| 1. |
- Andersson, Åke, et al.
(författare)
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Future development plans for the MAX IV light source: Pushing further towards higher brightness and coherence
- 2018
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048. ; 224
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Tidskriftsartikel (refereegranskat)abstract
- The commissioning of the MAX IV synchrotron radiation facility in Lund marks the dawn of a new generation of storage-ring-based light sources. This new generation delivers one order of magnitude higher performance and allows realization of groundbreaking experiments on a variety of systems and materials at the atomic and molecular levels. This paper reviews the conceptual basis of the MAX IV design, briefly summarizes the most recent accelerator commissioning results and focusses on exploring a future development path for the MAX IV 3 GeV storage ring aimed at achieving the diffraction limit at hard x-ray wavelengths.
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| 2. |
- Cerenius, Yngve, et al.
(författare)
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Status of the MAX IV Laboratory
- 2016
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Ingår i: Synchrotron Radiation News. - : Informa UK Limited. - 0894-0886 .- 1931-7344. ; 29:1, s. 34-38
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Tidskriftsartikel (refereegranskat)abstract
- On the day of the 2016 summer solstice, June 21, MAX IV, the new synchrotron radiation facility in Lund, Sweden, will be inaugurated. MAX IV is setting a new standard in terms of emittance, thereby providing beamlines with the best possible brilliance and coherence. At the same time, MAX IV continues a more than three-decades-long successful history of Swedish synchrotron-radiation-based research. The activities at the present MAX-lab, which officially started when the MAX I storage ring opened for users in 1986, have been concluded with a “last beamdump” ceremony for the MAX II and MAX III storage rings on December 13, 2015, Saint Lucy's Day. In Sweden, the winter solstice is celebrated with a festival of light.
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| 3. |
- Cullinan, F. J., et al.
(författare)
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The damping of transverse coherent instabilities by harmonic cavities
- 2015
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Ingår i: 6th International Particle Accelerator Conference, IPAC 2015. - 9783954501687 ; , s. 102-105
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Konferensbidrag (refereegranskat)abstract
- At nonzero chromaticity, the threshold current due to transverse coupled bunch instabilities in an electron storage ring is defined by intrabunch head-tail motion of higher than zeroth order. Multibunch tracking simulations predict that this threshold can be increased to several times its original value through the introduction of bunch lengthening harmonic cavities. One previously suggested explanation is the narrower spectra of the elongated bunches but reliable estimates for the threshold currents are not obtainable for anything other than rigid beam motion since the usual Sacherer formalism is not directly applicable to beams in a non-harmonic potential. A new scheme has been developed in which the decay time of a higher than zeroth order transverse head-tail mode may be estimated by taking into account the synchrotron tune spread generated by the harmonic cavity potential. This scheme is presented along with the results of numerical simulations performed in order to confirm the analytical predictions and justify the assumptions made. The extension of the scheme to more complex scenarios is also discussed.
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| 4. |
- Cullinan, F. J., et al.
(författare)
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Transverse coherent instabilities in storage rings with harmonic cavities
- 2016
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Ingår i: IPAC 2016 - Proceedings of the 7th International Particle Accelerator Conference. - 9783954501472 ; , s. 1061-1064
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Konferensbidrag (refereegranskat)abstract
- Many current and future synchrotron light sources employ harmonic cavities to lengthen the electron bunches in order to reduce the emittance dilution caused by intrabeam scattering. In some cases, the harmonic cavities may be tuned to fulfill the flat potential condition. For this condition, a large increase in the threshold currents of transverse coupled-bunch instabilities has been predicted and recently, the physical content behind this stabilisation has been better understood. With this in mind, an investigation is made into the effectiveness of harmonic cavities for different machines. Frequency domain computations employing Laclare's eigenvalue method have been used to investigate the influence of several machine parameters and the results are presented.
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| 5. |
- Cullinan, F. J., et al.
(författare)
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Transverse coupled-bunch instability thresholds in the presence of a harmonic-cavity-flattened rf potential
- 2016
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Ingår i: Physical Review Special Topics - Accelerators and Beams. - 1098-4402. ; 19:12
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Tidskriftsartikel (refereegranskat)abstract
- A small vacuum chamber aperture is a present trend in the design of future synchrotron light sources. This leads to a large resistive-wall impedance that can drive coupled-bunch instabilities. Another trend is the use of passively driven cavities at a harmonic of the main radio frequency to lengthen the electron bunches in order to increase the Touschek lifetime and reduce emittance blowup due to intrabeam scattering. In some cases, the harmonic cavities may be tuned to fulfill the flat potential condition. With this condition met, it has been predicted in simulation that the threshold current for coupled-bunch resistive-wall instabilities is much higher than with no bunch lengthening at all. In this paper, the features of a bunch in the flat potential that would contribute toward this stabilization are identified and discussed. The threshold currents for these instabilities are estimated for the MAX IV 3 GeV storage ring at different values of chromaticity using macroparticle simulations in the time domain and, within the limits of the existing theory, frequency domain calculations. By comparing the results from these two methods and analyzing the spectra of the dominant head-tail modes, the impact of each of the distinguishing features of a bunch in the flat potential can be explained and quantified in terms of the change in threshold current. It is found that, above a certain chromaticity, the threshold current is determined by the radial structure of the zeroth-order head-tail mode. This happens at a lower chromaticity if the bunch length is longer.
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| 6. |
- Fernandes, Ricardo M.F. 1983-, et al.
(författare)
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Strong Spacer Length Effects on The Thermal Behavior and Mesophase Formation By Gemini Surfactants
- 2015
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The self-aggregation properties in aqueous solution of gemini surfactants of the type alkanediyl-α,ω-bis(dodecyldimethylammonium bromides), 12-s-12, have been extensively reported and are known to be significantly influenced by the number of methylene groups, s, of the covalent spacer. In contrast, the thermal behavior of the anhydrous compounds as a function of varying s has not been investigated in a similarly systematic way. Herein, we present the thermal phase behavior of eight compounds of the 12-s-12 family (with s = 2-6, 8, 10 and 12), resorting to differential scanning calorimetry (DSC), polarized light microscopy (PLM) and X-ray diffraction (XRD). We find that compounds with either the shortest spacer, s = 2, or the longest ones—8, 10 and 12—form several smectic liquid-crystalline phases prior to isotropization to the liquid phase, with appearance of oily streaks, focal conics, mosaic and fan-shaped birefringent textures. In sharp contrast, gemini compounds with intermediate spacers, s = 3-6, decompose and do not form any disordered, fluid mesophases. Both the DSC thermodynamic parameters for the phase transitions and d00l spacings obtained from XRD show non-monotonic trends with spacer variation, indicating that there are significant differences in solid-state packing and melting process. Plausible molecular packing arrangements in the solid-state are presented, consistent with the XRD information and geometric considerations, and their influence on the phase behavior trends critically discussed.
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| 7. |
- Johansson, Martin, et al.
(författare)
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MAX IV 3 GeV storage ring magnet block production series measurement results
- 2015
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Ingår i: 6th International Particle Accelerator Conference, IPAC 2015. - 9783954501687 ; , s. 3069-3071
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Konferensbidrag (refereegranskat)abstract
- The magnet design of the MAX IV 3 GeV storage ring replaces the conventional support girder + discrete magnets scheme of previous third-generation synchrotron radiation light sources with a compact (Ø25 mm aperture) integrated design having several consecutive magnet elements precision-machined out of a common solid iron block. The production series of 140 integrated magnet block units, which was totally outsourced to industry, was completed mid-2014. This article presents mechanical and magnetic field measurement results of the full production series.
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| 8. |
- Johansson, Martin, et al.
(författare)
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MAX IV 3 GeV storage ring magnet block production series measurement results
- 2016
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Ingår i: IPAC 2016 - Proceedings of the 7th International Particle Accelerator Conference. - 9783954501472 ; , s. 1157-1159
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Konferensbidrag (refereegranskat)abstract
- The MAX IV 3 GeV storage ring magnets are integrated "magnet block" units consisting of several consecutive magnet elements precision-machined out of a common solid iron block. In the 3 GeV ring, there are 140 magnet blocks containing a total of 1320 magnet elements. During the manufacturing phase of the project, a field measurement was performed for each magnet element, by Hall probe and/or by rotating coil. This article presents an overview of the magnetic field measurement results that were obtained for the full production series.
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| 9. |
- Leemann, Simon, et al.
(författare)
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Commissioning of the MAX IV Light Source
- 2016
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Ingår i: IPAC 2016 - Proceedings of the 7th International Particle Accelerator Conference. - 9783954501472 ; , s. 11-15
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The first of the so-called diffraction-limited storage rings (DLSRs), MAX I V, has now gone into operation. For this ring, a multibend achromat (MBA) lattice is employed in order to achieve a small electron beam emittance. Several non-conventional technical system solutions have been introduced in order to reduce size, cost, assembly time, installation effort and to increase the ring robustness. Examples of this are solid magnet blocks housing several magnet items, a fully NEG-coated vacuum system and a low frequency RF system. The commissioning started in late August 2015. Several base-line parameters have now been reached like a sufficiently high stored circulating current, beam lifetime and beam quality for beamline commissioning. The MBA concept and the operation of the non-conventional solutions technical systems are verified. This article describes some of the technical solutions chosen and the early commissioning results.
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| 10. |
- Skripka, G., et al.
(författare)
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Commissioning of the harmonic cavities in the MAX IV 3 GeV ring
- 2016
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Ingår i: IPAC 2016 - Proceedings of the 7th International Particle Accelerator Conference. - 9783954501472 ; , s. 2911-2913
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Konferensbidrag (refereegranskat)abstract
- The MAX IV 3 GeV storage ring operates with beam of high current and ultralow emittance. These beam parameters in combination with the small effective aperture enhance possible collective beam instabilities. Three passive harmonic cavities are installed to introduce bunch lengthening and tune spread, leading to decoupling of the bunch spectrum from the machine effective impedance and mitigating instabilities by Landau damping respectively. In this paper we present the first results of the commissioning of the passive third harmonic cavities in the MAX IV 3 GeV ring. The additional harmonic cavity potential significantly improved the beam lifetime. First observations of the harmonic cavity effect on the damping of collective beam instabilities are discussed.
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| 11. |
- Skripka, Galina, et al.
(författare)
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Simultaneous computation of intrabunch and interbunch collective beam motions in storage rings
- 2016
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 806, s. 221-230
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Tidskriftsartikel (refereegranskat)abstract
- We present the multibunch tracking code mbtrack developed to simulate, in 6-dimensional phase space, single- and multibunch collective instabilities driven by short- and long-range wakefields in storage rings. Multiple bunches, each composed of a large number of macroparticles, are tracked, allowing simulation of both intra- and interbunch motions. Besides analytical impedance models, the code allows employment of numerical wake potentials computed with electromagnetic (EM) field solvers. The corresponding impedances are fitted to a number of known analytical functions and the coefficients obtained in the fit are used as an input to the code. mbtrack performs a dynamic treatment of long-range resistive-wall and harmonic cavity fields, which are likely to be the two major factors impacting multibunch collective motions in many present and future ring-based light sources. Furthermore, it is capable of simulating beam-ion interactions as well as transverse bunch-by-bunch feedback. We describe the physical effects considered in the code and their implementation, which makes use of parallel processing to significantly shorten the computation time. mbtrack is benchmarked against other codes and applied to the MAX IV 3 GeV ring as an example, where the importance of the interplay of various physical effects as well as coupling among different degrees of freedom is demonstrated.
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