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Proposal for a Multi-Use Test Beam in the SLAC B-Line

Description: With the impending construction of the Linac Coherent Light Source (LCLS) [1] at SLAC, displacing the well used Final Focus Test Beam (FFTB) area, there is growing interest in developing a new test beam facility which makes use of the remaining 2/3 of the SLAC linac, and is available during LCLS operations. The success of the Sub-Picosecond Pulse Source (SPPS) [2] and the desire to preserve this capacity suggest a new beamline with similar or improved electron beam quality, including bunch length compression to 10 {micro}m. Beam availability during LCLS operations requires a new 1-km bypass beamline connecting the 2/3-point of the linac with, for example, the existing B-Line tunnel at the end of the linac. A second operating mode, with LCLS not running, is then available using the existing connection directly from the end of the linac to the B-line. This path would provide the highest beam quality at 30 GeV and also allow a third operational mode by deflecting a few of the very high-brightness 120-Hz, 14-GeV LCLS bunches at low rate (1-10 Hz) into the B-line. Additionally, linear collider research might also be carried out in a short final focus system at the end of the B-Line, capable of producing a 70-nm rms transverse beam size. We describe a design for these systems.
Date: May 25, 2005
Creator: Emma, P.; Bentson, L.; Erickson, R.; Fieguth, T.; Seeman, J.; Seryi, A. et al.
Partner: UNT Libraries Government Documents Department

Inverse Free Electron Laser Heater for the LCLS

Description: The Linac Coherent Light Source (LCLS) free electron laser employs an RF photocathode gun that yields a 1nC bunch a few picoseconds long, which must be further compressed to yield the high current required for Self Amplified Spontaneous Emission (SASE) gain. The electron beam from the RF photocathode gun is quite sensitive to microbunching instabilities such as coherent synchrotron radiation (CSR) in the compressor chicanes and longitudinal space charge (LSC) in the linac. These effects can be Landau damped by adding energy spread to the electron bunch prior to compression. They propose to do this by co-propagating an infrared laser beam with the electron bunch in an undulator in the LCLS injector beamline. The undulator is placed in a four bend magnet chicane to allow the Ir laser beam to propagate colinearly with the e-beam while it oscillates in the undulator. The IR laser beam is derived from the photocathode gun drive laser, so the two beams are synchronized. Simulations presented elsewhere in these proceedings show that the laser interaction damps the microbunching instabilities to a very great extent. This paper is a description of the design of the laser heater.
Date: May 11, 2005
Creator: Bentson, L.D.; Bolton, P.; Carr, R.; Dowell, D.; Emma, P.; Gilevich, S. et al.
Partner: UNT Libraries Government Documents Department

SLAC Linac Preparations for FACET

Description: The SLAC 3km linear electron accelerator has been cut at the two-thirds point to provide beams to two independent programs. The last third provides the electron beam for the Linac Coherent Light Source (LCLS), leaving the first two-thirds available for FACET, the new experimental facility for accelerator science and test beams. In this paper, we describe this separation and projects to prepare the linac for the FACET experimental program.
Date: February 7, 2011
Creator: Erickson, R.; Bentson, L.; Kharakh, D.; Owens, A.; Schuh, P.; Seeman, J. et al.
Partner: UNT Libraries Government Documents Department

Coupler Design for the LCLS Injector S-Band Structures

Description: The LCLS injector is required to provide a 1-nC, 10-ps bunch with a normalized rms transverse projected emittance of less than 1 micron. The LCLS beam is generated and accelerated in a 1.6-cell S-band RF gun at 120 MV/m up to 6 MeV. The gun is followed by two SLAC 3-m S-band accelerator structures to further accelerate the beam to 135 MeV which moves the beam out of the space-charge dominated regime. In the SLAC S-band structures, the RF power feed is through a single coupling-hole (single-feed coupler) which results in a field asymmetry. The time dependent multipole fields in the coupler induce a transverse kick along the bunch and cause the emittance to increase above the LCLS specification. To meet the stringent emittance requirements for the injector, the single-feed couplers will be replaced by a dual-feed racetrack design to minimize the multipole field effects. We will present detailed studies of the multipole fields in the SLAC linac RF coupler and the improvements with the dual-feed ractrack design using the parallel finite element S-parameter solver S3P.
Date: March 3, 2006
Creator: Li, Z.; Bentson, L.D.; Chan, J.; Dowell, D.H.; Limborg-Deprey, C.; Schmerge, J.F. et al.
Partner: UNT Libraries Government Documents Department

Optics Design for FACET

Description: FACET is a proposed facility at SLAC National Accelerator Laboratory. It will provide high energy, tightly focused and compressed electron and positron bunches for beam driven plasma wakefield acceleration research and other experiments. FACET will be built in the SLAC linac sector 20, where it will be separated from the LCLS located immediately downstream and will take advantage of the upstream 2 km linac for up to 23 GeV beam acceleration. FACET will also include an upgrade to linac sector 10, where a new e+ compressor chicane will be installed. The sector 20 will contain a new optics consisting of two chicanes for e+ and ebunch length compression, a final focus and an experimental line with a dump. The e+ and e- chicanes will allow the transport of e+ and ebunches together, their compression and proper positioning of e+ witness bunch behind the e- drive bunch at the plasma Interaction Point. The new optics will mostly use the existing SLAC magnets to minimize the project cost. Details of the FACET optics design and results of particle tracking simulations are presented.
Date: May 7, 2009
Creator: Nosochkov, Y.; Bane, K.; Bentson, L.; Erickson, R.; Hogan, M.J.; Li, N. et al.
Partner: UNT Libraries Government Documents Department

Ideas for a Future PEP-X Light Source

Description: SLAC is developing a long-range plan to transfer the evolving scientific programs at SSRL from the SPEAR3 light source to a much higher performing synchrotron source -- PEP-X -- a new storage ring that would occupy the existing PEP-II tunnel and support two experimental halls, each containing 16 x-ray beam lines. Operating at 4.5 GeV and 1.5 A with a horizontal emittance of 0.14 nm-rad, reached using 90 m of damping wigglers, PEP-X would have an order of magnitude higher average brightness and flux in the 1-{angstrom} x-ray range than any existing or planned future storage ring sources. Higher brightness in the soft x-ray regime might be reached with partial lasing in long undulators, and high peak brightness could be reached with seeded FEL emission. The status of preliminary studies of PEP-X is presented.
Date: November 2, 2011
Creator: Hettel, R.O.; Bane, K.L.F.; Bentson, L.D.; Bertsche, Kirk J.; Brennan, S.M.; Cai, Y. et al.
Partner: UNT Libraries Government Documents Department