impact of synchrotron radiation in lepton collider arcs
DESCRIPTION
Impact of synchrotron radiation in LEPTON COLLIDER arcs. Francesco Cerutti , Alfredo Ferrari, Luisella Lari *, Alessio Mereghetti. *BE department. Acknowledgments:B. Holzer , R. Kersevan , A. Milanese. FCC study kickoff meeting Lepton collider design - PowerPoint PPT PresentationTRANSCRIPT
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IMPACT OF SYNCHROTRON RADIATION IN LEPTON COLLIDER
ARCSFrancesco Cerutti, Alfredo Ferrari, Luisella Lari*, Alessio
Mereghetti
*BE department
FCC study kickoff meetingLepton collider design
University of Geneva, Feb 14, 2014
Acknowledgments: B. Holzer, R. Kersevan, A. Milanese
F. Cerutti FCC study kickoff meeting Geneva, 2014 February 14 2
OUTLINE
- simulation of synchrotron radiation interaction
- a (too?) much preliminary layout and the role of absorbers- power sharing- beam chamber and water heating- dose to hypothetical coils- ozone production
- a shielded beam chamber- absorption and leakage- photoneutrons and activation
F. Cerutti FCC study kickoff meeting Geneva, 2014 February 14 3
SYNCHROTRON RADIATION
[km][GeV]1021.2[MeV]c
23 3
63
EEE cc
MeV][[GeV]1098.3[GeV/turn]παγ98 2
cirrcirr EEEEE
F. Cerutti FCC study kickoff meeting Geneva, 2014 February 14 4
E= 8.5 GeV/turn (dE/ds=1.375 keV/cm in the dipoles) P = 8.5 x I[mA] MW = 8.5 x 10mA = 85 MW in the whole accelerator (dP/ds= 1.375 x I[mA] W/cm in the dipoles)
SYNCHROTRON RADIATION
95.75% of the photon amount
<E>=395 keV
99.99964% of the total power
E>100 eV
F. Cerutti FCC study kickoff meeting Geneva, 2014 February 14 5
RELEVANT FLUKA CAPABILITIES
Sophisticated low energy photon transport including polarization effects for Compton, photoelectric and coherent scattering, and full account for bound electron effects: already available in FLUKA since several years
New: dedicated “generic” source for SR radiation accounting for: Spectrum sampling Polarization as a function of emitted photon energy Angular distribution Arbitrary orientation emitting particle vs magnetic field Photon emission along arcs/helical paths
F. Cerutti FCC study kickoff meeting Geneva, 2014 February 14 6
inside the same dipole only if ℓ >
SYNCHROTRON RADIATION INTERCEPTIONℓ
𝑅ℓ dipole length
vacuum chamber radius
accelerator bending radius
ℓ
𝑅
for = 9 km and = 4.5 cm ℓ > 28.5 m
totally escaping for shorter dipolesshielding in the interconnects ?
for = 3.1 km and = 6.5 cm (LEP2) ℓ > 20 m
F. Cerutti FCC study kickoff meeting Geneva, 2014 February 14 7
LAYOUTMODEL
25 mm
10.5 m dipole
24 cm absorber
1.5 mQ
Copper (2mm tube)
water cooling
Lead
Iron + plastic
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TOTAL POWERnormalized to 10 mA beam current
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BEAM CHAMBERnormalized to 10 mA beam current
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WATER
values averaged along the dipole length
normalized to 10 mA beam current
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DIPOLE COILSnormalized to 10 mA beam current over 116 days/year
front face masks ?
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DIPOLE COILS
values averaged along the dipole length
normalized to 10 mA beam current
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OZONE
Adapted from NCRP Report 51 and LEP Note 379(under the assumption of no O3 decomposition, yielding in the t expression a neglected term kPeV/V with k decomposition constant equal to 1.4 10-16 cm3/eV)
t
t
t
t
tt
t
teV
O
venteV
Air
AirAvO
vent
t
Air
AirAv
eVoO
VsPGC
rPP
NTPA
NGC
O
AVN
PGCC
e1][cm
][[eV/s]]eV[109.28 [ppm]
renewal/s][air 1[W]1024.6 [eV/s]
]/cm[molecules1050.2@eV]/[O074.006.0232.0
constanton dissociati ][s103.2)/1(e1
31-15-
18
3193
31-41
3
2
2
3
For P=10 W in air, V108 cm3, tvent10 h at saturation CO31-2 ppm
F. Cerutti FCC study kickoff meeting Geneva, 2014 February 14 14
SHIELDED BEAM CHAMBER
B
3 mrad
Scoringsurfaces
Beam chamber: round IR = 4.5 cm
Aluminum pipe: thickness = 0.5 cm
Lead shielding: thickness = 5.0 cm
o 9 km radius, Ec = 1.32 MeV
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GRAZING INCIDENCE EFFECT
Radius or Depth sin(3 mrad) (cm)
3 mrad incidence
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THE PHYSICAL EXPLANATIONThe first scattering effect: after a Compton interaction the photon loses
“memory” of the initial grazing incidence because of the much larger scattering angle
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BENDING (NO) EFFECT
AlPb
Vacu
um
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Vacu
um
Al
Pb
BENDING (NO) EFFECT
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SPECTRUM EVOLUTIONAnnihilationPb Kx linesAl Kx lines
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REFLECTION INTO VACUUM
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ESCAPING POWER
100%
10%
1%
0.1%
Al
Pb
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ESCAPING RADIATION
Pb
Al
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NEUTRON PRODUCTION AND ACTIVATION
Neutron production: 1.110-10 n/cm/e, 7105 n/s/cm/mAActivity at saturation: 170 kBq/cm/mA(mostly 203Pbgs/m, 26Alm,205Pbm) After 1 day: 5.5 kBq/cm/mAAfter 1 week: 800 Bq/cm/mA(almost only 203Pb)
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OPENING CONCLUSIONS
extensive calculation of synchrotron radiation is possible with full generality
as expected the attenuation curve is insensitive to the incidence angle and (unfortunately) far from naïve line-of-sight approximations
localized absorbers look as an attractive option. More realistic shape is under way (possibly integrated inside the dipoles)
which magnets? Coils on the external side of the beam would be highly exposed
F. Cerutti FCC study kickoff meeting Geneva, 2014 February 14 25
RESERVESLIDES
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PHOTON CROSS SECTION
Compton dominated
Compton dominated
Photoelectric dominated
Photoelectric dominated
Pair dominated
Pair dominatedp.e.=photoelectric incoh=Compton coherent=Rayleigh nuc=photonuclear
N=pair production, nuclear field e=pair production, electron field