Nuclear physics

Definition:Nuclear physicists are scientists who analyze the energy generated within cells’ nuclei and how this energy may be applied in the modern world. The field began in the early twentieth century as part of weapons research, culminating in nuclear bombs. However, nuclear physics also led to the establishment of alternatives to coal and other sources of energy. In 2012, nuclear physics is used to treat diseases such as cancer, determine the age of items uncovered in archaeological digs, and change the properties of solids to use them as semiconductors?an invaluable tool in engineering. Scientists continue to find applications for the products of nuclear-physics research.

Basic Principles

Nuclear physics owes its roots to the 1896 discovery by Henri Becquerel of radiation emanating from phosphorescent (glowing) uranium salts. Marie Curie and Pierre Curie continued Becquerel’s research, finding more radioactive elements and coining the term radioactivity. Over time, many more naturally radioactive substances were discovered. During this period, greater attention was paid to the nature of radioactivity, with scientists tracing the radiation to atoms within the nuclei of cells. By the 1930s, it became apparent to scientists that radiation in many materials was increased, or “excited,” when exposed to light and other forms of energy. This concept, nuclear fission, became the launching point for the development of nuclear weapons.

Although there were military application for nuclear physics in the 1930s, over the course of the Cold War nuclear physics also saw applications as a source of energy. Nuclear energy has since become a major source of power throughout the industrialized world, and it is increasingly being applied in developing nations as well. This knowledge has also been applied elsewhere, largely in the field of health care, where nuclear medicine is being used for treatment of cancer and other ailments.

Development in the field of nuclear physics is reliant on the particle accelerator, a large piece of technology that uses electronic or electromagnetic fields to speed subatomic particles and have them collide with other particles. The resulting high-energy rays (x-rays and gamma rays) are then cataloged and analyzed by nuclear physicists. This research helps them understand the nature of nuclear energy and its place within the natural and industrialized worlds.

Core Concepts

Nuclear physicists analyze the energy produced by natural and engineered nuclear reactions, as well as the effects those reactions have on their respective environments. They research the atomic forces that cause radiation, creating models and developing theories about how subatomic particles are structured and reorganized during nuclear reactions. Nuclear physicists use the data they uncover during their research to draft scholarly papers and other literature, along with models that can be used as the basis for further research. Engineers, scientists, and others have applied the work of nuclear physicists to the development of medicine, weapons, energy systems, and other technologies.

Subparticles. The central focus of a nuclear physicist is the subatomic particle. The basic premise on which nuclear physics operates is the notion that within the nucleus of any atom exists a group of charged particles. There is a vast array of such particles, including protons, neutrons, electrons, quarks, and photons. Some of these particles are researched in earthbound substances, such as rocks and other compounds, while other subatomic particles radiate from space-based sources.

When charged, these particles come into contact with one another, or collide, causing a reaction. Such reactions can change the composition of the substance in which the interaction occurs. The reaction also triggers a release of energy in the form of radiation. Nuclear physicists analyze these reactions to better understand their nature and the implications for the world.

Technology. One of the ways nuclear physicists detect and quantify nuclear radiation and reactions is through the use of a frequency analyzer. This device works on the principle that radiation may be detected in the form of sound waves. The analyzer’s microphone picks up the sound, and the device converts it into voltage and organizes the samples with numerical values. These samples are then analyzed for their frequencies and intensities.

Another set of devices used to analyze nuclear samples uses light rather than sound. Spectrometers, for example, operate on the basis that each atom emits its own wavelength of light. Spectrometers emit light beams at a sample and then analyze the responding emissions from the atoms within that sample. Nuclear physicists also use lasers, targeting a sample and calculating its emissions as well.

Still another vital tool utilized by nuclear physicists is a particle accelerator. These complex devices use electromagnetic fields to accelerate a stream of subatomic particles, such as protons and electrons, as they travel through a sealed chamber. Nuclear physicists then study the energy that is released when these charged particles collide with each other. Particle accelerators appear in many different configurations and sizes. Some, like those used in hospitals and medical-research facilities, are mobile and can fit in a single room. Others, like the Large Hadron Collider (LHC) in Switzerland, are considerably larger, requiring much greater space and facilities. These devices—also known as “atom smashers”—may be circular in configuration (cyclotrons) or operate on a straight line (linear accelerators).

Semiconductors. Nuclear physicists frequently use semiconductors as the basis for their experiments. There are three general types of materials in the natural world—those that allow for energy to be transmitted through them (conductors), those that resist such charges (insulators), and semiconductors, which resist some charges and allow others. Nuclear physicists may use a particle accelerator to run a stream of charged particles through a semiconductor. The resulting reaction can dramatically change the chemical-electric composition of that substance. By infusing different ions into a semiconductor, a process called doping, scientists can alter its structure and, therefore, its uses. One well-known semiconductor, for example, is the element silicon, which has many different applications after the doping process is applied, including the development of jewels and computer chips.

Computer Software. Nuclear physicists must compile a great deal of data from their experiments, collating it into manageable components in order to analyze it and generate reports. Relevant computer systems and software are essential for this purpose. Scientists rely on analytical and scientific software capable of collating the information collected into easily accessed components. Among the types of scientific software available are the three-dimensional Opera suite and specialized databases. Additionally, nuclear physicists rely on high-definition graphic imaging and modeling systems like Adobe Photoshop, the GNU Image Manipulation Program, and computer-aided design (CAD) software, such as Autodesk’s AutoCAD suite.

Research Projects and Presentations. Nuclear physicists do not develop nuclear technologies, but the theories they introduce and the discoveries they make lay the groundwork for such innovations. These hypotheses and revelations are presented in scholarly articles, papers, and books. Nuclear physicists are generally expected to have or be on track to receive a doctorate, and their dissertations often takes several years’ worth of research, gathered while working at a particle-accelerator facility or in another scientific venue. The dissertation serves as a nuclear physicist’s resume after receiving a doctorate.

Following graduation, nuclear physicists must produce many more scholarly works throughout their careers. They publish such pieces in scientific periodicals like the Journal of Nuclear Physics and the American Journal of Physics. Frequently, they are called upon to present their findings at nuclear physics-oriented conferences, where they may give a formal presentation on the paper in question. A large number of nuclear physicists are also university professors, presenting their theories—as well as the theories of their peers and other scientists, past and present—to aspiring nuclear physicists at the undergraduate and graduate levels.

Applications Past and Present

Although one of the first applications of nuclear physics was the creation of the atomic bomb, nuclear physicists have discovered a vast array of other applications for the discipline. Among these applications, many of which are presently being developed for the future, are nuclear energy, nuclear weapons, nuclear medicine, and archaeology.

Energy Sources. One of the most common applications for nuclear physics is in the field of energy. Nuclear energy entails the use of the radioactive isotope known as uranium-235, chosen because its atoms are easily split. This material is mined and converted into rods, which are bundled and placed into a tank of water in a nuclear reactor. The rods are then showered with neutrons, causing the atoms in the rods to split, a reaction called fission. The nuclear reaction generates a great deal of heat, which causes the water to convert to steam, which is then run through turbines. The turbines convert the steam into electricity, which is then transferred onto the grid for consumption. Once the rods in the chamber are spent, special control rods of a neutron-absorbing material are placed in the water to absorb the excess neutrons.

Nuclear energy has long been embraced as a more efficient alternative to coal, gas, and other types of energy production, generating larger volumes of energy. However, there are risks involved with nuclear energy, including the storage of the spent uranium and control rods after use and the concern that nuclear power plants, if breached, could cause devastation to the surrounding populations. The disasters at the Three Mile Island and Chernobyl facilities during the late twentieth century proved the existence of such dangers, as did the Fukushima Daiichi nuclear facilities in Japan following the 2011 earthquake and tsunami. Nuclear physicists continue to research ways to ensure safe fission reactions at these facilities, as well as study ways to better detect radiation in order to prevent more such incidents.

Nuclear energy is not applied solely to public grids. It is commonly used on naval vessels such as submarines and aircraft carriers. These ships use smaller reactors than those at nuclear power plants, but the same approach is used. Nuclear physicists are also exploring the effects of nuclear-fission reactions in space, research that could lead to nuclear-powered spacecraft in the future.

Despite the prevailing use of nuclear fission during the first decades of the twenty-first century, by that point many researchers had also begun exploring the potential use of nuclear fusion, which involves combing two light nuclei into a heavier nucleus and releasing a massive amount of energy, as an energy source. Fusion shares many of the same benefits as fission-based power; for example, it does not produce greenhouse gases. However, fusion has many additional advantages. It has no potential to cause a catastrophic nuclear meltdown, does not produce long-lasting radioactive waste, and does not use materials which could be repurposed into atomic weapons. Additionally, fusion produces far greater amounts of energy per reaction than fission does. Scientists were able to achieve a number of fusion-related breakthroughs during the 2010s and 2020s. Notably, in December 2022, researchers in the United States achieved a net energy gain during a nuclear fusion test.

Weapons. The atom bombs that devastated the Japanese cities of Hiroshima and Nagasaki in 1945 were the products of years of research in nuclear physics. Atom bombs function by nuclear fission. They contained radioactive uranium surrounded by dynamite; when the dynamite is detonated, the force of the explosion compresses the already-unstable uranium, causing its neutrons to release great quantities of energy during a chain reaction. This chain reaction is capable of destroying an entire city.

The capability for destruction contained within those two bombs was considerably smaller than that of the missiles developed thereafter, as nuclear research continued at breakneck speed during the Cold War. The atom bomb’s successors—hydrogen and thermonuclear weapons—were based on physics research performed not on fission but on fusion. Such weapons comprise a core of unstable isotopes (elements with added nuclei) of hydrogen surrounded by smaller atom bombs and encased in radioactive plutonium. When detonated, the bombs’ explosive force causes the isotopes to compress violently, forming new nuclei and releasing tremendous amounts of energy. Meanwhile, the atom bombs also cause a fission reaction, adding to the weapon’s destructive capability.

The Cold War was driven in part by a race to build and position nuclear weapons, but leaders worked to avoid any confrontation that might warrant their use. Ultimately, the United States and the Soviet Union began dismantling their respective nuclear arsenals. However, other nations, as well as global terrorist organizations, are pursuing nuclear weapons of their own in the twenty-first century. Although some nations are also developing missiles that could carry a nuclear warhead, terrorists would rather build smaller weapons that can be smuggled into target areas. These weapons could be generate a fission or fusion reaction, but on a much smaller scale. Their purpose is often not to destroy buildings but to contaminate the target area with large volumes of radiation. Such a weapon is known as a dirty bomb, and nuclear physicists’ knowledge of radiation and nuclear science is proving useful in the detection of this post-Cold War form of nuclear warfare. They are working with engineers and others to research the types of radiation that are emitted by active nuclear weapons, thereby helping government agents track stolen bombs and bomb components before they can put people in harm’s way.

Medicine. The study of radiation through nuclear physics has had a great impact on the field of medicine. One of the earliest examples of this is the x-ray machine. This device emits x-rays through a person; the interference detected by the machine provides a detailed image of organs, bones, and other structures. X-ray machines have been improved with the introduction of computer-aided tomography (CAT), which combines x-ray devices with computer-signal-processing technologies, providing images of internal organs and bones without obstruction from other body parts.

The growing field of nuclear medicine has evolved beyond the x-ray machine to include nuclear magnetic resonance (NMR). This technology uses a principle of nuclear physics that states that every human body contains diverse quantities of atoms containing radiation-emitting particles known as radionuclides. These subatomic particles vary in volume based on the chemical composition of the structure in which they are found. Medical professionals use a magnetic resonance scanner to detect the radiation emitted by these particles, providing a three-dimensional image of internal organs and structures without the need for an x-ray scan. Scientists are hopeful that this innovation will enable medical professionals to detect diseases much earlier than before. Research on NMR continues to evolve as more radioactive isotopes and their subatomic particles are discovered.

In addition to medical scanning, nuclear physics has directly aided the treatment of diseases such as cancer. Medical professionals can target cancerous cells with a particle beam, which leaves noncancerous cells intact. The infusion of this radiation destabilizes the cellular structure and triggers a chain reaction that carries over into the other cells that make up the tumor. This application of nuclear physics to medicine continues to evolve, not just in terms of combating different types of cancer, but in terms of treating other diseases (such as Alzheimer’s disease) as well.

Archaeology. Archaeologists are concerned with studying civilizations, peoples, and events in human history in order to understand how humanity has developed over the millennia. An important aspect of this pursuit is archaeologists’ ability to determine the dates of origin of the artifacts they uncover. Nuclear physics is contributing greatly to this aspect of archaeology.

Central to how nuclear physics is applied to archaeological dating is the notion that radiation is the energy emitted by an object that is decaying to the point at which it becomes stable. Scientists use this principle to analyze certain types of radioactive isotopes as they decay toward that point of stability. For example, they may analyze the presence of the isotope carbon-14 in a body unearthed at a dig site. Based on the length of time it would take for carbon-14 to decay to half of its original volume—its half-life, a constant figure of 5,730 years—researchers can effectively gauge the age of that body.

This field of carbon dating has proven invaluable to the field of archaeology. Scientists continue to analyze other radioactive subparticle emissions contained within living and dead organisms, as well as other objects. As this nuclear physics-based research continues to evolve, it is anticipated that archaeologists will in the future be able to better pinpoint the ages of invaluable historical finds.

Social Context and Future Prospects

Nuclear physics has contributed greatly to modern civilization, presenting to the world a form of energy that, once understood, improved the lives of many. However, the applications of nuclear physics, particularly the development of nuclear weapons, have also had a profound and negative impact on society, beginning with the first detonation of such weapons during World War II and extending for decades during the Cold War. Even one of its most widespread benefits—nuclear energy—has generated mixed social returns: the efficiency and output associated with well-maintained nuclear power plants have been offset in the minds of many by the terrifying events surrounding the Three Mile Island, Chernobyl, and Fukushima facilities, the last of which was created by the combination of a major earthquake and a tsunami in 2011.

Despite the mixed benefits and risks associated with nuclear energy, continued exploration of the world of nuclear physics will continue. Researchers have only discovered a small percentage of the presumed nuclides and isotopes that exist, and they are actively pursuing the discovery of new subatomic particles and their respective elements. New supercollider facilities, such as the LHC in Switzerland, are being used for a wide range of experiments on the dynamics of subatomic particles, including research into quarks—subatomic particles containing a fraction of the electrical charges held by other such particles—and space-based dark matter. Furthermore, many scientists are exploring new approaches to studying particle collisions, potentially leading to the discovery of new types of particles and more information about how these particles interact.

Bibliography

“Advantages of Fusion.” Iter, www.iter.org/sci/Fusion. Accessed 26 Sep. 2023.

Bern, Zvi, Lance J. Dixon, and David A. Kosower. “Loops, Trees and the Search for New Physics.” Scientific American 306.5 (2012): 35–41.

Jamieson, Valerie, and Richard Webb. “There’s a Particle for That.” New Scientist 17 Mar. 2012: 32–36.

“Nuclear Physics: Exploring the Heart of the Matter.” National Research Council, 2013, nap.nationalacademies.org/read/13438/chapter/1. Accessed 26 Sep. 2023.

Walker, Phil. “The Atomic Nucleus.” New Scientist 1 Oct. 2011: 1–8.

“What is a Semiconductor?” Semiconductor Industry Association, www.semiconductors.org/semiconductors-101/what-is-a-semiconductor/. Accessed 26 Sep. 2023.

About the Author

Michael P. Auerbach has over nineteen years of professional experience in public policy and administration, business and economic development, and political science. He is a 1993 graduate of Wittenberg University and a 1999 graduate of the Boston College Graduate School of Arts and Sciences. He is a veteran of state and federal government, having worked for seven years in the Massachusetts legislature and four years as a federal government contractor. He has written on a wide range of topics, including the environment, health care, international relations, and history.