Post on 13-Dec-2015
transcript
16th HAPL MeetingPrinceton, New Jersey
December 12, 2006
Naval Research LaboratoryPlasma Physics Division
Washington, DC
Presented by M. Wolford
Work supported by DOE/NNSA/DP
Electra (KrF) Laser Development
NRLJ. SethianM. MyersJ. GiulianiM. Wolford S. Obenschain
Commonwealth Tech
F. HegelerM. Friedman
T. Albert J. Parrish K. Gunlicks
RSIP. Burns
R. Lehmberg S. Searles
SAIC R. Jaynes
• Starting Integration of Electra Laser System– First Stages of Construction
• Pre-Amplifier Laser Energy Measurements– Increased laser yield to 25 J– Time-Dependent characterization of laser pulse– Near-Field Profile
• Cathode & Rep-Rate Durability– Anode Mesh (1st Implementation 12,363 shots)
Summary Since August HAPL Meeting
PinholeAmplifier
Focus
A. V. Deniz, S. P. Obenschain Opt. Comm. 106 (1994) 113-122
LPX
f f
LPX Diffuser
T. Lehecka et al., Opt. Comm. 117 (1995) 485-491
External Cavity Diffuser w/ additional amplifier
Electra ISI Laser Source Options
See NRL Poster:Large Aperture KrF Discharge Amplifier
Initial experiments and will continue with LPX as is, non ISI
PinholeAmplifier
Focus
AMP
Closely PackedConvex Mirror Array
Large Concave Mirror
Double Pass Large Amp Architecture
Electra Pre-Amplifier Laser Experiments
LPX 305 i
Input 0.5 J10 cm x 10 cm
Cylindrical lens Pair
Telescope
1 cm x 3 cm
3 cm x 3 cm
Calorimeter
OutputInput
Review: First light on Electra Pre-Amp
80% Ar, 0.3% Fluorine
0.0
5.0
10.0
15.0
20.0
25.0
30.0
8 12 16 20Pressure (psi)
Las
er O
utp
ut
(J)
Orestes 0.5 J Input
Measured Input ~0.5 J
25 J Electra Pre-Amplifier Output
80% Ar, 0.3% F2
0.0
5.0
10.0
15.0
20.0
25.0
30.0
8 12 16 20Pressure (psi)
Las
er O
utp
ut
(J)
Orestes 0.5 J Input
Measured Input ~0.5 J
Orestes 0.7 J Input
Measured Input 0.6 J
Timing Electron Beam to Laser, 10 J Yield
Voltage
OutputInput
64.8 ns
-50
0
50
100
150
200
250
300
350
-40 -20 0 20 40 60 80 100 120 140
Time (ns)
Vo
ltag
e (k
eV)
Po
wer
(10
0 M
W)
-0.5
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
Inte
nsi
ty (
arb
.)
Diode VoltageDiode PowerOutputInput
Output Time Dependent Intensity
-1
0
1
2
3
4
5
6
0 20 40 60 80 100 120 140
Time (ns)
Inte
ns
ity (
arb
.)
1 (-36.3 ns) 3.8 J
2 (1.3 ns) 10.0 J
3 (21.5 ns) 15.7 J
4 (40.7 ns) 20.0 J
5 (64.8 ns) 10.0 J
6 (88.0 ns) 2.9 J
Power (10 GW)
1
2
3
4
5
6
-40 -20 0 20 40 60 80 100 120 140
1 2 3 4 56
Input
Output
Pre-Amplifier Energy Function of Input Timing
0
5
10
15
20
25
-50 0 50 100 150Input Time (ns)
En
erg
y (J
)
80% Ar, 0.3% F2@ 16 psi80%Ar, 0.3% F2@ 18 psiOrestes 16 psi
Orestes 18 psi
-30 -10 10 30 50 70 90Time (ns)
Cause of Discrepancy
Progress in realizing long duration laser runs
ceramic honeycomb
primaryemitter • Gas buildup in the diode
• Degradation of the emitter
• Foil failure due to debris and/or plasma arcs in A-K gap
Previous Limits to Laser Durability(< 10 k shots)
March 2006 HAPL meeting
Hibachi
Solved with new all-carbon emitter.As much as 25 k shots
(reported at Aug 2006 meeting)Foil
MAY have been solved withhigh transparency anode screen
Screen
One Possible mechanism limiting foil durabilityElectron emission from Anode
Hypothesis Rationale
Micro particles can stick to the foil Emission is an explosive process.See marks on foil
Voltage reverses in diode Seen on Voltage monitorsafter the main pulse
Voltage reversal causes micro See what may be "cathode spots" onparticles to emit electrons pressure foil
Emission can be an explosive process Known fact.
Can puncture hole in highly stressed Experiments with an anode foil showpressure foil evolution of this process
First experiments with mesh, (90%-95% effective transmission) showa) Minimal degradation in laser energy (i.e. transmission OK)b) First Implementation lasted several multi-thousand shot runs
• Starting Integration of Electra Laser System– First Stages of Construction
• Pre-Amplifier Laser Energy Measurements– Increased laser yield to 25 J– Time-Dependent characterization of laser pulse– Near-Field Profile
• Cathode & Rep-rate Durability– Anode Mesh (1st Implementation 12,363 shots)
Summary Since August HAPL Meeting