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Artificial sun

The term "artificial sun" is commonly used to describe various technologies that simulate or replicate aspects of the Sun, including experimental nuclear fusion reactors designed to mimic the Sun's thermonuclear fusion process, solar simulators for scientific and testing purposes, and artificial sunlight systems for health, therapeutic, and horticultural applications. In the context of nuclear fusion, an artificial sun typically refers to a tokamak or similar device that confines and heats plasma to extreme temperatures exceeding 100 million degrees Celsius, aiming to achieve controlled, sustainable fusion reactions for clean, abundant energy production with minimal long-lived radioactive waste. These fusion devices employ powerful magnetic fields to contain the superheated plasma, preventing contact with reactor walls, and are central to global efforts to develop fusion power as an alternative to fossil fuels and fission nuclear energy. Prominent artificial sun projects in fusion research include China's (EAST), operational since 2006 in , which achieved confinement at over 100 million degrees for 1,066 seconds as of 2025, surpassing its previous record of 403 seconds set in 2023 and advancing data on operational stability. Similarly, South Korea's (KSTAR) sustained at 100 million degrees for 48 seconds during experiments from December 2023 to February 2024, emphasizing high-performance shaping for future reactors. France's WEST established a record in February 2025 by maintaining above 50 million degrees for 1,337 seconds—approximately 25% longer than EAST's duration—utilizing advanced components to evaluate materials under extreme conditions. These national initiatives support the international project in , France, involving 35 countries to demonstrate net energy gain from by the 2030s, tackling challenges such as instability and heat exhaust.

Nuclear Fusion Devices

Concept and Principles

An is a controlled reactor engineered to replicate the thermonuclear process that powers , fusing light atomic nuclei such as isotopes into heavier elements like while releasing enormous . This concept aims to harness the same reaction that sustains stellar production on , providing a potential source of virtually unlimited, clean power. Unlike natural , which occurs under immense gravitational pressure, artificial suns require sophisticated human-engineered systems to achieve and maintain the necessary conditions for sustained reactions. The core principles revolve around the deuterium-tritium (D-T) fusion reaction, the most feasible for current technology, where a deuterium nucleus (^2H) and a tritium nucleus (^3H) fuse to produce a helium-4 nucleus (^4He), a neutron, and approximately 17.6 MeV of energy per reaction. To enable this, the fuel mixture is ionized into plasma—a hot, charged gas—and heated to temperatures exceeding 100 million degrees Celsius, far surpassing the Sun's core temperature of about 15 million degrees, to overcome the Coulomb barrier between positively charged nuclei. Plasma confinement is critical to prevent contact with reactor walls, which would cool the plasma and halt fusion; this is typically achieved through magnetic fields that suspend and stabilize the plasma. The Lawson criterion defines the ignition threshold for self-sustaining fusion, requiring the product of plasma density n (in particles per cubic meter) and energy confinement time \tau_E (in seconds) to exceed $10^{20} s/m³ for D-T reactions at relevant temperatures: n \tau_E > 10^{20} \, \mathrm{s/m^3} This ensures that fusion reaction rates outpace energy losses, leading to net power production. In contrast to , which splits heavy atoms like to release and generates long-lived along with proliferation risks, mimics stellar processes using abundant fuels— from and bred from —producing minimal short-lived radioactive byproducts and no gases, positioning it as a safer, more pathway. The historical roots trace to the early , when international research began exploring controlled through early magnetic confinement experiments, inspired by the Sun's mechanism. The phrase "artificial sun" gained traction in media around the to evoke the solar-like in tokamak-based efforts, symbolizing the quest for star-powered on .

Key Technologies

Magnetic confinement fusion (MCF) represents the primary approach for developing artificial sun devices, utilizing powerful magnetic fields to confine and control superheated at temperatures exceeding 100 million degrees , mimicking the sun's core conditions. In MCF systems, toroidal magnetic fields—generated by coils encircling a doughnut-shaped —create a helical path that prevents plasma particles from escaping toward the vessel walls, thereby sustaining reactions over extended periods. This method has dominated research since the mid-20th century due to its scalability and ability to achieve quasi-steady-state operations, as outlined in foundational reports from the (IAEA). The , the most widely studied MCF configuration, features a chamber where is confined by a combination of (circumferential) and poloidal (vertical) produced by external superconducting magnets and an induced current. Superconducting materials like niobium-tin alloys enable high-field strengths up to 13 , minimizing energy losses and supporting longer durations. The balance between pressure and magnetic confinement is governed by the magnetic pressure equation: \frac{B^2}{2\mu_0} where B is the magnetic field strength and \mu_0 is the permeability of free space, ensuring the plasma remains stable without direct contact with containment structures. This design has been refined through decades of international collaboration, with key principles detailed in the proceedings of the IAEA Fusion Energy Conferences. Alternative technologies include stellarators, which achieve steady-state plasma confinement using twisted, non-axisymmetric magnetic coils that eliminate the need for plasma current drive, potentially reducing instabilities compared to tokamaks. Stellarators offer advantages in continuous operation but face greater engineering complexity in coil fabrication. In contrast, inertial confinement fusion (ICF) employs high-powered lasers to compress and heat fuel pellets to fusion conditions in microseconds, providing a pulsed rather than continuous approach; while MCF focuses on sustained magnetic isolation, ICF relies on rapid implosion dynamics, as compared in reviews by the U.S. Department of Energy's fusion programs. Heating the plasma to ignition temperatures in these devices involves multiple complementary methods: neutral beam injection (NBI) accelerates neutral particles into the to transfer momentum and heat via collisions; radiofrequency (RF) heating uses electromagnetic waves at frequencies like 100-500 MHz to resonate with ions or electrons; and ohmic heating induces electrical currents within the itself for initial temperature ramps. These techniques, often combined, can deliver gigawatts of power to achieve the necessary thermal energy for deuterium-tritium fusion, with NBI and RF systems proven effective in achieving temperatures over 150 million in experimental setups. Significant challenges persist in these technologies, including plasma instabilities such as major disruptions—sudden losses of confinement that can damage vessel components—and the endurance of materials like tungsten under intense neutron bombardment from fusion reactions. Disruptions arise from magnetohydrodynamic (MHD) modes that destabilize the plasma equilibrium, necessitating advanced control systems like real-time feedback loops. First-wall materials must withstand fluxes exceeding 10 MW/m² and neutron doses up to 100 dpa (displacements per atom) over device lifetimes, driving research into divertors and advanced alloys. These hurdles are central to ongoing engineering efforts in MCF, as documented in high-impact studies from the Fusion Engineering and Design journal.

Major Fusion Projects

EAST Tokamak

The (EAST), developed by the Hefei Institutes of Physical Science under the , represents a key advancement in -based research, building on the magnetic confinement principle to achieve high-temperature s. Launched in 2006, EAST achieved its first plasma discharge that year, marking China's entry into large-scale superconducting experimentation. By the 2010s, the device transitioned to fully superconducting operations, incorporating niobium-titanium alloy coils for and poloidal fields, which enable extended pulse durations essential for steady-state studies. EAST features a compact with an overall of approximately 8 meters, a major plasma radius of 1.85 meters, and the capability to generate and confine at temperatures exceeding 100 million °C. Its all-superconducting magnet system, comprising 16 field coils, six poloidal field coils, and a central , supports high-current operations up to 1 megaampere while minimizing energy losses for long-pulse scenarios. These specifications allow EAST to simulate conditions relevant to future reactors, focusing on plasma heating, current drive, and wall-material interactions without relying on conventional magnets. Key milestones underscore EAST's progress in fusion confinement. In 2021, the device set a by sustaining a of 120 million °C for 101 seconds, demonstrating enhanced heating efficiency through neutral beam injection and radiofrequency systems. Building on this, in January 2025, EAST achieved a groundbreaking 1,066 seconds of steady-state high-confinement (H-mode) operation at over 100 million °C, surpassing previous duration records and validating long-pulse stability. In October 2025, researchers reported a major breakthrough in developing high-performance core materials, such as advanced alloys for -facing components, enabling next-generation subsystems resilient to extreme fluxes. EAST contributes significantly to international fusion efforts by testing ITER-relevant technologies, including divertor configurations and steady-state plasma scenarios that inform the multinational project's operational strategies. Its 2025 advancements in core materials have accelerated progress toward durable reactor components, supporting global goals for sustainable fusion power. As of November 2025, EAST remains active in experiments targeting even longer pulses beyond 1,000 seconds, bolstered by private sector investments in China's fusion ecosystem, including funding from Ant Group to fusion startups in Hefei that complement national research initiatives.

ITER Project

The International Thermonuclear Experimental Reactor () is a collaborative international project aimed at demonstrating the feasibility of as a large-scale, carbon-free source, initiated through the signing of the ITER Agreement in 2006 by seven member parties: , the , , , the Republic of Korea, , and the . Located at the site in , the project involves contributions from 35 nations and seeks to achieve first plasma in 2033, with initial deuterium-tritium operations targeted for 2035. This timeline reflects adjustments from earlier schedules due to technical and complexities, positioning as the world's largest experiment. ITER's design stands approximately 30 meters tall and is engineered to produce 500 megawatts of thermal from an input of 50 megawatts, utilizing a heated to 150 million degrees —ten times hotter than the Sun's core. The device confines this using a system of 10,000 tonnes of superconducting magnets, cooled to near-absolute zero, which generate magnetic fields up to 13 to maintain stability. These magnets, including 18 field coils, form a doughnut-shaped vacuum vessel that isolates the ultra-hot from the reactor walls, enabling sustained fusion reactions between and isotopes. Assembly of the commenced in 2020, with significant progress by 2025 including the installation of the first sector module in , followed by additional modules in and ongoing sector integrations. As of November 2025, the fifth of six central modules has been installed, advancing preparations for testing, while the nears completion despite supply chain delays that contributed to the first shift to 2033. These milestones underscore steady on-site construction, with the base and lower sections already in place to support the reactor's integration. Scientifically, ITER aims to achieve an energy gain factor Q greater than 10, meaning it will produce at least ten times more than the power required to heat and sustain the , demonstrating net in a controlled environment. The project will conduct pulses lasting 400 to 500 seconds at high performance, building toward longer durations, and test tritium breeding modules to validate self-sustaining fuel through lithium reactions within the blanket surrounding the . These goals will provide critical data for future fusion reactors, including optimization of confinement and exhaust management. Despite achievements, ITER faces substantial challenges, including budget overruns that have escalated the total cost beyond €20 billion from an initial €6 billion estimate, with an additional €5 billion attributed to and design refinements as of 2024 assessments carried into 2025. Progress on toroidal field coils continues in 2025, with cold testing facilities preparing for the first coil validations by late year, even amid geopolitical tensions affecting supply chains from members like . These hurdles highlight the complexities of multinational collaboration but affirm ITER's role as a foundational step toward .

Other Initiatives

In addition to major international collaborations, several national programs are advancing research toward practical energy production. South Korea's Korea Institute of Fusion Energy is planning K-DEMO, a demonstration reactor aimed at achieving steady-state operation and net electricity production after 2050, building on experience from the . In November 2025, the Korean government announced a competition among local governments to host a new "artificial sun" dedicated to fusion development, with site inspections underway to select a location for enhanced research infrastructure. France's WEST (Tungsten Environment in Steady-state Tokamak) tokamak, operated by the French Alternative Energies and Atomic Energy Commission (CEA), set a record in February 2025 by maintaining plasma above 50 million degrees Celsius for 1,337 seconds—over 22 minutes—using advanced tungsten components to test materials for extreme conditions in future reactors like ITER. In the United States, the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory achieved a historic inertial confinement fusion (ICF) ignition milestone in December 2022, producing 3.15 megajoules of fusion energy from 2.05 megajoules of laser input, marking the first controlled net energy gain in a laboratory setting. Ongoing upgrades to NIF's laser systems, including enhancements to the injection laser system and overall facility recapitalization estimated at $470 million to $1 billion, aim to increase shot rates and energy output for repeated high-yield experiments through 2025 and beyond. Private sector efforts complement these, with Commonwealth Fusion Systems advancing its SPARC tokamak, a compact high-field device that began assembly in March 2025 and targets initial demonstrations of net energy production (Q>1) by 2027, leveraging high-temperature superconducting magnets for improved efficiency. European initiatives beyond ITER include the (JET), which set a in 2021 by sustaining 59 megajoules of energy for five seconds in deuterium-tritium , providing critical data for design validation. The United Kingdom's (STEP) program, a public-private , is designing a plant targeting grid-connected operations by 2040, with £2.5 billion in government funding announced in June 2025 to support in Nottinghamshire. In Japan, the JT-60SA , a joint EU-Japan project, achieved first in October 2023 and entered operational phases for integrated commissioning, focusing on and control to inform operations. Private investments in have surged globally, reaching a cumulative $9.7 billion across approximately 50 projects by July 2025, with $2.64 billion raised in the prior 12 months alone, driven by advancements in and energy demands. In , Ant Group led a hundreds-of-millions-yuan round in November 2025 for startup Xeonova, contributing to the 14.7 billion yuan ($2 billion) raised by 12 domestic fusion firms by July 2025, emphasizing compact designs for commercialization. These efforts reflect a broader global trend toward compact, high-field magnet technologies, as seen in , to enable smaller, more cost-effective s compared to traditional large-scale tokamaks. Additionally, in October 2025, Governor signed a bill allocating $5 million in state funds to UC for developing diamond-based sensors to monitor extreme conditions in fusion devices, enhancing diagnostics for safer operations.

Solar Simulators

Design and Operation

Solar simulators are high-intensity light sources engineered to replicate the spectral distribution of sunlight, encompassing ultraviolet (UV), visible, and infrared (IR) wavelengths, for controlled testing environments. These devices achieve irradiance levels typically standardized at 1 kW/m² under air mass 1.5 global (AM1.5G) conditions, representing terrestrial solar radiation, though the solar constant (AM0) is approximately 1.367 kW/m² at the top of the atmosphere; advanced models can reach up to 10 kW/m² for concentrated solar applications. The core components of a solar simulator include the light source, optical system, and filtration elements. Traditional sources rely on arc lamps, which produce a broad closely matching due to their high-pressure plasma discharge, while modern alternatives use (LED) arrays for greater energy efficiency and longevity. Collimation is achieved through parabolic mirrors or fiber optic bundles to deliver parallel rays mimicking direct , and spectral filters ensure compliance with standards like ASTM E927, which classifies simulators based on spectral match, spatial non-uniformity, and temporal instability for AM1.5G replication. Operationally, solar simulators function in either continuous (steady-state) or pulsed modes to suit different testing durations and thermal requirements. Continuous modes provide stable illumination over extended periods, ideal for steady-state measurements, but necessitate robust cooling systems—such as water or air circulation—to manage heat from high-power lamps and prevent spectral drift. Pulsed modes deliver short bursts of light, reducing thermal load on samples and enabling high-speed testing, with pulse durations calibrated for uniformity. Calibration involves measuring irradiance across defined test areas, such as 2 m × 2 m fields, using multiple points to verify spatial uniformity within 2-5% as per ASTM E927 guidelines. The evolution of solar simulators traces back to the , when early designs employed carbon and vacuum tube-based lamps for and testing, evolving to short- lamps by the for improved . By the , LED arrays emerged as efficient alternatives, offering lower power consumption and reduced maintenance compared to lamps. As of 2025, advancements include tunable outputs via multi-wavelength LEDs, enabling precise adjustments for climate or simulations like AM0, enhancing versatility for research.

Scientific Applications

Solar simulators play a crucial role in space technology by replicating the intense solar radiation and conditions encountered in , enabling researchers to assess the performance and longevity of satellite components. For instance, facilities at NASA's utilize large-scale solar simulators to test spacecraft materials under simulated orbital exposure, including thermal and radiative stresses that mimic the sun's full spectrum. These tests are essential for validating designs before launch, as seen in evaluations of components for missions like the , where simulators help ensure structural integrity against prolonged solar bombardment. Additionally, (UV) degradation tests conducted with solar simulators accelerate the study of material breakdown, such as embrittlement or , providing data on how satellites withstand years of exposure in days or weeks. In photovoltaic research, solar simulators standardize testing conditions to measure solar cell efficiency by delivering a consistent air mass 1.5 global (AM1.5G) spectrum, which closely approximates terrestrial sunlight. This allows precise current-voltage (I-V) characterization, where cells are exposed to controlled irradiance levels to determine power conversion efficiency without outdoor variability. High-class simulators, certified under standards like IEC 60904-9, ensure spectral match within 2% deviation across key wavelengths, enabling reliable comparisons across device types. As of 2025, these tools have been instrumental in advancing perovskite solar cells, with updated testing protocols assessing stability and efficiency under simulated conditions; for example, evaluations have confirmed efficiencies exceeding 33% for tandem perovskite-silicon configurations through rigorous I-V sweeps and light-soaking experiments. Solar simulators facilitate investigations by accelerating processes, simulating decades of solar exposure to evaluate in paints, polymers, and other coatings. In these tests, xenon-based illumination replicates UV, visible, and components of , inducing photochemical reactions that reveal fading, cracking, or loss of in exterior materials. For automotive applications, simulators assess durability by exposing laminated windshields to intensified UV and thermal cycles, quantifying yellowing or risks under equivalent years of highway use. This controlled approach outperforms natural exposure, offering quantifiable metrics like gloss retention or tensile strength loss to guide formulation improvements. In , solar simulators enable controlled experiments on biological and ecological responses to solar radiation, isolating variables like intensity and spectrum. Researchers use them for plant growth trials, where artificial sunlight drives in growth chambers to model crop yields under varying climates, revealing how altered UV levels affect accumulation or uptake. These setups also support climate modeling by simulating on ecosystems, such as testing algal blooms or microbial activity in aquatic systems under enhanced solar conditions. Furthermore, they investigate biological effects on organisms, including DNA damage from UV exposure in skin cells or , providing insights into impacts without field uncertainties. Prominent facilities underscore the global infrastructure for these applications, including NASA's Plum Brook Station—now the Neil A. Armstrong Test Facility—which houses the Space Environments Complex with vacuum chambers integrated with powerful simulators for full-scale testing. Similarly, the European Space Agency's ESTEC Large Space Simulator in features a high-fidelity sun simulator with 19 modules delivering up to 2,300 W/m² over a 350 mm beam, used for thermal balance under simulated sunlight. In commercial contexts, simulators ensure certification per IEC 60904 standards, where modules undergo efficiency validation in production lines to meet spectral and uniformity requirements for market approval.

Artificial Sunlight Systems

Health and Therapeutic Uses

Artificial sunlight systems, particularly devices, are employed to mimic natural solar exposure for therapeutic purposes, addressing conditions linked to insufficient sunlight such as (SAD). These systems deliver bright white light at intensities of 10,000 for 30 minutes daily, typically upon waking, to alleviate depressive symptoms by suppressing and elevating serotonin levels, with the recommending this as a first-line treatment for milder SAD cases. Additionally, exposure to ultraviolet B (UVB) components in these systems promotes synthesis in the skin, increasing circulating 25-hydroxyvitamin D levels by up to 25% after eight weeks of controlled sessions, thereby mitigating deficiency-related health risks like weakened immunity and disorders. Light therapy also regulates circadian rhythms by advancing or delaying onset through timed exposure, improving sleep quality and daytime alertness in individuals with disrupted cycles, such as shift workers or those with . The core technology involves full-spectrum fluorescent or (LED) lamps that replicate daylight without excessive radiation, operating at color temperatures between 2,700 and 6,500 to evoke natural while minimizing UV overload that could lead to skin damage. These devices emit UV-free visible light for broad applications or controlled narrowband UVB (311-313 ) for targeted therapies, ensuring safe simulation of solar spectra. In medical contexts, narrowband UVB phototherapy treats by penetrating the skin to slow excessive cell growth and reduce , achieving 75% improvement in plaques after 20-36 sessions administered three times weekly, as per guidelines from the . A 2025 meta-analysis on for sleep disorders in shift workers demonstrated improvements in total time by an average of 32.54 minutes, primarily as an adjunct to established chronotherapies. Another 2025 study explored blue- LEDs (around 464 nm), finding they more strongly suppress secretion during evening exposure compared to red light, highlighting the need for appropriate timing—such as morning use—to advance circadian rhythms and support regulation without disruption. Common devices include stationary light boxes for SAD treatment and portable dawn simulators that gradually increase illumination from 0 to 300 lux over 30-60 minutes to mimic sunrise, aligning with guidelines for 30-60 minutes of daily exposure at eye level without direct staring. Many such devices, including home UVB units for , are FDA-cleared as Class medical devices, confirming safety and efficacy for over-the-counter or prescribed use. Potential risks necessitate safeguards, including protective eyewear to prevent retinal strain from prolonged bright light and strict dosage limits for UVB, such as starting at 70% of the minimal erythema dose (typically 200-500 mJ/cm² per session) with increments of 5-10% to avoid burns or long-term skin cancer risk. FDA-cleared devices incorporate timers and filters to enforce these standards, ensuring therapeutic benefits without exceeding safe exposure thresholds.

Horticultural Applications

Artificial sunlight systems, particularly LED grow lights, play a pivotal role in modern by replicating the (PAR) spectrum essential for plant growth. PAR encompasses wavelengths from 400 to 700 nm, where red (600–700 nm) and blue (400–500 nm) light are most efficiently absorbed by to drive , enabling (CEA) such as indoor farming. These systems allow for precise tuning of light spectra, optimizing energy use and compared to traditional broad-spectrum sources. In applications like vertical farms and greenhouses, artificial sunlight supports year-round production of crops including leafy greens, herbs, and cannabis in urban settings, reducing reliance on seasonal sunlight and land constraints. For instance, vertical farming integrates stacked layers with LED lighting to maximize space efficiency in cities, while cannabis cultivation benefits from tailored red-dominant spectra during flowering to enhance cannabinoid yields. Urban agriculture initiatives, such as those in controlled-environment facilities, leverage these systems to produce fresh produce locally, minimizing transportation emissions. By 2025, trends include AI-optimized light spectra that dynamically adjust wavelengths based on real-time plant sensors, boosting yields by up to 20–30% through predictive modeling of growth stages. Key benefits include substantial resource savings: these systems enable year-round cultivation independent of weather, with water use reduced by up to 95% through recirculating hydroponic or aeroponic setups, as demonstrated by ' vertical farms that mist roots efficiently. Energy efficiency is further improved by LEDs' low heat output, allowing denser planting and integration with climate controls for overall . Technical specifications typically involve light intensities of 200–1,000 µmol/m²/s photosynthetic photon flux density (PPFD), measured in the PAR range, to match varying crop needs—lower for seedlings and higher for fruiting stages. Photoperiod control, often 12–18 hours daily, simulates day-night cycles to regulate flowering, while integration with CO₂ enrichment (up to 1,000 ppm) amplifies under elevated light, increasing by 20–50%. Despite these advantages, challenges persist, primarily high energy costs that can account for 25–50% of operational expenses in fully artificial setups, limiting scalability in regions with expensive electricity. Advancements by 2025 address this through (QD) LEDs, which provide broader spectra mimicking full by down-converting to usable red and far-red wavelengths, enhancing and reducing power needs by 15–30% in integrations. These innovations, including QD films on covers, improve light capture for crops like , potentially increasing yields without proportional energy hikes.