Slow Positron Research Articles

Positron Annihilation Study of RPV Steels Radiation Loaded by Hydrogen Ion Implantation.

Specimens of 15Kh2MFAA steel used for reactor pressure vessels V-213 (VVER-440 reactor) were studied by positron annihilation techniques in terms of their radiation resistance and structural recovery after thermal treatment. The radiation load was simulated by experimental implantation of 500 keV H+ ions. The maximum radiation damage of 1 DPA was obtained across a region of 3 µm. Radiation-induced defects were investigated by coincidence Doppler broadening spectroscopy and positron lifetime spectroscopy using a conventional positron source as well as a slow positron beam. All techniques registered an accumulation of small open-volume defects (mostly mono- and di-vacancies) due to the irradiation, with an increase of the defect volume ΔVD ≈ 2.88 × 10−8 cm−3. Finally, the irradiated specimens were gradually annealed at temperatures from 200 to 550 °C and analyzed in detail. The best defect recovery was found at a temperature between 450 and 475 °C, but the final defect concentration of about ΔCD = 0.34 ppm was still higher than in the as-received specimens.

Defects Characterization of HgCdTe and CdZnTe Compounds by Positron Annihilation Spectroscopy

Infrared cooled photodetectors must operate at higher temperatures to reduce their size, weight and power consumption (SWaP context). Their stability and image quality are then challenged by extra electrical activity of crystal defects. Knowledge of defect populations is mandatory to improve the material quality of the epitaxial Hg1−xCdxTe (MCT) active layer and the Cd1−xZnxTe (CZT) substrate. Positron annihilation spectroscopy with a slow positron beam was used to study near-surface open-volume defects profiles. Low- and high-momentum fractions (\(S\),\( W\)) were used to characterize the Doppler broadening of the 511 keV electron-positron pair annihilation-line as a function of the positron implantation energy \(E\). The results show that three regions can be identified beneath the surface of the as-grown non-optimized MCT layer. The quasi-linear relationship between the annihilation characteristics in the regions suggests that the defect populations mainly correspond to the same open-volume defect in different concentrations. The probed defect is thought to be related to the mercury vacancy. This hypothesis is discussed in an original way with near-surface elemental profiles using scanning transmission electron spectroscopy combined to energy dispersive x-ray spectroscopy (STEM-EDX). Afterwards, this approach is extended to CZT substrates showing that surface and bulk properties of those fabricated by LYNRED tend to match those that are state-of-the-art. A common open-volume defect is probed, in concentration estimated by Hall effect around 1015 cm−3 and thought to be related to the cadmium vacancy.

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.

A new digital positron annihilation lifetime spectrometer for a single piece of micron-thickness film

Positron annihilation lifetime (PAL) spectroscopy is a unique method to study defects and supermicropores in solid materials. Traditionally, the pulsed slow positron beam (accelerator system included) was used to measure the PAL spectrum for a single film with a thickness of several microns, which is more complicated, expensive, and has worse time resolution than a conventional PAL spectrometer. In this paper, we developed a new PAL spectrometer to measure a single piece of micron-thickness film using two lanthanum bromide (LaBr3) detectors, a specially designed plastic scintillator detector, and a fast digitizer, at a cost equivalent to that of a conventional PAL spectrometer. The reliability and time resolution (around 210 ps, comparable to that of a conventional PAL spectrometer) of this spectrometer were verified by testing samples with thicknesses range from 15 to 60μm. Due to the successful construction of the new PAL spectrometer, PAL spectroscopy can now be applied to a single piece of micron-thickness film for the first time without building an accelerator system.

Helium behavior and vacancy‐defect evolution in nickel‐base alloy by helium ion beam irradiation and annealing

Nickel‐base alloys have been selected as a potential metallic material for reactor internals in Generation IV reactors. In order to evaluate their helium embrittlement resistance, microstrain changes and evolution of vacancy‐type defects after Helium irradiation and postimplantation annealing have been studied by grazing incidence X‐ray diffraction (GIXRD) and slow positron doppler broadening spectroscopy (PDB). GIXRD results show that the increase in microstrain after helium irradiation is more pronounced at high doses. The observed S parameters of PDB increase with the irradiation doses, which indicates a significant number of vacancy‐type defects, possibly helium‐vacancy clusters. For postimplantation annealing specimens, the microstrain characterized by GIXRD has recovered. The surprise is the S parameters that significantly increase, revealing that helium atoms trapped at unstable helium‐vacancy clusters desorb during annealing, contributing to the growth of helium bubbles. These findings of microstrain mechanisms and vacancy‐type defects behaviors give us new insights into the helium irradiation evaluation.

Improving the exploration of vacancy evolution in P92 alloy under Fe ion irradiation using positron annihilation

P92 alloy, a candidate structural material for supercritical water reactors, was irradiated with 1 MeV Fe ions at 1, 3, and 7 dpa at room temperature, 300, 450, and 550°C. Slow positron beam Doppler broadening spectroscopy was used to characterize the evolution of the open-volume defects. Irradiation of the Fe9Cr alloy at 300°C induced an unexcepted phenomenon in which the S parameter decreased with an increasing irradiation dose; the phenomenon was ascribed to the pinning effect of Cr on dislocation loops, which promoted the recovery of vacancies. Whereas the reduction in the S parameter was generally inhibited in the P92 alloy. These distinctions are related to the evolution of vacancies. We show that the migration of vacancies hindered by C atoms is mainly related to carbon–vacancy complexes in the P92 alloy at approximately 300°C. As the irradiation temperature increased, the complexes gradually dissociated, and the vacancies were captured and annihilated with interstitial atoms. A better understanding of the evolution of vacancies is helpful for investigating irradiation swelling.

On the helium bubble swelling in nano-oxide dispersion-strengthened steels

The development of structural materials resistant to harsh radiation environments requires an in-depth understanding of the early stage of the aging processes. In radiation environments with high transmutation helium production rates such as in fusion and spallation applications, even materials with otherwise acceptable radiation stability may suffer from radiation embrittlement related to helium bubble formation. While theoretical modeling of helium-assisted cavity nucleation in pure metals and simple alloys provides some useful guidelines at the atomic scale level, these, however, do not overlap with the size resolution of available experimental techniques. In this study, we employed slow positron beam spectroscopy to characterize the nucleation and growth of nano-scale helium bubbles in martensitic steels strengthened by thermodynamically stable nano-oxide dispersoids. In combination with transmission electron microscopy, we experimentally characterized the evolution of helium bubbles from small clusters of radiation-induced vacancies to large cavities well resolvable by TEM. Superior radiation resistance of oxide-dispersion strengthened steels dominates only in the early stages of bubble evolution, where positron lifetime measurements provide a missing piece of the microstructural puzzle conventionally constructed by TEM.

Micro-defects evolution of (Al0.33Cr0.21Fe0.28Zr0.18)O2 and (Al0.33Cr0.2Mn0.09Fe0.22Zr0.16)O2 induced by hydrogen ions irradiation

The micro-defects evolution of (Al 0 . 33 Cr 0 . 21 Fe 0 . 28 Zr 0.18 )O 2 and (Al 0 . 33 Cr 0 . 2 Mn 0 . 09 Fe 0 . 22 Zr 0.16 )O 2 thin films irradiated with low energy (60 eV) hydrogen ions (H + ) is investigated through Transmission Electron Microscopy (TEM) and the slow positron Doppler broadening spectroscopy (DBS) technique in this work. The results revealed that some perfect dislocation loops with Burgers vector b = a/2<1 1 0> were observed as the quaternary (Al 0 . 33 Cr 0 . 21 Fe 0 . 28 Zr 0.18 )O 2 irradiated with a fluence of 5.2 × 10 22 cm −2 . The micro defects are mainly vacancy (V), hydrogen vacancy complex (i.e. H–V complex), and vacancy dislocation loops. However, after the fluence increased to 1.2 × 10 23 cm −2 , the phase of (Al 0 . 33 Cr 0 . 21 Fe 0 . 28 Zr 0.18 )O 2 transformed from FCC structure to amorphous, suggesting that the weak ionic bonds between the cations with O. The defects mainly exist as large amounts of hydrogen bubbles, some H–V complex and few voids. As the addition of little Mn element, the phase of quinary (Al 0 . 33 Cr 0 . 2 Mn 0 . 09 Fe 0 . 22 Zr 0.16 )O 2 was unstable and easily produce precipitate under the irradiation temperature. And the micro-defects in (Al 0 . 33 Cr 0 . 2 Mn 0 . 09 Fe 0 . 22 Zr 0.16 )O 2 irradiated with 5.2 × 10 22 cm −2 mainly exist as V, H–V complex and some vacancy clusters. While the fluence increase to 1.2 × 10 23 cm −2 , the defects mainly exist as H–V complex and hydrogen bubbles. • The defects evolution of the two HEOs induced by H + irradiation behave differently. • The ionic bonds between the cations with O in (Al 0 . 33 Cr 0 .. 21 Fe 0 . 28 Zr 0.18 )O 2 are weak. • As the addition of Mn, the phase of (Al 0 . 33 Cr 0 . 2 Mn 0 . 09 Fe 0 . 22 Zr 0.16 )O 2 was unstable. • Hydrogen diffuse into both the surface and inner direction of films.

Characteristics of Solar Wind Radiation Damage in Lunar Soil: PAT and TEM Study

Irradiation structural damage (e.g., radiation tracks, amorphous layers, and vesicles) is widely observed in lunar soil grains. Previous experiments have revealed that irradiation damage is caused by the injection of solar wind and solar flare energetic particles. In this study, cordierite and gabbro were selected as analogs of shallow and deep excavated lunar crust materials for proton irradiation experiments. The fluence was 1.44 ± 0.03 × 1018 H+/cm2, which is equivalent to 102 years of average solar wind proton implantation on the Moon. Before and after irradiation, structural damage in samples is detected by slow positron annihilation technology (PAT), Doppler broadening (DB) measurement, focused ion beam (FIB), and transmission electron microscopy (TEM). The DB results showed the structural damage peaks of irradiated gabbro and cordierite were located at 40 and 45 nm. Hydrogen diffused to a deeper region and it reached beyond depths of 150 and 136 nm for gabbro and cordierite, respectively. Hydrogen atoms occupied the original vacancy defects and formed vacancy sites—hydrogen atom complexes, which affected the annihilation of positrons with electrons in the vacancy defects. All of the DB results were validated by TEM. This study proves that the positron annihilation technique has an excellent performance in the detection of defects in the whole structure of the sample. In combination with TEM and other detection methods, this technology could be used for the detection of structural damage in extraterrestrial samples.

Temperature dependence of positron annihilation lifetime in near-surface and bulk of room-temperature ionic liquid observed by a slow positron beam

We obtained temperature dependence up to 150 °C of the triplet positronium (ortho-Ps) lifetime in N,N,N-Trimethyl-N-propylammonium bis(trifluoromethanesulfonyl)imide (TMPA-TFSI) using the vertical slow positron beamline installed at AIST. The ortho-Ps lifetimes at the near-surface and bulk regions of TMPA-TFSI were measured. The lifetime difference between the near-surface and bulk at 150 °C, 130 °C above the melting temperature, suggested that the molecular oriented structure at the surface remained. The ortho-Ps lifetimes at the near-surface and bulk became shorter as the temperature increased. On the contrary, the ortho-Ps lifetimes became longer as the temperature increased when other molecular liquids were employed except for water.PACS/topics: 78.70.Bj.

Effect of neutron–photon converter materials (Cd, Gd, and Sm) on the positron production in a reactor-based slow positron beamline

The change in the amount of positron production when Cd cap, installed as a neutron–photon converter, is replaced with Gd or Sm caps was simulated by Monte Carlo calculations in the slow positron beamline at the Kyoto University Research Reactor, especially focusing on the change in the amount of positron production induced by neutrons emitted from a reactor core. Based on the simulation results, the amount of positron production induced by neutrons obtained using Gd and Sm caps was estimated to decrease to (69±4)% and (54±3)%, respectively, compared with the amount obtained using Cd cap. Meanwhile, Cd and Gd caps with a thickness of 1 mm were evaluated to have almost the same burn-up lifetime. Therefore, a Cd cap is the best choice, while a Gd cap, which has a higher melting point, could be an alternative if the structure of the positron source makes effective cooling difficult.

Defect evolution in Y&lt;sub&gt;0.5&lt;/sub&gt;Gd&lt;sub&gt;0.5&lt;/sub&gt;Ba&lt;sub&gt;2&lt;/sub&gt;Cu&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;7–&lt;i&gt;δ&lt;/i&gt;&lt;/sub&gt; superconducting layer irradiated by H&lt;sup&gt;+&lt;/sup&gt; ions

&lt;sec&gt;In order to further improve the superconducting current carrying capacity of RE-Ba-Cu-O coated conductor under the action of strong magnetic field, ion irradiation is used to generate the pinning centers of introduced magnetic flux in the RE-Ba-Cu-O coated conductor. In this work, the H&lt;sup&gt;+&lt;/sup&gt;-ion irradiation of second-generation high-temperature superconductor RE-Ba-Cu-O strip is carried out by using the 320 kV high charge state ion synthesis research platform. Doppler broadened slow positron beam analysis combined with Raman spectroscopy is used to measure the change of microstructure in Y&lt;sub&gt;0.5&lt;/sub&gt;Gd&lt;sub&gt;0.5&lt;/sub&gt;Ba&lt;sub&gt;2&lt;/sub&gt;Cu&lt;sub&gt;3&lt;/sub&gt;O&lt;sub&gt;7–&lt;i&gt;δ&lt;/i&gt; &lt;/sub&gt;(YBCO) sample irradiated by H&lt;sup&gt;+&lt;/sup&gt; ions in a range of 5.0 × 10&lt;sup&gt;14&lt;/sup&gt;–1.0 × 10&lt;sup&gt;16&lt;/sup&gt; ions/cm&lt;sup&gt;2&lt;/sup&gt;. The positron annihilation parameters in YBCO before and after irradiation are analyzed. It is found that after 100 keV H&lt;sup&gt;+&lt;/sup&gt; ion irradiation, a large number of defects including vacancies, vacancy groups or dislocation groups are produced in the superconducting layer.&lt;/sec&gt;&lt;sec&gt;The larger the irradiation dose, the more the produced vacancy type defects are and the more complex the defect types, and the annihilation mechanism of positrons in the defects changes. Raman spectroscopy results show that with the increase of H&lt;sup&gt;+&lt;/sup&gt; ion irradiation dose, the oxygen atoms in the coating rearrange, the plane spacing increases, the orthogonal phase structure of the coating is destroyed, and the degree of order decreases. The defects produced by such an ion irradiation lay a foundation for the introduction of flux pinning centers. Further research can be carried out in combination with X-ray diffractometer, transmission electron microscope, superconductivity and other testing methods to provide theoretical and practical reference for the optimization of material properties.&lt;/sec&gt;

Vacancy‐Type Defects in H+6%He Neutral Beam Irradiated WK Alloy Probed by Slow Positron Beam

H+6%He mixed neutral beam with a power density of 8 MV m−2 and fluence of 1025 m−2 is produced to induce irradiation damage at surface temperatures of 400, 800, and 1300 °C in WK alloy, and at 400 and 800 °C in pure W samples. Doppler‐broadening positron annihilation spectroscopy (DB‐PAS) and X‐ray diffraction (XRD) are used to probe the evolution of vacancy‐type defects in the samples after irradiation. The results show that for the WK alloy, the S‐parameters for the 400, 800, and 1300 °C samples increase sequentially because of the increase in vacancy‐type defect concentrations or volumes. The WK sample at 1300 °C exhibits a wider defect damage layer and more complicated vacancy‐type defects than those in the WK samples at 400 and 800 °C. For pure W, the S‐parameter of the 800 °C samples is larger than that of the 400 °C samples, which is attributed to the aggregation and growth of vacancy‐type defects. Based on a comparison of the WK and pure W samples, the pinning effect of K bubbles in the WK samples has an influence on the transportation of H/He atoms and the migration and aggregation of vacancy‐type defects.

Defect evolution in tungsten exposed to helium plasma and deuterium plasmas studied by slow positron beam

• W samples have been exposed to He plasma and D plasmas. • DBS-PA technique has been used to characterize the defects in W. • Low energy plasma exposure could create defects in W. • D plasmas exposure could reduce the detectable defects in He plasma exposed W. Comparison of defect formation in tungsten samples exposed only to a helium plasma and those exposed to both helium plasma and subsequent deuterium plasmas is performed via Doppler broadening spectroscopy in the positron annihilation technique (DBS-PA). The S parameters of tungsten samples after helium plasma exposure increased with the increase of the incident fluence, which indicates that low energy helium plasma could induce the formation of defects such as nano-sized helium bubbles and dislocations in tungsten. The S parameters of samples exposed to helium incident fluence of 7.9 × 10 21 He/m 2 enhanced after deuterium plasmas exposure, indicating that low energy deuterium plasmas could form defects in tungsten too. Unexpectedly, deuterium plasmas exposure did not significantly influence the S parameters of the tungsten sample with helium incident fluence of 3.9 × 10 22 He/m 2 , and reduced the S parameters of the tungsten sample with helium incident fluence of 7.9 × 10 22 He/m 2 . These variations of S parameters could be associated with the occupation of nano-sized helium bubbles by deuterium atoms. This indicates possible competition between the increased density of vacancy-type defects by deuterium plasmas exposure and the filling of nano-sized helium bubbles by deuterium atoms, reducing detectability of these defects.

Formation and time dynamics of hydrogen-induced vacancies in nickel

The formation of hydrogen-induced defects in nickel was investigated by positron annihilation lifetime spectroscopy (PALS) and the time dynamics of those defects during room temperature aging was tracked with an unprecedented time resolution of the order of minutes using an ultrahigh-flux slow positron beam. Those measurements showed the formation of a large number of atomic vacancies simply by hydrogen addition at room temperature. Low-temperature PALS measurements indicated that they were monovacancy-level defects and low-temperature coincidence Doppler broadening measurements proved that hydrogen was trapped and bound to those vacancies during the hydrogen charge. Room temperature aging, i.e. below the stage III temperature in Ni, and the concomitant hydrogen desorption induced the agglomeration of those monovacancies into large vacancy clusters which remained even after all the hydrogen had desorbed and hydrides had disappeared. These results constitute the first empirical evidence that vacancy-hydrogen complexes are induced in Ni only by hydrogen charging and demonstrate that hydrogen has a primary role in the formation and stabilization of vacancies even at room temperature.

Investigation of irradiation resistance characteristics of precipitation strengthened high-entropy alloy (CoCrFeNi)95Ti1Nb1Al3 using slow positron beam

A high-entropy alloy (HEA), (CoCrFeNi)95Ti1Nb1Al3, with a tensile strength approximately 60% higher than that of the equiatomic high-entropy alloy CoCrFeNi was developed. The increase in tensile strength results from the formation of Ni, Ti, Nb, and Al-rich precipitates, having a face-centered cubic (FCC) L12 type crystal structure, in the alloy during aging. To investigate the irradiation resistance of this alloy, it was irradiated up to 1.5×1019 ions/m2, corresponding to 1.65 displacements per atom (dpa) at the peak damage, at 300, 573, and 773 K using high-energy 2.5 MeV Fe ions. Applying a slow positron beam, the formation of defect clusters induced by ion irradiation and the thermal stability of defects formed at 300 K were investigated. Vacancy clusters formed after irradiation with 5.0×1018 ions/m2 at 300 K. Irradiation above this fluence at 300 K, and at the same fluence at 573 K did not significantly affect the formation of vacancy clusters. However, no vacancy clusters were formed after irradiation at 5.0×1018 ions/m2 at 773 K. The high-temperatures irradiation of this HEA hinders the formation of vacancy clusters. The irradiation resistance of the (CoCrFeNi)95Ti1Nb1Al3 HEA was excellent.

Optimization of a device for positron moderation based on a magnetic bottle

The design optimization of a magnetic bottle device for high-efficiency positron moderation is described herein. The interaction between positrons and matter, including positron tracking, was performed via GEANT and COMSOL simulation. Optimization was performed for a 10 kW power supply for the excitation of two magnetic coils and were established geometry sizes of the device, namely a chamber with a radius of 100 mm and a length of 300 mm. The irradiation of a Ti foil with a thickness of 1 ÷ 10 μm at the TR19 cyclotron for 8 h with a proton current of 10 μA can produce 48V with an activity of 6 ÷ 60 MBq. Given such a source of fast positrons for use in the optimized magnetic bottle device, a slow positron beam intensity of 2 ÷ 10×104 s−1 can be achieved.

Investigation on structural and optical properties of ZnSe thin films prepared by selenization

In this paper, ZnSe films were prepared on quartz substrates by selenizing as-sputtered zinc films at different temperatures for 6 h. The crystal structure, morphology, microscopic defects and optical properties of the ZnSe films were characterized by XRD, SEM, Raman spectroscopy, UV–visible spectrophotometer and slow positron beam Doppler broadening spectroscopy, respectively. The results showed that ZnSe thin films had the best structural and optical properties when the selenization temperature was 700 °C . All ZnSe thin films have a hexagonal wurtzite structure. The results of XRD、SEM and Raman spectra all showed that the crystallization and molar ratio of the films were significantly optimized with the increase of temperature. The transmission spectra of the films showed an obvious absorption edge of ZnSe and increased transmittance with the increase of temperature. The variation of defect concentration and types in the ZnSe thin films were released visually by slow positron beam Doppler broadening energy spectra.

Defects introduced by helium irradiation at different temperatures in W and W-5wt%Re alloy

W and W-5wt%Re alloy were irradiated by 50 keV helium ions at RT, 200 °C, 350 °C and 500 °C to investigate the influence of temperature on the microdefects and surface morphology in the sample. The microdefects in the subsurface region and the surface damage caused by irradiation were characterized by Doppler broadening spectroscopy (DBS) of slow positron beam, transmission electron microscope (TEM) and scanning electron microscopy (SEM), respectively. The results show that a large number of vacancy-type defects were produced after helium ions irradiation, especially at 500 °C, the vacancy-type defects of W alloy are higher than that of W-5wt%Re alloy, which indicated that Re restricted the behavior of vacancy-type defects in tungsten to some extent. The surface irradiation damage such as crystal gap enlargement, grain fell off and pores were observed at different irradiation temperatures. Compared with the coral-like structure observed in W, the circular objects and Hilly-gully structure were observed in W-5wt%Re alloy, and both of them increased and grew with the increase of irradiation temperature. It was speculated that the presence of Re led to the difference by analyzing the formation mechanism of the coral-like structure and the Hilly-gully structure.

Open Porosity and Pore Size Distribution of Mesoporous Silica Films Investigated by Positron Annihilation Lifetime Spectroscopy and Ellipsometric Porosimetry.

Tunable mesoporous silica films were prepared though a sol-gel process directed by the self-assembly of various triblock copolymers. Positron annihilation γ-ray energy spectroscopy and positron annihilation lifetime spectroscopy (PALS) based on intense pulsed slow positron beams as well as ellipsometric porosimetry (EP) combined with heptane adsorption were utilized to characterize the open porosity/interconnectivity and pore size distribution for the prepared films. The consistency between the open porosities was examined by the variations of orthopositronium (o-Ps) 3γ annihilation fractions and the total adsorbed volumes of heptane. The average pore sizes deduced by PALS from the longest-lived o-Ps lifetimes are in good agreement with those by EP on the basis of the Barrett–Joyner–Halenda model, as indicated by a well fitted line of slope k = 1. The results indicate that the EP combined with heptane adsorption is a useful method with high sensitivity for calibrating the mesopore size in highly interconnected mesoporous films, whereas PALS is a novel, complementary tool for characterizing both closed and open pores in them.