Proton Storage Ring Research Articles

NICA Facilities for the Search for EDM Light Nuclei

To search for proton Electric Dipole Moments (EDM) using proton storage ring with purely electrostatic elements, the concept of frozen spin method has been proposed by Brookhaven National Laboratory. This method is based on two facts: in the equation of spin precession, the magnetic field dependence is entirely eliminated, and at the ‘‘magic’’ energy, the spin precession frequency coincides with the precession frequency of the particle momentum. In case of deuteron, we have to use the electrical and magnetic field simultaneously, keeping the frozen spin direction along the momentum as in the pure electrostatic ring. Later, Yu. Senichev proposed the concept of quasi-frozen spin, in which the spin oscillates around the direction of the pulse within half the value of the advanced phase of rotation in magnetic arcs, each time returning back in deflectors with an electrostatic field. Due to the low value of the anomalous magnetic moment of deuteron, an effective contribution to the expected EDM effect is reduced only by a few percent compared with frozen spin method. In this work, we consider the adapted structure of the NICA and Nuclotron synchrotrons, in which the ‘‘quasi-frozen spin’’ option can be implemented. The advantage of the ‘‘quasi-frozen spin’’ concept is the possibility of using synchrotrons already existing in the world that are not focused on studying EDM, which makes this method the only one possible for the accelerators of the NICA complex.

Spin of Protons in NICA and PTR Storage Rings as an Axion Antenna

A new approach to search for axions in the storage ring experiments, applicable at a short coherence time of the in-plane polarization as is the case for protons is discussed. The technique can readily be applied at any storage ring equipped with internal polarimeter for the radial polarization of the beam (COSY, NICA, PTR). A possibility of substantial broadening of the range of attainable axion masses in storage rings with the hybrid electric and magnetic bending is pointed out, the PTR proton storage ring being an example.

Fast injection and extraction kicker system design for High rEpetition rate Muon Source at CSNS

A non-parasitic muon production facility (HEMS, abbreviation of High rEpetition rate Muon Source) at China Spallation Neutron Source (CSNS) is proposed. HEMS will extract a 500 MeV proton beam from a proton storage ring with a circumference of 80 m to bombard a target on a linear section at a repetition rate of 100 Hz. After bombarding the target, the beam will be injected back into the proton storage ring. The proton beam will be extracted and injected repeatedly to the proton storage ring 20 times within 20 ms. For injection and extraction kicker system, the repetition rate of pulser should be as high as 1 kHz. In addition, to achieve a large kick angle with a high magnet gap aperture in a relatively small beam lattice, kicker pulser is required to generate a large excitation current. The primary challenge is to build a high repetition rate, high current, and fast injection and extraction kicker system. To achieve these requirements, a 6.25 Ω impedance matching kicker system, mainly composed of a twin-C transmission line kicker magnet and inductive adder, is developed. In this paper, we report the conceptual design of the kicker magnet and kicker pulser for HEMS.

Storage ring probes of dark matter and dark energy

We show that proton storage ring experiments designed to search for proton electric dipole moments can also be used to look for the nearly dc spin precession induced by dark energy and ultra-light dark matter. These experiments are sensitive to both axion-like and vector fields. Current technology permits probes of these phenomena up to three orders of magnitude beyond astrophysical limits. The relativistic boost of the protons in these rings allows this scheme to have sensitivities comparable to atomic co-magnetometer experiments that can also probe similar phenomena. These complementary approaches can be used to extract the micro-physics of a signal, allowing us to distinguish between pseudo-scalar, magnetic and electric dipole moment interactions.

Straightening of superconducting HERA dipoles for the any-light-particle-search experiment ALPS II

At DESY the ALPS II experiment is being installed in the HERA tunnel to search for axion like particles. A laser beam will be injected into the magnetic field of a string of superconducting (s.c.) dipole magnets, available from the HERA proton storage ring, to produce axion like particles. After passing a light tight wall, the ALPs can reconvert into photons in a second string of HERA s.c. dipoles. The sensitivity of the experiment will be increased by two mode-matched optical cavities before and behind the wall. The dipoles for the HERA storage ring are curved, suited for stored proton beam. However, the curvature of the magnets limits the aperture and hence the performance of the optical resonators beyond a certain length. As the sensitivity of the search scales with the length of the magnetic field, the aperture for the optical resonators inside the HERA dipoles was increased by straightening the curved magnet yoke. The procedure of straightening the s.c. HERA dipoles is described in this report.

Opening the 1 Hz axion window

An axion-like particle (ALP) with mass mϕ ∼ 10−15 eV oscillates with frequency ∼1 Hz. This mass scale lies in an open window of astrophysical constraints, and appears naturally as a consequence of grand unification (GUT) in string/M-theory. However, with a GUT-scale decay constant such an ALP overcloses the Universe, and cannot solve the strong CP problem. In this paper, we present a two axion model in which the 1 Hz ALP constitutes the entirety of the dark matter (DM) while the QCD axion solves the strong CP problem but contributes negligibly to the DM relic density. The mechanism to achieve the correct relic densities relies on low-scale inflation (mϕ ≲ Hinf ≲ 1 MeV), and we present explicit realisations of such a model. The scale in the axion potential leading to the 1 Hz axion generates a value for the strong CP phase which oscillates around {overline{theta}}_{mathrm{QCD}}sim {10}^{-12} , within reach of the proton storage ring electric dipole moment experiment. The 1 Hz axion is also in reach of near future laboratory and astrophysical searches.

An <i>e</i><sup>+</sup><i>e</i><sup>-</sup>/<i>γγ</i>/<i>ep</i> Accelerator Complex at a Future Circular Collider

This is the second paper by the author describing versatile accelerator complexes that could be built at a Future Circular Collider (FCC) in order to produce e+e-, γγ and ep collisions. The facility described here features an ILC-based e+e- collider placed tangentially to the FCC tunnel. If the collider is positioned asymmetrically with respect to the FCC tunnel, electron (or positron) bunches could be accelerated by both linacs before they are brought into collision with the 50-TeV beams from the FCC proton storage ring (FCC-pp). The two linacs may also form a part of the injector chain for FCC-pp. The facility could be converted into a γγ collider or a source of multi-MW beams for fixed-target experiments.

Method of barrier voltages in cyclic accelerators

Principle of operation of barrier RF voltage systems that are used for stacking and acceleration of charged particles in proton synchrotrons and storage rings is presented. The description is based on two sample models of such systems: with rectangular and quasi-sinusoidal barriers. Two different methods are used for description of particle dynamics in synchrotrons with barrier RF voltage. The first method is “stepwise” analysis of particle motion in the “momentum-phase” space. This method allows to give a clear and simple description of physical principles of the method and to obtain its main properties in analytical form. However, this method is not always efficient. Therefore, a method of analysis of phase motion of particles in barrier systems based on solution of differential equations of phase motion is presented in the paper and is widely used in practice. This method allows both analytical calculations and numeric simulation, which is illustrated with the aid of supplied examples.

Low uncertainty position transducers for the LHC collimators: tutorial 49

The Large Hadron Collider (LHC) is the largest particle accelerator ever built. The transverse energy density of the nominal beam is 1000 times higher than what was previously achieved in proton storage rings. Tiny fractions of the stored beam suffice to quench a super-conducting LHC magnet (i.e., a situation where part of the magnet exits the superconducting state) or even to destroy parts of the accelerator. The energy in the two LHC beams is sufficient to melt almost one ton of copper.

Search for electric dipole moments of light ions in storage rings

The Standard Model (SM) of Particle Physics is not capable to account for the apparent matterantimatter asymmetry of our Universe. Physics beyond the SM is required and is searched for by (i) employing highest energies (e.g., at LHC), and (ii) striving for ultimate precision and sensitivity (e.g., in the search for electric dipole moments (EDMs)). Permanent EDMs of particles violate both time reversal (T) and parity (P) invariance, and are via the CPT-theorem also CP-violating. Finding an EDM would be a strong indication for physics beyond the SM, and pushing upper limits further provides crucial tests for any corresponding theoretical model, e.g., SUSY. Direct searches of proton and deuteron EDMs bear the potential to reach sensitivities beyond 10−29 e cm. For an all-electric proton storage ring, this goal is pursued by the US-based srEDM collaboration [2], while the newly found Julich-based JEDI collaboration [1] is pursuing an approach using a combined electric-magnetic lattice which shall provide access to the EDMs of protons, deuterons, and 3He ions in the same machine. In addition, JEDI has recently proposed to perform a direct measurement of the proton and/or deuteron EDM at COSY using resonant techniques involving Wien filters.

The search for electric dipole moments of light ions in storage rings

The Standard Model (SM) of Particle Physics is not capable of accounting for the apparent matter-antimatter asymmetry of our universe. Physics beyond the SM is required and is searched for by (i) employing highest energies (e.g., at LHC), and (ii) striving for ultimate precision and sensitivity (e.g., in the search for electric dipole moments (EDMs)). Permanent EDMs of particles violate both time reversal (T) and parity (P) invariance, and are via the CPT-theorem also CP-violating. Finding an EDM would be a strong indication for physics beyond the SM, and reducing upper limits further provides crucial tests for any corresponding theoretical model, e.g., SUSY. Direct searches for proton and deuteron EDMs bear the potential to reach sensitivities beyond 10−29 e·cm. For an all-electric proton storage ring, this goal is pursued by the US-based srEDM collaboration [1], while the newly founded Jülich-based JEDI collaboration [2] is pursuing an approach using a combined electric-magnetic lattice, which shall provide access to the EDMs of protons, deuterons, and 3He ions in the same machine. In addition, JEDI has recently proposed making a direct measurement of the proton and/or deuteron EDM at COSY using resonant techniques involving Wien filters.

DAΦNE operation with electron-cloud-clearing electrodes.

The effects of an electron cloud (e-cloud) on beam dynamics are one of the major factors limiting performances of high intensity positron, proton, and ion storage rings. In the electron-positron collider DAΦNE, namely, a horizontal beam instability due to the electron-cloud effect has been identified as one of the main limitations on the maximum stored positron beam current and as a source of beam quality deterioration. During the last machine shutdown in order to mitigate such instability, special electrodes have been inserted in all dipole and wiggler magnets of the positron ring. It has been the first installation all over the world of this type since long metallic electrodes have been installed in all arcs of the collider positron ring and are currently used during the machine operation in collision. This has allowed a number of unprecedented measurements (e-cloud instabilities growth rate, transverse beam size variation, tune shifts along the bunch train) where the e-cloud contribution is clearly evidenced by turning the electrodes on and off. In this Letter we briefly describe a novel design of the electrodes, while the main focus is on experimental measurements. Here we report all results that clearly indicate the effectiveness of the electrodes for e-cloud suppression.

Independent component analysis applied to long bunch beams in the Los Alamos Proton Storage Ring

Independent component analysis (ICA) is a powerful blind source separation (BSS) method. Compared to the typical BSS method, principal component analysis, ICA is more robust to noise, coupling, and nonlinearity. The conventional ICA application to turn-by-turn position data from multiple beam position monitors (BPMs) yields information about cross-BPM correlations. With this scheme, multi-BPM ICA has been used to measure the transverse betatron phase and amplitude functions, dispersion function, linear coupling, sextupole strength, and nonlinear beam dynamics. We apply ICA in a new way to slices along the bunch revealing correlations of particle motion within the beam bunch. We digitize beam signals of the long bunch at the Los Alamos Proton Storage Ring with a single device (BPM or fast current monitor) for an entire injection-extraction cycle. ICA of the digitized beam signals results in source signals, which we identify to describe varying betatron motion along the bunch, locations of transverse resonances along the bunch, measurement noise, characteristic frequencies of the digitizing oscilloscopes, and longitudinal beam structure.

Design of a disc DIRC detector for the WASA experiment

A Disc DIRC counter is foreseen for the WASA experiment at the COSY proton storage ring in Jülich. It shall improve the proton kinetic energy measurement in the forward direction by measuring the proton speed at the two per mille level. The segmentation into four quarter-discs allows to incline the radiator relative to the incoming particles. This lowers the threshold velocity for light propagation inside the DIRC radiator. The construction of a full-scale quarter disc prototype is envisaged within a year.

Compact Storage Ring with Longitudinal Magnetic Field and Electron Cooling

Project of compact low energy proton storage ring (1.75 MeV) for production of high energy photons in reaction 13C(p,γ) 14N on internal target is presented. With the help of the photons it is possible to realize the scheme for detection of substances with heightened content of nitrogen using Nuclear Resonance Absorption method. Distinctive features of the construction are use of electron cooling method for beam heating compensation, and strong longitudinal magnetic field along full perimeter of the ring. For optimal work of electron cooling, compensation of space charge of the beam circulating in the ring is necessary. Results of simulation of main effects in the storage ring are shown. The results allow us to expect that proton current up to 100 mA can be stored and luminosity up to 3·1033 cm2 s -1 can be achieved

Experimental observations of in situ secondary electron yield reduction in the PEP-II particle accelerator beam line

Beam instability caused by the electron cloud has been observed in positron and proton storage rings and it is expected to be a limiting factor in the performance of the positron damping ring (DR) of future linear colliders (LC) such as ILC and CLIC [1,2]. To test a series of promising possible electron cloud mitigation techniques as surface coatings and grooves, in the Positron low-energy ring (LER) of the PEP-II accelerator, we have installed several test vacuum chambers including (i) a special chamber to monitor the variation in the secondary electron yield of technical surface materials and coatings under the effect of ion, electron and photon conditioning in situ in the beam line (ii) chambers with grooves [3] in a straight magnetic-free section and (iii) coated chambers in a dedicated newly installed 4-magnet chicane [4] to study mitigations in a magnetic field region. In this paper, we describe the ongoing R&D effort to mitigate the electron cloud effect for the LC damping ring, focusing on the first experimental area and on results of the reduction in the secondary electron yield due to in situ conditioning.

Continuing study on electron-cloud clearing techniques in high-intensity positron ring: Mitigation by using groove surface in vertical magnetic field

Beam instability caused by an electron cloud is one of the limiting factors in the performance of future advanced positron and proton storage rings. At a wiggler section in the positron ring of the KEK B-factory (KEKB), we installed a test beam chamber with a replaceable insertion and investigated different techniques for the mitigation of electron-cloud effect in a high magnetic field. All techniques were investigated under identical conditions. In this study, the insertions with an isosceles-triangular groove surface and a flat surface were investigated and compared. The groove insertion was composed of grooves running longitudinally along the beam orbit in order to reduce the beam impedance. In this experiment, a large reduction of almost one order of magnitude in the measured electron-cloud current was observed when the groove surface was used instead of the flat one. This is the first experimental demonstration of the concept of the groove surface in a magnetic field. The results are also compared with those obtained in a previous experiment in which a clearing electrode insertion was used.

Comparison of carbon and corrugated diamond stripper foils under operational conditions at the Los Alamos PSR

To accumulate high-intensity proton pulses, the Los Alamos Proton Storage Ring (PSR) uses the charge-exchange injection method. H − ions merge with already circulating protons in a bending magnet, and then are stripped off their two electrons in a carbon stripper foil. The circulating protons continue to interact with the foil. Despite efforts to minimize the number of these foil hits, like “painting” of the vertical phase space, they cannot totally be eliminated. As a result, foil heating and probably also radiation damage limit the lifetime of these foils. In recent years, LANL has collaborated with KEK to improve the carbon foils in use at PSR, and these foils now last typically for about 2 months. Recently, an alternative in the form of corrugated diamond foils has been proposed for use at SNS. These foils have now been tested in PSR production for a year, and have already shown to be at least as enduring as the LANL/KEK carbon foils. Advantages of the diamond foil concept, as well as some noteworthy differences that we observed with respect to the LANL carbon foils, will be discussed here.

Electron cloud simulations of a proton storage ring using cold proton bunches

Using the ORBIT code we study the sensitivity of electron cloud properties with respect to different proton beam profiles, the secondary electron yield (SEY) parameter, and the proton loss rate. Our model uses a cold proton bunch to generate primary electrons and electromagnetic field for electron cloud dynamics. We study the dependence of the prompt and swept electron signals vs the bunch charge and the recovery of electron clouds after sweeping on the beam loss rate and the SEY. The simulation results are compared with the experimental data measured at the proton storage ring at the Los Alamos National Laboratory. Our simulations indicate that the fractional proton loss rate in the field-free straight section may be an exponential function of proton beam charge and may also be lower than the averaged fractional proton loss rate over the whole ring.

Electron cloud generation and trapping in a quadrupole magnet at the Los Alamos proton storage ring

Recent beam physics studies on the two-stream e-p instability at the LANL proton storage ring (PSR) have focused on the role of the electron cloud generated in quadrupole magnets where primary electrons, which seed beam-induced multipacting, are expected to be largest due to grazing angle losses from the beam halo. A new diagnostic to measure electron cloud formation and trapping in a quadrupole magnet has been developed, installed, and successfully tested at PSR. Beam studies using this diagnostic show that the ``prompt'' electron flux striking the wall in a quadrupole is comparable to the prompt signal in the adjacent drift space. In addition, the ``swept'' electron signal, obtained using the sweeping feature of the diagnostic after the beam was extracted from the ring, was larger than expected and decayed slowly with an exponential time constant of 50 to $100\text{ }\text{ }\ensuremath{\mu}\mathrm{s}$. Other measurements include the cumulative energy spectra of prompt electrons and the variation of both prompt and swept electron signals with beam intensity. Experimental results were also obtained which suggest that a good fraction of the electrons observed in the adjacent drift space for the typical beam conditions in the 2006 run cycle were seeded by electrons ejected from the quadrupole.