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![Page 1: James Holloway University College London, London, UK PhD Supervisors: Professor Matthew Wing University College London, London, UK Professor Peter Norreys.](https://reader035.fdocuments.us/reader035/viewer/2022062401/5a4d1af07f8b9ab05997d923/html5/thumbnails/1.jpg)
James HollowayUniversity College London, London, UK
PhD Supervisors:
Professor Matthew WingUniversity College London, London, UK
Professor Peter NorreysUniversity of Oxford, Oxfordshire, UK
Central Laser Facility, Rutherford Appleton Laboratory, UK
Bright Radiation Source based on
Plasma-micro-bunched Diamond Beam
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Image Source: http://www.veqter.co.uk/residual-stress-measurement/synchrotron-diffraction
Synchrotron Facilities Worldwide
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Image Source: http://www.veqter.co.uk/residual-stress-measurement/synchrotron-diffraction
Synchrotron Facilities Europe
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Image Source: http://www.veqter.co.uk/residual-stress-measurement/synchrotron-diffraction
Synchrotron Facilities Europe
330 mm
26 mm
14.6 mm
120 mm
52 mm
5.4 mm
2.4 mm
13.2 mm PETRA III
Electron beam lengthProton beam length
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• Use existing facilities’ beams to drive PWA• Accelerate higher energy beams using PWA• Generate harder X-rays from 3rd generation light sources
The Goal
σideal = λp / (π√2)
Need beam lengths of:
σz < 1 mm
• These beams are too long to drive effective wakefields
• Existing beam lines have limited space• Longitudinal compression via magnetic
chicanes takes considerable space and expense
The Problem
• Micro-bunch beams to make them an effective wakefield driver
The Solution
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• Strong transverse kick from laser wakefield
• Propagate beam through vacuum
• Pass micro-bunches into second plasma stage when on-axis number density maximised
Micro-Bunching Via Wakefield Kick and Drift Space
Long electron beamLed by laser
Neutral plasma
+
++
+
+
+---
+
Vacuum
Micro-bunched driver beam.
Secondplasma
cell
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Beam number density. 51 mm of propagation
• E = 300 MeV • εp = 0• σz = 0.6 cm • σr = √2 / kp
• Q = 0.1 nC
Electron beam
• ne = 2.84e22 m-3
• λp = 200 um• Er = 1 GVm-1
The Plasma
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3.5 x 1019
3.1 x1019 m-3
On axis number density
enhanced by ~ an order of magnitude
Beam number density. 51 mm of propagation
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Diamond Booster Param• E = 300 MeV • εp = 0• σz = 0.6 cm • σr = √2 / kp
• Q = 0.1 nC
Electron beam
2 31
First Plasma Cell (3.5 mm)
Vacuum(48.5 mm) Second Plasma Cell
(> 100 mm)
1) The long beam given transverse momentum by strong wakefield.
2) Micro-bunches form as half e- defocused, other half focused
3) At the moment the beam has achieved best micro-bunching*, pass into the second plasma cell.
The ‘Drift Space’ Design
• First plasma cell analogous to lens
• Longer first cell results in a stronger focus and shorter vacuum needed
• However strong focus results in higher emittance micro-bunches
• ne = 2.84e22 m-3
• λp = 200 um• Er = 1 GVm-1
The Plasma
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Run♯ Cell Length (mm)
Vacuum Length(mm)
Peak Nd @ 2 m (e19 m-3)
5 2.5 65.5 4.09
6 3.0 57.0 4.00
7 3.5 48.5 3.90
8 4.0 42.0 3.73
9 4.5 37.5 3.80
10 5.0 32.0 3.64
No vacuum ∞ 0.0 0.13
Effects of First Cell length
200
200 mm
Single cell design. Electrons focused too hard and lost
from micro-bunch
Two-Stage design results in stable micro-bunches
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The Diamond light source at RAL uses a 3 GeV electron beam to generate soft x-rays.
Beam length: σz = 26 mm
Too long to effectively drive a wakefield! (λp ~ 100um).
A proof of principle experiment has been proposed to micro-bunch the beam using a laser-driven wakefield. The beam can then drive a PWA to:
• Create a higher energy electron beam• Create a poor mans FEL using betatron oscillations within the wake
• E = 3 GeV • ε = 140 nm rad • σz = 26 mm • Q = 2 nC
Diamond Booster Beam
The Diamond Light Source
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Linac
Pictures by Michael Bloom, Imperial College.
90 KeV
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Booster
Pictures by Michael Bloom, Imperial College.
158m circumference
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The Diamond ExperimentServeral slides of tour of Diamond!
Transfer Line
Pictures by Michael Bloom, Imperial College.
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Diamond Booster Param• E = 300 MeV • εp = 0• σz = 0.6 cm • σr = √2 / kp
• Q = 2 nC
Electron beam
1) The long beam given transverse momentum by high amplitude wakefield.
2) Micro-bunches form as half e- defocused, other half focused.
3) At the moment the beam has achieved micro-bunching*, pass into the second plasma cell.
The ‘Drift Space’ Design
• ne = 1.11e22 m-3
• λp = 300 um• Er = 1 GVm-1
The Plasma
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A B
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Acknowledgements
Professor Matthew WingUniversity College London, London, UK
Professor Peter NorreysUniversity of Oxford, Oxfordshire, UK
Central Laser Facility, Rutherford Appleton Laboratory, UK
Professor Robert BinghamUniversity of Strathclyde, Glasgow, UK
Central Laser Facility, Rutherford Appleton Laboratory, UK
Doctor Raoul TrinesCentral Laser Facility, Rutherford Appleton Laboratory, UK
Computing resources provided by STFC’s e-Science facility, SCARF and DiRAC.
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• Many existing particle beam facilities • Can treat these beams and make them
suitable to drive PWA• Two-stage drift-space design achieves
this over short distances• PWA can generate higher energy
electrons and in turn generate harder X-rays form existing infrastructure
• PWA can generate X-rays directly from micro-bunch oscillations
• Ion motion can be a problem!
Thank you for listening
Concluding