MC2: Photon Sources and Electron Accelerators
A05 Synchrotron Radiation Facilities
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MOVIR06 Preliminary Sirius Commissioning Results 11
  • L. Liu, M.B. Alves, F.C. Arroyo, J.F. Citadini, R.H.A. Farias, J.G.R.S. Franco, R. Junqueira Leão, S.R. Marques, R.T. Neuenschwander, A.C.S. Oliveira, X.R. Resende, A.R.D. Rodrigues, C. Rodrigues, F. Rodrigues, R.M. Seraphim, F.H. de Sá
    LNLS, Campinas, Brazil
  Sirius is a 4th generation 3 GeV low emittance electron storage ring that is in final commissioning phase at the Brazilian Centre for Research in Energy and Materials (CNPEM) campus in Campinas, Brazil. Presently (April 2020) we have accumulated 15 mA of current, limited by vacuum, using a nonlinear kicker for injection. In this paper we report on the Sirius main commissioning results and main subsystems issues during installation and commissioning.  
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DOI • reference for this paper ※  
About • paper received ※ 01 June 2020       paper accepted ※ 11 June 2020       issue date ※ 01 September 2020  
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First Experimental Demonstration of the Mechanism of Steady-state Microbunching  
  • C.-X. Tang, X.J. Deng, W.-H. Huang, L.X. Yan
    TUB, Beijing, People’s Republic of China
  • A. Chao
    SLAC, Menlo Park, California, USA
  • J. Feikes, J. Li, A.N. Matveenko, Y. Petenev, M. Ries
    HZB, Berlin, Germany
  • A. Hoehl, R. Klein
    PTB, Berlin, Germany
  The concept of steady-state microbunching (SSMB) in electron storage rings implies a longitudinal bunch structure given by an optical or ultraviolet wavelength rather than a conventional radio frequency wavelength, typically six or more orders of magnitude smaller. The strong coherent radiation from the steady-state microbunches will support a facility with high-power, high-repetition-rate or continuous-wave, narrow-band, and short-wavelength radiation, which can provide unprecedented new possibilities for accelerator photon science and industry applications. It has been proved that the electron beam energy modulation induced by an externally applied 1064 nm laser in an undulator can yield microbunching and coherent radiation one turn later at exactly the same place where the modulation was applied. The results confirm that the phase of an electron beam relative to a laser in a storage ring can be locked turn-by-turn in a sub-laser-wavelength precision, therefore making SSMB possible. This validation represents the first key advance in the development of an SSMB high-power light source.
Phys. Rev. Lett. 105, 154801 (2010)
The SSMB collaboration: [FLS2018-THP2WB02]
X. Deng, et al. First Experimental Demonstration of the Mechanism of Steady-state Microbunching, under review.
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Applying Machine Learning to Stabilize the Source Size in the ALS Storage Ring  
  • S.C. Leemann, W.E. Byrne, D.P. Cuneo, M.P. Ehrlichman, T. Hellert, A. Hexemer, Y. Lu, M. Marcus, C.N. Melton, H. Nishimura, G. Penn, F. Sannibale, D.A. Shapiro, C. Sun, D. Ushizima, M. Venturini, E.J. Wallén
    LBNL, Berkeley, USA
  Funding: This research is funded by the US Department of Energy (BES & ASCR Programs) and supported by the Director of the Office of Science of the US Department of Energy under Contract No. DEAC02-05CH11231.
In state-of-the-art synchrotron light sources the overall source stability is presently limited by the achievable level of electron beam size stability. This source size stability is presently on the few-percent level, which is still 1–2 orders of magnitude larger than already demonstrated stability of source position/angle (slow/fast orbit feedbacks) and current (top-off injection). Until now source size stabilization has been achieved through corrections based on a combination of static predetermined physics models and lengthy calibration measurements (feed-forward tables), periodically repeated to counteract drift in the accelerator and instrumentation. We now demonstrate for the first time* how application of machine learning allows for a physics- and model-independent stabilization of source size relying only on previously existing instrumentation in ALS. Such feed-forward correction based on neural networks that can be continuously online-retrained achieves source size stability as low as 0.2 microns rms (0.4%) which results in overall source stability approaching the sub-percent noise floor of the most sensitive experiments.
*Phys. Rev. Lett. 123, 194801 (2019)
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Alternating the Helicity of X-Ray Photons from an Undulator at Unprecedented Speed  
  • K. Holldack, F. Armborst, J. Bahrdt, W. Frentrup, P. Goslawski, N. Pontius, M. Ries, A. Schälicke, M. Scheer, Ch. Schüssler-Langeheine
    HZB, Berlin, Germany
  X-ray circular dichroism (XMCD), one of the main tools of modern X-ray physics for studying magnetism, benefits enormously from the capability of a fast alterable helicity of circularly polarized X-ray photons. Here we present a novel method, which allows boosting the alternating frequency between right- and left-handed photons to the MHz regime, more than three orders of magnitude faster than present state-of-the-art technologies. The method is based on a twin elliptical undulator installed in a low emittance electron storage ring being operated in a novel mode. Here, the electron optics is tuned close to a resonance where the electron bunches are spatially separated in so-called transverse resonance island buckets (TRIBs). Propagating through the magnetic structures of the twin undulator, electrons from different islands emit photons of the same wavelength but of opposite helicity. Radiation from these two helicity components can be alternated as fast as 2 ns, given by the radio frequency of the accelerator cavity. In the present proof-of-principle experiment at BESSY II we demonstrate a XMCD measurement at the L2,3 absorption edges of a Ni sample with an 800 ns helicity flip.  
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Present Status of Siam Photon Source  
  • P. Sudmuang, S. Boonsuya, T. Chanwattana, Ch. Dhammatong, P. Klysubun, A. Kwankasem, C.P. Preecha, T. Pulampong, V. Sooksrimuang, P. Sunwong, N. Suradet
    SLRI, Nakhon Ratchasima, Thailand
  The 1.2 GeV Siam Photon Source (SPS) has been delivering synchrotron radiation for both academic and industrial community in Thailand. Improvement of the SPS has been significantly archived in the past few years. The booster synchrotron and transfer-line have been successfully upgraded to 1.2 GeV in 2018, which is required for full energy injection. To accommodate more users from ASEAN countries, an additional insertion device namely a 3.5 T superconducting multipole wiggler has been installed and operated in 2018. Coupling correction scheme has been improved after modification of sextupole magnets with additional skew quadrupole coils. Longitudinal instability is also investigated by using streak camera.  
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