CLIC drive beam accelerating (DBA) structure Rolf Wegner.

14-Oct-2009 CLIC DBA Rolf Wegner 1

CLIC drive beam accelerating (DBA) structure

Rolf Wegner


Outline

• CLIC drive beam complex, 3 GHz DBA structure

• design of 1 GHz DBA structure

• optimisations for efficiency and filling time

• damping and detuning

• summary


CLIC RF power sourcefacc= 0.99952 GHz

Ipulse= 4.2 A

Vacc= 2.37 GV

Ppeak,RF ≈ 12 GW

Pavg,RF ≈ 90 MW


3 GHz DBA structure

facc= 3 GHz

Pin= 33 MW

ncell= 33

Length= 1.22 m

Øoutside= 17.4 cm

weight ≈ 200 kg

17.4 cm


3 GHz DBA structure

SICA = Slotted Iris – Constant Aperture


1 GHz DBA structure

• SICA principle• but no direct scaling possible

• 3 GHz: Ø= 17.5 cm, L= 1.2 m, weight= 200 kg1 GHz: Ø= 52.5 cm, L= 1.2 m, weight= 1800 kg

• klystron PRF ~ 10 to 15 MW(optimising klystron cost per MW and per operating hour and modulator cost)

• noise, phase error reduction if tfill= 240…250 ns(combination scheme => multiplication of phase noise,tDL≈ 245 ns, tCR I ≈ 2*245 ns, tCR II ≈ 6*245 ns)


basic cell geometry

Rb

gapb

Lb

gapa

La

RBP

Ra

110

60

11

18R 6

R 6

R 9

R 9

99.979

3 basic cells

typical dimensions


simulations of basic cells

variations:RBP

gap <=> vgr/c

tuning Ra => f0= 0.99952 GHz

0.5 1 1.5 2 2.5 3 3.5 4 4.5 50.5

1

1.5

2

2.5x 10

4

vgr/c [%]

Q0

RBP

=31.0mm

RBP

=35.0mm

RBP

=39.0mm

RBP

=43.0mm

RBP

=47.0mm

RBP

=51.0mm

0.5 1 1.5 2 2.5 3 3.5 4 4.5 50

50

100

150

200

vgr/c [%]

R/Q

0 [O

hm]

R/Q0=R0*T2/Q0

R0/Q0

0.5 1 1.5 2 2.5 3 3.5 4 4.5 50

2

4

6

vgr/c [%]

R [

MO

hm]

R0T2

R0

vgr/c range:min ~ 0.4% to 0.5%


design of TWS

gapn

RBPE0T

Vacc

Ncells

PoutPin

Pb Pb

constant aperture

η= ΔPb/Pin

tfill

mode spectrum


design of TWS

example:

Pin= 10 MWIb= 4.21 ANcells= 10RBP= 39 mm

vgr/c (gap) constη= 97.7%tfilling= 239.9 ns

vgr/c lin. distributionη= 98.0%tfilling= 252.7 ns

9 9.2 9.4 9.6 9.8 10 10.2 10.4 10.6 10.8 110

1

2

3

cell no

1-et

a(n)

[%

]

f0= 1.000 GHz, bore Radius= 39.00 mm, mean(Pin)= 10.00 MW

i_vgr=1

i_vgr=2

9 9.2 9.4 9.6 9.8 10 10.2 10.4 10.6 10.8 11230

240

250

260

cell no

t_fil

l [ns

]

1 2 3 4 5 6 7 8 9 100

1

2

3

cell no

vgr/

c0 [

%]


design of TWS

example:


vgr/c constη= 97.7%tfilling= 239.9 ns


1 2 3 4 5 6 7 8 9 100

1

2

3

4

5

6

cell no

E0T

[M

V/m

]

f0= 1.000 GHz, BP Radius= 39.00 mm, mean(Pin)= 10.00 MW

i_vgr=1

i_vgr=2

1 2 3 4 5 6 7 8 9 100

1

2

3

4

5

cell no

V_i

nt [

MV

]


design of TWS

1 2 3 4 5 6 7 8 9 100

2

4

6

8

10

cell no

P_i

n [M

W]


i_vgr=1

i_vgr=2

1 2 3 4 5 6 7 8 9 100

50

100

150

cell no

P_d

per

cel

l [kW

]

example:


vgr/c constη= 97.7%tfilling= 239.9 ns



9 9.2 9.4 9.6 9.8 10 10.2 10.4 10.6 10.8 110

1

2

3

cell no

1-et

a(n)

[%

]


9 9.2 9.4 9.6 9.8 10 10.2 10.4 10.6 10.8 110

500

1000

cell no

t_fil

l [ns

]

1 2 3 4 5 6 7 8 9 100

1

2

3

cell no

vgr/

c0 [

%]

9 9.2 9.4 9.6 9.8 10 10.2 10.4 10.6 10.8 110

1

2

3

cell no

1-et

a(n)

[%

]


9 9.2 9.4 9.6 9.8 10 10.2 10.4 10.6 10.8 110

200

400

cell no

t_fil

l [ns

]

1 2 3 4 5 6 7 8 9 100

1

2

3

cell no

vgr/

c0 [

%]

optimisations

Pin= 10 MWIb= 4.21 ARBP= 39 mm

Ncells= 10

vgr/c lin. distribution

vgr/c= [2.2% to 0.86%]

vgr/c= [1.7% to 0.86%]

vgr/c= [1.7% to 1.28%]


optimisations - efficiency

Pin= 10 MWIb= 4.21 ARBP= 39 mm

Ncells= 4 .. 16

vgr/c lin. distributionoptimised for

efficiency

4 6 8 10 12 14 160

2

4

6

cell no

1-et

a(n)

[%

]


i_vgr=91i_vgr=167

i_vgr=169

i_vgr=187

i_vgr=221i_vgr=240

i_vgr=210

i_vgr=165i_vgr=135

i_vgr=15

i_vgr=15

i_vgr=15i_vgr=15

4 6 8 10 12 14 16200

300

400

500

cell no

t_fil

l [ns

]

2 4 6 8 10 12 14 160

1

2

3

cell no

vgr/

c0 [

%]

efficiency


• noise damping => D, tfill

combined optimisations

DBA structure tasks:

• acceleration => ηRF

Drive Beam Accelerator

Delay Loop 2gap creation, pulse

compression & frequency

multiplication

1st Combiner Ring 3

2nd Combiner Ring 4

pulse compression & frequency multiplication

tDL~ 245 ns

appropriate tfill => noise suppression at f = 1/tDL


tfill [ns]

da

mp

ing

fa

cto

r D

245 nsD ≈ 1/18

368 nsD ≈ 1/4

124 nsD ≈ 1/4

combined optimisations

245 ± 8.5 ns D ≈ 1/17

t0= 245 ns

Δt= 8.5 ns

α= 2%

combination for optimisation

C(ηRF,tfill)= f1(ηRF) + f2(tfill)

DBA structure tasks:

• acceleration => ηRF

• noise damping => D, tfill

f1(ηRF)= 1- ηRF

f2(tfill)= α ((tfill-t0)/Δt)2

appropriate tfill => noise suppression at f = 1/tDL


optimisations

30 40 50 60 70 80 90

10

20

30

40

50

60

70

2 2

2

33

3

3

3

33

3

3

33 33

3

333

3

444

44

4

4

4

44

4

4

4

44

4

44

44

4

4

4

4444

44

4

55

5

5

5

5

5

5

5

55

5

5

5

5

5

5

5

55

5

55

5

5

5

5

55

5

6

6

6

6

6

6

6

6 6

6

6

6

6

6

6

6

6

6

66

6

6

6

6

6

6

6

6

7

7

7

7

7

7

7

7

7

7

7

7

77

77

7

7

RBP

[mm]

no o

f ce

lls

cost function [%], Pin= 10.00 MW, Ib= 4.21 A

2

2.5

3

3.5

4

4.5

5

5.5

6

6.5

7


optimisations

95

95

95

95

95

95

95

95

95

9595

96

96

96

96

96

96

96

96

9696

969696

9797

9797

97

97

97

97

97

9797

97

97

97

97.5

97.5

97.5

97.5

97.5

97.5

97.597.5

97.5

98

98

9898

98

98

98

98

RBP

[mm]

no o

f ce

lls

efficiency [%], Pin= 10.00 MW, Ib= 4.21 A

30 40 50 60 70 80 90

10

20

30

40

50

60

70

235

235

235

235

235

235

235

235

235

235

235

245

245

245

245

245245

245245

245245

245

245

245

245

245

245245

245

245 245

245

245

245

245

245

245

245

245

245245

245

245245

245

245

245

245245

245

245

245

245245

245

245

245

245

245

245

245245

245

245

245

245

245

245245245

245

245245

245245

245245

245

245

245

255

255

255

255

265

265

265

265

275

275

275

RBP

[mm]

no o

f ce

lls

filling time [ns], Pin= 10.00 MW, Ib= 4.21 A

30 40 50 60 70 80 90

10

20

30

40

50

60

70


optimisations

5 10 15 20 25 30 35 400

5

10

15Pin= 10.00 MW, Ib= 4.21 A

cell no

vgr/

c0 [

%]

N= 7, RB=33.0mm

N=10, RB=39.0mmN=13, RB=45.0mm

N=16, RB=53.0mm

N=19, RB=55.0mm

N=22, RB=59.0mmN=25, RB=63.0mm

N=28, RB=65.0mm

N=31, RB=71.0mm

N=34, RB=73.0mmN=37, RB=77.0mm

N=40, RB=79.0mm

235 240 245 250 2550

1

2

3

4

5

filling time [ns]

1-et

a [%

]


optimisations

ηRF ≥ 97.5 %

|tfill – 245 ns| ≤ 5 ns

0 10 20 30 40 50 60 70 80 900

10

20

30

40

50

60

70

RB [mm]

cell

no

no of cells <-> BP radius, eta >= 97.5%, |tfill-t0| <= 5.00 ns, Ib= 4.21 A

Pin= 5.00 MWPin= 10.00 MW

Pin= 15.00 MW

Pin= 20.00 MW

Pin= 30.00 MWPin= 40.00 MW


damping and detuningreduction of transverse wakefields by damping and detuning

Alexej Grudiev’s suggestion:dampers in web (~18 mm tick)

acc. mode Q0= 2.2 10∙ 4, Qext= 3.7 10∙ 7

distorted, 0.1° <=> 0.1 mm @ nose Qext= 1.5 10∙ 6 Pext,peak= 110 W, Pext,avg= 0.83 W (Pcell,peak= 30 kW, d.c. 0.75%)

Ø≈ 25 cm



0 20 40 60 80 100 120 140 160 180

1

1.5

2

2.5

3

3.5

phase advance per cell [°]

freq

uenc

y [G

Hz]

Monopole Modes

cell 01

cell 07

cell 11

beam may excite multiples of 0.5 GHz

(only every other bucket filled)

11 cell structureRBP= 41 mm


0 20 40 60 80 100 120 140 160 180

1

1.5

2

2.5

3

3.5

phase advance per cell [°]

freq

uenc

y [G

Hz]

Dipole Modes

cell 01

cell 07

cell 11


Q_11= 28Q_07= 34Q_01= 33

Q_11= 31


next steps

• wakefield calculation• optimisation of damping

• RF design• beam dynamics• mechanical design

=> iterations


summary

travelling wave structure for CLIC DBA• efficiency ≥ 97%• filling time 245 ns ± 5 ns• input RF power 5 to 40 MW • degree of freedom: no of cells <=> BP radius• transverse wakefield reduction by detuning and

damping• compact and effective damping

CLIC drive beam accelerating (DBA) structure Rolf Wegner.

Documents

Transcript of CLIC drive beam accelerating (DBA) structure Rolf Wegner.