17396361
An analytic model of rotating hot spot and kHz QPOs in X-ray binaries
An analytic model of rotating hot spot is proposed to explain kilohertz quasiperiodic oscillations (kHz QPO) in X-ray binaries, which is based on the magnetic coupling (MC) of a rotating black hole (BH) with its surrounding accretion disc. The hot spot in the inner region of the disc is produced by energy transferred from a spinning BH with non-axisymmetric magnetic field. The frequency and energy band of the hot spot turns out to be related to six parameters, by which the strength and the azimuthal angular region of the bulging magnetic field on the BH horizon, the mass and spin of the BH, and the power-law index of the magnetic field varying with the radial coordinate on the disc are described. In addition, the correlation of the fluctuation of the bulging magnetic field with the widths of QPO frequency is discussed.
17295428
Influences of the magnetic coupling process on the spectrum of a disk covered by the corona
Context. Recently, much attention has been paid to the magnetic coupling (MC) process, which is supported by the very high emissivity indexes observed in Seyfert 1 galaxy MCG-6-30-15 and GBHC XTE J1650-500. But the rotational energy transferred from a black hole is simply assumed to be radiated away from the surrounding accretion disk in the black-body spectrum, which is obviously not consistent with the observed hard power-law X-ray spectra. Aims. We introduce a corona into the MC model to make it more compatible with observations. Methods. We describe the model and the procedure of a simplified Monte Carlo simulation, compare the output spectra in the cases with and without the MC effects, and discuss the influences of the three parameters involved in the MC process on the output spectra. Results. It is shown that the MC process augments radiation fluxes in the UV or X-ray band. The emergent spectrum is affected by the BH spin and magnetic field strength at the BH horizon, while it is almost unaffected by the radial profile of the magnetic field at the disk. Conclusions. Introducing corona into the MC model will improve the fitting of the output spectra from AGNs and GBHCs.
117533820
Longitudinal kinetic energy spread from focusing in charged particle beams
A charged particle beam can be given a longitudinal kinetic energy spread through focusing by magnetic solenoid lenses. Measurements of energy spread are reported and are compared with the results of computer simulations, which include several known sources of energy spread. These sources are discussed. The results of the measurements and the simulations agree, giving energy spreads which are two orders of magnitude larger than the initial thermal energy spread.<<ETX>>
55579613
Computer simulation of the Maryland Transport Experiment
The longitudinal dynamics of the high-perveance long-pulse electron beam in the Maryland Transport Experiment is examined for the special case of an initially parabolic bunch. Because the longitudinal dynamics can depend on details of time-dependent transverse beam parameters which are difficult to measure, sensitivity studies using r-z simulations have been used to demonstrate that the details of longitudinal beam evolution are insensitive to transverse mismatch, and the bunch length evolution can be accurately described by the one-dimensional envelope equation with the "geometry factor" appropriately chosen. Comparison of experimental data to r,z simulation and to the envelope solution is presented.<<ETX>>
27409140
Generation of space-charge waves due to localized perturbations in a space-charge dominated beam.
It has been found for the first time in experiments with an electron beam that space-charge waves can be generated not only in pairs. A single slow wave, a single fast wave, or combinations of the two waves with different amplitude and polarity relations have been produced experimentally in a space-charge dominated beam. Analytical solutions derived from one-dimensional fluid equations show the amplitude and polarity of each space-charge wave as a function of the initial perturbation parameters. The theory provides the correct interpretation of the experimental observations.
39487088
Restoration of rectangular pulse shape after edge erosion for a space-charge dominated electron bunch.
We present in this Letter a novel experimental method that demonstrates the time reversibility of the 1D cold-fluid equations for a space-charge dominated beam. A bunch of charged particles with an initially rectangular line-charge and velocity profile experiences edge erosion during transport through a focusing system due to the nonlinear, longitudinal space-charge forces at the edges. By imposing on the eroded beam pulse a linear velocity gradient at a proper location one can restore the rectangular line-charge profile downstream. [An experiment has been performed to demonstrate this principle.] This technique could be used to offset edge erosion and assure a rectangular pulse shape for efficient acceleration and uniform power flow in the interaction region for applications of intense, high-power beams.
55356715
PROGRESS OF THE eRHIC ELECTRON RING DESIGN
Over the past year, a baseline design of the electron ring for the eRHIC hadron-lepton collider has been developed. This site-specific design is based on the understanding of the existing RHIC machine performance and its possible upgrades. The design includes a full energy polarized electron beam injector to ensure operational reliability and to provide high integrated luminosity. The electron ring energy range is 5 to 10 GeV. The electron beam emittance, the electron beam path length, and the interaction region optics have to be adjustable over wide ranges depending on the ion species and energy for collisions. We describe the design features and expected machine performance. The results of recent beam polarization and beam-beam studies are also discussed.
172134161
INSTALLATION AND COMMISSIONING OF THE 100 MeV PREINJECTOR LINAC OF THE NEW ELETTRA INJECTOR
A new full energy injector has been installed and commissioned at ELETTRA, the Italian Synchrotron Light Source facility in Trieste. It consists of a 100 MeV pre-injector linac followed by a 2.5 GeV booster Synchrotron, that fills the Elettra Storage Ring with 2.0 GeV and 2.4 GeV electrons. Here a complete description of the preinjector linac and a first evaluation of its performance will be presented and discussed. INTRODUCTION AND MILESTONES The new ELETTRA full energy injector, consisting of a 100 MeV pre-injector linac and a 2.5 GeV booster synchrotron, has been successful commissioned and routinely providing electrons for the storage ring for users operations since 3 of March 2008 [1]. The new pre-injector linac can fill the booster in two operating modes: • single bunch mode (SB), with one booster RF bucket (@500 MHz) filled; • multibuch mode (MB), with up to 75 buckets filled. The main parameters of the machine are summarized in Table 1, showing the designed and achieved performance. One of the most important requirements of the new injection system is to guarantee the operation in top-up mode, keeping constant the ELETTRA stored current. This in general implies machine reliability and an adequate safety margin for the operating levels of the main components. For this reasons the pre-injector layout foresees a second RF power station, now under assembly, with a spare klystron that guarantees the machine operation in case of fault of the main RF plant. This will have a noticeably effect on the down time of the machine. The installation of the pre-injector started at the end of June ’07 with co-occupancy of the building and putting in place the two main accelerating sections. The whole machine installation, the first RF plant, the WG circuits and the ancillary systems, was completed in late August. Two weeks were spent for RF conditioning of the accelerating structures (Aug. 24Sept. 6), pushing the klystron peak power up to 38-40 MW for 3.5 μsec pulse width at 10 Hz pulse repetition rate (prr). The first electrons from the gun were extracted on September 7 (multi bunch mode) and a week later we transported the first accelerated beam to the exit of the second accelerating section, measuring 90 MeV beam energy (September 15). Then the machine was operated up to Sept. 24 to explore its performance and for beam optimization. With a quite moderate level of power from the klystron, (≈ 36 MW), we have obtained a beam energy in excess of 115 MeV, with 100 mA current in 100 nsec pulse width. The overall transmission efficiency (Gun-Linac exit) was better than 60% and a first estimation of beam energy spread was less than 1 MeV @ 115 MeV. After these preliminary tests, from September 25, the machine was set at 110 MeV, 20 mA, 100 nsec, to allow, the starting of booster commissioning. Table 1: Preinjector main beam parameters
119298311
Dependence of quantum correlations of twin beams on the pump finesse of an optical parametric oscillator
The dependence of quantum correlations of twin beams on the pump finesse of an optical parametric oscillator is studied via a semi-classical analysis. It is found that the phase-sum correlation of the output signal and idler beams from an optical parametric oscillator operating above threshold depends on the finesse of the pump field when the spurious pump phase noise generated inside the optical cavity and the excess noise of the input pump field are involved in the Langevin equations. The theoretical calculations can explain the previously experimental results quantitatively.
53997503
A PERMANENT MAGNET PHASE SHIFTER FOR THE EUROPEAN X-RAY FREE ELECTRON LASER
In undulator systems with adjustable gaps phase shifters are needed to exactly control the phase retardation between electrons and the radiation field over the entire length of an undulator system. A phase shifter based on Permanent Magnet technology for the use in the European XFEL has been developed and tested. Specifications are given. This paper will explain its magnetic principle and design. Magnetic test results are presented and thoroughly discussed. Special attention is given to the operation in the XFEL.
29813748
Intrabeam scattering and touscheck lifetime for the optical stochastic cooling experiment at the MIT-Bates South Hall ring
A proof-of-principle experiment of optical stochastic cooling (OSC) at the MIT-Bates South Hall electron storage ring (SHR) has been proposed. To produce convincing cooling results, the ring will be run near 300 MeV. Beam emittance growth caused by Intrabeam scattering (IBS) is a major concern for the design of experiment. Touschek scattering imposes a dominant limit on beam lifetime. Evaluation of these effects is part of the design optimization process. Simulation analyses of cooling for a viable OSC experiment are presented.