Nicholas Simos

Material Studies for Pulsed High-Intensity Proton Beam Targets

Intense beams for muon colliders and neutrino facilities require high-performance target stations of 1–4 MW proton beams. The physics requirements for such a system push the envelope of our current knowledge as to how materials behave under high-power beams for both short and long exposure. The success of an adopted scheme that generates, captures and guides secondary particles depends on the useful life expectancy of this critical system. To address the key technical challenges around the target of these initiatives, a set of experimental studies have either been initiated or being planned that include (a) the response and survivability of target materials intercepting intense, energetic protons, (b) the integrity of beam windows for target enclosures, (c) the effects of irradiation on the long-term integrity of candidate target and focusing element materials, and (d) the performance of the integrated system and the assessment of its useful life. This paper presents an overview of what has been achieved during the various phases of the experimental effort including a tentative plan to continue the effort by expanding the material matrix. The paper also attempts to interpret what the experimental results are revealing and seeks for ways to extrapolate to the required intensities and anticipated levels of irradiation and it discusses the feasibility of the proposed approaches to achieving such high-performance systems. Further it explores the connection of accelerator target systems with reactor systems in order to utilize experience data that the nuclear reactor sector has acquired over the years.Copyright

Integration of Proton Beam Collimation Scheme in the Spallation Neutron Source (SNS) Accumulator Ring Including Dose and Activation Estimates

This paper details the integration scheme as well as the induced activation by the proton beam clean-up system (collimation) in the accumulator ring section of the Spallation Neutron Source (SNS) accelerator complex. Specifically, the results of the optimization study in terms of satisfying both the optics of the proton beam and the minimization of activation of the accelerator components as well as of the surrounding structure have guided both the design of the components and their integration and are presented in this paper. The resulted collimation scheme is a two-stage clean-up system consisting of proton beam halo intercepting scrapers and appropriate fixed aperture absorbers. The accumulator ring structure consists of the High Energy Beam Transfer (HEBT) line which receives the 1 GeV proton beam from the SNS LINAC accelerator, the accumulator ring itself which compiles the micro-pulses into the final 60 Hz pulse, and the RTBT line that transfers the final proton pulse to the accelerator target. Collimation takes place in all three ring components and along respective straight sections with the exception of the off-momentum particle clean-up in the HEBT line in which off-momentum protons are guided to a stationary absorber outside the transfer line. Given that the activation issues of the collimating structures themselves as well as of the nearby accelerator components (mainly magnets) are similar in all sections of the ring, the activation of components in the ring clean-up system will be discussed in detail in the following sections.© 2004 ASME

Assessment of Spatial Property Variability of the Subsurface in SSI Studies of the Armenian Nuclear Power Plant

This paper addresses issues surrounding soil property variability including uncertainties associated with “best estimate” values and searches for practical ways to assess the impact on the seismic response of a facility, such as a nuclear power plant, resting on it. Specifically, it attempts, using a parametric study, to formulate a probabilistic model that enables the enveloping of uncertainties associated with the soil-structure-interaction component of the seismic problem. The effects of most-likely sources of uncertainty, such as variability of “distinct” soil layer profile and variability of controlling soil properties, are to be addressed by generating a probabilistic profile in which randomization of key parameters that appear to have the most impact on the results of deterministic analyses is implemented. The use of stochastic finite elements and the introduction of correlation functions, in conjunction with finite element discretization of the foundation soil, are explored as means of achieving an enveloped structural response. The on-going evaluation of the Armenian nuclear plant site prompted this study. In order to stress the importance and relevance of the stated goal, the soil-structure-interaction of the nuclear power plant, subject to significant variation of the foundation soil, is examined. The conflicting results of two independent studies of the subsurface provide the basis for the variation range used in this study.Copyright