Use Of Storage Rings Research Articles

Phase Locking the Spin Precession in a Storage Ring.

This Letter reports the successful use of feedback from a spin polarization measurement to the revolution frequency of a 0.97 GeV/c bunched and polarized deuteron beam in the Cooler Synchrotron (COSY) storage ring in order to control both the precession rate (≈121 kHz) and the phase of the horizontal polarization component. Real time synchronization with a radio frequency (rf) solenoid made possible the rotation of the polarization out of the horizontal plane, yielding a demonstration of the feedback method to manipulate the polarization. In particular, the rotation rate shows a sinusoidal function of the horizontal polarization phase (relative to the rf solenoid), which was controlled to within a 1 standard deviation range of σ=0.21 rad. The minimum possible adjustment was 3.7mHz out of a revolution frequency of 753kHz, which changes the precession rate by 26 mrad/s. Such a capability meets a requirement for the use of storage rings to look for an intrinsic electric dipole moment of charged particles.

The Use of Storage Rings in the Study of Reactions at Low-momentum Transfers

A few aspects of the nucleus manifest themselves in direct reactions where the transferred momentum to the nucleus is very small. In the study of radioactive isotopes, one has to use inverse kinematics in which the radioactive ion impinges on a stable target. When the momentum transfer is low, one has to do these reactions with either an active target or in a storage-ring environment. In this contribution, the latter method will be discussed in some detail as the active targets are discussed in other contributions. The pilot studies performed by the EXL Collaboration in 2012 lead to the first ever measurements of reactions employing radioactive isotopes in the ring. In this contribution, the first results will be presented. The outlook will indicate in which directions the future of this field will be headed.

Search for electric dipole moments in storage rings

The JEDI collaboration aims at making use of storage ring to provide the most precise measurement of the electric dipole moments of hadrons. The method makes exploits a longitudinal polarized beam. The existence an electric dipole moment would generate a torque slowly twisting the particle spin out of plan of the storage ring into the vertical direction. The observation of non zero electric dipole moment would represent a clear sign of new physics beyond the Standard Model. Feasiblity tests are presently undergoing at the COSY storage ring Forschungszentrum Julich (Germany), to develop the novel techniques to be implemented in a future dedicated storage ring.

Energy recovery linacs as synchrotron radiation sources (invited)

Practically all synchrotron x-ray sources to data are based on the use of storage rings to produce the high current electron (or positron) beams needed for synchrotron radiation (SR). The ultimate limitations on the quality of the electron beam, which are directly reflected in many of the most important characteristics of the SR beams, arise from the physics of equilibrium processes fundamental to the operation of storage rings. It is possible to produce electron beams with superior characteristics for SR via photoinjected electron sources and high-energy linacs; however, the energy consumption of such machines is prohibitive. This limitation can be overcome by the use of an energy recovery linac (ERL), which involves configuring the electron-beam path to use the same superconducting linac as a decelerator of the electron beam after SR production, thereby recovering the beam energy for acceleration of new electrons. ERLs have the potential to produce SR beams with brilliance, coherence, time structure, and source size and shape which are superior to even the best third-generation storage ring sources, while maintaining flexible machine operation and competitive costs. Here, we describe a project to produce a hard x-ray ERL SR source at Cornell University, with emphasis on the characteristics, promise, and challenges of such an ERL machine.

Possible detection of high frequency gravitational waves in storage rings: speculation on future applications

The effects induced by the interaction of gravitational waves (GWs) with ultra-relativistic bunches of particles in storage rings are analysed. Using a system of high precision beam monitors, each individual bunch of particles can be monitored and its oscillations, at relatively high frequencies, measured. We speculate on the possible use of storage rings equipped with refined monitors to be used as GW detectors. The noise induced by ground motion at low frequencies limits the possibility to measure any effect for GW frequencies bellow 100 Hz, where the ground motion spectral power density is too high; however, the level of ground motion noise is low at high frequencies, increasing the signal to noise ratio and the possibility to detect a cosmic background of gravitational radiation.

Excitation function experiments at storage rings with the ultimate goal to probe the liquid-gas phase transition

The use of storage rings, operating in slow ramping mode to obtain excitation function data, is presented. Such experiments could provide a new way of probing the liquid-gas phase transition. We also discuss “isotopic effect ratios” which may act both as thermometer and as clock for the fragmentation process. Recent data on π +, p and d emission in the first slow ramping experiments at the CELSIUS storage ring are presented.

Beam energy measurement and stabilization at the storage ring VEPP-2M

Adequate use of storage rings as synchrotron radiation sources requires exact knowledge of parameters like beam energy. This article discusses the long term experience of beam energy measurements at the storage ring VEPP-2M.

Recent heavy-ion fusion power plant studies in the US

The United States Department of Energy (DOE) sponsored two studies of inertial fusion energy (IFE) electric power plants, one led by McDonnell Douglas Aerospace (MDA) and the other led by W. J. Schafer Associates (WJSA). These studies, which were completed in March of 1992, included the conceptual design and analysis of two KrF-laser and two heavy-ion-driven power plants. The reactor and driver designs for the heavy-ion power plants are described in this paper. The MDA team design, Prometheus-H, features a wetted-wall chamber, a compact induction linac driver, and channel propagation for beam delivery. The single-beam driver uses storage rings to accumulate a series of pulses before delivery to the target. The use of storage rings and a folded linear section results in a compact footprint and significant cost savings compared to a straight multiple-beam linac. Fourteen beams of doubly-charged, 4 GeV Pb ions are used to deliver 7 MJ on the target at a pulse repetition rate of 3.5 Hz with an overall driver efficiency of 21%. The channel propagation mode requires only two small, diametrically opposed holes through the blanket and first wall; this approach maximizes the wall coverage and minimizes radiation leakage and contamination of the beamlines. Th resulting target gain is 103 for a yield of 719 MJ per pulse. The Prometheus chamber has a Pb-cooled, porous SiC first wall and a He-cooled Li2O breeding blanket. The blanket structural material is low-activation SiC. The thermal conversion efficiency is 43%, and the net electric power is 1000 MWe. The WJSA team design, Osiris, uses a wetted-wall chamber, a multiple-beam induction linac driver, and ballistic focus with auto-neutralization. The driver design is conservative in that it uses singly charged ions and does not use beam combination or splitting. Twelve beams are close-packed in order to use common cores and focusing magnets. The accelerator costs were reduced by operating at spacecharge-limited current density and standardizing the quadrupole and inductor designs. In this case, twelve beams of 3.8 GeV Xe ions provide a total of 5 MJ at a pulse repetition rate of 4.6 Hz. The overall driver efficiency is 28%, the target gain is 87, and the yield is 432 MJ per pulse. The Osiris chamber uses a flexible, porous carbon/carbon fabric to contain the flow of the molten salt Flibe, which serves as the primary coolant and breeding material. The vacuum vessel structure is a carbon/carbon composite. The thermal conversion efficiency is 45%, and the net electric power is 1000 MWe.

Experiences with titanium sublimation pumps for uhv/accelerator application

Titanium sublimation pumps have been studied in reasonable detail over the past few decades. This type of pump evolved primarily to ensure fast pump down in industrial systems. Though it has been adopted for accelerator, fusion and space applications, it has always been used as an auxiliary pump. We have tried to evaluate the various commercially available sublimation pumps, including TiBall®, for use in storage rings. A number of interesting aspects like the influence of impurities in titanium, the vacuum chamber walls, operating parameters, the purity of gases and consequent substitution reactions while pumping H 2, N 2, CO, CO 2, CH 4 and mixtures of gases were studied. Besides possibility of trapping of gases like Ar and their evolution in the system are investigated. In essence, there is still a lot to be understood about the mechanism of sublimation pumping and we present here some new data and analysis.

Test of a polarized hydrogen gas target based on the storage cell technique

A polarized hydrogen gas target for use in storage rings has been developed. One application may be the production of a stored polarized antiproton beam via spin dependent attenuation which would allow a study of the spin-dependence of antiproton-proton interactions. In order to increase the target thickness compared to jet targets the polarized hydrogen atoms are injected into a T-shaped storage cell. Polarization and density of the target have been measured in a test experiment by elastic scattering of an α-beam from the Heidelberg MP-tandem accelerator. The target polarization amounts to 83±8% of the maximum possible value. The target areal density of n = (2.6±0.1±0.2) × 1013H/cm2 is consistent with the density calculated from the measured H beam intensity.

Realizations op polarized targets in storage rings

While particle storage rings generally provide a large average current, they require ultra-thin targets in order to maintain a reasonable lifetime of the beam. Targets composed of polarized atomic gas are well-suited for use in storage rings because of their thinness and the high degree of purity and polarization possible. Several of these so-called internal targets have been developed and successfully used to measure scattering asymmetries at Novosibirsk; future experiments have been proposed at Bates, NIKHEF and HERA, for example, which also rely on these techniques. The methods that have so far proved feasible for producing and storing highly polarized atoms will be reviewed.

Some mineralogical applications of synchrotron radiation

Synchrotron radiation offers several advantages over the conventional X-ray sources, among which the most important are its high intensity, broad spectral range and natural collimation. Among the numerous techniques which have been recently developed we present a review of the results concerning more specifically mineralogical systems: X-ray absorption spectroscopy concerning high-resolution edge spectra and Extended X-ray absorption fine structure (EXAFS), X-ray diffraction under high P-high T conditions, small-angle scattering, X-ray microanalysis and X-ray topography. For each technique the basic principles are described together with the experimental devices used, before mineralogical examples are given. Two main applications may be pointed out: chemical and structural characterization of disordered systems and kinetic studies (phase transitions and evolution). Many other techniques (photoelectron spectroscopy, X-ray fluorescence analysis ...) which are actually under development as a result of the rapid increase of the use of storage rings are not covered in the present review but will possibly also be used in the near future in Earth Sciences.

An Isochronous Stacking Ring Approach to the HTE

The problem of finding a suitable apparatus for demonstrating heavy ion fusion is a difficult one to approach in moderate steps. Ideally, such apparatus would be useful for testing beam transport, focusing and targeting concepts, and target behavior in the plasma regime, and the technology used in this ''high temperature experiment'' (HTE) would also be extended to construct a prototype fusion facility. A meaningful test of many of these concepts could be achieved with a device capable of heating a disk of material to plasma temperatures in the neighborhood of 100 eV or 1 million degrees K. Target heating for the HTE requires a short beam burst on the order of tens of nanoseconds with a total beam energy of a kilojoule or more. The RF linac falls far short of this capacity. A number of studies have looked at the use of storage rings for accumulating beam current. This paper looks at an alternative means: the use of a RF linac followed by an isochronous storage ring (ISR) producing rapidly the high multiplication of beam current required. This method avoids the necessity for beam manipulations such as splitting and bunching. Also, because of the fast transit time in themore » ISR, storage ring instabilities pose no problem. The paper discusses beam stacking with an isochronous ring and then addresses the use of an ISR for the HTE and the design and performance of an apparatus--consisting of an ion source, a RF linac, a stacking ring, and a number of beam lines to transfer beam bunches to the target--for such an application.« less

Results from storage rings

The historical development of those fields of physics investigated using storage rings is traced. The paper is divided into three parts. The first is the use of storage rings to investigate the validity of quantum electrodynamics. Second is their use in investigating vector meson dominance and lastly new aspects and preliminary results at high energy is given.