High Energy Plasmas

1
Supporting research on accelerators
Alan Phelps
2
Supporting research on accelerators
Path by which part of the Strathclyde Physics
Dept is supporting research on accelerators

• High energy neutral plasmas
• High energy non-neutral plasmas
• - intense relativistic electron beams
• Electromagnetic wave particle energy
  exchange
• Acceleration deacceleration
• High current particle beam production
• High field breakdown
• High power RF and microwave sources
• Novel compact plasma accelerators

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Supporting research on accelerators

• High power RF and microwaves are needed to feed
• accelerating cavities and provide high field
  gradients

Does the UK have a pool of RF accelerator
expertise or just a damp patch?

• The UK Faraday Partnership in High Power RF was
  formed
• about four years ago funded by PPARC and DTI
• Within the Faraday Partnership an Accelerator
  Club meets
• regularly to discuss RF accelerator issues
• Strathclyde is a foundation/core partner. Number
  of
• associated partners now 50 - mostly RF
  companies
• MSc in High Power RF Science and Engineering
  started
• in 2004 - first Strathclyde graduates in October
  2005

4
Rebirth of accelerator science in the UK

• New UK accelerator science centres since 2000
• Cockcroft Institute (Daresbury, Lancaster,
  Liverpool, Manchester)
• John Adams Institute for Accelerator Science
• (Oxford, RHC London)
• ASTeC (CCLRC)
• HPRF Faraday Partnership Accelerator
  Club-includes Strathclyde
• The LC-ABD (Linear Collider Accelerator and Beam
  Delivery) consortium
• Linear Collider UK Council - includes Strathclyde
• MICE

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Experimental and computationalintense
relativistic electron beams

• Electron cyclotron masers
• CARMs gyro-amplifiers
• Cherenkov interactions
• FELs
• Pseudospark high brightness sources

6
Wave electron beam interactions
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High power RF/microwave source research

• Strathclyde Gyro-TWA

1.1MW output power (TE11), 21 frequency
bandwidth (3dB points) centred at 9.4GHz,
Saturated gain 37dB, linear gain 48dB
8
Behaviour of electron beam through a cusp
transition
Simulated electron beam trajectories using MAGIC
9
CVD Diamond RF window.
Thickness 0.130 /- 0.010 mm
10
Two dimensional photonic band gap structures
Model and basic equations

• Schematic diagram of 2D feedback circle

• The 2D Bragg corrugation of the waveguide
  surface can be defined as

• RF field can be represented in form of four
  partial waves

M is the number of the field variations along
azimuthal co-ordinate ?. The partial waves A?
propagate in ? z direction and B? are near
cut-off waves. The waves are coupled on the
corrugation if the following conditions are
satisfied
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Transmission measurements of 1D and 2D Bragg
structures

• First co-axial 2D Bragg mirror constructed by
  machining square chessboard corrugations on the
  outer surface of the inner conductor

Frequency GHz
Frequency GHz
Frequency GHz
dB
??0.12
TEM?TM01 ??0.11
TEM?TEM ??0.08
dB
RF power transmission through the 2D Bragg
structure of length lz 4.8 cm
RF power transmission through the 1D Bragg
structure of length lz 30 cm
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2D Free Electron Source Relevant to CLIC
Schematic diagram of FEM experimental set-up (I)
Marx Pulsed Power (MPP) supply (II) transmission
line (III) Spark gap HCA (IV) guide solenoid
coaxial drift tube which includes the FEM
interaction space
II
I
III
IV
c)
a)
b)
d)
The photograph of the (a) MPP supply and the
transmission line (b) guide solenoid capacitors
support structure c) HCA with coaxial electron
drift tube (d) HCA fully assembled with guide
solenoid, beam diagnostics and X-ray shielding
13

• Strathclyde 2-D FEM Operating Parameters

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Novel electron beam sources
A pseudospark is a special hollow cathode
discharge
Low pressure (10-100 Pa, 70-700mtorr for a gap
separation of several mm)
15
Brightness as a function of current density for
various electron beam sources
The top right hand corner of the above diagram
indicates the highest brightness combined with
the highest current density
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The Plasma Afterburner
LENSES

• WFA Wake Field Accelerator
• Double the energy of Collider with short plasma
  sections before the interaction region
• 1st half of beam excites wake - decelerates to 0
• 2nd half of beam rides wake - accelerates to 2 x
  Eo
• Make up for luminosity decrease by focusing in a
  final plasma lens

50 GeV e-
50 GeV e
e- WFA
eWFA
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Wave electron beam interactions

• RAE impact - some publications

General Journals Phys. Rev. Lett., 77, 1492-1495
(1996) Phys. Rev. Lett., 77, 2320-2323
(1996). Phys. Rev. Lett., 77, 4836-4839
(1996) Phys. Rev. Lett., 78, 2365-2368
(1997) Phys. Rev. Lett., 81, 5680-5683
(1998) Phys. Rev. E, 60, 935-945 (1999) Phys.
Rev. E, 60, 3297-3304 (1999) Phys. Rev. Lett.,
84, 2393-2396 (2000) Phys. Rev. Lett., 84,
2746-2749 (2000) Appl. Phys. Lett., 80, 1517-19
(2002) Phys. Rev. E, 68, 066613, 1-8 (2003) Phys.
Rev. E, 70, 046402, 1-8 (2004) Phys. Rev. Lett.,
92, 118301, 1-4 (2004)
Specialist Journals IEEE Trans Plasma
Sci., 24, 770-780(1996) Phys. Plasmas, 4,
2285-2291 (1997) IEEE Trans. Plasma Sci., 26,
508-518 (1998) IEEE Trans. Plasma Sci., 26,
375-382 (1998) Phys. Plasmas, 7, 5195-5205
(2000) Phys. Plasmas, 7, 4280-4290 (2000) IEEE
Trans. Plasma Sci., 28, 1615-1619 (2000) Phys.
Plasmas, 9, 2798-802 (2002) Phys. Plasmas,10,
4494-4503 (2003) IEEE Trans. Plasma Sci., 32,
233-239 (2004). Cont. Plasma Phys.,44, 382-387
(2004) IEEE Trans. Plasma Sci., 32, 929-933
(2004). J. Plasma Phys., 71,675-693 (2005)

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Conclusions

• Particle physics research drives need for higher
  energy and greater beam brightness. What is ahead
  is hard but should be tackled. Need for
  research on improved RF sources and development
  of novel acceleration.
• Near to medium term
• Linear collider with low frequency RF driven
  superconducting cavities
• Neutrino factory driven by high power low
  frequency RF
• Medium term
• Linear collider with high frequency microwave
  high field gradient normal conducting cavities
• Longer term
• Accelerators with plasma after-burners. Novel
  ultra-high
• gradient, high frequency acceleration methods