Computational modeling of magnetic intervention
Download
1 / 26

Computational Modeling of Magnetic Intervention - PowerPoint PPT Presentation


  • 221 Views
  • Updated On :

Computational Modeling of Magnetic Intervention. D. V. Rose* Voss Scientific, LLC A. E. Robson, J. D. Sethian, and J. L. Giuliani Naval Research Laboratory High Average Power Laser Program Workshop Naval Research Laboratory, Building 226 Auditorium October 30 and 31, 2007.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Computational Modeling of Magnetic Intervention' - LeeJohn


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Computational modeling of magnetic intervention l.jpg

Computational Modeling of Magnetic Intervention

D. V. Rose*Voss Scientific, LLC

A. E. Robson, J. D. Sethian, and J. L. Giuliani

Naval Research Laboratory

High Average Power Laser Program Workshop

Naval Research Laboratory, Building 226 Auditorium

October 30 and 31, 2007

*With a special acknowledgement to Chris Mostrom for continuing work on 3D graphics!


Status report on computational modeling for magnetic intervention mi l.jpg
Status report on computational modeling for Magnetic Intervention (MI):

  • Electromagnetic analysis of the Pechacek experiment is essentially complete.

    • We are continuing to use this analysis to explore other computational models suitable for efficient EM analysis of IFE-scale MI physics.

  • Ion orbit analysis of the conventional MI concept has indicated that the escaping ion “beams” in both the ring and point cusps result in very high current densities.

    • No integrated, feasible solution of this ion-stopping/materials problem is known at this time.

  • Ion orbit analysis of the OCTACUSP MI concept (A. Robson) is underway (and is the main subject of this presentation):

    • Discussed in the previous presentation by A. Robson.


Emhd simulation of pechacek experiment complete l.jpg
EMHD Simulation of “Pechacek” Experiment Complete: Intervention (MI):

  • The essential physical character of the experiment reproduced in a 2D, large-scale simulation.

  • This model is NOT directly extendable to IFE chamber-scale problems.


Slide4 l.jpg
To “zeroth-order”, orbit calculations can be used to conduct relevant design studies for ions leaving the chamber:

  • We are continuing to develop new models that should lessen the discrepancies and handle the IFE chamber spatial & temporal scales.

  • The Pechacek experiment will continue to be the test case for all new algorithms.

t (ms)

t (ms)


Emhd vs orbit calculation ring cusp width and transverse velocities compared l.jpg
EMHD vs Orbit Calculation: Ring cusp width and transverse velocities compared:

Ion channel “width” as a function of time at r=29 cm in the escape cusp.

Ion channel transverse momentum (vz) at r=29 cm.


Orbit analysis of the duckbill dumps shows a narrow and sharply peaked ion deposition pattern l.jpg
Orbit Analysis of the “duckbill” dumps shows a narrow and sharply peaked ion deposition pattern:

  • The duckbill ion dump design does NOT look feasible for the ring cusp.

  • “5th” coil designs to spread the escaping ion ring have not been successful.

HeliumDensity at25 ms


5 coil design used to explore the energy separation of the ring cusp ions l.jpg
5-coil design used to explore the energy separation of the ring-cusp ions:

The resulting time-integratedenergy deposition is a littlebroader than the 4-coil case.


Octacusp primary coil configurations include l.jpg
OCTACUSP Primary Coil Configurations Include: ring-cusp ions:

Triangles:

Circles:

Conformal Triangles:


Slide9 l.jpg

|B| contour levels at z=0 plane illustrating magnetic void at center of trap (left). 3D representation of a single |B| iso-surface also shown (right).

|B|~0.1T iso-surfaces

The long tube-like extensions away from the center of the chamber at X-type neutral lines.


Magnetic topology of a single tube or x type neutral line l.jpg
Magnetic topology of a single “tube” or at center of trap (left). 3D representation of a single |B| iso-surface also shown (right).X-type neutral line:

Magnetic field at x=200 cm plane:

Chamber wall, r=5 m


3d view illustrates that the magnetic field lines extend through the eight solenoids l.jpg
3D view illustrates that the magnetic field lines extend through the eight solenoids:

Sample streamlines withoutconductor boundaries:

Sample streamlines withconductor boundaries:


3d streamlines can aid in the analysis by looking for critical field line intercept points l.jpg
3D streamlines can aid in the analysis by looking for critical field line intercept points:

“outside” view

View from “inside” the chamber:


Sample ion orbit calculation l.jpg
Sample Ion Orbit Calculation: critical field line intercept points:

  • 5-meter radius vacuum chamber

  • Four triangular main “coils” mapped onto a 6-meter radius sphere

    • each triangle carrys 6 MA

    • Allows 1-meter for neutral shielding

  • Eight 1.1-meter radius solenoids along ion drift tubes

    • Drift tubes have an inner diameter of 0.9 meters

    • Solenoids composed of 11 individual rings, each carrying 100 kA

  • Only 3.0 MeV Helium ions (4He++) followed here.

Oct17.lsp


Individual particle and density plots are less helpful here l.jpg
Individual particle and density plots are less helpful here: critical field line intercept points:

Particle positions and

densities at 5 ms:


Slide15 l.jpg
Charge deposition on the chamber surfaces (time-integrated) is being used to optimize the magnetic field topology:

Here, only surface cells with non-zerocharge deposition are plotted.

All surface cells plotted


Slide16 l.jpg
Views of the charge deposition in a single octant illustrate the three-fold symmetry in the escaping ion distribution

For this case, about

40% of the ions reach theends of the drift tubes.

About 2% are deposited at the neutral line points,and 58% are in the flowerpetals radiating out from the entrance to the drift tubes.


Target planes along the drift tubes are used to diagnose the escaping ion beams time integrated l.jpg
Target planes along the drift tubes are used to diagnose the escaping ion beams ( time-integrated).

Lsp uses combinatorialgeometry of basic objectsto build physical spaces and material boundaries.

Target planes alongone drift tube are shown.


3d targets in drift tubes indicate a focused ion beam l.jpg
3D targets in drift tubes indicate a focused ion beam* escaping ion beams ( time-integrated).

At r = 10 m:

* Additional diagnostics, not shown here, also indicate an expanding ion beam envelope.


Issues work in progress l.jpg
Issues/Work-in-Progress: escaping ion beams ( time-integrated).

  • Tapered X-type neutral line physics (including diamagnetic effects) needs to be addressed.

  • Full “Perkins” ion spectrum needs to be examined once the current design exercise is completed.

  • Lead vapor dE/dx mass-stopping analysis for the ions (realistic energy loading, radiation, thermal cycles, etc.).

  • The eight-fold symmetry of the OCTACUSP design adds complexity to the plasma/magnetic-field interaction analysis. (A full 3D inertialess-electron dynamic EM model is still being explored.)


Summary l.jpg
Summary: escaping ion beams ( time-integrated).

  • Issues with the “conventional” MI chamber (with 2 or 4 coil system with ring and point cusps) are forcing consideration of other magnetic field topologies.

  • Bertie’s OCTACUSP design:

    • preserves the spherical symmetry inherent in direct-drive systems

    • minimizes the chamber surface area for ion escape ports (~5%)

  • Other coil configurations are possible (nested triangles, etc.)


Backup slides l.jpg
Backup slides: escaping ion beams ( time-integrated).


Oct16 lsp l.jpg
Oct16.lsp escaping ion beams ( time-integrated).

1-m radius solenoids at each point cusp, 2 kA/cm (11 rings each carrying x MA)

5-meter radius chamber

Conformal Triangles on 6-m radius sphere, 3 MA

3 MeV He++ ion orbits followed

Show magnetic field topology

Ion orbits

Sample density plot

Energy deposition on surfaces.


Cutaway view of an iso surface of b illustrates location of the neutral lines l.jpg
Cutaway view of an iso-surface of |B| illustrates location of the neutral lines:

|B|=0.6 T iso-surfaces.

Neutral lines (6)lie along thecoordinate axesin this orientation,and terminatenear the chamberwall.


Slide24 l.jpg
Plots of the ion charge deposition on conducting surfaces are used to guide the design of the magnetic fields.

Ion Energy Delivery:

~20% in 8 tube ends

~4% in 6 neutral line points

~76% in the chamber wall (flower petals)


3d targets in drift tubes indicate a focused ion beam25 l.jpg
3D targets in drift tubes indicate a focused ion beam* are used to guide the design of the magnetic fields.

R = 6 m

R = 10 m

* Additional diagnostics, not shown here, also indicate an oscillating ion beam envelope.


Particle escape orbits are complex in the octacusp magnetic field l.jpg
Particle escape orbits are complex in the OCTACUSP magnetic field:

Sample orbits for 3 MeVa particles launchedfrom the origin at differentinitial angles.

Escape radius is 200 cm(the radius of the conductingspherical boundary).


ad