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RF Sources

Professor Richard Carter Lancaster University Engineering Department

27th November 2007



RGC Presentation to CI SAC 27 Nov 2007 2

Multiple-Beam Klystron for CLIC

• Collaboration with Thales ElectronDevices and CERN

• Chris Lingwood (PhD student)

• Current target design – 1.3 GHz, 15 MW pk, 80% efficiency

• Research challenges

– Cavity design – Interaction design

– Stability

– Electron optics




Multiple-beam klystron cavity studies

20 beams

Coaxial Cavity

TM 0 1 TM 10 1

Reentrant Cavity

Whispering Gallery




Multiple-beam klystron interaction studies

Interaction design for 15 MW, 80% efficiency

CLIC MBK ( f req = 1.31 cavité 6 Qex ( cavi té 2 f0 = 1.35 cavité 3 shift = 300 )

F = 1.30000 Pe = 1.000000e+001 Ps = 7.555e+005 % = 80.02

0

0.5

1

1.5

2

2.5

0.000E+00 5.000E+02 1.000E+03 1.500E+03 2.000E+03 2.500E+03

Z MM

a m

p l i t u d e d u c o u r a n t d e m o d u

l a t i o n ( A )

harm 1harm 2

harm 3

harm 4

I0

2*I0

Gaps




Klystron Transient Performance

Objective: Understand and model klystron transient performance for crab cavity control systems

• TH2450 klystron

amplifier

– 3 kW, 6 GHz, 45

MHz bandwidth

• Research Assistant:

Dr Richard Jenkins




Small-signal results

TH2450 Klystron: Small-Signal Gain

0

10

20

30

40

50

5.95 6 6.05 6.1 6.15 6.2

Frequency (GHz)

G a

i n ( d B )

Measured

AJ-Disk

Mathcad

• Tube data supplied by

Thales and CPI

• Tube modelled with

– Linear model

– SLAC AJ-Disk code

• Tube data confirmed

• Tuning of models not yetaligned with experiment




Transient performance

transien t measurements for a 200kHz modulated signal

0

0.5

11.5

2

2.5

3

3.5

4

4.5

0 1 2 3 4 5

time /microseconds

o u

t p u t s i g n a l / m V

input signal

klystron

• First ASK transient

measurements

• PSK measurements planned

• Modelling to be based onSLAC paper

T.L. Lavine, R.H. Miller, P.L. Mortonand R.D. Ruth

Transient analysis of multicavityklystrons

PAC 1989, pp.126-128




Radial inductive output tube

Collector

Output cavity

Input cavityRF Output

Grid bias and RFInput

Cathode

Anode

• Collaboration with E2V

Technologies

• PhD student: Sharon

Crane (part-time)

• Target 1 GHz, 1 MW c.w.




Radial Inductive Output Tube

• Research challenges

– Electron optics – Gridded electron gun

– Input cavity

– Output cavity

– Stability




Stabilisation of c.w. magnetron oscillators

• Dr Amos Dexter, Imran Tahir

• Phase-locked loop control of frequency

• Injection locking

• Phase locking to better than 1%

• Injected power – 37dB

-8 0

-6 0

-4 0

-2 0

0

2.430 2.440 2.450 2.460 2.470

Frequency (GHz)

-80

-60

-40

-20

0

2.43 2.44 2.45 2.46 2.47

Frequency (GHz)

-80

-60

-40

-20

0

2.4496 2.4498 2.45 2.4502 2.4504

Frequency(GHz)

RBW 2KHz

• Free-runningmagnetron

• Magnetronwith PLLfrequency

control

• Magnetronwith PLLcontrol and injection

Tahir I., Dexter A.C and Carter R.G.,

‘Noise Performance of Frequency and Phase Locked CW Magnetrons operated as current controlled oscillator s’ ,

IEEE Transactions on Electron Devices, vol.52, no.9, pp.2096-2103, (2005)




CW Magnetrons: State of the Art

CW Magnetron Efficiency

50%

60%

70%

80%

90%

100%

1 10 100 1000

Power (kW)

E f f i c i e n c y L Band

S Band

Shibata

Pf 2 scaling from 100 kW at 915 MHz suggests that it should bepossible to achieve at least

* 50 kW CW at > 80% efficiency at 1.3 GHz

* 2 MW CW at > 90% efficiency at 200 MHz




Comparison of Power Sources for IFMIF

(1 MW CW at 200 MHz)

Diacrode IOT Magnetron

Anode

voltage

14 kV 95 kV 60 kV

Anode

current

103 A 16 A 20 A

Efficiency 71% 65% (>75% with a multi-

element depressed

collector

90 %

Gain 13 dB 23 dB > 30 dB

Drive power 50 kW 5 kW < 1 kW

Cooling Anode Collector Anode and (probably) cathode

Electromagnet No Yes (except the radial IOT) Yes

Availability Yes Would require 2 - 3 years

R&D

Would require 4 – 5 years R&D




The magnetron is an attractive possibility

for future accelerators, BUT

• Performance and reliability of a prototype must be demonstrated

• Industry would be unlikely to commit resources to such a speculative project

• Proposed research:

– Stage 1: Detailed design study of a 50 kW, 1.3 GHz magnetron

– Stage 2: Build a prototype 50 kW, 1.3 GHz magnetron and install it on ERLP (e.g.)

– Stage 3: Detailed design study of a 1 MW, 200 MHz magnetron

– Stage 4: Build a prototype 1 MW, 200 MHz, magnetron and install it on MICE(e.g.)

• The committee’s comments are invited

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