impact of synchrotron radiation in lepton collider arcs

1

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

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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