Author: Shishlo, A.P.
Paper Title Page
MOPAB203 Benchmark of Superconducting Cavity Models at SNS Linac 671
 
  • A.P. Shishlo
    ORNL, Oak Ridge, Tennessee, USA
  
  Funding: This manuscript has been authored by UT-Battelle, LLC, under Contract No. DE-AC0500OR22725 with the U.S. Department of Energy.
A bench­mark of su­per­con­duct­ing cav­ity mod­els against Time-of-Flight mea­sure­ments at the SNS linac is pre­sented. The su­per­con­duct­ing part of SNS linac (SCL) in­cludes 81 RF cav­i­ties that ac­cel­er­ates H− beam from 185.6 MeV to the final en­ergy of 1 GeV. Dur­ing the op­er­a­tion some of cav­i­ties can be­come un­sta­ble, and its am­pli­tudes should be re­duced, or they should be com­pletely switched off. In this case, the SCL is re­tuned by using a linac sim­u­la­tion code. This sim­u­la­tion tool relay on an ac­cu­racy of the su­per­con­duct­ing cav­ity model. This paper de­scribes the com­par­i­son of the mea­sured beam ac­cel­er­a­tion by one of the SCL cav­i­ties and sim­u­la­tions of this process. Dif­fer­ent cav­ity mod­els are used in sim­u­la­tions. The sub­ject of this study is lim­ited to the lon­gi­tu­di­nal beam dy­nam­ics, so no ef­fects on trans­verse beam char­ac­ter­is­tics have been con­sid­ered. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB203  
About • paper received ※ 14 May 2021       paper accepted ※ 20 May 2021       issue date ※ 24 August 2021  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
MOPAB326 Maximum Entropy Reconstruction of 4D Transverse Phase Space from 2D Projections: with Application to Laser Wire Measurements in the SNS HEBT 1008
 
  • C.Y. Wong, A.P. Shishlo
    ORNL, Oak Ridge, Tennessee, USA
  
  We em­ploy the prin­ci­ple of max­i­mum en­tropy (MENT) to re­con­struct 4D trans­verse phase space from its 2D pro­jec­tions. Emit­tance de­vices com­monly mea­sure two spe­cific 2D pro­jec­tions, i.e. the hor­i­zon­tal and ver­ti­cal phase space dis­tri­b­u­tions. We show that: 1) given only these two 2D pro­jec­tions, their prod­uct is the an­a­lytic MENT so­lu­tion to the 4D dis­tri­b­u­tion; and 2) ad­di­tional 2D pro­jec­tions pro­vide in­for­ma­tion on in­ter-plane cou­pling in the MENT re­con­struc­tion of the 4D phase space which can be solved nu­mer­i­cally. At the Spal­la­tion Neu­tron Source (SNS), laser wires in the high en­ergy beam trans­port (HEBT) en­able non-in­va­sive two-slit type trans­verse phase space mea­sure­ments. Laser wires play the role of the first slit whereas phys­i­cal wires down­stream of a drift act as the sec­ond slit. We re­con­struct the 4D phase space in the HEBT using all four hor­i­zon­tal/ver­ti­cal per­mu­ta­tions of the two slits where: 1) the two con­fig­u­ra­tions with par­al­lel slits con­sti­tute or­di­nary 2D phase space mea­sure­ments in ei­ther plane; and 2) the two con­fig­u­ra­tions with per­pen­dic­u­lar slits carry cou­pling in­for­ma­tion.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB326  
About • paper received ※ 20 May 2021       paper accepted ※ 19 July 2021       issue date ※ 17 August 2021  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
TUPAB329 Pattern Based Parameter Setup of the SNS Linac 2276
 
  • C.C. Peters
    ORNL RAD, Oak Ridge, Tennessee, USA
  • A.P. Shishlo
    ORNL, Oak Ridge, Tennessee, USA
  
  Funding: ORNL is managed by UT-Battelle, LLC, under contract DE-AC05- 00OR22725 for the U.S. Department of Energy.
The­o­ret­i­cal and prac­ti­cal as­pects of beam tun­ing pro­ce­dures used for the SNS linac are dis­cussed. The SNS linac in­cludes two sec­tions of beam ac­cel­er­a­tion. Ac­cel­er­a­tion in the first sec­tion up to 185.5 MeV is done with a room tem­per­a­ture cop­per linac which con­sists of both Drift Tube Linac (DTL) and Cou­pled Cav­ity Linac (CCL) Radio Fre­quency (RF) cav­i­ties. The sec­ond sec­tion con­sists of 81 Su­per­con­duct­ing RF (SRF) cav­i­ties which ac­cel­er­ate the beam to the final beam en­ergy of 1 GeV. The linac is cur­rently ca­pa­ble of de­liv­er­ing an av­er­age beam power out­put of 1.44 MW with typ­i­cal yearly op­er­at­ing hours of around 4500 hours. Due to the high power out­put and high avail­abil­ity of the linac, ac­ti­va­tion of ac­cel­er­a­tor equip­ment is a sig­nif­i­cant con­cern. The linac tun­ing process con­sists of three stages: model based setup of am­pli­tudes and phases of the RF cav­i­ties, em­pir­i­cal beam loss re­duc­tion, and then doc­u­men­ta­tion of the final am­pli­tudes and phases of RF cav­i­ties after the em­pir­i­cal tun­ing. The final step is needed to en­sure fast re­cov­ery from an SRF cav­ity fail­ure. This paper dis­cusses mod­els, al­go­rithms, di­ag­nos­tic tools, soft­ware, and prac­tices that are used for these stages. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-TUPAB329  
About • paper received ※ 22 May 2021       paper accepted ※ 28 May 2021       issue date ※ 25 August 2021  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
WEPAB319 Open XAL Status Report 2021 3421
 
  • N. Milas, J.F. Esteban Müller, E. Laface, Y. Levinsen
    ESS, Lund, Sweden
  • T.V. Gorlov, A.P. Shishlo, A.P. Zhukov
    ORNL, Oak Ridge, Tennessee, USA
  
  The Open XAL ac­cel­er­a­tor physics soft­ware plat­form is being de­vel­oped through in­ter­na­tional col­lab­o­ra­tion among sev­eral fa­cil­i­ties since 2010. The goal of the col­lab­o­ra­tion is to es­tab­lish Open XAL as a multi-pur­pose soft­ware plat­form sup­port­ing a broad range of tool and ap­pli­ca­tion de­vel­op­ment in ac­cel­er­a­tor physics and high-level con­trol (Open XAL also ships with a suite of gen­eral-pur­pose ac­cel­er­a­tor ap­pli­ca­tions). This paper dis­cusses progress in beam dy­nam­ics sim­u­la­tion, new RF mod­els, and up­dated ap­pli­ca­tion frame­work along with new generic ac­cel­er­a­tor physics ap­pli­ca­tions. We pre­sent the cur­rent sta­tus of the pro­ject, a roadmap for con­tin­ued de­vel­op­ment, and an overview of the pro­ject sta­tus at each par­tic­i­pat­ing fa­cil­ity.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB319  
About • paper received ※ 19 May 2021       paper accepted ※ 21 July 2021       issue date ※ 11 August 2021  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)  
 
THXA01 Beyond RMS: Understanding the Evolution of Beam Distributions in High Intensity Linacs 3681
 
  • K.J. Ruisard, A.V. Aleksandrov, S.M. Cousineau, A.P. Shishlo, A.P. Zhukov
    ORNL, Oak Ridge, Tennessee, USA
  
  Funding: This work has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy.
Un­der­stand­ing the evo­lu­tion of beams with space charge is cru­cial to de­sign and op­er­a­tion of high in­ten­sity linacs. While the com­mu­nity holds a broad un­der­stand­ing of the mech­a­nisms lead­ing to emit­tance growth and halo for­ma­tion, there is out­stand­ing dis­crep­ancy be­tween mea­sure­ments and beam evo­lu­tion mod­els that pre­cludes pre­dic­tion of halo losses. This may be due in part to in­suf­fi­cient in­for­ma­tion of the ini­tial beam dis­tri­b­u­tion. This talk will de­scribe work at the SNS Beam Test Fa­cil­ity to di­rectly mea­sure the 6D beam dis­tri­b­u­tion. Full-and-di­rect 6D mea­sure­ment has re­vealed hid­den but phys­i­cally sig­nif­i­cant de­pen­dence be­tween the lon­gi­tu­di­nal dis­tri­b­u­tion and trans­verse co­or­di­nates. This non­lin­ear cor­re­la­tion is dri­ven by space charge and re­pro­duced by self-con­sis­tent sim­u­la­tion of the RFQ. Omis­sion of this in­ter­plane cor­re­la­tion, com­mon when bunches are re­con­structed from lower-di­men­sional mea­sure­ments, de­grades down­stream pre­dic­tions. This talk will also de­scribe the novel di­ag­nos­tics sup­port­ing this work. This in­cludes on­go­ing im­prove­ments to ef­fi­ciency of the 6D phase space mea­sure­ment as well as re­cent achieve­ment of six or­ders of dy­namic range in 2D phase space. 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THXA01  
About • paper received ※ 20 May 2021       paper accepted ※ 23 July 2021       issue date ※ 17 August 2021  
Export • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)