Phto-injector laser chain NEWS Massimo Petrarca & Marta Divall
Jan 03, 2016
History:
1Amp2
Problems(for energy)
1Synch.
Problems(Laser -> Gun)
2Harmonic
ConversionEfficiency &Stability
Major issues inJanuary 2008
When NO Harmonic generation
was performed!
May June 2008 Harmonic generation
Performed with Amp1 only:New Problems discovered!
1Amp1
Problems(Over most of the other problems):
June July 2008Amp1 problems
(pulses train instability , ASE,
parasitic lasing)
2Amp2
Problems(for energy)
2Synch.
Problems(Laser -> Gun)
3Harmonic
ConversionEfficiency &Stability
3-pass Nd:YLF amplifier
2 pass Nd:YLF amplifier
Optical gate (Pockels cell)
PC
24
Drive Beam (PHIN); Probe beam~600ps=<Dt=<DtPC
1.5 GHzNd:YLF
Oscillator +Nd:YLF
Preamplifier1047nm
Micro pulses at 1.5 GHz
~666ps; 10W
400us amplification windowfor AMP1
Macro pulse
200us amplification windowfor AMP2
Macro pulse
UV
Dt Dt
Green
Dt
IR
Laser overview
Pulsepicker
First Amplifier layout
M1
M2
M3
M4
M5
1st pass2nd pass3rd pass
F1 = +1146mmPreamp. beam
58cm54cm
21cm3.5cm 2.5cm
5cm
M6 Nd:Ylf rod
-Final configuration: 3passages trough the rod with F1 to ~ compensate for the beam divergence: X(3rd pass)-X(1st pass)~1.2mm; Y(3rd pass)-Y(1st pass)~1mm . Nominal power ~3KW has been reachedSatisfactory trace pulse stability has been reachedTransverse beam parameters:M2
x~2.38; M2x~1.94
Power Measurements Amp1:
Unamplified ~ 5.6 W@ 50 amps ~ 6.7 W@ 60 amps ~ 7.4 W@ 70 amps ~ 8.1 W@ 80 amps ~ 8.8 W
@ 90 amps ~ 9.7 W ~3.0 KW
Amp2: layout
M12
M11
1st pass2nd pass
F2 = +300mm
M6
Nd:Ylf rod
Pericope+FaradyF3 = -114mm
Amp1 3rd pass.
M7M8
M9M10
94cm
57.5cm 20.5cm
122cm
2.5cm 2.5cm
29.5cm
29.5cm
22cm
75cm
156cm
Tot:48cm
PockelsCell
20cm
25cm26cm
7cm
F4 = +802mmF5 = +402mm14.5cm 7cm
-Present configuration: 2passages trough the rod with F3 and F2 for the matching: “beam size rod size”
Satisfactory trace pulse stability has been achievedPower ~6.3KW has been reached with 90A (Amp1@90A)
Way to Harmonic G. crystal
Amp1 + Amp2 @ 90A
-350 -300 -250 -200 -150 -100 -50 0 50 1000
1
2
3
4
5
6
Amplifiers @ 90A:Power [KW] vs Time [ms]
Amp1 + Am2 @ 90A
Power Measurements Amp1:
Unamplified ~ 5.6 W@ 50 amps ~ 6.7 W@ 60 amps ~ 7.4 W@ 70 amps ~ 8.1 W@ 80 amps ~ 8.8 W
@ 90 amps ~ 9.7 W ~3.0 KW
Power Measurements Amp1 @90A+Amp2 ..:
@ 50 amps ~ 10.0W@ 60 amps ~ 10.5 W@ 70 amps ~ 11.2 W @ 80 amps ~ 11.6 W
@ 90 amps ~ 12.3 W ~6.3 KW
Amp1+Amp2 Harmonic GenerationIR
energy within 2ms gate
GREEN energy within
2ms gate
UVEnergy within
2ms gate
Amp1 @90ampsPC on 2ms
( Best Result )
(4.15-1.33)mJ std=0.06mJ
~1.2 mJStd=0.016mJ
0.398 mJStd=0.012
133.3 nJ in a micro pulse
~44 % efficiency
~34 % efficiency
Amp1+Amp2 @90ampsPC on 2ms
(12.3-4.2)mJ std=0.26mJ
3.23 mJStd=0.07mJ
40% efficiency
0.692 mJStd=0.024
~234 nJ in a micro pulse
22% efficiency
A decrease on the conversion efficiency has been observed when both amplifiers are @90AOptimization of the beam size onto the conversion crystals has to be done; nevertheless the
conversion efficiency is still acceptable yielding a micropulse energy of ~230nJ (nominal 730nJ)Collaboration with Guy Cheymol “CEA”
On site synchronization meas.:
22 JNFJJ measreal
Jreal ~ 634 fs (rms jitter required <1ps)
JNF: jitter noise floor ~ 350 fs Jmeas: 724fs
Lecroy SDA (16GHz, 60GS/s+ NewFocus Photodetector25GHz)After on site investigation,
oscillator cavity perturbations due to thermal effects were
suspected
HighQ expert came and fixed the settings of the
oscillator end-cavity mirror(semiconductor saturable
absorber mirror “SESAM”):50C
Degree
Problem has been fixed
HighQ Jitter behavior (over a day)
Synchronization
0
20
40
60
80
100
120
140
160
180
200
0 3600 7200 10800 14400 18000 21600 25200 28800
Time [sec]
Jit
ter
[fs
]
HighQ company provided the unit to synchronize the laser to the ext. rf master clock (~1.499):“Synch”
From this unit it is possible to monitories the jitter “Laser vs Ext-rf”
Open Issues:Even more difficult (it takes time!!):
• The rod probably has to be changed to improve transverse beam profile (poor quality now!).• Third passage has to installed to extract more energy
and to compensate for thermal effect introduced by Amp1 .
• Lenses system for the matching “rod -beam” size along the 3 passages has to be installed …… …..(optimization of the whole beam line that comes after!!!!!)
• Coupling: “Pumping beam vs Nd:Ylf rod” has to be study (no cylindrical lenses installed now; it could be necessary to replaced those lenses to focus pumping beam into the rod.)• Conversion efficiency studies (saturation, best size onto crystals….)
The end