Author: Luo, T.H.
Paper Title Page
TUPAB053 Design Progress of ALS-U 3rd-Harmonic Cavity 1481
 
  • T.H. Luo, K.M. Baptiste, S. De Santis, D. Li, J.W. Staples, M. Venturini
    LBNL, Berkeley, California, USA
  • H.Q. Feng
    TUB, Beijing, People’s Republic of China
  
  Funding: Director, Office of Science, Office of Basic Energy Sciences, and LDRD Program of Lawrence Berkeley National Laboratory, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231
A higher-har­monic rf cav­ity (HHC) sys­tem is re­quired in the ALS-U stor­age ring to lengthen the bunches, re­duce in­tra­beam-scat­ter­ing ef­fects, and im­prove Tou­schek beam life­time. A 3rd har­monic, nor­mal con­duct­ing, pas­sive-cav­ity sys­tem has been cho­sen based on beam-dy­nam­ics re­quire­ments and cost con­sid­er­a­tions. We have ex­plored two op­tions for ALS-U 3HC sys­tem: a high-R/Q re-en­trant cav­ity with wave­guide HOM dampers, and a low-R/Q sys­tem with two el­lip­ti­cal cav­i­ties and HOM beam line ab­sorbers. In this paper, we pre­sent the re­cent progress on the cav­ity de­sign and re­lated beam dy­nam­ics stud­ies. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB053  
About • paper received ※ 19 May 2021       paper accepted ※ 11 June 2021       issue date ※ 14 August 2021  
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WEPAB081 The Broad-Band Impedance Budget in the Storage Ring of the ALS-U Project 2779
 
  • D. Wang, K.L.F. Bane, R. Bereguer, T. Cui, S. De Santis, P. Gach, D. Li, T.H. Luo, T. Miller, T. Oliver, O. Omolayo, C. Steier, T.L. Swain, M. Venturini, G. Wang
    LBNL, Berkeley, California, USA
  
  De­sign work is un­der­way for the up­grade of the Ad­vanced Light Source (ALS-U) to a dif­frac­tion-lim­ited soft x-rays ra­di­a­tion source. Like other 4th-gen­er­a­tion light source ma­chines, the ALS-U mul­ti­ple-bend achro­mat stor­age-ring (SR) is po­ten­tially sen­si­tive to beam-cou­pling im­ped­ance ef­fects. This paper pre­sents the SR broad-band im­ped­ance bud­get in both the lon­gi­tu­di­nal and trans­verse planes. In our mod­el­ing we fol­low the com­monly ac­cepted ap­proach of sep­a­rat­ing the re­sis­tive-wall and the geo­met­ric parts of the im­ped­ance, the for­mer being de­scribed by an­a­lyt­i­cal for­mu­las and the lat­ter ob­tained by nu­mer­i­cal elec­tro­mag­netic codes (pri­mar­ily CST Stu­dio soft­ware) as­sum­ing per­fectly con­duct­ing ma­te­ri­als. We dis­cuss the main sources of im­ped­ance. Re­sults of our analy­sis are the basis for the sin­gle bunch in­sta­bil­ity study and would feed­back on the de­sign of crit­i­cal vac­uum com­po­nents.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB081  
About • paper received ※ 20 May 2021       paper accepted ※ 01 July 2021       issue date ※ 20 August 2021  
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WEPAB082 Single Bunch Instability Simulations in the Storage Ring of the ALS-U Project 2783
 
  • D. Wang, K.L.F. Bane, S. De Santis, M.P. Ehrlichman, D. Li, T.H. Luo, O. Omolayo, G. Penn, C. Steier, M. Venturini
    LBNL, Berkeley, California, USA
  
  As the broad-band im­ped­ance mod­el­ing and the vac­uum cham­ber de­sign of the new Ad­vanced Light Source stor­age ring (ALS- U) reach ma­tu­rity, we re­port on progress in sin­gle-bunch col­lec­tive ef­fects stud­ies. A pseudo-Green func­tion wake rep­re­sent­ing the en­tire ring was ear­lier ob­tained by nu­mer­i­cal and an­a­lyt­i­cal meth­ods. Macropar­ti­cle sim­u­la­tions using the com­puter code "el­e­gant" and this wake func­tion are used to de­ter­mine the in­sta­bil­ity thresh­olds for lon­gi­tu­di­nal and trans­verse mo­tion. We con­sider var­i­ous op­er­at­ing con­di­tions, such as with­out/with higher-har­monic RF cav­i­ties, zero/fi­nite lin­ear chro­matic­ity, and with­out/with a trans­verse bunch-by-bunch feed­back sys­tem. Re­sults show enough mar­gin for the broad­band im­ped­ance bud­get when the sin­gle-bunch in­sta­bil­ity thresh­olds are com­pared with the de­sign bunch charge.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB082  
About • paper received ※ 20 May 2021       paper accepted ※ 01 July 2021       issue date ※ 12 August 2021  
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