Summary of Recent work on 750 x 750 GeV Collider

1
Summary of Recent work on 750 - x 750 GeV Collider

• C. Johnstone
• LEMC Workshop
• June 8-12, 2009

2
Johnstone Design Overview

• 750 GeV
• Arc FMC module 5.3T dipole fields
• Fits circumference, would surround present
  Tevatron tunnel
• Direct piping of existing electrical, water,
  cryo services
• Negative momentum compaction
• Can be isochronous up to 3rd order in ?
• Peak beta functions are half of equivalent FODO
  cell
• 40 smaller beam size in arcs
• Lower fields allow potential for increased
  collider energy
• Potentially up to 1 x 1 TeV
• Asymmetric ? IR straight design ?x,y20, 5 mm
• IR quads 10T
• 2m IP to first CF magnet
• Non-zero dispersion in , vertically focusing,
  local chromatic correction in IR

3

• LESS THAN 0.1 of the energy from muon decay
  products can be deposited on the SC coils or its
  surrounding support structure. Previous
  solutions for the heating problem include
• Thick, 65 mm tungsten radiation shield to reduce
  the deposited energy by 103 beam size 5 ? beam
  zize 20 mm
• Separate the coils across the midplane
• Active (background sweep dipoles) and passive
  (tungsten collimators) inserted between the final
  focus quadrupoles to shadow/shield the SC.

4
New Considerations

• CF magnets
• Open midplane
• Discrete dipole/quad coils
• Corrector set of coils
• continuous field coverage no nonmagnetic
  straights gt 0.5 m
• Exploit azimuthal dependence of background
  distributions

5
Previous Ring Structures General Information

• IR final focus aberration correction section
• Relatively compact 425 m
• Peak Beta function 43 km
• Linear chromaticity -500 to -700
• Arcs
• Flexible Momentum compaction, 70 m long
• Packing fraction comparable to FODO
• Momentum compaction corrected up to 3rd order
• Peak beta function, 110 m
• Scraping and utility section
• Presently a simple representative R matrix
• Ring
• 1 km radius for 750 x 750 GeV
• 2-fold symmetric
• 64 arc modules

6
Study of IR CCS optimization

• Studied beating of two IR configuration, unity R
  matrix used for arcsutility straights
• Added phase adjustment between two IRs not
  pretty but is powerful and invisible in terms of
  nonlinearities
• Half integer tune is optimal for
  sextupole-dominated optics

7
Past work conclusions

• Tune optimiztion
• DA Sextupole pattern -I pairs always, unbroken
  by ring tune or multiple IRs
• Chromatic correction quarter integer between IRs
• Not reconcilable

8
New Approach to IR design

• collider ring defines performance of upstream
  systems
• Asymmetric ?s at IP- very likely asymmetric
  emittances which will allow new cooling schemes.
• Small vertical apertures reduce dependence of IR
  on highly nonlinear fringe fields
• Small vertical beam size _at_IR, factor of 7 or so
  difference in chromaticities
• CF magnet first dipole quadrupole achieves
  immediate focusing of vertical plane (probably
  all IR quads CF continuous background sweeping)

9
Continued

• Chromatic correction in horizontal plane _at_source
  same in dipole first approach.
• Next sextupole 180 away in 0-dispersion region
  no chromatic terms, impacts geometric aberrations
  only
• Octupoles need to be added as done in Higgs
  optimization for kinematical effects

10
New IR, under development
11
Summary / Recommendations

• Continuous magnetic field CF magnets everywhere?
• Simultaneous geometric chromatic aberrations a
  problem mitigate one or the other in IR design
  independent knobs
• Exploit open midplane both vertically and
  horizontally study azimuthal dependence of
  backgrounds
• Asymmetric ?s, reduce vertical aperture and
  fringe-field dependencies in IR
• Lattice repository all rings modeled
  consistently in a high-order code including
  kinematical and quadrupole fringe field effects
  - COSY or ZGOUBI

12
(No Transcript)
13
Progress with MC Lattice Design
Y. Alexahin, E. Gianfelice-Wendt (FNAL APC)
4th Low Emittance Muon Collider Workshop
Fermilab, June 8-12,
2009
14
(No Transcript)
15
Stages of MC lattice design - where are we now?
3
? Generation of new ideas, conceptual designs for
various options ? Comparison of different
schemes, choice of the baseline ? Detailed
lattice design with tuning and correction knobs
? Dynamic aperture studies with magnet
nonlinearities, misalignments and their
correction ? Transient beam-beam effect
compensation ? Coherent instabilities analysis
MC Lattice Update - Y. Alexahin
4th LEMC workshop,
Fermilab, June 09, 2009
16
(No Transcript)
17
Approaches to chromatic correction
5
? with sextupole families in the arcs (classic
method, global correction) ? with sextupoles
in special CC sections (local correction, but
the locale is out of IR). Allows to organize the
sextupoles into non-interleaved pairs with phase
advances between the sextupoles in a pair ?.
This greatly improves DA. - K. Oide and C.
Johnstone A. Garren designs of 1996 ? local
with sextupoles right in IR - saves space, less
prone to errors but at the price of stronger
higher-order effects - dispersion generated by
dipoles between FF quads (or even in front of
them) - Y.A. E.Gianfelice-Wendt - dipoles
outside IR create dispersion antisymmetric w.r.t.
IP - P.Raimondi F.Zimmermann (revisited by A.
Netepenko)
MC Lattice Update - Y. Alexahin
4th LEMC workshop,
Fermilab, June 09, 2009
18
(No Transcript)
19
Dipole First IR Design Option - a Quick Fix
10
Dipole before the first quad creates larger
dispersion in IR -gt weaker sextupoles It may also
help to protect the detector from backgrounds
decay electrons and Bethe-Heitler muons
MC Lattice Update - Y. Alexahin
4th LEMC workshop,
Fermilab, June 09, 2009
20
Upgrade Lattice Properties
11

• Dynamic momentum acceptance is now 0.63,
• it can be further increased by
• stronger octupoles to reduce Qx
• introducing decapoles to correct Qx

MC Lattice Update - Y. Alexahin
4th LEMC workshop,
Fermilab, June 09, 2009
21
Summary Outlook - MCD Workshop _at_ JLab
13
How it will withstand beam-beam interaction?
(Chuck)
Dipole first optics can provide necessary DA
for the medium-emittance option. However, for the
high-emittance option as well as for the
long-term beam stability new ideas are
necessary. Our next design - combination of the
two approaches chromatic correction in one plane
with IR sextupoles and with a -I pair of
sextupoles in the other plane further downstream
from IP. Hopefully this will permit to avoid
using dipole near IP
MC Lattice Update - Y. Alexahin
4th LEMC workshop,
Fermilab, June 09, 2009
22
Elianas New Synthetic Design
14
? 1 IP with ?? 1cm ? quad first at 6.5m ?
dipoles fill all available space ? no octupoles
chromatic correction sextupoles
MC Lattice Update - Y. Alexahin
4th LEMC workshop,
Fermilab, June 09, 2009
23
Elianas New Synthetic Design
15
Huge DA - sufficient for ??N100 microns!
MC Lattice Update - Y. Alexahin
4th LEMC workshop,
Fermilab, June 09, 2009
24
Problem with momentum compaction
17
? The ?p? problem can be solved with dedicated
sextupoles (at the expense of DA) ? Eliana tried
a number of arc cell designs to minimize ?p?,
the most promising being
MC Lattice Update - Y. Alexahin
4th LEMC workshop,
Fermilab, June 09, 2009
25
Basic parameters
18
Elianas new Dipole first Beam energy,
GeV 750 750 Number of IPs 1 2 Circumference,
km 3.6 3.1 ?, cm 1 1 ?_max,
km 64 32 Momentum compaction 7.7e-5 5.5e-5 Mom
entum acceptance, 0.96 0.63 Tunes 26.45/24.4
5 42.1/41.1 DA, ? for ?25?m 7 3 -------------
--------------------------------------------------
---------------- ) static acceptance with no RF
MC Lattice Update - Y. Alexahin
4th LEMC workshop,
Fermilab, June 09, 2009
26
Summary Outlook
19
? Elianas new design is promising to satisfy all
requirements, problem with momentum compaction is
solvable ? It will profit from dipole first as
well - study of its effect on detector
backgrounds will start soon ? Alternative schemes
for obtaining large dispersion at IR are being
studied (Alexandr Netepenko - next talk) ? Effect
of plasma beam-beam compensation on detector
backgrounds should be studied ? ? If forbidding -
return to scheme with Chromatic Correction
Sections (or Blocks) ? Consider possiblity to
move quads closer to IP to reduce chromatic
perturbations (R.Palmer) ? Study if FF quad
shielding from inside is really necessary
MC Lattice Update - Y. Alexahin
4th LEMC workshop,
Fermilab, June 09, 2009
27
A. Netepenko Asymmetric Dispersion Function

• Initially proposed by P. Raimondi and F.
  Zimmerman
• Positive dispersion on one side of IP and
  negative on other side
• Makes the IR more isochronous
• Asymmetric reflection cancels some higher-order
  terms locally
• apologies I was unable to download pictures
  from the talk.