Narrow Results

A recently proposed technique in storage ring accelerators is applied to provide potential high-power sources of photon radiation. The technique is based on the steady-state microbunching (SSMB) mechanism. As examples of this application, one may consider a high-power DUV photon source for research in atomic and molecular physics or a high-power EUV radiation source for industrial lithography. A less challenging proof-of-principle test to produce IR radiation using an existing storage ring is also considered.

We report an efficient dynamic aperture (DA) optimization approach using multi-objective genetic algorithm (MOGA), which is driven by nonlinear driving terms computation. It was found that having small low order driving terms is a necessary but insufficient condition of having a decent DA. Then direct DA tracking simulation is implemented among the last generation candidates to select the best solutions. The approach was demonstrated successfully in optimizing NSLS-II storage ring DA.

The Muon $g-2$ Experiment at Fermilab (E989) is directed toward measuring the muon magnetic anomaly, $a_{\mu }=(g-2)/2$, with total statistical and systematic errors of 0.14 ppm. This new measurement will serve as strong probe of effects of as yet undiscovered particles beyond the Standard Model (SM), and perhaps validate or disprove other theoretical models beyond the SM. Of special interest is the reduction of muon losses from the storage ring to achieve the precision needed at the Muon $g-2$ Experiment. For this purpose, we have developed a detailed and precise symplectic model of the Muon $g-2$ Storage Ring using COSY INFINITY that considers measured inhomogeneities of the magnetic field; high-order representation of the Electrostatic Quadrupole System (EQS) electrostatic field at different stages of the experiment including fringe fields; injection to the ring based on measurements; and beam collimation. Specifically, we have performed numerical analyses of the rate of muons that are lost before they have a chance to decay for several possible configurations of the EQS in order to find the best possible scenarios that minimize muon losses and understand the resonance mechanisms that contribute to betatron and possibly spin resonances. Additionally, comparisons with measurements have permitted the determination of whether observed resonances come from anticipated features of the $g-2$ storage ring or from unexpected sources of error whose effect could be detrimental to the precision of E989.

Nonlinear effects of the various electric field and magnetic field components of storage rings to confine the particles and bend their trajectory can cause substantial amplitude-dependent tune shifts within the beam. Furthermore, tune shifts are often sensitive to variations of system parameters, e.g. total particle momentum offsets $\delta p$. Such amplitude- and parameter-dependent tune shifts influence the dynamics and stability of a beam in particle storage rings. Thus, it is critical for high precision measurements to analyze and understand these influences. On this basis, we present normal form methods for the calculation of high order amplitude and system parameter dependencies of the horizontal and vertical tunes in storage rings using the differential algebra (DA) framework within COSY INFINITY. A storage ring is simulated using COSY INFINITY to generate a DA Poincaré return map describing the transverse phase space behavior after each revolution in the storage ring. The map is expanded around the parameter-dependent closed orbit of the system before transforming the resulting map into normal form coordinates to extract the high order tune dependencies on the phase space amplitude and variation in the system parameters. As a specific example, a storage ring similar to the Storage Ring of the Muon $g$-2 Experiment at Fermilab (E989) is investigated.

The physics of synchrotron radiation, undulator radiation, and free electron lasers is reviewed with an emphasis on the underlying physical principles and the experimental observables, such as the radiation spectrum, angular distribution, and radiation polarization.

This article outlines the development and evolution of storage ring light sources, focusing on the latest, third generation light sources. After making brief historical remarks, it describes the current status, the performance, and the technological advancements of third generation light sources. The future developments of the ultimate storage ring as the next generation light source are envisioned.

For several decades already, particle colliders have been essential tools for particle physics. From the very beginning, such accelerators have been among the most complicated scientific instruments ever built, including a number of innovative technological developments. Examples are ultrahigh vacuum systems, magnets with a very high magnetic field, and equipment for sub-ns synchronization and sub-mm precision alignment of equipment inside multi-km underground tunnels. Some key technologies are related to the focusing of the beam down to a scale of sub-μm at the collision point to obtain high luminosity. This review provides an overview of collision concepts and technologies for circular particle colliders, starting from the first ideas. In particular, it discusses such novel schemes and related technologies as crab waist collision and round beam collision.

Electrostatic accelerators have played a glorious role in physics, especially for low energy atomic and nuclear physics and electron microscopy. But circular accelerators have depended almost exclusively on the far greater bending force possible with static magnetic, rather than electric, fields. There is a potential exception to this magnetic bending monopoly for experimental high energy elementary particle physics — it is the possibility of measuring the electric dipole moments (EDMs) of charged elementary particles, such as proton, deuteron, or electron, using an electrostatic storage ring. Any such non-zero EDM would demonstrate violation of both parity (P) and time-reversal (T) invariance. One way of understanding the preponderance of matter over anti-matter in the present-day universe pre-supposes the existence of violations of P and T substantially greater than are allowed by the “standard model” of elementary particle physics. This provides the leading motivation for measuring EDMs. Currently, only upper limits are known for these EDMs. The very same smallness that makes it important to determine them makes their measurement difficult. Accepting as obvious the particle physics motivation, this paper concentrates on the accelerator physics of the (not very) high energy electrostatic accelerators needed for EDM measurements. Developments already completed are emphasized. Impressive advances have been made in the diagnostic tools, spin control and polarimetry that will make EDM measurement possible. Ring design for minimizing spin decoherence and limiting systematic EDM errors is presented. There have, however, been worrisome indications from low energy rings, concerning beam current limitations. A prototype ring design is proposed for investigating and addressing this concern.

Feasibility studies using 0.97-GeV/c polarized deuterons to determine the suitability of storage rings in the search for intrinsic electric dipole moments have led to new developments in storage ring polarimeters. Efficiency has increased with the use of thick carbon targets. The calibration of the effects of geometric and rate-dependent errors has made possible the subtraction of these systematic errors, resulting in sensitivities at or below 10${}^{-5}$ to polarization changes during the time of the store. Tagging polarimeter events with the clock time had made available the turn number for each event, making possible longitudinal profile and horizontal polarization measurements. These have been used to explore the correction of second-order contributions to decoherence using sextupole fields, yielding horizontal polarization lifetimes as long as 20 minutes. Such studies may be extended to protons and ³He.

In this contribution, we discuss aspects of spectral tuning of molecular chromophores at the atomic level. The basis for the discussion is a series of measurements performed at the electrostatic ion-storage ring ELISA at the University of Aarhus. The experimental technique, which is a type of “action spectroscopy” based on photo dissociation, will briefly be discussed. We will present examples of spectral tuning due to external charges and proton exchange with the hosting medium.

Electrostatic accelerators have played a glorious role in physics, especially for low energy atomic and nuclear physics and electron microscopy. But circular accelerators have depended almost exclusively on the far greater bending force possible with static magnetic, rather than electric, fields. There is a potential exception to this magnetic bending monopoly for experimental high energy elementary particle physics — it is the possibility of measuring the electric dipole moments (EDMs) of charged elementary particles, such as proton, deuteron, or electron, using an electrostatic storage ring. Any such non-zero EDM would demonstrate violation of both parity (P) and time-reversal (T) invariance. One way of understanding the preponderance of matter over anti-matter in the present-day universe pre-supposes the existence of violations of P and T substantially greater than are allowed by the “standard model” of elementary particle physics. This provides the leading motivation for measuring EDMs. Currently, only upper limits are known for these EDMs. The very same smallness that makes it important to determine them makes their measurement difficult. Accepting as obvious the particle physics motivation, this paper concentrates on the accelerator physics of the (not very) high energy electrostatic accelerators needed for EDM measurements. Developments already completed are emphasized. Impressive advances have been made in the diagnostic tools, spin control and polarimetry that will make EDM measurement possible. Ring design for minimizing spin decoherence and limiting systematic EDM errors is presented. There have, however, been worrisome indications from low energy rings, concerning beam current limitations. A prototype ring design is proposed for investigating and addressing this concern.

The physics of synchrotron radiation, undulator radiation, and free electron lasers is reviewed with an emphasis on the underlying physical principles and the experimental observables, such as the radiation spectrum, angular distribution, and radiation polarization.

We report an eficient dynamic aperture (DA) optimization approach using multi-objective genetic algorithm (MOGA), which is driven by nonlinear driving terms computation. It was found that having small low order driving terms is a necessary but insufficient condition of having a decent DA. Then direct DA tracking simulation is implemented among the last generation candidates to select the best solutions. The approach was demonstrated successfully in optimizing NSLS-II storage ring DA.

This article outlines the development and evolution of storage ring light sources, focusing on the latest, third generation light sources. After making brief historical remarks, it describes the current status, the performance, and the technological advancements of third generation light sources. The future developments of the ultimate storage ring as the next generation light source are envisioned.

Recent commissioning of the Cooler Storage Ring at the Heavy Ion Research Facility in Lanzhou (HIRFL-CSR) has allowed us for direct mass measurements at the Institute of Modern Physics in Lanzhou (IMP), Chinese Academy of Sciences. A series of isochronous mass measurements have been carried out in the past few years using ⁷⁸Kr, ⁸⁶Kr, ⁵⁸Ni, and ¹¹²Sn beams. The main results and the present status are presented in this talk, and the implications of these results with respect to nuclear structures and nucleosynthesis in the rp-process of x-ray bursts are discussed.

Laser Compton scattering gamma-ray beam source has been developed at the NewSUBARU synchrotron light facility. The available maximum Gamma-ray photon energy is 76 MeV. The flux of quasi-monochromatic gamma-ray photons (for example: 16.7 MeV, ΔE/E ~ 5%) is more than 10⁶photons/sec using a 35 W Nd:YVO₄ laser combined with the 1 GeV storage electron beam with an intensity of 300 mA. We used the electron beams at E_e = 0.55 ~ 1.47 GeV for changing the energy of quasi-monochromatic gamma-ray beam. Gamma-ray beams were used for application experiments, a nuclear physics research, a nondestructive inspection of thick material, a generation of positron by pair creation, a magnetic Compton scattering measurements, and a nuclear transmutation.

For several decades already, particle colliders have been essential tools for particle physics. From the very beginning, such accelerators have been among the most complicated scientific instruments ever built, including a number of innovative technological developments. Examples are ultrahigh vacuum systems, magnets with a very high magnetic field, and equipment for sub-ns synchronization and sub-mm precision alignment of equipment inside multi-km underground tunnels. Some key technologies are related to the focusing of the beam down to a scale of sub-μm at the collision point to obtain high luminosity. This review provides an overview of collision concepts and technologies for circular particle colliders, starting from the first ideas. In particular, it discusses such novel schemes and related technologies as crab waist collision and round beam collision.

Typical application of Si detectors in high energy physics is tracking. A variety of Si strip and pixel trackers is meanwhile built and successfully operated. In nuclear physics and astrophysics, in addition to tracking, energy loss measurements are very important. Recently, application to time measurements have been suggested and successfully tested. Applications of Si detectors on the examples of experiments performed at GSI, Darmstadt are presented, together with the ideas of using them in the future at FAIR and ACCULLINA2 facilities.

A recently proposed technique in storage ring accelerators is applied to provide potential high-power sources of photon radiation. The technique is based on the steady-state microbunching (SSMB) mechanism. As examples of this application, one may consider a high-power DUV photon source for research in atomic and molecular physics or a high-power EUV radiation source for industrial lithography. A less challenging proof-of-principle test to produce IR radiation using an existing storage ring is also considered.