Author: Nomura, M.
Paper Title Page
TUPAB201 Vacuum Tube Operation Tuning for a High Intensity Beam Acceleration in J-PARC RCS 1884
 
  • M. Yamamoto, M. Nomura, H. Okita, T. Shimada, F. Tamura
    JAEA/J-PARC, Tokai-mura, Japan
  • M. Furusawa, K. Hara, K. Hasegawa, C. Ohmori, Y. Sugiyama, M. Yoshii
    KEK, Tokai, Ibaraki, Japan
 
  Tetrode vac­uum tubes in the J-PARC RCS are used under a re­duced fil­a­ment volt­age con­di­tion com­pared with the rat­ing value to pro­long the tube life time. One tube reached the end of life in 2020; it was the first case in the RCS after 60,000 hours op­er­a­tion time. This means the re­duced fil­a­ment volt­age works well be­cause the tube has been run­ning be­yond an ex­pected life time sug­gested by the tube man­u­fac­turer. How­ever, an elec­tron emis­sion from the fil­a­ment is de­creased by the re­duced fil­a­ment volt­age. Al­though the large am­pli­tude of the anode cur­rent is nec­es­sary for the high in­ten­sity beam ac­cel­er­a­tion to com­pen­sate an wake volt­age, a solid-state am­pli­fier to drive a con­trol grid cir­cuit al­most reaches the out­put power limit be­cause of the poor elec­tron emis­sion. We changed the fil­a­ment volt­age re­duc­tion rate from 15 % to 5 %; the re­quired power of the solid-state am­pli­fier was fairly re­duced, whereas the ac­cel­er­ated beam power was same. We will de­scribe the mea­sure­ment re­sults of the vac­uum tube pa­ra­me­ters in terms of the fil­a­ment volt­age tun­ing.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB201  
About • paper received ※ 17 May 2021       paper accepted ※ 17 June 2021       issue date ※ 02 September 2021  
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WEPAB177 Consideration of Triple-Harmonic Operation for the J-PARC RCS 3020
 
  • H. Okita
    JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
  • M. Furusawa, Y. Sugiyama
    KEK, Tokai, Ibaraki, Japan
  • K. Hara, K. Hasegawa, M. Nomura, C. Ohmori, T. Shimada, F. Tamura, M. Yamamoto, M. Yoshii
    KEK/JAEA, Ibaraki-Ken, Japan
 
  The wide­band mag­netic alloy (MA) cav­i­ties are em­ployed in the J-PARC RCS. The dual-har­monic op­er­a­tion, in which each MA cav­ity is dri­ven by su­per­po­si­tion of the fun­da­men­tal ac­cel­er­at­ing volt­age and the sec­ond har­monic volt­age, sig­nif­i­cantly im­proves the bunch­ing fac­tor and is in­dis­pens­able for ac­cel­er­a­tion of the high in­ten­sity beams. The orig­i­nal LLRF con­trol sys­tem was re­placed with the new sys­tem in 2019, which can con­trol the am­pli­tudes of the higher har­mon­ics as well as the fun­da­men­tal and sec­ond har­mon­ics. There­fore we con­sider to use ad­di­tion­ally the third har­monic volt­age for fur­ther im­prove­ment of the bunch­ing fac­tor dur­ing ac­cel­er­a­tion. By the triple-har­monic op­er­a­tion, the flat RF bucket can be re­al­ized with a higher syn­chro­nous phase and im­prove­ment of the bunch­ing fac­tor is ex­pected. In this pre­sen­ta­tion, we de­scribe the lon­gi­tu­di­nal sim­u­la­tion stud­ies of the triple-har­monic op­er­a­tion. Also the pre­lim­i­nary test re­sults are pre­sented.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB177  
About • paper received ※ 18 May 2021       paper accepted ※ 25 June 2021       issue date ※ 19 August 2021  
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