Radiative Processes Research Articles

Direct Synthesis and Characterization of Hydrophilic Cu-Deficient Copper Indium Sulfide Quantum Dots.

Copper indium sulfide (CIS) nanocrystals constitute a promising alternative to cadmium- and lead-containing nanoparticles. We report a synthetic method that yields hydrophilic, core-only CIS quantum dots, exhibiting size-dependent, copper-deficient composition and optical properties that are suitable for direct coupling to biomolecules and nonradiative energy transfer applications. To assist such applications, we complemented previous studies covering the femtosecond-picosecond time scale with the investigation of slower radiative and nonradiative processes on the nanosecond time scale, using both time-resolved emission and transient absorption. As expected for core particles, relaxation occurs mainly nonradiatively, resulting in low, size-dependent photoluminescence quantum yield. The nonradiative relaxation from the first excited band is wavelength-dependent with lifetimes between 25 and 150 ns, reflecting the size distribution of the particles. Approximately constant lifetimes of around 65 ns were observed for nonradiative relaxation from the defect states at lower energies. The photoluminescence exhibited a large Stokes shift. The band gap emission decays on the order of 10 ns, while the defect emission is further red-shifted, and the lifetimes are on the order of 100 ns. Both sets of radiative lifetimes are wavelength-dependent, increasing toward longer wavelengths. Despite the low radiative quantum yield, the aqueous solubility and long lifetimes of the defect states are compatible with the proposed role of CIS quantum dots as excitation energy donors to biological molecules.

Quantifying the dynamical and radiative processes of the drastically weak South Asian summer monsoon circulation in 2015

The South Asian summer monsoon (SASM) circulation in 2015 is the weakest since 2000s, which results in severe drought over broad regions of the Indian peninsula. The 2015 SASM is closely related to the weakened summer meridional thermal contrast between southern Eurasia (SE) and the tropical Indian Ocean (TIO) at the mid–upper troposphere. Based on an updated climate feedback-response analysis method, this study conducts a quantitative attribution analysis of the thermal contrast anomalies associated with the 2015 SASM to multiple dynamical and radiative processes, particular for aerosol process. Result shows that the 2015 weak SASM is mainly attributed to the effect of water vapor (58%), followed by the effects of atmospheric dynamics (18%), clouds (15%), and aerosols (15%), respectively. These positive effects are partially offset by the negative contribution from surface dynamic process (-14%). As the most pronounced factor, the water vapor process weakens the SASM circulation via inducing SE cooling and TIO warming, which is closely linked to the decreased (increased) specific humidity over SE (TIO). Further analysis indicates that the total effect of aerosols is dominated by the changes in black carbon and sea salt. As two important components, the SE cooling and TIO warming separately account for about 51% and 49% to the 2015 SASM. The former is mainly attributed to the cooling effect of clouds, while the latter is mainly induced by the warming effect of atmospheric dynamics. Our result provides a new insight into the 2015 weak SASM from a quantitative perspective.

2D‐Material‐Fused High‐Emittance Plasmo–Photonic Metasurfaces

AbstractTransition metal dichalcogenides (TMDC) are a family of atomic‐layer 2D materials (2dMs). Many researches have attempted to reinforce the unique properties by incorporating artificially designed nanostructures. Here, a highly photoluminescence (PL) enhancing platform is reported that is formed by combining high‐emittance plasmo–photonic metasurfaces with a large‐area 2dM, which is a continuous monolayer of TMDC of cm2 dimension. It is experimentally demonstrated that the 2dM‐PL intensity at room temperature is enhanced by more than 1030‐fold in comparison with that observed on the flat gold film regions. The enhancement is associated with spectral transformation indicating a resonant effect of the metasurfaces. It is moreover revealed that the confocal PL image originates from a coherent single‐mode emission that forms a photon number distribution obeying the Poisson probability distribution. Thus, the 2dM‐fused metasurfaces function as efficient coherent quantum light sources. PL decay‐time analysis also reveals the coexistence of two components in the enhanced PL. The fast component exhibits a lifetime of 18 ps whereas the slow component decays at 4.4 ns. Both components are most likely to undergo radiative processes, which indicates that metal‐induced PL quenching is suppressed on these 2dM‐fused metasurfaces. The long lifetime component is ascribed to an excitonic intervalley transition.

Radiation Process in Relativistic MHD Waves: The Case of Circularly Polarized Alfvén Waves

Turbulence in highly magnetized plasma can be relativistic and induce an electric field comparable to the background magnetic field. Such a strong electric field can affect the emission process of nonthermal electrons. As the first step toward elucidating the emission process in relativistic turbulence, we study the radiation process of electrons in relativistic circularly polarized Alfvén waves. While the induced electric field boosts the average energy of low-energy electrons with a Larmor radius smaller than the wavelength, the emissivity for such electrons is suppressed because of the elongated gyromotion trajectory. The trajectory of high-energy electrons is shaken by the small-scale electric field, which enhances the emissivity. Since the effective Lorentz factor of E × B drift is ≃2 in the circularly polarized Alfvén waves, the deviation from the standard synchrotron emission is not so prominent. However, a power-law energy injection in the waves can produce a concave photon spectrum, which is similar to the GeV extra component seen in GRB spectra. If the turbulence electric field is responsible for the GeV extra component in GRBs, the estimates of the typical electron energy and magnetic field should be largely altered.

A Missing Piece of the E‐Region Puzzle: High‐Resolution Photoionization Cross Sections and Solar Irradiances in Models

AbstractMost ionospheric models cannot sufficiently reproduce the observed electron density profiles in the E‐region ionosphere, since they usually underestimate electron densities and do not match the profile shape. Mitigation of these issues is often addressed by increasing the solar soft X‐ray flux which is ineffective for resolving data‐model discrepancies. We show that low‐resolution cross sections and solar spectral irradiances fail to preserve structure within the data, which considerably impacts radiative processes in the E‐region, and are largely responsible for the discrepancies between observations and simulations. To resolve data‐model inconsistencies, we utilize new high‐resolution (0.001 nm) atomic oxygen (O) and molecular nitrogen (N2) cross sections and solar spectral irradiances, which contain autoionization and narrow rotational lines that allow solar photons to reach lower altitudes and increase the photoelectron flux. This work improves upon Meier et al. (2007, https://doi.org/10.1029/2006gl028484) by additionally incorporating high‐resolution N2 photoionization and photoabsorption cross sections in model calculations. Model results with the new inputs show increased O+ production rates of over 500%, larger than those of Meier et al. (2007, https://doi.org/10.1029/2006gl028484) and total ion production rates of over 125%, while production rates decrease by ∼15% in the E‐region in comparison to the results obtained using the cross section compilation from Conway (1988, https://apps.dtic.mil/sti/pdfs/ADA193866.pdf). Low‐resolution molecular oxygen (O2) cross sections from the Conway compilation are utilized for all input cases and indicate that is a dominant contributor to the total ion production rate in the E‐region. Specifically, the photoionization contributed from longer wavelengths is a main contributor at ∼120 km.

Effect of electron beam irradiation on hole structure of cellulose acetate membrane

Cellulose acetate (CA) is one of the most popular biomaterials used for filtration membranes in water treatment.In this study, the CA membranes immersing in water were irradiated by electron beam, and the hole structure of CA membranes at different irradiation doses was investigated. The SEM pictures show the combination of micro-meter sized pores in CA membrane during the irradiation process. The electrochemical impedance spectroscopy(EIS) results reveal the membrane resistance decreases with the irradiation dose, which implies easier ion permeation. The positron annihilation lifetime measurement (PAL) results indicate the mean free-volume hole size becomes smaller with increasing irradiation dose. The above results demonstrate that electron beam irradiation would lead to chain scission of CA, and then the formation of new pores and pores combination, which provides more channels for ion permeation. FTIR results suggest stronger hydrogen bonding in CA after the irradiation in water. The differential scanning calorimetry (DSC)results indicate that the crystallinity has been enhanced with the irradiation dose up to 10 kGy and reduces in the range from 10 kGy to 80 kGy. The results could provide the clues explaining the performance deterioration of CA membrane during treating radioactive waste water.

Radio emission as a stellar activity indicator

Radio observations of stars trace the plasma conditions and magnetic field properties of stellar magnetospheres and coronae. Depending on the plasma conditions at the emitter site, radio emission in the metre- and decimetre-wave bands is generated via different mechanisms, such as gyrosynchrotron, electron cyclotron maser instability, and plasma radiation processes. The ongoing LOFAR Two-metre Sky Survey (LoTSS) and VLA Sky Survey (VLASS) are currently the most sensitive wide-field radio sky surveys ever conducted. Because these surveys are untargeted, they provide an opportunity to study the statistical properties of the radio-emitting stellar population in an unbiased manner. Here we perform an untargeted search for stellar radio sources down to sub-mJy level using these radio surveys. We find that the population of radio-emitting stellar systems is mainly composed of two distinct categories: chromospherically active stellar (CAS) systems and M dwarfs. We also seek to identify signatures of a gradual transition within the M-dwarf population, from chromospheric or coronal acceleration close to the stellar surface similar to that observed on the Sun to magnetospheric acceleration occurring far from the stellar surface similar to that observed on Jupiter. We determine that radio detectability evolves with spectral type, and we identify a transition in radio detectability around spectral type M4, where stars become fully convective. Furthermore, we compare the radio detectability versus spectra type with X-ray and optical flare (observed by TESS) incidence statistics. We find that the radio efficiency of X-ray and optical flares, which is the fraction of flare energy channelled into radio-emitting charges, increases with spectral type. These results motivate us to conjecture that the emergence of large-scale magnetic fields in CAS systems and later M dwarfs leads to an increase in radio efficiency.

The impact of stratospheric aerosol heating on the frozen hydrometeor transport pathways in the tropical tropopause layer

The exceptionally low temperature in the tropical tropopause layer (TTL) restricts the amount of water vapor entering the stratosphere. However, moisture may also enter the stratosphere in its frozen state, and the amount thereof depends on hydrometeor sedimentation and air vertical velocity. We investigate the sensitivity of frozen hydrometeor transport pathways to substantial perturbations of the TTL temperature structure in global storm-resolving model simulations. A special focus is laid on the question which process—convection, slow upwelling within the background velocity field, in-cloud radiative processes, gravity waves or turbulence—is responsible for most of the transport. The study shows that the main contribution to the frozen hydrometeor flux is cold-point overshooting convection in both the control and perturbed scenario. The average convective event transports an increased amount of frozen hydrometeors at the cold-point tropopause, when the later is warmed. This finding can be explained by scaling of frozen moisture content with Clausius Clapeyron in a saturated environment.

Electrizaton and cathodoluminescence of single crystal MgO under 2.5 – 15 keV electron beam

Kinetics of single crystal MgO electrization showed a delay in the surface potential establishment. A number of processes taking place in the surface electrization and, in their turn, influenced by it, are discussed: secondary electron emission, accumulated charge distribution and spreading in the sample, modification of defects in the sample by the electron beam. The evolution of cathodoluminescence spectra was recorded during the irradiation process, showing both increases and decreases in intensity. A synergetic effect was suggested to explain the subthreshold generation of defects by the electron beam.

Radiative and Nonradiative Recombination Processes in AlGaN Quantum Wells on Epitaxially Laterally Overgrown AlN/Sapphire from 10 to 500 K

Radiative and nonradiative recombination processes are investigated in the temperature range from 10 to 500 K for AlGaN quantum wells on epitaxially laterally overgrown AlN/sapphire templates. Time‐integrated photoluminescence (PL) spectroscopy under selective excitation conditions demonstrates that the decrease in the radiative recombination efficiency with increasing temperature is one of the causes of the thermal droop in AlGaN‐based deep‐ultraviolet (DUV) light‐emitting diodes. Time‐resolved PL spectroscopy indicates that not only the decreasing nonradiative recombination lifetime but increasing radiative recombination lifetime with increasing temperature contributes to the thermal droop. The temperature dependence of the radiative recombination lifetime is discussed, revealing that luminescence linewidth is a valuable criterion for designing efficient AlGaN‐based DUV emitters.

Monitoring of changes in the concentration of volatile organic compound in beef irradiated with accelerated electrons

The need to develop safe methods for radiation processing of food products to improve their quality and extend their shelf life stimulates new scientific research aimed at increasing their effectiveness. Oxidation of lipids and proteins occurred under the impact of ionizing radiation in products with a high fat and water content, such as chilled meat and fish products, leads to the formation of volatile organic compounds in the product thus giving it a specific smell and taste. During storage, biochemical processes associated with microbial enzymatic activity and auto-oxidation develop in processed refrigerated products. These processes also modify the volatile organic compounds, which affect the organoleptic properties of the product. The method of gas chromatography-mass spectrometry was used to study the behavior of volatile compounds identified in irradiated beef samples both immediately after irradiation and four days later to determine the effective dose range for the radiation processing of beef. Monitoring of the content of volatile compounds in beef samples irradiated by 1-MeV electrons within a dose range from 0.25 to 5 kGy showed that the content of certain alcohols, aldehydes, and alkanes exhibited pronounced dose- and time-dependent character. The developed mathematical model describes the dependence of the concentration of volatile compounds identified immediately after irradiation in beef samples on the irradiation dose. The model is based on the simultaneous occurrence of two competing processes: the decomposition of compounds due to their oxidation and accumulation due to oxidation of other compounds after exposure to ionizing radiation. The results obtained revealed that the effective dosage range of radiation treatment lies between 250 and 1000 Gy.

Highly electrochemically active Ti3C2Tx MXene/MWCNT nanocomposite for the simultaneous sensing of paracetamol, theophylline, and caffeine in human blood samples.

Thefacile fabrication is reportedof highly electrochemically active Ti3C2Tx MXene/MWCNT (3D/1D)-modified screen-printed carbon electrode (SPE) for the efficient simultaneous electrochemical detection of paracetamol, theophylline, and caffeine in human blood samples. 3D/1D Ti3C2Tx MXene/MWCNT nanocomposite was synthesized using microwave irradiation and ultrasonication processes. Then, the Ti3C2Tx/MWCNT-modified SPE electrode was fabricated and thoroughly characterized towards its physicochemical and electrochemical properties using XPS, TEM, FESEM, XRD, electrochemical impedance spectroscopy, cyclic voltammetry, and differential pulse voltammetry techniques. As-constructed Ti3C2Tx-MWCNT/SPE offers excellent electrochemical sensing performance with good detection limits (0.23, 0.57, and 0.43µM) and wide linear ranges (1.0 ~ 90.1, 2.0 ~ 62.0, and 2.0-90.9µM) for paracetamol, caffeine, and theophylline, respectively, in the human samples. Notably, the non-enzymatic electroactive nanocomposite-modified electrode has depicted a semicircle Nyquist plot with low charge transfer resistance (Rct∼95 Ω), leading to high ionic diffusion and facilitating an excellent electron transfer path. All the above results in efficient stability, reproducibility, repeatability, and sensitivity compared with other reported works, and thus, it claims its practical utilization in realistic clinical applications.

Multi-scale remote sensing retrieval model for land surface emissivity and its impact on land surface temperature estimation

ABSTRACT As a fundamental parameter of the surface radiation process, land surface emissivity (LSE) is the most direct factor affecting the land surface temperature (LST) retrieval accuracy. Based on the measured data from 2017 to 2023, the characteristics of LSE changes were analysed, different timescale LSE retrieval models were developed, and the impact of LSE on pixel scale observational LST acquisition was evaluated by using unmanned aerial vehicle (UAV) remote sensing images. The results show that with changes in atmospheric environmental conditions, the LSE changes are relatively less pronounced at 3.99 µm and 4.02 µm in the mid-infrared band and at 10.8 µm and 11.8 µm in the thermal infrared band than in the other bands. At the timescale above day, the LSE is significant correlation with the normalized differential vegetation index (NDVI). Vegetation is the main parameter that dominates the LSE change under heterogeneous underlying surfaces. On a daily timescale, LSE exhibits typical diurnal variation characteristics, and the amplitude of diurnal variation is influenced mainly by shallow soil water and heat conditions. The developed LSE model based on Fengyun-4A (FY-4A) satellite remote-sensing data can effectively reproduce the daily variation characteristics of LST and avoid the ‘jumping’ phenomenon that may occur in the NDVI threshold method. The root-mean-square error (RMSE) between the retrieved LST and in situ data is reduced to 3.78°C, and the retrieval accuracy is better than that of the published LST product. When using UAVs to obtain pixel-scale LSTs, dry bare soil is more sensitive to LSE. When the LSE increases from 0.95 to 1.0, the average LST obtained by the UAV deviates by approximately 1.0°C. This study preliminarily provides some spatiotemporal variation patterns of LSE and lays a foundation for the later-modified LST retrieval algorithms.

Deciphering between enhanced light emission and absorption in multi-mode porphyrin cavity polariton samples

Abstract It remains unclear how the collective strong coupling of cavity-confined photons to the electronic transitions of molecular chromophore leverages the distinct properties of the polaritonic constituents for future technologies. In this study, we design, fabricate, and characterize multiple types of Fabry-Pérot (FP) mirco-resonators containing copper(II) tetraphenyl porphyrin (CuTPP) to show how cavity polariton formation affects radiative relaxation processes in the presence of substantial non-Condon vibronic coupling between two of this molecule’s excited electronic states. Unlike the prototypical enhancement of Q state radiative relaxation of CuTPP in a FP resonator incapable of forming polaritons, we find the light emission processes in multimode cavity polariton samples become enhanced for cavity-exciton energy differences near those of vibrations known to mediate non-Condon vibronic coupling. We propose the value of this detuning is consistent with radiative relaxation of Herzberg-Teller polaritons into collective molecular states coupled to the cavity photon coherently. We contrast the feature stemming from light emission from the HT polariton state with those that occur due to polariton-enhanced light absorption. Our results demonstrate the landscape of molecular and photonic interactions enabled by cavity polariton formation using complex chromophores and how researchers can design resonators to leverage these interactions to characterize and control polaritonic properties.

AN IMPROVEMENT OF ARJUNA 1.0 CONVEYOR SYSTEM FOR 3D IRRADIATION

An improved design of the conveyor system of Arjuna 1.0 electron accelerator for 3D object irradiation has been done. The penetration of low energy electrons is less than 1 cm in the surface, causing a challenge for the irradiation process for sterilization of 3D objects. We design a conveyor that can be rotated 360o to irradiate objects evenly. The dimension of this conveyor is 1750 x 600 x 800 mm and the maximum diameter of the object is 7 cm. Based on the Frame Bending Stress analysis to calculate the strength of the conveyor frame, it is shown that the maximum displacement is only 0.029 mm, which is very small so it will cause no disturbance to power transfer from the motor to the conveyor. The normal stress (Smax) is 3.926 MPa and the bending stress for Smax (Mx) and Smax (My), are 2.391 MPa and 3.925 MPa respectively. We also calculate the stress analysis of the 3 mm-thickness of the motor mount and found that the Von-Misses Stress, first, and third Principal Stress are 4.425 MPa, 5.01 MPa, and 1.95 MPa respectively. These results confirm that the design and the material used for the conveyor are safe because the stress is very low than the material’s yield strength which is 207 MPa. The power needed for this conveyor is 0.01724 kW, with a maximum speed is 880 rpm. The new model of 3D conveyor has been constructed and can be implemented to ARJUNA 1.0 to irradiate objects on all its surfaces

Gamma irradiation effects on microbial and qualitative properties of rosehip (Rosa canina L.) fresh fruit during storage

AbstractFruit of rosehip (Rosa canina L.) has high economic, medicinal, and nutritional values. Rosehip is rarely consumed fresh due to limitations of seasonality and short shelf life. They are usually processed, which affects the nutritional and sensory characteristics of rosehip products. Radiation processing along with storage at 4 °C is a way to increase safety and prolong fresh rosehip durability. Rosehip fruits were harvested at enough maturity stage, irradiated at doses of 0 (control), 0.5, 1, and 1.5 kGy, and stored at 25 and 4 °C for 60 days. Gamma irradiation at 1 kGy caused an increase in weight loss during storage for 60 days at 25 °C. Microbial counts, total phenolic contents (TPC), total anthocyanin contents (TAC), ascorbic acid contents (AAC), DPPH• scavenging activity, total colour difference (∆Eh), and sensory properties were acceptable in the sample irradiated at 1 kGy and preserved for 60 days at 4 °C. The amounts of acidity, pH, and total soluble solids (TSS) were not significantly different from the control. Gamma irradiation at 1 kGy and thereafter storage of the irradiated fruit at 4 °C are suggested as minimal processing and storage conditions of rosehip fresh fruit (RFF) for 60 days.

Accelerating atmospheric physics parameterizations using graphics processing units

As part of a project aimed at exploring the use of next-generation high-performance computing technologies for numerical weather prediction, we have ported two physics modules from the Common Community Physics Package (CCPP) to Graphics Processing Unit (GPU) and obtained accelerations of up to 10× relative to a comparable multi-core CPU. The physics parameterizations accelerated in this work are the aerosol-aware Thompson microphysics (TH) scheme and the Grell–Freitas (GF) cumulus convection scheme. Microphysics schemes are among the most time-consuming physics parameterizations, second to only radiative process schemes, and our results show better acceleration for the TH scheme than the GF scheme. Multi-GPU implementations of the schemes show acceptable weak scaling in a single node with 8 GPUs, and perfect weak scaling on multiple nodes using one GPU per node. The lack of inter-node communication for column physics parameterizations contributes to their scalability, however, physics parameterizations are run along with dynamics, so the overall multi-GPU performance is often governed by the latter. In the context of optimizing CCPP physics modules, our observations underscore that the extensive use of automatic arrays within inner subroutines hampers GPU performance due to serialized memory allocations. We have used the OpenACC directive programming language for this work because it allows for easy porting of large amounts of code and makes code maintenance more manageable compared to low-level languages like CUDA and OpenCL.

OPTIMIZATION OF CONDITIONS FOR OBTAINING URTICA DIOICA L. EXTRACT AND THE STUDY OF ITS ANTIOXIDANT PROPERTIES

The purpose of the presented study was to select optimal conditions and develop a technology for obtaining nettle extract, which in the future can be used in food technologies. Nettles were harvested in May before the appearance of inflorescences. The place where the plant is collected is a forest near the village of Lvovka in the Shigonsky district of the Samara region. Mathematical optimization of the conditions for obtaining water-alcohol extract of nettle dioecious was carried out. Nettle extraction was carried out in the traditional way, with ultrasound treatment and ultrahigh frequency currents. To obtain an extract with the highest yield of extractives, it is recommended to use 75% ethyl alcohol as an extractant at a hydromodule of 1 : 10, a temperature in the range from 45 to 55 °C, and an extraction time of 2 hours. In addition, it is possible to use ultrasonic radiation or microwave processing to obtain the extract, which also contribute to an increase in the yield of dry substances. Nettle extract, prepared with the help of ultrahigh frequency currents, showed the greatest antioxidant activity. This extract contains 1309.9 mg of gallic acid and 322.9 mg of catechin per 100 g of feedstock, and its antioxidant activity is 2.5 mg/ml. At the same time, with the help of a microwave field, the extract can be obtained in a minimum time.

Fabrication of jelly like material from rLLDPE by a binary approach based on gamma irradiation and thermal processing for oil remediation

This study investigated the fabrication of a jelly-like material from recycled linear low-density polyethylene (rLLDPE) using gamma irradiation and thermal processing with silicone oil. rLLDPE was irradiated at 0, 50, 75, and 100 kGy before pyrolysis in silicone oil at 300 ℃ for 1 h to produce the jelly-like material (Ir-jLLDPE). Fourier transform infrared spectroscopy confirmed interactions between rLLDPE and silicone oil in Ir-jLLDPE. Scanning electron microscopy revealed a rough, porous surface morphology with internal fibrillar structures. Thermogravimetric analysis showed thermal decomposition stages related to structural changes from irradiation and silicone oil integration. Batch adsorption experiments demonstrated the exceptional absorption capacities of Ir-jLLDPE for various organic solvents (0.1–24.7 g/g) and oils (0.6–19.8 g/g). Kinetic studies revealed absorption followed pseudo-first order at 50 and 75 kGy doses and pseudo-second order at 0 and 100 kGy doses. Isotherm modeling indicated the Freundlich model better described adsorption behavior. Over 10 adsorption cycles, Ir-jLLDPE exhibited excellent stability for pump oil at 50 and 75 kGy. This research highlights the promise of gamma-irradiated, thermally processed rLLDPE materials for applications in oil spill remediation, organic contaminant removal, and environmental sustainability. The novel approach of combining radiation and thermal processing can upcycle problematic rLLDPE plastic waste into an absorbent jelly material with potential environmental remediation applications.

Effect of exposure of metakaolin‐based geopolymer cements to gamma radiation

AbstractThe stability of cementitious materials under the harsh environment they will experience when used for radioactive waste disposal is incredibly important. Therefore, understanding the irradiation resistance of geopolymer cement, a potential alternative binder for the treatment of nuclear waste, is of the utmost importance when trying to develop a safety case for these materials. The study presented here addresses the structural and chemical changes of metakaolin‐based geopolymers, designed with different water contents, and exposed to a total cumulative dose of 1 MGy of gamma radiation. The range of formulations that were tested showed a significant loss of free water related to the irradiation process, which has led to an increase in the porosity. Analysis of the chemical structure has shown minimal changes in the main binding type‐gel phase, demonstrating high microstructural stability. Results showed that in samples cured for longer than 20 h, the bound/gel structure water remained in the sample when the water content was kept low enough. As the porosity and water content increase, more gel water is removed due to radiation exposure. However, the degree to which the water is removed from the gel structure is very small, and minimal changes can be seen across the geopolymers tested. Overall, metakaolin‐based geopolymers appear resistant to irradiation up to 1 MGy, which offers a potentially viable alternative for the immobilization of problematic intermediate‐level waste.