Abstract For the fuel cycles of fusion power plants, highly specialized in-line analytic systems are crucial for efficient process control, monitoring, and accountancy. One of these systems under development is infrared (IR) absorption spectroscopy of liquid hydrogen isotopologue mixtures that can be used for in-line process control and monitoring of cryogenic distillation. The main challenge of this method is the complex calibration procedure since the integral IR absorption strength is nonlinearly correlated with the isotopologue composition. Typical calibration procedures make use of well-known samples produced by mixing atomic pure samples and referenced by p-V-T-measurement. The samples are catalyzed to produce samples containing heteronuclear molecules. By this procedure, one cannot exceed the chemical equilibrium of high temperatures (mass action coefficient Kc<4). Therefore, it is not possible to produce samples with an HD, HT, or DT concentration above 50% by catalysis or natural equilibration. However, in isotope or isotopologue separation, such as in cryogenic distillation, this equilibrium will be regularly exceeded. In the case of IR absorption spectroscopy on liquid hydrogen isotopologues, additional care needs to be taken for calibration since the calibration functions are highly nonlinear. We tested our calibration in the high-purity HD regime (Kc>4) by producing a sample via cryogenic distillation and performing a cross calibration for three systems: Quadrupole mass spectrometry, Raman spectroscopy, and infrared spectroscopy. Therefore, we can also demonstrate that additional calibration points are indispensable in order to improve the systematic uncertainties below the 5% level, and a simple extrapolation from a calibration of Kc < 4 to Kc > 4 will result in a trueness and accuracy exceeding this 5% level.

中文翻译：

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用于氢同位素分析交叉校准的浓缩非平衡 HD

摘要 对于聚变电厂的燃料循环，高度专业化的在线分析系统对于高效的过程控制、监测和核算至关重要。正在开发的这些系统之一是液态氢同位素混合物的红外 (IR) 吸收光谱，可用于低温蒸馏的在线过程控制和监测。这种方法的主要挑战是复杂的校准程序，因为积分 IR 吸收强度与同位素体组成呈非线性相关。典型的校准程序使用通过混合原子纯样品产生的众所周知的样品，并通过 pVT 测量作为参考。样品被催化产生含有异核分子的样品。通过这个程序，不能超过高温的化学平衡（质量作用系数Kc<4）。因此，不可能通过催化或自然平衡产生 HD、HT 或 DT 浓度超过 50% 的样品。然而，在同位素或同位素体分离中，例如在低温蒸馏中，这种平衡将经常被超出。对于液态氢同位素体的 IR 吸收光谱，由于校准函数是高度非线性的，因此需要额外注意校准。我们通过低温蒸馏产生样品并为三个系统执行交叉校准，在高纯度 HD 体系 (Kc>4) 中测试了我们的校准：四极杆质谱、拉曼光谱和红外光谱。所以，