octoberfest! october 2014 peter tudor john adams institute for accelerator science laser wakefield...
TRANSCRIPT
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Octoberfest!October 2014
Peter TudorJohn Adams Institute for Accelerator Science
Laser Wakefield Acceleration
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Octoberfest 2 Peter Tudor, JAI
• Setting the scene– Conventional accelerators
• LWFA scheme and limitations• Multiple Pulse LWFA scheme• Fibre Lasers • FET Proposal• Future applications
Points to cover
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Octoberfest 3 Peter Tudor, JAI
• Are able to produce high beam energies
• But:- Typically large structures
- Large footprint
- Expensive to build - Expensive to run - Requires large amount of maintenance
work- Not practical for proliferation of tech
Conventional accelerators
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Octoberfest 4 Peter Tudor, JAI
• High intensity laser pulse is fired into a plasma, causing large electron displacement– Via ponderomotive force
• This leads to a wakefield, forming a large gradient of electric field
• This can be used to accelerate electrons
LWFA Scheme
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Octoberfest 5 Peter Tudor, JAI
• Oscillating electrons in a plasma lead to a wakefield
What is a wakefield?
Dr. Warren Mori, on behalf of SciDAC's Advanced Accelerator Group - http://www.scidacreview.org/0602/html/sa2.html
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Octoberfest 6 Peter Tudor, JAI
• Large accelerating gradients– Up to 1GV / cm – 3 orders of magnitude larger than RF
• Have the potential to revolutionise accelerator technology.– Smaller accelerators– Cheaper accelerators
What is the motivation for LWFA?
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Octoberfest 7 Peter Tudor, JAI
• Current laser systems which drive LWFA are capable of high peak powers (J’s in 10’s fs), but:– Low repetition rate ( ≤1Hz)– Low wall plug efficiency ( ≤0.1%)
• Rep rate is limiting for applications and experiments– E.g. FELs and medical diagnostic etc
• Repetition rate and efficiency need to be improved for LWFA to be viable
Limitations of current LWFA schemes
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Octoberfest 8 Peter Tudor, JAI
Multiple Pulse LWFA
Time
𝜏 ≈10′ 𝑠𝑝𝑠
Time
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Octoberfest 9 Peter Tudor, JAI
– (100’s fs)– – Energy is delivered over 100s of pulses
rather than a single pulse• Pulses resonantly excite a wakefield
– Can then use smaller, cheaper optical components. (Lower peak power)
Multiple Pulse LWFA
Pow
er
Time
τp
τd
ε
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Octoberfest 10 Peter Tudor, JAI
Fibre lasers
• Fibre lasers have:– High repetition rate, MHz– High wall plug efficiency, = 20 – 30%– Higher average power than single shot
systems
• The limitation– Low pulse energy
http://www.rp-photonics.com/photonic_crystal_fibers.html
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Octoberfest 11 Peter Tudor, JAI
• Future Emerging Technologies (FET) proposal has been submitted as a partnership between Oxford, Jena, Imperial, UCL and ESRF.
• Intention is to build a demonstration LWFA with:– Electron energies up to 250MeV – Repetition rate of 10kHz. – Scalable architecture
• Application to EPSRC for funding to investigate MP-LWFA by Oxford and Imperial
FET Proposal
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Octoberfest 12 Peter Tudor, JAI
Laser architecture
Scalable
Laser architecture courtesy of Jena group
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Octoberfest 13 Peter Tudor, JAI
Electron bunch production
http://www.aist.go.jp/aist_e/latest_research/2004/20040812/20040812.htmlEnergy Technology Research Institute (ETRI) of the National Institute of Advanced Industrial Science and Technology (AIST)
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Octoberfest 14 Peter Tudor, JAI
Comparison of light sources
http://arxiv.org/abs/1401.7874v1 Multi-Pulse Laser Wakefield Acceleration: A New Route to Efficient, High-Repetition-Rate Plasma Accelerators and High Flux Radiation Sources
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Octoberfest 15 Peter Tudor, JAI
Comparison of light sources
MP-LWFA driven FEL pulses (TGU)
MP-LWFA betatron pulses (1.3GeV)
ID9 beam line, ESRF
Diamond- Low α mode
LLNL FEL http://arxiv.org/abs/1401.7874v1 Multi-Pulse Laser Wakefield Acceleration: A New Route to Efficient, High-Repetition-Rate Plasma Accelerators and High Flux Radiation Sources
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Octoberfest 16 Peter Tudor, JAI
• Allow the proliferation of compact and efficient accelerators capable of GeV electron energies
• Ideal for use in universities– Good tool for education and research
• Use in hospitals – High resolution X-ray imaging
Future Applications
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Octoberfest 17 Peter Tudor, JAI
Any questions!
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Octoberfest 18 Peter Tudor, JAI
Future Applications
Paul Scherrer Institute, ETH Zurich – KS Baden
• Example - MammogramAbsorption imaging Phase contrast imaging
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Octoberfest 19 Peter Tudor, JAI
• The core is doped with a Rare Earth ion species. (Erbium, Ytterbium)
• The ion can be excited using a ‘Pump’ laser. – (Charging up the medium)
• The energy is liberated by the ‘Seed’ laser. – (Discharging the medium)
• This creates a light amplifier in the core of the Fibre itself.
Doped Fibres
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Octoberfest 20 Peter Tudor, JAI
Doped Fibres
Pump Laser
Seed Laser
No. Excited atoms
Max Max Max
Min Min Min
Doped Fibre
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Octoberfest 21 Peter Tudor, JAI
• Why would we use this?– Allows more pump energy to be
transferred to doped core
– Very high peak-power polarised laser pulses (GW, TW ranges)!
Photonic Crystal Fibres