Author: Wei, J.H.
Paper Title Page
MOPB09 Comparison Among Different Tune Measurement Schemes at HLS-II Storage Ring 93
 
  • L.T. Huang, X.Y. Liu, P. Lu, M.-X. Qian, B.G. Sun, J.G. Wang, J.H. Wei, F.F. Wu, Y.L. Yang, T.Y. Zhou
    USTC/NSRL, Hefei, Anhui, People's Republic of China
 
  Tune measurement is one of the most significant beam diagnostics at HLS-II storage ring. When measuring tune, higher tune spectral component and lower other compo-nents are expected, so that the tune measurement will be more accurate. To this end, a set of BBQ (Base Band Tune) front-end based on 3D (Direct Diode Detection) technique has previously developed to improve the effec-tive signal content and suppress other components. Em-ploying the BBQ front-end, four different tune measure-ment schemes are designed and related experiments per-formed on the HLS-II storage ring. Experimental results and analysis will be presented later.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-MOPB09  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUPB07 Stability Study of Beam Position Measurement Based on Higher Order Mode Signals at FLASH 273
 
  • J.H. Wei
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  • N. Baboi
    DESY, Hamburg, Germany
  • L. Shi
    PSI, Villigen PSI, Switzerland
 
  FLASH is a free-electron laser driven by a supercon-ducting linac at DESY in Hamburg. It generates high-brilliance XUV and soft X-ray pulses by SASE (Self Amplified Spontaneous Emission). Many accelerating cavities are equipped with HOMBPMs (Higher Order Mode based Beam Position Monitors) to align the beam and monitor the transverse beam position. However, these lose their position prediction ability over time. In this paper, we applied an efficient measurement and signal analysis with various data process methods including PLS (Partial Least Square) and SVD (Singular Value Decomposition) to determine the transverse beam position. By fitting the HOM signals with a genetic algorithm, we implemented a new HOMBPM calibration procedure and obtained reliable beam prediction positions over a long time. A stable RMS error of about 0.2 mm by using the spectra of signals and 0.15 mm by using the new method over two months has been observed.  
poster icon Poster TUPB07 [1.816 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-TUPB07  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUPC12 Beam Transverse Quadrupole Oscillation Measurement in the Injection Stage for the HLS-II Storage Ring 325
 
  • F.F. Wu, F.L. Gao, L.T. Huang, X.Y. Liu, P. Lu, B.G. Sun, J.G. Wang, J.H. Wei, T.Y. Zhou
    USTC/NSRL, Hefei, Anhui, People's Republic of China
 
  Funding: Supported by the National Science Foundation of China (Grant No. 11705203, 11575181, 11605202) and the National Key Research and Development Program of China(No. 2016YFA0402000)
Beam transverse quadrupole oscillation can be excited in the injection stage if injected beam parameters(twiss parameters or dispersion) are not matched with the parameters in the injection point of the storage ring. In order to measure the beam transverse quadrupole oscillation in the injection stage for the HLS-II storage ring, some axially symmetric stripline BPMs were designed. Transverse quadrupole component for these BPMs was simulated and off-line calibrated. Beam transverse quadrupole oscillation has been measured when beam was injected into the HLS-II electron storage ring. The spectrum of the transverse quadrupole component showed that beam transverse quadrupole oscillation is very obvious in the injection stage and this oscillation isn't the second harmonic of beam betatron oscillation. The relationship between transverse quadrupole oscillation and beam current was also analyzed and the result shows that the relationship is not linear.
 
poster icon Poster TUPC12 [0.467 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-TUPC12  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPA09 Long Term Beam Phase Monitoring Based on HOM Signals in SC Cavities at FLASH 388
 
  • J.H. Wei
    USTC/NSRL, Hefei, Anhui, People's Republic of China
  • N. Baboi
    DESY, Hamburg, Germany
  • L. Shi
    PSI, Villigen PSI, Switzerland
 
  The accelerating RF fields in superconducting cavities must be controlled precisely in FEL (Free Electron Laser) facilities to avoid beam energy spread and arrival time jitter. Otherwise the beam quality is degraded. The LLRF (Low Level Radio Frequency) system controls the RF field and provides a highly stable RF reference. A new type of beam phase determination technique based on beam-excited HOMs (Higher Order Modes) in cavities has been implemented. The two special couplers installed at both ends of each cavity, pick up the signals containing both the leakage of the accelerating field and the HOM signals. Therefore the signals can be used to calculate the beam phase directly with respect to the RF phase. We analysed the factors which may affect the result of the beam phase on a long-term based on an experimental platform at FLASH. Some phase drifts between the HOM-BPhM (Beam Phase Monitor) and the LLRF system phase measurement were observed and the reason will be further studied.  
poster icon Poster WEPA09 [1.720 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2018-WEPA09  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)