Jefferson Lab
and the
International
Linear Collider
The International Linear Collider (ILC) is the dream of the international high energy and particle physics community: two huge linear accelerators, one for electrons and one for positrons, positioned and pointed so that their extremely high energy beams intersect.
It is a commonplace that physicists in this field now use energies so high that the particles are traveling very close to the speed of light. To put it into perspective, the ‘high energy’ electrons used at JLab for the nuclear physics program are traveling so fast that if we started a race between those electrons and a light beam from the surface of the sun, and gave the electrons a 1 millimeter head start, the light beam wouldn’t catch up until the two of them had traveled about 60 miles. For electrons at the speed of the ILC, with the same head start, the light beam would only catch up to the electron after traveling about twice the distance from the earth to the moon.
The debris created by collisions between individual electrons and positrons at the crossing point will be examined with enormous detectors, looking for clues to help resolve the remaining puzzles in the rules that govern the world of matter: the universe around us.
This search is truly one to spark the imagination, and the scientists at JLab are following the evolution of the ILC with intense interest. But the business of JLab is nuclear, not high energy physics, so we’ll be watching the ILC physics program from the sidelines. Those of us who are engaged in maintaining and extending the core technology that supports physics at JLab – radiofrequency superconductivity – have another interest, because the proponents of the ILC have decided to use our technology in constructing their huge linear accelerators.
RF Superconductivity and the ILC
Achieving the very high energies of the ILC without having to build a very long linac, the proponents plan to build accelerating modules capable of putting more energy into the electron and positron beams per meter of length than was achieved for CEBAF: nearly 6 times more.
Achieving this without needing a truly gargantuan liquid helium refrigerator will require these devices to be about 4 times as efficient at converting rf power to accelerating field, at the higher operating voltages. To be quantitative, the accelerating gradient (E acc) will be more than 28 MV/m, and may be as much as 35 MV/m, with Q 0 > 10 10.
There is an international consensus that these specifications are achievable in production, using processes that have been developed and demonstrated in small quantities at laboratories around the world. There is agreement that the main challenge facing SRF experts around the world is transferring the knowledge of these processes to industry, so that the large number of accelerating modules needed can be built at minimum cost.
The search for still higher accelerating gradients or Q 0 is still worth pursuing, since an unexpected and substantial early success could have a dramatic impact on project cost, but this is relegated to a lower priority.
A Role for JLab
As the pre-eminent US center for production of superconducting accelerator systems, JLab clearly has a major role to play in the Linear Collider. The tasks are several and serial:
- demonstrate a command of the processes needed to achieve the level of performance needed for the ILC
- fine tune those processes and system design so they can be built in industry at minimum cost
- demonstrate the adequacy of design and processes by building and testing a small number of units
- assist industry in achieving production goals
- assist the ILC laboratory in the commissioning of its linacs.
Cost-effective production of superconducting modules is only likely to be achieved if the technology can be mastered by industry. Technology transfer at each of the steps listed above is essential to success. Equally essential to success is the enlistment of all institutions in the US with expertise in SRF, whether national labs, universities or industry. JLab is working hard to identify the means by which a successful national collaboration can be constructed to support industrialization of this technology.
The plan for carrying out these tasks has been in development for a little more than a year. Several documents giving some perspective on the evolution of this plan are available.
- A poster presentation, created by Dr. Charles E. Reece, for the International Technology Recommendation Panel (ITRP), a body created by the International Committee for Future Accelerators to make a recommendation on the technology to be used for the construction of the ILC main accelerators. This is the group that made the recommendation for a superconducting solution, accepted by the world community.
- A presentation by the Director of Jefferson Lab, Dr. Christoph Leemann, to the ITRP at its meeting at the California Institute of Technology on June 28, 2004.
- A presentation by Dr. L. Warren Funk, Director of JLab’s Institute for Superconducting RF Science & Technology at the Victoria, BC, Workshop on the Linear Collider, July 28-31, 2004.
- Another presentation by Funk, at the First International Linear Collider Workshop at the Laboratory for High Energy Physics (KEK) in Japan, November 13-15, 2004.