Author: Belhaj, M.B.
Paper Title Page
WEPAB381 Multipactor Simulations for MYRRHA Spoke Cavity: Comparison Between SPARK3D, MUSICC3D, CST PIC and Measurement 3606
 
  • N. Hu, M. Chabot, J.-L. Coacolo, D. Longuevergne, G. Olry
    Université Paris-Saclay, CNRS/IN2P3, IJCLab, Orsay, France
  • M.B. Belhaj
    ONERA, Toulouse, France
  
  The mul­ti­pactor ef­fect can lead to ther­mal break­down (quench), high field emis­sion and lim­ited ac­cel­er­at­ing gra­di­ent in su­per­con­duct­ing ac­cel­er­a­tor de­vices. To de­ter­mine the mul­ti­pactor break­down power level, mul­ti­pactor sim­u­la­tions can be per­formed. The ob­jec­tive of this study is to com­pare the re­sults given by dif­fer­ent sim­u­la­tion codes with the re­sults of ver­ti­cal test­ing of SRF cav­i­ties. In this paper, Spark3D, MU­S­IC­C3D and CST Stu­dio PIC solver have been used to sim­u­late the mul­ti­pactor ef­fect in Spoke cav­ity de­vel­oped within the frame­work of MYRRHA pro­ject. Then, a bench­mark of these three sim­u­la­tion codes has been made. The break­down power level, the mul­ti­pactor order and the most promi­nent lo­ca­tion of mul­ti­pactor are pre­sented. Fi­nally, the sim­u­la­tion re­sults are com­pared with the mea­sure­ments done dur­ing the ver­ti­cal tests.  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB381  
About • paper received ※ 19 May 2021       paper accepted ※ 24 June 2021       issue date ※ 25 August 2021  
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THPAB210 Extrapolated Range for Low Energy Electrons (< 1 keV) 4201
 
  • C. Inguimbert, M.B. Belhaj, Q. Gibaru
    ONERA, Toulouse, France
  • Q. Gibaru, D. Lambert, M. Raine
    CEA, Arpajon, France
  • Q. Gibaru
    CNES, PARIS, France
  
  Funding: ONERA- DPHY, 2 avenue E. Belin, 31055 Toulouse, France CEA, DAM, DIF, 91297 Arpajon, France CNES, 18 av. E. Belin, 31055 Toulouse, France
The Sec­ondary Elec­tron Emis­sion (SEE) process plays an im­por­tant role in the per­for­mance of var­i­ous de­vices. Mit­i­gat­ing the mul­ti­pactor phe­nom­e­non that may occur in ra­dio-fre­quency com­po­nents is a con­cern in many fields such as space tech­nolo­gies or elec­tron mi­croscopy. SEE is also a con­cern in the ac­cel­er­a­tor physics com­mu­nity, where the beam lines sta­bil­ity can strongly be af­fected by this phe­nom­e­non*,**. In that scope, the es­caped depth and thus the range of emit­ted elec­trons is of great in­ter­est. Our goal, by means of sim­u­la­tions is to pro­vide a bet­ter knowl­edge of SEE. We have de­vel­oped a Monte Carlo elec­tron trans­port code for low en­ergy elec­trons [~eV, ~10keV], that is part of the Dec. 2020 re­lease of GEANT4***. It has been used to study the prac­ti­cal range of low en­ergy elec­trons. Our goal is to for­mu­late, below ~10 keV, an an­a­lytic range vs. en­ergy ex­pres­sion, and to re­late it to fun­da­men­tal physcial pa­ra­me­ters such as the mean free paths of elec­trons in mat­ter. The goal is to pro­vide sim­ple prac­ti­cal ex­trap­o­lated range for­mula that can help to un­der­stand SEE phe­nom­e­non.
* M. Mostajeran et al. J. of Instr. 5 (2010)
** C. Y. Vallgren et al. Phys. Rev. Accel. Beam 14 (2011)
*** Q. Gibaru et al. Nuc. Inst. And Met. 487 (2021)
 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB210  
About • paper received ※ 10 May 2021       paper accepted ※ 23 June 2021       issue date ※ 27 August 2021  
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THPAB211 Monte Carlo Simulation of 3D Surface Morphologies for Secondary Electron Emission Reduction 4204
 
  • Q. Gibaru, M.B. Belhaj, C. Inguimbert
    ONERA, Toulouse, France
  • Q. Gibaru, D. Lambert, M. Raine
    CEA, Arpajon, France
  • Q. Gibaru
    CNES, PARIS, France
  
  Low en­ergy elec­trons of few tens of eV may cause Mul­ti­pactor break­downs in wave­guides dri­ven by the Sec­ondary Elec­tron Emis­sion Yield (SEY) of the walls. This risk is low­ered by using low emis­sive sur­faces and this topic has been stud­ied ex­per­i­men­tally and with nu­mer­i­cal sim­u­la­tions. The de­pen­dence of the SEY on sur­face prop­er­ties is well known*. Sur­face mor­phol­ogy has been widely used to re­duce the SEY by form­ing rough­ness pat­terns on the sur­face**. All pat­terns do not have the same ef­fi­ciency so their analy­sis in terms of SEY is rel­e­vant. Monte-Carlo sim­u­la­tion codes can be used to study the processes be­hind the SEY. The Mi­cro­Elec mod­ule of GEANT4 has re­cently been ex­tended with more ma­te­ri­als and processes and val­i­dated with ex­per­i­men­tal data for SEY cal­cu­la­tions**. In this work, sim­u­la­tion re­sults are shown for a bulk sam­ple capped with dif­fer­ent rough­ness pat­terns. The ef­fects of the shape pa­ra­me­ters on the SEY are stud­ied for typ­i­cal di­men­sions be­tween 20 µm and 100 µm. The re­sults are checked with ex­per­i­men­tal SEY mea­sure­ments on sam­ples with sim­i­lar rough­ness pat­terns.
*:T Gineste et al, Appl Surf Sci 359 (2015) 398-404
**:J Pierron et al, J Appl Phys 124 (2018) 095101
***:Q. Gibaru, C. Inguimbert, P. Caron, M. Raine, D. Lambert, J. Puech, NIM B. 487 (2021) 66-77 		 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-THPAB211  
About • paper received ※ 12 May 2021       paper accepted ※ 23 June 2021       issue date ※ 17 August 2021  
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