Status of studies for the transfer line between

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Status of studies for the transfer line between
Linac4 and the PS booster (South Hall project)
Purpose Transport the beam from Linac4 to the
booster and meet PSB injection requirements so
that beam can be captured in the ring with small
losses. Exact beam parameters (transverse and
longitudinal) for matching into PSB still to be
specified.

• Starting point _at_ Linac4 output
• E160MeV, f352 MHz, I65mA
• e rms transv. 0.28 p mm mrad
• e rms long. 0.174 deg MeV
• Rms phase half length 2.61 deg
  Rms
  energy half width 290 keV
• 
  ax -2.69
  bx 5.87 m ay 1.05
  by 1.73 m az 0.0135 bz 9
  deg/MeV

Booster injection Transverse matching as per 50
MeV injection ax 0. bx 2m ay0 by
4.22 m Longitudinal matching 200keV
(keeping same RF in booster)
Technique initial Trace3D design followed by
multi-particle simulations (PATH, later
cross-check with IMPACT) using beam distribution
from Linac4 output.
G. Bellodi - Linac4 TDC meeting 04/04/06
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Design approach

• Three main building blocks
• FODO channel for transport in the straight
  segments, to provide regular transverse focusing
  of the beam

• Q l 600 mm
• Q f 1.5 T/m
• L7.2 m
• s0 90o
• mm bore diameter

QF
QD
QF
QD
7.2 m
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Energy spread increase due to space charge
saturates after 18 m
Need to reduce energy spread of the bunch to lt200
keV with one or more debuncher cavities. D Phi lt
50 deg to avoid RF nonlinearities
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2) Buncher cavities
First one to be positioned at a distance of 20-30
m from Linac4 output (see plot) Voltage
required V DW/cos(Df) 900 keV/cos(40o)1.2
MV Solution suggested by M.Vretenar is to use
4-cell cavities
Max 0.3 MV per cell 1.2 MV total Power limit
80kW
1m
One cavity (_at_ full voltage) would probably just
be sufficient for debunching, but second one
(though at much lower voltage) would help to keep
a larger margin to play with in meeting injection
requirements on energy spread. Studied at 65mA,
in first approximation no strong sensitivity on
beam current. Keep bore diameter lt40 mm
Focus beam in the cavity
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3) Bends

• Straight layout not feasible (not a green-field
  construction) -gt need to add bendings.
• Two problems introduced
• Dispersion
• Achromatic solution of splitting the
  dipoles into two magnets and embedding them into
  a FODO period, then using 2 internal quads to
  match for Dx0 Dx0.
• 2) H- ion stripping
• particle moving through magnetic field B
  will experience an electric field that can cause
  stripping
• stripped 100 1-exp(-t/t)
  t(B)7.96E-6/(cbgB)exp(4.26E9/(cbgB))
• Calculated for q60o, r2m,
  B(T)1T --? losseslt0.01
• Aim to stay below magnetic fields
  of 1T in dipoles.

Q
q/2
Q
Q
Q
q/2
L 7.2m
Match for
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Latest scheme
achromats
LINAC2
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Summary

• From a preliminary study of the transport line
  wed need
• 32 quadrupoles
• 2 rf cavities (_at_ 1.2MV and 0.4 MV
  approx.)
• 3 bendings (45o, 22o, 65o split in two
  halves of q/2)
• FODO system for transporting and matching the
  beam can be done with standard quadrupoles for a
  wide range of currents. Next step is to couple
  quadrupoles on same power supply (cost driver for
  the line).
• Couple pair of dipoles on a single power supply.
• Total length is 110m (of which 32.5m minus
  elements lengths - in PS tunnel would need
  Mu-metal magnetic shielding).
• Civil engineering build 2 tunnels (wide enough
  to fit quadrupoles inside) through PS/Linac4
  shielding and PS/LEIR injection line, perhaps
  widen passage at the end of Linac3 building (not
  too painful!)
• RP initial study (location independent) based
  on 1 W/m level losses unif. distributed-
  estimated at 230cm the minimum shielding
  thickness required for a Simple Controlled area.
  Revise for current layout and location (close
  proximity with Linac3/LEIR ? strengthen existing
  protection?)

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Next steps

1. Refine layout, try longer FODO periods to
   economise on number of elements.
2. More extensive and accurate beam dynamics
   studies with multiparticle simulations (using
   output beam distribution from Linac4)
3. Finalise exact layout, introduce steerers and
   diagnostics
4. Liaise with civil engineering to have an exact
   fit of the proposed layout in the context of
   existing structures and lines.
5. Radioprotection issues?
6. Final costing and TDR