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Code parameters optimization & DTL Tank 1 error studies Maud Baylac, Emmanuel Froidefond Presented by JM De Conto LPSC-Grenoble HIPPI yearly meeting, Oxford,

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Presentation on theme: "Code parameters optimization & DTL Tank 1 error studies Maud Baylac, Emmanuel Froidefond Presented by JM De Conto LPSC-Grenoble HIPPI yearly meeting, Oxford,"— Presentation transcript:

1 Code parameters optimization & DTL Tank 1 error studies Maud Baylac, Emmanuel Froidefond Presented by JM De Conto LPSC-Grenoble HIPPI yearly meeting, Oxford, September, 2005

2 Overview Goal, recall TW inputs Optimization of code parameters Nb runs Nb calculations per βλ Nb particles Space charge routine: 2d vs 3d Mesh size Error study Individual sensitivity: longitudinal & transverse Effect of input distribution Global errors, loss Set of tolerances

3 Goal For us: learn how to use TraceWin Study sensitivity of DTL to quadrupole and field errors Determine set of tolerances for tank 1 for quadrupole alignment quadrupole gradient klystron field amplitude and phase gap field amplitude

4 TraceWin inputs Several inputs: evolutive DTL design Input distribution: mainly type -32 (Gaussian) file Worse case scenario & Same for all studies 2 types of simulations: Sensitivity: one type of error at a time (e.g.: δ x ) Global error effect: all types of errors at once Each error generated randomly & uniformly in [–max; +max] For all cases, transport to the end of the DTL

5 Number of runs Study convergence with nb of runs 1000 runs DTL 2004

6 Nb space charge calculations per βλ Inactive on DTL cells Default for DTL cells: was 1 space charge calc. per cell (ie: 20 calc. per betatron oscil.) modified to up to 3 calc. per cell (depending on cell length)

7 Number of particles Most simulations use 50 kparticles (1000 runs) –Fast calculation –Minimal loss: 20 ppm A few global error runs use 10 6 particles (5000 runs) –250 to 400 CPU hours –Minimal loss: 1 ppm

8 Space charge routines

9 Space charge routines comparison 2d vs 3d disagreement can be very large Not understood Example: 1 run with 1.5 mm x displacement of the 1 st quad with PICNIR & PICNIC PICNIR (2d) PICNIC (3d) DTL 2004

10 large for large emittance growth if X ≠ Y (our case) increases with beam current much more pronounced for FFDD vs FODO for transverse phenomenon Agreement for longitudinal errors (unexplained) Space charge routines disagreement  Use 3d PICNIC with optimized mesh size

11 Optimization of mesh size Gausup 3d (PICNIC) 2d (PICNIR) Mismatch beam (40% in x/y/z) at DTL input to generate large emittance growth

12 7x7 mesh size through DTL Gausup 3d (PICNIC) 2d (PICNIR) Matched beam through DTL: validation of mesh size

13 DTL with all errors 7x7 mesh statistically compatible with high resolution mesh & keeps calculation time reasonable

14 Sensitivities to longitudinal errors Gaussian distribution, 50 kpart, 1000 runs Error type Max error amplitude (mm or deg) ± rms (%) ± rms (%) ± rms (%) Longitudinal errors  E klys /E klys = ± 1%  φ klys = ±1deg  E gap /E gap = ± 1% 0.0 ± ± ± 0.7 Very little effect for all 3 longitudinal errors combined DTL 2005

15 Sensitivities to transverse errors Gaussian distribution, 50 kpart, 1000 runs Error type Max error amplitude (mm or deg) ± rms (%) proba (%) ± rms (%) proba (%) ± rms (%) proba (%) Displ x±0.1 mm 1.0 ± 0.8 <1% : 60 <5% : ± 0.1 <1% : 100 <5% : ± 0.5 <1% : 76 <5% : 100 Rota x (pitch) ±0.5 deg 0.01 ± 0.01 <1% : 100 <5% : 100 1E-3±3E-3 <1% : 100 <5% : ± 0.01 <1% : 100 <5% : 100 Rota z (roll) ±0.2 deg 0.8 ± 0.6 <1% : 76 <5% : ± 0.6 <1% : 77 <5% : ± 0.02 <1% : 100 <5% : 100  G/G ±0.5% 0.1 ± 0.2 <1% : 100 <5% : ± 0.3 <1% : 100 <5% : ± 0.07 <1% : 100 <5% : 100 Some emittance growth No loss Energy jitter: a few 10-4 Phase jitter: a few DTL 2005

16 Longitudinal rotation (roll) Emittance growth similar in x & y (coupling) Emittance growth quadratic with roll angle Confirmed by theoretical calculations No longitudinal emittance growth DTL 2005

17 Effect of input distribution Design & Distribution ± rms (%) proba (%) ± rms (%) proba (%) ± rms (%) proba (%) RMS x (mm) & RMS x’ (mrad) RMS y (mm) & RMS y’ (mrad) Losses 2005 Gaussian 2.0 ± 1.0 <1% : 13 <5% : ± 1.0 <1% : 15 <5% : ± 0.8 <1% : 28 <5% : & & 0.8 Loss < 2E KV 1.5 ± 1.0 <1% : 35 <5% : ± 1.0 <1% : 37 <5% : ± 0.7 <1% : 57 <5% : & & 0.9 Loss < 2E-5 Gaussian distribution, 50 kpart, 1000 runs Simple shift (30-50%), no broadening DTL 2005

18 Effect of input distribution: transverse errors DTL 2005

19 Global effect with high statistics: transverse & longitudinal errors and  φ/φ=±1 deg  E/E klystron =±1%  E/E gap =±1% Design & errors ± rms (%) proba (%) ± rms (%) proba (%) ± rms (%) proba (%)  E ± rms (keV)  φ ± rms (deg) Losses 2005 Trans. 2.0 ± 1.0 <1% : 13.8 <5% : ± 1.0 <1% : 14.2 <5% : ± 0.8 <1% : 26.5 <5% : ± ± 0.01Loss < 1E Trans.+ longi. 2.0 ± 1.2 <1% : 20.4 <5% : ± 1.2 <1% : 20.3 <5% : ± 1.1 <1% : 20.1 <5% : ± ± 0.15Loss < 1E particles, 4291 runs, Gaussian input, 250 to 400 CPU hours for each run δ x/y = ±0.1 mm Φ x/y = ± 0.5 deg Φ z = ± 0.2 deg  G/G = ±0.5% Some broadening in longitudinal direction

20 Main trends of quadrupole alignment Transverse displacement (symmetric x/y ) transverse & longitudinal emit. growth 2005 design: ~ 1% for ±0.1 mm Transverse rotation (pitch & yaw): no effect Longitudinal rotation (roll): transverse emit. growth 2005 design: ~ 0.8% for ±0.2 deg Emittance growth with 2005 design vs 2004 design: slightly worse with errors on all tanks Individual sensitivities roughly add up

21 DTL tank 1 tolerances Tolerances agreed upon by DTL task force: quadrupoles: longitudinal displacements: δ x,y = ±0.1 mm longitudinal rotations: Φ x,y = ±0.5 deg transverse rotations: Φ z = ±0.2 deg gradient:  G/G = ±0.5% accelerating field: klystron field amplitude:  E klys /E klys = ±1% klystron field phase:  φ klys = ±1deg gap field amplitude:  E gap /E gap = ±1%

22 Conclusions Sensitive parameters: transverse displacement & roll Little effect due to longitudinal errors (longitudinal shift cannot be tested with TW) With present tolerance budget, beam quality sees little degradation through DTL: Emittance growth x, y and z < 5% in 98% of runs Loss < RMS width in x and y < 1.2 mm RMS width in x’ and y’ < 1.1 mrad Multipolar component contribution: waiting for TW debug Code benchmarking to validate results

23 Acknowledgements Didier URIOT (CEA/DSM) for discussions and multiple debugs Nicolas PICHOFF (CEA/DAM) for discussions regarding space charge calculations Edgar Sargsyan, Alessandra Lombardi and Frank Gerigk (CERN) for inputs and discussions


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