LNF Laboratory Report

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LNF Laboratory Report

• S. Guiducci

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Damping Ring Kickers

• An injection extraction scheme for TESLA based on
  RF deflectors has been suggested by P. Raimondi.
• A solution for the present DR design has been
  worked out at LNF.
• The possibility of obtaining a much shorter bunch
  distance in the DR is envisaged.
• This opens the possibility of having an unified
  DR design for any LC project independent on the
  Linac technology (warm/SC)

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APDG Working GroupTESLA Damping Ring
Injection/Extraction Schemes with RF Deflectors
D. Alesini, F.Marcellini TESLA Damping Ring
RF Deflectors Design F.Marcellini, D. Alesini
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INTRODUCTION CTF3 INJECTION SCHEME
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Two frequenciesf24f1 F16
Recombination factor F16 CTF3 Recombination
factor F5
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CTF3-LIKE INJECTION/EXTRACTION SCHEME
-Number of bunches in the Linac NB -Bunch time
spacing in the Linac ?TL (Bunch spacing ?LL
?TLc) -Total length of the bunch train LB
-Number of RF deflectors 2 (1 inj. 1
extr.) -fRF n1/ ?TL (in the Figs.
n1) -Recombination Factor (F) -Total length of
the damping ring (LDR) LB/F? ?LL/F -Bunch time
spacing in the Damp. Ring ?TDR ?TL/F -(Bunch
spacing ?LDR ?LL/F)
Injection
Extraction
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• If the filling time (?F) of the deflectors is
  less than ?TDR it is possible to inject or
  extract the bunches without any gap of the
  filling pattern in the DR
• ?? should be ? ?? (depending on the ring
  optics)
• (considering a single RF frequency ?
  ??/?MAX1-cos(2?/F))

IN THE TESLA CASE (first evaluations made by J.P.
Delahaye)

• -NB 2820
• -?TL 337 ns
• (?LL101 m)
• -LB ?285 km
• -fRF ?1.3 GHz ( 4381/ ?TL)
• -F20
• -??0.6 mrad
• -LDR ? 14 km
• -?TDR 16.85 ns

TESLA klystrons
inj./extr. with more RF frequencies near 1.3 GHz
??/?MAX ? 5 ? ?MAX ? 12 mrad!!

• TW RF Deflectors
• GAP

?F ? 16.85 ns !!
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RF Deflectors

• Recombination factor F20
• Gap to turn on and off the deflectors
• 1 empty bucket over 141
• Two (or Three) Frequencies near 1.3 GHz
• (Linac Klystron)
• Effect of bunch length
• Error sensitivity
• Design of the deflectors

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3 Km Damping Ring?

• F100 is feasible for a very short bunch length
  sl 2mm.
• How critical?
• An exercise
• A parameter list for a 3Km long DR

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Space charge tune shift
TDR DQ .23 Short DR DQ .23 .18 / .33
.13 C 17Km 3Km
.18 sl 6 mm
2 mm .33
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Damping time

• ? gC/U0 U0 g2
  ?B2 dl
• U0 U0,arc U0,wig U0,arc (1 Fw)
• To get the same damping time
• U0 21 3/17 ? 3.7 MeV
• and
• ?B2 dl 605 3/17 ? 107 T2m

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Emittance
ex ea/(1Fw) ew Fw/(1Fw) 8 10-6 m TDR
ea/(1Fw) 2 10-6m ew Fw/(1Fw) 6 10-6
m Bw 1.6 T Fw 17.5 Short DR ea/(1Fw)
7 10-6 m ew Fw/(1Fw) ew ? Bwig3 l2ltbgt 1
10-6 m Bw .8 T Fw ? smaller or ea ? larger
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e Parameters _at_5GeV
TDR Short DR
Circumference Km 17 3
Inj. emittance rms (m) .01 .01
Norm. emitt. hor/ver (m) 8/2 10-6 8/2 10-6
Damping time (ms) 28 28
Bunch num/space (ns) 2820/ 20 2820/ 3.5
Particles/bunch 2 1010 2 1010
?B2 dl (T2m) 605 107
Wiggler l (m) / B0 (T) .4 / 1.6 .4/ 0.8
Energy loss/turn(MeV) 21 3.7
Rel. Energy spread sp 1.3 10-3 .65 10-3
Bunch length (mm) 6 2
Space charge DQ .23 .13
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Conclusions
RF deflectors for the Damping Ring with a
recombination factor F20 are proposed. The
possibility of a larger recombination (F100) is
interesting in order to shorten the Damping Ring
and make it less demanding.
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RF DEFLECTORS AND RECOMBINATION
1st turn - 1st bunch train from linac
2nd turn
3rd turn
4th turn
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TW RF DEFLECTORS GAP
nB1? 1 bunch over 141 ? TG337 ns