New orbit for electrons

Energy savings and a solution to a beam orbit correction problem are the results of a recent optimization carried out as part of a project initiated by Dr. Roman Panaś of the Accelerators Department. The correction problems stemmed from suboptimal alignment of the electron beam position “centers” (so-called offsets). It turned out that the correction magnets were undergoing periodic saturation, which made it impossible to maintain the correct orbit. Optimization of the beam orbit was essential, as it indirectly affects the quality and power of synchrotron light. It took about 2 months to develop and implement the new algorithms.

Precision at the synchrotron

Synchrotrons are a large, if not the largest, research infrastructure. Despite their size and diameters that range from tens to hundreds of meters, the precision of individual components is extremely important. As with a space rocket, accuracy to the hundredth of a millimeter on a synchrotron is crucial to the operation of the entire machine. This is why the synchrotron beam optimization project was such a great challenge. At the center of the initiative were the correction magnets, which directly affect the orbit of the electrons in the circular accelerator (ring). The orbit of electrons is determined by an algorithm and corrected in the vertical and horizontal axes with an accuracy that reaches fractions of micrometers.

The correction magnets got periodically saturated

The accumulation ring, in which the electrons circulate, is made up of 12 blocks of electromagnets. These blocks are called Double-Bend Achromat (DBA) cells. A typical DBA cell consists of two bending magnets, focusing magnets, and correction magnets. It is the latter that the team of researchers led by Dr. Roman Panaś, the originator of the project, focused on.

Steering magnets are responsible for keeping circulating electrons at the correct orbit. Until now, many power supplies for the correction magnets went to maximum currents, which is called saturation (reaching values of 11 A). This caused disturbances in the proper functioning of the beam correction. When electron beam is not properly corrected, it begins to oscillate in an uncontrolled manner, and resulting in faster electron beam losses.

Read more on the SOLARIS website

Researchers investigate the origins of superconductivity

The first scientific paper published with data obtained at the EMA beamline studied the relationship between skutterudite’s superconducting properties and the distance between their atoms.

In Brazil, about 7.5% of the electricity produced is lost in transmission and distribution. This happens because the materials that make up these systems are not perfect electrical conductors and dissipate part of the energy, for example, in the form of heat. Similarly, even though electric cars are much more efficient than combustion-engine vehicles, they can still lose up to 15 percent of their energy during the charging process.

Thus, the challenges of achieving sustainable development lie not only in the availability of abundant, clean, and cheap energy, but also in the development of new, efficient, and low-cost energy transport and storage systems.

In turn, these new systems require research into new materials with special properties, such as superconducting materials. Superconductivity is the property that allows certain materials to conduct electric current without resistance and therefore without energy loss. Currently, however, a major limitation for the large-scale use of superconducting materials is their need to be kept at very low temperatures, close to absolute zero (-273.15°C), which requires their association with large cooling infrastructures. In these conditions, superconductors have applications in MRI machines and other high-performance medical equipment, as well as in scientific research equipment, such as the super-magnets used in particle accelerators.

Although superconductivity has been known for more than a century, its origin is still a matter of intense debate in the scientific community. Why do certain materials exhibit superconductivity while others do not? Once this is known, it will be possible to build materials that are superconducting even under ambient temperature and pressure conditions, allowing a true technological revolution, not only in the transmission and storage of energy but also in all kinds of electrical equipment in everyday life.

The movement of electrons without resistance along a superconducting material is understood so far to be possible by the union of two electrons (called Cooper pairs) that, with the help of a deformation in the material’s lattice (called a phonon), can overcome Coulombian repulsion and start moving as a single particle.

The question to which there is still no satisfactory answer is: what makes these electrons want to come together in pairs? Among the various hypotheses, one possibility is that this phenomenon would be connected to the distance between the atoms in the superconducting material.

Thus, in research published in the journal Materials, researchers from the Brazilian Center for Research in Energy and Materials (CNPEM), and collaborators from Germany, investigated two materials (LaPt4Ge12 and PrPt4Ge12) whose crystalline structure is known as skutterudite to test the hypothesis that superconductivity would be related to the distance between the atoms of the material. This was the first scientific paper published with data obtained at the EMA beamline of CNPEM’s synchrotron light source Sirius.

Read more on the LNLS website

Multilayer stack opens door to low-power electronics

Researchers found that a stack of ultrathin materials, characterized in part at the Advanced Light Source (ALS), exhibits a phenomenon called negative capacitance, which reduces the voltage required for transistor operation.

The material is fully compatible with today’s silicon-based technology and is capable of reducing power consumption without sacrificing transistor size or performance.

High efficiency, low disruption

Microelectronics is expected to account for about 5% of total electricity production by 2030 thanks to ever-increasing demands for information processing. Maintaining progress will require a fundamental shift toward more efficient devices, with an emphasis on materials compatible with state-of-the-art silicon technology.

The phenomenon of negative capacitance represents one possible solution, promising to significantly reduce power consumption in electronic devices while fitting seamlessly into current semiconductor protocols. In this work, researchers took a key step toward integrating negative capacitance into advanced transistors, with support from various government and industrial groups including Samsung, Intel, SK hynix, Applied Materials, and DARPA.

Inside the gate

A transistor is essentially an on-off switch for the flow of current through a semiconductor, activated by a small voltage from a “gate” electrode. A thin insulating layer (the gate oxide) separates the semiconductor from the gate. Increasing the gate oxide’s ability to store charge (i.e., its capacitance) lowers the transistor’s operating voltage and thus reduces overall power consumption.

In advanced silicon transistors, the gate oxide is a combination of silicon oxide (SiO2) and hafnium oxide (HfO2). In this work, researchers replaced the HfO2 with a multilayered stack that displays negative capacitance—a counterintuitive effect in which decreasing the gate voltage increases the stored charge on the gate oxide, thus maintaining performance at reduced power.

Read more on the Berkeley Laboratory website

Image: Artistic rendering of a multilayered structure that exhibits negative capacitance, integrated onto a silicon chip. Incorporating this material into advanced silicon transistors could make devices more energy efficient.

Credit: Ella Maru Studio/UC Berkeley

Giant Rashba semiconductors show unconventional dynamics with potential applications

Germanium telluride is a strong candidate for use in functional spintronic devices due to its giant Rashba-effect. Now, scientists at HZB have discovered another intriguing phenomenon in GeTe by studying the electronic response to thermal excitation of the samples. To their surprise, the subsequent relaxation proceeded fundamentally different to that of conventional semimetals. By delicately controlling the fine details of the underlying electronic structure, new functionalities of this class of materials could be conceived. 

In recent decades, the complexity and functionality of silicon-based technologies has increased exponentially, commensurate with the ever-growing demand for smaller, more capable devices. However, the silicon age is coming to an end.  With increasing miniaturisation, undesirable quantum effects and thermal losses are becoming an ever-greater obstacle. Further progress requires new materials that harness quantum effects rather than avoid them. Spintronic devices, which use spins of electrons rather than their charge, promise more energy efficient devices with significantly enhanced switching times and with entirely new functionalities.

Spintronic devices are coming

Candidates for spintronic devices are semiconductor materials wherein the spins are coupled with the orbital motion of the electrons. This so-called Rashba effect occurs in a number of non-magnetic semiconductors and semi-metallic compounds and allows, among other things, to manipulate the spins in the material by an electric field.

First study in a non equilibrium state

Germanium telluride hosts one of the largest Rashba effects of all semiconducting systems. Until now, however, germanium telluride has only been studied in thermal equilibrium. Now, for the first time, a team led by HZB physicist Jaime-Sanchez-Barriga has specifically accessed a non-equilibrium state in GeTe samples at BESSY II and investigated in detail how equilibrium is restored in the material on ultrafast (<10-12 seconds) timescales. In the process, the physicists encountered a new and unexpected phenomenon.

First, the sample was excited with an infrared pulse and then measured with high time resolution using angle-resolved photoemission spectroscopy (tr-ARPES). “For the first time, we were able to observe and characterise all phases of excitation, thermalisation and relaxation on ultrashort time scales,” says Sánchez-Barriga. The most important result: “The data show that the thermal equilibrium between the system of electrons and the crystal lattice is restored in a highly unconventional and counterintuitive way”, explains one of the lead authors, Oliver Clark.

Read more on the HZB website

Image: Left: Electronic structure of GeTe taken with 11 eV photons at BESSY-II, showing the band dispersions of bulk (BS) and surface Rashba states (SS1, SS2) in equilibrium. Middle: Zoom-in on the region of the Rashba states measured with fs-laser 6 eV photons. Right: Corresponding out-of-equilibrium dispersions following excitation by the pump pulse.

Recycling alginate composites for thermal insulation

Thermal insulation materials represent one the most straightforward, yet effective, technologies for improving the energy efficiency of buildings (and not only) – one of the key strategies for reducing carbon emissions. Natural-based materials and downcycled industrial and agricultural waste, thanks to their potentially reduced environmental footprint, have already made their way up to the market with the aim of limiting the ever-growing waste stream generated by the industrial sector. Research efforts on the topic are currently mainly focused on developing new insulation solutions, in which waste is reconverted as a new valuable resource. Carbohydrates, such as alginate, cellulose or chitosanare currently extensively studied base materials for thermal insulation systems, in the form of aerogels or as low-impact binding agents in waste-filled panels. Unfortunately, little or no attention has been paid to the end-of-life fate of these recycled materials; disposal (or incineration) still represents the only available option. This unprofitable scenario is even more critical in the case of polysaccharide-based composites specifically developed to reuse industrial waste. 

This was the starting point of our work, mainly conducted at the laboratories of the Engineering and Architecture department of the University of Trieste, in collaboration with TomoLab at Elettra. We developed a recycling process for an alginate-based thermal insulation foam, in which the original material is fully recovered and the thermal and acoustic insulation performances are maintained. The original foam is produced via a patented process in which alginate is used as the host poly-anionic matrix for industrial fiberglass waste. 

Read more on the Elettra website

Image: SEM and μCT image of oCAF

Credit: Figure reprinted from Carbohydrate Polymers, 251, Matteo Cibinel, Giorgia Pugliese, Davide Porrelli, Lucia Marsich, Vanni Lughi, Recycling alginate composites for thermal insulation, 116995, Copyright 2021, with permission from Elsevier.