Deuterium Desorption Research Articles

Effects of Scandium doping on the deuterium absorption and desorption behavior of titanium films

Understanding the effects of Scandium (Sc) on the hydrogen absorption and desorption capabilities and the underlying mechanisms within Ti–Sc alloys is crucial for their applications as hydrogen storage materials. In this study, we explore the influence of Sc on deuterium (D) behavior in Titanium (Ti) films through a combination of experimental characterization and theoretical simulations. The Sc-doped Ti films with different Sc ratio were prepared using magnetron sputtering. Our findings indicate that Sc doping raises the D absorption temperature from 350 °C to 500 °C, and the Sc-doped Ti deuteride films exhibit higher apparent activation energies and temperatures for D desorption. Results from both experiments and DFT calculations indicate that these phenomena are attributed to the atomic size effect, in which the larger Sc atoms reduce the Ti–H spacing, thereby strengthening the interaction between the adjacent Ti atoms and H atoms. The enhanced interaction presents a greater challenge for H atom diffusion within α-Ti and complicates the dissociation of TiH2. This study provides a vital theoretical and experimental basis for understanding the effects of Sc doping on the hydrogen absorption and desorption properties in titanium alloys.

Structure analysis (XRD and Neutrons) and hydrogen storage properties of Hf1-xTixNbVZr BCC high entropy alloys

The hydrogen storage properties of Hf1-xTixNbVZr high entropy alloys (HEAs) synthesized by arc melting have been investigated. The first hydrogenation of the alloys was performed at room temperature under 20 bars of hydrogen pressure. Results show an increase in gravimetric hydrogen content with Ti substitutions. Upon hydrogenation, the multiphase alloys (x = 0 and x = 0.25) exhibit a combination of faces-centred-cubic (FCC) hydride and C15 Laves phases, while single-phase alloys (x = 0.5, 0.75, and 1) display FCC structures.The crystal structure evolution during dehydrogenation of HfNbVZr (x = 0) and TiNbVZr (x = 1) HEAs was examined using in-situ neutron diffraction. The analysis demonstrates temperature-dependent desorption behaviour, with HfNbVZr displaying lower desorption temperatures compared to TiNbVZr. Additionally, in-situ neutron diffraction experiments during deuterium desorption indicate a two-step phase transition from FCC dihydride to BCT monohydride, followed by a transition to BCC.

Cathode cooling effects on the neutron production rate in the glow discharge type of fusion neutron source

Fusion reactions on the cathode surface of glow discharge deuterium–deuterium fusion neutron sources contribute significantly to the neutron production rate (NPR). While the NPR shows a linear relationship with current in the low current regime, a rise in cathode temperature in the high-current regime causes stagnation of the NPR. This tendency may be caused by high-temperature-induced desorption of deuterium on the cathode. This study aims to clarify the relationship between NPR and deuterium desorption. The present study utilized a water-cooling system to prevent deuterium desorption on the cathode. A stainless-steel 304 cathode and a diamond-like carbon (DLC)-coated cathode were tested. The cooling system kept the cathode temperature below 315 K throughout the experiment. In the case of the DLC-coated cathode, the water-cooling system improves the NPR in a high-current regime (30 mA or more in the present study). At 50 kV and 60 mA, the NPRs were 1.87 × 106 and 8.39 × 105 (n/s), with and without water cooling, respectively. Furthermore, without the cooling system, the NPR correlation with the cathode temperature indicates good agreement with the estimation model of deuterium desorption on the DLC-coated cathode. This study demonstrates that suppression of deuterium desorption in the cathode improves NPR, especially in the high-current regime.

Influence of heating rate and storage condition on thermal desorption of deuterium in tungsten

The retention of hydrogen isotopes in tungsten has been a critical issue in future fusion facilities. Thermal desorption spectroscopy (TDS) is a common method for the studies of hydrogen isotope retention. To explore the effect of heating rate in TDS measurement, a series of deuterium (D) desorption experiments with different heating rates were conducted. The results were compared with TMAP7 (Tritium Migration and Analysis Program, version 7) simulations and Kissinger's theory. An empirical expression for the analysis of desorption spectra with different heating rates was derived. The expression was verified in another set of experiments on helium (He) desorption. Furthermore, the formation of molecules containing D atoms during TDS measurements was investigated. Specimens exposed to D plasma were stored in air and vacuum respectively for three months prior to desorption experiments. Signals of H, H2, HD, D2, HDO and D2O were detected. The reasons for the formation of these species were explored.

Effect of porosity on deuterium retention in titanium thin film

Abstract The absorption process of deuterium in titanium was studied in titanium film produced in two different types of copper substrate, one was a polished copper substrate and the other one was chemically etched copper substrate. Titanium film was produced by thermal evaporation method. It was activated at a temperature of 500 0C followed by deuteration at room temperature. Titanium film was characterized by XRD for crystallographic information, SEM for surface morphology, RGA for deuterium desorption studies and weight measurement for D/Ti ratio. The difference in porosity of both the samples is confirmed from XRD analysis and SEM images. Different diffusion process is observed in two different substrates from the RGA spectra. Presence of multiple trap sites in the thin film of both the substrates is observed from the RGA spectra. From the weight measurement, D/Ti ratio in polished substrate is found to be 1.03 whereas in case of chemically etched substrate it is 1.54.

Deuterium uptake, desorption and sputtering from W(110) surface covered with oxygen

Rate equation modelling is performed to simulate D2 and D2+D2+ exposure of the W(110) surface with varying coverage of oxygen atoms (O) from the clean surface up to 0.75 monolayer of O. Density Functional Theory (DFT) calculated energetics are used as inputs for the surface processes and desorption energies are optimized to best reproduce the Thermal Desorption Spectrometry (TDS) experiments obtained for D2 exposure. For the clean surface, the optimized desorption energies (1.10 eV–1.40 eV) are below the DFT ones (1.30 eV–1.50 eV). For the O covered surface, the main desorption peak is reproduced with desorption energies of 1.10 eV and 1.00 eV for 0.50 and 0.75 monolayer of O respectively. This is slightly higher than the DFT predicted desorption energies. In order to simulate satisfactorily the total retention obtained experimentally for D2+D2+ exposure, a sputtering process needs to be added to the model, describing the sputtering of adsorbed species (D atoms) by the incident D ions. The impact of the sputtering process on the shape of the TDS spectra, on the total retention and on the recycling of D from the wall is discussed. In order to better characterize the sputtering process, especially its products and yields, atomistic calculations such as molecular dynamics are suggested as a next step for this study.

The effect of High-Temperature Pre-Damage on Vacancy-Type defects and deuterium retention in tungsten

This work investigated tungsten samples that were pre-damaged at room (300 K) and high temperatures (573 and 873 K) using 3.5 MeV iron ions and then exposed to the high-flux deuterium plasma. The vacancy-type defects and the behavior of deuterium retention in the investigated tungsten were characterized and compared to study the effect of high-temperature pre-damage. Results of slow positron annihilation with Doppler broadening spectroscopy indicate the introduction of numerous defects by the room-temperature damage and the formation of larger-sized vacancy clusters by the high-temperature pre-damage. Surface observation demonstrates that the pre-damage at room temperature effectively suppressed the formation of intra-granular blisters, while the pre-damage at high temperature did not exhibit such a significant suppression effect on blister formation. Thermal desorption results show that pre-damage at room temperature significantly increases deuterium desorption. Pre-damage at high temperatures also strengthens deuterium desorption, not as significantly as room-temperature pre-damage, and meanwhile produces additional desorption at around 900 K. These results indicate differences between room-temperature and high-temperature pre-damage in the generation of defects and their impact on deuterium retention. Compared to room-temperature pre-damage, high-temperature pre-damage tends to generate defects with a larger average size, weakening the suppression effect on deuterium aggregation and blistering within the grains of tungsten, reducing the quantity of deuterium trapping sites and producing higher-energy deuterium traps.

Kinetics of hydrogen absorption/desorption in the Zr-2.5Nb alloy.

The Zr-2.5Nb alloy is a typical pressure tube material in heavy water nuclear reactors, and an increase of hydrogen isotope content in the alloy during service can pose major safety risks; hot vacuum extraction-mass spectrometry is an efficient method for evaluating hydrogen isotope concentrations in the Zr-2.5Nb alloy. This work investigates the kinetics and thermodynamic properties of deuterium (D) absorption and desorption of the Zr-2.5Nb alloy using the constant volume adsorption method and the hot vacuum extraction method. In addition to the previously reported volume contraction model, it was observed that at 600 °C and above, the reaction between D2 and Zr-2.5Nb is dominated by diffusion, while the reaction is predominantly influenced by surface adsorption and dissociation below 600 °C. Phase transition sequence of Zr-2.5Nb deuterides during non-isothermal desorption was established using quantitatively calibrated thermal desorption spectra combined with the phase transition process of deuteride decomposition. These results can provide important references for optimizing the process parameters of the hot vacuum extraction-mass spectrometry method.

Air contamination and its effect on deuterium desorption in liquid lithium

The clean wall condition in tokamak devices can be achieved by utilizing the active chemical property of lithium (Li). This also exposes Li to air contamination even when protected by inert gas. To determine whether air contamination affects the retention of hydrogen isotopes in Li, the desorption performances of deuterium (D2) in liquid Li with D/Li ratios of 4.1 mol.%, 2.5 mol.%, and 0.6 mol.% were compared. At a D/Li ratio as low as 0.6 mol.%, the results revealed a significant change in the desorption temperature of D2 by Li contaminants. The ratio of contaminants to D2 in Li was discovered to be important. In this regard, the influence of N2, O2, and H2O (accounting for 15 mol.% of D2) on the desorption performance of D2 in liquid Li was discussed. Both H2O and N2 preabsorbed in liquid Li could react with D2, leading to the changed desorption temperature of D2. Notably, the H2O present in Li consumed all of D2 via reaction, whereas the same amount of N2 as H2O could only react with a part of D2. However, the effect of O2 on the desorption temperature and the effect of impurities on the desorption amount of D2 were not obvious. The impacts of the findings of this work on the retention and extraction of hydrogen isotopes in Li may be further explored to prompt the application of Li in fusion devices.

Numerical simulation of cathode-spot crater formation and deuterium desorption process on hydrogen titanium cathode with flux boundary conditions and different impregnation degree

In this paper, the crater formation process of single cathode spot on hydrogen titanium electrode is modeled. In this model, combined with the deuterium diffusion equation, the flux boundary condition was considered to calculate the cathode spot desorption rate with different impregnation degree, and the deformation process of the cathode spot crater was simulated by a hydrodynamic model. The simulation results show that the current, size, and depth of a single cathode spot crater tend to decrease with increasing impregnation degree, which is consistent with many related experimental results. The simulation result shows that the desorption of deuterium in a single cathode spot crater mainly occurs in the ignition stage, and the positions of desorption are successively distributed in the liquid metal flow area on the side wall of the crater and the high temperature area in the center of the crater. The desorption rate of deuterium drops rapidly after cathode spot quenching. At the same time, the increase of arc current and impregnation degree can improve the deuterium desorption rate of a single cathode spot.

Isotope effect on hydrogen storage properties of Ti and Nb co-substituted ZrCo alloy

In our previous study, we showed that the anti-disproportionation properties of Zr0.8Ti0.2-xNbxCo alloys were remarkably improved by the co-substitution of Zr with Ti and Nb. However, the practical application of these alloys in handling of hydrogen isotopes necessitates the first hand knowledge of hydrogen isotope effect. Herein, we discuss the hydrogen isotope effect on storage properties of Zr0.8Ti0.2-xNbxCo alloys. According to PCT measurements on desorption of deuterium from the Zr0.8Ti0.2-xNbxCo deuterides and comparison with corresponding hydrides, the deuterides require relatively lower temperature to achieve the desired equilibrium pressure. DSC measurements reveal a significant decrease in the activation energy for hydrogen/deuterium desorption reactions when Zr is substituted with Ti and Nb. Furthermore, it is observed that the activation energy of deuterium desorption is lower than the desorption of hydrogen from analogous hydride. Isotope effect on isothermal disproportion studies on Zr0.8Ti0.2-xNbxCo-deuterides divulge that Zr0.8Ti0.2-xNbxCo-deuterides have superior anti-disproportionation properties over corresponding hydrides, and further improvement is anticipated for the Zr0.8Ti0.2-xNbxCo-tritides. This study revealed the significant impact of Ti and Nb co-substitution on hydrogen isotope storage properties of Zr0.8Ti0.2-xNbxCo alloys, making them potential candidates for handling hydrogen isotopes.

Dynamics of deuterium retention and desorption from plasma-facing materials in fusion reactor-relevant conditions

Hydrogen isotopes retention and desorption during and after discharges in fusion devices are still not well understood due to the complex device conditions and limitations of in-situ diagnostics and measurements. We simulated well-diagnosed recent experiments at the DIII-D facility to benchmark our ITMC-DYN integrated package of modeling deuterium diffusion, retention, and desorption during and after D discharge irradiation. Modeling results were compared with detail experimental data of D desorption fluxes for various irradiation conditions. We predicted the temporal evolution of free and trapped D distribution in tungsten (W) plasma-facing material (PFM). Effects of key parameters namely diffusion coefficient, recombination rate, trapping energies against different defect types, were examined in these simulations. Existing experimental data of these parameters in literature varies significantly which makes it harder to identify key mechanisms and physics responsible for hydrogen isotope retention and desorption. The purpose of this work is to accurately simulate recent well-diagnosed reactor experiments given the uncertainties in such parameters and identify mechanisms responsible for the retention and desorption. We implemented the best identified diffusion, recombination, and trapping parameters in ITMC-DYN package that integrate both various collisional and thermal processes. We predicted, for example, that sample cooling between discharges in DIII-D operations can significantly affect the spatial distribution of trapped D in W under reactor irradiation conditions. Correct prediction of desorption spectra from samples irradiated during 10 DIII-D discharges showed that up to 35% of D can be retained in high binding energy defects such as vacancy clusters or voids.

Spectroscopic investigation of the tungsten deuteride sputtering in the EAST divertor

• Behaviors of WD molecules sputtering were compared with W atoms sputtering in EAST. • Existence of energy threshold for WD sputtering in EAST was discussed. • Influences of heat flux and D retention on WD sputtering in EAST were analyzed in detail. Physical sputtering caused by particle bombardment is believed to be the main erosion mechanism of W materials in fusion devices, in which W atoms are the sputtering products. However, the tungsten deuteride molecule (WD) spectra have been observed in both TEXTOR and ASDEX Upgrade, which was believed to be the product of chemically assisted physical sputtering (CAPS), a new sputtering mechanism that has been proposed in recent years. In this paper, we report the spectroscopic observation of WD molecules in the EAST W divertor. The behaviors of WD molecules sputtering are compared with W atoms sputtering via the spectral measurements of the ro-vibrational band emission of WD 6 Π → 6 Σ + in the spectral range between 673 nm and 678 nm and the WI line emission at 400.9 nm. The physical sputtering characters and chemical sputtering characters of WD molecule sputtering were confirmed in EAST. The measurements in EAST showed that there is an energy threshold for WD molecules sputtering and that the sputtering energy threshold of WD molecules is smaller than that of W atoms. Furthermore, the dependence of WD molecule sputtering efficiency (the absolute WD photon flux ( Ph WD ) normalized to the particle flux ( Γ ion ) reaching the target with a constant T e ) on impact energy and heat flux were studied, presenting significantly different behaviors compared with W atom sputtering. In addition, it is found that the decrease of WD sputtering efficiency with the heat flux is accompanied by the rise of the photon flux of D δ (410.06 nm) normalized to the particle flux ( Γ ion ) at the divertor target, which may imply the enhanced deuterium desorption at the W surface. The further increase of heat flux hitting the target surface could elevate the surface temperature and benefit the deuterium release from the surface, which may influence the formation of WD molecules at the surface layer.

Deuterium retention and desorption behavior of W-Ta-Cr-V high entropy alloy

Deuterium retention and desorption behavior of W-Ta-Cr-V films under deuterium plasma irradiation were studied. The W-Ta-Cr-V films were prepared on the molybdenum (Mo) substrate by magnetron sputtering. Subsequently, all films annealed at 1000 °C were exposed to deuterium plasma at a flux of 8.13 × 1019 D/m2·s for 9 h to achieve an irradiation fluence of 2.63 ×1024 D/m2. Electron backscattered diffraction (EBSD) was used to characterize the texture and average grain size of films. Doppler broadening spectrometry of positron annihilation (DBS-PA) was carried out with an energy-variable slow positron beam to detect the concentration of vacancy-type defects in the films. The results suggest that there are fewer vacancy-type defects inside W-Ta-Cr-V grains. Deuterium retention and the desorption behavior of W-Ta-Cr-V were studied by compared to pure tungsten films. In the 300–800 K temperature range, the peaks of thermal desorption spectroscopy (TDS) of W-Ta-Cr-V films are substantially consistent with that of the W films. Notably, in the range of 800 K-1000 K, W-Ta-Cr-V film has no thermal desorption peak. We attribute this to the large lattice distortion and low vacancy formation energy, which inhibit the growth of voids inside the grains of W-Ta-Cr-V films. The total deuterium retention of W-Ta-Cr-V films is compared with that of W films. It is measured by TDS that the deuterium retention of W-Ta-Cr-V films is nearly 5 times that of W films. Based on the analysis of the TDS spectra, the higher deuterium retention in W-Ta-Cr-V films is due to the more grain boundary defects.

EFFECT OF IRRADIATION AND DEUTERIUM BEHAVIOR IN LI-BASED TRITIUM BREEDING CERAMICS

The behavior of implanted deuterium in advanced lithium orthosilicate (Li4SiO4) pellets with addition of lithium metatitanate (Li2TiO3), and in reference Li4SiO4 pellets, has been investigated. Thermal desorption (TD) spectroscopy was used to study the deuterium interaction with radiation defects in materials. Computational evaluation of deuterium desorption within the framework of the diffusion-trapping model allowed to associate characteristics of experimental TD spectra with specific trapping sites in the material. It was found that deuterium desorption is limited mainly by intragranular diffusion of deuterium and its trapping by radiation defects associated with Li-vacancy traps. Deuterium gas release from both ceramics demonstrated similar trend indicating weak dependence of deuterium trapping behavior on phase composition. The change of the morphology and elemental composition of the pellets surface has been analyzed. SEM examination indicated that ion irradiation and subsequent thermal desorption annealing of two-phase ceramics leads to an increase in surface destruction processes.

A comparative study on the hydrogen dissolution and release behaviors in the zirconate proton conductors by TDS and TMAP4 analysis

Proton-conducting oxides are potential materials for electrochemical devices such as fuel cells, hydrogen pumps, hydrogen sensors, and the tritium purification and recovery system in nuclear fusion reactors. The hydrogen concentration in oxide materials is important, but its precise measurement is difficult. In this study, thermal desorption spectroscopy (TDS) was used to investigate hydrogen dissolution and release behavior in proton-conducting oxides, yttrium (Y), and cobalt (Co) doped barium-zirconates in the temperature range of 673-1273 K using deuterium (D2) and heavy water (D2O). Specimens were prepared with conventional powder metallurgy: the powder of three zirconates, BaZr0.9Y0.1O3-a (BZY), BaZr0.955Y0.03Co0.015O3-a (BZYC), and CaZr0.9In0.1O2.95 (CZI) was pressed into discs and fired in the air at 1873 K for 20 h. The densities of the sintered BZY, BZYC, and CZI specimens were 98 percent, 99.7 percent, and 99.5 percent of the theoretical densities respectively. XRD, SEM, and EDX were performed for the structural and morphological analysis of the sintered samples. From TDS measurement, a similar trend of temperature-dependent hydrogen solubility was obtained for all samples compared to the tritium imaging plate (TIP) methods literature data of HT- and DTO-exposed samples. To compare the experimental results of the deuterium desorption profile derived by TDS analysis, the simulation code of the tritium migration analysis program, version 4 (TMAP4) was employed.

Study of isotope effect on dehydrogenation kinetics of Pd based alloys using differential scanning calorimetry

Owing to the large hydrogen isotope effect, palladium and palladium based alloy are of great technological importance for their application in separation of hydrogen isotopes. The present study deals with the investigation of isotope effect on hydrogen desorption kinetics of Pd, Pd0.77Ag0.23 and Pd0.77Ag0.10Cu0.13 alloys, using non-isothermal method by employing Differential Scanning Calorimetry (DSC). Pd0.77Ag0.23 and Pd0.77Ag0.10Cu0.13 alloys were prepared by arc melting method and characterised by XRD, TXRF and EDS. Both the alloys are found to have FCC phase similar to Pd lattice. Prior to kinetic measurements, samples were activated by hydriding-dehydriding method. Hydrogen/deuterium desorption kinetic measurements were carried out at four different heating rates (8, 12, 16 and 20 K/min) and Kissinger plots were constructed from peak temperature of DSC curves. Activation energies for hydrogen/deuterium desorption from the corresponding hydride/deuteride were calculated from the slope of Kissinger plot which follows the order; Pd > Pd0.77Ag0.23 > Pd0.77Ag0.10Cu0.13. Activation energy for deuterium desorption was found to be lower than that of hydrogen desorption and significant isotope effect was observed for the Pd0.77Ag0.10Cu0.13 alloy which makes it a favorable candidate material for its application in hydrogen isotope separation, employing self-displacement gas chromatography.

Surface oxygen versus native oxide on tungsten: contrasting effects on deuterium retention and release

We performed a direct comparison of deuterium retention and release from tungsten in presence or in absence of oxygen impurities. A single crystal of W(110) was used to prepare tungsten with four different surface states: with its native oxide, atomically clean, covered with half a monolayer of oxygen atoms, and covered with three fourths of a monolayer of oxygen atoms. For a D ion fluence of 3 × 1021 D+ m−2 implanted at 300 K, deuterium retention was highest with the native oxide, lowest with three fourths of a monolayer of oxygen atoms at the surface and intermediate for the clean surface. This counterintuitive result is explained by a different localization of deuterium retention in these samples. For tungsten with its native oxide, deuterium retention occurs solely in the bulk, i.e. below the first atomic plane of the surface. For clean tungsten, deuterium retention occurs in part at the surface and sputtering should play a role. For tungsten with a sub-monolayer surface coverage of oxygen atoms, a transition from surface to bulk retention is observed above half a monolayer of adsorbed oxygen. Striking differences in desorption peak(s) temperature(s) are observed between D ion-implanted samples and D2 molecules-exposed samples. These results highlight the importance of the (near-) surface localization of oxygen and deuterium on the temperature dependence of deuterium desorption rate i.e. on the fusion fuel recycling coefficient.

Comparative Studies of Hydrogen Dissolution and Release Behavior in Zirconate Oxides by TDS and TMAP4 Analysis

Proton-conducting oxides are potential materials for electrochemical devices such as fuel cells, hydrogen pumps, hydrogen sensors, and the tritium purification and recovery system in nuclear fusion reactors. The hydrogen concentration in oxide materials is important, but its precise measurement is difficult. In this study, thermal desorption spectroscopy (TDS) was used to investigate hydrogen dissolution and release behavior in proton-conducting oxides, yttrium (Y), and cobalt (Co) doped barium-zirconates in the temperature range of 673-1273 K using deuterium (D2) and heavy water (D2O). Specimens were prepared with conventional powder metallurgy: the powder of three zirconates, BaZr0.9Y0.1O3-a (BZY), BaZr0.955Y0.03Co0.015O3-a (BZYC), and CaZr0.9In0.1O2.95 (CZI) was pressed into discs and fired in the air at 1873 K for 20 h. The densities of the sintered BZY, BZYC, and CZI specimens were 98 percent, 99.7 percent, and 99.5 percent of the theoretical densities respectively. XRD, SEM, and EDX were performed for the structural and morphological analysis of the sintered samples. From TDS measurement, a similar trend of temperature-dependent hydrogen solubility was obtained for all samples compared to the tritium imaging plate (TIP) methods literature data of HT- and DTO-exposed samples. To compare the experimental results of the deuterium desorption profile derived by TDS analysis, the simulation code of the tritium migration analysis program, version 4 (TMAP4) was employed.

Thermodynamic and Kinetic Parameters of the Processes of Deuterium Interaction with Tungsten Protective Coatings

The effect of radiation damage on the retention of deuterium in tungsten (W) was examined. A vacuum-arc plasma source with magnetic stabilization of the cathode spot was used for tungsten coatings preparation. W samples were treated with D ions at temperatures 300‑600 K with a fluence of (1 – 10) ·1020 D2+/m2 and ion energies of 12 keV/D2+. The influence of radiation damage on microstructure and accumulation of deuterium implanted in W samples at room temperature and after annealing have been studied. Thermal desorption (TD) spectroscopy was used to determine the D retained throughout the bulk of the sample. The structure of TD spectra represents the multi-stage process of deuterium release suggesting the trapping of gas atoms by a number of defect types. Computational evaluation of deuterium desorption within the framework of the diffusion-trapping model allows to associate characteristics of experimental TD spectra with specific trapping sites in the material. Experimental TD spectrum was fitted by assigning four binding energies of 0.55 eV, 0.74 eV, 1.09 eV and 1.60 eV for the peaks with maxima at 475, 590, 810 and 1140 K, respectively. The low temperature peak in the TD spectra is associated with desorption of deuterium bounded to the low energy natural traps, whereas the other peaks are related to the desorption of deuterium bounded to the high energy ion induced traps: monovacancies and vacancy clusters.