The role of spatial and temporal radiation deposition in inertial fusion chambers: the case of HiPER

Abstract

The first wall armour for the reactor chamber of HiPER will have to face short energy pulses of 5 to 20 MJ mostly in the form of x-rays and charged particles at a repetition rate of 5-10 Hz. Armour material and chamber dimensions have to be chosen to avoid/minimize damage to the chamber, ensuring the proper functioning of the facility during its planned lifetime. The maximum energy fluence that the armour can withstand without risk of failure, is determined by temporal and spatial deposition of the radiation energy inside the material. In this paper, simulations on the thermal effect of the radiation-armour interaction are carried out with an increasing definition of the temporal and spatial deposition of energy to prove their influence on the final results. These calculations will lead us to present the first values of the thermo-mechanical behaviour of the tungsten armour designed for the HiPER project under a shock ignition target of 48 MJ. The results will show that only the crossing of the plasticity limit in the first few micrometres might be a threat after thousands of shots for the survivability of the armour.

Effect of ion flux on helium retention in helium-irradiated tungsten

“…These pulses produce very high thermal loads [8,9] that may result in fatal thermomechanical response of the W components. Appropriate chamber geometry, radiation mitigation strategies, materials engineering and a reduced target yield may lead to an acceptable thermomechanical response [9,10].…”

Materials Research for HiPER Laser Fusion Facilities: Chamber Wall, Structural Material and Final Optics

“…A mm-sized W armor is enough to protect the chamber structural material under this scenario. A previous study by the authors 6 show that 50 MJ targets produce a relatively low increase in the W temperature (1200 K) and an acceptable mechanical deformation. Only thousands of shots might cause an important fatigue and cracking or relevant ion-driven damage but that will not be the case for HiPER4a, which is meant to withstand just a few hundred of energetic explosions.…”

Ultraintense Lasers as a Promising Research Tool for Fusion Material Testing: Production of Ions, X-Rays and Neutrons

“…Whereas neutrons deposit their energy all across the reactor, causing damage in the long run, X-rays and ions are stopped by the inner wall and front optics, having an immediate effect. From a thermomechanical point of view, plasma facing components suffer a sudden increase in their temperature, accompanied by the corresponding stress-strain cycle which occurs in microseconds [2,3]. This process occurs several times per second, causing a considerable fatigue in the material which eventually leads to cracking, mass loss and irauthor's e-mail: jalvarezruiz@gmail.com * ) This article is based on the presentation at the Conference on Inertial Fusion Energy '12. reversible damage.…”

“…Fluxes of particles in the order of 10 20 p/cm 2 /s and energies higher than 1 MW/cm 2 are expected in laser fusion direct drive targets. In order to provide a meaningful assessment of the behavior of plasma facing components under laser fusion conditions, it is important to reproduce those characteristics as precisely as possible [2,13]. To date, ions generated by linear accelerators, plasma guns or ion pulsed sources only provide either the appropriate flux, the right energy range or the adequate pulse duration.…”