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The Jacobi-Anger identity is employed to quantify the findings of Morse, Orlov and Semertzidis [1]. The secular term in the longitudinal spin component is proportional to a Bessel function. A suggestion for values of machine parameters to optimize the secular term is presented.
The article considers an opportunity of gas-dynamic acceleration of body from the initial zero velocity till the finite velocity: five kilometers per second. When the gas flow rate of the body pre-acceleration reaches one kilometer per second, the body is accelerated at the front of the explosion wave propagating along the coils of the hexogen spiral. This wave accelerates the body and, finally, it reaches the velocity of five kilometers per second. The accelerated body has mass one-tenth of a kilogram and diameter eleven and three tenths of a millimeter. Acceleration length is six meters. At the slope of the spiral to the horizon equal to seventy degrees the flight range of the body is equal to sixteen hundred kilometers and the maximum height of the flight is eleven hundred kilometers.
I derive an expression for the spin decoherence rate for a smooth focusing electrostatic ring with a radial electric field. The answer contains some salutary lessons about spin decoherence calculations in electrostatic storage rings: the numerical tracking results disagreed with naive analytical calculations, but it was the tracking results which were correct, and more careful analytical calculations (canonical transformations) were required.
Multidimensional optimization schemes for TW hard X-Ray free electron lasers are applied to the cases of transversely uniform and parabolic electron beam distributions and compared to examples of transversely Gaussian beams. The optimizations are performed for a $200$m undulator and a resonant wavelength of $λ_r=1.5Å$ using the fully 3-dimensional FEL particle code GENESIS. Time dependent simulations showed that the maximum radiation power is larger for flatter transverse distributions due to enhanced optical guiding in the tapered section of the undulator. For a transversely Gaussian beam the maximum output power was found to be $\text{P}_{max}$=$1.56$ TW compared to $2.26$ TW for the parabolic case and $2.63$ TW for the uniform case. Spectral data also showed a 30-70$\%$ reduction in energy deposited in the sidebands for the uniform and parabolic beams compared with a Gaussian. An analysis of the maximum power as a function of detuning from resonance shows that redshifting the central wavelength by $Δλ/ λ<ρ$ increases the power for all three transverse electron distributions.
For heavy-ion synchrotrons an efficient Multi-Turn Injection (MTI) from the injector linac is crucial in order to reach the specified currents using the available machine acceptance. The beam loss during the MTI must not exceed the limits determined by machine protection and by the vacuum requirements. Especially for low energy and intermediate charge state ions, the beam loss at the injection septum can cause a degradation of the vacuum and a corresponding reduction of the beam lifetime. In order to optimize the injection of intense beams a very detailed simulation model was developed. Besides the closed orbit bump, lattice errors, the position of the septum and other aperture limiting components the transverse space charge force is included self-consistently. The space charge force causes a characteristic shift of the optimum tunes and a smoothing of the phase space density.
Results of numerical simulations of electron channeling and emission spectra are reported for straight and uniformly bent silicon crystal. The projectile trajectories are computed using the newly developed module [1] of the MBN Explorer package [2,3]. The electron channeling along Si(110) crystallographic planes is studied for the projectile energy 855 MeV.
Electron lenses are pulsed, magnetically confined electron beams whose current-density profile is shaped to obtain the desired effect on the circulating beam in high-energy accelerators. They were used in the Fermilab Tevatron collider for abort-gap clearing, beam-beam compensation, and halo scraping. A beam-beam compensation scheme based upon electron lenses is currently being implemented in the Relativistic Heavy Ion Collider at Brookhaven National Laboratory. This work is in support of a conceptual design of hollow electron beam scraper for the Large Hadron Collider. It also applies to the implementation of nonlinear integrable optics with electron lenses in the Integrable Optics Test Accelerator at Fermilab. We consider the axial asymmetries of the electron beam caused by the bends that are used to inject electrons into the interaction region and to extract them. A distribution of electron macroparticles is deposited on a discrete grid enclosed in a conducting pipe. The electrostatic potential and electric fields are calculated using numerical Poisson solvers. The kicks experienced by the circulating beam are estimated by integrating the electric fields over straight trajectories. These kicks are also provided in the form of interpolated analytical symplectic maps for numerical tracking simulations, which are needed to estimate the effects of the electron lens imperfections on proton lifetimes, emittance growth, and dynamic aperture. We outline a general procedure to calculate the magnitude of the transverse proton kicks, which can then be generalized, if needed, to include further refinements such as the space-charge evolution of the electron beam, magnetic fields generated by the electron current, and longitudinal proton dynamics.
For LCLS-II we estimate the power of radiated wakefields generated in the SRF cavities (including the 3rd harmonic cavities) and in the end transitions. Much of this power will pass through and reflect in the strings of cryomodules that comprise linacs L1, L2, or L3. Presumably, some of it will be absorbed by the higher order mode (HOM) couplers, or by the absorbers at warmer temperatures situated between the cryomodules. We investigate where such power gets generated, but not where it ends up. As such the results can serve as a pessimistic calculation of the extra power that needs to be removed by the cryosystem. Finally, we also estimate---under the assumption that all the wake power ends up in the SRF walls---the wall heating and the extent of Cooper pair breaking in L3, where the bunch is most intense. Note that all calculations here are of single bunch effects; thus resonant interactions are not included.
In these proceedings a novel approach to deal with the beam-induced effects in luminosity measurement is presented. Based on the relativistic kinematics of the collision frame of the Bhabha process, the beam-beam related uncertainties can be reduced to the permille level independently of a precision with which the beam parameters are known. Specific event selection combined with the corrective methods we introduce, leads to the systematic uncertainty from the beam-induced effects to be at a few permille level in the peak region above the 80% of the nominal centre-of-mass energies at ILC.
Since the discovery of electrons more than a century ago, the generation, transport and characterization of electron beams has been an active field of research. Breakthroughs in this field have led to applications as far reaching as cancer treatment, investigation of nanoscale material and dark matter. In this book, we present a snapshot of the photoinjector technology which has contributed to these advances by providing an introduction to the basic theory and engineering of state-of-the-art electron beam sources. Photoinjectors produce relativistic electrons for exciting new devices such as x-ray free electron lasers and the polarized beams for very high energy physics linear colliders. The chapters are written by renowned experts in the field who share their working knowledge of the technologies needed for designing and building photoinjectors. This 335 page book covers the following topics: Photoinjector Theory, Normal Conducting RF Injectors, Superconducting RF Photoinjectors, DC/RF Injectors, Photocathode Theory, Metal Cathodes, Semiconductor Photocathodes for Unpolarized Beams, Cathodes for Polarized Electron Beams, Laser Systems, RF Systems and Beam Diagnostics.
The case of axisymmetric ILC type cavities with titanium helium vessels is investigated. A first order estimate for magnetic field within the SRF current layer is presented. The induced magnetic field is found to be not more than 1.4x10-8 Tesla = 0.14 milligauss for the case of axial symmetry. Magnetic fields due to symmetry breaking effects are discussed.
The goal of this study is to evaluate the impact of the latest ILC beam parameters at the Interaction Point (IP), as specified in the 2013 ILC Technical Design Report (TDR), on beam losses in the extraction line. The previous beam loss evaluation was based on the parameters specified in the 2007 ILC Reference Design Report (RDR). The results of this study are compared to the results obtained in the past for the ``nominal'' and the ``low power'' (low-P) parameter options of the RDR. The initial disrupted beam distribution at IP was generated using Guinea-Pig code, and the beam losses were obtained in tracking simulations using DIMAD. The study is performed for 500 GeV center-of-mass beam energy and the extraction line optics corresponding to the latest final focus optics with L* = 4.5 m, with and without detector solenoid.
The output SASE characteristics of the baseline European XFEL, recently used in the TDRs of scientific instruments and X-ray optics, have been previously optimized assuming uniform undulators without considering the potential of undulator tapering in the SASE regime. Here we demonstrate that the performance of European XFEL sources can be significantly improved without additional hardware. The procedure simply consists in the optimization of the undulator gap configuration for each X-ray beamline. Here we provide a comprehensive description of the soft X-ray photon beam properties as a function of wavelength and bunch charge. Based on nominal parameters for the electron beam, we demonstrate that undulator tapering allows one to achieve up to a tenfold increase in peak power and photon spectral density in the conventional SASE regime. We illustrate this fact for the SASE3 beamline. The FEL code Genesis has been extensively used for these studies. Based on these findings we suggest that the requirements for the SASE3 instrument (SCS, SQS) and for the SASE3 beam transport system be updated.
Increasing the luminosity of relativistic hadron beams is critical for the advancement of nuclear physics. Coherent electron cooling (CEC) promises to cool such beams significantly faster than alternative methods. We present simulations of 40 GeV/nucleon Au+79 ions through the first (modulator) section of a coherent electron cooler. In the modulator, the electron beam copropagates with the ion beam, which perturbs the electron beam density and velocity via anisotropic Debye shielding. In contrast to previous simulations, where the electron density was constant in time and space, here the electron beam has a finite transverse extent, and undergoes focusing by quadrupoles as it passes through the modulator. The peak density in the modulator increases by a factor of 3, as specified by the beam Twiss parameters. The inherently 3D particle and field dynamics is modeled with the parallel VSim framework using a $δ$f PIC algorithm. Physical parameters are taken from the CEC proof-of-principle experiment under development at Brookhaven National Lab.
The rapid cycling synchrotron (RCS) is part of China Spallation Neutron Source (CSNS). The RCS provides 1.6GeV protons with a repetition rate of 25Hz. The RF system in RCS is mainly composed of a ferrite loaded RF cavity, a high power tetrode amplifier, a bias supply of 3300A and a digital low level RF (LLRF) system based on FPGA. The major challenge of the LLRF system is to solve problems caused by rapid frequency sweeping and heavy beam loading effect. This paper will present the design and structure of the LLRF system, and show results of performance tests.
In conventional research on the beam gas coulomb scattering (BGCS), only the related beam lifetime using the analytical method is studied. In this paper, using the PIC-MCC method, we not only simulated the beam lifetime but also explored the effect of BGCS on the beam distribution. In order to better estimate the effect on particle distribution, we study the ultra-low emittance electron beam, here we choose the HeFei Advanced Light Source (HLAS). By counting the lost particles in a certain time, the corresponding beam lifetime we simulated is 5.1078h/14.5507h in x/y, which is very close to the theoretic value (5.0555h /13.7024h in x/y). By counting the lost particles relative to the collided particles, the simulated value of the loss probability of collided particles is 1.3228e-04, which is also very close to the theoretical value (1.3824e-04). Besides, the simulation shows there is a tail in the transverse distribution due to the BGCS. The close match of the simulation with theoretic value in beam lifetime and loss probability indicates our simulation is reliable.
Fringe field becomes important when one requires more accurate modeling of a ring lattice to study the long-term beam dynamics in storage rings and deal with large aperture magnets in high-intensity proton synchrotrons or accumulator rings. In this paper, a simple expression to calculate the tune shifts due to quadrupole fringe fields is derived by using Lie algebra technique. With higher-order terms included, this method is more accurate compared with the linear fringe field model used in SAD code. The method is also applied to a BEPCII lattice. Also based on the Lie algebra technique and an inverse series technique, an equivalent hard-edge model for quadrupoles is proposed, in which the model parameters are derived analytically. The model has the advantages of the direct calculation of the equivalent length and strength of a quadrupole and the easy adaptation when the strength changes. The validity of the model and its simplified version has been checked with a numerical method, and they show very good agreements.
Conventional magnetic transverse focusing in conventional linear accelerators represents a high fraction of their cost and complexity. Both transverse and longitudinal focusing can be obtained from the radio frequency field by using the technique known as Alternating Phase Focusing. The design of suitable sequences has been difficult, without direct theoretical support, inhibiting Alternating Phase Focusing adoption. Synthesis of reported details and new physics and technique result in a new, general method for designing practical Alternating Phase Focusing linear accelerators. Very long sequences with high energy gain factors are demonstrated, motivated by the desire to accelerate particles over a factor of 500-600 energy gain. The method is demonstrated with simple dynamics and no space charge, later incorporation of space charge and more accurate elements is straight forward. Alternating Phase Focusing can now be another practical approach in the linear accelerator designer repertoire. Alternating Phase Focusing can be used in addition to conventional magnetic focusing, and could be useful in minimizing the amount of additional magnetic focusing needed to handle a desired amount of beam current.