ION ACCUMULATION IN LEIR

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ION ACCUMULATION IN LEIR
Presented by M. CHANEL
THIS CONCERNS ONLY LEIR
27 August 2001-PS-MB Technical Seminar
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CONTENTS

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

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LEAD Performance needed

• 7 107 Lead ions/bunch in LHC at 2.7 TeV/n in a
  normalised emittance of 1.5 mm(bg s2/bh,v). (
  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 1,2,4
  bunches?

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GENERAL SCHEME
LHC.LEAD.PUB
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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).
• Accelerate to 4.2 MeV/n, b0.0945
• Add a cavity to ramp momentum up to 1
• Stripping afterwards and use of Lead 54
  (Slightly less intensity than for Lead53, but
  acceptable lifetime with electrons of the
  electron cooler )
• Pulsing from 1 Hz up to 10 Hz ( 5 Hz probably
  sufficient).

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(75 on paper).
• Cool and stack the freshly injected beam by
  electron cooling in 400 ms max.
• 4 injection-cooling-stacking cycles should be
  enough (timelt1.6s).
• 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 the ejection kicker, the min RF
  frequency in PS and the 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/??
  5m1/2 (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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LEIR INJECTION LINE
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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 and mind the effect of
  the 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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RF
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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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LEIR EJECTION TO PS
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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 4.25GeV/n, cp/Q20. GeV/c/charge.
• Stripping in TT2. Change of TT2 line to have a
  low beta at stripper.

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TT2(from PS to SPS, has to be changed)

• 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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LIMITS OF THE ACTUAL SCHEME

• Specifs for LHC-LEAD not achievable by SPS ( tune
  shift too high, el growing by IBS too large)
• SPS tune shift acceptable if cp/QPS risen to 26
  GeV/c/Q but IBS still not acceptable (RF 200 MHz
  ? 80MHz?). No implication on LEIR as it is
  proposed.
• Specifs for light ions not achievable and strong
  implications on LEIR. To harmonise tune shifts
  along the chain ( LEIR,PS-0.25, SPS-0.07)
• a simple way to increase limit in the SPS is
• increase extraction energy in PS.(RF change in
  SPS?)
• strip ions completely at the exit of LINAC3 then
  RF frequency higher in LEIR (max from 3.5 MHz to
  6 MHz).
• increase extraction energy in LEIR to increase
  limit in PS but then limit at low energy in LEIR.
• It is then mandatory to review the overall chain.

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Other ions

• PS-SPS transfer 26GVSPS RF 200MHz (IBS?)
• always 4 bunches from PS to SPS

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Different Systems

• Inj./Ej. Line magnet spec. (not detailed) 8
  QTWs, 2 BHN 1.7 and 0.4 Tm2 cores, 2-4 DVN
  instrumentation. One inclined SEH , one pulsed
  magnetic septum, and pulsed power supplies. All
  others recup. But some power supplies
  modifications or renewal(kickers, bumpers)
• Electron cooling- specifs known.Novosibirsk? 2
  DHVs Old quad power supplies for solenoids.
• Machine magnets- all recuperated (even 4 reserve
  quad added ) but 6 big powers supplies (BHN5
  quads families) . renewal of controls.
• RF-2 cavities partly specified- Japanese cores
• Machine instrumentation- specifs knownadjust.

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Different Systems (suite)

• MechanicsAll elements position known
• Vacuum not completely known. This is the weakest
  point of the study but an important point for
  the machine.
• Controls ok but not detailed.
• Subsystems like safety, water cooling..

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LEIR COST (and only LEIR)
/specifications/cost-recapitule/cost..xls
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Why a difference with the original price (1994)
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Staffing (from PS-conclave in FV)
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Planning
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Summary

• Accumulation schemes for different kind of ions
  are well advanced but to finalise SPS must be
  studied.
• Electron cooling of heavy ions is defined.
• Space charge limits both in LEAR and PS are
  harmonised. Space charge 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.
• Rough planning established, cost known within
  10.
• All technical systems are specified.

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OUTLOOK

• REVIEW OF COMPLETE CHAIN
• September DESIGN report (readable draft end of
  sept.).
• Start detailed planning,
• Final specifications end of this year.

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TUNE SHIFT