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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
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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
IFT\P2006-067
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).