TraceWin Lattice for FNAL Drift-Tube Linac: Status

1
TraceWin Lattice for FNAL Drift-Tube Linac
Status

• Valery Kapin
• 30-Jul-2014
• PIP General Meeting

2
Contents

• Start with the lattice file for FNAL DTLs with
  old PARMILA based on MM1968 data (not convenient
  interface gt 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 -gt 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 PARMILAs 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 gt DTL12 (BNL pattern)DTL3-5(FNAL
  pattern) gt larger transverse acceptances (gt50)
• Needs for accurate 4-rod RFQ MEBT lattices gt
  TraceWin lattice with field maps extracted from
  MWS for sections/cells

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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 DTLs pre-injector (4-rod
  RFQ)

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(F)NAL BNL DTL tank geometries are the same
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BNL DTL tank had NOT been designed by PARMILA
9-DTL 200-MeV 138m Linac dL 1.3cm (0.01) DW
170keV (0.1)
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Example of Messymesh data printout (1968 for
BNL DTL) for one cell
MM calculates E/M parameters of linac cell and
output TTFs
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Drift-tube geometry - restored
VK01 - only Messymesh data
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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)
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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 "CHANGE4" (green
crosses).
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Start with the lattice file for FNAL DTLs based
on Messymesh1968 data with 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 ltOUT1_good_bad_parti
cles.outgt for FNAL DTL1-5 (text-file gt external
plotting soft)
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Old PARMILA SUBNUM8 example
SUBNUM 8 Plots two profiles as functions of
cell number SUBNUM 8 (34) dPhi dW profiles
dPhiMax180deg dWmax1MeV ---------------- OUTPUT
2 1 34 180 1. 220.11 1 204 1 OPTCON 0 0
Coding Number for plot Types and frame sizes
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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
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TraceWin code (con-ed)
What physics is inside? DTL_CELL ?
VE0TL, Qs Must be known a priory They
are written into a lattice file ! Supposing A
true design particle!
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Wanglers book page 202
What physics is inside? DTL_CELL ?
Tracking according to Lapostolle Co treatment,
not PARMILAs (Swensons style) see discussion
in LINAC bible (1970) In 1960-70 multi-step
integration (e.g.Runge-Kutta timememory
consuming!) TTF definitions are different from
PARMILAs ! TTFs are expanded around a given
synchronous particle gt still design code
! Exact implementation in TraceWin is unknown
(e.g. at center or entrance)
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Discussion from LINAC bible 1970
Tracking method in TraceWin according to
Lapostolles Formulae is similar to one in
PARMILAs (Swensons style) Driftthin-lensdri
ft
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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
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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
  (driftkickdrift)
• Particle losses largest constant radius of
  aperture
  (instead of stepwise increase
  1.01.251.52.0)
• Equivalent particle trajectory shift value for
  both phase radial position
  
  due to wrong value of T(k)

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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 PARMILAs 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 (driftkickdrift).
Benchmarking of results might be useful.
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Beam dynamics with a nominal Q-strengths Finding
Longitudinal Acceptance DTL1-5
Within separatrix non-linear oscillations
Beam exy-gt 0 Ibeam0
Zoom
Surv. Particles At DTL1 Entry
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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
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Long. Accept. small (linear) oscillations
1) drawing inscribed "small (linear
oscillations)" 25-ellipse with a plotting soft
(abconst shifted center) 2) superpose it on
large accept.
Test run with 0-loss (Beam exy-gt 0 Ibeam0)
Figs Entry Exit e(z)
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Beam dynamics with a nominal Q-stengths Finding
Transverse Acceptance X-Xplane
Particles At DTL1 Entry (surviveddark)
Inj. beam ey,L-gt 0 Ibeam0
Zoom
Zoom
Entry Exit
Not yet 100
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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
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Beam dynamics with a nominal Q-stengths Finding
Transverse Acceptance Y-Yplane
Reduce y-emittance until 100 transm. is reached
(as for x-x)
DTL1 Entry
DTL5 Exit
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Partial acceptances unmatched input beam
Calculated partial acceptances (for 0-loss, I0
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
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Unmatched input beam
Blue ellipses acceptances red elipses Total
5-rms Emittances (unnorm.)
Iout(Iinp2mA)1.76mA (88)
Iout(Iinp50mA)43.2mA (86)
Iout(Iinp100mA)68mA (68)
Imax(Iinp140mA)74mA (53)
Current dependent e-growth In all 3 phase space
(L2 X4 Y6.5 times)!
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Matched input beam
Blue ellipses - DTLs acceptances red elipses
Total 5-rms beam Emittances (unnorm.)
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Matched input beam e-growth I-transmission
Current dependent e-growth In all 3 phase space
(L2 X6 Y6.5 times)!
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Losses matched vs mismatched (Iinj1mA 45mA)
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Ibeam mA matched vs mismatched (Iinj1mA 45mA)
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ez,norm matched vs mism. (Iinj1mA 45mA)
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e t,norm matched vs mism. at Iinj1mA 45mA
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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

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Quad. Strengths and Smith-Gluckstern stability
diagram
BNL linac (1990)
FNAL linac (nomin. Qs)
Quads in DTL1
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Simple Smoothing of quad. G(nq)
Quad. gradient G vs quad number nq for DTL12
use BNLs (AK90) for DTL3-5 use FNALs nominal
(FG01). Liner interpolation equate adjacent Quad
pairs (common power supply) Keep Quad-settings at
the tank ends (matching between tanks in a future)
36
Q-smoothing DTL3-5
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Increased acceptances for smoothed G(nq)
a) blue original red smoothed Quads
X-acceptance 1.5-gt2.3 Y-acceptance 1.4-gt4.0
Y-Y plane
X-X plane
b) blue original red smoothed (Q2-3 exactly
as AK90)
X-acceptance 1.5-gt2.6 Y-acceptance 1.4-gt2.6
(w/o matching With MEBT beam at DTL1 entry)
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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 gt 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 !
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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 2gtAcc.
cell 3gt Front end cell 4gtTranscell
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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

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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.
  (gt50)Matching at entry and in inter-tanks
  might be needed
• Limitations for simulations of a real beam
  discussed supplementary or other code (ala
  TRACK) is needed
• The lattices for MEBT 4-rod RFQ should be
  studied updated for more accurate simulations