| 1. |
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| 2. |
- Andersson, Joel, et al.
(författare)
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New features of the MAX IV thermionic pre-injector
- 2017
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Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 855, s. 65-80
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Tidskriftsartikel (refereegranskat)abstract
- The MAX IV facility in Lund, Sweden consists of two storage rings for production of synchrotron radiation. The smaller 1.5 GeV ring is presently under construction, while the larger 3 GeV ring is being commissioned. Both rings will be operating with top-up injections from a full-energy injector. During injection, the electron beam is first delivered to the main injector from a thermionic pre-injector which consists of a thermionic RF gun, a chopper system, and an energy filter. In order to reduce losses of high-energy electrons along the injector and in the rings, the electron beam provided by the thermionic pre-injector should have the correct time structure and energy distribution. In this paper, the design of the MAX IV thermionic pre-injector with all its sub components is presented. The electron beam delivered by the pre-injector and its dependence on parameters such as optics, cathode temperature, and RF power are studied. Measurements are here compared with simulation results obtained by particle tracking and electromagnetic codes. The chopper system is described in detail, and different driving schemes that optimize the injection efficiency for the two storage rings are investigated. During operation, it was discovered that the structure of the beam delivered by the gun is affected by mode beating between the accelerating and a low-order mode. This mode beating is also studied in detail. Finally, initial measurements of the electron beam delivered to the 3 GeV ring during commissioning are presented.
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| 3. |
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| 4. |
- Björklund Svensson, Jonas, et al.
(författare)
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Double-bunches for two-color soft X-ray free-electron laser at the MAX IV Laboratory
- 2018
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Ingår i: Proceedings of FEL2017, Santa Fe, NM, USA. - 9783954501793 ; , s. 269-272
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The ability to generate two-color free-electron laser (FEL) radiation enables a wider range of user experiments than just single-color FEL radiation. There are different schemes for generating the two colors, the original being to use a single bunch and two sets of undulators with different K-parameters. An alternative scheme was recently shown, where two separate bunches in the same RF bucket are used for lasing at different wavelengths in a single set of undulators. We here investigate the feasibility of accelerating and compressing a double-bunch time structure generated in the photocathode electron gun for subsequent use in a soft X-ray FEL at the MAX IV Laboratory.
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| 5. |
- Björklund Svensson, Jonas, et al.
(författare)
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Driver-witness-bunches for plasma-wakefield acceleration at the MAX IV Linear Accelerator
- 2017
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Ingår i: IPAC 2017 - Proceedings of the 8th International Particle Accelerator Conference. - 9783954501823 ; , s. 1743-1746
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Beam-driven plasma-wakefield acceleration is an acceleration scheme promising accelerating fields of at least two to three orders of magnitude higher than in conventional radiofrequency accelerating structures. The scheme relies on using a charged particle bunch (driver) to drive a non-linear plasma wake, into which a second bunch (witness) can be injected at an appropriate distance behind the first, yielding a substantial energy gain of the witness bunch particles. This puts very special demands on the machine providing the particle beam. In this article, we use simulations to show that, if driver-witness-bunches can be generated in the photocathode electron gun, the MAX IV Linear Accelerator could be used for plasma-wakefield acceleration.
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| 6. |
- Curbis, Francesca, et al.
(författare)
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Commissioning of the test fel at MAX-Lab
- 2008
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Ingår i: Proceedings of FEL08. ; , s. 556-559
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Konferensbidrag (refereegranskat)abstract
- An installation for testing techniques related to seeding and harmonic generation has been completed at MAXlab. The aim is to study the processes around seeded harmonic generation at 130/88/54 nm, the 2/3/5 harmonic of a Ti: Sapphire laser. During the spring 2008 the commissioning work has begun and this paper will report on the progress. The test FEL is built around the existing linac injector at MAX-lab. This source can provide 4-500 MeV electrons from an RF-gun. A combined laser system both driving the photo cathode in the gun and, synchronised via an optical fibre, the seed laser pulse has been put into operation. An optical klystron, consisting of two 30 period undulators and a 4-magnet chicane, is in operation. Beam loss monitors along the optical klystron are in use and a THz system for additional synchronisation studies installed. Results from electron beam optics and operation generating spontaneous radiation is already available and synchronisation results immediate. The work is in progress and new results are added continuously to the portfolio.
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| 7. |
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| 8. |
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| 9. |
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| 10. |
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| 11. |
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| 12. |
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| 13. |
- Curbis, Francesca, et al.
(författare)
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Towards an X-ray FEL at the MAX IV laboratory
- 2014
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Ingår i: Proceedings of the 36th International Free Electron Laser Conference, FEL 2014. - 9783954501335 ; , s. 549-552
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Konferensbidrag (refereegranskat)abstract
- The design of the 3 GeV linac for the MAX IV facility was done to provide the ability to host a future FEL in the hard X-ray as well as in the soft X-ray range. The linear accelerator, with its two bunch compressors, is now under commissioning. Through the years increasing details for the actual FEL have been discussed and presented. In parallel a steering group for the science case for a Swedish FEL has worked and engaged a large number of Swedish user groups. These two paths are now converging into a joint project to develop the concept of an FEL at MAX IV. We will report on the paths to FEL performance based on the 3 GeV injector, FEL design considerations, the scientific preparation of the project, the linac commissioning and the strategy and priorities.
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| 14. |
- Cutic, Nino, et al.
(författare)
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SEEDING OF THE TEST-FEL AT MAX-LAB
- 2008
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Ingår i: Proceedings of EPAC08. ; , s. 76-78
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Konferensbidrag (refereegranskat)abstract
- The installation of the test FEL at MAX-lab has recently been completed. The system will be seeded by a tripled Ti:Sapphire laser (263 nm) synchronized to the RF system and the gun laser. Issues important for the seeding will be presented, ranging from the laser system via the layout of photon and electron optics to timing/synchronization and the theoretical approach.
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| 15. |
- Enquist, Henrik, et al.
(författare)
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FemtoMAX - An X-ray beamline for structural dynamics at the short-pulse facility of MAX IV
- 2018
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Ingår i: Journal of Synchrotron Radiation. - 0909-0495. ; 25:2, s. 570-579
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Tidskriftsartikel (refereegranskat)abstract
- The FemtoMAX beamline facilitates studies of the structural dynamics of materials. Such studies are of fundamental importance for key scientific problems related to programming materials using light, enabling new storage media and new manufacturing techniques, obtaining sustainable energy by mimicking photosynthesis, and gleaning insights into chemical and biological functional dynamics. The FemtoMAX beamline utilizes the MAX IV linear accelerator as an electron source. The photon bursts have a pulse length of 100fs, which is on the timescale of molecular vibrations, and have wavelengths matching interatomic distances (Å). The uniqueness of the beamline has called for special beamline components. This paper presents the beamline design including ultrasensitive X-ray beam-position monitors based on thin Ce:YAG screens, efficient harmonic separators and novel timing tools.The FemtoMAX beamline facilitates studies of the structural dynamics of materials on the femtosecond timescale. The first commissioning results are presented.
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| 16. |
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| 17. |
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| 18. |
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| 19. |
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| 20. |
- Mak, Alan, et al.
(författare)
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FEL Operation Modes of the MAX IV Short Pulse Facility
- 2015
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Ingår i: Proceedings of FEL 2015, Daejeon, Korea. - 9783954501342 ; , s. 241-241
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The Short Pulse Facility (SPF) of the MAX IV Laboratory in Lund, Sweden features the production of ultrashort, incoherent x-ray pulses. It is driven by a 3-GeV linac and comprises two 5-metre undulator modules. While the SPF is designed for spontaneous radiation, we explore alternative operation modes in which the SPF functions as a simple free-electron laser (FEL). In this article, we characterize two of them in time-dependent numerical simulations. We perform a sensitivity study on the electron beam parameters and examine the technique of single-step tapering.
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| 21. |
- Mak, Alan, et al.
(författare)
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Further Studies of Undulator Tapering in X-Ray FELs
- 2015
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Ingår i: Proceedings of FEL 2015, Daejeon, Korea. - 9783954501342 ; , s. 321-321
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We further the studies of the model-based optimization of tapered free-electron lasers presented in a recent publication [Phys. Rev. ST Accel. Beams 18, 040702 (2015)]. Departing from the ideal case, wherein the taper profile is a smooth and continuous function, we consider the more realistic case, with individual undulator segments separated by break sections. Using the simulation code GENESIS, we apply our taper optimization method to a case, which closely resembles the FLASH2 facility in Hamburg, Germany. By comparing steady-state and time-dependent simulations, we examine how time-dependent effects alter the optimal taper scenario. From the simulation results, we also deduce that the "traditional" empirical method, whereby the intermediate radiation power is maximized after closing every undulator gap, does not necessarily produce the highest final power at the exit of the undulator line.
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| 22. |
- Mak, Alan, et al.
(författare)
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Methods for the Optimization of a Tapered Free-Electron Laser
- 2014
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Ingår i: Proceedings of IPAC 2014, Dresden, Germany. - 9783954501328 ; , s. 2909-2911
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In a free-electron laser (FEL), the technique of wiggler tapering enables the sustained growth of radiation power beyond the initial saturation. With the goal to develop anX-ray FEL in the terawatt power regime, it is important to utilize this technique and optimize the taper profile,giving the wiggler parameter as a function of the distance along the wiggler line. This article examines two methods of optimization, which are based on the theoretical analysis by Kroll, Morton and Rosenbluth (KMR). Using the numerical simulation code GENESIS, the methods are applied to a case for the possible future FEL at the MAX IV Laboratory, as well as a case for the LCLS-II.
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| 23. |
- Mak, Alan, et al.
(författare)
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Model-Based Optimization of Tapered Free-Electron Lasers
- 2015
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Ingår i: Physical Review Special Topics - Accelerators and Beams. - 1098-4402. ; 18:4
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Tidskriftsartikel (refereegranskat)abstract
- The energy extraction efficiency is a figure of merit for a free-electron laser (FEL). It can be enhanced by the technique of undulator tapering, which enables the sustained growth of radiation power beyond the initial saturation point. In the development of a single-pass x-ray FEL, it is important to exploit the full potential of this technique and optimize the taper profile aw(z). Our approach to the optimization is based on the theoretical model by Kroll, Morton, and Rosenbluth, whereby the taper profile aw(z) is not a predetermined function (such as linear or exponential) but is determined by the physics of a resonant particle. For further enhancement of the energy extraction efficiency, we propose a modification to the model, which involves manipulations of the resonant particle’s phase. Using the numerical simulation code GENESIS, we apply our model-based optimization methods to a case of the future FEL at the MAX IV Laboratory (Lund, Sweden), as well as a case of the LCLS-II facility (Stanford, USA).
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| 24. |
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| 25. |
- Mak, Alan, et al.
(författare)
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Sensitivity Study of a Tapered Free-Electron Laser
- 2014
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Ingår i: Proceedings of FEL 2014, Basel, Switzerland. - 9783954501335 ; , s. 399-402
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The output power of a free-electron laser (FEL) can be greatly enhanced by tapering the undulator line. In this work, a sensitivity study of a tapered FEL is presented. The study is conducted using the numerical simulation code GENESIS and a taper optimization method. Starting from a possible case for the future X-ray FEL at the MAX IV Laboratory in Lund, Sweden, a number of parameters are varied systematically and the impact on the FEL power is investigated. These parameters include the electron beam's initial energy, current, emittance, energy spread, as well as the seed radiation power.
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| 26. |
- Olsson, David, et al.
(författare)
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Transverse RF Deflecting Structures for the MAX IV LINAC
- 2018
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Ingår i: JACoW Publishing. - 9783954501847 ; , s. 3684-3687
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The MAX IV LINAC operates both as a full-energy injector for two electron storage rings, and as a driver for a Short Pulse Facility (SPF). Recently a conceptual design report for a Soft X-ray Laser (SXL) beamline at the end of the existing LINAC was started. For SPF and SXL operation, it is important to characterize beam parameters such as bunch profile, slice energy spread and slice emittance. For these measurements, two 3 m long transverse deflecting RF structures with a matching section are being developed. The structures are operating at S-band and have variable polarizations. When fed via a SLED pulse compressor, the two structures can generate a total integrated deflecting voltage higher than 100 MV which is sufficient for measurements with temporal resolutions down to 1 fs. This paper describes the initial RF design of the deflecting structures.
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| 27. |
- Pop, Mihai, et al.
(författare)
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Characterization of FEL spectra using specific figures of merit
- 2019
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Ingår i: Proceedings of the 39th International Free-Electron Laser Conference, FEL 2019. - 9783954502103 ; , s. 388-391
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Konferensbidrag (refereegranskat)abstract
- There is an increasing demand from the user community for high quality FEL radiation. The spectrum of this radiation can prove to be a useful tool in characterizing the FEL process. Starting from a tool initially developed at FERMI we extend its capabilities to be able to analyze the modal components of the FEL spectrum. In this paper we will describe and compare two different figures of merit and offer initial bench-marking with respect to classic figure of merit for spectra such as FWHM and RMS.
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| 28. |
- Pop, Mihai, et al.
(författare)
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Considerations on implementing EEHG with a strong linear chirp
- 2019
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Ingår i: Proceedings of the 39th International Free-Electron Laser Conference, FEL 2019. - 9783954502103 ; , s. 262-265
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Konferensbidrag (refereegranskat)abstract
- Due to the stochastic nature of SASE radiation its longitudinal coherence is limited to a small fraction of the electron bunch. By pre-bunching the electrons before entering a radiator, the FEL radiation is ensured to have the same initial phase all through the bunch. Echo enabled harmonic generation (EEHG) is a technique that, by cleverly using two modulators and two dispersive sections, creates microbunches of electrons at a high harmonic of the seed laser used in the modulators. In this paper we will present some of the challenges of using this technique in combination with a strongly chirped beam and indicate a few ways to overcome said challenges.
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| 29. |
- Pop, Mihai, et al.
(författare)
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Mitigation of CSR induced spectral broadening in EEHG FEL
- 2023
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Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 1048
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Tidskriftsartikel (refereegranskat)abstract
- Externally seeded schemes have offered a major leap in improving the longitudinal coherence of FELs in the EUV and soft X-ray range. The Echo Enabled Harmonic Generation (EEHG) technique creates bunching at wavelengths of a few nanometers in two stages of longitudinal phase space manipulation, each consisting of an energy modulator and a chicane. Compared to other seeding techniques, EEHG is less sensitive to electron beam phase space distortions occurring during acceleration and compression. However the strong chicane needed in the first stage makes the system vulnerable to Coherent Synchrotron Radiation (CSR), which imprints a long-wavelength energy modulation on the electron bunch after the EEHG process has been initiated. Coupled with the second dispersive section, this modulation creates a position dependent change in the final bunching wavelength. In this work we show that tailoring the second seed laser wavelength can successfully compensate for the varying energy profile induced by CSR.
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| 30. |
- Pop, Mihai, et al.
(författare)
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On the coherence properties of FEL
- 2017
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Ingår i: IPAC 2017 - Proceedings of the 8th International Particle Accelerator Conference. - 9783954501823 ; , s. 2753-2755
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- FELs are well known for generating highly coherent light with excellent brilliance. In order to improve FEL coherence we have to follow how coherence evolves along the undulator and determine the factors that influence it the most. This paper presents qualitative coherence features that shine new light on the importance of coherence studies in the design of an FEL. By simulating and then analyzing the the FEL light we arrive at results linking coherence to parameters such as undulator polarization or seed laser power density.
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| 31. |
- Pop, Mihai, et al.
(författare)
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Single-shot transverse coherence in seeded and unseeded free-electron lasers: A comparison
- 2022
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Ingår i: Physical Review Accelerators and Beams. - 2469-9888. ; 25:040701
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Tidskriftsartikel (refereegranskat)abstract
- The advent of x-ray free-electron lasers (FELs) drastically enhanced the capabilities of several analytical techniques, for which the degree of transverse (spatial) coherence of the source is essential. FELs can be operated in self-amplified spontaneous emission (SASE) or seeded configurations, which rely on a qualitatively different initialization of the amplification process leading to light emission. The degree of transverse coherence of SASE and seeded FELs has been characterized in the past, both experimentally and theoretically. However, a direct experimental comparison between the two regimes in similar operating conditions is missing, as well as an accurate study of the sensitivity of transverse coherence to key working parameters. In this paper, we carry out such a comparison, focusing in particular on the evolution of coherence during the light amplification process.
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| 32. |
- Qin, Weilun, et al.
(författare)
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The FEL in the SXL project at MAX IV
- 2021
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Ingår i: Journal of Synchrotron Radiation. - : International Union Of Crystallography. - 1600-5775 .- 0909-0495. ; 28, s. 707-717
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Tidskriftsartikel (refereegranskat)abstract
- In this paper the design of the free-electron laser (FEL) in the SXL (Soft X-ray Laser) project at the MAX IV Laboratory is presented. The target performance parameters originate in a science case put forward by Swedish users and the SXL FEL is foreseen to be driven by the existing MAX IV 3 GeV linac. The SXL project is planned to be realized in different stages and in this paper the focus is on Phase 1, where the basic operation mode for the FEL will be SASE (self-amplified spontaneous emission), with an emphasis on short pulses. Simulation results for two linac bunches (high and low charge) with different pulse duration are illustrated, as well as the performance for two-color/two-pulses mode and power enhancement through tapering. Besides standard SASE and optical klystron configurations, the FEL setup is also tailored to allow for advanced seeding schemes operations. Finally possible upgrades that will be implemented in a second phase of the project are discussed.
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| 33. |
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| 34. |
- Thorin, Sara, et al.
(författare)
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Characterisation of the BEAM from thermionic RF-gun adapted for photo cathode operation
- 2009
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Ingår i: ; , s. 310-312
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Konferensbidrag (refereegranskat)abstract
- The existing thermionic RF-gun (tungsten-BaO cathode) at the MAX-lab linac injector has been adapted for photo cathode operation. Important parameters of this system for free electron laser experiments, like emittance and charge, were measured giving 5.5 mmmrad at 70 pC (see below). A more detailed report on that setup, including laser and electron optics is given.
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| 35. |
- Thorin, Sara, et al.
(författare)
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Experience and initial measurements of magnetic linearisation in the MAX IV linac bunch compressors
- 2017
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Ingår i: Proceedings of FEL2017, Santa Fe, NM, USA. - 9783954501793 ; , s. 273-275
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The MAX IV Linac is now in routine operation for injection into two storage rings, and as a high-brightness driver for a Short Pulse Facility (SPF). In short-pulse mode the electron bunch is created in a photo cathode gun and compressed in two double achromat bunch compressors that also linearise longitudinal phase space with the second order transfer matrix element T566. T566 in the compressors canbe tweaked with weak sextupoles located at high dispersion. In this paper we present the current experience from operating the bunch compressors at MAX IV and results from initial measurements of longitudinal phase space using our version of the the zero-crossing method.
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| 36. |
- Thorin, Sara, et al.
(författare)
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Photocathode operation of a thermionic RF gun
- 2009
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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. ; 606:3, s. 291-295
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Tidskriftsartikel (refereegranskat)abstract
- The thermionic RF gun using a BaO cathode at the MAX-lab linac injector has been successfully commissioned for additional operation as a photocathode gun. By retaining the BaO cathode, lowering the temperature below thermal emission and illuminating it with a UV (263 nm) 9 ps laser pulse a reduced emittance and enhanced emission control has been achieved. Measurements show a normalised emittance of 5.5 mm mrad at 200 pC charge and a maximum quantum efficiency of 1.1×10-4. The gun is now routinely switched between storage ring injections in thermionic mode and providing a beam for the MAX-lab test FEL in photocathode mode.
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| 37. |
- Thorin, Sara, et al.
(författare)
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PROGRESS OF THE COMMISSIONING OF THE TEST FEL AT MAX-lab
- 2008
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Ingår i: Proceedings of EPAC08. ; , s. 139-141
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Konferensbidrag (refereegranskat)abstract
- In a collaboration between MAX-lab and BESSY a test facility for Harmonic Generation Free Electron Laser is being constructed at MAX-lab. The setup uses the existing MAX-lab injector together with a Ti:Sa 263 nm laser system, used for both the gun and seeding, and an optical klystron consisting of a modulator, a chicane and a radiator. The different parts of the system have been installed and commissioning started during the fall of 2007. In this paper the progress of the commissioning of the Test FEL and our initial results are presented.
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| 38. |
- Thorin, Sara, et al.
(författare)
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Status of MAX IV linac beam commissioning and performance
- 2017
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Ingår i: IPAC 2017 - Proceedings of the 8th International Particle Accelerator Conference. - 9783954501823 ; , s. 1547-1549
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Konferensbidrag (refereegranskat)abstract
- The MAX IV linac is used both for injection into a 3 GeV storage ring, and as a high brightness driver for a Short Pulse Facility (SPF). It has also been deigned to handle the high demands of an FEL injector. The linac is now routinely injecting into the two storagerings, and commissioning work is focused towards delivering high brightness pulses to the SPF. In this paper we present results from characterisation of the linac in ring injection mode, as well as results from measurements of key parameters for the SPF such as bunch length and emittance.
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| 39. |
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| 40. |
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