High Energy Electron Storage Rings Research Articles

Alpha-buckets in High Energy Electron Storage Rings (Review of Existing Experiments and Feasibility Studies for Future Developments)

Electron storage rings operating at high energies have proven to be invaluable source of synchrotron radiation. Two and even three simultaneous beams of particles have been observed at different light source facilities worldwide. So called alpha-buckets were studied at Metrological Light Source (MLS) in Berlin (Germany), SOLEIL facility in France, DIAMOND light source in UK, NSLS ring in Brookhaven (USA). It is widely recognized that alpha buckets are general phenomena which is not restricted to a certain storage ring. However, earlier measurements showed essential limitations on parameters of alpha-buckets, strong dependence on high order (sextupole and octupoles) magnetic field imperfections and associated fast decay of electron current as well as reduced life time. Also a rising relevance of high order non-linear longitudinal beam dynamics is associated with new generation of diffraction limited light sources (DLSR) approaches, which all suffer nonlinear momentum compaction factor. A large variety of future generation electron synchrotrons require a comprehensive investigation of the physical processes involved into the operation of such rings. In this paper, we present review of high order non-linear longitudinal beam dynamics based on the longitudinal equations of motion and Hamiltonian expanded to a high order of the momentum compaction factor. Roots of the third order equation with a free term are derived in a form suitable for analytical estimations. The momentum independent term of orbit lengthening due to particle transverse excursions is estimated and taken into account. The results from simulations were benchmarked against existing experiments at the Karlsruhe Research Accelerator (KARA), SOLEIL and MLS rings. Parameters of three simultaneous beams and alpha buckets at MLS and SOLEIL have been reproduced with high accuracy. General conditions for stable operation of alpha buckets are presented. Based on analytical formulas and computer simulations, studies of longitudinal motion at KARA have been performed with an objective to estimate feasibility of filling and storing of beam in α-buckets. A Computer model was used to describe the behavior and dynamics of simultaneous beams in the KARA storage ring

Reevaluation of spin-orbit dynamics of polarized e+e− beams in high energy circular accelerators and storage rings: An approach based on a Bloch equation

We give an overview of our current/future analytical and numerical work on the spin polarization in high-energy electron storage rings. Our goal is to study the possibility of polarization for the CEPC and FCC-ee. Our work is based on the so-called Bloch equation for the polarization density introduced by Derbenev and Kondratenko in 1975. We also give an outline of the standard approach, the latter being based on the Derbenev–Kondratenko formulas.

The Bloch equation for spin dynamics in electron storage rings: Computational and theoretical aspects

In this paper, we describe our work on spin polarization in high-energy electron storage rings which we base on the Full Bloch equation (FBE) for the polarization density and which aims towards the [Formula: see text] option of the proposed Future Circular Collider (FCC-ee) and the proposed Circular Electron Positron Collider (CEPC). The FBE takes into account non spin-flip and spin-flip effects due to synchrotron radiation including the spin-diffusion effects and the Sokolov–Ternov effect with its Baier–Katkov generalization as well as the kinetic-polarization effect. This mathematical model is an alternative to the standard mathematical model based on the Derbenev–Kondratenko formulas. For our numerical and analytical studies of the FBE, we develop an approximation to the latter to obtain an effective FBE. This is accomplished by finding a third mathematical model based on a system of stochastic differential equations (SDEs) underlying the FBE and by approximating that system via the method of averaging from perturbative ODE theory. We also give an overview of our algorithm for numerically integrating the effective FBE. This discretizes the phase space using spectral methods and discretizes time via the additive Runge–Kutta (ARK) method which is a high-order semi-implicit method. We also discuss the relevance of the third mathematical model for spin tracking.

Gas bremsstrahlung shielding calculation for first optic enclosure of ILSF XPD beamline

Gas bremsstrahlung is generated in high energy electron storage ring and accompanies the synchrotron radiation into the beamlines, where both strike the various components of the beamline. In this paper, radiation shielding calculations for secondary gas bremsstrahlung are performed for the First Optics Enclosure (FOE) of X-ray powder diffraction (XPD) beamline of the Iranian Light Source Facility. Dose equivalent rate (DER) calculations are accomplished using FLUKA Monte Carlo code. A comprehensive study of DER distribution at the back wall, sides and roof are given.

Gas bremsstrahlung shielding calculation for first optic enclosure of ILSF medical beamline

Gas bremsstrahlung is generated in high energy electron storage ring accompanies the synchrotron radiation into the beamlines and strike the various components of the beamline. In this paper, radiation shielding calculation for secondary gas bremsstrahlung is performed for the first optics enclosure (FOE) of medical beamline of the Iranian Light Source Facility (ILSF). Dose equivalent rate (DER) calculation is accomplished using FLUKA Monte Carlo code. A comprehensive study of DER distribution at the back wall, sides and roof is given.

電子加速器を利用した研究の産業技術への橋渡し

Laser Compton photon beams generated by a high-energy electron storage ring have energy in the gamma-ray range. X-ray radiography for industrial products using the laser Compton photon beam is expected to show good spatial and density resolutions, because of its monochromaticity and good beam property. A radiography and computerized tomography system was built using AIST's TERAS electron storage ring. The performance of the system was examined. A summary of the development process is outlined to figure out the general methodology for translational research.

Monte Carlo and analytical calculations for characterization of gas bremsstrahlung in ILSF insertion devices

Gas bremsstrahlung is generated in high energy electron storage rings through interaction of the electron beam with the residual gas molecules in vacuum chamber. In this paper, Monte Carlo calculation has been performed to evaluate radiation hazard due to gas bremsstrahlung in the Iranian Light Source Facility (ILSF) insertion devices. Shutter/stopper dimensions is determined and dose rate from the photoneutrons via the giant resonance photonuclear reaction which takes place inside the shutter/stopper is also obtained. Some other characteristics of gas bremsstrahlung such as photon fluence, energy spectrum, angular distribution and equivalent dose in tissue equivalent phantom have also been investigated by FLUKA Monte Carlo code.

Synchrotron oscillation effects for spin resonances driven by a localized oscillating rf magnetic field

I derive a generalized tune modulation parameter, to take into account time-of-arrival effects for synchrotron tune modulation of spin resonances driven by a localized rf solenoid or rf dipole, i.e. a time-dependent oscillating magnetic field. I show that the extra effects are negligible for high energy electron storage rings, but they might not be negligible for low or medium energy hadron storage rings. I show that alternative interpretations are possible for some previously published data of bunched stored polarized hadron beams. I suggest benchmark tests for new experimental measurements.

Transient bunch compression using pulsed phase modulation in high-energy electron storage rings

A method for producing short electron bunches in an electron storage ring using pulsed phase modulation has been demonstrated. A simple theoretical model was validated using the particle tracking code elegant, and the bunch compression process was observed experimentally in the Advanced Photon Source storage ring using a visible light streak camera. Compression to 54% of the initial bunch length was achieved.

Study of possibilities for a spin flip in high energy electron ring HERA

In a high energy electron ring the spins of electrons become spontaneously polarized via the emission of spin-flip synchrotron radiation. By employing a radio frequency radial dipole field kicker, particle spin directions can be rotated slowly over many turns. A model which couples three dimensional spin motion and longitudinal particle motion was constructed to describe nonequilibrium spin dynamics in high energy electron storage rings. The effects of a stochastic synchrotron radiation on the orbital motion in the accelerator synchrotron plane and its influence on the spin motion are studied. The main contributions to the spin motion, the synchrotron oscillations and the stochastic synchrotron radiation, have different influence on the spin polarization reversal in different regions of the parameter space. The results indicate that polarization reversal might be obtained in high energy electron storage rings with a significant noise even with relatively small strengths of a perturbing magnetic field. The only experimental datum available agrees with the model prediction, however further experimental data would be necessary to validate the model.

Properties of the electron cloud in a high-energy positron and electron storage ring

Low-energy, background electrons are ubiquitous in high-energy particle accelerators. Under certain conditions, interactions between this electron cloud and the high-energy beam can give rise to numerous effects that can seriously degrade the accelerator performance. These effects range from vacuum degradation to collective beam instabilities and emittance blowup. Although electron-cloud effects were first observed two decades ago in a few proton storage rings, they have in recent years been widely observed and intensely studied in positron and proton rings. Electron-cloud diagnostics developed at the Advanced Photon Source enabled for the first time detailed, direct characterization of the electron-cloud properties in a positron and electron storage ring. From in situ measurements of the electron flux and energy distribution at the vacuum chamber wall, electron-cloud production mechanisms and details of the beam-cloud interaction can be inferred. A significant longitudinal variation of the electron cloud is also observed, due primarily to geometrical details of the vacuum chamber. Such experimental data can be used to provide realistic limits on key input parameters in modeling efforts, leading ultimately to greater confidence in predicting electron-cloud effects in future accelerators.

Development of an asymmetric power divider for a high-power RF distribution system

We have developed a radio-frequency (RF) power divider that is used for an RF distribution system in high-energy electron storage rings. This power divider has four waveguide ports, and it can split a high RF power by a ratio of 1:2 at an operating frequency of about 508.6 MHz. Since other properties are very similar to those of a magic-T it is very suitable for accelerator applications. By combining this device with a conventional magic-T, one can design an RF distribution system in which three cavities are driven by a single klystron. The design procedure of the power divider, a low-power measurement, and a high-power test result are presented.

Refractive lenses as a beam diagnostics tool for high-energy synchrotron radiation

Parabolic compound refractive lenses (CRLs) for hard X rays have been used to image the electron beam at undulator and bending-magnet beamlines at the ESRF. The measurements yield the shape and size of the synchrotron radiation source, and show that CRLs with paraboloid surface shape can be used as a beam diagnostics tool at high-energy electron storage rings. The optical resolution of the imaging setup can be as small as 4 μm . This is smaller than typical values of the electron beam size in third-generation synchrotron sources. We report measurements at two ESRF beamlines and resolution calculations taking into account the properties of synchrotron radiation and the transmission characteristics of the CRLs used.

Measurement of absorbed dose by 7-GeV bremsstrahlung in a PMMA phantom

High-energy electron storage rings generate energetic bremsstrahlung photons through radiative interaction of the particle beam with the residual gas molecules and other components inside the storage ring. At synchrotron radiation facilities, where beamlines are channeled out of the storage ring, a continuous bremsstrahlung spectrum, with a maximum energy of the stored particle beam, will be present. At the advanced photon source (APS), where the stored beam energy is 7 GeV, bremsstrahlung generated in the straight sections of the insertion device beamlines, which are a total of 15.38 m in length, can be significant. The contribution from each bremsstrahlung interaction adds up to produce a narrow mono-directional bremsstrahlung beam that comes down through the insertion device beamlines. The resulting absorbed dose distributions by this radiation in a 300 mm×300 mm×300 mm tissue substitute cube phantom were measured with LiF:Mg,Ti (TLD-700) thermoluminescent dosemeters. The normalized absorbed dose, in a cross-sectional area of 100 mm 2 at a depth of 150 mm of the PMMA phantom, was measured as 3.3×10 6 mGy h −1W −1 for 7-GeV bremsstrahlung spectrum.

Dose measurements of bremsstrahlung-produced neutrons from thick targets

Photons of sufficiently high energies ( E γ ≥5–15 MeV) can produce neutrons by means of photonuclear interactions. Bremsstrahlung from high energy electron storage rings, which have an energy range of zero to the maximum energy of the particle beam, can interact with beamline components like beam stops and collimators generating photoneutrons of varying energies. This paper presents the results of simultaneous measurements of bremsstrahlung power and corresponding photoneutron dose equivalent rate at the insertion device beamlines of the Advanced Photon Source, using a lead-glass calorimeter and an Andersson–Braun remmeter. Targets made of Fe, Cu, W, and Pb are placed in the bremsstrahlung beam inside the first optics enclosure of the insertion device beamlines. The photoneutron dose equivalent rates, normalized to bremsstrahlung power, beam current, and storage ring pressure, are measured for the four targets. The photoneutron dose equivalent rates, normalized to the bremsstrahlung power and corrected for systematic variations, are given as 2.2±0.5 rem/h/W for Fe,3.0±0.5 rem/h/W for Cu, 3.8±0.5 rem/h/W for W, and 3.7±0.8 rem/h/W for Pb targets, at a distance of 0.8 m perpendicular from the target center.

Proposal of a high-field superconducting wiggler for a slow positron source at SPring-8.

A low-energy positron beam is a unique probe of materials. In high-energy electron and positron storage rings it is possible to generate intense synchrotron radiation with a photon energy of 1-3 MeV by installing a high-field (8-10 T) superconducting wiggler. High-energy photons are converted to low-energy positrons by using a suitable target-moderator system. For an 8 GeV electron storage ring at a beam current of 100 mA, final yields are estimated to be about 10(8)-10(10) slow-e(+) s(-1) or larger depending on the moderation efficiency, with the size of the positron source 10(1)-10(2) cm(2). In the present work a wiggler magnetic system of 10 T is proposed. The main parameters of the superconducting wiggler are presented.

An estimate of gas desorption in the damping rings of the next linear collider

We express the gas desorption in a high-energy electron or positron storage ring in terms of the photoemission and the electron-induced gas-desorption yields of the vacuum-chamber material. The derived expression is used to estimate the gas desorption in the two main damping rings of the Next Linear Collider (NLC) and, in particular, its dependence on the height of the slots which connect the beam pipe proper to an antechamber.

Production of Intense Low-Energy Positron Beams with Synchrotron Radiation

A low-energy positron beam is a unique probe of Fermi surfaces, defects, surfaces and interfaces. In high-energy electron and positron storage rings (E > 6 GeV) it is possible to generate intense synchrotron radiation with 1-3 MeV photons by installing a high-field superconducting wiggler. The strength of the wiggler should be ~8-12 T. High-energy photons are emitted from the wiggler and converted to low-energy positrons by using a suitable target-moderator system. For an 8 GeV electron storage ring at a beam current of 100 mA, final yields are estimated to be ~10(10)-10(12) (slow-e(+) s(-1)) with the size of positron source ~10(2)-10(3) cm(2). The possibility of increasing the brightness of the low-energy positron beam is discussed. Advantages of using synchrotron radiation for producing positrons are pointed out. The effect of a superconducting wiggler on the stored electron beam is also discussed.

The first achievement of longitudinal spin polarization in a high energy electron storage ring

A pair of spin rotators has been installed in the electron ring of HERA. Longitudinal spin polarizations up to 65% have been reached reproducibly during dedicated measurement time. This is the first time that longitudinal spin polarization has been produced in a high energy electron storage ring.

A compact radiation source for digital subtractive angiography

Beam requirements for 33 keV radiation used in digital subtraction angiography have been established through extended experimentation first at Stanford and later at the National Synchrotron Light Source in Brookhaven. So far research and development of this medical procedure to image coronary blood vessels have been undertaken on large high energy electron storage rings. With progress in this diagnostic procedure, it is interesting to look for an optimum concept for providing a 33 keV radiation source which would fit into the environment of a hospital. A variety of competing effects and technologies to produce 33 keV radiation are available, but none of these processes provides the combination of sufficient photon flux and monochromaticity except for synchrotron radiation from an electron storage ring. The conceptual design of a compact storage ring optimized to fit into a hospital environment and producing sufficient 33 keV radiation for digital subtraction radiography will be discussed.