We study the modifications of synchrotron radiation of charges in a storage ring as they are cooled. The pair correlation lengths between the charges are manifest in the synchrotron radiation and coherence effects exist for wavelengths longer than the coherence lengths between the charges. Therefore the synchrotron radiation can be used as a diagnostic tool to determine the state (gas, liquid, crystal) of the charged plasma in the storage ring. We show also that the total power of the synchrotron radiation is enormously reduced for crystallized beams. This opens the possibility of accelerating particles to ultra-relativistic energies using small-sized cyclic accelerators.
With respect to a "hot", non-crystallized beam the synchrotron radiation of a cold crystallized beam is considerably modified. We predict suppression of synchrotron radiation emitted by a crystallized beam in a storage ring. We also propose experiments to detect this effect.
We investigate influence on the storage ring beam dynamics of the coherent Synchrotron Radiation (SR) self fields produced by an electron bunch. We show that the maximum energy gain in the RF cavity must far exceed the energy loss of electrons due to the coherent SR.
A laser pulse guided in a curved plasma channel can excite wakefields that steer electrons along an arched trajectory. As the electrons are accelerated along the curved channel, they emit synchrotron radiation. We present simple analytical models and simulations examining laser pulse guiding, wakefield generation, electron steering, and synchrotron emission in curved plasma channels. For experimentally realizable parameters, a ~2 GeV electron emits 0.1 photons per cm with an average photon energy of multiple keV.
Spontaneous and stimulated emission of an electron in the ion channel is studied. The emission processes are studied in the regime of high harmonic generation when the parameter of plasma wiggler strength is large. Like for conventional free electron laser, a synchrotron-like broadband spectrum is generated in this regime. The asymptotic expression for the radiation spectrum of the spontaneous emission is derived. The radiation spectrum emitted from axisymmetric monoenergetic electron beam is analyzed. The gain of ion-channel synchrotron-radiation laser is calculated. Use of laser-produced ion…
We investigate the effect of shear in the flow of charged particle equilibria that are unstable to the Coherent Synchrotron Radiation (CSR) instability. Shear may act to quench this instability because it acts to limit the size of the region with a fixed phase relation between emitters. The results are important for the understanding of astrophysical sources of coherent radiation where shear in the flow is likely.
The electromagnetic radiation of a rotating relativistic electron layers is studied numerically using particle-in-cell simulation. The results of the simulation confirm all relevant scaling properties predicted by theoretical models. These models may turn out to be important for the understanding of the coherent synchrotron radiation (CSR) instability that may occur in systems as diverse as particle accelerators radio pulsars.
A single electron circulating in a storage ring is a very peculiar object. Synchrotron radiation quantum fluctuation causes stohastic process in the synchrotron oscillation of an electron. The radiation from a undulator permits one to obtain discret moments of longitudional electron motion. Experiments with a single electron on on the VEPP-3 optical klystrons are described.
Spin dependencies of the intensity and polarization of the synchrotron radiation of the longitudinally polarized particle performing uniform circular motion in the magnetic field are investigated.
Various effects of intense synchrotron radiation on the performance of particle accelerators, especially for storage rings, are discussed. Following a brief introduction to synchrotron radiation, the basic concepts of heat load, gas load, electron emission, and the countermeasures against these effects are discussed.
We investigate the radiation from a charge rotating around conductors with cylindrical symmetry. First the problem is considered with a charge rotating around a conducting cylinder immersed in a homogeneous medium. The surface charge and current densities induced on the cylinder surface are evaluated. A formula is derived for the spectral-angular density of the radiation intensity. In the second part, we study the radiation for a charge rotating around a diffraction grating on a cylindrical surface with metallic strips parallel to the cylinder axis. The effect of the grating on the radiation i…
The possible use of open-cell conductive foams in high synchrotron radiation particle accelerator beam liners is considered. Available materials and modeling tools are reviewed, potential pros and cons are discussed, and preliminary conclusions are drawn.
Theory and measurement of spatial coherence of synchrotron radiation beams are briefly reviewed. Emphasis is given to simple relationships between electron beam characteristics and far field properties of the light beam.
Below we summarize presentations, discussions and general conclusions of the Workshop session on "Beam Dynamics Issues". Major subjects include effects due to synchrotron radiation (SR), cryogenic loads, electron cloud, impedances, intra-beam scattering (IBS) and beam-beam interactions.
A techniques, describing electron dynamics for magnetic models closed to cyclical accelerators, is developed and applied to the analysis of electromagnetic radiation emitted by charged particles. Formulas for the angular characteristics of synchrotron emission, which take into account the electron vibrations in the lattices of accelerators and storage rings are derived. It is shown that both the degree of photon polarization, as well as the spectral and angular distributions of radiation intensity, exhibit an observable dependence on the vertical betatron oscillations.
Some high-energy experiments have suffered from synchrotron-radiation background. As a measure, we have developed a new calculation method of synchrotron radiation based on a real beam orbit, aiming at quantitative estimations and the construction of a possible alarm system for the background. An explanation and a demonstration of our method are given.
Electron and positron beams in storage-rings self-polarize by emitting spin-flipping synchrotron radiation. If new ultralight particles couple to $e^\pm$, their emission in synchrotron-like radiation would modify the characteristic self-polarization time. We calculate the rate of spin-flipping synchrotron-like radiation in several simplified models, and find that the largest contribution is for an axial-vector. We use polarization time measurements from the Swiss-Light-Source, and SPEAR3 to set new strong limits on ultralight axial-vectors coupled to $e^\pm$.
An interferometer system and an imaging system using visible synchrotron radiation (SR) have been installed in HLS II storage ring. Simulations of these two systems are given using Synchrotron Radiation Workshop(SRW) code. With these two systems, the beam energy spread and the beam emittance can be measured. A detailed description of these two systems and the measurement method is given in this paper. The measurement results of beam size, emittance and energy spread are given at the end.
This paper theoretically proves that an electron storage ring can generate coherent radiation in THz region using a quick kicker magnet and an ac sextupole magnet. When the vertical chromaticity is modulated by the ac sextupole magnet, the vertical beam collective motion excited by the kicker produces a wavy spatial structure after a number of longitudinal oscillation periods. We calculate the radiation spectral distribution from the wavy bunch in Hefei Light Source(HLS). If we reduce electron energy to 400MeV, it can produce extremely strong coherent synchrotron radiation(CSR) at 0.115THz.
Coherent Synchrotron Radiation can severely limit the performance of accelerators designed for high brightness and short bunch length. Examples include light sources based on ERLs or FELs, and bunch compressors for linear colliders. In order to better simulate Coherent Synchrotron Radiation, the established 1-dimensional formalism is extended to work at lower energies, at shorter bunch lengths, and for an arbitrary configuration of multiple bends. Wide vacuum chambers are simulated by means of vertical image charges. This formalism has been implemented in the general beam dynamics code "Bmad" …
Since their discovery in 1896, x-rays have had a profound impact on science, medicine and technology. Here we show that the x-rays from a novel tabletop source of bright coherent synchrotron radiation can be applied to phase contrast imaging of biological specimens, yielding superior image quality and avoiding the need for scarce or expensive conventional sources.
An explicit and remarkably simple one-dimensional integral expression is derived for the mean number $<N>$ of photons emitted per revolution in synchrotron radiation. The familiar high-energy expression $5πα/\sqrt{3(1-β^2)}$, printed repeatedly in the literature, is found to be inaccurate and only truly asymptotic with relative errors of 160%, 82% for $β=0.8$, 0.9, respectively. A new improved high-energy expression for $<N>$ is given.
In order to detect the spin contribution to the synchrotron radiation, the so-called spin light, we propose to compare the characteristics of the radiation emitted by a spin-less charged particle with the huge crop of data regarding the synchrotron light, i.e. the radiation emitted by a particle endowed with a magnetic moment. Helium nuclei are proposed as the lightest stable spin-less charged particles available.
The detailed analysis of angular dependence of the synchrotron radiation (SR) is presented. In particular, we analyze the angular dependence of the integral SR-intensity and peculiarities of the angular dependence of the first harmonics SR. Studying spectral SR-intensities, we have discovered their unexpected angular behavior, completely different from that of the integral SR-intensity. Namely, for any given synchrotron frequency, maxima of the spectral SR-intensities recede from the orbit plane with increasing particle energy. Thus, in contrast with the integral SR-intensity, the spectral one…
We develop a general model of coherent synchrotron radiation (CSR) impedance with shielding provided by two parallel conducting plates. This model allows us to easily reproduce all previously known analytical CSR wakes and to expand the analysis to the situations not explored before. It reduces calculations of the impedance to taking integrals along the trajectory of the beam. New analytical results are derived for the radiation impedance with shielding for the following orbits: a kink, a bending magnet, a wiggler of finite length, and an infinitely long wiggler. All our formulas are benchmark…
The notion of brightness is efficiently conveyed in geometric optics as density of rays in phase space. Wigner has introduced his famous distribution in quantum mechanics as a quasi-probability density of a quantum system in phase space. Naturally, the same formalism can be used to represent light including all the wave phenomena. It provides a natural framework for radiation propagation and optics matching by transferring the familiar `baggage' of accelerator physics (beta-function, emittance, phase space transforms, etc.) to synchrotron radiation. This paper details many of the properties of…
Beam quality preservation during transport of high-brightness electron beams is of general concern in the design of modern accelerators. Methods to manage incoherent synchrotron radiation (ISR) have been in place for decades; as beam brightness has improved coherent synchrotron radiation (CSR) and the microbunching instability (uBI) have emerged as performance limitations. We apply the compensation analysis of diMitri, Cornacchia, and Spampinati - as previously used by Borland - to the design of transport systems for use with low-emittance beams, and find that appropriately configured second o…
Theory predicts that Coherent Synchrotron Radiation (CSR) in electron storage rings should appear in whispering gallery modes. In an idealized model these are resonances of the vacuum chamber that are characterized by their high frequencies and concentration of the field near the outer wall of the chamber. The resonant modes imply a series of sharp peaks in the frequency spectrum of CSR, and very long wake fields which lead to interbunch communication. Theory and experimental evidence for this behavior will be reviewed.
Most studies of Coherent Synchrotron Radiation (CSR) have only considered the radiation from independent dipole magnets. However, in the damping rings of future linear colliders, a large fraction of the radiation power will be emitted in damping wigglers. In this paper, the longitudinal wakefield and impedance due to CSR in a wiggler are derived in the limit of a large wiggler parameter $K$. After an appropriate scaling, the results can be expressed in terms of universal functions, which are independent of $K$. Analytical asymptotic results are obtained for the wakefield in the limit of large …
The horizontal impact parameter profile of synchrotron radiation, for fixed vertical angle of the photon, is calculated. This profile is observed through an astigmatic optical system, horizontally focused on the electron trajectory and vertically focused at infinity. It is the product of the usual angular distribution of synchrotron radiation, which depends on the vertical angle $ψ$, and the profile function of a caustic staying at distance $\bcl = (γ^{-2} + ψ^2) \RB/2 $ from the orbit circle, $\RB$ being the bending radius and $γ$ the Lorentz factor. The {\it classical impact parameter} $\bcl…
Spontaneous formation of spatial structures (patterns) occurs in various contexts, ranging from sand dunes and rogue wave formation, to traffic jams. These last decades, very practical reasons also led to studies of pattern formation in relativistic electron bunches used in synchrotron radiation light sources. As the main motivation, the patterns which spontaneously appear during an instability increase the terahertz radiation power by factors exceeding 10000. However the irregularity of these patterns largely prevented applications of this powerful source. Here we show how to make the spatio-…
A compact damping ring with limited circumference of about 160 m is proposed for producing kilowatt-level coherent EUV radiation. The electron bunch in the ring is modulated by a 257nm wavelength laser with the help of the angular dispersion induced micro-bunching method [C. Feng and Z. Zhao, Sci. Rep. 7, 4724 (2017)]. Coherent radiation at 13.5 nm with an average power of about 2.5 kW can be achieved with the state-of-the-art accelerator and laser technologies.
The classical description of synchrotron radiation fails at large Lorentz factors, $γ$, for relativistic electrons crossing strong transverse magnetic fields $B$. In the rest frame of the electron this field is comparable to the so-called critical field $B_0 = 4.414\cdot10^9$ T. For $χ= γB/B_0 \simeq 1$ quantum corrections are essential for the description of synchrotron radiation to conserve energy. With electrons of energies 10-150 GeV penetrating a germanium single crystal along the $<110>$ axis, we have experimentally investigated the transition from the regime where classical synchrotron …
Electron storage rings used for the production of synchrotron radiation (SR) have an output photon brightness that is limited by the equilibrium beam emittance. By using interleaved injection and ejection of bunches from a source with repetition rate greater than 1 kHz, we show that it is practicable to overcome this limit in rings of energy ~1 GeV. Sufficiently short kicker pulse lengths enable effective currents of many milliamperes, which can deliver a significant flux of diffraction-limited soft X-ray photons. Thus, either existing SR facilities may be adapted for non-equilibrium operation…
The proposed High-Energy LHC project presents an unusual combination of strong synchrotron radiation (SR) damping and intrabeam scattering (IBS), which is not seen in present-day hadron colliders. The subject of investigation reported in this paper was the simulation of beam-beam effect for the HE-LHC parameters. Parameters of SR and IBS are calculated, and the luminosity evolution is simulated in the absence of beambeam interaction. Then, a weak-strong numerical simulation is used to predict the effect of beam-beam interaction on particle losses and emittance evolution.
Coherent synchrotron radiation (CSR) occurs when short bunches travel on strongly bent trajectories. Its effects on high-quality beams can be severe and are well understood qualitatively. For quantitative results, however, one has to rely on numerical methods. There exist several simulation codes utilizing different approaches. We describe in some detail the code TraFiC4 developed at DESY for design and analysis purposes, which approaches the problem from first principles and solves the equations of motion either perturbatively or self-consistently. We present some calculational results and co…
A recent "beam splitting" experiment at LCLS apparently demonstrated that after a microbunched electron beam is kicked on a large angle compared to the divergence of the FEL radiation, the microbunching wave front is readjusted along the new direction of motion of the kicked beam. Therefore, coherent radiation from an undulator placed after the kicker is emitted along the kicked direction without suppression. This strong emission of coherent undulator radiation in the kicked direction cannot be explained in the framework of conventional synchrotron radiation theory. In a previous paper we expl…
Laser wakefield accelerators have emerged as a promising candidate for compact synchrotron radiation and even x-ray free electron lasers. Today, to make the electrons emit electromagnetic radiation, the trajectories of laser wakefield accelerated electrons are deflected by transverse wakefield, counter-propagating laser field or external permanent magnet insertion device. Here, we propose a novel type of undulator which has a few hundred microns of period and tens of Tesla of magnetic field. The undulator consists of a bifilar capacitor-coil target which sustains strong discharge current that …
A novel method for generating GigaGauss solenoidal field in laser-plasma bubble, using screw-shaped laser pulses, has been recently presented in arXiv:1604.01259 [physics.plasm-ph]. Such magnetic fields enable fast synchrotron radiation cooling of the beam emittance of laser-plasma accelerated leptons. This recent finding opens a novel approach for design of laser-plasma FELs or colliders, where the acceleration stages are interleaved with laser-plasma emittance cooling stages. In this concept paper we present an outline of how a staged plasma-acceleration FEL could look like and discuss furth…
If we try to measure the backward optical diffraction radiation (BODR) of high energy electrons from a conductive slit or a semi infinitive plate, the electron beam will pass thru the bending or steering magnets or magnet lenses before striking the target. The synchrotron radiation (SR) from these magnets can obscure the BODR measurements. An analysis of the properties of SR from these magnets is in this paper presented. A model based on the modified Lenar Wikherd potentials was created, and the SR angular distribution from relativistic electrons in bending and steering magnets for different c…
Next generation accelerators will require a high current, low emittance beam with a low energy spread. Such accelerators will employ advanced beam conditioning systems such as emittance exchangers to manipulate high brightness beams. One of the goals of the Fermilab A0 photoinjector is to investigate the transverse to longitudinal emittance exchange principle. Coherent synchrotron radiation could limit high current operation of the emittance exchanger. In this paper, we report on the preliminary experimental and simulation study of the coherent synchroton radiation (CSR) in the emittance excha…
In a lepton storage ring of very high energy (e.g. in the $e^+e^-$ Higgs factory) synchrotron radiation from quadrupoles constrains transverse dynamic aperture even in the absence of any magnetic nonlinearities. This was observed in tracking for LEP and the Future Circular $e^+e^-$ Collider (FCC-ee). Here we describe a new mechanism of instability created by modulation of the particle energy at the double betatron frequency by synchrotron radiation in the quadrupoles. Energy modulation varies transverse focusing strength at the same frequency and creates a parametric resonance of the betatron …
Generation of extreme bright coherent synchrotron radiation in a short wavelength range is of remarkable interest in the synchrotron light source community. In this paper, a novel technique is adopted to produce the coherent radiation which uses an angular dispersion to enhance the micro-bunch by a tiny amplitude of energy modulation. This scheme can be inserted in a long straight section of a storage ring. A lattice design of an extreme-low emittance storage ring with 3.5 GeV energy is presented in this paper, which employs a higher order achromat (HOA) concept. We show the design results for…
The study presented here was initiated by a discussion to investigate the possibility of using synchrotron radiation as a source for the Next Generation Lithography (NGL) based on the EUV-concept (Extreme Ultra-Violet; here 13.5 nm or 11.3 nm radiation, respectively). The requirements are: 50 W, 2% bandwidth and minimal power outside this bandwidth. Three options were investigated. The first two deal with radiation from bending magnets and undulators. The results confirm the earlier work by Oxfords Instrument and others that these light-sources lack in-band power while emitting excessive out-o…
In KEKB, synchrotron radiation interferometers (SRMs) are used for measuring the transverse beam sizes. There is also a tool for enlarging the vertical beam size intentionally by making an asymmetric bump, called an ``iSize'' bump, at one of the strongest non-interleaved sextupole magnets in each KEKB ring. The calibrations of the SRMs were checked by comparing the measured vertical beam sizes with those calculated using the computer code ``SAD''. The obtained correction factors are 1.000$\pm$0.045 for HER and 0.971$\pm$0.060 for LER, which are consistent with the calibration factors of SRMs\c…
This work contains a systematic treatment of single particle Synchrotron Radiation and some application to realistic beams with given cross section area, divergence and energy spread. Standard theory relies on several approximations whose applicability limits and accuracy are often forgotten. We begin remarking that on the one hand, a paraxial approximation can always be applied without loss of generality and with ultra relativistic accuracy. On the other hand, dominance of the acceleration field over the velocity part in the Lienard-Wiechert expressions is not always granted and constitutes a…
In this paper we discuss a method for nondestructive measurements of the longitudinal profile of sub-picosecond electron bunches for X-Ray Free Electron Lasers (XFELs). The method is based on the detection of the Coherent Synchrotron Radiation (CSR) spectrum produced by a bunch passing a dipole magnet system. This work also contains a systematic treatment of synchrotron radiation theory which lies at the basis of CSR. Standard theory of synchrotron radiation uses several approximations whose applicability limits are often forgotten: here we present a systematic discussion about these assumptio…
Coherent Synchrotron Radiation has been studied effectively using a 1-dimensional model for the charge distribution in the realm of small angle approximations and high energies. Here we use Jefimenko's form of Maxwell's equations, without such approximations, to calculate the exact wake-fields due to this effect in multiple bends and drifts. It has been shown before that the influence of a drift can propagate well into a subsequent bend. We show, for reasonable parameters, that the influence of a previous bend can also propagate well into a subsequent bend, and that this is especially importan…
At the Metrology Light Source (MLS), the compact electron storage ring of the Physikalisch-Technische Bundesanstalt (PTB) with a circumference of 48\,m, a specific operation mode with two stable closed orbits for stored electrons was realized by transverse resonance island buckets. One of these orbits is closing only after three turns. In combination with single-bunch operation, the new mode was applied for electron time-of-flight spectroscopy with an interval of the synchrotron radiation pulses which is three times the revolution period at the MLS of 160\,ns. The achievement is of significant…
Coherent Synchrotron Radiation (CSR) can play an important role by not only increasing the energy spread and emittance of a beam, but also leading to a potential instability. Previous studies of the CSR induced longitudinal instability were carried out for the CSR impedance due to dipole magnets. However, many storage rings include long wigglers where a large fraction of the synchrotron radiation is emitted. This includes high-luminosity factories such as DAPHNE, PEP-II, KEK-B, and CESR-C as well as the damping rings of future linear colliders. In this paper, the instability due to the CSR imp…
We investigate the electromagnetic fields generated by a charged particle rotating inside a dielectric cylinder immersed into a homogeneous medium. The expressions for the bound modes of the radiation field are derived in both interior and exterior regions. The radiation intensity for the modes propagating inside the cylinder is evaluated by using two different ways: by evaluating the work done by the radiation field on the charge and by evaluating the energy flux through the cross-section of the cylinder. The relation between these two quantities is discussed. We investigate the relative cont…
In this paper we analyze the image formation problem for undulator radiation through an optical system, accounting for the influence of the electron beam emittance. On the one hand, image formation with Synchrotron Radiation is governed by the laws of Statistical Optics. On the other hand, the widely used Gaussian-Shell model cannot be applied to describe the coherence properties of X-ray beams from third generation Synchrotron Radiation sources. As a result, a more rigorous analysis of coherence properties is required. We propose a technique to explicitly calculate the cross-spectral density …
Photon-stimulated desorption (PSD) is a process of interest for the two seemingly unrelated topics of accelerator vacuum dynamics and astrochemistry. Here we present an approach to studying PSD of interstellar ice analogs, i.e. condensed films of molecules of astrophysical interest at cryogenic temperatures, using synchrotron radiation. We present results obtained in the VUV range on various pure and layered ices, focusing on elucidating the desorption mechanisms, and results in the X-ray range for H$_2$O.
Synchrotron radiation has been used for many years as a beam diagnostic at electron accelerators. It is not normally associated with proton accelerators as the intensity of the radiation is too weak to make detection practical. However, if one utilizes the radiation originating near the edge of a bending magnet, or from a short magnet, the rapidly changing magnetic field serves to enhance the wavelengths shorter than the cutoff wavelength, which for more recent high energy proton accelerators such as Fermilab's Tevatron, tends to be visible light. This paper discusses the implementation at the…
