氘化增强KDP/DKDP晶体辐照诱导点缺陷热稳定性的EPR实验研究

魏列宁; 谭放; 任宏凯; 徐明霞; 孙洵; 洪伟

doi:10.11884/HPLPB202638.260176

氘化增强KDP/DKDP晶体辐照诱导点缺陷热稳定性的EPR实验研究

EPR study on deuteration-enhanced thermal stability of radiation-induced point defects in KDP and DKDP crystals

摘要

摘要: 为揭示氘化对KDP晶体紫外损伤微观机制的影响，采用液氮温区X射线辐照结合液氦温区低温电子顺磁共振等温退火监测实验，系统研究了KDP与70%氘代DKDP晶体中辐照诱导点缺陷的演化行为。结果表明：（1）氘化显著增强自束缚空穴热稳定性，DKDP中D₂PO₄⁰在80 K退火后残存率为49.5%，而KDP中H₂PO₄⁰完全消失；（2）DKDP中DPO₄⁻浓度在80～140 K区间持续升高72.8%，形成60 K宽的缺陷积累窗口，而KDP中HPO₄⁻仅升高15.1%后即衰退；（3）间隙D⁰电子中心在100 K退火后残存率72%，高于H⁰的55%。上述差异源于氢氘同位素质量效应导致的零点振动能降低和质子扩散速率抑制，证实氘化延长了关键本征点缺陷寿命，为理解DKDP抗紫外激光损伤性能弱于KDP提供了微观实验依据。

Abstract:
Background Potassium dihydrogen phosphate (KDP) and its deuterated analog (DKDP) are critical frequency conversion crystals in inertial confinement fusion (ICF) laser systems. However, DKDP exhibits inferior UV damage resistance compared to KDP, yet systematic experimental comparisons of radiation-induced point defects under identical conditions remain lacking.
Purpose This study aims to elucidate the influence of deuteration on the thermal stability and evolution dynamics of radiation-induced intrinsic point defects in KDP/DKDP crystals, providing microscopic experimental evidence for understanding their differential UV damage resistance.
Methods Single crystals of KDP and DKDP (70% deuteration) were irradiated with X-rays for 2.5 h at 77 K. Electron paramagnetic resonance (EPR) spectra were acquired at 35 K using a Bruker ELEXYS E500 spectrometer. The samples underwent isothermal annealing from 80 K to 295 K with 10 min holds at each step. Signal intensities were normalized after double integration using EasySpin software.
Results （1）Deuteration dramatically enhances self-trapped hole thermal stability: D₂PO₄⁰ retains 49.5% intensity after 80 K annealing, while H₂PO₄⁰ vanishes completely (<2%), representing a 25-fold stability difference. (2) The DPO₄⁻ concentration in DKDP increases continuously by 72.8%±5.1% over 80–140 K, forming a 60 K-wide "defect accumulation window," whereas HPO₄⁻ in KDP increases only 15.1%±1.8% before decaying. (3) Interstitial D⁰ electron centers exhibit higher survival (72%±4%) than H⁰ (55%±3%) after 100 K annealing.
Conclusions The isotope mass effect reduces zero-point vibrational energy (ΔE₀≈0.057 eV) and suppresses proton transport, confirming that deuteration selectively prolongs hole center lifetimes. This leads to elevated transient defect concentrations in DKDP at room temperature, providing microscopic experimental evidence for its inferior UV damage resistance and suggesting deuteration level is a key parameter for controlling damage resistance in ICF applications.

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