LHC (SSC)
Byung Yunn
CASA
Parameters
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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
continued
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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)
continued
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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 (/cm^2-s ): 1.65e34 (1.0e33)
Number of interaction points: 3 (4)
Synchrotron radiation power (per beam): 9.1
(9.1) kw
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.
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)
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)
Collider ring (SSC)
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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
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
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
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
continued
• Working point: (78.27, 78.28)
• Chromaticity correction: sextupoles next to
the main quads, powered in 2 families
• Linear aperture: 5 mm
Collision IR (LHC)
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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
Collision IR (SSC)
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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
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.
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.