Berlin Energy Recovery Linac Prototype (bERLinPro)

ERLs hold the promise of becoming the future backbone of modern accelerator facilities, satisfying the needs of the user community in applied science and fundamental research.They combine the efficiency advantage of storage rings with the improved beam quality achievable in a linac.Thus the ERL offers two important properties: an electron beam having high-brightness and high-power capabilities simultanously.

The basic idea of the ERL is to circumvent the "storage ring" like equilibrium state, but maitain the beam quality delivered by the source. This means, the beam must be discarded before the equilibrium is established. A single-pass linear accelerator (linac) represents the most extreme example of such a device. In order to reach beam currents in the 100mA range superconducting RF (SRF) cavities are the enabling technology that allows to accelerate a Continuous Wave (CW) beam. Due to the extreme beam power (Mega- to Gigawatt), after usage the beam is redirected through the accelerating structures to recover most of the energy invested.

The beam, generated by an ERL has the potential to be applied to a large number of uses, notably particle collider, compact Compton sources and the next generation of synchrotron light sources. With respect to the latter ERLs provide radiation with characteristics, that cannot be matched by third-generation storage rings

  •  Average brilliance two to three orders of magnitude higher
  •  Pulse lengths that are at least two orders of magnitude shorter (some 10 fs)
  •  Significantly higher coherence fraction
  •  Great flexibility to tune the beam properties and repetition rate to the user requirements.
  •  And critically, ERLs can generate a wide spectrum of radiation for a true multiuser facility.

The Future of Synchrotron Light Sources

Despite of the invaluable success of synchrotron radiation in scientific research - so far,  researchers were limited to investigations of static structural properties of matter. Examples are the electron distribution in an atom or a molecule’s structural analysis – both in its static ground state. Unfortunately this alone is not enough to tackle the urgent and major challenges of today’s society with respect to energy, environment , health or transport.

Understanding the dynamics of ultrafast processes will become an essential necessity.

Only if we are able to investigate the dynamics of these processes while determine the probe’s  structure with the highest resolution , the knowledge to compose completely new , "functional materials " such as new energy storage , thin-film solar cells and materials for regenerative medicine to solving the major challenges developing our society ( " Grand Challenges ")  will be gained.

In the future, therefore, the dynamics of microscopic, molecular, atomic and subatomic processes must be analyzed, on extremely short time scales down to the femtosecond range. Single or even better sequences of snap-shots series of ultrafast processes must become available to investigate the time dependency of structural material transformations. With this knowledge a fully understanding of the functioning of materials will be possible. The results obtained in recent years synchrotron radiation sources show the way that must be pursued in the development of these facilities. Light sources based on the ERL technology could meet the increasing demands of a growing user community with a focus on the study of dynamic effects.


For ERLs, the demands placed on the electron source, the SRF linac, and the beam transport are severe due to the required extreme beam quality, high current and the CW operation. Ultimately, the technology and concepts have to be put to the test in an ERL test facility. To this end, HZB is building bERLinPro.

bERLinPro is designed to develop and to demonstrate the CW LINAC technology and expertise required to drive next-generation accelerator facilities that are based on ERL principle.

→ BerLinPro Website