SLAC, Menlo Park, California, USA
CERN, Geneva, Switzerland
Electron cloud and transverse mode coupled-bunch instabilities (TMCI) limit the bunch intensity in the CERN SPS. Intra-bunch fast feedback systems are a possible method to control these effects. This paper presents experimental measurements of single-bunch motion in the SPS driven by a GHz bandwidth vertical excitation system*. The primary goal is to quantify the change in internal bunch dynamics as instability thresholds are approached, and quantify the frequencies of internal modes as Ecloud effects become significant. The beam response is sampled at 20 GS/sec. in response to arbitrary excitation patterns, with data in 2011 taken at 3 bunch intensities. We show the excitation of barycentric, head-tail and higher vertical modes. The beam motion is analyzed in the time domain, via animated presentations of the sampled vertical signals, and in the frequency domain, via spectrograms showing the modal frequencies vs. time. The demonstration of the excitation of selected internal modes is a significant step in development of the feedback control techniques.
* "A 4 GS/Sec. Synchronized Vertical Excitation System for SPS Studies - Steps Towards Wideband Feedback," these proceedings.
Fermilab, Batavia, USA
CLASSE, Ithaca, New York, USA
SLAC, Menlo Park, California, USA
CLASSE, Ithaca, New York, USA
ANL, Argonne, USA
LBNL, Berkeley, California, USA
INFN/LNF, Frascati (Roma), Italy
SLAC, Menlo Park, California, USA
We report modeling results for electron cloud buildup in the ILC damping ring lattice design. Updated optics, wiggler magnet, and vacuum chamber designs have recently been developed for the 5-GeV, 3.2-km racetrack layout. An analysis of the synchrotron radiation profile around the ring has been performed, including the effect of photon scattering on the interior of the vacuum chamber. Operational implications of the resulting electron cloud buildup will be discussed.
SLAC, Menlo Park, California, USA
End Station A Test Beam (ESTB) is a test beam line at SLAC in the large End Station A (ESA) experimental hall. It uses a fraction of the bunches of the 14.7 GeV electron beam from the Linac Coherent Light Source (LCLS). ESTB provides a unique test beam for particle and particle astrophysics detector research, accelerator instrumentation and accelerator R&D, development of radiation-hard detectors, and material damage studies. It has exceptionally clean and well-defined secondary electron beams, a huge experimental area and good existing conventional facilities. Recently, a new kicker magnet has been installed to divert 5 Hz of the LCLS low energy beam into the A-line. The full installation will include 4 kicker magnets to allow diversion of high energy beams. A new beam dump and a new Personnel Protection System (PPS) have been built in ESA. In stage II, a secondary hadron target will be able to produce pions up to about 12 GeV/c at 1 particle/pulse. This paper reports the progress on ESTB construction and commissioning.
CERN, Geneva, Switzerland
IFIC, Valencia, Spain
KIT, Karlsruhe, Germany
ASCo, Clayton, Victoria, Australia
BINP SB RAS, Novosibirsk, Russia
Cockcroft Institute, Warrington, Cheshire, United Kingdom
EPFL, Lausanne, Switzerland
CLASSE, Ithaca, New York, USA
SLAC, Menlo Park, California, USA
The University of Melbourne, Melbourne, Australia
JUAS, Archamps, France
Fermilab, Batavia, USA
CLASSE, Ithaca, New York, USA
CalPoly, San Luis Obispo, California, USA
CMU, Pittsburgh, Pennsylvania, USA
KEK, Ibaraki, Japan
LBNL, Berkeley, California, USA
SLAC, Menlo Park, California, USA
Electron clouds can adversely affect the performance of accelerators, and are of particular concern for the design of future low emittance damping rings. Studies of the impact of electron clouds on the dynamics of bunch trains in CESR have been a major focus of the CESR Test Accelerator program. In this paper, we report measurements of coherent tune shifts, emittance growth, and coherent instabilities carried out using a variety of bunch currents, train configurations, beam energies, and transverse emittances, similar to the design values for the ILC damping rings. We also compare the measurements with simulations which model the effects of electron clouds on beam dynamics, to extract simulation model parameters and to quantify the validity of the simulation codes.
SLAC, Menlo Park, California, USA
CERN, Geneva, Switzerland
INFN/LNF, Frascati (Roma), Italy
CLASSE, Ithaca, New York, USA
The beam tracking codes C-MAD and HEAD-TAIL have been enhanced to include a detailed model of a single-bunch feedback system. Such a system is under development to mitigate the electron cloud and the transverse mode coupling instability (TMCI) in the SPS and LHC at CERN. This paper presents the model of the feedback sub-systems: receiver, processing channel, filter, amplifier and kicker, which takes into account the frequency response, noise, mismatching and technological limits. With a realistic model of the hardware, it is possible to study the prototypes installed in the SPS and design a novel feedback system. The C-MAD code, which is parallel and optimized for speed, now also includes radiation damping and quantum excitation and a detailed model of Intra-Beam Scattering (IBS) based on the Zenkevich-Bolshakov algorithm, to investigate the IBS during damping and its effect on the beam distribution, especially the beam tails, that analytical methods cannot investigate. Intra-beam scattering is a limiting factor for ultra-low emittance rings such as CLIC and Super-B.
SLAC, Menlo Park, California, USA