High energy physics research is strongly dependent on the use of high-energy particle beams provided by charged particle accelerators, storage rings and the associated detectors. Operating in the extreme domains that are essential for successful particle physics research demands very specialized technology that takes substantial time and expense to invent, design, build, maintain and upgrade. The DOE HEP supports a very successful program of technology R&D that has ensured the availability of the most technically advanced research facilities and a world-class U.S. HEP program.
Scientists at SLAC and LBL, for example, have made significant progress on alternate mechanisms of charged particle acceleration. Current experiments are studying the potential feasibility of both particle-driven and laser-driven plasma wakefield accelerators. These technologies could potentially double the energy of a linear accelerator beam in only a few meters, and research on these alternate methods of acceleration will continue.
In many cases the same technologies that scientists develop in this R&D subprogram find applications in synchrotron light sources, intense neutron sources, very short-pulse, bright electron beams and computational software for particle beam optics design. This functionality makes these technologies useful in nuclear physics, materials science, chemistry, medicine and industry. Accelerators are widely used for medical therapy and diagnostics, not to mention preparation of radionuclides used in medical treatment facilities, electronics and food industries. Homeland security applications are also a new application.
The R&D program for the proposed International Linear Collider, for example, emphasizes technological developments that have a broad range of scientific applications. The ILC will use superconducting radiofrequency cavities to accelerate the electrons and positrons to high energies. Although SCRF technology has been studied for decades, scientists still consider it to be new, with ILC collaborators making significant improvements and cost savings as they develop it for use in particle accelerators.
Radiofrequency cavities are used to boost the speeds of particles in accelerators. The accelerator fills each cavity with very strong electrical fields that oscillate, producing pulses of energy that push the particles along. When chilled to near absolute zero, the cavity’s superconducting metal walls conduct electric current with almost no loss of energy. This efficiency makes the technology appealing.
Higher accelerator fields and improved efficiency can translate into smaller and cheaper packages. The potential applications of SCRF are manifold and currently under discussion.
One beneficiary is the X-ray free electron laser. These X-rays are generated by a beam of electrons that passes through an oscillating magnetic field, which then produce super-fast pulses of X-rays that can be used to record chemical reactions and molecular processes in action. Some of these lasers could use superconducting cavities to accelerate the electrons. By using free-electron lasers, scientists may be able to see how a drug changes the molecular structure of proteins in real time, providing a unique tool to create pharmaceuticals that can fit the shape of human biological molecules.
Changing nuclear waste into a more stable form that is less hazardous is another ambitious topic of discussion. A high-powered proton beam from a superconducting linear accelerator may make it possible to extract nearly all the available energy from nuclear waste, leaving virtually no plutonium behind. The resulting residue would require special storage for a few hundred years, compared with a few hundred thousands years, greatly simplifying the engineering needed to store it safely.
Cargo scanning is also a potential application of SCRF technology. A high-power beam of gamma rays from a superconducting linear accelerator could probe a shipping container, exciting the atoms and nuclei inside. An advanced particle detector would measure the resulting emissions, revealing a three-dimensional shape of the objects inside, to spot contraband or nuclear weapons.
Practical uses of SCRF technology still require ample research, and scientists are continuing to discuss the potential applications with members of U.S. industry.