W.K. Pitts

Test of a windowless storage cell target in a proton storage ring

Abstract Stored ion beams offer the possibility to use polarized internal targets that consist of a source of polarized atoms in conjunction with a long, narrow, windowless target cell to enhance the target thickness. In this paper, we discuss the effect of such a cell on the performance of the storage ring, based on measurements carried out with the Indiana Cooler. A prototype target cell was constructed and was operated with a controlled flow of H 2 target gas in a beam of stored protons. Detection of protons scattered at angles from 4° to 15° in coincidence with the associated recoil particles was used to identify elastic scattering. The results show that the presence of a 25 cm long target cell with a rectangular opening of 6.4 mm by 7.9 mm is compatible with operation of the Cooler ring. This demonstrates the feasibility of an important component of experiments with stored, polarized beams and carrier-free polarized, internal targets.

Low energy charged particle detection in a light-ion storage ring

Abstract We have detected low energy protons from elastic proton-proton scattering at forward angles ( θ lab = 2.3° −10.6°) with silicon strip detectors mounted inside the Indiana University Cyclotron Facility “Cooler” storage ring. Detection of both protons reduces the coincident background to less than ≈ 1% of the elastic scattering rate.

Measurement of Coulomb-Nuclear Interference in the pp Analyzing Power Ay at the IUCF Cooler Ring

We report here a measurement of the analyzing power Ay in 185 MeV elastic proton-proton (pp) scattering at forward angles (2.5°–10.5° in the laboratory). In this angular range the Coulomb and nuclear amplitudes are of similar magnitude and measurements of polarization observables allow separation of the real and imaginary components of the nuclear amplitudes by their interference with the known Coulomb amplitude.[1] Precise measurements at such small angles can be difficult due to the presence of beam halo or scattering from target materials other than hydrogen. In the present experiment we have used both a windowless gas jet target and coincident detection of the low energy proton at large angles to eliminate these backgrounds.