RF Technology

RF Technology

Professor Richard CarterLancaster University Engineering Department

23rd November 2006

RF Presentation to CI SAC 23 Nov 2006 2

Research group focus

• Electromagnetics• High power RF and

microwave engineering• Particle dynamics in RF

electromagnetic fields• Vacuum electronics

Courtesy of Thales Electron Devices


Staff

• Academic staff– Prof. Richard Carter– Dr Amos Dexter– Dr Rebecca Seviour

• Research staff– Dr Graeme Burt– Dr Richard Jenkins– Jonny Smith– Imran Tahir– 2 Vacancies

• Research Students– Chris Hill– Sharon Crane– Fay Hannon– Emma Wooldridge– Chris Lingwood


Resources• Microwave laboratory

– Test equipment– High power sources– Vacuum equipment– Auger spectrometer

• Software– Commercial

• (MAFIA, MWS, Lorenz HF, MAGIC, KOBRA3, Accelrys, GdfidL, FEMLab)

– Indigenous • (Small and large-signal models for klystrons and travelling-wave

tubes, models of helix and coupled-cavity slow-wave structures)


Current research projects

• Microwave tubes– Stabilisation of c.w. magnetron oscillators– High power magnetron for IFMIF – Radial inductive output tubes– Multiple beam klystron for CLIC

• Particle accelerators– Energy recovery linac stability for 4GLS– Crab cavity system for the ILC– Collimator for the ILC– High brightness gun for 4GLS

• RF vacuum breakdown (Multipactor)


Future research projects

• Superconducting RF systems

• Parallel operation of stabilised magnetrons

• Secondary electron emission theory

• Cavity technology for the Neutrino Factory


Stabilisation of c.w. magnetron oscillators

• Dr Amos Dexter, Imran Tahir

• PLL control of frequency• Injection locking• Phase locking to better

than 1%• Injected power – 37dB• Magnetrons could be used

as high efficiency, low cost sources for accelerators

-80

-60

-40

-20

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-running magnetron

• Magnetron with PLL frequency control

• Magnetron with PLL control and injection


High Power RF Sources for IFMIF• Prof Richard Carter, Carl Beard• Conceptual design report:1 MW c.w., 175 MHz, 90% efficiency

Diacrode IOT Magnetron

Anode voltage

14 kV 95 kV 60 kV

Anode current

103 A 58 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

Electro-magnet

No Yes (except the radial IOT) Yes

Availability Yes Would require 2 - 3 years R&D Would require 4 – 5 years R&D

R&D issues None • Mechanical stability of control grid• Multi-element depressed collector design• Multi-beam and radial beam designs

• Cathode choice for long life• Development of switched mode power supply • Demonstration of simultaneous control of amplitude and phase• Stability


Radial inductive output tubes

• Sharon Crane (PhD student),

• Prof. Richard Carter

• Collaboration with E2V Technologies

• Target 1 GHz, 1 MW c.w.

Collector

Output cavity

Input cavityRF Output

Grid bias and RF Input

Cathode

Anode


Multiple beam klystron for CLIC

• Chris Lingwood (PhD student), Prof. Richard Carter

• Investigation of novel multiple beam klystron concepts for CLIC

• 1 GHz, 50 MW pk

• Collaboration with CERN and Thales Electron Devices

• Previous project – Future Linear Collider Klystron Study – Dr Jinjun Feng, Collaboration with CERN, DESY, E2V

Technologies, TMD Technologies.


Energy recovery linac stability for 4GLS

• Emma Wooldridge (ASTeC Staff, PhD Student)

• Prof. Richard Carter

• Susan Smith (ASTeC)

• Study of beam break-up and its prevention



High brightness gun for 4GLS

• Fay Hannon (PhD student) • Dr Rebecca Seviour• Dr Bob Rimmer (JLab)• Project funded and based at JLab


RF vacuum breakdown (Multipactor)

• Dr Rebecca Seviour, Dr Richard Jenkins, Dr Matt Stables, Chris Hill (PhD Student), Prof. Richard Carter

• Theoretical and experimental study of multipactor discharges in complex structures

• Collaboration with E2V Technologies

• Previous project – Multipactor in the CESR RF system, – Dr Philippe Goudket, Professor Richard Carter, Mike Dykes

(ASTeC) – Collaboration with Cornell University


Multipactor – Experimental Work

• Chris Hill (PhD Student) • Prof Richard Carter• Multipactor in a klystron input cavity


Multipactor – Simulation

• Dr Rebecca Seviour• Dr Matt Stables

• Aim – Computer simulation of multipactor in complex geometries

• Issues– Accuracy of fields close to

surfaces– Knowledge of energy spectrum

of secondary electrons


Multipactor – Secondary Electron Emission Measurements

• Dr Richard Jenkins• Prof Richard Carter• Re-commissioning of Auger

spectrometer

E.D.C. for different beam voltages

0

0.5

1

1.5

2

2.5

3

-410 -370 -330 -290 -250 -210 -170 -130 -90 -50 -10

Retarding Potential E

N(E

)

100V150V200V300V400V

Acid cleaned, not outgased Ni SAMPLE, :5 * 10^-8 Torr1st derivative of current (EDC)A1=1KV, A2=200V,A3,A4=Variable10^-9, BW=3, Vac=0.5V Vcoll=250 VFreq=high, Phase shift =+20100SECS 100V SWEEP


Multipactor – prediction of secondary electron emission coefficients

• Dr Rebecca Seviour• Accelrys used to investigate band diagrams of materials

TiN = 1

TiN

Al2O3

Muon Ionisation Cooling for NF & MICE

Need:• 201 MHz Resonant Cavities at 16 MV/w in 4T field• High accuracy measurement of the Eacc

• Dr Rebecca Seviour• 1 x PhD (MICE Phase II)


RF Cavity development

• Dr Rebecca Seviour• 2 x Post Doc’s (NF)



Without Magnetic field has achieved 16 MV/m

Electric field Magnetic field Surface currents

Scattering causes losses limits current

limits RF limits acceleration

Metal

Vacuum

Excitation MotionImpurities


We propose to conduct a systematic review of each stage of manufacture.

Investigating the effect each stage has on the surface topology and chemical composition of the surfaces, and ultimately the effect on cavity performance.

• Auger Spectrometry

• Atomic force microscopy

These results will also be compared to theory.

Transport

CodesCavity Q



RF Cavity development: Alternatives to EP

Al2O3 suspended in

PH7 Solution.

CMP cheaper & less hazardous than EP.

Only useful on flat areas

Chemical Mechanical Polishing (CMP)

(Rohm and Haas Electronic Materials)


Ra ~ 0.4 m

Abrasive Flow (AF)

RF Cavity development: Alternatives to EP


PBG Based Particle Acceleration

• Dr Rebecca Seviour• 2 x Post Doc’s • 2 x PhD’s• 1 x MSc


• RF Creation

• Particle Acceleration

• Slow-wave structures

• Inverse Cherenkov Acceleration

• Quasi-Crystals/Metamaterials

PBG Based Particle Acceleration


Selected Publications• Carter RG., ‘Accuracy of microwave cavity perturbation measurements’, IEEE Transactions on Microwave Theory

& Techniques, vol.49, no.5, pp.918-23. (2001)

• Geng RL. Padamsee H. Belomestnykh S. Goudket P. Dykes DM. Carter RG., ‘Suppression of multipacting in rectangular coupler waveguides’, Nuclear Instruments & Methods in Physics Research Section A-Accelerators Spectrometers Detectors & Associated Equipment, vol.508, no.3, pp.227-38. (2003)

• Tahir I., Dexter A.C and Carter R.G., ‘Noise Performance of Frequency and Phase Locked CW Magnetrons operated as current controlled oscillators’, IEEE Transactions on Electron Devices, vol.52, no.9, pp.2096-2103, (2005)

• Dexter A.C. and Seviour R. ‘Rapid Generation of Multipactor Charts by Numerical Solution of the Phase Equation’, J. Phys D: Appl. Phys. vol 38, pp1383-1389, (2005)

• Seviour, R. ‘The Role of Elastic and Inelastic Electron Reflection in Multipactor Discharges’, IEEE Transactions on Electron Devices, vol.52, pp.1927-1930, (2005)

• Geng RL, Goudket P, Carter RG, Belomestnykh S, Padamsee H, Dykes DM, Dynamical aspects of multipacting induced discharge in a rectangular waveguide, Nuclear Instruments & Methods in Physics Research Section A-Accelerators Spectrometers Detectors & Associated Equipment, vol.538, pp.189-205, (2005)

• Tahir I., Dexter A.C and Carter R.G., ‘Noise performance of frequency- and phase-locked CW magnetrons operated as current-controlled oscillators’, IEEE Transactions on Electron Devices Volume 3, no.7, pp.1721–1729, (2006)

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RF Technology