Post on 08-Jul-2018
1/7/2008
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Ion Beam Heating and Diagnostics Ion Beam Heating and Diagnostics -- II
Frank Bieniosek
Winter School on Warm Dense Matter PhysicsJanuary 10-16, 2008
Lawrence Berkeley National Laboratory and University of California, Berkeley
The Heavy Ion Fusion Science Virtual National LaboratoryWork performed for the US DOE under contract numbers DE-AC03-76SF00098 and W-7405-ENG-48.
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CollaboratorsLBNL: J. Duersch, E. Henestroza, M.A. Leitner,
B.G. Logan, R. M. More, P. Ni, P.K. Roy, P. A. Seidl, A. B. Zylstra
LLNL: J. J. BarnardU. of Electro-communications, Tokyo: H. YonedaPPPLUC BerkeleySandiaGSI DarmstadtTU DarmstadtIPCP ChernogolovkaITEP Moscow
NDCX II 3 - 6 MeV, 0.03 μC
~2010
NDCX II 3 - 6 MeV, 0.03 μC
~2010
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Outline of talk
Heavy Ion Fusion Science experiments:
The physics of compressing beams in space and time
-- Ion-driven WDM
-- Accelerator technology
-- Drift compression and final focus
Warm Dense Matter (WDM) experiments
-- WDM target chamber and diagnostics
-- Experimental plan
-- GSI experiment with porous targets
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Ion beams provide an excellent tool to generate homogeneous, volumetric warm density matter.
Short pulseion beam
Example: Ne+
Enter foilExit foil
Al target• Warm dense matter (WDM)– T ~ 0.1 to 10 eV– ρ ~ 0.01 -1 * solid density
• Techniques for generating WDM– High power lasers– Shock waves– Pulsed power (e.g. exploding wire)– Intense ion beams
• Some advantages of intense ion beams– Volumetric heating: uniform physical
conditions– High rep. rate– Any target material
GSI
WDM strategy: maximize uniformity and the efficient use of beam energy by placing center of foil at Bragg peak.
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Ion beam driven HEDP/WDM has unique characteristics.
Precise control of energy deposition
Large sample sizes compared to diagnostic resolution volumes (~ 1's to 10's μ thick by ~ 1 mm diameter)
Uniformity of energy deposition (<~ 5%)
Ability to heat all target materials (conductors and insulators, foams, powders, ...)
Pulse long enough to achieve local thermodynamic equilibrium
A benign environment for diagnostics
High shot rates (10/hour to 1/second)
Potential for multiple beamlines/target chambers
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BuncherFinalfocus
Chambertransport TargetIon source
& injector Accelerator
HIF Driver WDMBeam ~40 kA
(~4GeV)~30A(3-6MeV)
Beamnumber
~120 1
Focal spot
2 mm 1 mm
Pulse length
~10 ns ~1 ns
HIF Driver
One concept of WDM facility: NDCX-II
The HIF Driver/WDM experiments require beam compressions to hit mm-sized spot with ns pulse.
NDCX II 3 - 6 MeV, 0.03 μC
~2010
NDCX II 3 - 6 MeV, 0.03 μC
~2010
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HIFS-VNL accelerators for WDM experiments
NDCX II 3 - 6 MeV, 0.03 μC
~2010
IB-HEDPX (with CD0)5 - 15 year goal 20 - 40 MeV, 0.3 - 1.0 μCWDM User facility
NDCX I
0.4 MeV, 0.003 μC
HCX
1.7 MeV, ~0.025 μC
Today:
Future
10 kJ Machine for HIF
10 - 20 year goal
Target implosion physics
Soon
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Neutralized beam transport (NTX) & drift compression (NDCX) can provide ~mm spot with ~nsec pulse.
●NDCX: In neutralized drift compression beam is longitudinally compressed by imposing a linear head-to-tail velocity tilt to a drifting neutralized beam and producing a pulse duration of several ns.
●NTX: In beam neutralization, electrons from a plasma or external source are entrained by the beam and neutralize the space charge sufficiently that the pulse focuses on the target in a nearly ballistic manner to a small spot.
NDCX
00.20.40.60.8
11.21.41.61.8
2
0 25 50 75 100Distance (cm)
RM
S R
adiu
s (c
m)
Perfect Neutralized
Vacuum transport:un-neutralized
CAP neutralized
Time
Cur
rent
(log
sca
le)
NTX
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NDCX-1 has demonstrated factor ~70 pulse compression, and simultaneous transverse and longitudinal focusing
120 ns section of pulsecompressed to ~ 2 ns
Velocity tilt accelerates tail, decelerates head
Neutralizing plasma is required for final focus
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Concentration of ion beam using funnel (cone) provides a new path to increasing energy density on target.
• Cone acts as grazing incidence mirror. Beam particle reflection coefficient is 80% at 89° incidence.
• Space charge neutralization of beam electric field, electron production.
• 40% measured increase in intensity with 200 mrad (79°) gold cone.
• Greatly improved beam concentration in grazing incidence and scattering geometries may be possible.
Backscatter for 350-keV K+, 2-MeV Li+ on gold
0
0.2
0.4
0.6
0.8
0 20 40 60 80
Angle of Incidence (degrees)
Frac
tion
of b
eam
ions
ba
cksc
atte
red
WDMTarget
Converging beam
Gold cone
0.0
0.1
0.2
0.3
0.4
0.5
1.0 2.0 3.0 4.0 5.0
Radius/(Target Radius)
Frac
tion
of E
nerg
y Sc
atte
red
to T
arge
t
1
1.1
1.2
1.3
1.4
1.5
1.6
1.7
Enha
ncem
ent o
f ene
rgy
to
targ
et
75º 80º 85º 70º
TRIM calculations for a single reflection
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Near-term experiments provide opportunity to gain experience with diagnostics on WDM targets.
Probe laser
Self emission (out of plane)
Probe laser transmission
Current input
Voltage taps
ION BEAM
Sapphire substrate
SAMPLE <1-micron
Initial diagnostics will include
– Visible light emission, especially optical pyrometer
– Electrical conductivity, optical absorption provide information on target temperature and phase transitions
– Stopping power
– Laser, VISAR probes
Probe laser specular reflection
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Front view of the octagonal shaped target chamber. The target ismounted in the exact center of the chamber with the ports aimingat the target location.
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Initial set of target experiments on NDCX-1 will take place in next few months.
• Initial set of targets is on hand
• Deposited layers on sapphire substrate– Al: 350 nm (1.2 x range)– Au: 150 nm (1.4 x range)– W: 150 nm (1.5 x range,
for pyrometer calibration)
• Free-standing foils– 350-nm Al– 150 nm Au
Energy Density Vs. Thickness
0
0.05
0.1
0.15
0.2
0.25
0.3
0 0.5 1 1.5 2
Thickness / RangeEn
ergy
Den
sity
[keV
/Ang
stro
m]
WAlAu
Average for given foil thickness
TRIM calculations
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HYDRA simulations of the NDCX-1 experiment2A, 2 ns, 1 mm diameter, 350 keV K+ beam will heat up a 350 nm solid aluminum target to ~ 0.16 eV, and a 150 nm solid gold target to ~ 0.2 eV. The simulation assumes a uniform transverse beam profile and EOS from QEOS for aluminum and SESAME tables for gold.
The (transverse) non-uniformity of the profiles is due to the small number of sampled beam rays.
BEAM
Temperature profile Axial velocity profile
BEAM
Al
Au
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Target temp.
NDCX-1 or HCX
NDCX-2
Transient darkening emission and absorption experiment to investigate previous observations in the WDM regime
Measure target temperature using a beam compressed both radially and longitudinally
Thin target dE/dx, energy distribution, charge state, and scattering
Positive - negative halogen ion plasma experiment
Two-phase liquid-vapor metal experiments
Critical point measurements
Low (0-0.4 eV)
√
Low √
Low √
>0.4 eV √ √
0.5-1.0 √ √
>1.0 √
We have begun a series of warm dense matter experiments that can begin on NDCX-I at Temperature < 1 eV.
time
Also: low density porous targets, wire arrays, etc.
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Transient optical transmission experiments in quartz fiber performed on HCX (1 MeV K+ ion beam).
Optical transmission experiment: look for difference in fiber transmission with and without beam.
Initial experiment shows possible weak effect at 10 μs, long wavelengths
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Porous target beam-driven experiment Dec. 2006 at GSI.
•Replace target foil with porous material.•Study effect of pore size on target behavior using existing diagnostics.•HIFS-VNL targets: Au, 50 nm, Cu, 50 micron.
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Streak camera data shows expansion of the targets solid/porous gold and copper targets.
Gold
Copper
Pyrometer ‘gray’ temp.
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Pyrometer data for gold targets.
• Solid gold is initially heated 1000 deg. hotter than porous gold. The solid gold also expands into the sapphire window much more rapidly than the porous gold (shots 13 and 14). At late times the temperatures of the two targets come together. (T-boil = 2435 K)
2500
3500
4500
5500
6500
7500
8500
14.00 14.50 15.00 15.50 16.00
time [microsec]
Tem
p [K
]
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
emis
sivi
ty
13 T
14 T
13 e14 e
Porous gold
Solid gold
Beam pulse
Pyrometer ‘gray’ temp.
front: 1.9 km/s
1.6 km/s
center 1.1 km/s
1.55 km/s
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Conclusion
• Ion beams provide a new tool to generate homogeneous, volumetricWDM.
• Development plan uses existing accelerators and pulse compression technique developed in HIFS-VNL. We have built a target chamber.
• We are developing and fielding target diagnostics on the target chamber (to be described by Pavel Ni).
• Initial experiments performed at GSI; experiments specified at LBNL; initial set of targets are in hand; target modeling is underway.