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In this work we detail experiments performed on a gear-changing system using the Double ElectroStatic Ion Ring ExpEriment (DESIREE). A gear-changing system is one where there are different harmonic numbers in each ring. This experiment used carbon and nitrogen beams in a 4 on 3 gear-changing arrangement, with the last bunch of each left off. The bunch length can be measured and synchrotron motion detected. We performed this measurement on three different values of carbon current, and present the differences in the bunch length frequency spectrum here, which correspond to twice the synchrotron frequencies., Proceedings of the 13th International Particle Accelerator Conference, IPAC2022, Bangkok, Thailand

The double ion storage ring DESIREE has been used in combination with position- and time-sensitive detectors to study the mutual neutralization of N+ with O− at 40 meV collision energy. Several previously unassigned spectral features observed in a recent single-pass merged-beams experiment at 7 meV collision energy [Phys. Rev. Lett. 121, 083401 (2018)], were also observed in the present experiment. It was found that neutralization channels of the first metastable state of the cation [N+(1D), τ ≈ 256 s] could explain the majority of these features, while the second metastable state [N+(1S), τ ≈ 0.9 s] was not found to contribute significantly. The branching ratios into the different electronically excited states of N were determined and found to be in good agreement between the two experiments. Theoretical calculations using the multichannel Landau-Zener model were found to yield good results for a number of channels, but could not describe some observed contributions, possibly due to the presence of other processes not accounted for in the model.

The double ion storage ring DESIREE has been used in combination with position- and time-sensitive detectors to study the mutual neutralization of N+ with O- at 40 meV collision energy. Several previously unassigned spectral features observed in a recent single-pass merged-beams experiment at 7 meV collision energy [Phys. Rev. Lett. 121, 083401 (2018)], were also observed in the present experiment. It was found that neutralization channels of the first metastable state of the cation [N+(1D), τ≈ 256 s] could explain the majority of these features, while the second metastable state [N+(1S), τ≈ 0.9 s] was not found to contribute significantly. The branching ratios into the different electronically excited states of N were determined and found to be in good agreement between the two experiments. Theoretical calculations using the multichannel Landau-Zener model were found to yield good results for a number of channels, but could not describe some observed contributions, possibly due to the presence of other processes not accounted for in the model.

In this work, we perform measurements on the interactions of colliding beams in a gear-changing system. Gear-changing was first demonstrated in DESIREE in May of 2020 and showed several promising avenues to measure beam-beam effects. DESIREE has a unique collision scheme where the beams are moving in the same direction, which provides for unique interactions. This experiment used a 4 on 3 gear changing system with one bucket in each ring left empty, this allows us to see the bunch profile while undergoing collisions. We then measured the bunch length over time and used a Fourier transform to extract longitudinal evolution data and compared it to baseline data of uncollided beams., Proceedings of the 12th International Particle Accelerator Conference, IPAC2021, Campinas, SP, Brazil

The present paper reports on a merged-beam experiment on mutual neutralization between Na+ and D-. For this experiment, we have used the DESIREE ion-beams storage-ring facility. The reaction products are detected using a position- and time-sensitive detector, which ideally allows for determination of the population of each individual quantum state in the final atomic systems. Here, the 4s, 3d, and 4p final states in Na are observed and in all cases the D atom is in its ground state 1s S-2. The respective branching fractions of the states populated in Na are determined by fitting results from a Monte Carlo simulation of the experiment to the measured data. The center-of-mass collision energy is controlled using a set of biased drift tubes, and the branching fractions are measured for energies between 80 meV and 393 meV. The resulting branching fractions are found to agree qualitatively with the only available theoretical calculations for this particular system, which are based on a multichannel Landau-Zener approach using dynamic couplings determined with a linear combination of atomic orbitals model.

The current status of DESIREE is described, with special emphasis on the setup for collision experiments with ions in both the two electrostatic rings - negative ions in one ring and positive in the other. By measuring the kinetic energy released in mutual neutralization reactions be-tween the two ions at collision energies close to zero eV in 3D, the population of different reaction channels has been obtained. The different steps necessary to set up the beams to get well controlled experimental properties are described as well as the principles behind our automatic optimization routines, which are extensively used with consistent result., Proceedings of the 10th Int. Particle Accelerator Conf., IPAC2019, Melbourne, Australia

DESIREE, the double electrostatic storage rings in Stockholm has been running since 2011(?). In the cold (13 K) environment with an excellent vacuum, very long storage times in both rings have been achieved, which has enabled the preparation of beams in a single quantum state. The status of DESIREE is presented with particular emphasis on measurements of stored beam currents in the sub-nA range. We also discuss the ongoing work towards stochastic cooling of very slow beams., Proceedings of the 8th Int. Particle Accelerator Conf., IPAC2017, Copenhagen, Denmark

The use of the instrumentation in the cryogenic double electrostatic storage rings DESIREE is discussed. In particular measurements of the stored beam currents using either a fast kick-out of the beam or Schottky noise signals are presented. For the Schottky signals, both the area of the peak and the double-peak structure of the signal have been used. Also the first tests of a stochastic cooling system are described., Proceedings of the 4th International Beam Instrumentation Conference, IBIC2015, Melbourne, Australia

DESIREE, the double electrostatic storage rings in Stockholm, is now commissioned and used for experiments. The two 9 m circumference storage rings, which are constructed inside a double walled cryostat, are now cooled to 13 K and routinely used for storage of both negative and positive ions with lifetimes of several minutes. The main properties of DESIREE are presented as well as results from the commissioning and the first experiments., Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany

The EU supported EURISOL Design Study encompasses a beta-beam facility for neutrino physics. Intense electron (anti-)neutrino beams are in such a machine generated through the decay of radioactive ions in a high energy storage ring. The two main candidate isotopes for the generation of a neutrino and an antineutrino beam are 6He and 18Ne. The intensities required are hard to reach, in particular for the neon case. A possible solution to increase the intensity is to use an accumulator ring with an electron cooler. Critical parameters such as cooling times and current limitations due to space charge and tune shifts are presently being optimized. We will in this presentation give an overview of the low energy accumulation stage and review recent work on this option.

The Beta-Beam is a concept of large-scale facility that aims at providing pure electronic neutrino and antineutrino beams for the measurement of electron and muon neutrino oscillations. Beta-decaying nuclides are produced in large amounts in a facility of the scale of EURISOL, and are then post-accelerated and stored at large gamma in a racetrack decay ring. We present here a conceptual design of the accelerator chain of a Beta-Beam based at CERN.