Target Injection Update

Presented by Ron Petzoldt

Neil Alexander, Landon Carlson, Lane Carlson, Dan Frey, Dan Goodin, Phan Huynh, Robert Kratz, Robert Stemke

and Emanuil Valmianski

San Diego HAPL meetingAugust 8-9, 2006

IFT\P2006-067

Overview of injection progress

In-flight target steering has been achievedCan improve overall target injection accuracy (goal ±1 mm to ease beam steering)

1.5 m target fall

Magnetic coils

accelerate target upward

Magnetic slingshot design calculations were done and support the concept’s feasibility

€

F = −∇ m⋅B( )

5

9

0Field contour

IFT\P2006-067

In-flight target steering achieved with dropped targets

±3 kV steeringelectrode

Mirror

Target release

Target charging

Camera

Laser

10 cm, 0.14 s

80 cm, 0.18 s

60 cm, 0.24 s

Key parametersTarget charge (~-0.1 nC), Target mass (300 mg), 4 mm diameterPeak velocity (5 m/s), Steering field range (±150 kV/m)Steering range (±2 mm)

IFT\P2006-067

We integrated in-flight steering with tracking system for real-time trajectory correction

Labview screen shot - details next slide…

IFT\P2006-067

We integrated in-flight steering with tracking system for real-time trajectory correction

Poisson spot

X vs time (mm)

Control signal Vi

Steering voltage based on X position (Poisson spot’s centroid) and velocity updates each ~10 ms

€

e.g.

Vi = −3000 X i + 30 X i − X i−1[ ]( )

Y

X

Steering voltage

Steering duration

X&Y positiontrace

-0.4 -

0.0 -

0.2 -

0.4 -

-0.2-

IFT\P2006-067

X position with various steering voltages

-1000

-800

-600

-400

-200

0

200

400

600

800

1000

0 10 20 30 40 50 60 70 80

Drop number

Final X position (µm)

Standard deviation of target placement accuracy (1D) decreased from 254 to 107 µm

Much of remaining error is believed due to “curve ball” effect

in air

-1500 V

0 VActive

Feedback

v

F

~0.1 mrad accuracy is similar to that needed for IFE

Additional goal is ±20 µm at 0.5 m for FTF

IFT\P2006-067

GA’s EMS Group calculations support Robson’s magnetic slingshot concept feasibility

Conductingtube

Shuttle

S/C Coil

Trigger coil

Conducting tube provides centering force but induces

drag on shuttle

Magnetic slingshot concept advantages• Non-contacting ferromagnetic shuttle

• No friction wear• Centering force provided by conducting enclosure• No sabot or gas turbulence• Potentially very accurate• No mechanical feedthroughs required into cryostat• Powered via simple DC magnetic field

IFT\P2006-067

Vector Fields* calculations show centering force in conducting tube leads to ~1 oscillation period

Shuttle length = 40 mmShuttle radius = 4 mmCarrier saturation = 2.4 TTube inner radius = 8 mm

Tune for integer number of half oscillation periods during acceleration 12 ms for minimum radial velocity

r0

r0

Case (a)

Case (b)

-14

-12

-10

-8

-6

-4

-2

0

0 1 2 3

Radial Position (mm)

Restoring Force (N)

1 mm skin depth Superconductor

Bertie’s analytical estimate = 8.6 ms for same assumptions

*

4000 N/m => T = 12.5 ms

This shows centering force is adequate

IFT\P2006-067

r Hm-

m+a

a

Coil drag and power dissipated are significant but acceptable with sufficient tube conductivity

• Energy dissipated per target ~15 mJ in high conductivity case (0.075 W)• Acceleration force = 81 N >> drag force• 2.51011(Ωm)-1 corresponds to very high-purity cryogenic aluminum

0.01

0.1

1

10

0 50 100

Velocity (m/s)

Drag Force (N)

250 GS/m 2.86 GS/m2.86109(Ωm)-1

2.51011(Ωm)-1

1

10

100

0 50 100

Velocity (m/s)

Power Dissipated (W)

250 GS/m 2.86 GS/m2.86109(Ωm)-1

2.51011(Ωm)-1

Eddy currents in tube wallinduce drag = P/v

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A 40 coil design results in a very smooth acceleration profile

0 0.05 0.1 0.15 0.2 0.25 0.3 0.3510

15

20

25

30

35

z [m]

dB/dz [T/m]

0 150 300 Z (mm)

10

20

30

dB/dz

(T/m)

0

1

2

3

4

5

6

7

8

9

10

-100 0 100 200 300 400 500

z [mm]

Field Bz along z-axis, r=0mm

250A 40

250A 20

200A 40

200A 20

0 200 400Z (mm)

0

5

10

Magnetic Field Bz

(T)

Acceleration

(G’s)

200

400

600

SC = Nb3Sn vf = 60 m/s

IFT\P2006-067

Summary of injection progressIn-flight target steering has been achieved•Real-time trajectory corrections based on position measurement

(v~5 m/s)

•1-D placement accuracy improved to 107 m (1 at 0.8 m standoff).

Calculations support the magnetic slingshot concept• Can achieve constant acceleration with a 40 coil design. • Adequate centering force is provided by a conducting tube.• Drag is acceptable with a sufficiently high-conductivity tube material (very high-purity aluminum).