LHC (SSC)

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LHC (SSC)

• Byung Yunn
• CASA

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Parameters

• Type Synchrotron
• Circumference 26.659 (82.944) km
• Proton energy 7.7 (20) TeV
• Bunch length 7.5 (6 to 7.5) cm
• Energy spread 1.05e-4 (0.5e-4)
• Transverse emittance 3.75 (1.0) µm
• Longitudinal emittance 2.5 (0.233) eV-s

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continued

• Protons per bunch 1.0e11 (7.3e9)
• Average beam current 850 (73) mA
• Number of bunches 4725 (17100)
• RF frequency 400.8 (374.74) MHz
• RF voltage 16 (20) MV
• Synchrotron tune 0.00157 (0.0019)
• Momentum compaction 2.94e-4 (2.23e-4)

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continued

• Nominal full crossing angle 200 (75) µrad
• Bunch spacing 15 (16) ns
• Beta star 50 (50) cm
• Beam-beam tune shift 0.0032 (0.00084)
• Luminosity (/cm2-s ) 1.65e34 (1.0e33)
• Number of interaction points 3 (4)
• Synchrotron radiation power (per beam) 9.1 (9.1)
  kw

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Injectors (LHC)

• 50 MeV proton linac (180 mA for 7 µs), injected
  into 4 PS booster rings
• PS booster accelerated in one bunch up to 1.4
  GeV, PS accepts eight 200 ns long bunches
• 26 GeV PS (1/11 of SPS) debunched and rebunched
  at 26 GeV to 1.0e11 protons per bunch (emittance
  3 µm, bunch length 9 ns)
• 450 GeV SPS (7/27 of LHC) 36 SPS beam pulses to
  fill one LHC channel.

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Injectors (SSC)

• 600 MeV H- linac 125 m, RF Freq 49.5 MHz
  (RFQ), 445 MHz (DTL), 1336 MHz (SCL)
• 8 GeV LEB 250 m, RF Freq 49.5-62.0 MHz
• 100 GeV MEB 1.9 km, RF Freq 62.5 MHz
• 1 TeV HEB (Superconducting) 6 km, RF Freq 62.5
  MHz
• Average current (mA) 3.9 (Linac), 99 (LEB), 92
  (MEB), 87 (HEB)

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Collider ring (LHC)

• Built on top (1.21 m) of LEP and has eightfold
  symmetry
• Two beam channels in the same magnet
• 10 Tesla dipole field (4 to 6 Tesla available)
• Can be used to collide ions
• Number of arcs 8
• Number of interaction regions 8 (3 collision and
  2 utility)

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Collider ring (SSC)

• Two rings separated vertically (0.7 m)
• Dipole field 6.6 T
• Quad in arcs 212 T/m
• Interaction regions (IR) are arranged in 2
  clusters (East and West) for cost effectiveness
• 4 IRs in each cluster and each IR is 2.4 km long
• Clusters are joined by arcs of 11.7 km radius

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Lattice (LHC)

• Two beam channels in the same plane (18 cm
  separation in arcs) and cross at eight points.
• Eight 25 FODO cells (98 m long and phase advance
  of 90 deg per cell) per ring
• Four 9 m long dipoles and one 3 m quad in a half
  cell
• Beta in arcs max 166 m, min 29 m
• Dispersion in arcs max 1.86 m, min 0.9 m

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continued

• Working point (71.28, 70.31)
• Insertion 886 m long and phase advance in each
  plane by 2.5 units
• Chromaticity correction sextupoles next to the
  main quads, powered in 2 families
• Linear aperture 4 mm

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Lattice (SSC)

• FODO cell 192 m long and phase advance of 60 deg
• Five 16.5 m long dipoles and one 3.3m arc quad in
  each half cell
• Eight 42 cells per ring
• Beta in arcs max 332 m, min 111 m
• Dispersion in arcs max 3.92 m, min 2.36 m
• Natural chromaticity -204

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continued

• Working point (78.27, 78.28)
• Chromaticity correction sextupoles next to the
  main quads, powered in 2 families
• Linear aperture 5 mm

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Collision IR (LHC)

• 40 m free space between final quad triplets
• Beta star can be tuned from 0.5 m to 15 m
• Beta max 4 km
• Beam radius at IP 15 µm
• Beam divergence at IP 30 µrad

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Collision IR (SSC)

• 40 m free space between final quad triplets
• Beta star 0.5 m
• Beta max 8 km
• Beam crossing angle at IR 75 µrad, but can vary
  from 0 to 150 µrad

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Collective Effects (LHC)

• Beam lifetime 26.5 h
• Luminosity lifetime 11 h
• IBS emittance growth time 100 h (horizontal), 60
  h (longitudinal)
• Longitudinal microwave and transverse mode
  coupling instability are potential dangers.
  Coupled bunch instabilities require active
  feedback systems to control.

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Collective Effects (SSC)

• Beam lifetime 39000 h
• Luminosity lifetime 24 h
• IBS emittance growth time 126 h (horizontal),
  277 h (longitudinal)
• Relatively safe from single bunch instabilities.
  Coupled bunch instabilities require active
  feedback systems to control.