Characterization of a Tunable Quasi-Monoenergetic Neutron Beamfrom Deuteron Breakup

A neutron irradiation facility is being developed at the88-Inch Cyclotron at Lawrence Berkeley National Laboratory for thepurposes of measuring neutron reaction cross sections on radioactivetargets and for radiation effects testing. Applications are of benefit tostockpile stewardship, nuclear astrophysics, next generation advancedfuel reactors, and cosmic radiation biology and electronics in space. Thefacility will supply a tunable, quasi-monoenergetic neutron beam in therange of 10-30 MeV or a white neutron source, produced by deuteronbreakup reactions on thin and thick targets, respectively. Because thedeuteron breakup reaction has not been well studied at intermediateincident deuteron energies, above the target Coulomb barrier and below 56MeV, a detailed characterization was necessary of the neutron spectraproduced by thin targets.Neutron time of flight (TOF) methods have beenused to measure the neutron spectra produced on thin targets of low-Z(titanium) and high-Z (tantalum) materials at incident deuteron energiesof 20 MeV and 29 MeV at 0 deg. Breakup neutrons at both energies fromlow-Z targets appear to peak at roughly half of the available kineticenergy, while neutrons from high-Z interactions peak somewhat lower inenergy, owing to the increased proton energy due to breakup within theCoulomb field. Furthermore, neutron spectra appear narrower for high-Ztargets. These centroids are consistent with recent preliminary protonenergy measurements using silicon telescope detectors conducted at LBNL,though there is a notable discrepancy with spectral widths

Neutron Beams from Deuteron Breakup at the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory

Accelerator-based neutron sources offer many advantages, in particular tunability of the neutron beam in energy and width to match the needs of the application. Using a recently constructed neutron beam line at the 88-Inch Cyclotron at LBNL, tunable high-intensity sources of quasi-monoenergetic and broad spectrum neutrons from deuteron breakup are under development for a variety of applications

RADIATION DAMAGE TO BSCCO-2223 FROM 50 MEV PROTONS

The use of HTS materials in high radiation environments requires that the superconducting properties remain constant up to a radiation high dose. BSCCO-2223 samples from two manufacturers were irradiated with 50 MeV protons at fluences of up to 5 x 1017 protons/cm2. The samples lost approximately 75 percent of their pre-irradiation Ic. This compares with Nb3Sn, which loses about 50 percent at the same displacements per atom

Fragmentation cross sections of 28Si at beam energies from 290A MeV to 1200A MeV

In planning for long-duration spaceflight, it will be important to accurately model the exposure of astronauts to heavy ions in the Galactic Cosmic Rays (GCR). As part of an ongoing effort to improve heavy-ion transport codes that will be used in designing future spacecraft and habitats, fragmentation cross sections of 28Si have been measured using beams with extracted energies from 290A MeV to 1200A MeV, spanning most of the peak region of the energy distribution of silicon ions in the GCR. Results were obtained for six elemental targets: hydrogen, carbon, aluminum, copper, tin, and lead. The charge-changing cross sections are found to be energy-independent within the experimental uncertainties, except for those on the hydrogen target. Cross sections for the heaviest fragments are found to decrease slightly with increasing energy for lighter targets, but increase with energy for tin and lead targets. The cross sections are compared to previous measurements at similar energies, and to predictions of the NUCFRG2 model used by NASA to evaluate radiation exposures in flight. For charge-changing cross sections, reasonable agreement is found between the present experiment and those of Webber, et al. and Flesch, et al., and NUCFRG2 agrees with the data to within 3 percent in most cases. Fragment cross sections show less agreement between experiments, and there are substantial differences between NUCFRG2 predictions and the data

Secondary Neutron-Production Cross Sections from Heavy-Ion Interactions between 230 and 600 MeV/nucleon

Secondary neutron-production cross-sections have been measured from interactions of 230 MeV/nucleon He, 400 MeV/nucleon N, 400 MeV/nucleon Kr, 400 MeV/nucleon Xe, 500 MeV/nucleon Fe, and 600 MeV/nucleon Ne interacting in a variety of elemental and composite targets. We report the double-differential production cross sections, angular distributions, energy spectra, and total cross sections from all systems. Neutron energies were measured using the time-of-flight technique, and were measured at laboratory angles between 5 deg and 80 deg. The spectra exhibit behavior previously reported in other heavy-ion-induced neutron production experiments; namely, a peak at forward angles near the energy corresponding to the beam velocity, with the remaining spectra generated by preequilibrium and equilibrium processes. The double-differential spectra are fitted with a moving-source parameterization. Observations on the dependence of the total cross sections on target and projectile mass are discussed