C L I CC L I C

9 March. 2010Alexej Grudiev, CLIC DR RF.

RF for CLIC DRUpdate 2010preliminary

9.03.2010Alexej

Grudiev

C L I CC L I C

9 March. 2010Alexej Grudiev, CLIC DR RF.

Energy acceptance - OKEnergy acceptance - OK

rf

s

p

rfrf

sss

V

U

h

EVe

h

EVeE

EE

ˆsin

ˆ2ˆ2

sin)2(cos

0

1

2

0

0

CLIC DR * NLC DR+

Circumference: C [m] 493.1 (corrected) 223

Bunch population: Ne 4x109 7x109

Energy : E [GeV] 2.86 ~2

Momentum compaction: αp 0.6x10-4 ?

Energy loss per turn: U0 [MeV]

5.8 0.635

RF frequency: frf [GHz] 0.9995 1.999 0.714

RF voltage: Vrf [MV] 10.8 7.4 1

Calculated RF parameters

Harmonic number: h 1644 3288

Synchronous phase : φs [o] 32.5 51.6

Energy acceptance: ΔE/E [%] 8.6 2.8

•*from Yannis on 27/01/2010•+ from Tor et.al., PAC95

C L I CC L I C

9 March. 2010Alexej Grudiev, CLIC DR RF.

Scaling of NLC DR RF cavity Scaling of NLC DR RF cavity

NLC DR RF cavity parameters CLIC DR RF

Frequency: f[GHz] 0.714 2 1

Shunt impedance: R [MΩ] (~ 1/√f)

3 1.8 2.5

Unloaded Q-factor: Q0 (~ 1/√f)

25500 15400 21500

Aperture radius: r [mm](~ 1/f)

31 11 22

Max. Gap voltage: Vg [kV] 500 180 360

Gradient: [MV/m] G ~ Vg/4r 4 4 4

HOM (σz=3.3mm)

Total loss factor: kl [V/pC] (~ f)

1.7 4.76 2.38

Fundamental loss factor: k0l

[V/pC] (~ f) 0.26 0.72 0.36

HOM loss factor: k||l [V/pC]

(~ f) 1.1 3.08 1.54

Transverse HOM kick factor: kT

t [V/pC/m] (~ f2) 39.4 309 77.3

From PAC 2001, ChicagoAN RF CAVITY FOR THE NLC DAMPING RINGSR.A. Rimmer, et al., LBNL, Berkeley, CA 94720, USA

From PAC 1995,Collective effects in the NLC DR designsT. Raubenheimer, et al.,

C L I CC L I C

9 March. 2010Alexej Grudiev, CLIC DR RF.

Comparison between NLC and Comparison between NLC and CLIC CLIC

Calculated RF cavity parameters fundamental

NLC DR CLIC DR

Frequency: f[GHz] 0.714 2 1Number of cavities: N = Vrf/Vg 2 (3) 41 30Total wall losses [MW] : POhm = Vrf

2/2NR 0.0833 0.371 0.778Peak beam current [A]: Ib = Qb*f 1 1.3 0.65Peak beam SR power [MW]: Pb = U0*Ib 0.635 7.54 3.77Loaded Q-factor: Qext = Q0*POhm /Pb 3345 756 4437Filling time [ns] :Tf = Qext/f 4685 378 4437Revolution Period [ns]: Tr = C/c 743 1643Duty cycle: D = 1 or (Tb+Tf)/Tr if < 1 ~1 ~0.33 ~1Total average rf power: [MW] Prf ~ POhm + Pb*D

~1 ~3 ~5

Average beam SR power [MW] : Pb*Tb/Tr 0.635 0.716Active length of RF system [m]: Lrf = Vrf/G 0.25 1.85 2.7Wall loss per unit length: [MW/m] POhm/Lrf 0.666 0.4 0.576Average -:- -:- -:- -: [MW/m] Tb/Tr*POhm/Lrf 0.666 0.13 0.576Gradient filling factor: F = Lrf/Ltot (~f) ~0.2 ~0.6 ~0.3Total length of RF system: [m] Ltot = Lrf/F ~1.25 ~3.1 ~9

C L I CC L I C

9 March. 2010Alexej Grudiev, CLIC DR RF.

Comparison between NLC and Comparison between NLC and CLIC CLIC

Calculated RF cavity parameters HOM NLC DR CLIC DR Frequency: f[GHz] 0.714 2 1Number of cavities: N = Vrf/Vg 2 (3) 41 30Long. HOM energy loss per turn per bunch [μJ]: ΔU = k||

l * N * eNe2

2.8 51.7 18.9

Incoherent long. HOM loss power [kW]: P||

incoh= ΔU * Nb/Tr2 9.8 3.6

Coherent long. HOM loss power [kW]: P||

coh~ P||incoh*QHOM *f/fHOM

(if the mode frequency fHOM is a harmonic of 2 GHz)

Careful Design of HOM damping is needed

Tran. HOM energy loss per turn per bunch [nJ]: ΔU = kT

t * 2πf/c * N * eNe2 * d2

(d – orbit deviation , 1mm assumed)

1.5 11 1.3

Tran. HOM loss power is not an issue: ~ [W]

C L I CC L I C

9 March. 2010Alexej Grudiev, CLIC DR RF.

1 or 2 GHz, pros and 1 or 2 GHz, pros and conscons

1 GHz 2 GHz

Beam loading

1 GHz rf system based on over-moded cavities with bigger stored energy can be used to solve the problem in conventional way (has been done before: LEP, KEK-B)

Completely different concept must be used (see next slide). Never been demonstrated before. Higher risk. More studies are needed.

Very interesting

RF power Roughly 2 times more power

More efficient

Size Roughly 2 times longer 2 X Shorter (probably can be done even more compact because average cavity wall loss is 4 times lower, if yes it has also impact on HOM power loss)

HOM Roughly 3 times lower HOM power loss (incoherent)

Higher HOM power loss

Rf power source

IOTs can be used. There are even R&D on L-band solid state rf system…

Only klystrons

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9 March. 2010Alexej Grudiev, CLIC DR RF.

Concept at 2 GHz Concept at 2 GHz

Rf cavity

Pulsecompressor

Kly

stro

n

CW

Phase flip 2 times per revolution period

Right pulse shape after compression

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9 March. 2010Alexej Grudiev, CLIC DR RF.

Vacuum Electron Device Limitations for High-Power RF Sources

0.1 1 10 100 1000

Frequency (GHz)

Considerable part of former klystron domain claimed by IOTs

Why?

9Heinz Bohlen,Thomas Grant, CPI

Vacuum Electron Device Limitations for High-Power RF Sources

IOTs have operational advantages…

- Efficiency- Absence of saturation- Pulse-able via RF- Small size- High linearity

…and they are less expensive!

Disadvantage:

- Low gain (± 22 dB)

10