A bunch-by-bunch longitudinal feedback system has been designed and built o control coupled-bunch instabilities in the PEP-I1 machine. A prototype system has been installed at the Advanced Light Source at LBNL. Programmable DSPs allow longitudinal feedback processing in conjunction with data acquisition or instrumentation algorithms. Here we describe techniques developed for different beam and ...

Compensation of multi-bunch beam loading is of great importance in the main linac of the Compact Linear Collider (CLIC). The bunch-to-bunch energy variation has to stay below 1 part in 10. In CLIC, the RF power is obtained by decelerating a drive beam which is formed by merging a number of short bunch trains. A promising scheme for tackling beam loading in the main linac is based on varying the...

We derive analytical expressions for external fields of a charged relativistic bunch with a circular cross section. At distances far from the bunch, the field reduces to the relativistic modified Coulomb form and in the near region, reproduce the external fields of a continuous beam. If the bunch is surrounded by conducting surfaces, the bunch self-fields are modified. Image fields generated by...

The perturbative approach for describing the underdense plasma–ultrarelativistic electron bunch system is developed,using the ratio n0 nb as a small parameter (nb-bunch,n0plasma electron densities). Focusing of the electron bunch emerged in the first approximation of the perturbative procedure as a result of the plasma electrons redistribution.Focusing gradient and strength for ultrarelativisti...

The increase in single processor speed based on Moore’s law alone will not be able to deliver the dramatic speedup needed in many beam tracking simulations to uncover very slowly evolving effects in a reasonable time. SLAC has embarked on an effort to bring the power of parallel computing to bear on such computations with the goal to reduce the turnaround time by orders of magnitude so that the...

In CESR, 9 trains of 4 or 5 bunches of electrons and positrons collide at the interaction point, but bypass each other in the arcs of the storage ring using electrostatically separated orbits (pretzels). The parasitic bunch crossings resulting from the use of pretzel separation causes the bunches to have different orbits and, thus, the luminosity to be sensitive to the relative transverse posit...

In routine operation the Cornell Electron/positron Storage Ring, CESR, collides 9 trains of 4 or 5 bunches of electrons and positrons. The luminosity of individual bunch pairs can suffer if the transverse positions of those bunches are displaced differentially. This paper will present the results of studies of the effect of bunch–by–bunch or train– by–train variations in the luminosity by measu...

Nothing epitomizes the mystery of life more than the spatial organization and dynamics of the cytoplasm. How can a bunch of molecules, no matter how sophisticated, generate spatially complex behavior on a scale that is much larger than the molecules themselves? In my view, we will be done as cell biologists when we can predict the structure and dynamics of cells from DNA sequence. That goal is ...

We have directly measured the mm-wave wake fields induced by subpicosecond, intense relativistic electron bunches in a diamond loaded accelerating structure via the dielectric wake-field acceleration mechanism. Fields produced by a leading drive beam were used to accelerate a trailing witness electron bunch which followed the driving bunch at an adjustable distance. The energy change of the wit...

In the TESLA Test Facility (TTF), short bunches with low emittance are needed for the operation of a free electron laser. Several stages of bunch compression by means of magnetic chicanes will be used to reach the required peak current. The second stage of the bunch compression system, bunch compressor II, has been taken into operation recently. We describe design and instrumentation of the bun...