Cosmic rays: space messengers

30 November 2017

60 second science: ChipIR
(Credit: STFC)

As we reach the last day of November with the cold, dark, evenings upon us, many will no doubt be looking forward to the festive season. But as lots of people prepare for the celebrations that come with the faint jingle of bells in the distance, the focus for many ast-roparticle physicists around the globe will be on another occasion in their calendar: International Cosmic Ray Day. Today, 30 November 2017, is a day of celebration organised by the Deutsches Elektronen Syn¬chrotron (DESY), a research institute in Hamburg, Germany. The aim is to bring stu¬dents, teachers and scientists together to learn about and discuss the phenomena of galactic cosmic rays.

These tiny, high-energy particles arrive on Earth from outer space and are atom fragments composed mainly of protons (positively charged particles), electrons (negatively charged particles) and atomic nuclei such as from the element Uranium.

As cosmic rays rain down on Earth, “primary” rays collide with the nuclei of atoms in the Earth’s upper atmosphere, creating more particles, such as pions, a type of subatomic particle composed of quarks and antiquarks. Whilst the primary rays rarely make it to sea level, these “secondary” particles are ejected from these atmospheric collisions and penetrate below ground, even passing through our bodies. Although the Earth’s magnetic field does a very good job of shielding us from the health effects of this cosmic radiation at ground level, solar storms such as the Carrington event observed in 1859, can wreak havoc on electronic devices, hindering the Earth’s communication networks.

Since their discovery in 1912 by Austrian physicist and Nobel Prize Laureate Victor Hess as he travelled in a hot air balloon during an eclipse, these particles have long been a very intriguing topic of conversation. Every day an Alpha-magnetic spectrometer (see image), installed on the International Space Station, detects 15 million cosmic ray particles, the information from which is sent to a control room at CERN in Switzerland. Scientists can then use this information to investigate the undiscovered secrets of the universe.

As a world-class, innovation-driven organisation, the Science and Technology Facilities Council has supported a vast range of research in this field over the past few years. At the Rutherford Appleton Laboratory in Didcot, Oxfordshire, scientists have come together to attempt to not only discover more about these tiny space messengers but to aid industry in the design of infrastructure to improve both the safety and efficiency of vulnerable electronic devices. Through the work completed at ISIS, the Central Laser Facility and RAL Space, scientists at STFC are completing pioneering research to understand and mitigate natural radiation effects.

In February 2017, instrument scientist Dr Christopher Frost travelled to the American Association for the Advancement of Science conference in Boston, USA. His purpose was to promote the unique capabilities of a new instrument built at the ISIS Neutron and Muon Source called ChipIr (see image). This instrument, which began commissioning this year, is designed to study how silicon microchips respond to cosmic neutron radiation. Within the instrument, microelectronic devices, such as systems found on the ground or aboard aircraft, are irradiated with very high-energy neutrons. By virtue of the intensity of the beam, the exposure a device would receive during one hour of testing in ChipIr is equivalent to what it would receive in thousands of years of use on Earth. This facilitates the testing of electronic systems, so that potential problems can be identified and microelectronics can be made that are both reliable and robust, for use in the aviation, automotive and communication industries, to name a few.

Not only can cosmic rays be detrimental to the functioning of electronic devices, they pose a deadly threat to astronauts in space. In fact, space weather is quoted as being the single greatest obstacle to deep space travel by international space agencies. At RAL Space, astrophysicists and engineers recently sought to explore the effectiveness of an artificial mini-magnetosphere; on Earth this is the area of space around our planet that it controlled by Earth’s magnetic field, as a potential radiation shelter for use in human space missions. The result of this work is to hopefully aid spacecraft engineers in the design and development of more effective radiation protection in space.

The Central Laser Facility houses one of the world’s most powerful lasers that has recently been used to replicate the high energy particle radiation that surrounds our planet. Vulcan is a petawatt (1015 Watts) laser system that delivers a focused beam which is 10,000 times more powerful than the National Grid. Whilst conventional cyclotrons and linear particle accelerators are incredibly powerful, they can only produce mono-energetic particles, that is, radiation that consists of particles (or waves) with narrow energy ranges. However, when the extreme intensity of the Vulcan laser shoots a piece of metal it generates a micro-sized but supercharged particle accelerator that gives off beams of radiation that are very similar to space weather conditions. This means that scientists can investigate how space weather affects humans and consequently aid in the development of more resilient satellite and rocket equipment. In May 2017, for example, researchers led by Professor Bernhard Hidding from the University of Strathclyde used Vulcan at RAL (along with another laser-plasma accelerator at the University of Dusseldorf) to produce broadband electrons and protons. These particles resembled what you would find in van-Allen radiation belts, zones of energetic particles, held around our planet by the Earth’s protective magnetic fields. This work provides great promise for future electronics testing.

Despite their very small size, cosmic rays are of great value within the astroparticle physics community to the extent that many believe that these particles are the key to discovering the secrets of the universe and its origins, acting as tiny space messengers from afar. In fact, by studying the frequency by which certain particles occur, we can estimate the relative abundance of particular elements in the universe. Not only that, but scientists worldwide hope that cosmic rays will be able to reveal hidden insights into anti-matter and even the possible existence of dark matter.

Science and Technology Facilities Council Switchboard: 01793 442000