ION ACCUMULATION IN LEIR

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ION ACCUMULATION IN LEIR
Presented by M. CHANEL
ECOOL2001-Bad Honef
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CONTENTS

• LEAD on LEAD
• General view
• Linac3
• Injection
• Cooling
• Lattice and machine elements
• Vacuum
• PS and further
• Other ions
• Planning
• Summary

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GENERAL SCHEME
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Performance needed

• 7 107 Lead ions/bunch in LHC at 2.7 TeV/n in a
  normalised emittance of 1.5 mm(bg s2/b). ( quench
  limit and central detector limit)
• Overall transfer efficiency of 30,
• elt1.2 mm at the exit of SPS,
• elt1 mm at the entrance of SPS after final
  stripping,
• elt0.7 mm at the entrance of PS.
• This means 4 bunches in Leir with 2.3 108
  ions/bunch. Or a total of 0.9 109 ions in 1, 2
  or 4 bunches?

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Stacking tests of lead ions
requested
Sourceefficiency
Lossescharge state
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LINAC3

• Improved afterglow pulsed ECR source (450ms pulse
  length but increased current from 100mA to 300mA
  Lead 27 Leir uses 200 ms max).
• Accelerate to 4.2 MeV/n, b0.0945
• Add a cavity to ramp momentum by 1
• Stripping afterwards and use of Lead 54 (main
  contents Lead53 but too much recombination rate
  with electrons of e-cooler )
• Pulsing from up to 10Hz.

Collaboration Catania, Grenobles, Cern, GSI
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LEIR

• Combined H/V/P multiturn injection inclined
  septum momentum variation of incoming beam such
  the injection orbit (D dp/pbump) remains the
  same during injection. 50 injection efficiency
  reachable.
• Cool and stack the freshly injected beam by
  electron cooling in 400 ms max.
• 4 injection-cooling-stacking cycles should be
  enough.
• Acceleration and ejection (h2) at T71MeV/n
  energy choice is a compromise between the limit
  of incoherent tune shift in PS, the time between
  bunches for ejection kicker and stacking time in
  SPS/LHC.

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LEIR Injection

• Combined injection gives lower et (better cooling
  time) compared to normal multiturn but increases
  mom. spread (good long. cool.).
• Combined injection implies large D and D/??5
  (D10, b3).

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X-Y plane105 turns tracked
Cooled beam
E-SEPTUM
New beam from linac D0
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• X-Y plane after 100 turns
• 75 injected

• x and y and momentum projected distributions

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Cooling and Stacking

• Electron cooling theory gives

• where q is the relative difference in angle
  between the ions and electrons qi?(?/?)
• the parameter hecool Lcooler/Lmachine
• and Ie is the electron current.
• A and Q atom mass and charge state

• Large b desirable but ion beam size should remain
  smaller then e-beam size mind to e-beam space
  charge.optimum around b5m

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Lattice

• Good for injection and coolingstill 2 periods
• tune(1.8,2.7)
• longitudinal acceptance reduced to dp/p 1
• 5 quad families, more flexible.

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Electron cooling
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GUN
Dipole
Toroïd
DRIFT
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LEIR cycle for LEAD ions
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OTHERS

• With an electron beam of 200mA, the cooling rate
  is sufficient to counteract the IBS growth rate
  and get the emittances wanted.
• The beam will be maintained stable mainly during
  cooling(coasting beam) by a 100MHz bandwidth
  transverse active feedback.

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A word on vacuum

• During the tests in 1997, the Lear vacuum was
  good (5E-12T without beam) but the lost lead
  ions (e-ion recombination..lead 54 or res. gas
  charge exchange or..) degas the chamber walls.
  One lead ion releases 105 molecules!!!!
• At end of linac3, tests of different vacuum
  chamber treatment are under way.
• Hope outgassing can be reduced by appropriate
  treatment of the vacuum chamber.
• Already known when ions are lost perpendicularly
  to walls, outgassing is decreased.

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PS(preliminary)

• Inject (change/modif. septum-kicker) and
  accelerate on h16 up to T1.5 GeV/n
• h16?14?10 , split 2b. to 4 bunches and finally
  h20 ?17
• h17 is chosen to have 125ns b. separation at
  flatop in LHC and it is compatible at 4.25GeV/n
  with 200MHz RF system in SPS.
• Acceleration to 4.25 GeV/u, cp/Q19.7 GeV/charge.
• Stripping in TT2. Change of TT2 line to have a
  low beta at stripper.

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TT2(from PS to SPS)

• At stripper bh,v20m?5m, D-1m
• Blow-up reduced by a factor 4 compared to
  old(normal)optic.needs MD for SPS matching.
  De0.2mm after re-matching in SPS?.
• Need of 4 quad, 6 power supplies building?.

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Other ions
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Planning
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Summary

• Accumulation schemes for different kind of ions
  are well advanced
• Electron cooling of heavy ions is defined.
• Space charge limits both in LEAR and PS together
  with cooling/filling time are the main
  limitations especially for light ions.
• Vacuum degradation due to losses is a challenge .
• IBS and conservation of high beam density is
  another challenge.
• Blow-up due to stripping improved in TT2
• Planning established.
• All technical systems are being specified.

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PSB-PS?

• PSB for light ions(He,O,Ar?) with a source of
  1mAe, cp/Q310 MeV/c/ch ?15, 3-4turns injection
  it could be possible even using the 4 rings(
  change filling scheme in LHC???)