Keyword: HOM
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MOPP010 Design and Properties of a New DCCT Chamber for the PF-Ring at KEK simulation, impedance, operation, cavity 91
 
  • R. Takai, T. Honda, T. Nogami, T. Obina, Y. Tanimoto
    KEK, Ibaraki, Japan
  
  A DC current transformer (DCCT) for the PF-ring was renewed during the 2018 summer shutdown. A vacuum chamber for the new DCCT was designed based on a circular duct with an inner diameter of 100 mm and has a structure housing a toroidal core inside of electromagnetic shields. The geometry of the ceramic break for interrupting the wall current flow was optimized using a three-dimensional electromagnetic field simulator, and the break was fabricated considering some technical limitations. Both ends of the ceramic break were short-circuited in a high-frequency manner by a sheet-like capacitive structure to suppress the radiation of unneeded higher-order modes (HOMs) into the core housing. The ceramic break is also equipped with water-cooling pipes on metal sleeves brazed to the both ends to efficiently remove the heat generated by HOMs. The new DCCT chamber has been used already in user operation without any problems. A temperature rise near the ceramic break is still approximately six degrees Celsius, even when a 50-mA isolated bunch is stored.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2019-MOPP010  
About • paper received ※ 04 September 2019       paper accepted ※ 07 September 2019       issue date ※ 10 November 2019  
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TUPP032 J-PARC Test of ESS Beam on Target Diagnostics Prototypes Aperture Monitor and GRID target, electron, proton, monitoring 387
 
  • C.A. Thomas, J. Etxeberria, H. Kocevar, J.P.S. Martins, T.J. Shea
    ESS, Lund, Sweden
  • A.J. Johansson, M. Törmänen
    Lund University, Lund, Sweden
  • S.I. Meigo, M. Ooi
    JAEA/J-PARC, Tokai-mura, Japan
  • H. Niu, B. Zhang
    IMP/CAS, Lanzhou, People’s Republic of China
  
  The ESS high power beam will be delivered to the spallation target with high degree of control. To this end, we have designed a suite of instruments which provide measurement of the beam characteristics in a drift space a few meters from the target. Two of these instruments, the APTerure Monitor (APTM) and the GRID are presented. The APTM is designed to measure the fraction of beam going through the defined aperture; its time acquisition ranges from intra-pulse at µs sampling rate to many pulses over seconds. The GRID measures the projected horizontal and vertical profiles, sampling the pulse at 1MHz. A prototype of these two instruments has been designed and installed in the 3NBT dump line of J-PARC. They are designed to test functionality of these instruments in a similar environment as ESS. The 3NBT Dump line at J-PARC presents such an environment. In the second part of the paper we report the results and the measurements performed to test the prototypes. Before concluding we will discuss the results and propose improvements to the instruments final design.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2019-TUPP032  
About • paper received ※ 04 September 2019       paper accepted ※ 10 September 2019       issue date ※ 10 November 2019  
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TUPP041 Observations of Long-Range and Short-Range Wakefield Effects on Electron-Beam Dynamics in TESLA-type Superconducting RF Cavities cavity, wakefield, FEL, detector 428
 
  • A.H. Lumpkin, N. Eddy, D.R. Edstrom, J. Ruan, R.M. Thurman-Keup
    Fermilab, Batavia, Illinois, USA
  
  Funding: This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics.
The Fermilab Accelerator Science and Technology (FAST) facility has a unique configuration of a photocathode rf gun beam injecting two TESLA-type single cavities (CC1 and CC2) in series prior to the cryomodule. Beam propagation off axis in these cavities can result in both long-range and short-range transverse wakefields which can lead to emittance dilution within the macropulses and micropulses, respectively. Two configurations of a Hamamatsu C5680 streak camera viewing a downstream OTR screen were utilized to track centroid shifts during the macropulse (framing mode) for the long-range case and during the micropulse for the short-range case (~10-micron spatial resolution and 2-ps temporal resolution). Steering off axis before CC1, resulted in a 100-kHz bunch centroid oscillation within the macropulse that was detected by the downstream rf BPMs and the streak camera*. At 500 pC/b, 50b, and 4-mrad off-axis vertical steering into CC2, we observed an ~ 100-micron head-tail centroid shift in the streak camera image y(t) profiles which we attributed to a short-range wakefield effect. Additional results for kick-angle compensations and model results will be presented.
*A.H. Lumpkin et al., Phys. Rev. Accel. and Beams 21,064401 (2018). 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IBIC2019-TUPP041  
About • paper received ※ 10 September 2019       paper accepted ※ 11 September 2019       issue date ※ 10 November 2019  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)