High Energy Storage Ring Research Articles

PANDA at the GSI future facility

PANDA is the multi-purpose detector that is under construction to cover most of the measurements using antiprotons from the high-energy storage ring (HESR), which will become possible at the GSI future facility. The detector setup has to meet the requirements of a broad physics programme, which ranges from high-resolution resonance spectroscopy in the charmonium region to the production of open charm in annihilations of antiprotons on heavy nuclei. The interaction rate of up to 10 7 annihilations/s requires sophisticated trigger concepts, which are in part based on vertex detection. To this end, PANDA will be equipped with a compact state-of-the-art micro-vertex detector. Its data shall be used for D meson identification at data acquisition time. Layout of the vertex detector and its interaction with the other detector parts are discussed and an introduction into the physics programme is given.

An ultra-low-energy storage ring at FLAIR

The future accelerator Facility for Antiproton and Ion Research (FAIR) at GSI, Darmstadt will produce the highest flux of antiprotons in the world. So far it is foreseen to accelerate the antiprotons to high energies (3–15 GeV) for meson spectroscopy and other nuclear and particle physics experiments in the High-Energy Storage Ring (HESR). Within the planned complex of storage rings, it is possible to decelerate the antiprotons to about 30 MeV kinetic energy, opening up the possibility to create low-energy antiprotons. In the proposed Facility for Low-energy Antiproton and Ion Research (FLAIR) [ http://www.flair.eu.tt] the antiprotons shall be slowed down in a last step from 300 to 20 keV in an ultra-low-energy electrostatic storage ring (USR) for various in-ring experiments as well as for their efficient injection into traps. This paper presents the layout and design parameters of the USR.

Future hypernuclear physics at MAMI-C and PANDA-GSI

Hypernuclei represent the first steps towards an extension of the periodic system into the sector of strangeness and thus add a third dimension to our evolving picture of nuclei. They provide a large variety of new and exciting perspectives ranging from new dynamical symmetries in hypernuclei spectra, non-mesonic weak decays, and the interplay of the quark-exchange and meson-exchange aspects of strong baryon–baryon forces in the flavor SU ( 3 ) world. Furthermore, double hypernuclei may provide a doorway towards exotic quark states. In the near future, electroproduction experiments at TJNAF and MAMI-C will add more detailed information on the structure of single hypernuclei states. On the long term, experiments at the Japanese hadron facility and the high energy storage ring for antiprotons at the future GSI accelerator facility will allow us to extend high resolution γ-ray studies also into the domain of double hypernuclei.

THE PANDA DETECTOR AT THE GSI-FAIR PROJECT

A major component of the approved upgrade of the GSI facility in Darmstadt, Germany is the High Energy Storage Ring (HESR) for high intensity, phase space cooled antiprotons with momenta up to 15 GeV/c. At this facility a wide physics program is planned to investigate both the structure of hadrons in the charmonium mass range and the spectroscopy of double hypernuclei. To serve the many experiments planned at this new facility, a general purpose detector called PANDA (Proton ANtiproton Detector Array) is planned. An overview of the PANDA detector concept, as well as selected results from simulation of the detector's performance will be presented.

CHARMONIUM AND EXOTIC HADRONS AT PANDA

Recently GSI presented the plans for a major new international research facility, called FAIR. A key feature of this new facility will be the delivery of intense, high-quality secondary beams which embody the production of antiprotons. For the antiproton beams a High Energy Storage Ring (HESR) is comprised. The design luminosity is 2·1032 cm -2 s -1. Experiments will take place at an internal target. The rich spectroscopy program on exotic hadrons with antiproton beams is presented.

The PANDA experiment at FAIR

The approved FAIR upgrade of the GSI facility in Darmstadt, Germany, includes the construction of a High Energy Storage Ring (HESR) for high intensity, phase space cooled antiprotons with momenta up to 15 GeV/c. A wide physics program is planned at this facility to investigate fundamental questions of hadron and nuclear physics in interactions of antiprotons with nucleons and nuclei. To serve the many experiments planned at this new facility an universal, modular, hermetic spectrometer called PANDA (Proton ANtiproton Detector Array) is planned.

Physics with the P̄ANDA detector at GSI

The P̄ANDA experiment, which will be installed at the High-Energy Storage Ring (HESR) of the recently approved FAIR facility at GSI in Darmstadt, Germany, has a rich experimental program of hadron spectroscopy which includes the study of charmonium, the search for glueballs and hybrids and the investigation of in-medium modifications of hadrons as they interact with nuclear matter.

From laser cooling of non-relativistic to relativistic ion beams

Laser cooling of stored 24Mg+ ion beams recently led to the long anticipated experimental realization of Coulomb-ordered ‘crystalline’ ion beams in the low-energy RF-quadrupole storage ring PAul Laser CooLing Acceleration System (Munich). Moreover, systematic studies revealed severe constraints on the cooling scheme and the storage ring lattice for the attainment and maintenance of the crystalline state of the beam, which will be summarized. With the envisaged advent of high-energy heavy ion storage rings like SIS300 at GSI (Darmstadt), which offer favourable lattice conditions for space-charge-dominated beams, we here discuss the general scaling of laser cooling of highly relativistic beams of highly charged ions and present a novel idea for direct three-dimensional beam cooling by forcing the ions onto a helical path.

Dipole instability of a circulating beam due to the ion cloud in an electron cooling system

We consider the dipole instability of the circulating beam in a storage ring in presence of a cooling electron beam and an “ion cloud” captured in the potential well of the electron beam. The coherent interaction between the centers of gravity of three species (circulating beam, cooling electrons and accumulated ions) is described by a four-dimensional transfer matrix with elements depending on frequency. The interaction becomes dangerous when the frequency of the dipole oscillations for the circulating beam coincides with the coherent frequency of the ion cloud. The theory is applied to the planned antiproton storage ring HESR (High Energy Storage Ring), which is part of the GSI future project. Calculations show that in the HESR, comparatively small ion traces (with a neutralization factor 0.2%) can increase the instability increment by 1–2 orders of magnitude compared with the case without ions.

１Ａを越える蓄積電流と加速器真空系〜ＫＥＫ Ｂ−Ｆａｃｔｏｒｙでの経験〜

Described are several technical issues of a vacuum system for high energy storage rings. A vacuum chamber (beam duct) contains a charged particle beam, which brings a variety of problems to the system as increasing the beam current.The beam excites intense high-frequency electro-magnetic waves, for example, that lead to heating and discharges at several vacuum components. Pulsed high wall currents accompanied with the beam are also likely to result in discharges at insufficient electric connections.

Conceptual design and simulation of the PANDA detector

A major component of the approved upgrade of the GSI facility in Darmstadt, Germany is the high energy storage ring for high intensity, phase space cooled antiprotons with momenta up to 15 GeV/ c. At this facility a wide physics program is planned to investigate both the structure of hadrons in the charmonium mass range and the spectroscopy of double hypernuclei. To serve the many experiments planned at this new facility, a general purpose detector called PANDA (Proton ANtiproton Detector Array) is planned. The feasibility of the PANDA detector concept to perform the proposed physics program has been investigated with simulations based on the GEANT4 package. The detector concept, as well as selected results from these simulations are presented.

Variable-period undulators as synchrotron radiation sources.

A concept for variable-period undulators for the production of synchrotron radiation from both medium- and high-energy storage rings is described. This concept is based on a staggered array of permeable poles placed in a magnetic solenoid that produces a longitudinal field. The concept permits variations in the short magnetic period of the undulator of as much as 100%. The unique capabilities of such undulators will allow them to be tuned by the variation of the period length and of the solenoid field. The device can be operated at either constant flux or constant power, independent of X-ray energy. It is expected that the new concept will have a major impact on the production and applications of X-rays because of the inherent simplicity and flexibility of the design and the absence of radiation damage. Analyses of the magnetic and mechanical design concepts are presented.

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.

Ion-hose instability in a long-pulse linear induction accelerator

The ion-hose instability is a transverse electrostatic instability which occurs on electron beams in the presence of a low-density ion channel. It is a phenomenon quite similar to the interaction between electron clouds and proton or positron beams in high-energy accelerators and storage rings. In the DARHT-2 accelerator, the 2-kA, $2\mathrm{\text{\ensuremath{-}}}\ensuremath{\mu}\mathrm{s}$ beam pulse produces an ion channel through impact ionization of the residual background gas (${10}^{\ensuremath{-}7}--{10}^{\ensuremath{-}6}\text{ }\mathrm{torr}$). A calculation of the linear growth by Briggs indicates that the instability could be strong enough to affect the radiographic application of DARHT, which requires that transverse oscillations be small compared to the beam radius. We present semianalytical theory and 3D particle-in-cell simulations (using the Lsp code) of the linear and nonlinear growth of the instability, including the effects of the temporal change in the ion density and spatially decreasing beam radius. We find that the number of $e$-foldings experienced by a given beam slice is given approximately by an analytic expression using the local channel density at the beam slice. Hence, in the linear regime, the number of $e$-foldings increases linearly from head to tail of the beam pulse since it is proportional to the ion density. We also find that growth is strongly suppressed by nonlinear effects at relatively small oscillation amplitudes of the electron beam. This is because the ion oscillation amplitude is several times larger than that of the beam, allowing nonlinear effects to come into play. An analogous effect has recently been noted in electron-proton instabilities in high-energy accelerators and storage rings. For DARHT-2 parameters, we find that a pressure of $\ensuremath{\le}1.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}\text{ }\mathrm{torr}$ is needed to keep the transverse beam oscillation amplitude less than about 20% of the rms beam radius.

Crystallisation of ion beams in the rf quadrupole storage ring PALLAS

The crystallisation of laser-cooled Mg+ ion beams circulating in the table-top rf quadrupole storage ring PALLAS at a velocity of the order of 2800 m/s (beam energy 1 eV) is reviewed. Emphasis is given to the description of the experimental techniques that were required for this first realisation of crystalline beams. The equivalence of the equations of motion for rf electric and magnetic confinement and thus for PALLAS and high-energy storage rings is pointed out. The phase transition is indicated by the detection of a sudden collapse of the transverse beam size, by the low velocity spread, and by the exceptional stability of the crystalline state, persisting for more than3000 revolutions or 106 focusing periods without any cooling.

Physics with Antiprotons at the Future GSI Facility

Recently GSI presented the plans for a major new international research facility (http://www.gsi.de/GSI-future/). Highly luminous secondary beams with excellent quality encompassing the production of antiprotons will be delivered. In a High Energy Storage Ring (HESR) with a bending power of 50 Tm antiprotons will be cooled either stochastically or by electrons. The envisaged limits are a momentum range of 1.5 to 15 GeV/c and a luminosity of 2 × 1032 cm-2 s-1. Four major physical research goals can be addressed: high precision charmonium spectroscopy, medium effects of open and hidden charm, the search for glueballs and hybrids, and the production of hypernuclei.

The quest for crystalline ion beams

The phase transition of an ion beam into its crystalline state has long been expected to dramatically influence beam dynamics beyond the limitations of standard accelerator physics. Yet, although considerable improvement in beam cooling techniques has been made, strong heating mechanisms inherent to existing high-energy storage rings have prohibited the formation of the crystalline state in these machines up to now. Only recently, laser cooling of low-energy beams in the table-top rf quadrupole storage ring PAaul Laser cooLing Acceleration System (PALLAS) has lead to the experimental realization of crystalline beams. In this article, the quest for crystalline beams as well as their unique properties as experienced in PALLAS will be reviewed.

Tune shifts of bunch trains due to resistive vacuum chambers without circular symmetry

We present an explanation for the opposite signs of the horizontal and vertical tune shifts of bunch trains which have been observed recently in several high-energy storage rings. This result can be understood in terms of the long-range quadrupolar wakes of noncircular vacuum chambers with finite resistivity. In vacuum chambers with circular cross section, the dominant transverse wake driven by a leading particle and seen by a trailing test particle is dipolar and is proportional only to the transverse offset of the driving particle. The contributions of preceding bunches or previous turns tend to cancel, as they add with oscillatory factors. On the other hand, quadrupolar wakes are independent of the offset of the driving particle, and thus the contributions of preceding bunches and turns are strictly additive. Since quadrupole fields are focusing in one plane and defocusing in the plane orthogonal to it, their effects on tune shifts in these planes have opposite signs. Their cumulative effect also explains the large values of the tune shifts measured in PEP-II, which exceeded estimates from other impedance sources by factors of 3 to 4. Our analysis also offers a connection to the familiar Laslett tune shift.

Measurement of radiation-induced demagnetization of Nd–Fe–B permanent magnets

Nd–Fe–B permanent magnets are highly desirable for use in the insertion devices of synchrotron radiation sources due to their high remanence, or residual magnetic induction, and intrinsic coercivity. However, the radiation environment within high-energy storage rings makes essential the determination of the degree of radiation sensitivity as well as the mechanisms of radiation-induced demagnetization. Sample Nd–Fe–B permanent magnets were irradiated at the Advanced Photon Source with bending magnet X-rays up to an absorbed dose of approximately 280 Mrad (1 Mrad=10kGy). Sample magnets were also irradiated with 60Co γ-rays up to an absorbed dose of 700 Mrad at the National Institute of Standards and Technology's standard gamma irradiation facility. Changes in the residual induction were found to be within the experimental uncertainties for both the X-ray and γ-ray irradiations. Sample Nd–Fe–B permanent magnets were then irradiated at Oak Ridge National Laboratory's Californium User Facility for Neutron Science with fast neutrons up to a total fast fluence of 1.61×10 14 n/cm 2, and with thermal neutrons up to a total thermal fluence of 2.94×10 12 n/cm 2. The fast-neutron irradiation revealed changes between residual induction measurements of the sample magnets before and after irradiation of 0.6% and greater for fast-neutron fluence levels of 2×10 13 n/cm 2 and above. Thermal-neutron irradiation revealed changes in the residual induction measurements of the sample magnets before and after irradiation that were within the experimental uncertainties for thermal-neutron fluence levels up to 3×10 12 n/cm 2.

Conceptual design of a hybrid-type elliptically polarizing undulator

A hybrid-type planar undulator was designed to generate circularly polarized radiation. It is an APPLE-type design consisting of four rows of hybrid structures that can be shifted with respect to each other. The magnetic field on axis can thus be adjusted so it can have linear or circular polarization including intermediate (elliptical polarization) positions. A short-period device of this kind can provide 100% circularly polarized radiation in a hard x-ray region when it is installed in a high-energy storage ring, such as the Advanced Photon Source.