Slide 1 - Cockcroft Institute by yurtgc548

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									    RF for Really Forceful
        Acceleration

      Dr. Rebecca Seviour
        Cockcroft Institute
Dept Engineering, Lancaster University
                Morpho menelaus




                                                     200 nm




The inverse of a Radiative process is Acceleration
               Electromagnetic Fields




Electron   Lines
             of
           force
                 Travelling Wave
                   Structures
Iris loaded
Accelerator




                                   Twisted Waveguide
                                      Accelerator




      Dielectric loaded
        Accelerator
Particle
Source




           Series of drift tubes alternately connected oscillators.
Standing Wave Structures
               RF Cavities:
           Important Quantities


Cavity Quality factor (Q) = Energy Stored
                             Energy Lost



     Accelerating Gradient
Normal Cavity @ 500 MHz

Rs = 5.9 m
Q = 44000

@ 1 MV ~ Ploss = 116 kW ~ 20 W/Cm2

Re-entrant Cavities

Increase Magnetic Volume
       Decrease B on Surface
             Reduce Loss (I2R)

Can have high surface E resulting in
Field emission.
Superconducting Cavity @ 500 MHz

Rs ~ 200 n
Q ~ 105

@ 1 MV ~ Ploss = 4W


                      Iris rounded avoid reentrancy
                               Reduced surface E
                                     Reduced field emission
                               Reduced Multipactor
Workshop on High Gradient RF
 Argonne National Laboratory          Issues:
                                   Surface Finish
      October 7-9, 2003




                               Field Emission
                                       (2004)




   Plasma Spots                                 Cracking   Hot Spots
Skin Depth
Cu @ 200MHz ~ 4.6 µ
Nb @ 1.3 GHz ~ 0.08 µ
(SLAC)
Photonic Band Gap Structure
                            Plasma Acceleration




Plasma acceleration has several types depending how the plasma wave is formed:

Plasma Wakefield acceleration: Plasma wave formed by an electron bunch

Laser Wakefield acceleration: Laser pulse is used to form a plasma wave.

Laser Beat-wave acceleration: Plasma wave arises based on different frequency
generation of two laser pulses.

Self-modulated laser Wakefield acceleration: Leave for another day

								
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