55,238 research outputs found
Surface micromachined solenoid on-Si and on-glass inductors for RF applications
No full textRF performance of surface micromachined solenoid on-chip inductors fabricated on a standard silicon substrate (10 Omega. cm) has been investigated and the results are compared with the same inductors on glass, The solenoid inductor on Si with a 15-mu m thick insulating layer achieves peak quality (Q-) factor of 16.7 at 2.4 GHz with inductance of 2.67 nH, This peak Q-factor is about two-thirds of that of the same inductor fabricated on glass. The highest performance has been obtained from the narrowest-pitched on-glass inductor, which shows inductance of 2.3 nH, peak Q-factor of 25.1 at 8.4 GHz, and spatial inductance density of 30 nH/mm(2), Both on-Si and on-glass inductors have been modeled by lumped circuits, and the geometrical dependence of the inductance and Q-factor have been investigated as well
Multiperiodic states and bifurcations in bunch lengthening by a localized impedance in electron storage ring
No full textThe equilibrium particle distribution of a bunch in an electron storage ring is investigated using a localized constant wake function. It is shown that, under some conditions, stable multiperiodic states can exist simultaneously. When moving around the parameter space, the system can show bifurcation phenomena which is not always reversible, We study this behavior using the Gaussian approximation and compare the results with multiparticle tracking. The results show qualitative agreement.X116sciescopu
Transverse beam instability in a 50 GeV x 50 GeV muon-collider ring
No full textThe transverse beam instability due to a broad-band impedance in a 50 GeV x 50 GeV muon-collider ring is numerically investigated. It is shown that the transverse beam size is increased by a factor of five when the impedance, Z(\ \)/n, is 1.7 Omega. The transverse instability is shown to be cured by introducing tune spreads, such as BNS damping, chromaticity, amplitude-dependent tune shift, and beam-beam interaction. It is shown that any one of these tune spreads limits the growth of the beam size to less than 20%. (C) 2001 Elsevier Science B.V. All rights reserved.X111sciescopu
Design of transverse muon-cooling channels for a neutrino factory
No full textIonization cooling is the preferred method for transverse cooling of a muon beam in a neutrino factory. In this paper, we design two different cooling channels, a DF0F0 channel and an alternating solenoid channel, and show that the transverse beam emittance through these cooling channels is cooled down by a factor of 7.7 and 6.5, respectively. The cooling channel design has been carried out by invoking the ICOOL program. Transmission efficiency, transverse beam emittance, growth of longitudinal bunch length, and momentum spread are investigated. It is shown that these two cooling channels provide adequate cooling performance, satisfying the so-called Palmer, Johnson and Keil (PJK) parameter for a neutrino factory. It is also shown that the numerical results agree well with those of analytical formulae.X112sciescopu
Transverse beam instability due to a broad-band impedance in very large hadron-collider ring
No full textThe strong head-tail instability due to a broad-band impedance in the very large hadron-collider (VLHC) ring of 20 TeV is numerically, investigated. It is shown that the beam size increases significantly when the impedance, Z(parallel to)/n, is 0.6 Omega, which is the estimated impedance budget in the design. The beam instability is shown to be cured by introducing tune spreads, such as RF quadrupole, chromaticity and amplitude-dependent tune shift. It is shown that any of these tune spreads limits the growth of the beam size to less than 3%. It is shown that threshold impedance for the instability is estimated to be about Z(parallel to)/n = 0.3 Omega.X11sciescopu
Decoherence of beam oscillation in a 2 TeV x 2 TeV muon-collider ring
No full textThe decoherence behavior of betatron-oscillation motion of a beam after a transverse kick is examined by a multiparticle tracking method. When a beam is displaced transversely, it undergoes a betatron oscillation and the oscillation decays in time because of decoherence among the oscillations of different particles. The rate of decoherence depends on the spread of betatron frequencies as well as the strength of wakefields. The impedances of a broad-band resonator model and rf cavity are adopted. Operation of the ring with a slippage factor eta (1) similar or equal to -10(-6) in the 2 TeV x 2 TeV muon-collider ring may lead to beam breakup-like instability. It is explicitly shown that the decoherence due to betatron-tune spreads results in a transition from beam breakup-like instability to stable beam oscillation. Emittance growth due to a strong wakefield is also shown to be suppressed by tune spreads.X11sciescopu
Investigation of longitudinal beam distributions due to potential-well distortion in the PLS storage ring
No full textIn this paper, we examine the effect of the wakefields generated by an interaction between the circulating electron beam and the rf cavities and components of vacuum chambers on the longitudinal beam distribution, with particular emphasis on the Pohang Light Source (PLS) storage ring. In order to obtain an equilibrium longitudinal beam distribution for a single beam, we utilized both a numerical solution of the Vlasov equation and a multi-particle tracking method. Results show that the impedance due to the beam-cavity interaction affects the longitudinal beam deformation less than the broadband impedance in the ring does. The results of the Vlasov method are shown to be in good agreement with those of the multi-particle tracking method.X115sciescopuskciothe
Nonlinear Behavior of bunch lengthening by using a localized wake in electron storage rings
No full textThe equilibrium particle distribution of a bunch is investigated by using a localized delta' wake in an electron storage ring. A mapping method is performed to show the dynamical behavior of the particle distribution by using the Gaussian approximation. It is shown that stable multi-periodic states, a limit cycle, and chaos can exist under some conditions. When moving around the parameter space, the system can show bifurcation phenomena.X111sci
Compensation of beam-beam interaction in a 50 GeV x 50 GeV muon-collider ring
No full textThe effect of a beam-beam interaction on the motion of a circulating beam in a 50 GeV x 50 GeV muon-collider ring is investigated by weak-strong beam modeling. In the present design of the muon-collider storage ring, the frequency-slippage factor eta (1) is approximately -5 x 10(-7) so that the synchrotron motion is nearly frozen. This may lead to an increase in the energy spread due to the beam-beam interaction. Through the weak-strong beam modeling, we have investigated the parametric dependencies of the energy spread induced by the beam-beam interaction. We show in this paper that the energy spread due to the beam-beam interaction is large and can be compensated for by employing one ri cavity in the ring with a modest rf voltage.X112sciescopu
Beam Dynamics in a 10-GeV Linear Accelerator for the X-Ray Free Electron Laser at PAL
No full textWe investigated beam dynamics in a 10-GeV linear accelerator for SASE (Self-Amplified Spontaneous Emission) Free-Electron Laser (FEL) at PAL. The linac is designed to provide the optimal beams to generate radiation of the wavelength of 1-angstrom in the undulator. An optimum choice of beam parameters is performed to reduce the correlated energy spread after final beam compression and to make accelerator system insensitive to rf jitters. The two-stage bunch compressors are designed to reduce the effects of coherent synchrotron radiation and thus the transverse emittance is not significantly increased. The bunch compressors are also designed such that the effects of nonlinearities due to wake-fields, rf curvature and second order momentum compaction become as small as possible in the linear accelerator. With a careful choice of beam and accelerator parameters, the bunch compression process can be made more linear, which minimizes bunch length that can be achieved and helps to reduce high peak current spikes in the beam distributions, which may deteriorate the SASE performance. The tracking simulations in the linear accelerator include longitudinal and transverse wakefields, and the effects of errors such as rf gun timing, rf phase and rf voltage. The simulations also include the X-band rf section and its wakefield. In result, through these design studies, we could get beam parameters and accelerator parameters to be able to provide the radiation power of 6 GW in the wavelength of 1-angstrom in a 94-m-long undulator. Results on low-charge case of 0.2 nC and the microbunching instability are also shown. It is shown that the designed linac with a tuneable lattice shows satisfactory performances for a 10-GeV X-ray FEL facility.X11910sciescopu
- …
