Summary of activities done on PSL on the 2 and 3 oct
More analysis coming later

# we check the neoVAN alignement:
no major issue found

# we check the PMC throughput:
- we confirm PMC_Th = 91 % considering as the inciddent power the power PMC reflected when it is not locked
- we confirm PMC_Th = 88 % considering as the incident power the power incident on the PMC

the 3% difference are know since the begining of the PMC life at EGO. A 3% loss in the non resonant optics of the PMC related (hublot enclosure, rear face of the PMC mirror...) mimic this loss. We have no clue yet from where the power is lost. This loss would be outside the PMC rather than intra-cavity loss related.

We use to have 98-99% right after the PMC integration (Jan 2018) using the first calculation mode

# we have swapped the M8 mirror mount with a more stable one (the first Rmax after the neoVAN). Let's see wether it reduces the lg term horiz drift we use to have

# we gave back 56 mW for the squeezing (the dedicated beam was clipped after the swap of the M8 mirror mount, we restore the situation)

# we swap the picolas module. The hope is to remove the 1.151 kHz line with spoil the PSTAB actuation

plot shows the improvement in reducing the 1151Hz line on the neoVAN (PICOLAS module swap), this will help PSTAB in its daily life

# we install 2 Power monitors around the PMC:
in order to get signals more closely related to the optical power at the PMC entrance and gt a more reliable PMC_throughput monitor
- PSL_PMC_PMONIT_Pin: power pickoff through the M12 mirror, with the AOM contribution (1st order diffracted) blocked. It means this is the power at the PMC entrance.
- PSL_PMC_PMONIT_Prefl: identical to PMC_REFL_DC but with a large PD dedicatd for P monitor.

it seems some sudden slope change has occured in the ML with no visible reason.

# visible in plot2, on ML_PZT_CORR.

- It triggers some correction at the EOM_CORR. According to the actuation path cross (30 kHz) between the pzt and the EOM, EOM_CORR should be the ML_PZT_CORR signal filtered by a high pass filter. Nothing unsual there.

- the signal ML_FREQ_Q_MONIT features a small glitch contemporary of EOM_CORR and with a quite different sgnature than the one of ML_PZT_CORR: it means ML_PZT_CORR is there to compensate some freq. drift which has occured inside the ML, and is not driving the frequency of the PSL.

# plot1

- the trend of the ML_PZT_CORR does not fit with other signals and confirm that the issue comes from the inside of the ML

# Unlock at 6H49MN47SEC_UTC

I (Fred)  am responsible for  this unlock while we were in the atrium for locking the master laser frequency monitor (MLFM). Beside this light intervention I went at the rear of the master laser crate in order to plug a hole in the wooden box of the MLFM with some tape. IIt maybe that I have hit the fiber which bring the ML to the LB (stainless steel shield) although I pay attention to not hit it...

the plot show a raising oscillation on EOM_corr (4 kHz) which ends up in saturation and unlock

The signals ML_FREQ_I_MONIT / ML_FREQ_Q_MONIT refer to the ML frequency noise for frequency below 150 Hz and aboce 150 Hz, (see next entry for the releavant calibrations)

# AOM alignement

Upon arrival the AOM_stage is found at 12.0 mm (AOM translation stage readout)

Procedure: we reduce the slave power. We reduce the power at PMC using the polarizer downstream the neoVAN.
-> PMC_REFL_DC goes from 3,6 V => 17.8 mV (considering 6 mV of offset => 11.8 mV => reduction of 305, means 0.295 W in the AOM)

we set the AOM_stage at 17.2 mm -> PMC_REFL_DC reduced from 17.8 to 17.4 mV ( 2,25 % loss)
--> this means that the beam center is on the AOM edge for x_AOM_stage = 17.2 + 0.74 (*) = 17.94 mm

we set stage at 15.30 mm, where the straylight is faint (elsewhere the spot is quite bright)
The beam center is thus at 2,64 mm from the AOM edge ( it used to be at 5,92 mm before)

(*) From FSOPT-1708-01_AOM_followup.pptx: 2.2 % power loss are induced by a clip at a beam radius distance from the edge. The beam radius in the AOM is ~740 um

We gain 3,3 mm closer to the AOM edge, this allows to improve the phase of the PSTAB loop by 360*100e3*3.3e-3/5740 = 20,6 ° (wrt previous situation)

Rem.:
- after the centering and with the normal conditions back: we got PMC_REFL_DC = 3.71 V (not locked)
- the PMC get very misaligned both in vert & in horiz, supposedly due to the AOM centering which is un-expected
- after the PMC realign PMC_REFL_DC = 0.72 V (locked). we stop at ~ 21H10MN36S LT we got the best PMC align (PMC_TRA =  1.107 V, likely the AOM was not connected)
 

We investigate issues mentionned on the PSTAB.

A detailed analysis will come later.

# upon arrival we found the PSL_ELEC_1712_01 (black crate) which suffers from mis-tuning of a IMC_FSR notch and hence shows reduced UGF (30 kHz)

Since we were not able to easilly adjust the notch we swap the rampauto with the ELEC_1803_01 (the glitchy one frm ER13).

In ELEC_1803_01 we adjust the notch to 1.04432 MHz since it was found mistuned by around 5-10 kHz.

We check that the correction is clamped to ~ +/- 1.0 V as expected

--> the max UGF is 90 kHz above which a 1 MHz oscillation ruins the erro signal

# We adjust the beam alignment into the AOM:

we found the beam ~ 5 mm appart from the AOM edge: translation stage indicates x = 12.0 mm

we move the AOM to x = 15.4 mm. the beam center is thus at  ~ 2,5 mm from the AOM edge (the beam size there is 740 mu radius)

this should spare 20 degrees in the PSTAB OLTF.

we check the PSTAB OLTF with PSL_ELEC1803_01

we get UGF_max = 110 kHz before an oscillation appears at 200 kHz (no 1 MHz anymore)

we get UGF_mini = 24 kHz (due to the 1/f^4 corner)

we let the gain set to get UGF = 70 kHz

We conmsider this rampeauto as fully compliant.

Next step to is get the PSL_ELEC_1712_01 identical as ELEC_1803_01 (notch tuning)

After the PSL work of last night it took a few hours to recover the whole injection system mostly because there was a large offset on the PMC error signal.

We have not yet understoof the orgin of the problem but we could null this offset by shifting the 14MHz modulation frequency from 14.230MHz to 14.5MHz.

Maybe a cable length in the PMC loop has been changed?

When the PMC has been relocked we noticed a loss of roughly 5% with respect to yesterday. We have still to understand the origin of that loss. Part of that could

be related to the laser amplifier. Further investigations are needed.

In any case we could close all the injection system loops without any problem.

We may need to realign the PMC in the coming hours/days to recover misalignment related to thermal transients.

We have removed the temperature probe inside the PMC enclosure (since useless and source of 135 mW of heat) to get rid of a possible source of outgazing

We have placed a Rmax from LMA (4M002 formerlly devoted to the PMC) as an absorption witness

We did this by removing the flange on the top of the enclosure cover.

we put the whole back

We check that the PMC_PRESS_IN and OUT still indicates 99 kPa

we check that the piezo is still able to scan the PMC.

when leaving the PMC_REFL says TEM01 and TEM02 nearly 0 and TEM00_R at resonance =  (1.5V - ~ 0.2V ) / 6.4V = 20 % [ REFL_TEM00 -{TEM01+TEM02}]/REFL_OutOfReso

we have scanned the PMC at 4Hz around 1220661742 for few mn.

We leave with the PMC scanning and the beam blocked at the PSL bench

No fans are running on the power meter

The R_PMC power is dumped into the water cooled beam dumped

The neoVAN fibers are left coiled with the pattern described in a future logentry (the "coiler" is lying on the PSL bench)

# After our investigations on the output of the neoVAN fibers we give back the PSL. Since datadisplay shows a huge latency it is not possible to get any info from it for assesment of the powers at PSL level after our work. Anyway the powermeter indicates 86 W at the output of the neoVAN.
Data will come later regarding the neoVAN fiber output.

# Btw we 've noticed that the coils installed with Bastian Schultz on the pump fiber have been removed, likely during the neoVAN_60W_pump swap unless some misunderstanding.Those coils were supposed to improve the homogeneity at the fiber output.

# There is no over-pressure in the laser lab since our arrival, could be an issue wrt the dusts contamination on the bench

# Attempt to assess the PMC throughput

• Data from 13/06/2018, ~10 pm LT

PMC_Inc    PMC_R_OR    PMC_R_R        PMC_TRA T_PMC (all P in W)
87.0            84.0                 13.2                  68.9            0,977
87.0            84.6                 12.7                  69.9            0,976    (6)

Legend:
PMC_R_OR: reflection from PMC out of resonance
PMC_R_R: reflection from PMC at resonance
PMC_Inc: power incident on the PMC (read after LB_M12)
T_PMC = (T + PMC_R_R)/PMC_R_OR
(6) with diaph installed at 5 cm downstream of the AOM
 

• Conclusion:

--> 2,4 - 3 W (~ 3%) are lost between the PMC input and the PMC reflection (mentionned in 41916)

with T_PMC + 1,5% = 0,992  (1,5 % is the known Round trip loss from logentry 41091)  --> that means less than 1% unexpected loss in the PMC
 

we investigate the power "loss" between neoVAN and PMC reflection, ( data from 13/06/2018)

# Power meas. around PMC
a- PMC_REFL: 84.4 W (1)
b- P_LB_M12 = 87.7 (2)
c- P_LB_M12 = 89.9 (3)
d- P_LB_M12 = 87.2 (2)(4)
e- PMC_REFL: 84.8 W (1)(4)(5)
f- we put the prism which manages the AOM diffraction 1st order mode further apart from the AOM zero order diffraction to cope with possible clipping: we saw no effect since we got PMC_REF = 84.2 W (1)(5)

Legend:
(1) calo at 44cm from lens 70mm installed on PMC_REFL (large beam on the calo, w ~ 3 mm, 0.6 kW/cm2)
(2) calo at 35cm from an on purpose lens (75mm) located at 5 cm from M12  (large beam on the calo, w ~ 2,3 mm, 1kW/cm2)
(3)  no lens ("small" beam on the calo, w ~ 0,6 mm, 16 kW/cm2)
(4) with a diaph at 3 cm from M12 to remove ghost beams from Brewster polar
(5) with small PMC scan and seek for the max power (far from any modes)
PMC_REFL is the power reflected by the PMC when out of resonance with the use of a short focal lens to expand the beam on the calo surface
P_LB_M12 is the last mirror before the PMC

Conclusion:
--> b,c,d: the power measurement with small beam over-estimates by ~ 2,8 % !?
--> b,d: the ghosts beams generated at the polariser level do not account for noticeable power loss. We put a diaphragm merely to cope with possible accidental large misalignment at neoVAN which may affect the PMC.
--> f: the prism which manages the AOM 1st order beam is not an issue wrt the PMC power balance
--> d,e: 2,4 W are lost between the PMC entrance and the PMC reflection (while out-of-resonnance). Since the PMC reflection out of resonnance is expected to be 1-1,7e-4 assuming 380 ppm intracavity loss (needed to explain the 1,5% loss of intracavity loss, see 41091) we have no clue yet on where are lost those Watts

The plot displays PMC_R & T with 380 ppm RTL loss; R+T=1 for all the mirrors, a specific term along the propagation to cope with the loss

After the neoVAN tuning on 12-13th of June (41874) we relaign the beam onto the associated diagnoBox (indeed the optical axis set by the neoVAN amplifier were changed while adjusting the matching lens inside the neoVAN head (done by B. Shultz)).

Moving the QD_H and V signals from 0,7 V to 0 leads to a change of the PSL_AMP_DC signal by 2%. This signal monitors the overall power of the neoVAN. Those numbers give some insight on how the calibration is affected by some beam misalignment

Tests around the fibers bringing the pump to the neoVAN

# we check whether that the swap of spare fiber FOPT-1801-01 with FOPT-1703-02 is mandatory
- with the fiber PSL-FOPT-1703-02 on the neoVAN, we get PMC_TRA = 66.0-66.7 W
- we install the fiber PSL-FOPT-1801-01 instead of PSL-FOPT-1703-02, we get PMC_TRA = 65,5 W
we come back with fiber PSL-FOPT-1703-02 on the neoVAN, we get PMC_TRA = 66.0 W

--> it seems both fibers are equivalent as long as some bending is put on PSL-FOPT-1703-02

# Fiber bending (for stress) location

we check whether the bending set near th eamplifier head is still mandatory while another bending has been set on the diode side

with stress near the head released: the power drops and comes back to 66 W
-> seems the stress becomes useless as long as another stress has been set near the diode box

Rem. : removing the stress on the fibers at the diode side give a drop of 1 W at the PMC output

-> it seems cumulative bending of the fiber does not bring any significative improvement. One single beding (one fiber turn over a 10 cm diameter round) seems enough

!!! I ve checked that PD_PMC_REF is well centered !!!
AOM disconnected

d (m)    P_M9(W)    TEM02_V    TEM02_%    TEM00_OR(V)    C_R        TEM00_R    PMC_TRA(W)   Comment
0,64    89.0    0.020    0.5%    3.45        0.156    0.56    66.2    Step180613_1
0,62    90.3    < 0.02     0%        3.46        0.150    0.52    67.8    Step180613_2
0.60    89.2    <0.02    0%        3.42        0.155    0.53    65.9    Step180613_3
-> seems d=0,62 m is optimum

0.60    93.2    0.050    1.4%    3.54        0.169    0.65    68.3    Step180613_4
0.62    90.7    x        x        x            x        x        x        Step180613_5
0.62    95.1    0.180    5        3.58        0.179    0.820     63.5    Step180613_6
0.62    90.6    < 0.02    0        3.40        0.158    0.540    65.7    Step180613_7
0.62    89.1    x        x        x            x        x        66.3     Step180613_8
0.60    89.4    < 0.02    0        3.425        0.147    0.504    67.2    Step180613_10
-> seems d=0,60 m is better than 0,62 !... and we can't recover what we got in Step180613_2 (see Step180613_7)
--> we stick to d = 0,60 m

# Play with different pump
0.60    x        x        x        x            x        x        69.1    Step180613_11
0.60    x        x        x        x            x        x        68.5    Step180613_12
0.60    x        x        x        x            x        x        68.9    Step180613_13
0.60    x        x        x        x            x        x        69.1    Step180613_14
0.60    x        x        x        x            x        x        67.0    Step180613_15
0.60    x        x        x        x            x        x        69.4    Step180613_16
0.60    x        x        x        x            x        x        69.9    Step180613_16_bis
0.60    93.0    0.06     1.68%    3.56        0.620    0.157    70.2    Step180613_17
0.60    x        x        x        x            x        x        68.4    Step180613_18
0.60    x        x        x        x            x        x        69.9    Step180613_19
-> seems Step180613_17 is the best config

!! the meas. of the TEM02 mode is missing... should be done any time later
This may sligthly change the conclusion on the most efficient pumping configuration
indeed:

• we expect Step180613_12 to lead to 5% would lead to 72 W assuming TEM02 is cured (same config as Step180613_4)
• Step180613_17 should present even more TEM02 (TBC) since the pump config is unbalanced is worsen (4,5/5,5 A) could lead to 73,7 W assuming TEM02 is cured. Again: To Be Checked

Legend:
d: dist(LB_L5-neoVAN input side)
Step180613_1: 4.2/5.3
Step180613_2: 4.2/5.3    
Step180613_3: 4.2/5.3
Step180613_4: 4.7/5.3 Pgoes to 94.2 W after 30'
Step180613_5: 4.2/5.3 for a double check
Step180613_6: 4.7/5.3
Step180613_7: 4.2/5.3
Step180613_8: 4.2/5.3 before moving to 0,60 for double check that this is the optimum
Step180613_9: 4.2/5.3
Step180613_10: 4.2/5.3
Step180613_11: 4.5/5.3
Step180613_12: 4.7/5.3
Step180614_13: 4.6/5.3
Step180615_14: 4.4/5.3
Step180615_15: 4.5/5.1
Step180615_16: 4.5/5.4
Step180615_16_bis: 10' later after realign
Step180615_17: 4.5/5.5 (by the way, we got also 67.5 with AOM), 18:00 LT
Step180615_18: 4.6/5.6
Step180615_19: 4.4/5.4

--> we choose the config Step180615_17 from now

it leads to  70,2 W at PMC_TRA with the AOM disconnected

it leads to 67,5 W at PMC_TRA with the AOM back connected

We have swapped the mirror mount of LB_M6 and LB_M7 from newport ones (picture 1) to Polaris_Thorlabs ones (picture 2). The newport are suspected to be unstable since they show some "hysteresys" when moving the micrometer adjusters forward and backward.

We 've checked it did not impact on the overall power.

This should help in long term stability although it is unlikely that this will cure the neoVAN beam drift mentionned in 41742

# Monday 11/06/2018: seeder size status before neoVAN insestigation with neoLASE engineer

• we set the neoVAN seeder size to 131 um, located @ ~ 6 cm upstream the neoVAN input side

it should be compliant with the nominal setting from the datasheet: 130 um at  5 cm (see attached pdf doc) .

• Slave-to-neoVAN telescope tuning:

we set the distance between LB-L4 and LB_L5  to 33.1 mm (lens center -to-lens center)
dis(LB_M5'-LB_L4) = 380 mm, dist(WP5-M5') = 535 + 270 mm
the beam profile measurement of the seeder is stored into 180611_SlaveTelescope_BeamProfile_r.txt, (see also plot). The profile of the seeder is got in transmission of LB_M6 mirror
--> that is 131 um at 55 cm from LB_L5 (from propagation measurement) and 6 cm before the neoVAN input side ( we set dist(LB_L5,neoVAN) to 61 cm)
 

Summary of the tests made around the neoVAN amplifier with Bastian Schultz from neoLASE Cie

Tuesday 12/06/18

I - Illumination at fiber output (rem_1):
we check the illumination at the output of the fiber connecting the pump diode to the amplifier head. 4 fibers are currently installed: PSL-FOPT-1703-01/02/03/04
- the fiber PSL-FOPT-1703-02 output is very sensitive to any fiber bending (R< 5cm):
the mean power in the center of the aperture (within a radius = 0.25*illuminated_area_diameter) is fluctuating accordingly (see picture 1, non homogeneous enlightening)
- the fiber PSL-FOPT-1703-02 output is very sensitive to the injection setting too( we twist the fiber connector at the diode level):
again some illumination change in the center part and the appearance of an outer dark ring (close the edge of the illuminated area)
- The fiber PSL-FOPT-1703-01 shows also an illumination with a central area somewhat less bright than the edge but features a less sensitivity to any bending than with the previous fiber (PSL-FOPT-1703-02)
- we 've exchanged the fiber FOPT-1703-01 and FOPT-1703-02 at the diode level and found that the issue is related to the fiber FOPT-1703-02 rather than to the diode

The output power has been found compliant with what expected on June the 5th (see https://logbook.virgo-gw.eu/virgo/?r=41699 )

rem_1: we use a screen located at 10 cm from the fiber output

II - Effect on the 1064nm beam profile
- we have checked that twisting the fiber at the diode level has no/little effect on the neoVAN beam profile (checked with camera PSL_AMPL, Gx client)
- we check that bending all the 4 fibers with a radius of curvature ~ 5 cm reduces the pedestal of the beam profile by 10-15%. The bending is applied 2 m before the amplifier head. See 180612_neoVan_BP_47004700.png (with bending).
Bending specifically the fiber FOPT-1703-02 seems to have a larger effect than with any other fiber.

III - neoVAN best direction of use
B. Schultz moved the IPCML lens to check the hypothesis of a possible wrong direction of the neoVAN implementation (3 - 4 pm)
(IPCML: Inter Pair-Crystals Modules Lens = lens between the first 2 and 2 last crystal pairs of the amplifier head)
-> we end up with 1 or 2 more Watt for the beam but we have considered this as non-significant and maybe due to the usual power lg term drift.
We find no major improvement on the Beam Profile either
-> we put back the lens IPCML to the former configuration

IV - IPCML adjustment
B. Schultz 's adjusted the IPCML lens centering to improve the beam profile at the neoVAN output.

V - Centering of the pump on the crystals (7 - 9 pm)
B. Schultz has optimized the pump centering wrt the crystals. No clear obvious improvements
-> 180612_neoVAN_BP_47004700.png = neoVAN beam in the far field (ie @lens (500mm) focus) (figure 2)

Conclusion:
- it seems the fiber are one of the major DOF which can impact on the neoVAN beam profile
- This is also the only thing which have changed wrt the tests completed at AEI (which showed excellent performances: 90 % TEM00 modal content)
- the major change between the commissioning made in December ("nice" performances of the amplifier, see https://logbook.virgo-gw.eu/virgo/?r=40296) ) and today is the location of the pump diodes driver which used to be in the laser lab before the 18th of Januray and in the EERoom after. Accordingly the fibers were let coiled (1 m diameter roll) on the ground or ~ straight in the cable tray between EERoom and Laser lab.

A possible scenario could be to put back the diodes in the laser lab to try to get better perf. But I guess we don't like this scenario...


13/06/18

I - Since fibers were identified as possible culprit we tried to swap the present fibers with the one used with the V+ amplifier (50W) still in place.
Unfortunately the threads of the fiber connectors and the one of the socket (100W amplifier head) seems incompatible, no way to complete 1/4 turn, although they fulfill the same standard!!..
This might be important to remember if one want to get spare fibers.
The sockets are custom made for neoLASE, the issue is likely to come from this part.


II - bending the fiber
- we put some bending (5 cm radius) on the fiber at the diode level. We see little effect on the power nor on the beam profile.

- after  couple of hours we release the bending at the amplifier head level (installed the day before): we see little effect on the beam.

- While releasing the bending at the diode level we realized that this bending improve by 1 W the PMC output (likely to induce some beam change and/or power). One single loop enough since we notice no further improvement with more loops. So we put this bending back in place

III - spare fiber and fiber FOPT-1703-02
we swap the sensitive fiber FOPT-1703-02 with a spare fiber, we see no major change on the beam profile  nor on the power. We decided to put back installed the FOPT-1703-02 fiber in place and let the spare fiber aside, ready to be installed in case of failure (4 pm).


IV - Power at PMC transmission
Before leaving ( 10 pm UTC) we get the PMC_TRA = 69.7 W (without the AOM connected and 67 W with the AOM connected)
A dedicated log entry will come soon to given some more detail on the power balance.

Rem.: all the test were made with a seeder waist of 131 um
 

With Benoit we move the signal from channel n°3 to the channel n°7 of the same ADC card (slot1, ADC40).

Now the signal seems back to normal, although the 50 Hz contribution is higher by a factor 2: 0.5V pp instead of 0.25V before May the 28th; this may be due to the experiment itself rather than  from the ADC board.

Not investigated so far

since May the 29th the signal PSTAB_HF_CORR is imprinted with a 10 kHz oscillation (plot2)

PSTAB_HF_CORR feeds the AOM, it is the cobination of a 3,5 V offset and an AC part releavant to the RIN to be compensated

- this oscillation results in a mean value of 2 V visible on the trend data (plot1)

- it seems there is no impact on the Pstab perf: plot3: we see that nor the Pstab error signal nor the correction signal are affected.

we don't know yet whether this concerns only the monitoring part

- we 've checked this morning the associated signal into the rampauto with a multimeter. We found 3,47 V. To be done again with a scope since we don't know how the multimeter deals with HF oscillation

Remark: This signal is usefull to assess the power balance at PSL since it says which amount of power before the PMC is spared aside for Pstab purpose

We investigated several tests around the neoVAN amplifier with little improvements. A detailled entry shall be posted soon.

A summary:

- check the susceptibility of the neoVAN beam profile with a stress applied on the fibers, seems non negligeable. More specifically for the fiber n°2

- B. Schultz moved the matching lens between the pairs of crystals (MLBPC) inside the neoVAN to check whether the neoVAN is put in the good direction: little improvement: means little gain to expect by flipping the neoVAN

- Bastian Schultz proceeded with fine adjustment of theMLBPC and the lenses which focus the pump on the crystal

-> together with some stress put on purpose on the fibers the situation seems a bit improved (although no major breakthrough)

The plan for tomorrow is to swap the present fibers with the ones (still in place) of the V+ amplifier. Indeed as mentionned by B Schultz when AEI did the commissioning of our ampli they used supposedly same fibers (apart from the length: 5m only ).

btw, looking under the floor in th elaser lab and atrium, we 've found them "flooded". It seems to come from the roof in the corridor of the IMC (aside to the north wall)

Night shift summary (more data to come later):

- we install a long rail before the neoVAN in order to ease the possibly needed sliding of the Slave-to-neoVAN telescope

- we realign the DiagnoBox dedicated to the neoVAN and got hence back the signal PSL_AMPL_DC to nominal value (misalignment due to the required tilt of a tap-off plate to feed temporarilly a beam-profiler).

- we check other various configuration for the seeder size (120, 130, 160 um waist) and position with always more or less the same beam shape and power at the neoVAN output.

- we would need to check the pumping diodes of the amplifier in case some of them could be down-rated for any reason

At the end little progress...

The neoVAN pump config is now 4,2 A and 5,3 A and the PMC_TRA = 63 W (AOM is driven)

before we leave the beam is bloqued at PSL bench and the PMC is scanned

we spent the shift to try various seeder size & position wrt the neoVAN with not much progress

we left the Lab with 62 W at PMC output.

- The PMC is scanning

- The perturb cable is connected to the rampauto perturb channel

- we let the flip mirror in lower position, the beam can be available on EIB

details on the night shift to come later.

we mesure the power at LB_M9 (neoVAN output), at LB_M11 (AOM output) with and witout the block "L/2 - Brewster polar - L/2" right before the AOM).

we deduce: