CLIC MAIN LINAC DDSCLIC MAIN LINAC DDS

Vasim Khan

24 cellsNo interleaving

48cells2-fold interleaving

∆fmin = 32.5 MHz∆tmax =30.76 ns∆s = 9.22 m

24 cellsNo interleaving

∆fmin = 65 MHz∆tmax =15.38 ns∆s = 4.61 m

48cells2-fold interleaving

Summary of results

96 cells4-fold interleaving

192 cells8-fold interleaving

V. Khan LC-ABD 09, Cockcroft Institute 22.09.09 8/13

96 cells4-fold interleaving

∆fmin = 16.25 MHz∆tmax = 61.52 ns∆s = 18.46 m

192 cells8-fold interleaving

∆fmin = 8.12 MHz∆tmax =123 ns∆s = 36.92 m

Summary of results

A 1.19

GHz 11.9942

6101.61072.3

I19-9

For CLIC_G structure <a>/λ=0.11, considering the beam dynamics constraint bunch population is 3.72 x 10^9 particles per bunch and the heavy damping can allow an inter bunch spacing as compact as ~0.5 ns. This leads to about 1 A beam current and rf –to-beam efficiency of ~28%.

For CLIC_DDS structure (2.3 GHz) <a>/λ=0.126, and has an advantage of populating bunches up to 4.5x10^9 particles but a moderate Q~500 will require an inter bunch spacing of 8 cycles (~ 0.67 ns).

A 1.13

GHz 11.9942

8101.6104.75

I19-9

V/pc/mm/m 1.71072.3150

10410010W

9

9limitT

V/pc/mm/m 5.6104.75150

10410010W

9

9limitT

Though the bunch spacing is increased in CLIC_DDS, the beam current is compensated by increasing the bunch population and hence the rf-to-beam efficiency of the structure is not affected alarmingly.

CLIC_G vs CLIC_DDS

Parameters CLIC_G (Optimised)

[1,2]

CLIC_DDS(Single

structure)

CLIC_DDS(8-fold

interleaved)

Bunch space (rf cycles/ns) 6/0.5 8/0.67 8/0.67

Limit on wake (V/pC/mm/m) 7.1 5.6 5.3*

Number of bunches 312 312 312

Bunch population (109) 3.72 4.7 5.0*

Pulse length (ns) 240.8 273 272.2*

Fill time (ns) 62.9 42 40.8*

Pin (MW) 63.8 72 75.8*

Esur max. (MV/m) 245 232 236

Pulse temperature rise (K) 53 47.3 51

RF-beam-eff. 27.7 26.6 26.7*

Figure of merit (a.u.) 9.1 8.41 8.29*

[1] A. Grudiev, CLIC-ACE, JAN 08[2] H. Braun, CLIC Note 764, 2008* Mean value of 8 structures

CLIC_G vs CLIC_DDS

Single structure vs. Interleaved structure

Interleaved structures

Single structure

Interleaved structures

Single structure

Single structureSingle structure

Mean ofinterleaved structures

Mean ofinterleaved structures

Sumwake: 8-fold interleaved structure

Mean deviation RMS sumwake

Random error

RMS ∆f = 3.5 MHz

Random error

RMS ∆f = 2.4 MHz

Eight fold Interleaving

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

1 9 17 185

Single structure

2 10 18 186

3 11 19 187

4 12 20 188

5 13 21 189

6 14 22 190

7 15 23 191

8 16 24 192

Decoupling end cell from each structure

Decoupling 2 end cells from each structure

Decoupling both the end cells from each structure

Decoupling two end cells from either side from each structure

Decoupling first cell and two end cells from each structure + RMS 2.5 MHz Random error

Decoupling first cell and last cell from each structure + RMS 2.5 MHz Random error

A typical geometry : cell # 1

R

h

r1

h1

L

a1

t/2

a

b

Rc

a

a+a1

R

Structure GeometryCell parameters

a1

t/2

a

L

b

Rc

a

a+a1

RIris radius Iris radius

Cavity radius Cavity radius

Sparse Sampled HPT (High Power Test)

Fully Interleaved8-structures

amin, amax= 4.0, 2.13

bmin, bmax= 10.5, 9.53

Structure GeometryCell parameters

a1

t/2

a

L

b

Rc

a

a+a1

RIris thickness Iris thickness

Ellipticity Ellipticity

Sparse Sampled HPT (High Power Test)

Fully Interleaved8-structures

t

a 2ε 1

tmin, tmax= 4.0, 0.35

εmin, εmax= 1.0, 2.0

Structure GeometryManifold parameters

a1

t/2

a

L

b

Rc

a

a+a1

RDegree of manifold penetration

Manifold radius

Sparse Sampled HPT (High Power Test)

Fully Interleaved8-structures

Degree of manifold penetration

Manifold radius

Rcmin, Rcmax= 6.2, 7.5

Rmin, Rmax= 3.25, 2.3

Structure # 1 in an 8-fold interleaved design

Structure # 8 in an 8-fold interleaved design

Structure # 1 in an 8-fold interleaved design

Structure # 8 in an 8-fold interleaved design

Structure # 1 in an 8-fold interleaved design

Structure # 8 in an 8-fold interleaved design

Sparse Sampled Structure

Structure # 1 in an 8-fold interleaved design

Structure # 8 in an 8-fold interleaved design

Sparse Sampled HPT (High Power Test)

Fully Interleaved 8-structures

dn/df

Kdn/df

dn/df

Kdn/df

dn/df

Kdn/df

dn/df

Kdn/df

Sparse Sampled HPT (High Power Test)

Fully Interleaved 8-structures

Structure # 1 in an 8-fold interleaved design

Structure # 8 in an 8-fold interleaved design

SRMS: Random errors with 20 iterations

∆f = +/- 4.0 MHzRMS ∆f ~ 2.3 MHz