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Physics of Beams; Accelerator Technology
- Cornell Laboratory for Accelerator-based Sciences and Education (CLASSE)
- Laboratory for Elementary-Particle Physics (LEPP)
The Physics of Beams is the study of accelerated beams as a special state of matter. It has many applications in particle accelerators, spectrometers, electron microscopes, and lithographic devices. These instruments have become so complex that an empirical approach to properties of the particle beams is by no means sufficient and a detailed theoretical understanding is necessary. Historically it has proved fruitful that studies in beam physics have been performed in the context of projects that developed or built one of these instruments, and I have worked on several such projects. Since 2016, I have been Cornell’s Principle Investigator in charge of building CBETA in a collaboration with Brookhaven National Laboratory; it is a new kind of accelerator at Cornell’s Wilson Laboratory, a 4-turn Energy Recovery Linac (ERL) and a prototyping facility for parts of a large scale Electron-Ion Collider, which is likely to be the US’ next large particle accelerator. My group has constructed many technical components needed for such accelerators and designed a large-scale hard X-ray light source based on an ERL. Before arriving at Cornell, I worked on the 4 mile circular accelerator HERA in Hamburg, where I contributed to the understanding of the non-linear dynamics and long term stability of the stored particles, of polarization dynamics, and of space charge forces acting from one particle beam to another. What was learned has been published as a book by Springer, High Energy Polarized Proton Beams, a modern view. Polarized beam studies are important, for example at the US’s largest nuclear physics collider RHIC. The particle beams in all these accelerators have interesting nonlinear beam dynamics, multi bunch instabilities, space charge within a tightly focused beam, the creation of synchrotron light, and the back-reaction of coherently emitted light on the beam. ERLs are a new type of accelerator where the energy of a spent beam is re-used to accelerate new beam. Charged particle accelerators have become an essential tool in today's investigation of all types of materials, from airplane wings to cell membranes and from pollutants in leaves to matter under earth-core pressures. Technical components that have been developed at Cornell for these applications are now being used in the development of LCLS-II, a new x-ray laser at SLAC. And my group has also had a collaboration with ASML, a company for industrial lithography of computer chips, on the use of ERLs for chip production.
Accelerator Technology describes the technology used to accelerate large currents of tightly focused beams to high energies. These beams are then used to study elementary particles, to produce synchrotron light for analysis in biophysics, in crystallography, in surface physics, or in the material sciences, for cancer therapy, and for a variety of other applications. Studies with synchrotron light are currently performed by CHESS at Cornell. The technology involved in accelerators is very rich and I am currently mostly interested in the technology required for the Electron Ion Collider, in particular in components that are tested by CBETA, the 4-turn ERL we are constructing at Cornell, where the energy of accelerated particles is recovered in superconducting cavities in order to accelerate new particles. These particles are produced in a photo cathode electron gun that involves a very complex system of lasers. Subsequently they are accelerated in a high-power superconducting radio-frequency (SRF) linac that has been constructed in my group. This system holds world records in beam brightness and in current through an SRF linac. A second SRF linac was constructed that couples only little RF power to the beam, because it is optimized for ERLs where the power is supplied by a decelerating beam. This complete accelerating system from the electron source through the ERL linac and its permanent magnet return loop recovered the beam’s energy for the firs time in June 2019. We are now completing the world’s first multi-turn ERL and will store all beam of 4-different energies in one beam pipe simultaneously. This is first-of-its kind technology.
William Lou (Charged-particle optics in FFAGs and ERLs)
Nilanjan Banerjee (Stabilization of microphonic detuning of RF frequencies)
Thursday 11am, CBETA Design and Commissioning Meeting, 374 Wilson Lab
Further information can be obtained by contacting research associates at Wilson Laboratory and at https://www.classe.cornell.edu/Research/ERL/WebHome.html.
Graduate and undergraduate students interested in beam physics and the application of particle accelerators are encouraged to join this group. There are many opportunities for student involvement.