A new study detailing the use of X-ray lasers to study Warm Dense Matter (WDM) has many in the sector excited. The researchers utilized the European XFEL to conduct a series of experiments surrounding the mysterious state of matter. Here’s what they discovered.
Warm Dense Matter (WDM) State
The term “Warm Dense Matter” describes a particular set of matter that doesn’t fall directly into current physics categories. Warm dense matter is seen by many as a crucial building block in the universe and understanding it would enable a deeper insight into the history of existence. Notably, the existence of this material state was only acknowledged two decades ago.
Warm Dense Matter is abundant in the universe. This unique state can be found on gaseous planets like Jupiter and even in the center of brown dwarf stars. The unique thing about WDM is it’s a state between plasma and a condensed stage. As such, it’s extremely difficult to recreate and plays a vital role in astrophysics, planetary science, and nuclear fission.
The initial understanding of WDM was broad. It grouped multiple phenomena that had ranging temperatures between a few thousand degrees and high density. Over the last 5 years, the definition has been expanded to include celestial bodies with a density between 0.01 and 100 g/cm³ and a temperature surpassing several thousand kelvins (1-100 eV).
Current Methods of Monitoring and Creating WDM
Optical equipment has been used to observe the warm dense matter state in the past. However, this approach was limited by the equipment’s capabilities. Specifically, the device could not register and accurately monitor the energy levels at peak.
Another method that is used currently is X-ray emission spectroscopy. This approach was invented 12 years ago as an electron-free alternative. In this study, researchers employ X-ray free-electron Lasers (XFELs) to generate high-intensity X-ray pulses lasting a single femtosecond. Notably, a femtosecond laser sends pulses that span millionths of a billionth of a second.
The introduction of reliable XFEL lasers enabled researchers to further their studies into the WDM state. Specifically, they examined the transient change and optical properties of matter exposed to laser X-ray irradiation. These studies have opened the door for new types of X-ray-free-electron lasers. For this study, researchers leveraged the ability to measure changes in atomic length scales to accurately document the conversion of solid matter into WDM state using the European XFEL in Hamburg.
European XFEL Laser
The European XFEL Laser is one of only a dozen XFELs in operation globally. This advanced device was constructed in collaboration with the DESY research center. It features a 2.1-mile-long testing area that enables researchers to monitor the electronic and ionic structure of matter as it converts.
Warm Dense Matter Study
To date, there haven’t been many studies conducted into how these new systems’ irradiation can alter matter states in a recordable and trackable manner. As such, the researchers sought to detail how the use of ultrafast X-ray free-electron laser pulses can convert copper into warm dense matter. Specifically, the team details the use of L-edge X-ray absorption spectroscopy over a large irradiation intensity range to convert states.
Warm Dense Matter Test
The laser pulses were set up to pulse blast illuminated copper samples for 15 femtoseconds. The researchers repeated this process at different intensities to see the effect and how each adjustment alerted the matter conversion rate. They noticed the X-ray laser pulse created strong ionization.
This ionization resulted in electrons expanding the matter as temperatures rose. Within seconds, the matter was converted into ionized WDM. From there, it became transparent to X-rays. This transition from saturable absorption (SA) to reverse saturable absorption (RSA) piqued researchers’ interest.
Mixing Experimental Data with Simulations
The testing process was performed using the Spectroscopy and Coherent Scattering (SCS) instrument of the European XFEL (EuXFEL). This location provided the perfect spot for researchers to conduct experiments and meticulously record the results. They examined precisely how much radiation passed through the matter as well as its ionization changes.
Source – Nature
Notably, the experiments required the XFEL pulse energy to be focused through Kirkpatrick–Báez mirrors. This approach enabled the team to set the beam size to 4 μm full-width at half-maximum (FWHM). A pulse energy of 2 mJ was measured with two X-ray gas monitors. These devices were located 2.3 m downstream of the interaction point.
The device passed the laser through an entrance slit of 40 μm and a grating with 1,200 lines per mm. A miniature CCD camera was also introduced to further monitor the X-ray-excited copper. From there, the team applied kinetic Boltzmann equations with finite-temperature extensions of DFT finite-temperature real-space density-functional theory to realize their final data. A 15-fs-long XFEL pulse was then used across the test copper edges, where measurements showed intensity could be doubled.
BOLTZMANN SOLVER Software
Boltzmann kinetic equation solver is a custom-made simulation software package that enables the modeling of x-ray pulse irradiation on bulk material. The program was created by Prof. Ziaja-Motyka in 2004 and has been instrumental in WDM research to date. The simulations allowed engineers to simulate changes in the energy level of WDM against alternate laser intensities. This software provided valuable insight and saved time, money, and resources.
XANES
X-ray absorption near-edge structure spectroscopy (XANES) was also integrated into the testing process. This unit monitored the valence electron state and the atomic structure during the experimentation. It was ideally suited for the task due to its full spectral bandwidth, which enabled the team to better understand the transitional stages of the material.
Results
The test results revealed some key details about the process. For one, x-ray intensity has a direct correlation to ionization. This process causes drastic changes in the energy levels brought on by collisions of atoms in the excited state. The pace and intensity of these collisions were relative to the amount of energy the laser pulse provided.
Interestingly, the team noticed that below a pulse intensity of 1015W cm−2, an absorption peak can be obtained. They gradually increased the laser intensity until the testing equipment showed the matter becoming opaque. When the intensity was increased further, the matter became transparent to the laser pulse. As such, the study reveals that at a certain high energy level x-rays cannot be absorbed by WDM.
Benefits
There are several benefits that this research brings to the market. The new system provides a deeper understanding of WDM, how it forms, and its capabilities under certain energy levels. The data provided by researchers helps astrophysicists and nuclear engineers better understand how this matter state can benefit the world.
Understanding the thermodynamics of WDM opens the door to new possibilities. This technology enables stronger materials and testing procedures. These steps will enable humans to create more powerful and longer-lasting spacecraft that could have the ability to generate energy using new fusion methods.
Researchers
The research was hosted by the Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN) in Cracow. Nina Rohringer was the lead researcher. Additionally, Prof. Beata Ziaja-Motyka and Dr. Laurent Mercadier from the European XFEL participated in the study that was partly financed by the Institute of Nuclear Physics of the Polish Academy of Sciences.
Companies that Could Benefit from This Study
Several firms are positioned to capitalize on this research ranging from aeronautical companies to those working on new fusion methods, new opportunities are available. This study can help improve current offerings and enhance products in the future. As such, these companies hold vital positions in their market and are seen as positive holds for traders.
1. Exelon Corporation 
The Exelon Corporation entered the market in 2020 following the merger of two high-profile energy firms, PECO and Unicom. The company is one of the largest energy suppliers in North America and has headquarters in Chicago, IL. It’s a Fortune 500 company and is recognized as one of the largest and most successful providers in the market. It also has a strong focus on community, with +20K employees dedicated to workforce development and driving community outreach.
Exelon is a smart stock to add to your portfolio. The company has six regulated utilities and controls over $101B in assets. Additionally, it has 21 nuclear reactors active across 12 power plants in the US. All of these factors position Exelon as a market pioneer and a wise addition to your portfolio.
2. Lockheed Martin 
Lockheed Martin officially entered the market following the merger of Lockheed and Martin Marietta in the 1950s. The company is a pioneer in the aerodynamics, military, drive, rotary, and space sectors. As such, it’s uniquely positioned to leverage the researchers’ efforts immediately.
Lockheed is responsible for some of the most iconic airplanes that hit the sky. They also have a major stake in the US defense industry where it is known for its high-tech aeronautics. A better understanding of WDM could improve their offering in numerous ways. For one, it could open the door for new propulsion systems. Also, it would allow engineers to model more effective aircraft using new processes and models.
Notably, Lockheed Martin is a massive part of the US industrial complex. It currently employs +122k people globally and has +350 facilities. These factors, plus a growing demand for its products following quality control concerns from Boeing, have made LockeheadMartin a wise addition to your portfolio.
Future of WDM Research And Applications
You can expect to see the data collected from this study put to good use immediately across multiple industries. The models created will help researchers further the fields of X-ray pulse-shaping, which will drastically improve monitoring capabilities and provide a glimpse into what was once invisible to researchers.
Metallic Heat Shields of Spacecraft
One location where WDM is common is when a spacecraft enters the Earth’s atmosphere. Whenever a craft re-enters the earth’s atmosphere the temperature and radiation reach a level that creates WDM. The research put forth in the study will help engineers create more efficient and stronger spacecraft heat shields that can disperse the WMD energy safely.
Controlled Nuclear Fusion (ICF – Inertial Confinement Fusion)
Researchers have long dreamed of low-cost nuclear fusion. This research takes the world one step closer to understanding and achieving that goal. The team has put forth substantial evidence and new methods that enable future researchers to monitor atomic changes accurately to create more effective fusion models. As such, this research could one day lead to clean energy for everyone.
More Research is Needed
The study has sparked interest in harnessing WDM’s capabilities. Currently, the substance can be found in small stars, planets, dwarfs, particle beam interactions, ablation of metals, and intense laser interaction. This new method may reveal even more locations where this universe-building substance exists. As such, researchers are preparing for more testing in the coming weeks as their findings undergo peer review.
Warm Dense Matter (WDM) – Still Lots to Learn
It’s crazy to think that researchers are just now becoming aware of how WDM operates. This common material state is at the core of existence and the more people understand about it, the more it becomes evident it could unlock power sources that are orders of magnitude past what’s currently in use. As such, these researchers deserve a salute for helping to shed light on one of the universe’s oldest mysteries.
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