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Open Access Publications from the University of California

Scholarly Works (17 results)

  • Article
LBL Publications (2006)
Ion induced beam instability and tune shift are critical issues for the electron damping ring of the International Linear Collider (ILC). To avoid conventional ion trapping, gaps are introduced in the electron beam by missing bunches in a train of bunches. However, the beam can still suffer from the fast ion instability (FII) driven by ions that last only for a single passage of the electron beam and are not trapped for multiple turns. Our study shows that the ion effects can be significantly mitigated by using multiple gaps, so that the stored beam consists of a number of relatively short bunch trains. Another way to avoid trapped ions is to introduce clearing electrodes. The ion effects in the ILC damping rings are investigated using both analytical and numerical methods.
    Cover page: Ion Effects in the Electron Damping Ring of the International Linear Collider
    • Article
    LBL Publications (2003)

    In the beam pipe of the Main Damping Ring (MDR) of the Next Linear Collider (NLC), ionization of residual gasses and secondary emission give rise to an electron-cloud which stabilizes to equilibrium after few bunch trains. In this paper, we present recent computer simulation results for the main features of the electron cloud at the NLC and preliminary simulation results for the TESLA main damping rings, obtained with the code POSINST that has been developed at LBNL, and lately in collaboration with SLAC, over the past 7 years. Possible remedies to mitigate the effect are also discussed. We have recently included the possibility to simulate different magnetic field configurations in our code including solenoid, quadrupole, sextupole and wiggler.

      Cover page: Recent electron-cloud simulation results for the main damping rings of the NLC and TESLA linear colliders
      • Article
      LBL Publications (2005)

      We present bunch compressor designs for the International Linear Collider (ILC) which achieve a reduction in RMS bunch length from 6 mm to 0.3 mm via multiple stages of compression, with stages of acceleration inserted between the stages of compression. The key advantage of multi-stage compression is that the maximum RMS energy spread is reduced to approximately 1 percent, compared to over 3 percent for a single-stage design. Analytic and simulation studies of the multi-stage bunch compressors are presented, along with performance comparisons to a single-stage system. Parameters for extending the systems to a larger total compression factor are discussed.

        Cover page: Multi-Stage Bunch Compressors for the International Linear Collider
        • Article
        LBL Publications (2004)
          Cover page: A lattice with larger momentum compaction for the NLC main damping rings
          • Article
          • Peer Reviewed
          LBL Publications (2017)
          The shot-noise driven microbunching instability can significantly degrade electron beam quality in x-ray free electron laser light sources. Experiments were carried out at the Linac Coherent Light Source (LCLS) to study this instability. In this paper, we present start-to-end simulations of the shot-noise driven microbunching instability experiment at the LCLS using the real number of electrons. The simulation results reproduce the measurements quite well. A microbunching self-heating mechanism is also illustrated in the simulation, which helps explain the experimental observation.
            Cover page: Start-to-end simulation of the shot-noise driven microbunching instability experiment at the Linac Coherent Light Source
            • Article
            LBL Publications (2005)

            Collective instabilities caused by the formation of anelectron cloud (EC) are a potential limitation to the performances of the damping rings for a future linear collider. In this paper, we present recent simulation results for the electron cloud build-up in damping rings of different circumferences and discuss the single-bunch instabilities driven by the electron cloud.

              Cover page: Single-Bunch Instability Driven by the Electron Cloud Effect in the Positron Damping Ring of the International Linear Collider
              • Article
              LBL Publications (1992)
                Cover page: A 2 to 4 nm High Power FEL on the SLAC Linac
                • Article
                • Peer Reviewed
                LBL Publications (2019)
                We present the results from studies of soft X-ray seeding options for the LCLS-II X-ray free electron laser (FEL) at SLAC. The LCLS-II will use superconducting accelerator technology to produce X-ray pulses at up to 1 MHz repetition rate using 4 GeV electron beams. If properly seeded, these pulses will be nearly fully coherent, and highly stable in photon energy, bandwidth, and intensity, thus enabling unique experiments with intense high-resolution soft X-rays. Given the expected electron beam parameters from start to end simulations and predicted FEL performance, our studies reveal echo enabled harmonic generation (EEHG) and soft X-ray self-seeding (SXRSS) as promising and complementary seeding methods. We find that SXRSS has the advantage of simplicity and will deliver 5-35 times higher spectral brightness than EEHG in the 1-2 nm range, but lacks some of the potential for phase-stable multipulse and multicolor FEL operations enabled by external laser seeding with EEHG.
                  Cover page: Soft x-ray seeding studies for the SLAC Linac Coherent Light Source II
                  • Article
                  • Peer Reviewed
                  LBL Publications (2017)
                  There is a great interest in generating high-power hard X-ray Free Electron Laser (FEL) in the terawatt (TW) level that can enable coherent diffraction imaging of complex molecules like proteins and probe fundamental high-field physics. A feasibility study of producing such X-ray pulses was carried out employing a configuration beginning with a Self-Amplified Spontaneous Emission FEL, followed by a “self-seeding” crystal monochromator generating a fully coherent seed, and finishing with a long tapered undulator where the coherent seed recombines with the electron bunch and is amplified to high power. The undulator tapering profile, the phase advance in the undulator break sections, the quadrupole focusing strength, etc. are parameters to be optimized. A Genetic Algorithm (GA) is adopted for this multi-dimensional optimization. Concrete examples are given for LINAC Coherent Light Source (LCLS) and LCLS-II-type systems. Analytical estimate is also developed to cross check the simulation and optimization results as a quick and complimentary tool.
                    Cover page: Multi-dimensional optimization of a terawatt seeded tapered Free Electron Laser with a Multi-Objective Genetic Algorithm
                    • Article
                    Lawrence Berkeley National Laboratory (2001)
                      Cover page: The next linear collider damping ring complex
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