Post on 30-Jan-2016
description
HAPL 6/05
LASER GATED AND PUMPED THYRISTOR (LGPT) SCALE-UPFOR THE ELECTRA ADVANCED PULSED POWER
TECHNOLOGY DEMONSTRATOR*
*Work sponsored by the Naval Research Laboratory Plasma Physics Division
D. Weidenheimer, G. James, D. Morton, D. Knudsen, R. KnightTitan Pulse Sciences Division, San Leandro CA
D. Giorgi, T. NavapanichOptiSwitch Technology Corporation, San Diego CA
HAPL 6/05
• Flood entire switch channel with laser light…• Optical fluence determines di/dt• Advances in design, construction yield fast thyristor action (» 100 ns)• Near band edge light, high quality silicon enable 20 kV working devices• Continuous illumination reduces forward dissipation in thyristor• Uses relatively low power laser diodes in place of YAG
CONCEPT LGPT (Laser Gated & Pumped Thyristor),
Diode Lasers
On or off-board
Si Switch
p
n-
n+
n++
p++
LGPT Concept
HAPL 6/05
Limited Area Developmental Devices
Diode Lasers LGPT Laser Drive Boards
Development History I
HAPL 6/05
Development History II
16.4kV
162 to 184kA/(us*cm2 ) Active Si 0.7mCoul Charge Transfer
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
1.0E+00 1.0E+01 1.0E+02 1.0E+03 1.0E+04 1.0E+05 1.0E+06 1.0E+07 1.0E+08
Number of 5Hz Shots
kAm
ps/c
m^2
Act
ive
Si
0
0.5
1
1.5
2
2.5
kAm
ps/c
m^2
LG
PT A
rea
kAmps/cm2 (Total LGPT Area)
kAmps/cm2 (Active Si)
No. of shots to failure vs. current density at 162-184 kA/usec/cm2
HAPL 6/05
No. of shots to failure vs. di/dt density at 15 kA/cm2 current density
16.4 kV
15kA/cm2 Active Si0.7mCoul Charge Transfer
0.00
20.00
40.00
60.00
80.00
100.00
120.00
140.00
160.00
180.00
200.00
1.0E+04 1.0E+05 1.0E+06 1.0E+07 1.0E+08
Number of 5Hz Shots
kAm
ps/(u
s*cm
^2) A
ctiv
e S
i
0
2
4
6
8
10
12
14
Date
kAm
ps/(u
s*cm
^2) T
otal
LG
PT
Are
a
kA/us (Active Si)
kA/us (Total LGPT Area)
Development History III
HAPL 6/05
Laser Diode Bars
Development History IV
Circa 2000-2003 – first designs - standard cavity, 1085 thru 1125 nm progression in wavelength,60 x 1500 um x 90 um pitch, 2500 um bar length, stripline package
2004 - first LOC strain-mitigated designs - reduced facet loading, 1125 nm, increased emitter area/packing fraction, 150 x 2000 um x 180 um pitch, 2500 um bar length, increased lifetimes at requisite drive currents
2005 - first LOC designs with single-side confinement, 1125 nm, further reduced facet loading – longer life expectations, 140 x 2000 um x 170 um pitch, same bar length, due 6/05
first direct-coupled double-layer mini-bars, 2 emitter arrays ~150 um c-c, samepackage envelope, due 7/05
HAPL 6/05
Rev 2 Bord Current and Laser Power
0
100
200
300
400
500
600
1.50E-07 2.00E-07 2.50E-07 3.00E-07 3.50E-07 4.00E-07 4.50E-07
sec
Am
ps
0.00E+00
5.00E+01
1.00E+02
1.50E+02
2.00E+02
2.50E+02
3.00E+02
3.50E+02
Watt
s
CURRENT
6 Venkel 2.2uF 48V 0.050 series R180uJ
c
Development History V
Laser Diode Bars
Apparent turn-on delay (fill-time) of diode laser cavities – reproducible for fixed drive parameters
HAPL 6/05
Development History VI
CEO from 9-08-04 Experiment 12uF Driver
-71
-69
-67
-65
-63
-61
-59
-57
-55
-53
-51
1110 1115 1120 1125 1130 1135 1140 1145 1150
nm
dB
m
100A 61uJ
200A 125uJ
25A 12.2uJ
50A 30uJ
400A 225uJ
700A 265uJ
10A 2uJ from 9-10 data
Laser Diode Bars
Thermal CWL Shift and Spectral Broadening with Current
HAPL 6/05
Development History VII
Silicon Thyristors
• Basic design has remained unchanged since late 2002 – quasi-symmetric thyristor, 16.4 kV working • Continuous iterations/improvements made to passivation and encapsulation, optical interface, current contacts
• Co-planar anti-parallel diodes added 2004
HAPL 6/05
Diagnostics/Test Fixtures
Development History VIII
Circuit L
Circuit C
Circuit Load ( Twelve 55W Rs)
Floating Laser Power/Trigger
LGPT V Monitor
Three Tek HV probes for Charge, Load R,
and LGPT R
B-dot
• Improved diagnostics measure forward voltage drop with confidence – forward dissipation
• SF6 device immersion enables rapid turn-around between failures, maintenance and inspections
HAPL 6/05
Recent Conclusions
• Experimental measurements/data, Medici modeling, absorption profiles, ray-tracing, plasma-spread theory all point to active silicon volume being confined to that defined by the window/cell dimensions.
• Devices must be scaled by the cell unit – presently ~.0167 cm2
• Current density of ~15 kA/cm2 and di/dt density of ~90 kA/usec/cm2, corresponding to illumination levels of ~25 kW/cm2 (gross-active) are sustainable for ~107 shots at 5 pps by both silicon device and latest design lasers – 800 nsec half-sine pulseshape
• Reduction in current and di/dt density by a factor of 2, with commensurate reduction in optical illumination levels should be sufficient for ~109 shot service at 5 pps
• Scaled-up integrated device design must have flexibility to accommodate a range of 7-15 kA/cm2 active area and the requisite laser diode bars to provide illumination levels from ~12-25 kW/cm2 (active) in a device with an overall peak current rating of 10-20 kA, di/dt of 60-200 kA/usec
• Cell/laser bar counts for such a device will be from 40-80 at present cell dimensions – fewer if cell/laser bar size increases
• Scale-up requires direct-mount double bar laser packaging and series drive
HAPL 6/05
LGPT Scale-Up
Anode
Cathode
Anode Cathode
5x1 Test Bed
Cross Section Shows 4 of 40 Laser Channels
Adjustable Laser Holder
Low Inductance Strip Line connecting Drive Board to Laser
Top View Shows 20 of 40 Laser Laser Channels
Side View
• ~ 5 cm x 1 cm contact area device accommodates 42 cells in first iteration• Staggered patterning of cells for greater active area packing fraction• Expandable to 84 cells as necessary• Single laser diode bar each cell in first iteration – 5-10 kA peak current - 7/05• Direct-coupled double laser package upgrade - >10 kA peak - 8/05• Expansion to 84 cells – if necessary – 9/05
5 x 1 cm LGPT
LGPT Integrated with Electrodes/Lasers
HAPL 6/05
Scaled-Up Test Capability
• Integrated LGPT inserts into scaled- up test fixture
• Fast turn-around features
• Peak currents to >25 kA
• Full diagnostics as in small scale testbed
• Easy access to all internal components
• Components to undergo miniaturization phase after scaling demonstrated
HAPL 6/05
Near-Term: FE2 Retrofit
HAPL 6/05
KrF IFE Building Block
HAPL 6/05
Summary/Conclusions
• Understanding of LGPT performance/scaling is sufficient to move ahead with 5 x 1 cm KrF IFE building-block device
• Scaled-up device and test fixture designs completed ~April, 2005
• Silicon devices are in process at Optiswitch, due for first delivery by end of June, 2005
• Electrodes/laser drive hardware for 1st prototype due end of June
• First single bar packaged limited confinement LOC laser bars due end of June
• Direct double bar packaged lasers due in July, 2005
• Subsystem testing to begin early July
• Full integrated device testing in late July
• Engineering iterations/optimizations through 2005-2006
• Target retro-fit of FE2 in 2006-2007