ABP Research Seminar Adams Institute Glasgow, G4 0NG, UK - PowerPoint PPT Presentation

Research Progress at Strathclyde Research Progress at Strathclyde relevant to Accelerators relevant to Accelerators Alan Phelps Alan Phelps A.W. Cross, K. Ronald, C.G. Whyte, A.R. Young, W. He, I.V. Konoplev, A.W. Cross, K. Ronald, C.G. Whyte, A.R. Young, W. He, I.V. Konoplev, D. Barclay, H. Yin, C.W. Robertson, D.C. Speirs, C.R. Donaldson, P . D. Barclay, H. Yin, C.W. Robertson, D.C. Speirs, C.R. Donaldson, P . MacInnes, MacInnes, S.L. McConville, K.M. Gillespie, L. Fisher, F . Li, M. McStravick, L. Zhang, S.L. McConville, K.M. Gillespie, L. Fisher, F . Li, M. McStravick, L. Zhang, D. Constable, D. Bowes, K.A. Matheson, R. Bryson, M. King, P . D. Constable, D. Bowes, K.A. Matheson, R. Bryson, M. King, P . McElhinney McElhinney Department of Physics, SUPA, University of Strathclyde, Department of Physics, SUPA, University of Strathclyde, ABP Research Seminar Adams Institute Glasgow, G4 0NG, UK Glasgow, G4 0NG, UK 17 June 2010 Oxford University

Introduction Introduction  Strathclyde research group overview Strathclyde research group overview  SUPA SUPA  Strathclyde research Strathclyde research High power microwave sources High power microwave sources Examples of modelling and experiments Examples of modelling and experiments  Conclusions Conclusions

Strathclyde research group overview Strathclyde research group overview 500km

Strathclyde research group overview Strathclyde research group overview Physics Department Strathclyde University Campus

Strathclyde research group overview Strathclyde research group overview  University of Strathclyde ~ 17,000 students University of Strathclyde ~ 17,000 students  Physics Department one of 8 within SUPA Physics Department one of 8 within SUPA  SUPA graduate school ~ 400 PhD students SUPA graduate school ~ 400 PhD students  Microwave & MM-wave research (~ 30 people) Microwave & MM-wave research (~ 30 people)

Scottish Universities Physics Alliance (SUPA) Members Aberdeen Dundee St Andrews Glasgow Edinburgh Strathclyde Heriot Watt West of Scotland

Research Themes in SUPA Research Themes in SUPA  Nuclear and plasma physics Nuclear and plasma physics  Particle physics Particle physics  Condensed matter & materials Condensed matter & materials  Photonics Photonics  Astronomy and astrophysics Astronomy and astrophysics  Physics applied to the life sciences Physics applied to the life sciences  Energy Energy

Physics Dept Nano- Optics Plasma science Computational Biomolecular Semiconductor Atoms Nonlinear & Chemical Spectroscopy Laser- Beams Photonics and Quantum Physics & Devices plasma-nuclear Optics (BCP) & Plasmas (SSD) (CNQO)

Strathclyde research group overview Strathclyde research group overview  Cathodes  Field emission: FEA Field emission: FEA  Explosive/plasma flare: Metal & Velvet Explosive/plasma flare: Metal & Velvet  Thermionic Thermionic  Pseudospark Pseudospark  Gun structures  Pierce, MIG, CUSP  Coherent h Coherent high power mm-wave generation  Slow wave: Dielectric Cherenkov, Cherenkov BWO  Fast wave: FEL, Gyrotron, CARM, Gyro-TWAs Gyro- BWOs, Superradiance (CRM & Cherenkov)

Examples of Strathclyde work on high power Examples of Strathclyde work on high power vacuum electronic mm-wave devices vacuum electronic mm-wave devices  Modelling – using MAGIC, KARAT, SURETRAJ, Modelling – using MAGIC, KARAT, SURETRAJ, OPERA, MICROWAVE STUDIO, COMSOL, VORPAL OPERA, MICROWAVE STUDIO, COMSOL, VORPAL  Electron beam research using thermionic, plasma flare, Electron beam research using thermionic, plasma flare, field emission array and pseudospark cathodes field emission array and pseudospark cathodes  Design, construction and measuring output of high Design, construction and measuring output of high power mm-wave vacuum electronic devices. Includes power mm-wave vacuum electronic devices. Includes research, design and construction of couplers, cavities, research, design and construction of couplers, cavities, converters, collectors and windows converters, collectors and windows  (i) high power mm-wave diagnostics (i) high power mm-wave diagnostics (ii) power supplies to drive the devices (ii) power supplies to drive the devices

Several different types of electron sources Several different types of electron sources MM-wave gyrotron driven by a field emission array (FEA) electron gun Physical Review Letters 77, 2320-2323, 1996

MM-wave gyrotron driven by a field emission array electron gun

Plasma flare cathodes

Mm-wave sources using a pseudospark generated electron beam Mm-wave sources using a pseudospark generated electron beam 20 800 15 600 10 400 5 200 Discharge Voltage [kV] 0 0 Current [A] -10 40 90 140 -5 -200 -10 -400 -15 -600 -20 -800 -25 -1000 -30 -1200 T ime [ns] Discharge Voltage Discharge Current 8 Beam Current by Rogowski Coil Beam Current by Faraday cup after T ungsten M

Cherenkov maser using high brightness electron beam from pseudospark source H ollow A no d e catho d e L aun ch in g ho rn S oleno id W aveguid e M icrow ave E lectro n beam D ielectric (alum ina)

Experimental setup of the 14-gap PS powered by a cable pulser and beam-wave interaction investigation

BWO Interaction Region W-band (75 to 110)GHz Ka-band (26.5 to 40)GHz W-band Aluminium positive former - Constructed in University Strathclyde - Copper is deposited - Aluminium dissolved in alkali solution Advantages: a) compactness (table-top size); b) simplicity (no B-field); c) flexibility; d) PRF operation

W-band (75-110 GHz) BWO 250 100 Microwave (mV) Current (A) 200 80 150 60 Voltage (kV) 100 40 50 20 0 0 -50 -20 -100 -40 -150 -60 -200 -80 -100 -50 0 50 100 150 200 Time (ns) Applied voltage Beam current Microwave pulse Time-correlated electron beam pulse (green) microwave pulse (red) and applied voltage pulse (blue)

1 mm aperture single gap pseudospark 1 mm aperture single gap pseudospark beam measurements beam measurements Measured small size (1 mm) beam easured small size (1 mm) beam M 1mm Aperture, 2 Disk, 10k 12 4.5 4 10 3.5 3 8 2.5 Beam Current (A) Voltage (-kV) 6 2 Voltage Beam Curren 1.5 4 1 2 0.5 0 0 -0.5 -178 -58 62 182 302 -2 -1 Time (ns)

Comparison of four types of electron beam source

206 GHz four cavity klystron 206 GHz four cavity klystron

Millimetre-wave free electron laser Millimetre-wave free electron laser 37 GHz Free Electron Laser 37 GHz Free Electron Laser

Model and basic equations of 2D Bragg FEL • Schematic diagram of two-mirror 2D-1D FEM interaction region • The 2D Bragg corrugation of the waveguide surface can be defined as: ϕ = + ϕ r ( z , ) R a cos( k z ) cos( m ) in , out 1 z • EM field can be represented by four partial waves: r r r r r − − ϕ ϕ • Schematic diagram of 2D distributed ﾢ ik z ik z iM iM = + + E A e A e + B e B e z z + - + - feedback circle M is the number of field variations along azimuthal co-ordinate ϕ . The A ± partial waves A ± propagate in ± z B ± B ± k + direction and B ± are near cut-off A ± k - A ± A ± B ± waves. The waves are coupled on the A ± corrugation if the following conditions B ± B ± are satisfied ′ = ≅ = k k k , m M z z z Physical Review Letters 96, art 035002, 2006

The FEL cavity configuration (a) 2D-2D Active length 860 mm (b) 2D-1D Schematic diagram of inner conductor with the corrugated structures (a) 2D-2D (b) 2D-1D Photograph of inner conductor

Measurements of 1D and 2D Bragg structures Co-axial 2D Bragg mirror - constructed by machining square chessboard corrugations on the outer surface of the inner conductor Frequency [ GHz ] Frequency [ GHz ] 35 36 37 38 39 40 35 36 37 38 39 40 0 -10 -10 TEM ↔ TEM -20 α≈ 0.08 α≈ 0.12 -20 TEM ↔ TM 01 -30 [dB] α≈ 0.11 [dB -30 ] Millimetre wave transmission through the Millimetre wave transmission through the 1D Bragg structure of length l z =30 cm 2D Bragg structure of length l z =4.8 cm

The spectra of a 7ns pump pulse at the input of the structure (thin line) and longitudinal electric fields (solid line) measured on the cavity’s axis in the time frame (10ns – 30ns) having length 4.8 cm. The spikes are associated with cavity eigenmodes having radial indices l =6 and l =7. The contour plots of the longitudinal electric ( E z ) and magnetic ( B z ) components of the field inside the cavity observed using the 3D code MAGIC. 1 S 0.8 0.6 0.4 0.2 0 75 80 85 90 95 100 105 E z B z

Pulsed power systems that drive Pulsed power systems that drive the 600 MW electron beam the 600 MW electron beam C onnection of the transmission line to the Assembly of the Marx pulsed power diode cathode via pressurised spark gap supply and the transmission line and matching resistors

The FEL experiment FEL apparatus to produce mm-waves - co-axial output horn and Mylar window of diameter 0.2m - matching resistors for capacitor bank powering solenoid - ignitron switch and fibre optic controlled trigger unit - solenoid of length 2.55m, diameter 0.3m with undulator inside - 3D X-ray shielded enclosure