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Georg Hoffstaetter


Newman, Floyd R. Laboratory, Room 318
318 Newman Lab

Educational Background

Diplom, 1991, Darmstadt University of Technology, Germany. M.S., 1992, and Ph.D., 1994, as NSCL Fellow and Natural Science Fellow, Michigan State University. Dr. habil. (doctor habilitatus), 2000, Darmstadt University of Technology. Research Associate, Deutsches Elektornen-Synchrotron (DESY), Hamburg, Germany, 1994-1996. Faculty, Darmstadt University of Technology, 1996-1998. Accelerator Physicist, DESY, 1998-2002. Associate Professor, Cornell University, 2002-2008. Professor, Cornell University, 2008-present,.Fellow, German National Merrit Foundation.



Physics of Beams; Accelerator Technology


  • Physics

Graduate Fields

  • Physics


  • 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, 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. I am coordinating the accelerator science work for an Energy Recovery Linear Accelerator (ERL) Project at Cornell where my interests concern 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. One large application that my group has developed will constitute a novel x-ray light source with beams significantly better than those of the world's most advanced facilities. X-ray beams from 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. The development of the ERL, envisioned and invented at Cornell, that provides more brilliant beams in shorter pulses will move such investigations to new frontiers. Technical components that have been developed at Cornell for this application 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. Currently we are constructing CBETA, an ERL as a prototyping facility for the 4km long nuclear physics accelerator eRHIC in collaboration with Brookhaven National Laboratory.

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 Cornell ERL 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 was operated for the first time in May 2017. It will be built into the world’s first multi-turn ERL by a return loop built of permanent magnets in an FFAG arrangement that allows to store all beam of 4-different energies in one beam pipe simultaneously. Also a first-of-its kind technology.

Graduate Students
William Liu (Charged-particle optics in FFAGs and ERLs)
Nilanjan Banerjee (Stabilization of microphonic detuning of RF frequencies)

Group meetings:
Thursday 4pm, CBETA Design and Commissioning Meeting, 374 Wilson Lab

Further information can be obtained by contacting research associates at Wilson Laboratory and at

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.