ILC-CR-0004 Main Linac extension:
Implementation status
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Overview
• the most recent “official” release of ILC lattice description files (MAD8 Extended
Standard Input Format files), corresponding to the TDR, was made at ALCWS-2015 in
April and designated “ILC2015a”
- https://bitbucket.org/whitegr/ilc-lattices
• goals of present work:
- implement Change Request #2 (CR02) … single 4.1 m L* for both detectors
> merge ILC2015a FF design with T. Okugi design … FF length increased by 11.64 m
> includes Change Request #6 (CR06) … IP BPM
- fix error in laser wire chicane length in BSYs … maintain identical e- and e+ systems
> BSY length decreased by 23.87 m
> photon path length (undulator exit to target) decreased by 12.23 m
* ~372 m to ~360 m
* 40 m drift space in e- system (d/s dogleg) to bypass target infrastructure
- implement Change Request #4 (CR04) … extension of Main Linac tunnels
> pLET system (pDR → IP) length increased by 2965.609 m (after changes mentioned
above)
> part of length increase in pLTL, part between pBC2 and pML, the rest at the end of
pML (before pMPSCOL)
> includes Change Request #10 (CR10) … BC1 and BC2 part of Main Linac
> path length difference (e-/e+) set to 10 x CDR
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LTL to
turnaround
match
LTL
FODO
cells
DR extraction
BC2 to
Main Linac
match
turnaround
Return Line
Main Linac
Main Linac
extension
IP
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e+ system changes for CR04
• pLTL
- add 20 “RETURNCELLC” FODO cells after MARKer “M_8_cell_end”
> did NOT change FODO cell length (still 72.493 m cell length)
- add 32.939 m to “RTMATCH” beamline just upstream of turnaround
- rematch return line to turnaround
• pBC2
- add 88.5 m to “BC2_ML_2” beamline (matching between pBC2 and pML)
- rematch pBC2 to pML
• pML
- inserted space for an additional complete 12-string (36 ML unit) cryo unit … details to
follow
• pBSY
- shorten laserwire chicane from 76.9 m to 42.6 m
> shorten center drift from 11.5 m to 5.0 m
- replace eight (8) quadrupoles used to match to FF through polarimeter chicane
> old: length = 3 m, bore = 80 mm
> new: length = 2 m, bore = 12 mm
- rematch BSY to FF through polarimeter
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LTL
turnaround
LTL FODO cells
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LTL
turnaround
RTMATCH
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kickers
BC2
Main Linac
BC2_ML_2
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Main Linac
BSY
DUNIT1
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• positron Main Linac extended at downstream end (before MPS collimation)
• inserted space for an additional complete 12-string (36 ML unit) cryo unit
- include space for end boxes, service boxes, and warm drifts
- same quadrupole center-to-center spacing as Main Linac
- same cryo unit-to-unit spacing as Main Linac
- replace cryogenic quadrupoles with BDS “Q75L2000” magnets
> core length = 2 m, bore = 75 mm
- maintain Main Linac optics (β-functions)
• no additional cryomodules included (drifts, quads, BPMs, XCORs, and YCORs only)
• if populated with cryomodules, would provide an additional ~30 GeV of acceleration
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From “TDR lattice (2015a) review and status” (ALCW-2015)
https://agenda.linearcollider.org/event/6557/session/7/contribution/77/material/slides/1.pdf
Recreating the TDR CFS geometry
subsystems
comments
EBSY1 / EBSY2
PBSY1 / PBSY2
Redefinition errors discovered during “deck integration”:
• polarimeter chicanes were copied from *BSY2 to *BSY1 as separate laserwire detection chicanes
• names of elements (bends and drifts) were not changed
• names of parameters that defined bend and drift lengths were not changed
• values of parameters that defined bend and drift lengths were changed in *BSY1 files
• when *BSY1 file is loaded, LW chicane is 45.1 m long
• when *BSY2 file is loaded, LW chicane is redefined to be 76.9 m long (ΔL = 31.8 m)
• TDR CFS coordinates include BSY LW chicanes that are each 31.8 m too long
PBDS was 0.95 m shorter than EBDS due to rematching between PBSY and PFFS, so:
• shorten PMPSCOL by 0.95 m and rematch
• modify PBSY2 such that EBDS and PBDS are now identical
• redefine TDR CFS coordinates for TPML2BDS Treaty Point (e+) to be symmetric w.r.t. IP with
TPS2EBDS treaty point (e-)
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MPS collimation
FF
kickers
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From “Report of Global Timing Working Group”
EDMS number: D00000001097725
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ΔS = ±340 mm
From T. Okugi’s presentation at POSIPOL2015
https://eventbooking.stfc.ac.uk/uploads/posipol/posipolokugi20150902.pdf
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From “SB2009 Proposal Document”
https://ilc-edmsdirect.desy.de/ilc-edmsdirect/file.jsp?edmsid=D00000000900425
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Continuing Work
• MAD8 SURVEY tape-file output precision (10 digit) is too small for total LET (length > 32
km) … need to use sum(Li) for μ-level precision!
- investigate using MAD-X instead of MAD8
• fix path length between kickers and septa in DR (127 μm + 32 μm = 159 μm error)
• make identical modifications to electron systems
- DR injection/extraction model
- space for 12-string (36 ML unit) cryo unit in eML
- FODO cells in eLTL
• add path length adjustment chicane in e+ source system
- Okugi-san’s chicane after booster linac (same location relative to booster linac)
- assume ±230 mm range (as specified in CR04) … set initially to +230 mm and readjust
path lengths
- don’t move booster linac or include new energy compressor yet (Change Request)
• verify BSY laserwire chicane offset large enough for laserwire photon detection
- old (polarimeter) chicane offset was 20 mm … offset now is 8 mm
• don’t change eBSY fast abort line (requires further study)
• shift all Treaty Point coordinates to restore IP to origin (0,0,0)
• earth’s curvature following and vertical dispersion only if time permits
• release ILC2015b in 2015 (!)
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Conclusions and Outlook
• implementation of CR-0004 is about 50% complete
- need to apply positron system modifications to electron systems
- need to add positron path length correction chicane
- need to shift coordinate system / Treaty Points to restore IP at origin (0,0,0)
- still hoping to finish in 2015!
• e+/e- path lengths now differ by exactly 10 x CDR (within 1 μm)
- there are sub-millimeter path length errors in DR Injection/Extraction layout to fix
• all changes (such as they are) will be available from the Lattice Repository (from the
“dev” branch)
• ILC2015b to be next release
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End
Thanks!
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