Beam Delivery update

1
Beam Delivery update

• Andrei Seryi
• adapted from the talk on GDE meeting last week,
  will skip most of slides
• December 12, 2005

GDE Meeting at INFN-LNF
2
Plan of the talk

• List, very briefly, topics where progress were
  made after Snowmass
• Describe in more details RD progress in areas
  relevant to IR configuration
• Describe ranking of IR configurations
• Present example, where evaluation is ongoing and
  ranking is still being discussed
• Outline plans for the next year
• If time left (unlikely), comment in more details
  about design progress in some of the areas

3
Snowmass Baseline Alternatives

• Baseline (supported, at the moment, by GDE exec)
• two BDSs, 20/2mrad, 2 detectors, 2 longitudinally
  separated IR halls
• Alternative 1
• two BDSs, 20/2mrad, 2 detectors in single IR hall
  _at_ Z0
• Alternative 2
• single IR/BDS, collider hall long enough for two
  push-pull detectors

2006 gt will work on design and cost of baseline,
choose IR configuration (20,14,2,0mr) of
Alternative 2 and cost it
4
Design and RD progress since Snowmass (1)

• Evaluate possibility to remove full power tune-up
  dumps
• Collimation optimization, calc. of wakes beam
  damage
• Prepare ESA (BDS instrumentation IR facility)
  run at SLAC
• ATF2 design, fabrication of hardware,
  collaboration
• Work with detector concepts to minimize solenoids
  leakage
• Optimize DID field shape to be more TPC friendly
• Introduced anti-DID to minimize pairs background
• Work on linac and BDS stability criteria (with
  WG1)
• Optimize self shielded compact SC quad design,
  produce a prototype and make successful
  experimental test at BNL

ESA End Station A at SLAC ATF2 Accelerator
Test Facility -2 at KEK DID Detector Integrated
Dipole anti-DID DID with reverse sign of the
field TPC Time Projection Chamber
5
Design and RD progress since Snowmass (2)

• Consider effects of e source location
• Work on diagnostics system optimization laser
  wire requirements
• Continue crab cavity design study, plan phase
  stability tests in UK
• Evaluate effects of parasitic crossings in
  head-on case
• Study of beam-cal performance to detect small
  angle tagging electrons
• Studying losses in extraction line for various
  design, parameters and study effects on
  diagnostics IR background
• Continue work on forward region optimization
• Study of beam-beam and pair productions, EM
  deflection effect on Bhabha scattering

6
Intermediate crossing angle

• At Snowmass, WG4 suggested to study intermediate
  crossing angle and asked 2-3month to complete
  design
• Motivations for intermediate crossing angle
• Snowmass discussion of single IR
• With two IRs, one of them may be more risky for
  machine performance in expectation of better
  backgrounds and hermeticity
• With single IR configuration, need to put the
  overall performance, reliability and operability
  on the first place
• With one IR the optimal baseline may be neither
  20mr nor 2mr
• Optimization of detector performance while
  minimizing risk
• would be interested in the smallest crossing
  angle that does not compromise downstream E and P
  measurement, does not increase backgrounds, does
  not significantly increase the risk of
  backgrounds, and does not reduce the reliability
  of the machine . This may well be more than 2
  and less than 20 mrad SiD
• Technical possibility to reduce the angle with
  compact BNL quads
• At Nanobeam 2005 in October, presented complete
  14mrad design including IR magnets, extraction
  optics, IR optimization background reduction,
  civil considerations upgrade paths

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Compact quad design developments
8
IR with self shielding quads
9
Tests of short prototype of SC quad
10
Tests of self shielded quad at BNL
Test quad
Rotating coil to measure the field is inside this
brass tube

• The cancellation of the external field with a
  shield coil has been successfully demonstrated in
  a recent test at BNL

11
DID and anti-DID

• Detector Integrated Dipole
• Dipole coils wound on detector solenoid, giving
  small sine-like transverse field
• (anti-)DID allows aligning the detector solenoid
  field lines along the (outgoing) incoming beam
  trajectory
• gt anti-DID effectively zeroes the crossing angle
  for the outgoing beam and pairs, while the
  effective angle for the incoming beam is
  increased 1.5-1.6 times
• Decreased SR, in 14mrad, ease the use of anti-DID

12
Field lines in LDC
Pairs High E Low E
Fringe and internal field of QD0 not included
13
Field lines in LDC with anti-DID
Pairs High E Low E
14
DID/ anti-DID field shape for detectors with TPC

• Field in the central region is flattened with two
  DID coils (short and long) whose currents are
  properly adjusted, to ease TPC calibration
• Suggestion that flattening the field in central
  region would ease TPC calibration came from Dan
  Paterson in discussion with Witold Kozanecki

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anti-DID
Pairs in LDC with DID anti-DID
DID
apertures Incoming Extraction
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Photons into Tracker

• Pair energy into BeamCal is smaller in 14 mrad
  crossing.
• Anti-DID can further reduce the energy to the 2
  mrad crossing level.
• of secondary photons generated in BeamCal is
  also smaller.

photons/BX into Tracker
Takashi Maruyama
17

• From physics points of view, the effect of
  crossing angle is mainly low angle tagging and
  beam background (they are correlated).   AntiDID
  seems to reduce the background for large crossing
  angle case to the same level for the small angle
  crossing case, so the crossing angle is not a
  large factor in physics cases - provided that the
  AntiDID works (including TPC). from Hitoshi
  Yamamoto, November 15, 2005

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(No Transcript)
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Ranking of BDS Configurations

• Rank 1 - directly affecting energy and luminosity
  reach, background, and precision measurements of
  beam properties or a single point failure
• Rank 2 - may affect energy, luminosity and
  background indirectly, e.g. via reliability of
  operation (integrated luminosity)
• Rank 3 - affecting only cost, difficulty of RD
  and difficulty of the design
• Special Rank compatibility with other physics
  programs and upgrades
• (Relative weight of this category should be
  discussed and determined by the whole community)

http//www-project.slac.stanford.edu/ilc/acceldev/
beamdelivery/bds_bcd_acd.htmir_configs_rank
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Rank 1 directly affecting energy and luminosity
reach, background and precision measurements of
beam properties, or a single point failure

• Luminosity reach best 14 and 20mr, worst 2mr
  and head on
• Crab-crossing best head-on, then 2mr, then
  14mr, worst 20mr
• Fast feedback hardware and its integration into
  IR  best 20 and 14mr, then head-on, worst 2mr
• Hermeticity min veto angle best head-on and
  2mr, then 14mr, worst 20mr
• Pairs background best head-on, 2mr and 14mr,
  worst 20mr
• Flexibility of extraction optics and possibility
  of downstream diagnostics best 20 and 14mr,
  then 2mr, worst head-on
• Losses and background conditions in downstream
  diagnostics best 20 and 14mr, then 2mr, worst
  head-on
• Losses in extraction affecting IR background -
  best 20 and 14mr, worst 2mr and head-on

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Rank 2 may affect energy, luminosity and
background indirectly, e.g. via reliability of
operation (integrated luminosity)

• Parasitic crossings best 20,14,2mr, worst
  head-on
• Vertical orbit correction in IP best head on
  and 2mr, then 14mr, worst 20mr
• Tracking, in particular TPC operation and
  calibration best head on and 2mr, worst 14 and
  20mr
• Radiation in solenoid field best head on and
  2mr, then 14mr, worst 20mr
• Extraction line clearance for beamstrahlung
  photons best 20 and 14mr, worst head-on and
  2mrad
• Photon losses in FD, direct sight to vertex
  best 20,14 and head-on, worst 2mr
• Extraction devices affecting MPS best 20,14,
  worst 2mr and head on
• Extraction devices affecting collision stability
  best 20,14 2mr, worst head-on

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Rank 3 affecting only cost, difficulty of rd
and of the design

• Difficulty of final doublet magnets best 20 and
  14mr, then head-on, worst 2mr
• Length of extraction line best 20 and 14mrad,
  worst 2mr and head on
• Difficulty of final doublet integration in
  detector best 20, 14mr and head on, worst 2mr
• Special extraction magnets best 20 and 14, then
  head on, worst 2mr
• Special coils for detector solenoid best 2mr
  and head-on, worst 14 and 20mr

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Special Rank compatibility with other physics
programs and upgrades

• Compatibility with gamma-gamma best 20mr,
  worst head-on, 2mr, 14mr
• Compatibility with e-e- best 20 and 14mr, then
  head-on, worst 2mr
• Compatibility with multi-TeV best 20mr and
  14mr, worst head on and 2mr

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Ongoing work and discussion (rank 1)

• Luminosity reach best 14 and 20mr, worst 2mr
  and head on
• In 2mr and head-on, to extract the disrupted
  beam, it is bent by a separator, rf kicker or
  field off-center of the final quadrupole. Large
  energy spread of disrupted beam causes beam
  losses and limits the luminosity reach by more
  than a factor of two in comparison with 20 and
  14mr
• Luminosity reach for considered versions
• 20/14mr all parameter sets work except 1TeV High
  Lumi (alternative 1TeV High L works OK)
• 2mr problems with Large Y, Low P, High Lum for
  500GeV CM, Large Y, Low P, High Lum, High Lum
  Alternative 1TeV CM
• head-on does not work for Low Q (parasitic
  crossings), other sets not evaluated, issues
  likely for low P and high L
• Discuss with detector community the relative
  merits of parameter sets with larger
  beamstrahlung and disruption

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Ongoing work and discussion (rank 1)

• Crab-crossing best head-on, then 2mr, then
  14mr, worst 20mr
• No need for crab cavity in head-on
• Small to moderate luminosity loss (5, 10 or 30
  for low Q, nominal or large sigma Y parameters)
  in 2mr without crab cavity
• Crab cavity is essential for 14 or 20mr.
  Luminosity loss without crab cavity is 60-75-90
  in 14mr and 75-85-95 in 20mr (for low Q, nominal
  or large sigma Y parameters)
• Warm transverse cavities are in use now, SC
  cavities are not yet. A deflecting SC CKM cavity
  is being built at FNAL. Crab cavity system can be
  built and experimentally verified during TDR
  phase, before start of ILC operation.

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Ongoing work and discussion (rank 1)

• Fast feedback hardware and its integration into
  IR  best 20 and 14mr, then head-on, worst 2mr
• In 20 and 14mr, feedback BPMs and kickers do not
  see other beam
• In head-on with shared aperture, BPM sees other
  beam and need to be directional, there may be
  losses of low energy beam tail on the kicker.
• In 2mrad, the feedback BPM has to be placed in
  front of FD, where disrupted beam envelope is
  still small, there is offset of outgoing beam in
  the BPM, the kicker should be large aperture,
  there are potential losses on the kicker.
• Performance of IP feedback, with all effects of
  beam losses included, is difficult to guarantee
  from simulations (which have advanced
  significantly) or from simplified beam tests.
  Eventual verification cannot be done before start
  of ILC operation.

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Summary plan for the next year

• Since Snowmass, a lot of progress in all areas
• Next year, will continue design,
• Choose IR configuration for single IR case
• Consider in more details optimization for
  push-pull
• Consider upgrade paths to two IRs in more details
• Cost the baseline and single IR alternative
• Consider possibilities to reduce the cost further
• Consider optimization of 500GeV stage while
  keeping 1TeV reach