[en] Several possible scenarios of Energy Recovery Linac (ERL) beam optics design are investigated to support the low emittance high current CW electron beam needed to drive a new ERL based X-ray Source. It is shown by numerical simulations that sufficiently high multipass beam break-up (BBU) threshold current can be achieved in a straightforward one-pass one-linac ERL scenario. A simple guideline for choosing optimal linac and recirculating transport line optics is suggested to realize best possible BBU threshold current

[en] Storage rings have served well as x-ray sources, achieving continued increases in flux and brightness. While further improvements in performance may still be expected, the performance of these machines is circumscribed by radiation fluctuations and by the Touschek effect. The practical effect of the radiation fluctuations is to limit the minimum 6D emittance of the rings in general, particularly the bunch length. Through limiting the lifetime, the Touschek effect also limits the charge density in the bunches. These effects can be greatly ameliorated through use of a linac driver for the x-ray producing devices such as small gap undulators because the beam passes through only once and in a time short compared to the radiation equilibration time. In this case, the emittance is limited only by the source and the beam is thrown away after each pass so that radiation and collision effects are no longer relevant. By recovering the kinetic energy carried by the beam through use of the energy recovery principle in a superconducting linac, one can in principle support beam currents comparable to those of storage rings but with smaller emitting source area. These advantages permit the achieving of superior brilliance while giving great flexibility in bunch pattern and bunch length. The concept of a 5 - 7 GeV facility using this principle is described and parameter goals are given

[en] In recirculating accelerators, and in particular energy recovery linacs (ERLs), the maximum current has been limited by multipass, multibunch beam breakup (BBU), which occurs when the electron beam interacts with the higher-order modes (HOMs) of an accelerating cavity on the accelerating pass and again on the energy recovered pass. This effect is of particular concern in the design of modern high average current energy recovery accelerators utilizing superconducting RF technology. Experimental observations of the instability at the Jefferson Laboratory 10 kW Free-Electron Laser (FEL) are presented. Measurements of the threshold current for the instability are presented and compared to the predictions of several BBU simulation codes. With BBU posing a threat to high current beam operation in the FEL Driver, several suppression schemes were developed. These include direct damping of the dangerous HOMs and appropriately modifying the electron beam optics. Preliminary results of their effectiveness in raising the threshold current for stability are presented

[en] In recirculating accelerators, and in particular energy recovery linacs (ERLs), the maximum current can be limited by multipass, multibunch beam breakup (BBU), which occurs when the electron beam interacts with the higher-order modes (HOMs) of an accelerating cavity on the accelerating pass and again on the energy recovering pass. This effect is of particular concern in the design of modern high average current energy recovery accelerators utilizing superconducting RF technology. Experimental characterization and observations of the instability at the Jefferson Laboratory 10 kW Free Electron Laser (FEL) are presented. Measurements of the threshold current for the instability are made under a variety of beam conditions and compared to the predictions of several BBU simulation codes. This represents the first time in which the codes have been experimentally benchmarked. With BBU posing a threat to high current beam operation in the FEL Driver, several suppression schemes were developed

[en] Practically all synchrotron x-ray sources to data are based on the use of storage rings to produce the high current electron (or positron) beams needed for synchrotron radiation (SR). The ultimate limitations on the quality of the electron beam, which are directly reflected in many of the most important characteristics of the SR beams, arise from the physics of equilibrium processes fundamental to the operation of storage rings. It is possible to produce electron beams with superior characteristics for SR via photoinjected electron sources and high-energy linacs; however, the energy consumption of such machines is prohibitive. This limitation can be overcome by the use of an energy recovery linac (ERL), which involves configuring the electron-beam path to use the same superconducting linac as a decelerator of the electron beam after SR production, thereby recovering the beam energy for acceleration of new electrons. ERLs have the potential to produce SR beams with brilliance, coherence , time structure, and source size and shape which are superior to even the best third-generation storage ring sources, while maintaining flexible machine operation and competitive costs. Here, we describe a project to produce a hard x-ray ERL SR source at Cornell University, with emphasis on the characteristics, promise, and challenges of such an ERL machine

[en] Cornell University, in collaboration with Jefferson Lab, has proposed a novel X-ray source based on the energy recovery linac (ERL) concept [1, 2]. Such a source will exceed the brightness of third generation synchrotron light facilities and will also allow ultra short X-ray pulses and variable pulse formats, to enhance existing, and promote new applications in X-ray science

[en] Synchrotron radiation (SR) has become an essential and rapidly growing tool across the sciences and engineering. World-wide, about 70 SR sources are in various stages of operation, construction, or planning, representing a cumulative investment on many billions of dollars and serving a growing research community well in excess of 10,000 scientists. To date, all major SR x-ray facilities are based on electron (or positron) storage rings. Given the expected continued growth, importance and expense of SR sources, it is important to ask if there are alternatives to the storage ring SR source which offer advantages of capability or cost. A step in this direction is being taken by the SR community with the proposed developments of linac-based x-ray free-electron lasers (XFELs) utilizing the self-amplified spontaneous emission process (SASE). However, the versatility of modern developments in accelerator physics, as applied to synchrotron radiation, is not limited to storage rings or XFELs. New developments in laser driven photoinjectors and superconducting linac technology open new and exciting possibilities for novel SR-generating machines which offer extraordinary capabilities and promise to catalyze whole new areas of SR-based science