A New Way To See The High-Energy Sky

Credit: HAWC Collaboration

University of Maryland (UMD) physicists pioneered development of observatory that has located new high-energy sources in the universe and provided more detail on known sources in first year of full operation. HAWC observations show that a previously known gamma ray source in the Milky Way galaxy, TeV J1930+188, which is probably due to a pulsar wind nebula, is far more complicated than originally thought. Where researchers previously identified a single gamma ray source, HAWC identified several hot spots. The United States and Mexico constructed the High Altitude Water Cherenkov (HAWC) Gamma-ray Observatory to observe some of the most energetic phenomena in the known universe--the aftermath when massive stars die, glowing clouds of electrons around rapidly spinning neutron stars, and supermassive black holes devouring matter and spitting out powerful jets of particles. These violent explosions produce high-energy gamma rays and cosmic rays, which can travel large distances--making it possible to see objects and events far outside our own galaxy. Today, scientists operating HAWC released a new survey of the sky made from the highest energy gamma rays ever observed. The new sky map, which uses data collected since the observatory began running at full capacity last March, offers a deeper understanding of high-energy processes taking place in our galaxy and beyond. "HAWC gives us a new way to see the high-energy sky," said Jordan Goodman, professor of physics at the University of Maryland, and U.S. lead investigator and spokesperson for the HAWC collaboration. "This new data from HAWC shows the galaxy in unprecedented detail, revealing new high-energy sources and previously unseen details about existing sources." HAWC researchers presented the new observation data and sky map April 18, 2016, at the American Physical Society meeting. They also participated in a press conference at the meeting. The new sky map shows many new gamma ray sources within our own Milky Way galaxy. Because HAWC observes 24 hours per day and year-round with a wide field-of-view and large area, the observatory boasts a higher energy reach especially for extended objects. In addition, HAWC can uniquely monitor for gamma ray flares by sources in our galaxy and other active galaxies, such as Markarian 421 and Markarian 501. This is a view of two-thirds of the entire sky with very-high-energy gamma rays observed by HAWC. Many sources are clearly visible in our own Milky Way galaxy, as well as two other galaxies: Markarian 421 and Markarian 501. Some well-known constellations are shown as a reference. The center of the Milky Way is located toward

Credit: HAWC Collaboration

Sagittarius. One of HAWC's new observations provides a better understanding of the high-energy nature of the Cygnus region--a northern constellation lying on the plane of the Milky Way. A multitude of neutron stars and supernova remnants call this star nursery home. HAWC scientists observed previously unknown objects in the Cygnus region and identified objects discovered earlier with sharper resolution. In a region of the Milky Way where researchers previously identified a single gamma ray source named TeV J1930+188, HAWC identified several hot spots, indicating that the region is more complicated than previously thought. "Studying these objects at the highest energies can reveal the mechanism by which they produce gamma rays and possibly help us unravel the hundred-year-old mystery of the origin of high-energy cosmic rays that bombard Earth from space," said Goodman. HAWC--located 13,500 feet above sea level on the slopes of Mexico's Volcán Sierra Negra--contains 300 detector tanks, each holding 50,000 gallons of ultrapure water with four light sensors anchored to the floor. When gamma rays or cosmic rays reach Earth's atmosphere they set off a cascade of charged particles, and when these particles reach the water in HAWC's detectors, they produce a cone-shaped flash of light known as Cherenkov radiation. The effect is much like a sonic boom produced by a supersonic jet, because the particles are traveling slightly faster than the speed of light in water when they enter the detectors. The complete array of HAWC detector tanks is seen here in Dec. 2014.

Credit: HAWC Collaboration

The light sensors record each flash of Cherenkov radiation inside the detector tanks. By comparing nanosecond differences in arrival times at each light sensor, scientists can reconstruct the angle of travel for each particle cascade. The intensity of the light indicates the primary particle's energy, and the pattern of detector hits can distinguish between gamma rays and cosmic rays. With 300 detectors spread over an area equivalent to more than three football fields, HAWC "sees" these events in relatively high resolution. "Unlike traditional telescopes, with HAWC we have now an instrument that surveys two-thirds of the sky at the highest energies, day and night," said Andrés Sandoval, Mexico spokesperson for HAWC. HAWC exhibits 15-times greater sensitivity than its predecessor--an observatory known as Milagro that operated near Los Alamos, New Mexico, and ceased taking data in 2008. In eight years of operation, Milagro found new sources of high-energy gamma rays, detected diffuse gamma rays from the Milky Way galaxy and discovered that the cosmic rays hitting earth had an unexpected non-uniformity. "HAWC will collect more data in the next few years, allowing us to reach even higher energies," said Goodman. "Combining HAWC observations with data from other instruments will allow us to extend the reach of our understanding of the most violent processes in the universe." Contacts and sources:Abby Robinson, University of Maryland (UMD) Source: http://www.ineffableisland.com/

Read More........→April 25, 2016

Nuclear battery: Chinese firm aiming for mass market production

The BV100 battery (Image: Betavolt)

Beijing Betavolt New Energy Technology Company Ltd claims to have developed a miniature atomic energy battery that can generate electricity stably and autonomously for 50 years without the need for charging or maintenance. It said the battery is currently in the pilot stage and will be put into mass production on the market.

Atomic energy batteries - also known as nuclear batteries or radioisotope batteries - work on the principle of utilising the energy released by the decay of nuclear isotopes and converting it into electrical energy through semiconductor converters.

Betavolt, which was established in April 2021, says its battery "combines nickel-63 nuclear isotope decay technology and China's first diamond semiconductor (4th generation semiconductor) module to successfully realise the miniaturisation of atomic energy batteries".

The company's team of scientists developed a unique single-crystal diamond semiconductor that is just 10 microns thick, placing a 2-micron-thick nickel-63 sheet between two diamond semiconductor converters. The decay energy of the radioactive source is converted into an electrical current, forming an independent unit. Betavolt said its nuclear batteries are modular and can be composed of dozens or hundreds of independent unit modules and can be used in series and parallel, so battery products of different sizes and capacities can be manufactured.

The composition of a nuclear battery (Image: Betavolt)

Betavolt says its batteries can meet the needs of long-lasting power supply in multiple scenarios such as aerospace, AI equipment, medical equipment, micro-electromechanical systems, advanced sensors, small drones and micro-robots. "If policies allow, atomic energy batteries can allow a mobile phone to never be charged, and drones that can only fly for 15 minutes can fly continuously," it said.

The first battery that the company plans to launch is the BV100, which it claims will be the world's first nuclear battery to be mass-produced. Measuring 15mm by 15mm and 5 mm thick, the battery can generate 100 microwatts, with a voltage of 3V. The company plans to launch a 1-watt battery in 2025.

Betavolt says its atomic energy battery is "absolutely safe, has no external radiation, and is suitable for use in medical devices such as pacemakers, artificial hearts, and cochleas in the human body". It adds: "Atomic energy batteries are environmentally friendly. After the decay period, the nickel-63 isotope as the radioactive source turns into a stable isotope of copper, which is non-radioactive and does not pose any threat or pollution to the environment."

The company plans to continue research on using isotopes such as strontium-90, promethium-147 and deuterium to develop atomic energy batteries with higher power and a service life of 2-30 years.Researched and written by World Nuclear News. Nuclear battery: Chinese firm aiming for mass market production : Corporate - World Nuclear News

Read More........→January 31, 2024

Can Artificial Trees Generate Renewable Power

Credit: Tech Briefs

New tools for harvesting wind energy may soon look less like giant windmills and more like tiny leafless trees. A project at The Ohio State University is testing whether high-tech objects that look a bit like artificial trees can generate renewable power when they are shaken by the wind--or by the sway of a tall building, traffic on a bridge or even seismic activity. In a recent issue of the Journal of Sound and Vibration, researchers report that they've uncovered something new about the vibrations that pass through tree-shaped objects when they are shaken. Specifically, they've demonstrated that tree-like structures made with electromechanical materials can convert random forces--such as winds or footfalls on a bridge--into strong structural vibrations that are ideal for generating electricity. The idea may conjure images of fields full of mechanical trees swaying in the breeze. But the technology may prove most valuable when applied on a small scale, in situations where other renewable energy sources such as solar are not an option, said project leader Ryan Harne, assistant professor of mechanical and aerospace engineering at Ohio State, and director of the Laboratory of Sound and Vibration Research. The "trees" themselves would be very simple structures: think of a trunk with a few branches--no leaves required. Early applications would include powering the sensors that monitor the structural integrity and health of civil infrastructure, such as buildings and bridges. Harne envisions tiny trees feeding voltages to a sensor on the underside of a bridge, or on a girder deep inside a high-rise building. The project takes advantage of the plentiful vibrational energy that surrounds us every day, he said. Some sources are wind-induced structural motions, seismic activity and human activity. "Buildings sway ever so slightly in the wind, bridges oscillate when we drive on them and car suspensions absorb bumps in the road," he said. "In fact, there's a massive amount of kinetic energy associated with those motions that is otherwise lost. We want to recover and recycle some of that energy." Sensors monitor the soundness of a structure by detecting the vibrations that pass through it, he explained. The initial aim of the project is to turn those vibrations into electricity, so that structural monitoring systems could actually be powered by the same vibrations they are monitoring. Today, the only way to power most structural sensors is to use batteries or plug the sensors directly into power lines, both of which are expensive and hard to manage for sensors planted in remote locations. If sensors could capture vibrational energy, they could acquire and wirelessly transmit their data is a truly self-sufficient way. At first, the idea of using tree-like devices to capture wind or vibration energies may seem straightforward, because real trees obviously dissipate energy when they sway. And other research groups have tested the effectiveness of similar tree structures using idealized--that is, not random--vibrations. But until now, researchers haven't made a concerted effort to capture realistic ambient vibrations with a tree-shaped electromechanical device--mainly because it was assumed that random forces of nature wouldn't be very suitable for generating the consistent oscillations that yield useful electrical energies. First, through mathematical modeling, Harne determined that it is possible for tree-like structures to maintain vibrations at a consistent frequency despite large, random inputs, so that the energy can be effectively captured and stored via power circuitry. The phenomenon is called internal resonance, and it's how certain mechanical systems dissipate internal energies. In particular, he determined that he could exploit internal resonance to coax an electromechanical tree to vibrate with large amplitudes at a consistent low frequency, even when the tree was experiencing only high frequency forces. It even worked when these forces were significantly overwhelmed by extra random noise, as natural ambient vibrations would be in many environments. He and his colleagues tested the mathematical model in an experiment, where they built a tree-like device out of two small steel beams--one a tree "trunk" and the other a "branch"--connected by a strip of an electromechanical material, polyvinylidene fluoride (PVDF), to convert the structural oscillations into electrical energy. They installed the model tree on a device that shook it back and forth at high frequencies. At first, to the eye, the tree didn't seem to move because the device oscillated with only small amplitudes at a high frequency. Regardless, the PVDF produced a small voltage from the motion: about 0.8 volts. Then they added noise to the system, as if the tree were being randomly nudged slightly more one way or the other. That's when the tree began displaying what Harne called "saturation phenomena": It reached a tipping point where the high frequency energy was suddenly channeled into a low frequency oscillation. At this point, the tree swayed noticeably back and forth, with the trunk and branch vibrating in sync. This low frequency motion produced more than double the voltage--around 2 volts. Those are low voltages, but the experiment was a proof-of-concept: Random energies can produce vibrations that are useful for generating electricity. "In addition, we introduced massive amounts of noise, and found that the saturation phenomenon is very robust, and the voltage output reliable. That wasn't known before," Harne said. Harne will continue this work, which he began when he was a postdoctoral researcher at the University of Michigan. There, his colleagues and co-authors on the paper were Kon-Well Wang and Anqi Sun of the Department of Mechanical Engineering. Source: http://www.ineffableisland.com/

• Contacts and sources: Ryan Harne, The Ohio State University, 
• Written by Pam Frost Gorder 
• The initial phase of this research was supported by the University of Michigan Summer Undergraduate Research in Engineering program and the University of Michigan Collegiate Professorship. 

Read More........→February 05, 2016