Ph. Chesny

A Frozen Spin Target with Three Orthogonal Polarization Directions

A frozen spin target has been designed and constructed at CEN-Saclay for nucleon-nucleon scattering experiments at the synchrotron SATURNE II. In this target, the polarization can be maintained in three directions: vertical, horizontal along the beam, or horizontal perpendicular to the beam. The angle of free access is up to 80° from the forward direction to the left and up to 56° or 43° to the right depending on the magnet configuration; the azimuthal angle is 15°. The magnet system is entirely superconducting. The target of about 70 cm3 maximum volume is cooled in a vertical dilution refrigerator. A 14 cm3 target has been used in several experiments with proton and deuteron beams during the 1981–1985 period.

Measurement of the total cross section difference ΔσT(pp) in the energy range from 0.43 to 2.4 GeV

Abstract The SATURNE II polarized proton beam and the Saclay frozen spin polarized proton target were used to measure the total cross section difference Δσ T = −2 σ 1 tot at 26 energies between 0.43 and 2.4 GeV. Here Δσ T is the total cross section difference for transverse beam and target spins parallel and antiparallel, respectively, and σ 1tot is one of spin-dependent terms in the total cross section σ tot . The energy dependence of Δσ T below 1 GeV shows similar structures as for Δσ L . An additional minimum appears at about 1.3 GeV, which involves a structure in singlet spin partial waves.

Energy dependence of the neutron-proton total cross section differences ΔσT and ΔσL between 0.31 and 1.1 GeV

Abstract Final results for total cross section differences ΔσT and ΔσL measured with a polarized neutron beam transmitted through a polarized proton target are presented. Measurements were carried out at SATURNE II, at 11 energies between 0.63 and 1.1 GeV for ΔσT and at 9 energies between 0.312 and 1.1 GeV for ΔσL. The results are compared with measurements at PSI and LAMPF as well as with ΔσL data points deduced from p-d and p-p transmission experiments at the ANL-ZGS. The present results together with the corresponding pp data allow to determine two of the three imaginary parts of forward scattering amplitudes for isospin I = 0.

Apparatus for the measurement of spin dependent observables in np and pp elastic and quasi-elastic scattering

Abstract The present article describes an apparatus used for the measurement of spin dependent observables at SATURNE II. Observables for np elastic and quasi-elastic scattering were measured between 0.31 and 1.1 GeV, those for pp elastic scattering between 1.94 and 2.24 GeV. Measurements of pn and pp observables with an unpolarized 6LiD and 7LiH targets around 2 GeV were also carried out. Fast electronics, on-line data acquisition, event selection and off-line analysis are presented.

Angular dependence of analyzing power in np elastic scattering between 0.312 and 1.10 GeV

Abstract We present a total of 427 np analyzing power data points in a large angular interval at 12 energies between 0.312 and 1.10 GeV. The SATURNE II polarized beam of free monochromatic neutrons was scattered either on the Saclay frozen-spin polarized proton target or on CH2 and C targets. Present results are compared with existing elastic and quasieleastic data.

Angular dependence of the beam and target analyzing powers Aoono and Aooon in np elastic scattering between 0.477 and 0.940 GeV

Abstract We present a total of 273 independent data points of the analyzing powers A oono (nP) and A ooon (nP) in a large angular interval at four energies between 0.477 and 0.940 GeV. The SATURNE II polarized beam of free neutrons obtained from the break-up of polarized deuterons was scattered on the polarized Saclay frozen-spin proton target. Part of the data was obtained with a CH 2 target. A comparison of the two measured observables allows one to determine the polarization of the neutron beam. The present results provide an important contribution to any future theoretical or phenomenological analysis.

Measurement of the spin correlation parameter Aoonn and of the analyzing power for pp elastic scattering in the energy range from 0.5 to 0.8 GeV

Abstract The spin correlation parameter A oonn and the analyzing powers A oono and A ooon were measured simultaneously, in the energy range 0.5–0.8 GeV and in the angular region 40°–80° CM. The experiment used the polarized proton beam of SATURNE II and the Saclay frozen spin polarized target.

A THREE-CELL LIQUID HYDROGEN TARGET FOR AN EXTENDED FOCAL PLANE POLARIMETER

Abstract This article describes the design and working principle of a three-cell liquid hydrogen target produced for the high-energy deuteron polarimeter HYPOM. This target uses liquid helium as a cooling agent. After a general description of the apparatus, tests and operating modes are thoroughly explained. In particular the air controlled self-regulation of helium flow in the cryostat to stabilize the liquid hydrogen level is presented. The main feature of this target is the simplicity of the design as well as its safeness towards any incident. Results of cooling down, filling up of the target and stabilization regime were processed during one experiment of physics at synchrotron Saturne II.

Angular dependence of the spin correlation parameter Aoonn in np elastic scattering between 0.8 and 1.1 GeV

Abstract We present a total of 323 data points of the spin correlation parameter A oonn (np) in a large angular interval at eight energies between 0.8 and 1.1 GeV. The SATURNE II polarized beam of free neutrons obtained from the break-up of polarized deuterons was scattered on the polarized Saclay frozen-spin proton target. The present data are the first existing results above 0.8 GeV.

Measurements of the total cross section differenceΔσ Т innp transmission between 0.86 and 0.94 GeV

We present results of the total cross section differenceΔσТ obtained in transmission measurements at the energies 0.86, 0.88, 0.91 and 0.94 GeV. The SATURNE II polarized beam of free neutrons obtained from the break-up of polarized deuterons was transmitted through the polarized Saclay frozen-spin proton target. The beam and target polarizations were oriented in the vertical direction. The present results agree with previous SATURNE measurements and improve the amplitude analysis in the forward direction.