[en] We have carried out computer simulations using MATLAB to study the transverse coupled-mode instability (TMCI) in the proposed NSLS-II storage ring. Our calculations have been performed using transverse short-range wakefields describing: a broad-band resonator; a resistive wall with normal surface impedance; and a chamber wall with extreme anomalous skin effect. We have considered: (1) the ring with a single-frequency RF system for which the equilibrium longitudinal bunch distribution is Gaussian; and (2) the ring with a third harmonic (Landau) cavity included to lengthen the bunch. Based on current NSLS-II design parameters, we report estimates of the TMCI threshold behavior. All of our results for the instability threshold (at zero chromaticity) are consistent (to about ± 30%) with the simple relation e²N_e^thβ_y/4πγmc² v_s κ_#perpendicular# ≅ 0.7, where κ_#perpendicular# is the transverse kick factor, N_e^th is the number of electrons in the bunch at threshold, β_y is the vertical beta function at the impedance, and γ mc² is the electron energy. For a single-frequency RF system v_s is the synchrotron tune, while for a Landau cavity, v_s is the synchrotron tune of an electron with synchrotron amplitude equal to the rms bunch length

[en] Along the general run of the vacuum chamber synchrotron radiation strikes the wall at a glancing angle of about 5.6⁰. The heat source is well-approximated by a ribbon of uniform power density having a small vertical height and an infinite azimuthal length. The heat transfer problem reduces to one in two-dimensions and it has been considered in a previous note. At the corner of a beam port the angle of incidence becomes 90⁰, so the temperature rises much higher than elsewhere. Since the power density at the corner is not uniform in its azimuthal dependence, but is strongly peaked at the point of normal incidence, two-dimensional heat flow is not a good approximation. The rectangular 3d problem is considered. This is easily solved and yields a good first estimate of the temperature rise at the corner

[en] A summer study was held in 1977 to provide definitive recommendations on the design of the National Synchrotron Light Source. The group attending the workshop included electron storage ring experts. Topics covered in the proceedings include: introduction to the lattice; partial list of corrective or diagnostic equipment; closed orbit errors in the 2.5 GeV x-ray source; linear horizontal-vertical coupling, vertical dispersion, and control of the vertical closed orbit at the wiggler; bunch lengthening and longitudinal stability; longitudinal stability with a Landau cavity; transverse coupled-bundle instabilities; coupling impedance and power dissipation for a step change in the vacuum chamber; bunch lengthening and widening; aperture limitations by sextupoles; second-order effects of correction sextupoles; horizontal aperture in x-ray ring; introduction of sinusoidal wiggler into the x-ray lattice; the Touchek effect; possible mode of injection into the x-ray ring; and an inquiry into the flexibility of the x-ray lattice

[en] We review the statistical description of the chaotic time evolution of the radiation from a self-amplified spontaneous-emission free-electron laser in the linear region before saturation. A high-gain, self-amplified spontaneous-emission (SASE) free-electron laser (FEL) (1, 2), based on modern beam technology, has the advantage of operating without a resonator and hence is capable of generating coherent radiation with wavelength down to the x-ray region. The LCLS at SLAC has recently achieved high gain and saturation at 1.5 (angstrom) (3). A review of SASE theory can be found in ref. (4). In this paper, we have considered the linear regime before saturation. In the nonlinear saturation regime, SASE is no longer a Gaussian process and analytic treatment is very difficult. A valuable numerical simulation analysis of the statistical behavior in the nonlinear regime can be found in ref. (10,11).

[en] The development of synchrotron radiation sources is discussed, emphasizing characteristics important for x-ray microscopy. Bending magnets, wigglers and undulators are considered as sources of radiation. Operating experience at the national Synchrotron Light Source on the VUV and XRAY storage rings is reviewed, with particular consideration given to achieved current and lifetime, transverse bunch dimensions, and orbit stability. 6 refs., 3 figs

[en] The number of temporal modes in the SASE output can be defined in several ways: as the ratio of the phase space area occupied by the radiation to the minimum area allowed by the uncertainty principle; in terms of the fluctuation of the pulse energy; and in terms of the Wigner function. Here, we discuss these different definitions and show their equivalence for SASE from a Gaussian electron bunch, in the linear regime before saturation

[en] We present an introduction to the operating principles of free-electron lasers, discussing the amplification process, and the requirements on the electron beam necessary to achieve desired performance

[en] Over the last two decades great progress has been made in the development of storage rings with small transverse emittance. It is now a good time to consider the possibility of achieving very short bunches m storage rings. From the perspective of synchrotron radiation source development, there are at least two motivations for obtaining short electron bunches: (1) the generation of sub- picosecond x-ray pulses and (2) the coherent emission of sub- picosecond pulses of far infrared radiation. A useful short-term goal is the experimental study of bunches with 1 ps rms length both at high (approx-gt 1 GeV) and low (approx-lt 150 MeV) electron energies. Experiments on 1 ps bunches are now feasible and can yield new insight into the high frequency impedance of storage rings and the associated phenomena which can result in bunch lengthening. Achievement of 1 ps bunches can also be expected to allow the first observation of coherent synchrotron radiation in a storage ring, in the millimeter wavelength regime. A longer-term objective is the realization of 100 fs bunches. Achievement of this goal not only will advance understanding of storage rings but will open up new opportunities in synchrotron radiation based research at both x-ray and far infrared wavelengths. It is now an appropriate time to carry forward theoretical investigations clarifying the fundamental limitations on bunch length, and to devise schemes to minimize it

[en] Stupakov has used a perturbation method to estimate the transverse impedance at zero frequency of a rectangular collimator having characteristic taper length (ell), half-width w, and average vertical half-aperture b₀, under the condition b₀ << w << (ell). We use the boundary perturbation method to approximate the transverse impedance of a flat, slowly tapered chamber in the complementary limit, w = ∞

[en] Self-sustained synchrotron oscillations are observed in electron storage rings. In general the theoretical description of the saturation of an instability for large oscillation amplitude is a difficult problem, and techniques have not yet been developed which yield analytic approximations to the appropriate nonlinear Vlasov or Fokker-Planck equations. In this paper, a single point bunch interacting with the wake field from a single resonant mode of an rf cavity is considered, and the averaging method of Bogoliubov and Mitropolsky is used to study the saturation of the initial exponential growth of the oscillation amplitude, due to the nonlinearity of the wake field. The determination of the limiting amplitude of oscillation is discussed both in the presence and in the absence of radiation damping