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TraceWin Lattice for FNAL Drift-Tube Linac: Status

TraceWin Lattice for FNAL Drift-Tube Linac: Status. Valery Kapin 30-Jul-2014 PIP General Meeting. Start with the lattice file for FNAL DTLs with old PARMILA based on MM~1968 data (not convenient interface –> command codes) TraceWin code (only exe, commercial) with user-friendly interface

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TraceWin Lattice for FNAL Drift-Tube Linac: Status

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  1. TraceWin Lattice for FNAL Drift-Tube Linac: Status Valery Kapin 30-Jul-2014 PIP General Meeting

  2. Start with the lattice file for FNAL DTLs with old PARMILA based on MM~1968 data (not convenient interface –> command codes) TraceWin code (only exe, commercial) with user-friendly interface Existing DTL lattice (by Kim?) for TraceWin used by J.P. (~2013);My inspection -> inaccurate interpretations of “DTL_CELL” elements TraceWin lattice generation: old PARMILA outputs “DTL_cell” lines via post-processing of MM-data & DTL cell parameters generated by PARMILA’s GENLIN subroutine Beam dynamics simulations with a nominal Q-stengths: 1) mismatched input beam; 2) input beam matched to DTL acceptances Beam dynamics simulations with “smoothed” cell-by-cell quadrupole strengths: SG stability diagram => DTL1&2 (BNL pattern)+DTL3-5(FNAL pattern) => larger transverse acceptances (>50%) Needs for accurate “4-rod RFQ” & MEBT lattices => TraceWin lattice with field maps extracted from MWS for sections/cells Contents V.Kapin, PIP meeting, July-2014

  3. Previous 2013 presentation Beams-doc-4293-v1 • Review previous talks: - D.McGinnis(2011); - H.J.Kim(Jan-2012) • New restart in Oct-2012 by VK • Optics reconstruction for accelerator model • SNS: XAL(Java) online models • PARMILA new vs old versions • A new configuration for on/off-line modeling • Overview FNAL DTL lattices • FNAL & BNL designs – history • New lattice based on MM68 data is well agree with BNL 1990 lattice and all published design specifications • Questions on intertank distances and quad strengths • About on-line modeling DTL’s pre-injector (4-rod RFQ) V.Kapin, PIP meeting, July-2014

  4. (F)NAL & BNL DTL tank geometries are the same V.Kapin, PIP meeting, July-2014

  5. BNL DTL tank had NOT been designed by PARMILA 9-DTL 200-MeV 138m Linac: dL =1.3cm (~0.01%); DW = 170keV (~0.1%) V.Kapin, PIP meeting, July-2014

  6. Example of Messymesh data printout (~1968 for BNL DTL) for one cell MM calculates E/M parameters of linac cell and output TTFs V.Kapin, PIP meeting, July-2014

  7. Drift-tube geometry - restored VK01 - only Messymesh data V.Kapin, PIP meeting, July-2014

  8. TTFs from MM68 and might be corrected for tracking Original Messymesh TTFs have be used for design; PARMILA should use original for design (step1 - GENLIN), and refined TTFs for tracking (step2; also for TraceWin) V.Kapin, PIP meeting, July-2014

  9. Restore field tilt in DTL1 C. Curtis et al, in report "fermilab-fn-0201“; HEACC-7, Yerevan, 1969, USSR, p.192-204. The plot (left) has been digitized and normalized values from the 1969-plots had been converted into absolute values of the electrical field strength needed for PARMILA. The right plot shows the measured field (red circles), the design field (blue-line), the gap fields set with by PARMILA's command "CHANGE=4" (green crosses). V.Kapin, PIP meeting, July-2014

  10. Start with the lattice file for FNAL DTLs based on Messymesh~1968 datawith old PARMILA V.Kapin, Post-processing for old Parmila (SY12): notes with examples for FNAL DTL, June-2013, 20pages • OUTPROC: • SUBNUM# command codes: • not convenient interface • NOT for a CASUAL (MODERN) USER! The example plot from data in <OUT1_good_bad_particles.out> for FNAL DTL1-5 (text-file => external plotting soft): V.Kapin, PIP meeting, July-2014

  11. Old PARMILA: SUBNUM8 example : SUBNUM 8 : Plots two profiles as functions of cell number SUBNUM 8 : (34) dPhi & dW profiles: dPhiMax=180deg dWmax=1MeV ---------------- OUTPUT 2 1 34 180 1. 220.11 1 204 1 OPTCON 0 0 Coding Number for plot Types and frame sizes V.Kapin, PIP meeting, July-2014

  12. TraceWin code (only EXEcutable, commercial) with a user-friendly interface What physics is inside? “DTL_CELL” ? Source code is not available; Manual is in a laconic & briefly style (in English, but some chapters in French) Need to communicate With code owners ! In red box: from my E-mail communications V.Kapin, PIP meeting, July-2014

  13. TraceWin code (con-ed) What physics is inside? “DTL_CELL” ? V=E0*T*L, Qs – Must be known “a priory” – They are written into a lattice file ! Supposing A true design particle! V.Kapin, PIP meeting, July-2014

  14. What physics is inside? “DTL_CELL” ? “Wangler’s book page 202” Tracking according to Lapostolle & Co treatment, not PARMILA’s (Swenson’s style) – see discussion in LINAC bible (1970) In 1960-70 multi-step integration (e.g.Runge-Kutta – time&memory consuming!) TTF definitions are different from PARMILA’s ! TTFs are expanded around a given synchronous particle => still “design code” ! Exact implementation in TraceWin is unknown … (e.g. at center or entrance) V.Kapin, PIP meeting, July-2014

  15. Discussion from LINAC bible 1970 Tracking method in TraceWin according to Lapostolle’s Formulae is similar to one in PARMILA’s (Swenson’s style): “Drift+thin-lens+drift” V.Kapin, PIP meeting, July-2014

  16. Existing TraceWin Start-to-end lattice J.P. Carneiro, The FNAL 400 MeV Linac in TRACEWIN (from Ion Source to Stripping Foil), PIP meeting, 12-June-2013. Start-to-end Model with TRACEWIN; (TRACEWIN and TOUTATIS;) Citation: “How was the model built ? • LEBT (35 keV): from TRACE2D input file (CY Tan, D. Bollinger) • RFQ (750 keV) : from PARMTEQM input file (CY Tan) • MEBT +DTL (117 MeV) + CCL (400 MeV) : from PARMILA input file (H.J. Kim)” Out: TraceWin lattice file “fnal_pip_linac.dat” containing “RFQ_CELL”, “DTL_CELL” (by Kim ?) etc. commands V.Kapin, PIP meeting, July-2014

  17. Inspection of existing TraceWin lattice inaccurate interpretations of “DTL_CELL” elements Gap shift ignored: As for symmetrical cell R aperture 20mm assumed everywhere in DTL1-5 Wrong by factor “-2p” • Inaccurate values will affect on beam dynamics results: • Equivalent particle trajectory – position of trajectory bend due to the gap center position (“drift+kick+drift”); • Particle losses – largest & constant radius of aperture (instead of stepwise increase 1.0;1.25;1.5;2.0) • Equivalent particle trajectory – shift value for both phase & radial position due to wrong value of T’(k) V.Kapin, PIP meeting, July-2014

  18. TraceWin lattice generation Old PARMILA (with specially written using FORTRAN source code) outputs “DTL_cell” lines via post-processing of MessyMesh-data & DTL cell parameters generated by PARMILA’s GENLIN subroutine Several parameters are needed at the cell centers (not at the ends as in PARMILA) Methods for particle tracking through the gaps in PARMILA & TraceWin are different, but based on the same approach (“drift+kick+drift”). Benchmarking of results might be useful. V.Kapin, PIP meeting, July-2014

  19. Beam dynamics with a nominal Q-strengths; Finding Longitudinal Acceptance DTL1-5 Within separatrix – non-linear oscillations Beam:exy-> 0; Ibeam=0 Zoom Surv. Particles At DTL1 Entry V.Kapin, PIP meeting, July-2014

  20. Finding Long. Acceptance DTL1-5(con-ed) Particles with non-linear oscillations Surv. Particles At DTL5 Exit Surv. Particles At DTL1 Entry TraceWin provides approx. ellipse Parameters & its shift: V.Kapin, PIP meeting, July-2014

  21. Long. Accept.: small (linear) oscillations 1) drawing inscribed "small (linear oscillations)" 25%-ellipse with a plotting soft (a&b=const; shifted center) 2) superpose it on large accept. Test run with 0%-loss (Beam: exy-> 0; Ibeam=0): Figs: Entry; Exit; e(z) V.Kapin, PIP meeting, July-2014

  22. Beam dynamics with a nominal Q-stengths; Finding Transverse Acceptance X-X’plane Particles At DTL1 Entry – (survived=dark): Inj. beam: ey,L-> 0; Ibeam=0 Zoom Zoom Entry & Exit Not yet 100% V.Kapin, PIP meeting, July-2014

  23. Beam dynamics with a nominal Q-stengths; Finding Trans. X-X’ Accept. (con-ed) Reduce x-emittance until 100% transm. is reached DTL1 Entry: DTL5 Exit: V.Kapin, PIP meeting, July-2014

  24. Beam dynamics with a nominal Q-stengths; Finding Transverse Acceptance: Y-Y’plane Reduce y-emittance until 100% transm. is reached (as for x-x’) DTL1 Entry: DTL5 Exit: V.Kapin, PIP meeting, July-2014

  25. Partial acceptances & unmatched input beam Calculated partial acceptances (for 0%-loss, I=0 & zero emittances in other planes) Initial parameters of unmatched injected beam (file "pmi2tw.dst" by new PARMILA): Input 35 10000 1.269 20.18 0.0128 2.138 38.01 0.0083 50 0.05 0.0 0 0 0 0 0 0 V.Kapin, PIP meeting, July-2014

  26. Unmatched input beam Blue ellipses acceptances; red elipses: Total 5-rms Emittances (unnorm.) Iout(Iinp=2mA)=1.76mA (88%) Iout(Iinp=50mA)=43.2mA (86%) Iout(Iinp=100mA)=68mA (68%) Imax(Iinp=140mA)=74mA (53%) Current dependent e-growth In all 3 phase space (L~2; X~4; Y~6.5 times)! V.Kapin, PIP meeting, July-2014

  27. Matched input beam Blue ellipses - DTLs acceptances; red elipses: Total 5-rms beam Emittances (unnorm.) V.Kapin, PIP meeting, July-2014

  28. Matched input beam: e-growth & I-transmission Current dependent e-growth In all 3 phase space (L~2; X~6; Y~6.5 times)! V.Kapin, PIP meeting, July-2014

  29. Losses %: matched vs mismatched (Iinj=1mA& 45mA) V.Kapin, PIP meeting, July-2014

  30. Ibeam mA: matched vs mismatched (Iinj=1mA & 45mA) V.Kapin, PIP meeting, July-2014

  31. ez,norm: matched vs mism. (Iinj=1mA & 45mA) V.Kapin, PIP meeting, July-2014

  32. e t,norm: matched vs mism. at Iinj=1mA & 45mA: V.Kapin, PIP meeting, July-2014

  33. On emittance growth in proton linacs • References: • 1972 Batchelor Emittance vs Quads BNL LINAC_p47; • 1979 Jameson & Mills EmittanceGrowth in Linacs LinacConfProcs_p231 • 1979 Jameson Emittance Growth in Linacs HeavyIonFusionWorkshop_p84 • 1985 Wangler Emittance Growth of IntenseBEam PAC1985_2196 • 2008 Reiser Emittance Growth Ch06 in his book • 2008 Wangler SpCh Multiparticle Dynamic ch09 in RF linacs book • 2010 Wei Simulations of Errors JPARC Linac V.Kapin, PIP meeting, July-2014

  34. Quad. Strengths and Smith-Gluckstern stability diagram BNL linac (1990) FNAL linac (nomin. Qs) Quads in DTL1 V.Kapin, PIP meeting, July-2014

  35. Simple Smoothing of quad. G(nq) Quad. gradient G vs quad number nq : for DTL1&2 use BNL’s (AK90); for DTL3-5 use FNAL’s nominal (FG01). Liner interpolation; equate adjacent Quad pairs (common power supply) Keep Quad-settings at the tank ends (matching between tanks in a future) V.Kapin, PIP meeting, July-2014

  36. Q-smoothing DTL3-5 V.Kapin, PIP meeting, July-2014

  37. Increased acceptances for smoothed G(nq) a) blue= original; red = smoothed Quads X-acceptance: 1.5->2.3 Y-acceptance: 1.4->4.0 Y-Y’ plane X-X’ plane b) blue= original; red = smoothed (Q2-3 exactly as AK90) X-acceptance: 1.5->2.6 Y-acceptance: 1.4->2.6 (w/o matching With MEBT beam at DTL1 entry) V.Kapin, PIP meeting, July-2014

  38. XY e; centroid; I, A BPMs ; I, A BPMs ; I, A BPMs ; I, A ~Long e (PARMTEQ, tests) W-Phi Centroid MEBT RF cavity & Quads DTL5: E+d, PhiS+d, 24 gaps; 25 Qs DTL4: E+d, PhiS+d, 29 gaps; 30 Qs DTL3: E+d, PhiS+d, 35 gaps; 36 Qs DTL2: E+d, PhiS+d, 60 gaps; 61Quads DTL1: E+d, PhiS+d, 56 gaps; 57 Quads Grad(Qi, Qi+1)= F(I)+d 4-rod RFQ Known & unknown DTL parameters RF param.:Power Prf & phases between resonators dPhi are tuned for best Ibeam !? Prf & dPhi values unknown; different from design values E0 & PhiS used by TraceWin ! This difference affects on both long. & transv. Tracking results! Actual E0 & PhiS must be recalculated (additional code or another code, e.g. TRACK? Quad param.:Gradients are calculated from currents with ideal formulae ~5-10% There is no dipoles & BPMs inside => usual optics reconstruction is impossible Intertank BPMs: for correction of coherent oscillations (ini. Beam or misalignments) Initial beam:Transv. Emittances are measured (at what conditions ?); Long. Emittance – upright ellipse (ideal MEBT) via PARMTEQ (not for 4-rod RFQ) Particle Distributions (Gaussian etc) are unknown ! V.Kapin, PIP meeting, July-2014

  39. Existing 4-rod RFQ lattice with TraceWin • RFQ (750 keV) : from PARMTEQM input file (CY Tan) • RFQ: RFQ_CELL; RFQ_GAP_RMS_FFS etc. TraceWin manual: Analytical function for ideal RFQ with pure quad-symmetry (like 4-vane RFQ): Type: 2=>Acc. cell; 3=> Front end cell; 4=>Transcell V.Kapin, PIP meeting, July-2014

  40. Need for a correct TraceWin lattice for 4-rod RFQ • Existing TraceWin lattice (based on PARMTEQ-M lattice) • It ignore its inherent asymmetry; it describes an ideal RFQ with ideal Quad-symmetry like 4-vane RFQ (w/o dipoles) • Problems are in matching section and regular RFQ channel, where additional components generated. • Experimentally 4-rod RFQ never had a high transmission as PARMTEQ(M) predicted • Existing TraceWin lattice will not model features of 4-rod RFQ (acceptance; emittance & shifts of beam centroid). • I had worked on 4-rod RFQ simulations in 198x-199x (EPAC-94, Linac-94, JJAP-97) (see APCsem-2013) • Additional non-quadrupole fields in 4-rod RFQ were shown and a new model for beam dynamics simulations was used • I guess now it is possible simulate 4-rod RFQ with TraceWin using field maps from MWS V.Kapin, PIP meeting, July-2014

  41. Conclusion • TraceWin lattice for FNAL DTL1-5 is updated • Long. & Transv acceptances are calculated • Beam transmission and emittance growth for matched and unmatched beam are compared • Beam transmission for matched beam ~97% at 50mA • Emittance growth depends on Ibeam (unavoidable); it is the same for matched and unmatched beams • Simple smoothing of Grad(nq) increases accept. (>50%);Matching at entry and in inter-tanks might be needed • Limitations for simulations of a real beam discussed; supplementary or other code (a’la TRACK) is needed • The lattices for MEBT & 4-rod RFQ should be studied & updated for more accurate simulations V.Kapin, PIP meeting, July-2014

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