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Expanding the capability of reaction-diffusion codes using pseudo traps and temperature partitioning: Applied to hydrogen uptake and release from tungsten
Journal of Nuclear Materials ( IF 2.8 ) Pub Date : 2018-06-04 , DOI: 10.1016/j.jnucmat.2018.05.080
M.J. Simmonds , J.H. Yu , Y.Q. Wang , M.J. Baldwin , R.P. Doerner , G.R. Tynan

Simulating the implantation and thermal desorption evolution in a reaction-diffusion model requires solving a set of coupled differential equations that describe the trapping and release of atomic species in Plasma Facing Materials (PFMs). These fundamental equations are well outlined by the Tritium Migration Analysis Program (TMAP) which can model systems with no more than three active traps per atomic species. To overcome this limitation, we have developed a Pseudo Trap and Temperature Partition (PTTP) scheme allowing us to lump multiple inactive traps into one pseudo trap, simplifying the system of equations to be solved. For all temperatures, we show the trapping of atoms from solute is exactly accounted for when using a pseudo trap. However, a single effective pseudo trap energy can not well replicate the release from multiple traps, each with its own detrapping energy. However, atoms held in a high energy trap will remain trapped at relatively low temperatures, and thus there is a temperature range in which release from high energy traps is effectively inactive. By partitioning the temperature range into segments, a pseudo trap can be defined for each segment to account for multiple high energy traps that are actively trapping but are effectively not releasing atoms. With increasing temperature, as in controlled thermal desorption, the lowest energy trap is nearly emptied and can be removed from the set of coupled equations, while the next higher energy trap becomes an actively releasing trap. Each segment is thus calculated sequentially, with the last time step of a given segment solution being used as an initial input for the next segment as only the pseudo and actively releasing traps are modeled. This PTTP scheme is then applied to experimental thermal desorption data for tungsten (W) samples damaged with heavy ions, which display six distinct release peaks during thermal desorption. Without modifying the TMAP7 source code the PTTP scheme is shown to successfully model the D retention in all six traps. We demonstrate the full reconstruction from the plasma implantation phase through the controlled thermal desorption phase with detrapping energies near 0.9, 1.1, 1.4, 1.7, 1.9 and 2.1 eV for a W sample damaged at room temperature.



中文翻译:

使用伪阱和温度分配功能扩展反应扩散代码的能力:适用于从钨吸收和释放氢

在反应扩散模型中模拟注入和热解吸演化需要解决一组耦合的微分方程,这些方程描述了在等离子体表面材料(PFMs)中原子种类的捕获和释放。t迁移分析程序(TMAP)很好地概述了这些基本方程,该程序可以对每个原子种类不超过三个活动陷阱的系统进行建模。为克服此限制,我们开发了一种伪陷阱和温度分区(PTTP)方案,该方案允许我们将多个非活动陷阱集中到一个伪陷阱中,从而简化了要求解的方程组。在所有温度下,我们都表明使用伪陷阱可以准确地解释溶质中的原子陷阱。但是,一个有效的伪陷阱能量不能很好地复制多个陷阱的释放,每个都有其自身的诱捕能量。然而,保持在高能阱中的原子将在相对较低的温度下保持被俘获,因此存在一个温度范围,在该温度范围内,从高能阱的释放实际上是无效的。通过将温度范围划分为多个段,可以为每个段定义一个伪陷阱,以解决多个高能陷阱的问题,这些陷阱正处于自陷状态,但实际上并未释放原子。随着温度的升高,如在受控的热脱附中,最低的能量陷阱几乎被排空并可以从一组耦合方程式中删除,而下一个较高的能量陷阱变为主动释放的陷阱。因此,每个段都是按顺序计算的,将给定段解决方案的最后一个时间步用作下一个段的初始输入,因为仅对伪释放陷阱和主动释放陷阱进行了建模。然后,将此PTTP方案应用于受重离子破坏的钨(W)样品的实验热脱附数据,该数据在热脱附过程中显示出六个不同的释放峰。在不修改TMAP7源代码的情况下,显示了PTTP方案可以成功建模所有六个陷阱中的D保留。对于在室温下损坏的W样品,我们证明了从等离子体注入阶段到受控的热脱附阶段的完全重构,并具有接近0.9、1.1、1.4、1.7、1.9和2.1 eV的俘获能。在热脱附过程中显示出六个不同的释放峰。在不修改TMAP7源代码的情况下,显示了PTTP方案可以成功建模所有六个陷阱中的D保留。对于在室温下损坏的W样品,我们证明了从等离子体注入阶段到受控的热脱附阶段的完全重构,并具有接近0.9、1.1、1.4、1.7、1.9和2.1 eV的俘获能。在热脱附过程中显示出六个不同的释放峰。在不修改TMAP7源代码的情况下,显示了PTTP方案可以成功建模所有六个陷阱中的D保留。对于在室温下损坏的W样品,我们证明了从等离子体注入阶段到受控的热脱附阶段的完全重构,并具有接近0.9、1.1、1.4、1.7、1.9和2.1 eV的俘获能。

更新日期:2018-06-04
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