Large Storage Rings Research Articles

Toward a diffraction limited light source

This paper introduces a storage ring lattice design for synchrotron radiation sources which fulfills all the required features for the realization of a diffraction limited light source. Insertion devices half gaps of 2.5 mm are assumed and enabled by the design of dedicated straight sections. The use of long straight sections is possible for such a lattice and led to the definition of a set of transparency conditions used to minimize the effect of such insertions for on- and off- energy beam dynamics. The design proposed enables an extremely long Touschek lifetime and beam accumulation. A real case study will be shown for large circumference storage ring upgrade lattices.17 MoreReceived 17 October 2022Accepted 17 January 2023DOI:https://doi.org/10.1103/PhysRevAccelBeams.26.021601Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasBeam dynamicsBeam trackingCollimationHigher order beam dynamicsLattices in beam opticsSingle-particle dynamicsAccelerators & Beams

Time-of-flight mass spectrographs of high mass resolving power

The masses of charged atoms and molecules were first investigated by laterally dispersive sector field mass analyzers, which early on already achieved high mass resolving powers. Equally, high mass resolving powers were achieved by time-of-flight mass analyzers during the last decades. These measurements became possible when fast and precise electronic circuitries became available. Such techniques have been developed and used extensively for the mass analysis of short-lived nuclei, whose mass values reveal insight in processes that describe the formation of elements in star explosions. Precise mass determinations of short-lived ions have been performed for energetic ions in large accelerator storage rings as well as for low-energy ions in time-of-flight mass spectrographs with long flight paths. Similarly, precise mass measurements can also be performed for molecular ions that help to reveal the structure of molecules. In case of very high mass resolving powers, the mass determination of molecular ions can be so high that the measured ion mass directly reveals the molecule’s sum formula.

Design considerations for a new beamline for standard EXAFS at a high-energy low-emittance storage ring

P65 is a new EXAFS beamline to be built at the PETRA III storage ring at DESY in Hamburg. It will mainly be used for standard EXAFS applications with a relatively large beam and moderate flux density. While the beamline optics will be similar to many other standard EXAFS beamlines, the insertion device at such a large high-energy storage ring with low emittance like PETRA III will need special attention. This paper discusses the main design considerations for the construction of such a beamline at a 6 GeV storage ring with an emittance of 1 nm rad.

Steady-state analysis of short-wavelength, high-gain FELs in a large storage ring

Storage ring FELs have operated successfully in the low-gain regime using optical cavities. Discussions of a high-gain FEL in a storage ring typically involve a special bypass to decouple the FEL interaction from the storage ring dynamics. In this paper, we investigate the coupled dynamics of a high-gain FEL in a large storage ring such as PEP and analyze the equilibrium solution. We show that an FEL in the EUV and soft X-ray regimes can be integrated into a very bright storage ring and potentially provides three orders of magnitude improvement in the average brightness at these radiation wavelengths. We also discuss possibilities of seeding with HHG sources to obtain ultra-short, high-peak power EUV and soft X-ray pulses.

Effect of coupled-bunch modes on the longitudinal feedback system

The Pedersen analysis of the low-level rf feedback system assumes that all bunches oscillate in phase which corresponds to the lowest coupled-bunch mode. This analysis is extended here to take into account all other coupled-bunch modes what might be important for the strongly detuned cavities in large storage rings such as PEP-II.

Neutrino-nucleus interaction rates at a low-energyβ-beam facility

We compute the neutrino detection rates to be expected at a low-energy beta-beam facility. We consider various nuclei as neutrino detectors and compare the case of a small versus large storage ring.

Ion Coulomb crystals: a tool for studying ion processes

Ion processes can be studied by a wide variety of experimental setups ranging from small ion trap devises to large storage rings. In Penning as well as Paul (rf) traps, the effective oscillation frequencies of trapped particles have, e.g., extensively been used to gain information of the charge to mass ratio of produced atomic and molecular ions. For such investigations, space charges due to the simultaneous presence of multiple ions, is a limiting factor, and hence low density or single particle experiments are preferred. The purpose of the present article is to discuss the prospects of using traps in the opposite regime where space charges dominate and so-called ion Coulomb crystals form (at temperatures about ∼10 mK). The experimental results presented below show that in this regime, differences in single particle oscillation frequencies of simultaneously trapped ions lead to a spatial segregation of the ion species which can be used as means to study a large variety of ion processes. Since the detection relies generally on observations of changes in the spatial structure of the Coulomb crystals formed by the cold, trapped ions, it can often be non-destructive, i.e., the product ions of a certain process will stay trapped and be available for further experimentations. It is the intention of the present article to discuss, via some examples, the usefulness of ion Coulomb crystals as a tool in investigations of ion processes more than it is the aim to provide new data.

POLYNOMIAL MAP FACTORIZATION OF SYMPLECTIC MAPS

Long-term stability studies of nonlinear Hamiltonian systems require symplectic integration algorithms which are both fast and accurate. In this paper, we study a symplectic integration method wherein the symplectic map representing the Hamiltonian system is refactorized using polynomial symplectic maps. This method is analyzed for the three degree of freedom case. Finally, we apply this algorithm to study a large particle storage ring.

Bose-Einstein condensates in 'giant' toroidal magnetic traps

The experimental realization of gaseous Bose—Einstein condensation (BEC) in 1995 sparked considerable interest in this intriguing quantum fluid. Here, progress towards the development of an 87Rb BEC experiment in a large (≈ 10cm diameter) toroidal storage ring is reported. A BEC will be formed at a localized region within the toroidal magnetic trap, from whence it can be launched around the torus. The benefits of the system are manifold, as it should readily enable detailed investigations of persistent currents, Josephson effects, phase fluctuations and high-precision Sagnac or gravitational interferometry.

Single-particle dynamics in particle storage rings with integrable polynomial factorization maps

A six-dimensional symplectic tracking code based on the concept of integrable polynomial factorization (IPF) maps has been developed for the study of beam dynamics in large storage rings. To examine the accuracy of the IPF maps, comparison studies on beam dynamics between the IPF maps and the original system have been conducted with two sample lattices: a lattice containing one sextupole kick that is otherwise linear and the LHC (Large Hadron Collider) collision lattice. It was found that the errors in the $n\mathrm{th}$-order IPF map scale as the $(n+1)\mathrm{th}$ power of phase-space amplitude. As the order of the map is increased, the difference between the original system and its IPF map can thus be reduced to be as small as desired. A study of phase-space portraits showed that the IPF map precisely reproduces the resonance structure of the original system even in the phase-space region where the system is quite nonlinear. The tracking study for the LHC showed that the IPF map accurately predicts the same dynamic aperture as does element-by-element tracking. Our results suggest that the IPF map is a reliable model for the study of long-term behavior of beam particles in large storage rings.

Feedback system for elimination of the transverse mode coupling instability

Transverse mode coupling (TMC) instability [1] is one of the major limitations of a single bunch current in large storage rings. This paper is devoted to a theoretical analysis of the effect of transverse feedback systems on TMC thresholds. It presents a space-time formalism for a hollow beam model and time-independent collective interaction. Then, in the framework of a simplified model, the principle of eliminating the TMC by means of a special transverse feedback system is outlined. This approach is then generalized in the form of an algorithm.

Integrable polynomial factorization for symplectic systems.

It has been shown that an analytic symplectic map can be directly converted into a product of Lie transformations in the form of integrable polynomial factorization with the desired accuracy. A map in the form of integrable polynomial factorization is exactly symplectic and easy to evaluate exactly. Error involved in the integrable polynomial factorization has been studied with the case of the H\'enon map. The results suggest that the map in the form of integrable polynomial factorization is a reliable and convenient model for the study of the long-term behavior of a symplectic system such as a large storage ring.

Short wavelength FELs on large storage rings

Abstract The use of a large-circumference, high-energy, electron-positron collider such as PEP, TRISTAN or PETRA to drive a free-electron laser (FEL), producing high levels of coherent power at short wavelengths around 40 A is explored. We consider self-amplified spontaneous emission (SASE), in which electron bunches with low emittance, high peak current and small energy spread radiate coherently in a single pass through a long undulator. As the electron beam passes down the undulator, its interaction with the increasingly intense spontaneous radiation causes a bunch density modulation at the optical wavelength, resulting in stimulated emission and exponential growth of coherent power in a single pass. The need for optical-cavity mirrors, which place a lower limit on the wavelength of a conventional FEL oscillator, is avoided. Various combinations of electron-beam and undulator parameters, as well as special undulator designs, are discussed. Saturation and high peak, in-band, coherent power (460 MW) are possible with a 67 m, hybrid permanent-magnet undulator in a ring bypass. A 100 m, cusp-field undulator can achieve high average, in-band, coherent power (0.25 W) in the main ring. The existing, 25.6 m. Paladin undulator at LLNL, with the addition of optical-klystron dispersive sections, is considered for both peak and average power.

Review of accelerator magnet design in the world

It is pointed out that the construction of large particle accelerators and storage rings requires the design and fabrication of large numbers of bending, focusing, and correction magnets. Normal conducting iron yoke magnets are standard for low fields. Two designs representing efforts for manufacturing cost reduction are discussed. Emphasis is placed on superconducting magnets necessary for high fields. Many details of the well-established cos theta one or two layer coil design using NbTi superconductor are presented. Peculiarities in the use of Nb/sub 3/Sn superconducting material are mentioned. Examples of alternative superconducting magnet designs are given. Finally, the performance of HERA (Hadron-Electron Ring Accelerator) magnets produced in quantity by industry is presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The vacuum system of the HERA electron storage ring

The 6.3 km long vacuum system for electrons of the new large storage ring HERA 1 at Hamburg consists of about 1400 components having lengths between 0.14 and 12m. These components are mainly made by brazing variously shaped tubes of the copper alloy CuSn 2 instead of using the common aluminium alloy extrusions. This copper alloy absorbs synchrotron light more efficiently than aluminium and therefore reduces radiation shielding problems. The system is mainly pumped by integrated sputter-ion pumps using the fields of the dipole and quadrupole magnets. The impedence of the beam environment is kept small by minimizing the dimensions of the pump slots and avoiding steps of greater than 1 mm inside the vacuum chamber. A vacuum pressure in the 10 −9 mbar range was achieved some days after assembly of the vacuum system and without bake-out in situ. A beam lifetime of more than one hour was observed during the first test runs of HERA.

Traps and rings: Is small beautiful?

In recent years ion traps of various types have served in studies of collision interactions and spectroscopy of low energy multicharged ions. With large storage rings for multicharged heavy ions, dedicated to atomic physics research, now planned or coming into operation, it is useful to consider the role of ion traps in future experimental work. The capabilities and current limitations of multicharged ion research using traps are discussed, and a comparison with storage rings for the purposes of ion spectroscopy is made. Recent experimental investigations to develop techniques for the study of multicharged ions in traps using laser or synchrotron radiation are discussed, including a UHV pulsed gas source and an atom beam as ionization targets.

A scheme to measure the polarization asymmetry at the z pole in LEP

If longitudinally polarized beams are available in the large electron-position storage ring (LEP), it is shown that running with a specific sequence of polarized and depolarized bunches will allow both a measurement of the polarization asymmetry A LR and the absolute calibration of the polarimeters. The resulting accuracy that one can expect is discussed.

Future of large tandems plus boosters

The future of existing large tandem facilities lies firstly in the application of developments to achieve higher terminal voltages, secondly in the addition of a suitable booster, and thirdly in the use of the tandem as injector for a large synchrotron or storage ring. The development of the Vivitron in Strasbourg might well be the prototype for one or two more machines in the range of terminal voltages between 35 MV and 50 MV. The field of large tandems and boosters is very much alive and we can expect a series of improvements and even new developments in the next ten years.

Recent Progress in RF Superconductivity

The wide spread activities to prepare major size superconducting accelerating systems mainly for the large storage rings presently under construction in Europe and Japan are based on the continuous progress in rf superconductivity achieved in the past years. The thermal stability of s. c. cavities has been increased significantly by improving the thermal conductivity of niobium with different techniques. The promising attempts to sputter high purity niobium onto 500 MHz copper cavities have shown encouraging results. Multicell cavities at 3 GHz coated with Nb3Sn achieved high Q values already at 4.2 K. Field emission studies using modern surface analytical tools are shedding more light on anomalous electric surface breakdown fields. This report summarizes briefly the current activities in different laboratories and comments on recent achievements with superconducting cavities and in materials research. It concentrates on work performed prior to the preparation of accelerator experiments. These are discussed by R. Sundelin 1 and in other contributions to this conference.

A Diagnostic for Dynamic Aperture

In large accelerators and low beta colliding beam storage rings, the strong sextupoles, which are required to correct the chromatic effects, produce strong nonlinear forces which act on particles in the beam. In addition in large hadron storage rings the superconducting magnets have significant nonlinear fields. To understand the effects of these nonlinearities on the particle motion there is currently a large theoretical effort using both analytic techniques and computer tracking. This effort is focused on the determination of the 'dynamic aperture' (the stable acceptance) of both present and future accelerators and storage rings. A great deal of progress has been made in understanding nonlinear particle motion, but very little experimental verification of the theoretical results is available. In this paper we describe 'dynamic tracking', a method being studied at the SPEAR storage ring, which can be used to obtain experimental results which are in a convenient form to be compared with the theoretical predictions.