Matthew F. WolfordSAIC/Naval Research Laboratory

December 5, 2002

Electra title page

ElectraElectraNRL

J. Sethian M. Friedman

M. MyersJ. GiulianiP. Kepple

JAYCOR S. Swanekamp

Commonwealth TechF. Hegeler

SAIC M. Wolford

RSIS. Searles

MRC/AlbuquerqueD. RoseD. Welch

Work sponsored by DOE//NNSA/DP

The Electra Laser Facility500 keV, 100 kA, 100 nsec @ 5 Hz (x 2 sides = 50 kW)

The Electra Laser Facility500 keV, 100 kA, 100 nsec @ 5 Hz (x 2 sides = 50 kW)

Electra Configuration in Oscillator Mode

Laser GasRecirculator

(under installation)

Flat Mirror

OutputCoupler

Laser Cell(Kr + F2 +Ar )

PulsedPowerSystem

ElectronBeam Foil

Support(Hibachi) Window

Cathode

Bz

Laser GasRecirculator

(under installation)

Flat Mirror

OutputCoupler

ENERGY + (Kr + F 2) (KrF) * + F (Kr + F 2) + h (248 nm)ENERGY + (Kr + F 2 ) (KrF) * + F (Kr + F2 ) + h (248 nm)

Laser Cell(Kr + F2 +Ar )

PulsedPowerSystem

ElectronBeam Foil

Support(Hibachi) Window

Cathode

Bz

Two innovations allowed high hibachi transmission:

Laser GasKr + F2+ Ar

Vacuum

e-beam

1. Eliminate anode foil2. Pattern the beam to “miss” the ribs

Emitter

PressureFoil

(.002”Ti)

1. Non-uniform electric field at anode causes beam spreading2. Beam rotates and skews between cathode and anode due to Bz

ISSUES

Rib

AnodeFoil

(.001” Ti)

We can counter-rotate the emitter strips so beam goes straight through the hibachi ribs

Cathode stripsrotated 6 degrees

Radiachromic Film: Time integrated current profile at the pressure foil

Position of the hibachi ribs

30 cm

100 cm

3-D LSP Simulations (MRC/Albuquerque) Prescribe the cathode rotation Predict observed electron beam deposition into the gas

Efficiency Energy deposited in laser gas/energy in diode (for flat top portion of beam)

0%

10%

20%

30%

40%

50%

60%

70%

80%

laser gas pressure foil hibachi ribs

energydepositionfraction2 mil foil

Simulations by D. Rose & D. Welch, MRC Albuquerque

Tiger 1-D modeling shows 81% @ 750 keV (full scale system, or Nike)

Deposition Efficiency (500 keV):Deposition Efficiency (500 keV):Pressure foil 2 mil 1 mil

Experiments: 67% 75%Simulations: 66% 76%

400 J Measured with 33 cm x 33 cm Calorimeter

-50

0

50

100

150

200

250

300

350

400

450

-1 0 1 2 3 4 5Time (s)

En

erg

y (

J)

39.7% Kr, 0.3% F2, 60% Ar @ total pressure of 1.5 atm

KrF Laser Gas MixKrFHR 8% OC Cal.

400 J Photodiode Results

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

-100 -50 0 50 100 150 200 250 300

Time (ns)

Nor

mal

ized

Am

plit

ud

e

OscillatorASE

KrFLaser Gas MixKrFHR 8% OC Cal.

Experiment Versus Orestes Contour Plot

2.0 atm1.6 atm

1.2 atm

0.8 atm

pKr (Torr)

p

(To

rr)

Ar

850

700 600

stopping locus for 500 kV e-beam and 2 mil Ti foil

ELECTRARosc = 10%Pbeam = 800 kW/ccT(t=0) = 300 KF2 = 0.5%30x30x100 cc

100%Kr 195 J

60% Kr 280 J

40% Kr 360 J

800400

Orestes prediction by J. Giuliani et al.

Experiment

Rosc = 8%

Pbeam =650 kW/ccT(t=0) = 300 KF2 = 0.3%30x30x100 cc

80% Kr 205 J

40% Kr 400 J

Baratron Pressure Measurement

-0.02

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

-1 -0.5 0 0.5 1 1.5 2

Time (seconds)

Ch

ang

e in

Pre

ssu

re (

atm

osp

her

es) 360 J @ 1.85 atm

400J @ 1.5 atm

Composition:40% Ar 59.7% Kr 0.3% FluroineComposition:

Kr 39.7%, 0.3% F2 , 60% Ar

LouversOpen

Louversclosed

.

Ar*

Kr*

KrF*(Bv,Cv)

Kr+

ArF*

Kr2F*

Neutral Channel

Ar+

Ion Channel

harpoon

exch

ange

ion-ion rec

ArKrF*

absorption = F2 nF2+ F- nF- + KrF2nKrF2 + ArF2nArF2 ...

gain, go

, Ar,Kr,F2,F,e-

Kr,Ar,F2

KrF2 F-

Kr

F-Kr

2Kr2Ar

e-

Kr,Ar,F

24 species122 reactions

e-beame-beam

, F2,e-, Ar,Kr,F2,e-

F2

Multi-species plasma chemistry for KrF kinetics

Provided by J. Giuliani et al.

Fluorine Comparison, 100% Kr @ 1.2 atm

Orestes Prediction

0

50

100

150

200

250

300

350

400

0 0.2 0.4 0.6 0.8 1

Fluorine Abundance (%)

En

erg

y (J

)

Experimental Yield

Pulse Energies for 1 Hz Rep-Rate 99.4 % Kr + 0.6% Fluorine

-50

0

50

100

150

200

-1 0 1 2 3 4 5 6 7 8 9 10

Time (sec)

Ou

tpu

t E

ne

rgy

@ 2

48

nm

(J

)

Baratron Pressure Measurement for 1 Hz Rep-Rate 99.4 % Kr + 0.6% Fluorine

1.1

1.2

1.3

1.4

1.5

1.6

1.7

1.8

-1 0 1 2 3 4 5 6 7 8 9 10

Time (sec)

Pre

ssu

re (

atm

.)

290K

309K

339K350K

361K371K

379K 386K392K

325K

Ideal Gas ApproximationPV=nRT

Rep-Rate Measurement with 33 cm x 33 cm Calorimeter

-500

0

500

1000

1500

2000

2500

3000

3500

-1 0 1 2 3 4 5 6 7 8 9 10

Time (s)

En

erg

y (J

)

39.7% Kr, 0.3% F2, 60% Ar @ total pressure of 1.5 atm

To

tal E

ne r

gy

(J)

Electra Oscillator Energy Distance Dependence (33 cm X 33 cm Calorimeter)

0

20

40

60

80

100

120

140

160

0 5 10 15 20 25 30

Distance from Output Coupler (feet)

En

erg

y (

J)

With Output Coupler

Without Output Coupler(ASE)

Composition:99.4% Kr 0.6 % Fluorine at 1.2 atm

7

cu

rre

nt

de

ns

ity

A/c

m2

time (100 ns/div)

0

14

frequency (GHz)

am

pli

tud

e

0 1 2 3

0

.02

.04

-7

0

7

14

time (100 ns/div)

cu

rre

nt

de

ns

ity

A/c

m2

0 19

2 30

.02

.04

am

pli

tud

e

frequency (GHz)

e-

e-

The slotted cathode suppresses the transit-time instability on NIKE 60 cm Amplifier

Slotting cathode in other direction may completely eliminate instability

News FlashInstability has been eliminated on NIKE 60 cm amplifier with a

patch cathode

Electra Laser tasks 2003-2005 (page 1 of 2)

1. Evaluate recirculator for cooling and quieting

2. Evaluate hibachi gas flow cooling concept3. Front end: 80% complete for Dec 03 delivery (M. Myers Poster)

4. KrF Physics Experiments/modelinga. Oscillator, Small Seed input

b. Benchmark and Improve Orestes Code

5. Utilize Orestes for systems studies--establish tradeoffs

6. Build new “cathode tester”

7. Perform Electron Beam Physics Experimentsa. Instability, effect of Magnetic Materials, advanced cathodes

8. Demo solid state switch at full voltage and rep-ratea. Finalize packaging

FY 2003

Electra Laser tasks 2003-2005 (page 2 of 2)

1. Complete Electra as a laser1. Seed Oscillator + Front End + Angular Multiplexing

2. Start System Studies—link to Point Design

3. Design Pulsed Power Marx with advanced switch

4. Develop Long Life Cathode

FY 2005

1. Add ISI (beam smoothing)

2. Add Pulse Shaping

3. Evaluate overall system Durability and Efficiency

4. Build Advanced Pulsed Power for Front end

FY 2004