# Presentation: 468353

## Robust Heavy Ion Fusion Target

- Shigeo KAWATA
- Utsunomiya Univ. Japan
- U.S.-J. Workshop on HIF
- December 18-19, 2008
- at LBNL & LLNL

## Acknowledgments

- Thanks for Collaborations with Grant, John & Friends in VNL
- for WDM/HEDM physics + HIF with wobblers!
- Colleagues in HIF Japan,
- Sasho, Jacob
- JSPS & MEXT, Japan

## / High d ~ 30~40%

**/ High ********d**** ~ 30~40%**
**/ Robust driver with a high rep. **
**/ Beam handling**
**/ Spherical target with a hybrid implosion**
**/ Robust implosion**

## Advantages of HIF Scheme

- / High efficiency ~30~40%  => Gain~30 with ~10Hz operation
- / Simple energy deposition
- / Robust against R-T instability <= large density gradient

**Large scale**

**Small scale**

## Without foam

- Incident beam
- 	: 34 [ns]  7 [MJ]
- Nonunifomity
- 	: 2.0 [%]
- Maximum incidence angle
- 	: 30 [degree]

- With foam
- Incident beam
- 	: 34 [ns]  7 [MJ]
- Nonunifomity
- 	: 4.0 [%]
- Maximum incidence angle
- 	: 40 [degree]

- No 11

- Comparison of
- 	space profiles of density

**The Density Valley is Widened by inserting the foam.  **

## With foam

-  of the R-T instability with foam

- No 20

- Incident beam
- 	: 34 [ns]  7 [MJ]
- Maximum incidence angle
- 	: 40 [degree]

**Estimation of the R-T Instability growth**

## Introduction - Problems of ICF -

- Wobbling HIBs
- => time-dependent energy deposition E
- => time-dependent non-uniform acceleration: g

- Flow of inertial confinement fusion

**Notes:**
Etc=and so on.

## The Rayleigh-Taylor Instability (RTI)

- When a low density fluid supports a high density one under gravity, the fluid instability is caused.
- This instability is so called the Rayleigh-Taylor Instability (RTI).

- The growth rate of the RTI is

- gravity

- ρ1<ρ2

- high density

- low density

- 2π/k

- 2π/k

## RTI induced by non-uniform gravity

- A non-uniform acceleration (gravity) is generated by non-uniform illumination of heavy ion beams.
- Because the beam number is finite.

- The gravity is expressed by the constant term and the non-uniform term, in this study.

- ion beam

- target

## RTI induced by non-uniform gravity

- time

## Simulation model - constant gravity -

- gravity

- ρ

**Notes:**
This figure shows the density distribution of the fluid in two dimensional.

## Simulation result - constant gravity -

- density

- t=0~6 [1/γ]

- gravity

- The RTI is grown by the initial unstable density and the non-uniform gravity distributions.

## HIB axis can be oscillated with a high frequency-> Control of RTI - Oscillating gravity -

- From the equation, when the gravity oscillation frequency *f*  increases, the RTI perturbation velocity *w* decreases.

## Control of RTI - Oscillating gravity -

- The RTI perturbation velocity is approximately written by <-.

- From the equation, when the gravity oscillation frequency *f* is increased, the RTI perturbation velocity *w* decreases.

## Single Mode Simulation [constant gravity]

- vorticity

- density

- t=0~6 [1/γ]

## Single Mode Simulation [constant gravity]

- t=5 [1/γ]

- density

- vorticity

## Single Mode Simulation [oscillation gravity]

## Single Mode Simulation

- density

- vorticity

- oscillation (γ[Hz])

- t=5 [1/γ]

- t=9 [1/γ]

- t=7 [1/γ]

## Single Mode Comparison  (γt=5)

- Single Mode Comparison  (*γt*=5)

- density

- vorticity

- oscillation
- (γ[Hz])

- constant

## Single Mode Comparison (passage of time)

- constant

- f=1[γ]

- f=10[γ]

- constant

- f=1[γ]

- f=10[γ]

- constant

- f=1[γ]

- f=10[γ]

- Single Mode Comparison (passage of time)

## Multi Mode Simulation [oscillation gravity]

- parameter

- gravity

- gravity

## Multi Mode Comparison  (t=5 [1/γ])

- density

- vorticity

- oscillation
- (γ[Hz])

- constant

## Illumination of Wobblers

**Illumination of Wobblers**
**Parameters**** **
- Pb+ ion beam
- Beam number : 12, 32
- Beam particle energy : 8GeV
- Beam particle density distribution : Gaussian
- Beam temperature of projectile ions : 100MeV with the
-                                                            Maxwell distribution
- Beam emittance : 1.0 mm-mrad
- External pellet radius : 4.0mm
- Pellet material : Al

## Rotation radius  1.5mm

- 1.5~3.0mm

- Rotation radius

- Pellet radius
-          4.0mm

- Beam radius
-     1.5~4.0mm

- Rotation radius  2.0mm

- Rotation radius  3.0mm

## Rotation radius 1.9mm

- Beam radius     2.6mm
-                          2.3 %

- Rotation radius 3.0mm
- Beam radius     3.2mm
-                          3.2 %

## 32 beams

- Rotation radius 1.9mm
- Beam radius      2.6mm
-                           2.32%

- 32-HIBs illumination system

- 32-beam

- 12-beam

- 12 beams
- Rotation radius 1.9mm
- Beam radius      2.6mm
-                           8.29%

- mm

- mm

- 12-HIBs illumination system

## Mode(2,0)

- Mode(1,0)

- Mode(1,1)

- Mode(2,1)

- Mode(2,2)

## Summary

- The Rayleigh-Taylor Instability growth can be reduced by the oscillating gravity (acceleration), that may be realized by wobbling HIBs.
- The reduction ratio of the RTI growth depends on the frequency of the gravity oscillation.
- Even in the case of the multi mode gravity perturbation, the RTI growth is reduced by the wobbler.

## Wobblers may bring 

- a robust uniform target implosion.

## i-HIF Reactor

- / Particle Accelerator (Scale, Cost, Energy, etc..)
- / Physics of Intense Beam (Focusing & Compression, Emittance growth, etc..)
- / Beam Final Transport (Stable transportation, Interaction with gas, etc..)
- / Target-Plasma Hydrodynamics, stability, beam illumination scheme, robustness,
-    ignition, burning, ...
- / Reactor design, wall, T breeding, molten salt, material, neutronics, ...
- etc..

**Proposal of **
**a Conceptual Design of International HIF Reactor?!?**
**International Collaborative Work!**
**i-HIF Reactor**

**Accelerator**

**Ion Beam**

**chamber**

**target**

## Previous work on uniform HIB illumination

** ****IFE reactor**

** ****HIB illumination non-uniformity **
**< a few % **

- Pellet injector

- Fusion reactor

- Reactor chamber center

- Displacement  dz

***3.00×10******4***

***8.14×10******4***

***1.33×10******5***

***1.84×10******5***

***2.36×10******5***

**(a)**** ****dz = 0[********m]**

**(b)**** ****dz = 100[********m]**

**[J/mm****3****]**

- Fuel Pellet

- Conventional illumination pattern  => ~ **50-100********m **=> non-uniformity > **3.0%**
- Our results =>  ~ **300-400********m is allowable**

## Sample (beam profile) Simulation [constant]

- gravity

- parameter

**beam profile**** ****P****n**

## Sample (beam profile) Comparison (t=0.2 [μsec])

- density

- vorticity

- oscillation
- (γ[Hz])

- constant

- Sample (beam profile) Comparison (t=0.2 [μsec])