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Magnetic Background Issues above 1Hz for CLIC beams
Cezary JachCLIC2009
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e+ injector, 2.4 GeV
e- injector2.4 GeV
CLIC 3 TeV
e+ main linace- main linac , 12 GHz, 100 MV/m, 20.85 km
BC2BC2
BC1
e+ DR365m
e- DR365m
booster linac, 9 GeV, 2 GHz or 4 GHz ?
decelerator, 24 sectors of 868 m
IP1
BDS2.75 km
BDS2.75 km
47.9 km
drive beam accelerator2.38 GeV, 1.0 GHz
combiner rings Circumferences delay loop 72.4 m
CR1 144.8 mCR2 434.3 m
CR1CR2
delayloop
326 klystrons33 MW, 139 ms
1 km
CR2delayloop
drive beam accelerator2.38 GeV, 1.0 GHz
326 klystrons33 MW, 139 ms
1 km
CR1
TAR=120m
TAR=120m
245m 245m
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Tolerance to variable fields
• In the Main Linac• In the long transfer line of the Main Beam• Near the IP• In all cases, we must consider– Frequencies above 1 Hz – Quasi-static field (above tolerance, implies re-
adjustment of the line)
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Main Linac & MB_LTL• Main Linac :
B < 0.2 nT at f>1 Hz
• Long Transfer Line :• Adding fields of variable f to the FODO
line• Track, get the beam displacement • From this, compute the tolerance ,
corresponding to 10% emittance growth after filamentation
B ≈ 0.01 nT at f>1 Hz
(To allow neat feed-back at 50 Hz - D. Schulte)
Study by J. Snuverink
(For incoherent addition by sector)
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Near the IP
Momentum Tolerance Field Current
P Δ B I @ 1m
250 GeV/c 0.1 nm 30 nT 0.14 A
1500 GeV/c 0.2 nm 80 nT 0.4 A
Current to produce B, in a conductor parallel to the beam in the horizontal planeat r from the beam axis :
s
L = 3.5 m
y
x
B
Δ⊗
⊗
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Possible Sources of Stray Magnetic Field
• High voltage transmission lines• Site power distribution system• Linac power distribution system• Electronics, vacuum pumps, compressors, etc.• Railroads• ?
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High voltage transmission lines
• Along the Jura, both in F +CH• Still awaiting detailed data from EDF and EOS• Considering a generic case:
● ●
● ●
● ●+I
+I
+I -I
-I
-I
7m
Bx = 16 nT at(+300m,-100m)
Even with the 1st-order cancellationoffered by the 3 phases , it remains :
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Coupling rejection
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Train Leakage Currents (LEP)*
*"The Influence of Train Leakage Currents on LEP Dipole Field" - CERN SL 97-47
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Train Leakage Currents (2)
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Train Leakage Currents (3)
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Train Leakage Currents (4)
Proportional to train leakage current
Proportional to LEP vacuum chamber current
ΔB/B ≈ 10-5
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FNAL data I - Courtesy of Dmitri Sergatskov
Data taken in the A0 exp-hall
In a ‘quiet’ officebuilding :10 × lower
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FNAL data II - Courtesy of Dmitri Sergatskov
• Level 10 × above HV-network estimate∼
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Next Steps
• Confirmation of stray magnetic field sensitivities
• Stray magnetic field mapping• Proposals for stray magnetic field reduction
methods– Local– general
• Cost impact