Electra title page

1
Electra title page
Electra
NRL J. Sethian M. Friedman M. Myers S.
Obenschain R. Lehmberg J. Giuliani JAYCOR
S. Swanekamp Commonwealth Tech F.
Hegeler SAIC M. Wolford Titan PSD, Inc D.
Weidenheimer
The Electra Laser Facility 500 keV, 100 kA, 100
nsec _at_ 5 Hz (x 2 sides 50 kW)
John Sethian Naval Research Laboratory April 4,
2002
Work sponsored by DOE//NNSA/DP
2
Topics This Time
Rear Mirror
Laser Gas Recirculator
Pulsed Power System
Bz
Cathode
Electron Beam
Foil Support(Hibachi)
Amplifier Window
Laser Cell (Kr F2)
Output Optics
3
Front runner for Advanced Pulsed Power should
meet IFE requirements (lt 10.00/J, gt80 eff)
Marx / Pulse Forming Network
DIODE
TTI
too new to evaluate cost and efficiency
Marx/PFN
Transformer PFL HV laser output switch
XFMR
S1
DIODE
PFL
8.35/J 87 eff
Laser-gated switch stack/array
Notes Cost / e-beam Joule, for 100 kJ
systems in quantities, NOT Electra
Efficiency Flat top e-beam/wall plug
4
Advanced Pulse Power Switch Development-1
CONCEPT
LGPT (Laser Gated and Pumped Thyristor)
Diode Laser
Flood entire switch volume junction with laser
light Gives high turn-on (dI/dt)
Si Switch
Photon ? ? 1105 nm 1.36 eV I.E. Just above
the band edge of the PN junction
RESULTS TO DATE
Prototype has demonstrated concept
Burst mode _at_ 5pps 104 shots Shots to
failure of chip under test 1.36 x 105 Max
voltage 3.2 kV (limited by external
insulation) Max current density 2.7 kA/cm2
(121 of IFE requirement) Max di/dt 1.36 x
1010 A/sec/cm2 (154 of IFE requirement,
limited by circuit) gt 10 x higher than non
laser triggered devices Max charge transfer per
pulse 1.7 mCb/cm2 (152 of IFE
requirement) Laser output 40 of maximum
(tested at gt107 shots) Successful demo of
thyristor/ laser diode integration
Lasers (hidden)
Switch
Feed Electrodes
5
Advanced Pulse Power Switch Development-2
Full required performance (16.7 kV)
NEXT GENERATION
Laser array in electrode (anode and/or cathode)
Generation 2 Forecasts Maximum voltage gt 16.7
kV (IFE requirements) Thicker device with
two sided laser pumping Design allows use
of advanced encapsulants (insulation)
(soldered or alloyed interface of silicon and
electrodes) Action (I2t) in excess of IFE
requirements Integration of larger area
reverse parallel co-planar diode to meet 100
of IFE reverse current requirement
Extrapolates to rail gap aspect ratio easily
(full IFE scale) EXPECT TO BE READY FOR TESTING
WITHIN 6 MONTHS
1 cm2 silicon thyristor and co-planar diode
(Single sided system shown)
6
Advanced Pulse Power Switch Development-3
Rail Gap Geometry
FINAL CONFIGURATION
7
Test bed is evaluating lifetime of capacitor
dielectric systems
Rep-rate 55 Hz
Capacitor/Switch
Test Bed Results 2 x 108 shots on CSI
capacitors (0.03 J/cm3) no failures 1 x 108
shots on GA capacitors ( 0.015 J/cm3) no
failures 2 x 108 shots on ABB thyristor in
service comparable to 3 stage MPC for IFE
8
Liquid Breakdown Dielectric Test facility nearing
completion
9
Cathode development Edge effect
10
Floating Edge Removers eliminate edge, fit
strip geometry, and dont emit (over 3000 shots)
See Frank Hegeler Poster
11
Expts theory show beam subject to transit
time instability. 2D PIC simulations predict
resistive slots stabilize beam
12
The slotted cathode suppresses the transit-time
instability on NIKE 60 cm Amplifier
e-
Slotting cathode in other direction may
completely eliminate instability
13
Reducing instability increases hibachi
transmission efficiency
See Matt Myers Poster
14
The recirculating laser gas can be used to cool
the Hibachi
Louvers Open
Louvers closed
gas flow
gas flow
FOR REFERENCE ONLY, DOES NOT VIOLATE NO OLD
VIEWGRAPH RULE
Foils
Rib
Contours of Stream Function-- flow is quiescent
for next shot
Foil Temperature below required 650?F
0
Cell Entrance
louvers
10
gas flow
cm along foil
20
After 1st shot After 1st cycle After 2nd shot
Cell Exit
200?F
400?F
600?F
Concept Modeling A.Banka J.Mansfield,
Airflow Sciences, Inc
15
Recirculator to both cool and quiet laser gas
plus provide hibachi cooling has been designed
Louvers
Static Pressure Contours varies by 14 Pa (10-4)
over laser cell
16
Other accomplishments
Front end for Electra Prescription from Orestes
KrF kinetics code 30 cm x 10 cm aperture, 100
cm long 1.0 J input. 30-45 J output (enough
to give 700 J output on main amp) e-beam
pumped May be first demonstration of advanced
switch technology
Big issue We still dont have a cathode with
the require durability