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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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View of the new HIFS-VNL target chamber facility installed on NDCX-I.

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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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WARM DENSE MATTER EXPERIMENTS TARGET CHAMBER

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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.