H. Berg

Phase-shift analysis of pd elastic scattering below break-up threshold

Abstract A phase-shift analysis was performed for pd elastic scattering based on measurements of differential cross sections and proton and deuteron analyzing powers for energies below the break-up threshold. The angular momenta were restricted to l ⩽ 3; j -splitting and channel-spin mixing of the P-phases and the tensor coupling between the S- and D-phases were taken into account. The phase shifts were parameterized by the effective-range formalism and the corresponding parameters were directly deduced from the data. The results are compared with Faddeev calculations in which the Coulomb interaction is treated exactly or as a two-body approximation.

Proton stopping powers in various gases

Abstract The proton stopping powers of H2, He, N2, O2, Ne, Ar, Kr and Xe were measured for proton energies between 60 and 800 keV with an accuracy of about 2%. The protons were scattered off a thin gold foil mounted in the center of a gas-filled scattering chamber. The energy loss in the gas is given by the shift of the elastic peak measured with and without gas filling. The experimental data were fitted using the semi-empirical five-parameter formula of Andersen and Ziegler. Shell corrections were calculated from the measured stopping powers and compared to the theoretical shell-correction calculations of Bonderup which are based on the Lindhard-Scharff model.

Differential cross section, analyzing power and phase shifts for p-3He elastic scattering below 1.0 MeV☆

Abstract Differential cross sections and analyzing powers for the elastic scattering of polarized protons by unpolarized 3 He nuclei have been measured at eight energies between 0.3 MeV and 1.0 MeV for scattering angles θ c.m. = 52.4°–173.3°. The cross-section values were normalized to the Rutherford cross section for proton-krypton scattering. The analyzing powers have been measured with a statistical accuracy of about 0.001. The phase-shift analysis based on these data included all phases for orbital angular momenta l ≦ 1 and the channel-spin mixing parameter for the P waves. An energy parametrization of the phase shifts by an effective-range approximation allowed a simultaneous utilization of all data.

The Giessen polarization facility: II. 1.2 MeV tandem accelerator☆

Abstract A small pressure insulated tandem accelerator with 600 kV terminal voltage was constructed for the application of a polarized ion source of the Lambshift type; thin carbon foils or gas stripping is used for the charge exchange in the high voltage terminal. The calculated ion optical properties were realized in the construction; transmission and energy resolution are sufficient to obtain high intensity polarized beams on target (maximum 0.6 μA protons with P = 0.75) for precision polarization experiments in the 0.2–1.2 MeV energy region.

Differential cross sections and analyzing powers for pd elastic scattering below 1.0 MeV

Abstract Differential cross sections for the elastic pd scattering were measured at seven energies between 0.4 and 1.0 MeV for scattering angles from θc.m. = 44.5° to 149.2°. A mixture of D2 and Kr was used as target gas and the pd differential cross sections were determined relative to those of pKr scattering with a statistical error of Δσ σ ∼5 × 10−3. Analyzing powers for p d scattering were measured at 0.8, 0.9 and 1.0 MeV with a statistical error of ΔAy ∼5 × 10−4.

4He stopping cross sections in H2, He, N2, O2, Ne, Ar, Kr, e, CH4 and CO2

Abstract Helium stopping powers were measured for ten gases in the energy range between 0.1 and 1.1 MeV with a total accuracy of about 2.5%. Additionally, the proton stopping powers in CO 2 and CH 4 were determined. Optimum parameters for the Andersen-Ziegler semi-empirical formula were deduced for all data sets by means of the least-squares method. Stopping-power ratios S He / S p were determined using proton stopping powers for H 2 , N 2 , O 2 and the five inert gases which were measured recently with the same experimental set-up; they show a strong dependence on the target atomic number. The low-energy helium stopping cross sections were filted to the power function S = kE p . Experimental shell corrections were deduced from the measured helium stopping powers and compared with the theoretical shell corrections of Bonderup, whereby different higher-order Z l correction terms were included. The results show that in the energy range investigated it is not possible to obtain a consistent description for all gases.

The Giessen polarization facility: I. Lambshift source

Abstract A source for the production of polarized negative hydrogen or deuterium ions following the Lambshift method is described. A duoplasmatron with expansion cup and extended ion optics is used. The polarization is generated by a diabetic zero field passage of the metastable atoms. For precision experiments the polarization can be switched “on” and “off” with a frequency of 1 kHz by a disturbance with a transverse magnetic field. The quantization axis can be rotated with a Wien filter. All source components are installed in a compact vacuum chamber, which allows high effective pumping. speeds. The overal length of the source including the Wien filter is 1.7 m.With a 10 mm diameter cesium canal typical H − currents of 0.6–0.75 μA ( P =0.7−0.75) and maximum currents of 0.9 μA are obtained.

Proton and helium stopping cross sections in Cl2 and Br2

Abstract Proton and 4He stopping powers for gaseous Cl2 and Br2 were measured in the energy ranges 50–750 keV and 100–1000 keV, respectively, and fitted with the semi-empirical Andersen-Ziegler formula. The peak energies are located near the minima of the oscillating structure as a function of the target atomic number Z2 recently observed by Gowda et al. The stopping-power ratios SHe/Sp for Cl2 and Br2 as a function of ion velocity show a similar behavior as for the adjacent inert gases Ar and Kr. The low-energy helium stopping cross sections were described by the power function S = kEρ, whereby ρ values of 0.5 for Cl2 and 0.67 for Br2 were found.

The Giessen polarization facility: III. Multi-detector analyzing system☆

Abstract Analyzing system with a PDP 11 computer and a digital multiplexer is described. It allows to accept signals from 16 detectors with individual ADCs simultaneously. For measurements of analyzing powers the polarization of the ion beam can be sw tched to zero with a frequency of 1 kHz. The switching operation additionally controls the handling of the detector pulses. The software contains special programs for the analysis of polarization experiments.

Existence of Mott-Schwinger interaction by means of\(\vec p - \)12C elastic scattering

AbstractThe aim of this work was the unambiguous proof of the existence of the Mott-Schwinger interaction. The analyzing power of the