT Bates Laboratory will use the polarized 3He target in their measurements. Details of the target system, including the provisions needed to incorporate the target into the electron storage ring, are presented.

Measurement of spin observables in quasielastic scattering of polarized protons from polarized 3He

Measurements of analyzing powers and spin correlation parameters for 3He(p↘,2p) and 3H↘e(p↘,pn) quasielastic scattering have been carried out using a polarized internal 3He target and a stored, polarized proton beam. They were made over a wide kinematic range with a proton energy of 197 MeV and a large acceptance detector system which allowed the simultaneous measurement of both reactions. At momentum transfers sufficiently high to minimize rescattering effects, the (p,pn) results are in agreement with PWIA calculations. The (p,2p) results were found to be less sensitive to kinematic conditions and are also in agreement with calculations.