Author: Cheng, W.X.
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MOPMR057 Measurements using Button BPM SUM Signal 377
  • W.X. Cheng, K. Ha, J. Mead, O. Singh, G.M. Wang
    BNL, Upton, Long Island, New York, USA
  Modern digital BPM detectors measure not only the beam positions, four buttons SUM signal can be very helpful for machine developments and operations. At NSLS-II, BPM SUM signal has been used from commissioning stage, to investigate localized beam losses. During top-off operation, precise beam lifetime measurement within relative short period of time becomes important. With many BPMs along the ring, BPM SUM can be a much more accurate tool to measure the beam current and lifetime. BPM SUM signal shall be proportional to beam current, and it may depends on button sizes and BPM chamber geometry, cable attenuations, electronics attenuations, beam position, bunch lengths, fill pattern etc. Experience of BPM SUM signals measurements will be presented.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMR057  
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MOPMR058 Precise Beam Orbit Response Measurement with AC Excitation 380
  • W.X. Cheng, K. Ha, Y. Tian, L.-H. Yu
    BNL, Upton, Long Island, New York, USA
  Fast correctors at NSLS-II storage ring has broad frequency response (~1kHz bandwidth), together with high accurate BPM 10kHz data makes the broadband fast orbit feedback realistic. With integrated NCO, beam orbit response can be precisely measured while driving the electron beam with AC current. Compared to the normal DC orbit response measurement, this method eliminates the measurement errors due to orbit drift. Accurately measured orbit response matrix can be used to characterize the machine lattice. Fast corrector frequency responses have been measured using the same method, by scanning the excitation frequency. This information can be used to optimize the fast orbit feedback control loop.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMR058  
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TUPOR033 Experimental Study of Single Bunch Instabilities at NSLS-II Storage Ring 1738
  • W.X. Cheng, B. Bacha, G. Bassi, A. Blednykh, B. Podobedov, O. Singh, V. Smalyuk
    BNL, Upton, New York, USA
  Single bunch instabilities have been observed since the early stage of NSLS-II storage ring commissioning. After installing the super-conducting cavity, the single bunch instability threshold current was similar at 0.7mA. The instability was eventually determined to be due to transverse mode coupling. Microwave instability has been characterized using streak camera bunch profile, horizontal beam sizes at dispersion location and beam spectrums. Microwave instability threshold current dependency on bunch lengths and IUV gaps has been studied. Most recent experimental results will be presented in this paper.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOR033  
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WEOBB01 Single Micron Single-Bunch Turn-by-Turn BPM Resolution Achieved at NSLS-II 2095
  • B. Podobedov, W.X. Cheng, K. Ha, Y. Hidaka, J. Mead, O. Singh, K. Vetter
    BNL, Upton, Long Island, New York, USA
  NSLS-II state-of-the-art BPMs provide a single micron turn-by-turn BPM resolution for any bunch train of reasonable intensity. For certain beam dynamics studies a similar, or even better, resolution is desired for a single-, or a few-bunch fill, which is not yet available with our standard BPM signal processing. This paper describes our experience with more advanced BPM ADC signal processing which allowed us to significantly improve turn-by-turn BPM resolution in single bunch mode down to the level of about one micron at ~1 nC/bunch. We also present the examples of machine studies that benefit from this BPM performance enhancement.  
slides icon Slides WEOBB01 [2.565 MB]  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEOBB01  
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THPOY048 NSLS-II Active Interlock System and Post-Mortem Architecture 4214
  • K. Ha, E.B. Blum, W.X. Cheng, J. Choi, Y. Hu, D. Padrazo, S. Seletskiy, O. Singh, R.M. Smith, J. Tagger, Y. Tian, G. Wang, T. Yang
    BNL, Upton, Long Island, New York, USA
  The NSLS-II at Brookhaven National Laboratory (BNL) started the user beam service in early 2015, and is currently operating 13 of the insertion device (ID) and beamlines as well as constructing new beamlines. The fast machine protection consists of an active interlock system (AIS), beam position monitor (BPM), cell controller (CCs) and front-end (FE) systems. The AIS measures the electron beam envelop and the dumps the beam by turning off RF system, and then the diagnostic system provides the post-mortem data for an analysis of which system caused the beam dump and the machine status analysis. NSLS-II post-mortem system involves AIS, CCs, BPMs, radio frequency system (RFs), power supply systems (PSs) as well as the timing system. This paper describes the AIS architecture and PM performance for NSLS-II safe operations.  
DOI • reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOY048  
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