Rutherford Appleton Laboratory Three mechanisms interact to cause ion acceleration in PW laser interactions • Relativistic electrons expelled by the ponderomotive pressure of light wave. To overcome the attractive electric field of the ions, E e > E c . The Coloumb energy E c is approximately E c 2 2 ne 2 l s R • Later the ions move due to Coloumb repulsion. E i 4 2 ne 2 R 2 R laser l s •Inductive electric field caused by the rapid change in the B field that accelerates ions and decelerates electrons. The energy gained by this process is • E i 8 e 2 n R 2
Rutherford Appleton Laboratory Three mechanisms interact to cause ion acceleration in PW laser interactions Relativistic electrons expelled by the ponderomotive.
Mar 28, 2015
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Rutherford Appleton Laboratory
Three mechanisms interact to cause ion acceleration in PW laser interactions
• Relativistic electrons expelled by the ponderomotive pressure of light wave. To overcome the attractive electric field of the ions, Ee > Ec . The Coloumb energy Ec is approximately
Ec 2 2 ne2lsR
• Later the ions move due to Coloumb repulsion.
Ei 4 2 ne2R2
Rlaser
ls
•Inductive electric field caused by the rapid change in the B field that accelerates ions and decelerates electrons. The energy gained by this process is •
Ei 8 e2n R2
Rutherford Appleton Laboratory
Sophisticated 3D simulations performed by Prof. S.Bulanov and co-workers has revealed that for linear polarisation case
the ion energy is px = 0.61mic
Conclusion: at intensities 31021 Wcm-2, ~1012 protons are accelerated with energies of several hundred MeV
3D computer simulations of ion acceleration process
Rutherford Appleton Laboratory
0.1
10
1000
105
107
109
1013 1015 1017 1019 1021 1023 1025 1027
Tan et al.CR39 resultsCR39 (Dec.98)Recent CR39 resultsLivermore
Ion
ener
gy (
keV
/nuc
leon
)
I2 Wcm-2µm2
Maximum ion energy vs I
PIC simulationS.V.Bulanov et alJETP Lett 71, 407 (2000)
a02 I2
PIC simulationT.Zh.Esirkepov et alJETP Lett 70, 82 (1999)
a0 I2
Prospects for GeV proton acceleration using PW lasers
Rutherford Appleton Laboratory
GeVlacm
cmnE x
e 20318
3
)(10
)(
The energy gain over the interaction length in a plasma wakefield is
When I2 >> 1018 Wcm-2m2, the radiation pressure is so large nearly all electrons are expelled from the photon wave-envelope, generating a “snow-
plough” in which the electron momentum gain is
202
0
20
4
1a
cmn
E
cn
Ep
e
c
ex
cm
eEa
00
00
provided the laser pulse fully interacts with the plasma (i.e. not diffracted)
Accelerating gradients 200 TeV/cm at 1026 Wcm2
Wakefield acceleration
e
cmEc
00
Nd:glass
20 fs seed laser stretched to 400 ps
1000ps
527 nm
3400 J
SHG
LBO1.5 cm
KDP3.8 cm
4452 J
41 %
LBO1.4 cm
KDP1.1 cm
KDP 0.8 cm
3400 J3400 J44 % 46 % 0.2 mJ 4 J
00.20.40.60.8
11.21.41.6
-600 -200 200 600
time (ps)
inte
nsi
ty (
a.u
.) signal out
depleted pump
Output signal and pump intensity profiles
100 PW
Intensity profile after compression
-80 -60 -40 -20 0 20 40 60 80
time (fs)
inte
nsi
ty
FWHM = 22 fs
(0.3 J/cm2)
Rutherford Appleton Laboratory
Ideas for EW lasers (Dr I.N.Ross)
Rutherford Appleton Laboratory
Future Upgrade OptionsGiven Some Technology DevelopmentGiven Some Technology Development
SHG Pump Dielectric Gratings 1μm Output 50cm KDP
F/1 Focusing0.3 EW 1025 W/cm2
THG Pump Dielectric Gratings0.5μm Output 50cm KDP
F/1 Focusing 0.6 EW 1026 W/cm2
Multi OPCPA >1 EW >1026 W/cm2
Rutherford Appleton Laboratory
• The VULCAN PW upgrade is nearly completion - first experiments to university users scheduled November 2002 - laser wakefield accelerator studies
• >100 MeV protons and >1GeV heavy ions expected
• Future upgrades to multi-PW levels are being actively pursued
• The CLF is investigating new designs for average and peak power lasers required for accelerator and fusion applications
Summary
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