Author: Doom, L.
Paper Title Page
WEPGW102 Investigation on Mysterious Long-Term Orbit Drift at NSLS-II 2728
 
  • Y. Hidaka, W.X. Cheng, L. Doom, R.P. Fliller, G. Ganetis, J. Gosman, C. Hetzel, R. A. Hubbard, D. Padrazo Jr, B. Podobedov, J. Rose, T.V. Shaftan, S.K. Sharma, V.V. Smaluk, T. Tanabe, Y. Tian, G.M. Wang, C.H. Yu
    BNL, Upton, Long Island, New York, USA
 
  Funding: The study is supported by U.S. DOE under Contract No. DE-SC0012704.
Over a few months in 2018, we observed occasional episodes of relatively quick accumulation of correction strengths for the fast correctors (used by the fast orbit feedback) near Cell 4 (C04) region at NSLS-II Storage Ring. We immediately started investigating the problem, but the cause remained unclear. However, after coming back from the Fall shutdown, we experienced even faster drifts, at a rate of as much as 10 urad per day in terms of orbit kick angle accumulation. The risk of damage on the ring vacuum chambers by the continuing orbit drift without explanation eventually forced us to take emergency study shifts and temporarily lock out the C04 IVU beamline. After extensive investigation by many subsystem experts in Accelerator Division, ruling out many suspicious sources one by one, we were finally able to conclude the cause to be the localized ground motion induced by large temperature jumps of the utility tunnel right underneath the C04 straight section. We report the details of this incident.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW102  
About • paper received ※ 19 May 2019       paper accepted ※ 20 May 2019       issue date ※ 21 June 2019  
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WEPGW114 Interferometric Measurement of Bunch Length of a 3Mev Picocoulomb Electron Beam 2766
 
  • X. Yang, M. Babzien, B. Bacha, G.L. Carr, W.X. Cheng, L. Doom, M.G. Fedurin, B.N. Kosciuk, J.J. Li, D. Padrazo Jr, T.V. Shaftan, V.V. Smaluk, C. Swinson, L.-H. Yu, Y. Zhu
    BNL, Upton, Long Island, New York, USA
 
  Funding: BNL LDRD
We report the bunch length measurement of low-energy 3 MeV electron beams in picosecond regime with the charge from 1.0 to 14 pC. It is the first time that we demonstrate single-cycle nano-joule coherent terahertz (THz) radiation from 3MeV electron beam can be meas-ured via a far-infrared Michelson interferometer using a QOD. At this low energy range, when charge is about 1 pC, the signal from the conventional helium-cooled sili-con composite bolometer is too low. Compared to the bunch length measurement via the ultrafast-laser-pump and electron-beam-probe in the timescale 10-14 to 10-12 s which is determined by the phase-transition dynamics in solids, the advantages are: there are no needs of pump laser and probe sample, greatly simplifying the experi-ment; the timing jitter between laser and electron beams contributes no error to the bunch length measurement; furthermore, the method can be extended to sub-picosecond regime enabling bunch length measurement in a much broader timescale 10-14 to 10-11 s for low-energy electron beams. In the current experiment the bunch length is limited to 1 ps only because the setup of driving laser to cathode with a large 70° incident angle, effective-ly lengthening the laser pulse to ≥1 ps.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPGW114  
About • paper received ※ 14 May 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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THPMP053 Tuning Quadrupoles for Brighter and Sharper Ultra-fast Electron Diffraction Imaging 3571
 
  • X. Yang, L. Doom, M.G. Fedurin, Y. Hidaka, J.J. Li, D. Padrazo Jr, T.V. Shaftan, V.V. Smaluk, G.M. Wang, L.-H. Yu, Y. Zhu
    BNL, Upton, Long Island, New York, USA
  • W. Wan
    ShanghaiTech University, Shanghai, People’s Republic of China
 
  Funding: BNL LDRD
We report our proof-of-principle design and experi-mental commissioning of broadly tunable and low-cost transverse focusing lens system for MeV-energy electron beams at the ultra-fast electron diffraction (UED) beam-line of the Accelerator Test Facility II of BNL. We exper-imentally demonstrate the independent control over the size and divergence of the electron beam at the sample via tunable quadrupoles. By applying online optimiza-tion, we achieve minimum beam sizes 75 µm from 1 to 13 pC, two orders of magnitude higher charge density than previously achieved using conventional solenoid tech-nique. Finally, we experimentally demonstrate Bragg-diffraction image (BDI) with significant improvement up to 3 times brighter and 2 times sharper BDI peaks via the optimized quadrupoles, improvement larger with higher charge. The result could be crucial for the future single-shot ultra-fast electron microscope development.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPMP053  
About • paper received ※ 14 May 2019       paper accepted ※ 21 May 2019       issue date ※ 21 June 2019  
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