LBNL, Berkeley, California, USA
One of the concepts for the next generation of linac-driven FELs is a cw superconducting linac driving an electron beam with MHz repetition rates. The beam is then switched into an array of independently configurable FELs. The demand for high brightness beams and the high rep-rate presents a number of challenges for the instrumentation and diagnostics. The high rep-rate also presents opportunities for increased beam stability because of the ability for much higher sampling rates for beam-based feedbacks. In this paper, we present our plans for instrumentation and diagnostics for such a machine.
LBNL, Berkeley, California, USA
CERN, Geneva, Switzerland
SLAC, Menlo Park, California, USA
Fermilab, Batavia, USA
ESS, Lund, Sweden
BNL, Upton, Long Island, New York, USA
The BRAN Ionization Chambers installed at the IP1 and IP5 Interaction Points of the LHC provide a relative measurement of the total and bunch-by-bunch luminosities. This information, combined with the logged bunch charges from a fast BCT monitor, offers the possibility of evaluating the Interaction Area in collision for each of the colliding bunch pairs and monitor its time evolution. A Graphic User Interface (GUI) has been implemented to display the interaction area of the proton bunches interacting in IP1 and IP5 during each of the Physics Runs in the attempt of displaying the contribution to the Luminosity time decay originating from possible emittance blow-up when operating the Accelerator close to the beam-beam limit. Early results confirm the ability to characterize the bunch by bunch emittance behavior during the store and study possible differences among bunches in the same fill.
LBNL, Berkeley, California, USA
One of the concepts for the next generation of linac-driven FELs is a cw superconducting linac driving an electron beam with MHz repetition rates. One of the challenges for next generation FELs is improve the shot-to-shot stability of the energy, charge, peak current, and timing jitter of the electron beam. The use of a cw RF system with MHz beam repetition rates presents an opportunity to use broadband feedback to stabilize the beam parameters. To understand the performance of such a feedback system, we are are developing a dynamic feedback model of the machine with a focus on the longitudinal beam properties. The model is being developed as an extension of the LITrack code and will include the dynamics of the beam-cavity interaction, RF feedback, beam-based feedback, and multibunch effects. In this paper, we will present the status of this model along with results.
LBNL, Berkeley, California, USA
INFN/LNF, Frascati (Roma), Italy
The LHC luminosity upgrade currently being planned at CERN depends in large measure on a successful upgrade of its injectors chain. In particular the storing of higher currents in the SPS presents a significant challenge from the point of view of the beam stability. Electron cloud driven and transverse mode-coupled instabilities can disrupt the stored beam to the point of making injection in the LHC impossible. These types of instabilities are characterized by fast growth times and substantial spectral components at high frequency. Therefore a key aspect of any feedback system capable of effectively controlling the instability growth is the development of a suitable kicker with a high frequency response. In this paper we investigate the technologies available for such a kicker and identify a possible solution to be implemented on the SPS. By combining a lower frequency stripline kicker with a high frequency module, such as a damped cavity or a slotted waveguide, it would be possible to provide shunt impedances around 1000 Ω on a bandwidth from DC to 1 GHz. The basic parameters and limits of such a solution are discussed.
LBNL, Berkeley, California, USA
LBNL is developing design concepts for a multi-beamline soft x-ray FEL array powered by a superconducting linear accelerator, operating with a high bunch repetition rate of approximately one MHz. The cw superconducting linear accelerator is supplied by an injector based on a high-brightness, high-repetition-rate photocathode electron gun. Electron bunches are distributed from the linac to the array of independently configurable FEL beamlines with nominal bunch rates up to 100 kHz in each FEL, and with even pulse spacing. Individual FELs may be configured for different modes of operation, and each may produce high peak and average brightness x-rays with a flexible pulse format, and with pulse durations ranging from sub-femtoseconds to hundreds of femtoseconds. In this paper we describe conceptual design studies and optimizations. We describe recent developments in the design and performance parameters, and progress in R&D activities.