SLAC, Menlo Park, California, USA
A photonic band gap (PBG) lattice in dielectric fiber can provide high gradient acceleration in the optical regime, where the accelerating mode is obtained from the presence of a single defect in the lattice. In this paper, we will investigate two aspects of the PBG for acceleration. First, the excitation of the accelerating mode can be achieved by directing high-power lasers from free space. Simulation using ACE3P has demonstrated that, by appropriately shaping the end of the PBG fiber, power can be coupled into the fiber using a simple laser configuration. Second, the wakefield generated by the transit of a beam through a PBG fiber will be simulated using ACE3P. The free-space, outgoing radiation spectrum and distribution of the wakefield will be evaluated and corroborated with measurements from a commercial fiber.
SLAC, Menlo Park, California, USA
ACE3P is a 3D parallel finite element code suite for cavity design and optimization including electromagnetic, thermal and mechanical effects. Taking advantages of the power of computing on multi processors, ACE3P's particle tracking module Track3P allows efficient multipacting (MP) simulation by extensive scanning in field gradient and on cavity surface to identify the occurrences of MP activities. The output from Track3P simulation includes the determination of resonant trajectories and their locations, the calculation of electron impact energy on cavity surface, and the evaluation of the electron enhancement counter as a function of field gradient. The sensitivity of MP on secondary emission yield can be readily obtained through postprocessing. Examples of Track3P MP simulation for the Muon cooling cavities and APS SPX cavity will be presented.
WEOAA1
LBNL, Berkeley, California, USA
SLAC, Menlo Park, California, USA
JLAB, Newport News, Virginia, USA
Fermilab, Batavia, USA
We present an overview of design studies and R&D toward NGLS a Next Generation Light Source initiative at LBNL. The design concept is based on a multi-beamline soft x-ray FEL array powered by a CW superconducting linear accelerator, and operating with a high bunch repetition rate of approximately 1 MHz. The linac design uses TESLA and ILC technology, supplied by an injector based on a CW normal-conducting VHF photocathode electron gun. Electron bunches from the linac are distributed by RF deflecting cavities to the array of independently configurable FEL beamlines with nominal bunch rates of ~100 kHz in each FEL, with uniform pulse spacing, and some FELs capable of operating at the full linac bunch rate. Individual FELs may be configured for different modes of operation, including self-seeded and external-laser-seeded, and each may produce high peak and average brightness x-rays with a flexible pulse format.
SLAC, Menlo Park, California, USA
ANL, Argonne, USA
JLAB, Newport News, Virginia, USA
A single-cell superconducting deflecting cavity operating at 2.815 GHz has been proposed and designed for the Short Pulse X-ray (SPX) project for the Advanced Photon Source (APS) upgrade. Each deflecting cavity is equipped with one fundamental power coupler (FPC), one lower order mode (LOM) coupler, and two higher order mode (HOM) couplers to achieve the stringent damping requirements for the unwanted modes. Using the electromagnetic simulation suite ACE3P, HOM damping will be calculated for the cavity including the full engineering design waveguide configurations and rf windows. Trapped modes in the bellows located in the beampipes connecting the cavities in a cryomodule will be computed and their effects on heating evaluated. Furthermore, multipacting activities at the end groups of the cavity will be identified to assess possible problems during high power processing.
SLAC, Menlo Park, California, USA
A beam “dechirper” based on a corrugated, metallic vacuum chamber has been proposed recently to cancel residual energy chirp in a beam before it enters the undulator in a linac-based X-ray FEL*. Rather than the round geometry that was originally proposed, we consider a pipe composed of two parallel plates with corrugations. The advantage is that the strength of the wake effect can be tuned by adjusting the separation of the plates. The separation of the plates is a few millimeters, and the corrugations are fractions of a millimeter in size. The dechirpers need to be meters long in order to provide sufficient longitudinal wakefield to cancel the beam chirp. Considerable computation resources are required to determine accurately the wakefield for such a long structure with small corrugation gaps. Combining the moving window technique and parallel computing using multiple processors, the parallel finite-element electromagnetic suite ACE3P allows efficient determination of the wakefield through convergence studies. In this paper, we will calculate the longitudinal, dipole and quadrupole wakefields for the dechirper and compare the results with those of analytical approaches.
* K.L.F. Bane, G. Stupakov, Nucl. Instrum. Meth. A690 (2012) 106-110.