This paper is the fifth in a series of articles on the basic physics of light yield nonproportionality in scintillators. Here, we compare and contrast the nonproportionality as registered by gamma rays and high-energy electrons. As has been noted in the past, these two types of data have different curve shapes (for plots of the light yield against electron or gamma energy). Herein, we show how the experimental gamma nonproportionality curve can be calculated from the electron response by accounting for the distribution of high energy electrons created by the gamma photon via the photoelectric interaction. Similarly, we measure and model the gamma-induced resolution as a function of energy and compare this data to predictions from our model. The utility of the model is explored using data acquired with the scintillators SrI2(Eu), GYGAG(Ce) and CsI(Na).

This paper is the third in a series of articles on the basic physics of nonproportionality in scintillators. Here, we focus on the temperature dependence of six scintillators, NaI(Tl), CsI(Tl), CsI(Na), CeBr 3 , LaBr 3 (Ce), and undoped SrI 2 , and report their nonproportionality curves at -40 ° C, 0 ° C and + 40 ° C. We fit the data to a modified form of our previously employed model, including the competition of carrier trapping with the Onsager-mediated attraction between electrons and holes.

We report measurements of electron response of scintillators, including data on 29 halides, oxides, organics, and fluorides. We model the data based on combining the theories of: Onsager, to account for formation of excitons and excited activators; Birks, to allow for exciton-exciton annihilation; Bethe-Bloch, to relate electron stopping to its energy; and Landau, to describe how fluctuations in the linear energy deposited (dE/dx) lead to nonproportionality's contribution to resolution. In general there is satisfactory agreement with experiment, in terms of fitting the electron response data and reproducing the literature values of resolution. We find that the electron response curve shapes are more affected by the host lattice than by the activator or its concentration.

Recently a collaboration of LLNL and LBNL has constructed a second generation Compton coincidence instrument to study the non-proportionality of scintillators [1]. This device, known as SLYNCI (Scintillator Light-Yield Non-proportionality Characterization Instrument), has an over 30 time higher data collection rate than previous devices enabling complete characterization of a sample with less 24 hours of running time. Thus, SLYNCI enables a number of systematic studies of scintillators as many samples can be processed in a reasonable length of time. The studies include difference in non-proportionality between different types of scintillators, different members of the same family of scintillators, and impact of different doping levels. The results of such recent studies are presented here, including a study on of various alkali halides, and the impact of europium doping level in strontium iodide. Directions of future work will also be discussed.

Over the past century basic nuclear science research has led to the use of radioactive isotopes into a wide variety of applications that touch our lives everyday. Some are obvious, such as isotopes for medical diagnostics and treatment. Others are less so, such as National/Global security issues. And some we take for granted, like the small amount of 241Am that is in every smoke detector. At the beginning of this century, we are in a position where the prevalence and importance of some applications of nuclear science are pushing the basic nuclear science community for improved models and nuclear data. Yet, at the same time, the push by the basic nuclear science community to study nuclei that are farther and farther away from stability also offer new opportunities for many applications. This talk will look at several global security applications of nuclear science, summarizing current R&D and need for improved nuclear data It will also look at how applications of nuclear science, such as to medicine, will benefit from the push for more and more powerful radioactive ion beam facilities.

The Rare Isotope Accelerator (RIA) facility, planned to be built in the USA, will be capable of delivering diverse beams, from protons to uranium ions, with energies from 1GeV to at least 400MeV per nucleon to rare isotope-producing targets. High beam power—400kW—will allow RIA to become the most powerful rare isotope beam facility in the world; however, it also creates challenges for the design of the isotope-production targets. This paper focuses on the isotope-separator-on-line (ISOL) target work, particularly the radiation transport aspects of the two-step fission target design. Simulations were performed with the PHITS, MCNPX, and MARS15 computer codes. A two-step ISOL target considered here consists of a mercury or tungsten primary target in which primary beam interactions release neutrons, which in turn induce fissions—and produce rare isotopes—in the secondary target filled with fissionable material. Three primary beams were considered: 1-GeV protons, 622-MeV/u deuterons, and 777-MeV/u 3He ions. The proton and deuterium beams were found to be about equivalent in terms of induced fission rates and heating rates in the target, while the 3He beam, without optimizing the target geometry, was less favorable, producing about 15% fewer fissions and about 50% higher heating rates than the proton beam at the same beam power.

Neutronics simulations and activation evaluations are currently in progress as part of the pre-conceptual research and development effort for the Rare Isotope Accelerator (RIA). The RIA project involves generating heavy element ion beams with powers up to 400kW for use in a fragmentation target line to produce selected ion beams for physics research experiments. Designing a fragmentation beam dump for RIA is one of the most critical challenges for such a facility. Here, we present the results from neutronics and radiation field assessments for various beam dump concepts that can meet requirements for the RIA fragmentation line. Preliminary results from heavy ion transport including radiation damage evaluations for the RIA fragmentation beam dump are also presented. Initial neutronics and activation studies will be incorporated with other target area considerations to identify important challenges and explore possible solutions.

A compact multiple-beam injector concept is being developed for heavy ion inertial fusion. The design is based on merging high intensity miniature beamlets of a few mA each to form a large beam. In order to minimize emittance growth, the beamlets are kept separated in grids until they are allowed to merge together at 1.2 MeV. With optimized positioning and aiming, the merged beam can quickly match into an electrostatic quadrupole (ESQ) channel. Simulation results have shown that, based on this design, a 1.6 MeV, 0.5 A beam of K/sup +/ ions at the end of the injector has a normalized emittance of approximately 1.0 /spl pi/-mm-mrad which is comparable to that from the previous low current density design. The advantage is a factor of 6 reduction in the combined injector and matching section length.