Micron-Bubble Formation on Polycrystal Tungsten due to Low-Energy and High-Flux Helium Plasma Exposure

Abstract

Surface modification of polycrystal tungsten due to low-energy and high-flux helium plasma exposure was investigated. Micron-sized holes and bubbles were formed on the surface at a surface temperature of 2200 K even when the incident ion energy of helium was 10 eV. Hole formation was significantly reduced on the surface when the incident ion energy of helium was around 5 eV and no surface modification was seen at less than 5 eV. Coalescence of micron-sized helium bubbles was observed in the cross section of a W sample.

A stochastic differential equations approach for the description of helium bubble size distributions in irradiated metals

“…By adding the product of these stochastic terms to (1) and (2), and performing basic algebraic manipulations, we can re-express them in a simplified stochastic differential form as…”

“…The literature is rich with experimental data on the response of tungsten to ion irradiation. Over a very large temperature range, tungsten samples exposed to lower energy (<50 keV) helium implantation exhibit severe surface damage as helium bubbles coalesce at the surface [1,2]. Prolonged exposure leads to the formation of a coral-like surface morphology, risking contamination of the fuel mixture [3].…”

Is It Possible to Avoid of Blister Formation in the Diagnostic Mirrors?

“…В 2005-2007 гг. были опубликованы результаты ряда экспериментов [16,17] и ряд докладов на конференциях [18].…”

“…При микроволновой мощности ~400 Вт и давлении рабочего газа ~3·10 -2 Па параметры плазмы: n e ~ 10 10 cм -3 , T e  5 эВ. Испытываемые образцы крепились на подвижном коаксиальном, охлаждаемом водой держателе, вводились через шлюз в ваку- при экспозициях: a1 -1000 с, б1 -10 000 с и в1 -75 000 с; а2, б2, в2 -вид поперечных сечений каждого образца [18] 2 мкм а1 б1 в1 в2 б2 а2 умную камеру вдоль оси системы и закреплялись вне маг-нитной пробки. На держатель образца подавалось отрица-тельное напряжение для ускорения ионов плазмы к поверх-ности зеркала, либо фиксированное (между 0,05 и 1,5 кВ), либо изменявшееся во времени с частотой 100 Гц.…”

Microscopic Deformation of Tungsten Surfaces by High Energy and High Flux Helium/Hydrogen Particle Bombardment with Short Pulses

“…In ITER conditions, strong erosion and radiation damage on the divertor surface, caused by high heat and particle loading as a result of disruptions and edge localized modes (ELMs), are critical issues to consider in the preparation of divertor armors of good thermal and mechanical properties. To this end, in previous studies heat loading tests made by electron beam machines [1,2] and particle loading tests made by plasma machines [3,4] were performed. However, evaluation of synergistic loading effects of high heat and helium/hydrogen with short pulses is necessary for confirming the reliability of tungsten armor tiles.…”