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Electron-Transport Task Force report on studying the
feasibility of electron stopping experiments
MIT
This model
1 MeV e
C. K. Li for the Task Force
Annual Meeting of FSC
Laboratory for Laser Energetics
26-27 January, 2006
Can we do a cold-matter stopping experiment
that tests the validity of the new CELSA model?
•
The motivation for such a test is, in part, that the new model,
with blooming and straggling, predicts different energy
deposition than the traditional uniform model
•
There is no obvious quantitative path to such a verification.
The new model, with blooming and straggling, predicts
different energy deposition than the traditional uniform model
60.0
Uniform model
40.0
Density
(g/cm3)
r
rb = 1 μm
This model
20.0
0.0
3.00
2.00
300
1-MeV e
dE
1.00
(keV/μm3)
0.60
rb = 5 μm
0.00
0.40
0
0
5
10
15
Distance (mm)
20
25
rb = 10 μm
0.20
0.00
0.15
0.10
rb = 20 μm
0.05
0.00
0
5
10
15
20
Penetration (μm)
25
Qualitative similarities exist between new model and cold
matter stopping, as reflected in the strong Z dependence
1 MeV electrons
g/cm2
0.5
DT (Z=1)
Be (Z=4)
Cu (Z=29)
ΣB
0
ΣR
ρ<x>
0
0.7
0
g/cm2
ρR g/cm2
g/cm2
0.7
Quantitative differences exist between the new
model and cold matter stopping
dE/rs (MeV cm 2/g)
DT plasma, 10 eV, 0.25 g/cm3
B-S Pseudo-DT 0.25 g/cm3
40
30
20
10
0.01
0.1
1
Electron Energy (MeV)
10
Electron penetration in plasmas
is lower than in solids by ~30%
DT Plasma, 10 eV, 0.25 g/cm3
DT Plasma, 5 keV, 0.25 g/cm3
Pseudo-Solid DT, 0.2225 g/cm3
0
(g/cm 2)
10
350 μm
DT ice
-1
10
r<X>
-2
10
NIF Direct
Drive
-3
DT
10
350 μm
-4
10
10
100
1000
Energy (keV)
10000
1.7 mm
Consideration of a cold matter stopping experiment for
testing the CELSA model
• Would we be able to convincingly demonstrate that a proof of
cold matter stopping, beyond that which already exists in the
literature, would unambiguously prove the veracity of the
CELSA model?
• Given that the literature and work on electron stopping in cold
matter is so extensive and exhaustive, is there any experiment
that we could do, or lead for the ETTF or the FSC, that would
extend our understanding, in a fundamental way, of straggling
and blooming processes in cold matter?
There are no straightforward quantitative
collections between electron stopping in cold
matters and in plasmas
Stopping in cold matter
Stopping in plasma
Excitation/Ionization
Free electron
Bremsstrahlung
Pair production
Free electron
Bremsstrahlung
Pair production
Plasma oscillation
Scatterings
Scatterings
Quantum effects
Strong coupled
Screening effects --- Thomas-Fermi
Density effect
Quantum effects
Strong/weak coupled
Screening effects --- Debye
.......
.......
• While there are many common elements, NON counterpart physics exist
• Even for common elements, the level and scale are different
Can we do a cold-matter stopping experiment
that tests the validity of the new CELSA model?
•
The motivation for such a test is, in part, that the new model,
with blooming and straggling, predicts different energy
deposition than the traditional uniform model
•
There is no obvious quantitative path to such a verification.
ITS codes used and validated
I/I0
10
Energy (MeV)
Schonland/Varder
ITS
Scaled EXP
B-S
Geant4
1
R
Distance
0.1
10
100
1000
Range in Al (mg/cm 2)
Scaled=mean
10000
R0