What is Elementary Particle Physics Good for?
Selcuk Cihangir, Fermilab
What is Elementary Particle Physics good for? This question has been asked to me and to other physicists in the field on numerous occasions. It has been asked by friends, students, talk show hosts, as well as politicians. We tried to give an answer. Recently there have been concerted efforts to document the economical and sociological impact of basic research in elementary particle physics. There have been articles written and conferences given about the subject [1]. With this article, I attempt to summarize all these efforts by highlighting the contributions this particular field of science has made to our civilization.
Throughout human history, research was done to better understand the universe we live in. Aims of Copernicus, Kepler or Galileo in studying the Heavens were not one day to land on the moon, or to create NASA and a Space Industry to employ thousands of people. They wanted to know “How” and “Why”! That same intellectual curiosity stimulates the hard and delicate work to understand what constitutes the universe, what is its origin, and why it behaves the way it does. It is human nature. We want to know. If James Clerk Maxwell had pondered the use of his work leading to “Maxwell’s Equations”[2], where would our civilization be today? His equations gave humanity an understanding that the light was electric and magnetic waves oscillating together in space and it did not even have to be visible. What followed were many other discoveries about the nature of light and electromagnetism, leading to inventions of radio, television, microwaves, radars, x-rays, telecommunications, and other technologies that we cannot imagine living without. Civilization as we know it today would not exist without knowing these equations. It has been told that Maxwell did not publish his equations for a long time because he was not sure if they were correct. And therefore he is blamed by some for delaying the advancement of civilization for that many years.
Elementary particle physicists, while discovering seemingly useless particles, such as mesons, neutrinos, muons and quarks, have been laying the groundwork for much technological advancement. Here are some of the technologies that benefitted from the research and development in this field:
1. Cancer Treatment
Starting in early 1950’s some forms of cancer are being treated by X-ray radiation generated at linear accelerators for particle physics experiments. The side effects are serious. The radiation destroys the surrounding tissues in addition to the tumor, as well as the tissues along the path to the tumor and on the path exiting the body. As a result, especially later in life on young patients, failures at other organs, disfiguration, and even lower IQ in case of brain tumor treatment, are common observations.
In a 1946 paper [3], Robert R. Wilson, a Harvard physicist at the time, and who, in 1967, is to be the founding director of Fermi National Accelerator Laboratory (Fermilab), an elementary particle physics research laboratory in Batavia, IL, proposed the use of protons for cancer treatment. He explained that protons did most of their destruction just before they were stopped in the body and, how far they penetrated into the body depended on their energy (their speed, in a way). Therefore, by controlling the energy of the protons generated at a particle physics accelerator, we could penetrate into a desired depth of the body where the tumor was located, while causing minor destruction along the way.
First proton treatments took place in 1954 in Lawrence Berkeley Laboratory, an elementary particle physics research center in California. But not until the early 1980’s an attempt was made to commercialize this method of cancer treatment. Even then, the medical technology firms did not want to commit to this technology because it was “financially not worth it”. They turned down an offer by Loma Linda University Medical Center, Loma Linda, California to build a proton accelerator for a facility to treat cancer. The university then turned to Fermilab, and Fermilab built a synchrotron accelerator which could produce a proton beam up to 250 MeV (million electron volts) in energy and could penetrate 3 to 38 cm into a body [4]. It was only 20 feet in diameter and 5 feet tall. It was designed, built and tested at Fermilab by Fermilab staff. The US Department of Energy funded the project. Loma Linda treated its first patient in October 1990.
Today there are more of these proton treatment facilities around the world. More than 40,000 patients have been treated in these facilities since 1990. Hospitals can buy the components from companies specializing on the technology. Scientists are researching to determine the optimal proton dose and energy for various types of cancer treatments. Studies are made and ideas are entertained at various accelerator laboratories to lower the size of the machines by using superconducting magnets (another technology elementary particle physics helped to advance), to energize the protons faster and in cheaper ways, and to focus them to smaller targeted regions than ever before to further minimize any collateral damage.
2. Magnetic Resonance Imaging (MRI)
Another medical wonder, MRI, has its roots and development directly associated with particle physics research. The technology is based on the behavior of the hydrogen atoms in the presence of a strong magnetic field. These atoms align themselves to the field like compass needles in Earth’s magnetic field. When they are pulsed by a RF (radio frequency) energy source, they spin around the direction of the magnetic field. Upon turning the RF off, the absorbed energy is released. Detection of this energy in the presence of an oscillating second field, which is localized to certain part of an object (human body, for instance), and the fact that different materials (tissues in medical case) release the energy in specific rates, are the essence of the imaging technique. First such an image of a material was obtained in 1973 by Paul Lauterbur [5]. The first human body image was produced in 1977.
The technique is used to image the human body since the human body is mostly water and water molecules contain two hydrogen atoms. But strong, 0.5-2.0 Tesla, magnets are needed in a small area and with affordable cost. Within a year after Lauterbur’s imaging technique was discovered, in 1974 Fermilab initiated efforts to build the Tevatron, the world’s largest particle accelerator. Strong, stable and controllable magnets were needed for it, also.
There existed, at the time, electromagnets that were built by wires wrapped in a cylindrical coil shape. Most of the electric energy, however, was lost as heat on the wires, elevating the cost of the operation if strong magnetic field was desired. The solution for both MRI and the Tevatron was a phenomenon called superconductivity. The world knew about the superconductivity: electric current on wires made with certain metal alloys, such as niobium-titanium, and cooled down to liquid helium temperature would flow with almost no energy loss to heat. Fermilab physicists and engineers developed and built coils with superconducting wires in large scales needed for the Tevatron. To facilitate the production of superconducting metal alloys in the scale MRI required, Fermilab provided the material and the knowledge to private companies. This further led to commercial developments in the superconducting technology to build affordable MRI machines. In present day there are more than 25,000 MRI machines in hospitals and medical centers, being used to produce images of soft tissues of human body to diagnose and treat illnesses.
3. Ion Implantation
Use of particle accelerators yielded to a technology called ion implantation where accelerated ions were made to penetrate into material. Ion implantation revolutionized the microchip industry. It made it possible to introduce controlled amount of metallic elements on the surface or near the surface of semiconductors. Manufacturers today use ion implantation for almost all doping in integrated circuits which are the components of consumer electronic products such as cell phones, flat screen TV’s, personal computers.
Ion implantation is also the technology for modifying surface properties of materials. It is like a coating process without the addition of a layer on the surface. Highly energetic beams of ions are used to modify surface structure of materials at low temperature so that the component dimensions and material properties are not adversely affected. Surface properties such as hardness and wear resistance, can be improved and friction is reduced. The process can extend the lifetimes of cutting and punching tools, as well as the durability of automobile tires. In medical field, the application of this process improves the life span and functionality of the artificial human body parts, such as hip replacement and orthopedic implants.
4. Food Irradiation
It is still controversial to this date, but food irradiation is a method to delay its spoilage. It is a technology to eliminate pathogens that naturally exist in food. Bacteria that cause salmonella food poisoning, for instance, can be destroyed to save lives. In its purpose, irradiation of food is similar to conventional pasteurization but it does not rely on heat as pasteurization does. Therefore the technique is sometimes called “cold pasteurization”.
The ionization energy, in some form of elementary particles or created by them, kills the microbes. The energy breaks their molecular bonds, causing them to die or not being able to grow and multiply. One source of such energy is Cobalt-60 which emits gamma rays (photons) while decaying into another element. It is commonly used for food irradiation. It has a short life time and treatment of food is relatively slow. Cesium-137 is another gamma source used for food irradiation.
The other method of irradiation is the use electron beam. Electrons are generated and energized in a linear accelerator to form a beam. The beam can be turned on and off at will and there is no radioactive waste. But the penetration depth into the food is not adequate for most purposes. The facilities are complicated and costly to operate. In order to increase the penetration depth, the electrons need to be converted to x-rays, another form of ionization energy, by using a metal target.
Acceleration technology and knowledge created by the research in elementary particle physics can be utilized to overcome the obstacles and difficulties faced by the food irradiation facilities. The same knowledge may help to alleviate the fear associated with the negative connotation the word “radiation” brings to minds of general population. Growing human population and increase in food consumption emphasize the need of preserving the food for long period of times by delaying or even eliminating its spoilage.
5. World Wide Web
A less known fact is the contribution of particle physics to the development of the Internet and the World Wide Web (Web). The Internet, a global data communications system, is a hardware and software infrastructure that connects computers and provides communications between them. It existed in some form since 1958 and was used by the US Air Force and some other organizations. The Web, on the other hand, is one of the services communicated via the Internet. A collection of documents and resources that are linked and interconnected by systems and protocols constitutes the Web.
Tim Berners-Lee at the European Organization for Nuclear Research (CERN), an elementary particle physics research laboratory in Switzerland, invented both the HTML markup language and the HTTP protocol which are used to request and transmit web pages between web servers and web browsers, as we know today. Elementary particle physicists from around the world who were conducting experiments at CERN, needed to share data and information without a common computer or software. His proposal in 1989 addressing to this need of physicists paved the way to use of Internet in form of Web.
The influence of the Web and all the related technologies in today’s way of life is no doubt, very significant. One cannot argue against the opinion that if particle physics and CERN had not played the role they did, the Web probably would have been invented someday for some other reasons. But it is fair to say that the need of particle physicists to quickly access and share data was a catalyst for its invention. Its first use by the particle physicists pushed it forward to the advancement we have today. According to some, particle physics may have accelerated the Web’s introduction by at least ten years. By looking ten years back, one can appreciate the difference a decade has made in the development of the Web, and during the years ensued, the contributions of this technology into the way we communicate, and the way we store, access and process data.
6. Social Contributions
Elementary particle physics research has always pushed the limits of existing technologies. In present days, experiments in this field are so complicated and sophisticated that it takes thousands of people and 10 – 15 years to plan, to design and to build one. Therefore scientists and engineers have to think of and envision technologies beyond the present generations. Otherwise, the project would be obsolete before it even started. Often the requirements of the experiments in terms of measurement speed and accuracy are well beyond the existing capabilities. Seeking for that level of improvement challenged the technologies and their originators to surge ahead in unconventional territories. Often the physicists themselves were the originators.
Laboratories, such as Fermilab, that provide facilities to do research in elementary particle physics, contribute to local and national, and in some cases international business by outsourcing the manufacturing work and by employing people living in those communities. They train high school students and teachers in science. They provide summer internship to national and international college students. They open public forums to educate communities in science matters.
Graduates in this field are relentlessly hard workers and are highly trained in electronics, computer programming and management, statistics and data analysis, among other disciplines. Most of them join the work force in high tech companies, financial institutions, medical facilities and others, contributing to technological and scientific advancements with their creativity and skills.
There are other direct and indirect benefits of the research in elementary particle physics worth mentioning. One is the vacuum technology. Beams at the particle accelerators travel in almost absolute vacuum to prevent diversion in their paths. Vacuum technology, developed at these laboratories to meet their stringent requirements, is utilized by many other commercial technology centers. Similarly, the RF (radio frequency) technology needed to accelerate the particle beams, is advanced and perfected by the particle physics laboratories and is used by many commercial establishments. Research in this field pushed the frontier for ultra sensitive detectors, of light for instance, which are essential part of many research and applications in medicine and in other fields of science and technology. Many mathematical methods and tools, such as Monte Carlo modeling of any device, procedure and even finance, are invented and developed as part of research in elementary particle physics.
These are all anecdotal evidences to benefits of elementary particle physics. A comprehensive study and a systematic evaluation by an independent agency are needed. It is absolutely imperative that the science community makes the case that an investment in basic research, such as elementary particle physics, produces both short term benefits to the society in many profound ways, and scientific results with long term benefits.
References:
[1] A detailed case is presented in: Symmetry, Volume 05, Issue 06, December 2008.
[2] James Clerk Maxwell’s equations, in their modern form of four partial differential equations, first appeared in his textbook A Treatise on Electricity and Magnetism in 1873.
[3] "Radiological Use of Fast Protons", Radiology 47 (1946) pp. 487-491.
[4] More information about the Center and the proton therapy can be found at: www.protons.com/proton-therapy/proton-technology.html
[5] "Image Formation by Induced Local Interactions: Examples Employing Nuclear Magnetic Resonance", Nature 242 (1973), 190-191.
The proton accelerator built at Fermilab for Loma Linda Medical Center, before it was shipped to Loma Linda