Self-Focusing Bunches for High Brightness Acceleration
Explore the concept of self-focusing bunches for high brightness acceleration in particle accelerators. Learn about beam loading effects, linear regimes, transverse contributions, and energy spread growth for high-quality acceleration. Witness transverse matching, beam loading compensation, and important considerations for achieving optimum beam quality. Discover insights from studies on energy loss analysis, accelerating field equations, and plasma-based accelerators.
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Presentation Transcript
Self focusing bunches for high brightness acceleration Stefano Romeo on behalf of SPARC_LAB collaboration stefano.romeo@lnf.infn.it
Self focusing bunches The driver generates a linear field Witness can be injected on crest The field generated by the witness is non linear Focusing is guaranteed by a beam loading effect 4 ??=2 ? ??= ? ??? 4 1 2?? ?? ??= ?? ? 2 Stefano Romeo Frascati 13/03/2018
High quality acceleration in linear regime Transverse contribution (sliced) 2? ? ? 2????2 ??? 8??,? Spherical aberration coefficient ??= 2 4??,? 4 4??,? 4 4??,? 4?(0) 2??,? 4 2 +3?? +3?? 16?2(0) ?? 2+ 1 ?0 2??,? tan2?0?? 2 ??,?= ??,? ? Bunch length LT correlation Chirp Energy spread growth High quality requires: ??,? ??,? ????,? 1 In many realistic cases, beam loading is not negligible 3 Stefano Romeo Frascati 13/03/2018
Energy spread growth Barov, Nick, et al. "Energy loss of a high-charge bunched electron beam in plasma: Analysis." Physical Review Special Topics-Accelerators and Beams 7.6 (2004): 061301. The longitudinal field generatedby a low chargehigh density bunch can be described by linear equations The beam loading compensationoccurs whenthe first derivative of the acceleratingfield in the center of the witness is 0 Chiou, T. C., and T. Katsouleas. "High beam quality and efficiency in plasma-based accelerators." Physical review letters 81.16 (1998): 3411. LCLS, CDR, ch07. SLAC From the analytical model of field it is possible to evaluatethe energy spread ??? ??= 0 sin?0=?? Beam loading compensation ?? For any witness in a great range of parameters it s possible to find a bunch separation that guarantees beam loading compensation 23?? 4??,? 4 Energy spread growth depends only on witness length 4 2+ 1 ?0 ??,?= ??,? ? 4 Stefano Romeo Frascati 13/03/2018
Witness transverse matching A correlated focusing on longitudinal dimension causes emittance growth ??,?=?2??2? ?2? ? Energy spread compensation using beam loading (NO BUNCH SHAPING) Hypotesis of quasi-linearity Lu, W., et al. "A nonlinear theory for multidimensional relativistic plasma wave wakefields a." Physics of Plasmas 13.5 (2006): 056709. ??? ??= 0 ?(?? ???) ?? = 0 ??= 0 ?(?? ???) ?? ?? ??,?= 0 ??= 0 = 0 Consequences ? =?0 4 1 2?? ?? Ion column model can be applied Stupakov, G., et al. "Wake excited in plasma by an ultrarelativistic pointlike bunch." Physical Review Accelerators and Beams 19.10 (2016): 101302. ??= ? 2 5 Stefano Romeo Frascati 13/03/2018
SPARC_LAB layout for beam driven PWFA experiments ? ??? ??? ??? ? ?.? ? ?? ???? ??< ?.?% ??= ? ?? ?? High quality PWFA Beam diagnostic Photoinjector that allows to create trains of high quality electron bunches C band accelerating cavity 2 S band acceleratingcavities (velocity bunching) FEL 6 Stefano Romeo Frascati 13/03/2018
Working point design General comprehension of a phenomenon / Proof of principle SPARC_LAB Working Point Driver Injection Witness Injection ? 200 200 ??[ m] 10.3 1.26 Limited number of simulations 37.2 3 ??[ m] ??[%] 0.1 0.1 ??[ m] 17 0.3 Detailed analysis of phenomenon features / Optimization of working point ?[pC] 200 10 ?[kA] ? ?0[cm 3] 0.68 0.42 1.2 0.06 2 1016 Parametric scans 1-2 ??[GV/m] 5 ?[cm] 7 Stefano Romeo Frascati 13/03/2018
Hybrid Tool: Architect Bunch(es) are treated kinetically background plasma as a fluid cylindrical symmetry assumed run time figure of merit: 1cm/h no-Quasi Static Approximation ???????????= ? ? + ?????????? ? dt?????????= ?????????? ????= ? ????? ????= ? ?? ??? + ? ? + ??? ? ??? = ? ? ??? = ?2? ? ??0?3(????+ ????) Code reliability respect to full PIC code showed both for linear and quasi-linear regimes 8 Stefano Romeo Frascati 13/03/2018
Bunch separation scan sin?0=Q? ?? The model developed for the scheme doesn t forsee the driver head erosion effects A simulation scan is required in order to evaluate ?0 Optimal injection distance ?.????? 9 Stefano Romeo Frascati 13/03/2018
Witness longitudinal phase space 10 Stefano Romeo Frascati 13/03/2018
Outcoming witness parameters SPARC_LAB Working Point Driver Injection Witness Injection Witness Extraction ? 200 200 300 ??[ m] 10.3 1.26 1.3 ??[ m] 37.2 3 3 ??[%] 0.1 0.1 0.2 ??[ m] 17 0.3 0.31 ?[pC] 200 10 10 ?[kA] 0.68 0.42 0.42 ? 1.2 0.06 0.06 ?0[cm 3] 2 1016 ??[GV/m] 1 ?[cm] 5 11 Stefano Romeo PhD defense La Sapienza, University of Rome 2017/09/20
Stability analysis A scan of 30 simulation was performed using the latin hypercube sample in order to analyze the working point It was useful to prove the robustness of the scheme ? = 157 7.2 MeV ??= 0.307 0.005 mm mrad ??= 0.4 0.15% 12 Stefano Romeo Frascati 13/03/2018
Conclusions Results Low energy working point Scaling laws Future perspectives Model for head erosion Cross-check of the results with full PIC/3D codes Simulation scan in order to propose a possible EuPRAXIA working point is on chart 13 Stefano Romeo PhD defense La Sapienza, University of Rome 2017/09/20
