Beam Delivery Systems

1
Beam Delivery Systems

• Are we headed in the right direction to produce a
  CDR by the Spring of 2001
• Are we configured correctly and focused on the
  right things

2
Cost

• In 1996 ZDR Cost estimate BDS was 5 of total
  project cost
• CollimationBig Bends 72 M
• Final Focus, IR, Dumps 135 M
• Total Beam Delivery IR 207 M
• Total Project 4338 M
• We will not pay much attention to cost or
  construction schedules in this review

3
To have a credible CDR we must be able to
convince ourselves and the physics community that

• we can take a design emittance beam from the
  linac and de-magnify it to 3 nm
• we can get two independent beams to collide and
  that we can maintain those collisions
• that there is sufficient understanding ,
  protection, controls, and diagnostics so that the
  high power beams do not destroy the beam line nor
  cause unacceptable backgrounds
• that there is sufficient understanding of the
  luminosity dependent backgrounds generated at the
  IP and an adequate masking design

4
Why might it be difficult to convince a skeptic?

• It has taken the SLC 10 years to (almost) reach
  design luminosity
• While much has been learned, NLC breaks new
  ground in many areas

5
What did we have in the ZDR?

• Collimation System
• very long to provide passive protection for
  spoilers collimators
• severe optics
• chromatic problems
• tight tolerances
• octupoles
• wakefield problems
• very difficult to calculate for flat collimators
• rectangular apertures

6
What did we have in the ZDR? (continued)

• IP Switch, Big Bend, and the Final Focus
• 10 mrad bend
• Two IPs
• 40 m transverse separation
• symmetrically located in z
• 2 m L design
• Well studied optics
• Jitter drift tolerances on individual elements
• 0.5 lt Ecm lt 1.5 TeV, but magnets need transverse
  displacement
• Extraction and Diagnostic Line
• impossible REC quads 2m from IP
• common e and g dump
• chicane to separate e and g lines for diagnostics

7
What did we have in the ZDR? (continued)

• IR design
• Achieve 1nm stability via
• Optical anchor concept
• Compact detector
• Simple 100-150 mrad dead cone masking scheme
• based on 2 Tesla field and the ee- pair pt
  distribution
• Good muon background calculations
• Four 9 m long tunnel filling spoiler magnets
• lt Entire beam (1012 e-) could strike collimator
  make lt 1 m _at_ detector
• Good ee- and SR background calculations and
  detector simulations
• lt 10 hits/mm2/train _at_ r 1 cm in 4 Tesla

8
Where are we today?

• Collimation System
• Collimation group formed and considered novel
  schemes
• lasers
• octupoles
• post-bunch compressor / pre-linac
• intra-linac
• post-linac
• Reduce requirement of collimator survival and
  redesign a conventional scraper system
• Tors talk
• Wakefield tests planned for near future

9
Where are we today? (continued)

• IP Switch, Big Bend, and the Final Focus
• First real design of IP switch
• pay attention to spatial conflicts between the
  two IP beamlines
• 300 m IP separation in z
• Magnets redesigned to
• reduce number of magnet classes
• increase vacuum bore and minimize changes in bore
• Final quads redesigned to reduce pole tip fields
  and increase beam stay clears
• change Q1 A B for 350 lt Ecm lt 750 GeV and 750 lt
  Ecm lt 1000 GeV
• Well studied optics
• No longer need transverse displacement to upgrade
  beam energy to 1 TeV
• Feedback, stability, and tolerance studies just
  begun

10
Where are we today? (continued)

• Extraction and Diagnostic Line
• ZDR optics analyzed and found to produce
  unacceptable beam loss
• Redesign begun
• move first quads further away from the IP
• improve beam loss

11
IR status today?

• Small spots Many belts suspenders
• Optical anchor RD well developed (Mike Woods)
• 1 m interferometer
• piezo-mover vs. interferometer calibrations
• 10 m interferometer
• 100 kg quad simulator
• Goal IR mock-up
• Re-open question of non-optical stabilization
  devices (Joe Frisch)
• geophones
• accelerometers
• Very fast IP feedback (John Fox)
• Bunch spacing 1.4 ns -gt 2.8 ns
• Use head of bunch to correct tail
• Goal 50 ns to correct following bunches of 244
  ns long train
• RD planned developed
• looking for student(s)
• FFTB Run 1 70 nm spots, 40 nm jitter

12
IR status today? (continued)

• Engineering
• Nothing new since Snowmass 96
• Basic IR parameters
• Ideally, study the engineering, optics, and
  backgrounds for
• L 1, 2, 3 m
• Large and Small detectors (B_solenoid)
• Crossing angle ?c
• Q1 technology choice REC, SC, Hybrid, Normal
• Currently L 2m, B_s 4 Tesla, ?c 20 mrad,
  REC Q1
• Crossing Angle requires RF Crab cavity
• stability requirements analyzed and thought not
  to be a show stopper
• RD program to verify this developed

13
IR status today? (continued)

• Basic IR parameters (continued)
• Vertical deflection of beams due to ?c and Bs
• steering 45 mm deflection
• dispersion 135 nm added to vertical spot size
• Need one of
• Flux exclusion solenoid around Q1, or
• 800 G-m steering corrector after Q1, or
• Tuning with upstream skew-quad system
• Relative merits of each choice need study
• B_s apparently not constrained to within x2
• Desirable to coalesce JLC/NLC choices
• L 2 m
• ?c 8 mrad
• Iron Q1 system with a flux exclusion solenoid
• B_solenoid 2 T

14
IR status today? (continued)

• Backgrounds
• Source Calculations
• Beam - Beam incoherent pairs
• CAIN - Guinea-Pig code comparison
• Agree within x2
• Differences due to internal technical cuts
• SR, Muons
• Not yet redone for the newest lattice
• In principle, no problem
• Detector Simulations
• EGS -gt GEANT3 -gt GEANT4
• GEANT3
• Beam-Beam pairs e, g, n backgrounds as function
  of radius
• SR e, g, n backgrounds as function of radius
• calculation of n from 500 GeV e- hitting main
  dump just begun
• MUCARLO
• Opportunities for improvement, cost savings,
  agreement with JLC

15
IR status today? (continued)

• Extraction Line Diagnostics
• No one working in this area
• Tools to unfold beamstrahlung spectra
• Luminosity monitors
• Instrumented masks
• Energy spectrometers
• Polarimeters
• Radiative Bhabha monitors
• Beamstrahlung monitors

16
General Comments

• Unless there is a change of direction we will
  continue to act on a best efforts basis each
  individual working in their area of expertise
  until a given deadline. Then there will be a
  brain-dump and the machine status will be written
  up with a positive spin, just like for the ZDR.
• Why?
• Too few physicists engineers devoted to this
  part of the project
• Effort diluted in an attempt to broadly cover
  machine, ignoring the fact that our main effort
  is to investigate the design parameter space
  sufficiently to believe that we have produced the
  best design possible.
• Inability to articulate what is critical and to
  bring what resources we have to bear on the
  problem.

17
People(red full time beam delivery)

• Engineering
• Leif Eriksson
• Andy Ringwall
• Dieter Walz
• Other Accelerator Design Issues
• Yuri Nosochkov
• Peter Tenenbaum
• Kathy Thompson
• Tor Raubenheimer
• Collimation
• Joe Frisch
• Rainer Pitthan
• Frank Zimmermann

• IR Design
• Tom Markiewicz
• Takashi Maruyama
• Mike Woods
• Tracy Usher
• In the bullpen /or consultants
• Gordon Bowden
• John Fox
• Dick Helm
• Stan Hertzbach
• Nan Phinney
• Sayed Rokni
• Marc Ross
• Tim Slaton

18
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19
What do we really need in the CDR?

• Evidence that we have sufficiently analyzed the
  parameter space that defines the overall
  footprint of the beam delivery system
• Explain the parameter space or design options
• L, ?c, NLC vs. JLC style final focus, NLC vs.
  JLC collimation, sacrificial or indestructible
  collimators, active or passive protection, etc.
• Justify choice of design MPS, Collimation,
  IP/BB/FF, Dump
• describe design and its tolerances and
  performance _at_ 500 GeV and 1 TeV
• Specify tuning, feedback, and diagnostic systems
• De-magnification assured (FFTB) but can we get
  and maintain collisions given tolerances
• Monte Carlo - like simulation results which
  incorporate feedback, tolerances, drifts and
  jitter and which indicate the performance specs
  or aberration limits for each part of the system
• compare to alternate schemes
• Explain what changes to design might be possible
  with more work but within the footprint
• e.g. more collimation _at_ 1.5 TeV
• e.g. range of allowable L

20
What do we really need in the CDR?

• Engineering
• Identification and prototype results of items
  with high technical risk
• Identification of problem areas arising because
  of the scale of project
• Reliability
• Schedule
• Fabrication
• QC
• Installation
• Cost estimate
• Large contingency allowable
• Boilerplate
• Parts counts
• Engineering specs

21
What do we really need in the CDR?

• Description of IR parameter space
• L, ?c, Q1 technology choice, Flux excluder or
  not, tune-ability, vibrations, mass, stiffness,
  Solenoid field strength
• Justify choices and describe performance
• Put to bed the IR stability question
• Build an adequately engineered full scale
  prototype of IR
• Present experimental evidence on
• the amplification (or lack) of ground motion and
  culturally induced jitter
• the achievable jitter reduction as a function of
  frequency
• relative to local bedrock
• absolute
• Hardware simulation of a low latency pickup and
  correction scheme
• FFTB2 measurement of 40 nm spots desirable but
  expensive in terms of effort

22
What do we really need in the CDR?

• Description of detector backgrounds from all
  sources and optimization of shielding
• Easier to calculate sources
• Beam-beam pairs
• SR photons
• Muons
• Harder to calculate sources
• Jets from gg
• Lost particles, energy tails, .
• Design and simulate a minimal set of dump line
  instruments
• required to tune luminosity
• required to extract physics

23
What post-CDR study can go on?

• Design can be tweaked until the engineering
  contracts are bid, but changes that do lengthen
  the tunnel footprint will probably be strongly
  discouraged

24
Conclusions

• Main concern is that important parts the BD
  design remain while ULM has taken an engineering
  mind-set. Will BD work or not? Would like to
  see lots of convincing calculations and
  experimental results.
• that not enough options have been investigated
• current lattice needs lots more attention
• requisite RD may be happening at too slow a rate
  to allow for its results to be included in the
  final design
• e.g. current tunnel depth is 30 stability may
  require gt300
• large implication to project design
• Please advice ULM to find resources to address
  these problems quickly if Spring 2001 CDR
  deadline is to be met
• people
• money (to buy/rent people)
• beam time (Coll. Tests, FFTB?, )