Stored Ion Beam Research Articles

Stochastic cooling notch filter developments for the high-precision spectrometer ring in the high intensity heavy-ion accelerator facility project.

Stochastic cooling of the high-precision spectrometer ring (SRing) at the High Intensity Heavy-Ion Accelerator Facility (HIAF) project in China, which is used mainly for experiments with radioactive fragment beams, is applied to speed up the cooling process of a stored ion beam. In this article, a new coaxial-type notch filter with an amplitude equalizer in the long branch and an optical-type notch filter with phase-stabilized optical fiber are discussed and evaluated for the SRing stochastic cooling system. Both prototypes of coaxial and optical notch filters are fabricated and tested. The minimum notch depth of coaxial and optical notch filters reaches to 26 and 40 dB, respectively. The performance of both coaxial notch filter and optical fiber notch filter is presented in this work. These developments will be used not only for the longitudinal stochastic cooling system but also have potential for the beam feedback system.

Skin values and matter radii of 208Pb and 58,60,64Ni based on reaction cross section of 3,4He scattering

Background:The PREX group reported a new skin value, rskin208(PREX2)=0.283±0.071=0.212∼0.354fm. Using the chiral (Kyushu) g-matrix folding model with the proton and neutron densities determined with D1S+GHFB+AMP, we determined neutron skin thickness rskin208(exp)=0.278±0.035 fm from reaction cross sections σR(exp) of p+208Pb scattering, where D1S-GHFB+AMP denotes Gogny-D1S HFB with angular momentum projection (AMP). The method also yielded rskin208(exp)=0.416±0.146 from σR(exp) of 4He+208Pb scattering. In our previous work, we accumulated the 206 EoSs and determined a sloop parameter L=76∼165MeV from the 206 EoSs. The value of L yields rskin208=0.102∼0.354fm. As for 58Ni, a novel method for measuring nuclear reactions in inverse kinematics with stored ion beams was successfully used to extract matter radii rm of 58Ni at the GSI facility. Purpose:As the first aim, we first determine rskin208(exp) from σR(exp) of 3He scattering on 208Pb target and take the weighted mean and its error for rskin208(PREX2), three skin values of p+208Pb, 3,4He+208Pb scattering and rskin208=0.102∼0.354fm based on the 206 EoSs. As the second aim, we determine matter radii rm(exp) of 58,60,64Ni from σR(exp) of 3,4He scattering on 58,60,64Ni targets. Results:Our result is rskin208(exp)=0.512±0.268fm for 3He+208Pb scattering. Our results based on 4He+58,60,64Ni scattering are rm58(exp)=3.734±0.091 fm, rm60(exp)=3.815±0.094 fm, rm64(exp)=4.001±0.093 fm. Our results based on 3He+58,60,64Ni scattering are rm58(exp)=3.709±0.098 fm, rm60(exp)=3.753±0.112 fm, rm64(exp)=3.822±0.142 fm. Conclusion:Our conclusion is rskin208=0.285±0.030fm. It is determined from the 5 skin values mentioned above.

Thermometry of stored molecular ion beams

The radiative cooling of a stored, initially rotationally hot OH^{-} ion beam is probed by photodetachment using an electrostatic ion beam trap combined with an in-trap velocity map imaging spectrometer, providing direct measurement of the time-dependent rotational population. The rotational temperatures are estimated from photodetached electron spectra as a function of time using a Boltzmann distribution model and further verified by a rate law model using known Einstein coefficients. We demonstrate that during the entire cooling time, the rotational population can be well described by a Boltzmann distribution.

Stochastic Cooling Pickup/Kicker Developments for the High-Precision Spectrometer Ring in the HIAF Project at IMP

Stochastic cooling of the spectrometer ring (SRing) at the High Intensity Heavy-Ion Accelerator Facility (HIAF) project in China, which is used mainly for experiments with radioactive fragment beams, is applied to speed up the cooling process of a stored ion beam. In this study, both a Faltin traveling wave structure and a novel slot-ring standing wave structure based on a ceramic vacuum chamber are discussed and evaluated for the pickup/kicker of the SRing stochastic cooling system. The slot-ring structure should significantly improve the shunt impedance due to the Cherenkov effect. For the Faltin-type structure, the results for the pickup shunt impedance obtained from simulations and from beam measurements agree well. Good agreement is also found between the simulated and measured results for the pickup shunt impedance of the slot-ring structure. Cooling process simulations using the Fokker-Planck equation based on the shunt impedance results for the Faltin- and slot-ring-type pickups are also presented.

A 410 MHz resonant cavity pickup for heavy ion storage rings.

An improved design of a longitudinally sensitive resonant Schottky cavity pickup for the heavy ion storage rings of the Facility for Antiproton and Ion Research in Europe (FAIR) project is reported. The new detector has a higher measured Q value of ∼3000 and a higher simulated shunt impedance of 473.3 kΩ. It is possible to vary the sensitivity of the cavity with a motorized mechanism by inserting a dissipative blade during the operation based on experimental needs. Apart from a lower price tag, the new design features a more robust and production-friendly mechanical structure suitable for a series production in the future FAIR project. The manufactured cavity was built temporarily into the experimental storage ring and had delivered its first results using stored heavy ion beams. The structure, simulation results, and performance of this cavity are presented in this work.

Laser cooling and precision laser spectroscopy of highly charged ions at the storage ring CSRe and the future HIAF

Laser cooling and precision laser spectroscopy of highly charged ions are considered as frontiers of atomic physics research at heavy ion storage rings. A brief overview of the fundamentals of these powerful methods, applied to relativistic stored ion beams, is given. Preliminary results from laser cooling of lithium-like 16O5+ ion beams at a relativistic energy of 275.7 MeV/u at the heavy-ion storage ring CSRe are presented and prospects for upcoming experiments at the future facility HIAF are discussed.

Longitudinal modulation of electron-cooled [formula omitted] and [formula omitted] ion beams at heavy ion storage ring CSRe

The longitudinal dynamics of electron-cooled and radio-frequency (RF)-bunched 12C6+ and 16O8+ ion beams have been investigated at a heavy-ion experimental cooler storage ring CSRe. An rf-buncher was employed to longitudinally modulate the ion beams. A new resonant Schottky pick-up was applied to monitor the intensities and longitudinal dynamics of stored and electron-cooled ion beams. Using electron-cooling, the separated Schottky noise signals of the 12C6+ and 16O8+ ions were clearly observed in the Schottky spectrum. The storage times and the particle numbers of both ion beams were measured by Schottky noise, which demonstrated the ability to perform Schottky mass spectrometry measurements and also the measurement of highly charged ions at the CSRe. In addition, an enhancement of the Schottky noise signals was observed for rf-bunched ion beams, which could be used to diagnose the intensity ion beams at storage rings. Finally, a broadly longitudinal manipulation of the ion beams by scanning the bunching frequency was realized. The investigation of electron–ion recombination experiment at ultra-low collision energies by scanning the bunching frequency of the ion beams at the storage ring CSRe is proposed.

Nuclear-matter radius studies fromNi58(α,α)experiments at the GSI Experimental Storage Ring with the EXL facility

A novel method for measuring nuclear reactions in inverse kinematics with stored ion beams was successfully used to extract the nuclear-matter radius of Ni58. The experiment was performed at the experimental heavy-ion storage ring at the GSI facility using a stored Ni58 beam at energies of 100 and 150 MeV/u and an internal helium gas-jet target. Elastically scattered α-recoils at low momentum transfers were measured with an in-ring detector system compatible with ultrahigh vacuum. Experimental angular distributions were fitted using density-dependent optical model potentials within the eikonal approximation. This permitted the extraction of the point-matter root-mean-square radius of Ni58 with an average value of 3.70(7) fm. Results from this work are in good agreement with several experiments performed in the past in normal kinematics. This pioneering experiment demonstrates a major breakthrough towards future investigations with far-from-stability stored beams using the present technique.Received 22 June 2017DOI:https://doi.org/10.1103/PhysRevC.96.034617©2017 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasAccelerator/storage ring control systemsH & He induced nuclear reactionsNuclear charge distributionNuclear matterProperties39 ≤ A ≤ 58Nuclear PhysicsAccelerators & Beams

Measurement of the lifetime and the proportion of 12C3+ ions in stored relativistic ion beams as a preparation for laser cooling experiments at the CSRe

We report on an experiment that was conducted in preparation of laser cooling experiments at the heavy-ion storage ring CSRe. The lifetimes of ion beams made up of 12C3+ and 16O4+ ions stored at an energy of 122MeV/u in the CSRe were determined by two independent methods, firstly via a DC current transformer (DCCT) and secondly via a Schottky resonator. Using electron-cooling, the signals of the 12C3+ and 16O4+ ions could be separated and clearly observed in the Schottky spectrum. The obtained individual lifetimes of the 12C3+ and 16O4+ components were 23.6s and 17.8s, respectively. The proportion of 12C3+ ions in the stored ion beam was measured to be more than 70% at the beginning of the injection and increasing as a function of time. In addition to these measurements, the operation and remote control of a pulsed laser system placed directly next to the storage ring was tested in a setup similar to the one envisaged for future laser experiments.

First measurement of isoscalar giant resonances in a stored-beam experiment

Abstract A new technique developed for measuring nuclear reactions at low momentum transfer with stored beams in inverse kinematics was successfully used to study isoscalar giant resonances. The experiment was carried out at the experimental heavy-ion storage ring (ESR) at the GSI facility using a stored 58 Ni beam at 100 MeV/u and an internal helium gas-jet target. In these measurements, inelastically scattered α -recoils at very forward center-of-mass angles ( θ cm ≤ 1.5 ° ) were detected with a dedicated setup, including ultra-high vacuum compatible detectors. Experimental results indicate a dominant contribution of the isoscalar giant monopole resonance at this very forward angular range. It was found that the monopole contribution exhausts 79 − 11 + 12 % of the energy-weighted sum rule (EWSR), which agrees with measurements performed in normal kinematics. This opens up the opportunity to investigate the giant resonances in a large domain of unstable and exotic nuclei in the near future. It is a fundamental milestone towards new nuclear reaction studies with stored ion beams.

Laser cooling of relativistic heavy-ion beams for FAIR

Laser cooling is a powerful technique to reduce the longitudinal momentum spread of stored relativistic ion beams. Based on successful experiments at the experimental storage ring at GSI in Darmstadt, of which we show some important results in this paper, we present our plans for laser cooling of relativistic ion beams in the future heavy-ion synchrotron SIS100 at the Facility for Antiproton and Ion Research in Darmstadt.

Characterization of a new electrostatic storage ring for photofragmentation experiments.

We describe the design of and the first commissioning experiments with a newly constructed electrostatic storage ring named SAPHIRA (Storage Ring in Aarhus for PHoton-Ion Reaction Analysis). With an intense beam of Cu(-) at 4 keV, the storage ring is characterized in terms of the stored ion beam decay rate, the longitudinal spreading of an injected ion bunch, as well as the direct measurements of the transverse spatial distributions under different conditions of storage. The ion storage stability in SAPHIRA was investigated systematically in a selected region of its electrical configuration space.

DESIREE: Physics with cold stored ion beams

Here we will briefly describe the commissioning of the Double ElectroStatic Ion Ring ExpEriment (DESIREE) facility at Stockholm University, Sweden. This device uses purely electrostatic focussing and deflection elements and allows ion beams of opposite charge to be confined under extreme high vacuum and cryogenic conditions in separate rings and then merged over a common straight section. This apparatus allows for studies of interactions between cations and anions at very low and well-defined centre-of-mass energies (down to a few meV) and at very low internal temperatures (down to a few K).

Commissioning of the DESIREE storage rings – a new facility for cold ion-ion collisions

We report on the ongoing commissioning of the Double ElectroStatic Ion Ring ExpEriment, DESIREE, at Stockholm University. Beams of atomic carbon anions (C−) and smaller carbon anion molecules (C−2, C−3, C−4 etc.) have been produced in a sputter ion source, accelerated to 10 keV or 20 keV, and stored successfully in the two electrostatic rings. The rings are enclosed in a common vacuum chamber cooled to below 13 Kelvin. The DESIREE facility allows for studies of internally relaxed single isolated atomic, molecular and cluster ions and for collision experiments between cat- and anions down to very low center-of-mass collision energies (meV scale). The total thermal load of the vacuum chamber at this temperature is measured to be 32 W. The decay rates of stored ion beams have two components: a non-exponential component caused by the space charge of the beam itself which dominates at early times and an exponential term from the neutralization of the beam in collisions with residual gas at later times. The residual gas limited storage lifetime of carbon anions in the symmetric ring is over seven minutes while the 1/e lifetime in the asymmetric ring is measured to be about 30 seconds. Although we aim to improve the storage in the second ring, the number of stored ions are now sufficient for many merged beams experiments with positive and negative ions requiring milliseconds to seconds ion storage.

Detection system for forward emitted photons at the Experimental Storage Ring at GSI

A single photon counting system has been developed for efficient detection of forward emitted fluorescence photons at the Experimental Storage Ring (ESR) at GSI. The system employs a movable parabolic mirror with a central slit that can be positioned around the ion beam and a selected low noise photomultiplier for detection of the collected photons. Compared to the previously used system of mirror segments installed inside the ESR the collection efficiency for forward-emitted photons is improved by more than a factor of 5. No adverse effects on the stored ion beam have been observed during operation besides a small drop in the ion current of about 5% during movement of the mirror into the beam position. The new detection system has been used in the LIBELLE experiment at ESR and enabled for the first time the detection of the ground-state hyperfine M1 transition in lithium-like bismuth (209Bi80+) in a laser-spectroscopy measurement.

Accelerators for future neutrino facilities: strengths and challenges

Several different ideas have been put forward for future neutrino facilities, including a high-power conventional neutrino beam (a "Superbeam" facility), a Beta Beam facility based on stored beta-unstable ion beams, and a Neutrino Factory based on stored muon beams. Each of these has its advantages and disadvantages, and these are described here. After briefly describing the physics context, the various options will be described and their respective strengths and challenges indicated. The supporting R&D programs will be briefly discussed and a few specific technical questions for each facility will be outlined.

Resonance coupling induced enhancement of indirect transverse cooling in a laser-cooled ion beam

We report the first observation of indirect resonantly enhanced transverse laser cooling of a bunched, stored ion beam of 40 keV $^{24}\mathrm{Mg}^{+}$. The longitudinal velocity distribution and the horizontal beam size of the laser-cooled $^{24}\mathrm{Mg}^{+}$ ion beam with 280 nm laser light were simultaneously observed by the use of standard fluorescence-based techniques. Keeping the operation point at (2.068, 1.105), the synchrotron tune (${\ensuremath{\nu}}_{s}$) was changed from 0.0376 to 0.1299. A strong decrease in the cooled horizontal beam size and a corresponding increase in the equilibrium cooled momentum spread were observed at the expected synchrobetatron resonance coupling condition of ${\ensuremath{\nu}}_{s}=0.068$, which is the first observation of a resonantly induced coupling for enhanced indirect transverse laser cooling of an ion beam, and is an important step towards creating a crystalline ground state of the beam.

Storage ring at HIE-ISOLDE

We propose to install a storage ring at an ISOL-type radioactive beam facility for the first time. Specifically, we intend to setup the heavy-ion, low-energy ring TSR at the HIE-ISOLDE facility in CERN, Geneva. Such a facility will provide a capability for experiments with stored secondary beams that is unique in the world. The envisaged physics programme is rich and varied, spanning from investigations of nuclear ground-state properties and reaction studies of astrophysical relevance, to investigations with highly-charged ions and pure isomeric beams. The TSR might also be employed for removal of isobaric contaminants from stored ion beams and for systematic studies within the neutrino beam programme. In addition to experiments performed using beams recirculating within the ring, cooled beams can also be extracted and exploited by external spectrometers for high-precision measurements. The existing TSR, which is presently in operation at the Max-Planck Institute for Nuclear Physics in Heidelberg, is well-suited and can be employed for this purpose. The physics cases as well as technical details of the existing ring facility and of the beam and infrastructure requirements at HIE-ISOLDE are discussed in the present technical design report.

Shielding Calculations for the New Experimental Storage Ring for the Facility for Antiproton and Ion Research

The new experimental storage ring (NESR) is one of the new facilities planned for the Facility for Antiproton and Ion Research (FAIR) project. It is conceived as a versatile storage ring used for experiments with stored ion beams (up to 740 MeV/u for uranium beams) and for the deceleration of antiprotons from the injection energy of 3 GeV, which are subsequently extracted and used for experiments elsewhere.The planning of the shielding requires particular accuracy because rooms adjacent to the NESR are desired to be accessible at all times. Extensive shielding calculations have been done using the Monte Carlo code FLUKA. Calculations were performed separately for the different operation modes of the storage ring, as well as for the different parts of the facility. Because of the large shielding thicknesses required (up to ~4 m), biasing techniques had to be employed. While the results of the calculations confirmed that the planned shielding is sufficient in most places, two areas have been identified where a reinforcement of the shielding is recommended.

Three-Dimensional Laser Cooling of Ion Beams Using a Wien Filter

Laser cooling of ion beams generally operates only upon the longitudinal motion of an ion beam. In order to extend this powerful dissipative force to the transverse directions, we consider introducing a Wien filter in a cooing straight section. It is theoretically shown that longitudinal cooling within a Wien filter naturally develops a transverse (mostly horizontal) cooling effect as well. Molecular dynamics simulations demonstrate that this method enables us to reach an ultralow-temperature state of a stored ion beam.