P. Sauvan

First IFMIF/EVEDA Radioprotection Studies for the Preliminary Design of the Accelerator Beam Dump

A preliminary beam dump cartridge design has been proposed recently for the IFMIF-EVEDA accelerator. Copper was the material chosen for the beam stop. In this paper we investigate the possibility of designing a practical shielding for the proposed cartridge so that it can offer an acceptable radioprotection response during both beam-on and beam-off phases. The radioprotection analysis is performed for the whole beam dump component located inside the already designed accelerator vault. A comprehensive methodology has been proposed to deal with the problem. Special attention has been paid to the treatment of the neutron source and a significant effort has been devoted to validation purposes. It is justified that prompt and residual dose rates can be provided with a reasonably conservative margin. A base line shielding consisting of a 1 m water tank and a concrete shield of 1 m thickness in front of the tank can be a good approach to fulfill the radioprotection requirement assigned to the beam-on phase. This approach will not be acceptable for the beam-off but it is seen that a feasible solution can be reached by adding a plug at the entrance of the beam dump.

Development of the R2SUNED Code System for Shutdown Dose Rate Calculations

R2SUNED is a code system implementing the mesh-based Rigorous-two-step method for shutdown dose rates calculations, making use of MCNP and ACAB codes. In addition to the most relevant features of state-of-the-art R2S systems, novel and unique features have been implemented in R2SUNED to overcome limitations common to the current mesh-based R2S implementations. One of particular interest is the cell-under-voxel approach intended to address most of the issues associated with the conventional averaging technique used in the neutron flux determination. The underlying idea is to identify the cells enclosed in each voxel and calculate the average value of the neutron flux within each cell fraction. Subsequently, the activation of each material, filling the cell delimited by the voxel, is calculated using the neutron flux evaluated in the corresponding cell. This capability enables to properly resolve the strong spatial gradients of the neutron flux independently of geometrical considerations. Another relevant feature is that a flexible decay gamma source sampling has been incorporated to assure an efficient decay gamma transport in a vast diversity of problems. A verification of R2SUNED has been addressed on the ITER computational shutdown dose rate benchmark. It is highlighted both the limitations of voxel averaged neutron flux standard approach, and the ability of R2SUNED to overcome this issue. The excellent agreement of the results with those obtained using a mesh matching perfectly the geometry tells that R2SUNED performs correctly. Finally, a description of the most representative applications carried out with R2SUNED is provided for fusion relevant facilities.

Radioprotection Analysis for the High Energy Beam Transport Line of the Accelerator Facility of IFMIF

Abstract The safety analysis for the design of the IFMIF accelerator facility is an ongoing task within the IFMIF project, and the radioprotection analysis is one of the main sections of this task. The high energy beam transport line is a very sensitive section since it contains intense radiation sources. This work presents the radiological analysis of its current layout, and the design of local radiation shields, in order to meet project dose limits. These limits are established to protect workers in neighboring rooms during operation and to ensure unrestricted access for maintenance operations.

Sensitivity to Nuclear Data in the Radioprotection Design of the LIPAC (IFMIF/EVEDA) Beam Dump

Abstract Linear IFMIF Prototype Accelerator (LIPAC) is the prototype accelerator of the Engineering Validation and Engineering Design Activities (EVEDA) phase of the International Fusion Materials Irradiation Facility (IFMIF) project. The EVEDA phase is a first IFMIF step devoted to the construction of prototypes of the main units. The deuteron beam of LIPAC (125 mA, 9 MeV) is stopped by a conical copper beam stop, giving rise to neutron and photon sources that must be shielded to comply with dose requirements. A reliable characterization of these secondary sources is a mandatory task. The built-in-semi-analytical nuclear models used by advanced Monte Carlo transport codes as Monte Carlo N-Particle eXtended (MCNPX) or Particle and Heavy Ion Transport code System (PHITS) have been demonstrated as unreliable for describing deuteron interactions and secondary particle production at these low energies. The use of reliable external nuclear data is consequently necessary in the design of the LIPAC shielding. In particular, the TENDL-2010 library has been compared with recently published experimental data demonstrating its reliability for deuteron interaction on copper at 9 MeV. The Monte Carlo Universidad Nacional de Educación a Distancia (MCUNED) code has been developed to make use of external nuclear data, and its use with the TENDL-2010 library has proven very satisfactory for LIPAC radioprotection analysis. The impact on radioprotection tasks in LIPAC when the unreliable nuclear models mentioned above are used is discussed.

X-ray Spectroscopy of Hot Dense Plasmas: Experimental Limits^ Line Shifts & Field Effects

High‐resolution x‐ray spectroscopy is capable of providing complex information on environmental conditions in hot dense plasmas. Benefiting from application of modern spectroscopic methods, we report experiments aiming at identification of different phenomena occurring in laser‐produced plasma. Fine features observed in broadened profiles of the emitted x‐ray lines and their satellites are interpreted using theoretical models predicting spectra modification under diverse experimental situations.

Spectroscopic diagnostics of plasma interaction with an external oscillatory field

The paper presents an advanced analysis of the experimental Al Heβ emission from aluminium plasma created by one ps-laser beam and then subjected to another ps-laser beam when the pulse of the first laser beam was already off. The paper has two equally important goals. The first goal is to present an overview of the general principles of spectroscopic diagnostics of plasmas containing a quasi-monochromatic electric field (QEF) and to clarify some erroneous/confusing statements in the theoretical literature. The second goal is to model spectroscopic signatures of the strong QEF caused by the second laser beam in the plasma and thus to provide an adequate interpretation of the experimental spectral line profiles. The second goal has been achieved via advanced simulations coupling the code based on the Floquet–Liouville formalism with the particle-in-cell kinetic code that provides a spatial distribution of the QEF in the plasma. In this way—by using ultra-high resolution K-shell spectroscopy—the paper has established a link between two research communities: the one dealing with laser–plasma interactions and the other one dealing with atomic processes in plasmas.

Stark Profiles In Plasmas Interacting With A Strong Oscillatory Quasi‐Monochromatic Electric Field

This paper presents an advanced analysis of the spectroscopic signatures of the interaction of a strong oscillating Quasi‐monochromatic Electric Field (QEF), generated by a high‐power short‐pulse laser, with a preformed laser‐produced plasma. The computation of a synthetic spectrum emitted by such plasmas requires the calculation of the Stark line shape in the presence of a QEF and the evaluation of the QEF intensity profile throughout the line of sight in the plasma. As for the Stark profiles in hot dense plasmas submitted to a strong QEF, they are calculated using the so‐called Floquet‐Liouville formalism. In this formalism, the Liouville space, usually used for the calculation of Stark profiles in dense plasmas, and the Floquet theory, developed to solve time‐periodic problems, have been joined together to solve the time‐dependent Liouville equation. A second kind of simulations involving Particle‐In‐Cell PIC kinetic simulations is required for the calculation of the QEF inhomogeneous intensity and the...