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1.	Abele, H., et al. (author) Particle physics at the European Spallation Source 2023 In: Physics reports. - : Elsevier. - 0370-1573 .- 1873-6270. ; 1023, s. 1-84 Research review (peer-reviewed)abstract Presently under construction in Lund, Sweden, the European Spallation Source (ESS) will be the world’s brightest neutron source. As such, it has the potential for a particle physics program with a unique reach and which is complementary to that available at other facilities. This paper describes proposed particle physics activities for the ESS. These encompass the exploitation of both the neutrons and neutrinos produced at the ESS for high precision (sensitivity) measurements (searches).
2.	Schmidt, H. T., et al. (author) Recoil-ion momentum distribution for Transfer Ionization in fast proton-He collisions 2005 In: Phys. Rev. A. ; 72:012713 Journal article (peer-reviewed)
3.	Schmidt, HT, et al. (author) Recoil-ion momentum distributions for transfer ionization in fast proton-He collisions 2005 In: Physical Review A. Atomic, Molecular, and Optical Physics. - : American physical society. - 1050-2947 .- 1094-1622. ; 72:1 Journal article (peer-reviewed)abstract We present high-luminosity experimental investigations of the transfer ionization (TI:p+He -> H-0+He2++e(-)) process in collisions between fast protons and neutral helium atoms in the earlier inaccessibly high-energy range 1.4-5.8 MeV. The protons were stored in the heavy-ion storage and cooler ring CRYRING, where they intersected a narrow supersonic helium gas jet. We discuss the longitudinal recoil-ion momentum distribution, as measured by means of cold-target recoil-ion momentum spectroscopy and find that this distribution splits into two completely separated peaks at the high end of our energy range. These separate contributions are discussed in terms of the earlier proposed Thomas TI (TTI) and kinematic TI mechansims. The cross section of the TTI process is found to follow a sigma proportional to v(-b) dependence with b=10.78 +/- 0.27 in accordance with the expected v(-11) asymptotic behavior. Further, we discuss the probability for shake-off accompanying electron transfer and the relation of this TI mechanism to photodouble ionization. Finally the influence of the initial-state electron velocity distribution on the TTI process is discussed.
4.	Bohm, S., et al. (author) Measurement of the field-induced dielectronic recombination rate enhancement of N4+ ions differential in Rydberg quantum number n 2003 In: Nuclear Instruments and Methods in Physics Research B. - 0168-583X. ; 205, s. 370- Journal article (peer-reviewed)
5.	Böhm, S, et al. (author) Enhancement of dielectronic recombination by external electromagnetic fields 2003 In: Hyperfine Interactions. - 0304-3843. ; 146-147:1-4, s. 23-27 Journal article (peer-reviewed)abstract The enhancement of the dielectronic recombination rate of lithiumlike Ne7+ and O5+ ions by external electromagnetic fields has been measured at the storage ring CRYRING. The energy range covered all 1s(2)2pnl dielectronic recombination resonances attached to the 2s --> 2p core excitation. Electric fields up to 1436 V/cm were applied in the Ne7+ experiment and the saturation of the enhancement with increasing electric field could clearly be seen. In the O5+ experiment the enhancement was studied as a function of the Rydberg quantum number n.
6.	Böhm, S, et al. (author) Influence of electromagnetic fields on the dielectronic recombination of Ne7+ and O5+ ions 2001 In: Physica Scripta. Topical Issues. - 0281-1847. ; T92, s. 395-397 Journal article (peer-reviewed)abstract Within a series of measurements of the dielectronic recombination (DR) of lithium-like ions we have determined the enhancement of the recombination rate in the presence of crossed electric and magnetic fields for Ne7+ and O5+ ions. In both cases the electron energy range covers a DR resonances attached to 2s --> 2p(1/2) and 2s --> 2p(3/2) Delta_n = 0 core excitations. For increasing field the enhancement factor first increases linearly with the electric field and then saturates. In order to investigate the field effect on high-n Rydberg states the ion energy in the O5+ experiment was changed from 9.4 MeV/u to 5 MeV/u and 3.26 MeV/u. With the variation of the ion energy the field ionization of Rydberg states in the analyzing magnet is influenced. This enabled us to study the field enhancement for a narrow bandwidth of n-states.
7.	Böhm, S, et al. (author) Influence of electromagnetic fields on the dielectronic recombination of Ne7+ ions 2001 In: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947. ; 64:3, s. 032707/1-032707/7 Journal article (peer-reviewed)abstract The influence of crossed electric and magnetic fields on dielectronic recombination of Ne7+ ions has been measured at the Stockholm heavy-ion storage ring CRYRING. The electron energy range covered all dielectronic recombination resonances attached to 2s-2p1/2 and 2s-2p3/2 core excitations. Two sets of measurements at magnetic fields of 180 mT and 30 mT have been performed. For the measurement at 180 mT we applied 25 different electric fields between 0 and 1400 V/cm. The resonance strength for dielectronic recombination via high Rydberg states initially increases linearly with electric field and later levels out. At a magnetic field of 30 mT we applied 15 different electric fields ranging from 0 to 140 V/cm. Compared to the measurement at 180 mT the initial slope of the rate enhancement was larger by almost a factor of 2. The fraction of resonant strength not measured due to field ionization is estimated by a model calculation of dielectronic recombination cross sections.
8.	Gatchell, Michael, et al. (author) Commissioning of the DESIREE storage rings - a new facility for cold ion-ion collisions 2014 In: XXVIII International Conference on Photonic, Electronic and Atomic Collisions (ICPEAC 2013). - : Institute of Physics (IOP). ; 488:1 Conference paper (peer-reviewed)abstract 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.
9.	Wildner, E., et al. (author) The Opportunity Offered by the ESSnuSB Project to Exploit the Larger Leptonic CP Violation Signal at the Second Oscillation Maximum and the Requirements of This Project on the ESS Accelerator Complex 2016 In: Advances in High Energy Physics. - : Hindawi Publishing Corporation. - 1687-7357 .- 1687-7365. Journal article (peer-reviewed)abstract The European Spallation Source (ESS), currently under construction in Lund, Sweden, is a research center that will provide, by 2023, the world's most powerful neutron source. The average power of the proton linac will be 5 MW. Pulsing this linac at higher frequency will make it possible to raise the average total beam power to 10 MW to produce, in parallel with the spallation neutron production, a very intense neutrino Super Beam of about 0.4 GeV mean neutrino energy. This will allow searching for leptonic CP violation at the second oscillation maximum where the sensitivity is about 3 times higher than at the first. The ESS neutrino Super Beam, ESSnuSB operated with a 2.0 GeV linac proton beam, together with a large undergroundWater Cherenkov detector located at 540 km from Lund, will make it possible to discover leptonic CP violation at 5 sigma. significance level in 56% (65% for an upgrade to 2.5 GeV beam energy) of the leptonic CP-violating phase range after 10 years of data taking, assuming a 5% systematic error in the neutrino flux and 10% in the neutrino cross section. The paper presents the outstanding physics reach possible for CP violation with ESSnuSB obtainable under these assumptions for the systematic errors. It also describes the upgrade of the ESS accelerator complex required for ESSnuSB.
10.	Aguilar, J., et al. (author) Search for Leptonic CP Violation with the ESSnuSBplus Project 2024 In: Letters in High Energy Physics. - : Andromeda Publishing And Academic Services LTD. - 2632-2714. Journal article (peer-reviewed)abstract ESSνSB is a design study for a next-generation long-baseline neutrino experiment that aims at the precise measurement of the CP-violating phase, δCP, in the leptonic sector at the second oscillation maximum. The conceptual design report published from the first phase of the project showed that after 10 years of data taking, more than 70% of the possible δCP range will be covered with 5σ C.L. to reject the no-CP-violation hypothesis. The expected value of δCP precision is smaller than 8◦ for all δCP values. The next phase of the project, the ESSνSB+, aims at using the intense muon flux produced together with neutrinos to measure the neutrino-nucleus cross-section, the dominant term of the systematic uncertainty, in the energy range of 0.2–0.6 GeV, using a Low Energy neutrinos from STORed Muons (LEnuSTORM) and a Low Energy Monitored Neutrino Beam (LEMNB) facilities.
11.	Aguilar, J., et al. (author) Study of nonstandard interactions mediated by a scalar field at the ESSnuSB experiment 2024 In: Physical Review D. - : American Physical Society. - 2470-0010 .- 2470-0029. ; 109:11 Journal article (peer-reviewed)abstract In this paper, we study scalar mediator induced nonstandard interactions (SNSIs) in the context of the ESSnuSB experiment. In particular, we study the capability of ESSnuSB to put bounds on the SNSI parameters and also study the impact of SNSIs in the measurement of the leptonic CP phase δCP. Existence of SNSIs modifies the neutrino mass matrix and this modification can be expressed in terms of three diagonal real parameters (ηee, ημμ, and ηττ) and three off-diagonal complex parameters (ηeμ, ηeτ, and ημτ). Our study shows that the upper bounds on the parameters ημμ and ηττ depend upon how Δm312 is minimized in the theory. However, this is not the case when one tries to measure the impact of SNSIs on δCP. Further, we show that the CP sensitivity of ESSnuSB can be completely lost for certain values of ηee and ημτ for which the appearance channel probability becomes independent of δCP.
12.	Aguilar, J., et al. (author) Study of nonstandard interactions mediated by a scalar field at the ESSnuSB experiment 2024 In: Physical Review D. - : American Physical Society (APS). - 2470-0010 .- 2470-0029. ; 109:11 Journal article (peer-reviewed)abstract In this paper, we study scalar mediator induced nonstandard interactions (SNSIs) in the context of the ESSnuSB experiment. In particular, we study the capability of ESSnuSB to put bounds on the SNSI parameters and also study the impact of SNSIs in the measurement of the leptonic ?⁢? phase ??⁢?. Existence of SNSIs modifies the neutrino mass matrix and this modification can be expressed in terms of three diagonal real parameters (??⁢?, ??⁢?, and ??⁢?) and three off-diagonal complex parameters (??⁢?, ??⁢?, and ??⁢?). Our study shows that the upper bounds on the parameters ??⁢? and ??⁢? depend upon how Δ⁢?231 is minimized in the theory. However, this is not the case when one tries to measure the impact of SNSIs on ??⁢?. Further, we show that the ?⁢? sensitivity of ESSnuSB can be completely lost for certain values of ??⁢? and ??⁢? for which the appearance channel probability becomes independent of ??⁢?.
13.	Andersson, Pontus, 1971, et al. (author) Radiative lifetimes of metastable states of negative ions 2006 In: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622 .- 2469-9926 .- 2469-9934. ; 73, s. 032705- Journal article (peer-reviewed)abstract We present a technique for measuring the radiative lifetimes of metastable states of negative ions that involves the use of a heavy-ion storage ring. The method has been applied to investigate the radiative decay of the np(3) P-2(1/2) levels of Te-(n=5) and Se-(n=4) and the 3p(3) D-2 state of Si- for which the J=3/2 and 5/2 levels were unresolved. All of these states are metastable and decay primarily by emission of E2 and M1 radiation. Multi Configuration Dirac-Hartree-Fock calculations of rates for the transitions in Te- and Se- yielded lifetimes of 0.45 s and 4.7 s, respectively. The measured values agree well with these predicted values. In the case of the D-2 state of Si-, however, our measurement was only able to set a lower limit on the lifetime. The upper limit of the lifetime that can be measured with our apparatus is set by how long the ions can be stored in the ring, a limit determined by the rate of collisional detachment. Our lower limit of 1 min for the lifetime of the D-2 state is consistent with both the calculated lifetimes of 162 s for the D-2(3/2) level and 27.3 h for the D-2(5/2) level reported by O'Malley and Beck and 14.5 h and 12.5 h, respectively, from our Breit-Pauli calculations.
14.	Andersson, Patrik U, 1970, et al. (author) Formation of Highly Rovibrationally Excited Ammonia from Dissociative Recombination of NH4 2010 In: Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 1:17, s. 2519-2523 Journal article (peer-reviewed)abstract The internal energy distribution of ammonia formed in the dissociative recombination (DR) of NH4+ with electrons has been studied by an imaging technique at the ion storage ring CRYRING. The DR process resulted in the formation of NH3 + H (0.90 ± 0.01), with minor contributions from channels producing NH2 + H2 (0.05 ± 0.01) and NH2 + 2H (0.04 ± 0.02). The formed NH3 molecules were highly internally excited, with a mean rovibrational energy of 3.3 ± 0.4 eV, which corresponds to 70% of the energy released in the neutralization process. The internal energy distribution was semiquantitatively reproduced by ab initio direct dynamics simulations, and the calculations suggested that the NH3 molecules are highly vibrationally excited while rotational excitation is limited. The high internal excitation and the translational energy of NH3 and H will influence their subsequent reactivity, an aspect that should be taken into account when developing detailed models of the interstellar medium and ammonia-containing plasmas.
15.	Andreassen, B, et al. (author) Development of a scanning system for intensity modulated radiation therapy with photon pencil beams 2005 In: RADIOTHERAPY AND ONCOLOGY. - 0167-8140. ; 76, s. S106-S106 Conference paper (other academic/artistic)
16.	Bergmark, T., et al. (author) Status of the HESR electron cooler design work 2006 In: EPAC´06, Edenburg, Uk, 26-30 June 2006. Conference paper (other academic/artistic)
17.	Bohm, Christian, et al. (author) A MHz-repetition-rate hard X-ray free-electron laser driven by a superconducting linear accelerator 2020 In: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 14:6, s. 391-397 Journal article (peer-reviewed)abstract The European XFEL is a hard X-ray free-electron laser (FEL) based on a high-electron-energy superconducting linear accelerator. The superconducting technology allows for the acceleration of many electron bunches within one radio-frequency pulse of the accelerating voltage and, in turn, for the generation of a large number of hard X-ray pulses. We report on the performance of the European XFEL accelerator with up to 5,000 electron bunches per second and demonstrating a full energy of 17.5 GeV. Feedback mechanisms enable stabilization of the electron beam delivery at the FEL undulator in space and time. The measured FEL gain curve at 9.3 keV is in good agreement with predictions for saturated FEL radiation. Hard X-ray lasing was achieved between 7 keV and 14 keV with pulse energies of up to 2.0 mJ. Using the high repetition rate, an FEL beam with 6 W average power was created. The first operation of the European X-ray free-electron laser facility accelerator based on superconducting technology is reported. The maximum electron energy is 17.5 GeV. A laser average power of 6 W is achieved at a photon energy of 9.3 keV.
18.	Burgman, A., et al. (author) The ESSnuSB Design Study: Overview and Future Prospects 2023 In: Universe. - : MDPI. - 2218-1997. ; 9:8 Research review (peer-reviewed)abstract ESSnuSB is a design study for an experiment to measure the CP violation in the leptonic sector at the second neutrino oscillation maximum using a neutrino beam driven by the uniquely powerful ESS linear accelerator. The reduced impact of systematic errors on sensitivity at the second maximum allows for a very precise measurement of the CP violating parameter. This review describes the fundamental advantages of measurement at the second maximum, the necessary upgrades to the ESS linac in order to produce a neutrino beam, the near and far detector complexes, and the expected physics reach of the proposed ESSnuSB experiment, concluding with the near future developments aimed at the project realization.
19.	Burgman, A., et al. (author) The European Spallation Source neutrino super-beam conceptual design report 2022 In: The European Physical Journal Special Topics. - : Springer Nature. - 1951-6355 .- 1951-6401. ; 231:21, s. 3779-3955 Research review (peer-reviewed)abstract A design study, named ESSνSB for European Spallation Source neutrino Super Beam, has been carried out during the years 2018–2022 of how the 5 MW proton linear accelerator of the European Spallation Source under construction in Lund, Sweden, can be used to produce the world’s most intense long-baseline neutrino beam. The high beam intensity will allow for measuring the neutrino oscillations near the second oscillation maximum at which the CP violation signal is close to three times higher than at the first maximum, where other experiments measure. This will enable CP violation discovery in the leptonic sector for a wider range of values of the CP violating phase δCPδCP and, in particular, a higher precision measurement of δCPδCP. The present Conceptual Design Report describes the results of the design study of the required upgrade of the ESS linac, of the accumulator ring used to compress the linac pulses from 2.86 ms to 1.2 μs, and of the target station, where the 5 MW proton beam is used to produce the intense neutrino beam. It also presents the design of the near detector, which is used to monitor the neutrino beam as well as to measure neutrino cross sections, and of the large underground far detector located 360 km from ESS, where the magnitude of the oscillation appearance of νe from νμ is measured. The physics performance of the ESSνSB research facility has been evaluated demonstrating that after 10 years of data-taking, leptonic CP violation can be detected with more than 5 standard deviation significance over 70% of the range of values that the CP violation phase angle δCPδCP can take and that δCPδCP can be measured with a standard error less than 8° irrespective of the measured value of δCPδCP. These results demonstrate the uniquely high physics performance of the proposed ESSνSBESSνSB research facility.
20.	Burgman, A., et al. (author) Updated physics performance of the ESSnuSB experiment 2021 In: European Physical Journal C. - : Springer Nature. - 1434-6044 .- 1434-6052. ; 81:12 Journal article (peer-reviewed)abstract In this paper, we present the physics performance of the ESSnuSB experiment in the standard three flavor scenario using the updated neutrino flux calculated specifically for the ESSnuSB configuration and updated migration matrices for the far detector. Taking conservative systematic uncertainties corresponding to a normalization error of 5% for signal and 10% for background, we find that there is 10 sigma (13 sigma) CP violation discovery sensitivity for the baseline option of 540 km (360 km) at delta(CP) = +/- 90 degrees. The corresponding fraction of delta(CP )for which CP violation can be discovered at more than 5 sigma is 70%. Regarding CP precision measurements, the 1 sigma error associated with delta(CP )= 0 degrees is around 5 degrees and with delta(CP )= -90 degrees is around 14 degrees (7 degrees) for the baseline option of 540 km (360 km). For hierarchy sensitivity, one can have 3 sigma sensitivity for 540 km baseline except delta(CP) = +/- 90 degrees and 5 sigma sensitivity for 360 km baseline for all values of delta(CP). The octant of theta(23) can be determined at 30 for the values of: theta(23) > 51 degrees (theta(23) < 42 degrees and theta(23) > 49 degrees) for baseline of 540 km (360 km). Regarding measurement precision of the atmospheric mixing parameters, the allowed values at 3 sigma are: 40 degrees < theta(23) < 52 degrees (42 degrees < theta(23) < 51.5 degrees) and 2.485 x 10(-3) eV(2) < Delta(2)(m31) < 2.545 x 10(-3) eV(2) (2.49x 10(-3 ) eV(2) < Delta(2)(m31) < 2.54 x 10(-3) eV(2)) for the baseline of 540 km (360 km).
21.	Böhm, S, et al. (author) Experimental NV and NeVIII low-temperature dielectronic recombination rate coefficients 2005 In: Astronomy & Astrophysics. - 0004-6361. ; 437:3, s. 1151-1157 Journal article (peer-reviewed)abstract The dielectronic recombination rate coefficients of Nv and Ne viii ions have been measured at a heavy-ion storage ring. The investigated energy ranges covered all dielectronic recombination resonances attached to 2s -> 2p (delta_n = 0) core excitations. The rate coefficients in a plasma are derived and parameterized by using a convenient fit formula. The experimentally derived rate coefficients are compared with theoretical data by Colgan et al. (2004, A&A, 417, 1183) and Nahar & Pradhan (1997, ApJ, 111, 339) as well as with the recommended rate coefficients by Mazzotta et al. (1998, A&A, 133, 403). The data of Colgan et al. and Nahar & Pradhan reproduce the experiment very well over the temperature ranges where Nv and Ne viii are expected to exist in photoionized as well as in collisionally ionized plasmas. In contrast the recommendation of Mazzotta et al. agrees with the experimental rate coefficient only in the collisionally ionized temperature range. At lower temperatures it deviates from the measured rate coefficient by orders of magnitude. In addition the influence of external electric fields with field strengths up to 1300 V/cm on the dielectronic recombination rate coefficient has been investigated.
22.	Collins, G F, et al. (author) Electron-impact fragmentation of Cl-2(-) 2005 In: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 72:4, s. 042708- Journal article (peer-reviewed)abstract A merged beam technique has been used to investigate the fragmentation of the Cl-2(-) ion in collisions with electrons over an energy range of 0-200 eV. We have measured absolute cross sections for detachment, detachment plus dissociation and dissociation processes. Over the energy range studied, the dominant breakup mechanism is dissociation. Dissociation is relatively enhanced in the e(-)+Cl-2(-) collision system due to the suppression of the normally dominant detachment process, as a result of the large difference between the equilibrium internuclear distances of the Cl-2 and Cl-2(-) ground state potential curves. A prominent structure is observed just above the threshold in the Cl-+Cl+e(-) dissociation channel. It is proposed that the structure is a resonance associated with production and rapid decay of an excited state of the doubly charged Cl-2(-) ion. A plausible mechanism for production of the di-anionic state based on an excitation plus capture process is suggested.
23.	Eklöw, N, et al. (author) Magnetic-field dependence in electron-deuteron recombination at very low relative energy 2000 In: Hyperfine Interactions. - 0304-3843 .- 1572-9540. ; 127:1-4, s. 251-255 Journal article (peer-reviewed)abstract The rate coefficient for recombination of D+ with low-energy electrons has been measured at different magnetic fields in the interaction region of the electron cooler at CRYRING. It is found that the measured recombination rate coefficient is influenced by the magnetic field.
24.	Ellmann, A, et al. (author) Radiative lifetime of a bound excited state of Te- 2004 In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 92:25, s. 253002- Journal article (peer-reviewed)abstract We report on the first experimental study of the lifetime of a bound excited state of a negative ion. A new experimental technique was developed and used to measure the radiative lifetime of the 5p(5) P-2(1/2) level of Te-. The experiment was performed in a magnetic storage ring, where a laser beam was applied along one of the straight sections. In the experiment the population of the excited J=1/2 level was probed each time the Te- ions passed through the laser field. A decay curve was built up by sampling the population of the excited level of the Te- ions as a function of time after injection into the ring. A multiconfiguration Dirac-Hartree-Fock calculation was performed in conjunction with the experiment. The calculation yielded a radiative lifetime of 0.45 s, in excellent agreement with the measured value of 0.42(5) s.
25.	Fritioff, Karin, et al. (author) Observation of an excited C2-4 ion 2004 In: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 37:11, s. 2241-2246 Journal article (peer-reviewed)abstract This paper reports an experimental investigation of the electron impact detachment of C−4. We observe structure in the electron impact cross section for detaching a single electron from a C−4 cluster anion, which we attribute to the formation and decay of the C2−4 dianion. The system is energetically unstable and very rapidly decays via double autodetachment. The energy and width of the resonance were determined to be 8.8(5) eV and 1.4(5) eV, respectively, and the resonance lies 1.5(5) eV above the ground state of the neutral system. The experiment was conducted by merging monoenergetic electron and ion beams in the heavy ion storage ring CRYRING. The detachment channel was monitored by detecting neutral C4 fragments.
26.	Fritioff, K, et al. (author) Single and double detachment from H- 2004 In: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622 .- 2469-9926 .- 2469-9934. ; 69:4, s. 042707- Journal article (peer-reviewed)abstract Absolute cross sections for single and double detachment from H- following electron impact have been measured over a range of collision energies from the thresholds to 170 eV. The measurements were made using a magnetic storage ring. The ions in the ring were merged with a monoenergetic electron beam and neutral and positively charged fragments were detected. We cover larger energy ranges than in many of the previous experiments, and this is the first time both single and double detachment have been measured simultaneously. This allows us to present accurate ratios between the single and double detachment cross sections. On the basis of these ratio measurements we discuss possible mechanisms leading to double detachment.
27.	Glans, Peter, et al. (author) Dielectronic recombination of Li-like fluorine ions 1999 In: Nuclear Instruments & Methods in Physics Research, Section B (Beam Interactions with Materials and Atoms). - 0168-583X. ; 154:1-4, s. 97-101 Journal article (peer-reviewed)abstract Some recent new developments in dielectronic recombination (DR) measurements at heavy-ion storage rings are presented. A DR spectrum measured at CRYRING in Stockholm of F6+ is used to illustrate a few points regarding this kind of measurements. From the spectrum a transversal temperature of the adiabatically expanded electron beam of 3.0(5) meV is deduced, which is slightly higher than expected.
28.	Hartman, Henrik, et al. (author) First storage of ion beams in the Double Electrostatic Ion-Ring Experiment : DESIREE 2013 In: Review of Scientific Instruments. - : American Institute of Physics (AIP). - 0034-6748 .- 1089-7623. ; 84:5 Journal article (peer-reviewed)abstract We report on the first storage of ion beams in the Double ElectroStatic Ion Ring ExpEriment, DESIREE, at Stockholm University. We have produced beams of atomic carbon anions and small carbon anion molecules (Cn-, n = 1, 2, 3, 4) in a sputter ion source. The ion beams were accelerated to 10 keV kinetic energy and stored in an electrostatic ion storage ring enclosed in a vacuum chamber at 13 K. For 10 keV C2- molecular anions we measure the residual-gas limited beam storage lifetime to be 448 s +/- 18 s with two independent detector systems. Using the measured storage lifetimes we estimate that the residual gas pressure is in the 10-14 mbar range. When high current ion beams are injected, the number of stored particles does not follow a single exponential decay law as would be expected for stored particles lost solely due to electron detachment in collision with the residual-gas. Instead, we observe a faster initial decay rate, which we ascribe to the effect of the space charge of the ion beam on the storage capacity.
29.	Lestinsky, M., et al. (author) CRYRING@ESR: present status and future research 2015 In: Physica Scripta. - : IOP Publishing. - 1402-4896 .- 0031-8949. ; 2015:T166 Conference paper (peer-reviewed)abstract The former storage ring CRYRING has been shipped from the Manne Siegbahn Laboratory in Stockholm to Darmstadt as a Swedish in-kind contribution to FAIR. At its new location downstream of ESR all ion species presently accessible in ESR can be transferred to CRYRING, in which ions with rigidities between 1.44 and 0.054 Tm can be stored. The original Swedish layout has been modified by reconfiguring the sequence of straight sections and by slightly increasing the circumference to ESR/2. Ions can be injected from ESR or from an independent 300 keV/u RFQ test injector. The instrumentation of the ring includes an RF drift tube system for acceleration and deceleration (1 T s(-1), with a possibility for an upgrade to 7 T s(-1)), electron cooling, a free experimental section, and both fast and slow extraction of ions. We report on the present progress of this project, give a prospective timeline, and summarize the new research which will be enabled by this project. First beam for commissioning of the storage ring is expected for 2015, final bakeout to restore ultrahigh vacuum conditions in 2016 and ion beams injected through ESR in similar to 2017.
30.	Lindroos, M., et al. (author) ESS progressing into construction 2016 In: IPAC 2016 - Proceedings of the 7th International Particle Accelerator Conference. - 9783954501472 ; , s. 4266-4270 Conference paper (peer-reviewed)abstract The construction of the European Spallation Source, ESS, started in summer 2014. At the site in Lund, the accelerator tunnel will be completed at the time of IPAC16, while prototyping and manufacturing or preparations for manpower contributions are going on in more 23 laboratories distributed over the 12 European countries collaborating on the accelerator project. Major technical milestones have been reached include the testing of superconducting cavity prototypes of two families to values above design gradients, the first ESS modulator has been tested to 90 kV and the first klystron prototype has been received in April 2016. Equally important developments are taking place at many partner laboratories. The presentation will summarize the status of the ESS accelerator project by the time of IPAC16.
31.	Schuch, R, et al. (author) A first study of dielectronic recombination with the super-expanded electron beam in CRYRING 1998 In: Hyperfine Interactions. - 0304-3843. ; 115:1-4, s. 123-127 Journal article (peer-reviewed)abstract A first temperature measurement of the expanded electron beam from a super-conducting magnet in the cooler of CRYRING is reported. It is based on detection of a dielectronic recombination resonance in C2+. For this measurement C3+ was stored in the ring at 3 MeV/amu energy. A fit to the resonance with free transverse and longitudinal temperatures gave 3.9 x 10(-3) eV and 4.5 x 10(-5) eV,respectively. The result is also compatible with the values of 10(-3) eV for the transverse and 6.7 x 10(-5) eV for the longitudinal component, in good agreement with expected values.
32.	Thomas, Richard D., et al. (author) The double electrostatic ion ring experiment : A unique cryogenic electrostatic storage ring for merged ion-beams studies 2011 In: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 82:6, s. 065112- Journal article (peer-reviewed)abstract We describe the design of a novel type of storage device currently under construction at Stockholm University, Sweden, using purely electrostatic focussing and deflection elements, in which ion beams of opposite charges are confined under extreme high vacuum cryogenic conditions in separate rings and merged over a common straight section. The construction of this double electrostatic ion ring experiment uniquely allows for studies of interactions between cations and anions at low and well-defined internal temperatures and centre-of-mass collision energies down to about 10 K and 10 meV, respectively. Position sensitive multi-hit detector systems have been extensively tested and proven to work in cryogenic environments and these will be used to measure correlations between reaction products in, for example, electron-transfer processes. The technical advantages of using purely electrostatic ion storage devices over magnetic ones are many, but the most relevant are: electrostatic elements which are more compact and easier to construct; remanent fields, hysteresis, and eddy-currents, which are of concern in magnetic devices, are no longer relevant; and electrical fields required to control the orbit of the ions are not only much easier to create and control than the corresponding magnetic fields, they also set no upper mass limit on the ions that can be stored. These technical differences are a boon to new areas of fundamental experimental research, not only in atomic and molecular physics but also in the boundaries of these fields with chemistry and biology. For examples, studies of interactions with internally cold molecular ions will be particular useful for applications in astrophysics, while studies of solvated ionic clusters will be of relevance to aeronomy and biology.
33.	Tokman, M, et al. (author) Towards a determination of QED effects in Cu-like Pb recombination resonances near threshold 2001 In: Physica Scripta. Topical Issues. - 0281-1847. ; T92, s. 406-409 Journal article (peer-reviewed)abstract Dielectronic recombination of Pb53+ has been studied and a resonance is detected only similar to 10(-4) eV above the ground state. The possibility to determine the Pb53+ (4p(1/2)) - Ph53+ (4s(1/2)) energy splitting with a similar accuracy from the determination of the resonance position is discussed. Such a precision can only be achieved by calculations which treat quantum electrodynamics (QED) in a many-body environment at a level which can still not be reached. A fully relativistic many-body calculation of the splitting is described and the uncertainties are discussed.
34.	Öjekull, Jenny, 1973, et al. (author) Dissociative recombination of ammonia clusters studied by storage ring experiments 2006 In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 125:19, s. 194306- Journal article (peer-reviewed)abstract Dissociative recombination of ammonia cluster ions with free electrons has been studied at the heavy-ion storage ring CRYRING (Manne Siegbahn Laboratory, Stockholm University). The absolute cross sections for dissociative recombination of H+(NH3)(2), H+(NH3)(3), D+(ND3)(2), and D+(ND3)(3) in the collision energy range of 0.001-27 eV are reported, and thermal rate coefficients for the temperature interval from 10 to 1000 K are calculated from the experimental data and compared with earlier results. The fragmentation patterns for the two ions H+(NH3)(2) and D+(ND3)(2) show no clear isotope effect. Dissociative recombination of X+(NX3)(2) (X=H or D) is dominated by the product channels 2NX(3)+X [0.95 +/- 0.02 for H+(NH3)(2) and 1.00 +/- 0.02 for D+(ND3)(2)]. Dissociative recombination of D+(ND3)(3) is dominated by the channels yielding three N-containing fragments (0.95 +/- 0.05).
35.	Öjekull, Jenny, 1973, et al. (author) Dissociative recombination of H+(H2O)3 and D+(D2O)3 water cluster ions with electrons: Cross sections and branching ratios 2007 In: The Journal of chemical physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 127, s. 194301-194309 Journal article (peer-reviewed)abstract Dissociative recombination (DR) of the water cluster ions H+(H2O)3 and D+(D2O)3 with electrons has been studied at the heavy-ion storage ring CRYRING (Manne Siegbahn Laboratory, Stockholm University). For the first time, absolute DR cross sections have been measured for H+(H2O)3 in the energy range of 0.001–0.8 eV, and relative cross sections have been measured for D+(D2O)3 in the energy range of 0.001–1.0 eV. The DR cross sections for H+(H2O)3 are larger than previously observed for H+(H2O)n (n=1,2), which is in agreement with the previously observed trend indicating that the DR rate coefficient increases with size of the water cluster ion. Branching ratios have been determined for the dominating product channels. Dissociative recombination of H+(H2O)3 mainly results in the formation of 3H2O+H (probability of 0.95±0.05) and with a possible minor channel resulting in 2H2O+OH+H2 (0.05±0.05). The dominating channels for DR of D+(D2O)3 are 3D2O+D (0.88±0.03) and 2D2O+OD+D2 (0.09±0.02). The branching ratios are comparable to earlier DR results for H+(H2O)2 and D+(D2O)2, which gave 2X2O+X (X=H,D) with a probability of over 0.9.
36.	Öjekull, Jenny, 1973, et al. (author) Dissociative recombination of water cluster ions with free electrons : Cross sections and branching ratios 2008 In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 128:4, s. 44311- Journal article (peer-reviewed)abstract Dissociative recombination (DR) of water cluster ions H+(H2O)(n) (n=4-6) with ree electrons has been studied at the heavy-ion storage ring CRYRING (Manne Siegbahn Laboratory, Stockholm University). For the first time, branching ratios have been determined for the dominating product channels and absolute DR cross sections have been measured in the energy range from 0.001 to 0.7 eV. Dissociative recombination is concluded to result in extensive fragmentation for all three cluster ions, and a maximum number of heavy oxygen-containing fragments is produced with a probability close to unity. The branching ratio results agree with earlier DR studies of smaller water cluster ions where the channel nH(2)O+H has been observed to dominate and where energy transfer to internal degrees of freedom has been concluded to be highly efficient. The absolute DR cross sections for H+(H2O)(n) (n=4-6) decrease monotonically with increasing energy with an energy dependence close to E-1 in the lower part of the energy range and a faster falloff at higher energies, in agreement with the behavior of other studied heavy ions. The cross section data have been used to calculate DR rate coefficients in the temperature range of 10-2000 K. The results from storage ring experiments with water cluster ions are concluded to partly confirm the earlier results from afterglow experiments. The DR rate coefficients for H+(H2O)(n) (n=1-6) are in general somewhat lower than reported from afterglow experiments. The rate coefficient tends to increase with increasing cluster size, but not in the monotonic way that has been reported from afterglow experiments. The needs for further experimental studies and for theoretical models that can be used to predict the DR rate of polyatomic ions are discussed.

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