A.G. Pieper

Quasi-free scattering in the D(p, pn)p reaction from 15 to 50 MeV

Abstract The D(p, pn)p reaction was studied in a kinematically complete experiment. Comparison with the kinematically equivalent D(p, pp)n reaction shows the surprising result that the measured cross section for the (p, pn) reaction is a factor of seven larger than that of the (p, pp) reaction at the lower energies. The impulse approximation describes the shape of the observed energy spectra, but does not predict the measured magnitude.

Transient irradiation-induced creep of nickel during deuteron bombardment

Abstract The transient irradiation-induced creep of cold worked, high purity nickel was investigated during bombardment with 22 MeV deuterons at 224°C. The results indicate that the transient creep stage was complete after irradiation for 8 h. Microstructural characterization of specimens irradiated for 2, 4, and 8 h revealed a rapid decrease in dislocation density and a similar increase in defect cluster/loop density with increased irradiation time. The measured creep rates were compared with transient creep rates calculated on the basis of the microstructural data. The comparison shows that a climb-controlled glide mechanism was in agreement with the measured transient creep rates.

Simulation of irradiation-induced creep in nickel

Abstract An experimental technique has been developed to simulate neutron irradiation-induced creep by charged particle bombardment. The experimental apparatus permits on-line computer monitoring of experimental parameters while temperature, stress, and flux are maintained at the desired levels. A typical result obtained with a 0.38 mm (0.015 in.) thick, high-purity nickel specimen bombarded with 22 MeV deuterons at 224°C (435°F) and at a stress of 345 MPa (50.12 ksi) is presented. The result demonstrates that charged particle irradiation can successfully be used to simulate irradiation-induced creep reproducibly in materials whose thickness is typical of nuclear fuel cladding.

Study of the (p, pn) reaction in light nuclei

Abstract The (p, pn) reaction on 2H, 6Li, 7Li, 9Be has been studied at 47 MeV bombarding energy. Excitation energy spectra and energy sharing spectra are presented. Fragmentary information on 10B, 11B and 12C was also obtained. Sequential decay contributions to the 6Li(p, pn)5Li∗ reaction suggest an admixture of parentage (α)π( p 1 2 )π( d 5 2 ) for the (3−), 23 MeV excited state of 6Be. A possible 15.5 MeV excited state in 6Be is reported. An extensive study of the 9Be (p, pn)8Be reaction for 45 MeV protons was made. Results for θp = θn = 25°, 30°, 35°, 40°, 45°, 55°, 65°; θn = 40°, θp = 25°, 30°, 35°, 40°, 45°, 55°, 65°; θp/θn = 40°/45°, 38.5° are reported and compared to DWIA calculations. Agreement is good when the lower momentum components of the wave function are sampled, and deteriorates as higher momenta are required. Results are in agreement with the Cohen and Kurath spectroscopic factors for 9Be.

Ion-simulated irradiation-induced creep

Abstract An experimental technique developed to measure the ion-simulated irradiation-induced creep of bulk metallic specimens stressed in tension during charged particle irradiation is described. The experimental apparatus permits on-line computer monitoring of the experimental parameters while temperature, stress, and ion flux are maintained at the desired levels. A typical result obtained with a 0.38 mm (0.015″) thick, high-purity nickel specimen is presented with an analysis of the sources of systematic and random errors.

Method of computing magnet coil current settings for the NRL isochronous cyclotron

Abstract In order for the modern isochronous cyclotron to accelerate ions of different mass and charge state to a variable final energy, the magnetic field in the accelerating region must be precisely tailored. A deviation of 15 G in 18 kG may lead to a loss of beam. The approximate magnetic field of the NRL cyclotron for isochronous accelaration is achieved by iron pole pieces arranged in a 3-sector, hill-valley configuration. This basic field may deviate from that necessary for isochronous acceleration by two or more kG at some radii. Compensation for this field error is achieved by various current-carrying coils wound in the magnet gap. This paper discusses the extent of the magnetic field measurements and the computer program developed at NRL for computing operational parameters (knob-settings) for all current- carrying coils. Innovations introduced in the calculations include minimizing the first harmonic introduced by the extraction elements and imperfections of the iron. In addition, allowance is made for the lack of linear independence of the trim coils as well as for the perturbation of the flutter field due to the trim coils. The influence of the extraction elements on the accelerating region and the function of each element for beam extraction is also discussed. Measurements on the internal and external beam verify the calculations.

Microstructure and Mechanisms of Ion-Simulated Irradiation-Induced Creep of Nickel

The microstructure of cold-worked, high-purity nickel has been investigated following ion-simulated irradiation-induced creep with 22-MeV deuterons and 70-MeV α-particles. The irradiations were conducted at 224°C (435°F),at stresses between 170 and 345 MPa, and at displacement rates between 13 and 30 x 10 - 8 displacements per atom per second (dpa/s). Transmission electron microscopy (TEM) procedures were used to prepare, observe, and photograph the microstructure of the ion-irradiated uniaxial creep specimens and companion unirradiated specimens. Examination of the ion-irradiated microstructure revealed no substantial differences between the deuteron and α-particle irradiated specimens. In all cases, a heterogeneous distribution of defect clusters or small dislocation loops and network dislocations, or both, were observed. A significant reduction in dislocation density from the unirradiated values was seen for the irradiated specimens. It was found that the small loops and defect clusters provided effective obstacles to dislocation motion as evidenced by the bowing of dislocations between adjacent defects. The microstructural results were evaluated in terms of the theoretical mechanisms proposed for irradiation-induced creep and the previously reported creep simulation results for nickel by Hendrick et al. A model based on the climb-controlled glide of dislocations over dispersed obstacles was found to be consistent with the microstructural results and the experimental creep data.

Influence of Magnetic Elements on an Isochronous Cyclotron Field

One of the main advantages of using magnetic field measuring equipment supported external to the cyclotron magnet is the ability to map the field before and after installation of the extraction elements. Field measurements with extraction elements in place are usually precluded by the size of internally mounted field mapping equipment (e.g., a wheel). The magnetic field of the NRL-isochronous cyclotron was measured to full radius before installation of extraction elements. After installation the influence on the magnetic field of each extraction element energized separately was measured. These measurements were used to determine the perturbation of the extraction channel on the isochronous field. Ion orbit calculations were then used to determine necessary field corrections to accelerate ions to the extraction radius. These field corrections are translated to currents needed in each of the various coils via a least squares fitting program.

PROTON INDUCED DEUTERON BREAKUP

Publisher Summary This chapter presents the study of the proton induced deuteron breakup. The study was conducted to map the proton induced deuteron breakup spin observables in a kinematical region. The chapter explains the basic nature of the difference between p-n and p-p quasielastic scattering (QES). It presents the importance of the Pauli principle by an examination of the energy dependence of alpha induced deuteron breakup. The chapter describes the ratio of pn/pp cross sections in the region around 23 MeV. A deuteron breakup theory, to be viable, must fit the cross section magnitudes, the angular distribution, and the spectral shapes for both pp and pn data. It is not adequate for a theoretical approach to examine only a small amount of ρ,ρρ or ρ,ρη data.