17 th HAPL Meeting Washington, DC October 30, 2007 Naval Research Laboratory

17th HAPL MeetingWashington, DCOctober 30, 2007

Naval Research LaboratoryPlasma Physics Division

Washington, DC

Work supported by DOE/NNSA/DP

Optical System and staging of the Electra KrF laser facility

NRL M. Wolford

M. MyersJ. SethianJ. Giuliani

Commonwealth Tech

F. Hegeler

RSIP. Burns

SAIC R. Jaynes

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

OutputInput

BG 28

LA Vision

Improved Near Field Measurements since last HAPL Meeting

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

Single Beam Electra Pre-Amplifier 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

Single Beam Timing Between Laser Input, Laser Output and Electron Beam (10 J)

-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

Single Beam Output Time Dependent Intensity

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

Single Beam Pre-Amplifier Yield Function of Input Timing

LPX

PLCC

Cylindrical Optics6 m Nike Lens

BeamsplitterCalorimeter

Photodiode Combo

770 mJ Laser Input Laser Beam separation ~26 ns

00.10.20.30.40.50.60.70.80.9

1

-5.0E-08 0.0E+00 5.0E-08 1.0E-07 1.5E-07Time (s)

Vo

lts

Beam 1 ~ 373 mJBeam 2 ~ 397 mJ

PD 2PD1

Two Beam Angularly Multiplex Preamplifier

Calorimeter Data

-1

0

1

2

3

4

5

6

7

0 25 50 75 100

Time (ns)

Inte

ns

ity

25 J Laser Output

300 mJ Laser Input Laser Beam separation ~26 ns

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0 20 40 60 80 100Time (ns)

Vo

lts

Beam 1 Beam 2

8.1 cm 7.6 cm

9.0 cm 9.7 cm

25 J Output of Two Beam Angularly Multiplex Preamplifier

Dimensions

LPX

Pre-AMPMain AMP

Electra Laser System

Calorimeter

Photodiode (PDM)

Photodiode (PDTarget)

42 m

-0.5

0

0.5

1

1.5

2

2.5

3

600 650 700 750 800 850

Time (ns)

Inte

nsi

ty (

arb

.)

PDM (452 J)

Pdtarget (452 J)

PDM1 2

3 4

5 6

Pdtarget

0

100

200

300

400

500

-1 0 1 2 3 4 5 6

Time (s)E

ner

gy

(J)

Big Calorimeter33 x 33 cm2 Calorimeter

Nike Calorimeters18 x 18 cm2 Calorimeters

Sum

Full Laser System 452 J Single Shot Yield

Full Laser System Laser Yield Depends on Timing Between LPX, Pre Amplifier and Main Amplifier

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 50 100 150 200 250Time (ns)

Inte

nsi

ty (

arb

.)

452 J (PDM)237 J (PDM)

The Difference if one or both beams are amplified in Pre-amplifier

Timing Discrepancy Between Amplifiers

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

-50 0 50 100 150 200Time (ns)

Inte

ns

ity

(a

rb.)

Shot 1 (PDM)Shot 2 (PDM)Shot 3 (PDM)Shot 4 (PDM)Shot 5 (PDM)

0

0.2

0.4

0.6

0.8

1

1.2

0 50 100 150 200 250 300

Time (ns)

Inte

nsi

ty (

arb

.)

Shot 1 (406 J)

Shot 2 (365 J)

Shot 3 (412 J)

Shot 4 (268 J)

Shot 5 (134 J)

PDM1 2

3 4

5 6

PDTarget

Full Laser System Yield 1.585 kJ in One Second 5 Hz Burst

Single Pass Double Pass

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

-50 0 50 100 150 200Time (ns)

Inte

ns

ity

(a

rb.)

Shot 1 (PDM)Shot 2 (PDM)Shot 3 (PDM)Shot 4 (PDM)Shot 5 (PDM)

0

0.2

0.4

0.6

0.8

1

1.2

0 50 100 150 200 250 300

Time (ns)

Inte

nsi

ty (

arb

.)

Shot 1 (406 J)

Shot 2 (365 J)

Shot 3 (412 J)

Shot 4 (268 J)

Shot 5 (134 J)

Single Pass Double Pass

Why laser Yield is Decreasing with Shot #?

Observation: Larger Percentage Laser Intensity Decrease was observed after one pass than double pass

Probable Cause: A declining input laser intensity into the main amplifier

Single Shot 5 shot Rep-Rate Burst

Cross Hairs for Scale

Near Field (7m) Beam ProfileSuggests increase in Phase Aberration is the cause for the drop in laser energy for

the Electra Laser System

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

-20 0 20 40 60 80 100

time (ns)

ampl

itude

(ar

b. u

nits

)

1st shot

5th shot

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 50 100 150 200 250

time (ns)

ph

oto

dio

de

amp

litu

de

(V) shot 1

shot 100

shot 200

shot 300

shot 400

shot 500

500 shots @ 5 Hz

5 shots @ 5 Hz

Pre-amp without gas recirculator

Main-amp with gas

recirculator

Pre-amplifier Needs Recirculator For Rep-Rate Operation

0

500

1000

1500

2000

2500

3000

-2 0 2 4 6 8 10 12Time (seconds)

To

tal L

aser

Yie

ld (

J)Electra Laser System 2.5 kJ 2 second burst @ 5 Hz

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 50 100 150 200 250

Time (ns)

Inte

ns

ity

(a

rb.)

PDM_1PDM_2PDM_3PDM_4PDM_5PDM_6PDM_7PDM_8PDM_9PDM_10

All Components 5 Hz operational for longer bursts

Again, Low Yield for later shots due to Pre-AmpPhase Aberrations, will be corrected with Recirculator

Calorimeter Response

1)Pre-Amp Recirculator (Design Complete) (For Beam Quality, Consistent Rep-Rate Output)

2)Improved Coupling from Pre-Amp to Main Amp

3)Improved timing control, Reduced Jitter (improvement already made)

4)Increase and Improve Diagnostics for KrF Code Comparison

5)Strip Cathode for Pre-Amp (Increased Energy Deposition in laser gas by ~25%)

On Going Improvements in Laser System Since Measurements were made