ELOG THOMX commissioning

each time, we had a problem with the software, asking to switch OFF and ON the controller before being able to switch the amplifier diodes ON.
we switched OFF and ON many times without any success.

in the end, Aurélien called Guillaume from Alphanov... and without changing anything, it worked... strange!

one possible problem could be the correct detection of Frep of the seed laser (OneFive).
as we didn't check the signal coming from the seed laser, it could be the reason... to be confirmed.

the present status for the controller is:
- the power connector (on the rear side) is ON
- the green relay (on the rear side) is ACTIVATED
- the key (on the front side) is OFF
- the emission button (on the front side) is OFF

the normal procedure to start the controller is:
- switch the front side key ON
- start the software (possible error msg asking to switch OFF and ON the power button: don't do that)
- switch the emission button on the front side (which is red) ON
- switch the preamplifier button ON
=> all the software LEDs should be green and the PD_PULSE window should indicate 133.33MHz
otherwise, try a RESET on the software and restart the procedure (and pray).

at the end of the day, we successfully switched ON the preamp and increased the Power adjustment around 20% to get something about 10W on the big PowerMeter placed at the output of the amplifier.
=> we need another day of practice to be more confident with the software!

143

Fri Apr 8 13:15:18 2022

First hands on the Alphanov amplifier & software

Software Works well and is operational.

Just closing the log series!!!

Ronic Chiche wrote:

Additional information related to the injected power into the amplifier fibers.

power = 4.45 mW (as shown from the software)

the minimum to inject into amplifier is 2 mW

Ronic Chiche wrote:

Aurélien, Manar, and I spent more than 2h trying to start the software communicating with the Alphanov amplifier controller.

each time, we had a problem with the software, asking to switch OFF and ON the controller before being able to switch the amplifier diodes ON.
we switched OFF and ON many times without any success.

in the end, Aurélien called Guillaume from Alphanov... and without changing anything, it worked... strange!

one possible problem could be the correct detection of Frep of the seed laser (OneFive).
as we didn't check the signal coming from the seed laser, it could be the reason... to be confirmed.

225

Wed Jun 28 19:01:03 2023

First X rays and FP-cavity mode and electron beam waists size @ IP

on friday 23/06 afternoon, after scanning the hexapod z-axis, we observed a cut of the power stored in the FP-cavity (with constant input power/coupling) at both ends of the scan, due to the losses of the beam-pipe aperture.
we placed the hexapod exactly in the middle of this range ~ z=-1.68 mm (which is not the middle of the maximum range of the hexapod), we opened the slits on the X-table and we found the first signal.

after scanning, shuting the laser beam and electron beam ON and OFF, we confirmed this signal was coming from X-rays.

on monday 27/06, roughly in the same condition (25kW of power stored in FP-cavity), we scanned properly the same z-axis with the hexapod and we measured the pico-ampermeter current related to the produced X-rays to get the approximated size of the laser and electron beams at the IP position : see the raw data.

Daniele did the data analysis : see the attached analyse_profil_vert_X-1.pptx file
the total rms size (sigma of the Gaussian profile) is 100µm.

this morning, we measured the FP-cavity waist size by measuring the waist size of beam at the focal distance of a lens used after the spherical mirrors.
we measured the rms size of the FP-cavity mode to be 60µm in agreement with simulations, which leads to 80µm rms for the electron beam waist size.

Attachment 1: Raw_data.jpg

Attachment 2: analyse_profil_vert_X-1.pptx

Thu Oct 10 18:03:10 2019

First Lock with 2nd satge of amplifier : Motor issue ?

Global locking almost clean : tranmission and reflection are quite noiseless except the peaks at every 500ms.

During the amplifier 2nd stage lock, we experienced 2 strange behaviors :

- short "unlocks" every 500ms exactly all the time, during the whole lock process

- some PZT (in green on the picture) shift exactly synchronized with these "unlocks" (see the red circle).
these shifts are triggered by some OneFive motor move (Frep adjustment).

We tried to disconnect software activity (use the disconnect button on the software), to disconnect USB cable, to disconnect power supply of the motor controller box but none of these actions had an effect
=> still short unlocks every 500ms...

The amplifier 2nd stage seems to have small fan for the power supply... we can try to disconnect it.

We tried to turn on the 3rd stage which uses several fans for cooling the pump diodes... thus, one can see immediatly a big increasing in the PZT signal which tries to compensate the vibrations and quicly one loose the lock.
we have to think on how to suppress these vibrations.

Attachment 1: Image1.png

Tue Nov 26 16:11:52 2019

First Lock with 2nd satge of amplifier : Motor issue ?

The 500 ms noise disapeared. We had to disable the "power save" mode of the smaract translation stage. AND turn OFF and ON the controler box.

Ronic Chiche wrote:

Global locking almost clean : tranmission and reflection are quite noiseless except the peaks at every 500ms.

During the amplifier 2nd stage lock, we experienced 2 strange behaviors :

- short "unlocks" every 500ms exactly all the time, during the whole lock process

- some PZT (in green on the picture) shift exactly synchronized with these "unlocks" (see the red circle).
these shifts are triggered by some OneFive motor move (Frep adjustment).

The amplifier 2nd stage seems to have small fan for the power supply... we can try to disconnect it.

Thu Oct 10 17:51:26 2019

Ronic Chiche

Fixed

issue

lasers and optics | detectors and electronics

Optical room

First Lock with 2nd satge of amplifier : Finesse issue ?

1st lock today with the second stage of the amplifier.
~ 300mW of injected power (but which proportion of the pump and of the signal ? => One must use a spectrometer to determine this proportion)
MAYBE the real injected power of the signal is lower => maybe the Finesse is higher !

Coupling ~ 75%

1.2 mW measured in transmission => ~800W inside the FP cavity
=> Gain ~ 3500 => Finesse ~ 11k !!!

Last Finesse measurement was about 19k ! :-(

Fri Oct 11 18:42:32 2019

Ronic Chiche

Fixed

issue

lasers and optics | detectors and electronics

Optical room

First Lock with 2nd satge of amplifier : Finesse issue ?

First of all, we used and optical spectrometer to determine which proportion of pump and signal is in the injected beam.
the wavelength is THE SAME for the 2nd stage for the beam coming from the core or coming from the clad !
thus, it is impossible to use a spectrometer to obtain this proportion.

Thus, we made the assumption the pump beam (Sp) is unpolarized in contrary to the core beam (Sc) which is almost linearly polarized (Scp, Scs)

with a half waveplate and a PBS, we can define 2 cases in rotating the half waveplate at the output of the PBS :
maximum power : Scp + Sp/2 = a1
minimum power : Scs + Sp/2 = a2
The sum of both power a1 and a2 : a1+a2 = (Scp+Scs) + Sp is the total power of the beam before PBS.
The subtraction of power a1 and a2 : a1-a2 = Scp - Scs is independant of the pump power which can vary for example in opening an iris which normally block the most part of the pump beam.

if the core beam is perfectly linear, Scs=0 => a1-a2=Scp and Sp=2*a2
We did 2 measurements with a1=227mW, a2=67mW => Scp=160mW (Sp=134mW)
and with a1'=277mW, a2'=107mW => Scp=170mW (Sp'=214mW with a wider opened iris)

if these measurements and assumptions are correct, the real power injected to the cavity was 170mW (instead of 300mW).
with a coupling of 75% => Gain ~ 6.3k => Finesse ~ 19.7k !

to be confirmed...

Ronic Chiche wrote:

Coupling ~ 75%

1.2 mW measured in transmission => ~800W inside the FP cavity
=> Gain ~ 3500 => Finesse ~ 11k !!!

Last Finesse measurement was about 19k ! :-(

Fri Apr 5 11:28:39 2019

Finesse with P1 SUPRASIL

P1 SUPRASIL has been installed instead of P1 Sapphire. It has been cleaned 3 times on each face with wipe+isopropanol before to be installed.

Finesse ~= 10 000 - 11 000 (EOM Sweep of 100 kHz in 10sec, see last image.)
Coupling ~= 45%

Motors position:
P1 = -825 000
S2 = +825 000
S3 = +825 000
P4 = -825 000

Attachment 1: 190404_mode_size_with_P1_SUPRASIL.PNG

Attachment 2: 190404_mode_fit_with_P1_SUPRASIL.PNG

Attachment 3: tek00000.png

Attachment 4: tek00002.png

Thu May 23 10:10:56 2019

Finesse measurement by decay time technique

5 Files attached:

- Note on the technique and results for the present cavity on 2019, May 21th : F ~ 18 000

- 2Tektronix scope raw data

- 2 matlab files to fit the scope raw data and extract the Finesse

Attachment 1: 2019-05-21_-_Finesse_measurement_by_decay_time_technique.docx

Attachment 2: tek0005CH1.isf

Attachment 3: tek0006CH1.isf

Attachment 4: plotdata.m

clear
clc

global datacut tcut Trt

[h,data]=myisfread('tek0005CH1.isf');
dt=h.Xincr;
Nt=h.Npoints;
t=0:dt:(Nt-1)*dt;
t=t';

% offset removing
offset=mean(data(0.9*Nt:Nt));
data=data-offset;

% magnitude calculation
datamax=mean(data(1:0.1*Nt));

% cuting data to remove constant part at the beginning of the signal
% and where log(data) becomes complex (signal close to zero is sometime negative)
id1=find(data<0.967*datamax);
id2=find(imag(log(data))~=0);
tcut=t(id1(1):id2(1)-1);
datacut=data(id1(1):id2(1)-1);

%fit
L=9;
c=3e8;
Trt=L/c;
rho=1-1.5e-4;
k=1-15e-4;
pc0=0.14;
t0=2e-3;
x0=[rho k pc0 t0];

options = optimset('Display','iter','PlotFcns',@optimplotfval,'TolX',1e-7,'TolFun',1e-7);
x=fminsearch('myerror',x0,options);

rho=x(1);
k=x(2);
pc0=x(3);
t0=x(4);
datafit=pc0/(rho-k)^2*((1-k)*rho.^((tcut-t0)/Trt)-(1-rho)*k.^((tcut-t0)/Trt)).^2;

%%
figure(1)
clf
plot(t*1e3,data)
grid on
xlabel('Time (ms)')
ylabel('Transmited power (A.U)')

figure(2)
clf
plot(tcut*1e3,log(datacut))
hold on
plot(tcut*1e3,log(datafit),'.')
grid on
xlabel('Time (ms)')
ylabel('Log(Transmited power) (A.U)')
legend('data','fit')

Tpin=Trt/2/abs(log(k));
Tcav=Trt/2/abs(log(rho));
F=2*pi*Tcav/Trt;

disp(['Finesse                 : ' num2str(F)])
disp(['Cavity decay time : ' num2str(Tcav*1e6) ' �s'])
disp(['Pin sw decay time : ' num2str(Tpin*1e6) ' �s'])

Attachment 5: myerror.m

function [ output ] = myerror( x )
%MYERROR Summary of this function goes here
%   Detailed explanation goes here

global tcut datacut Trt

rho=x(1);
k=x(2);
pc0=x(3);
t0=x(4);

mydata=pc0/(rho-k)^2*((1-k)*rho.^((tcut-t0)/Trt)-(1-rho)*k.^((tcut-t0)/Trt)).^2;
output=sum((mydata-datacut).^2);

end

101

Tue Jul 7 12:49:38 2020

Finesse measurement after the Edge installation

After the Edge installation inside the cavity, the Finesse has been measured several times by modulation technique with an average around 16000:
(the scan speed is 50kHz in 10 seconds.)

So, it hasn't changed since the last measurement in June, just before the Edge installation.
The Edge position is normally the furthest from cavity beam (all rotating knobs are at 0 positions)

We used the last Onefive telescope (used with CVBGs). Coupling reached ~50% after alignment.
The cavity vacuum is ~7.2e-9 mbar as the cavity has been recently opened...

Attachment 1: untitled.png

Fri Aug 30 09:44:56 2019

Finesse measurement after mirror cleaning using the spin coater

Last Finesse measurement in air : ~ 17 000 the 20th of may (see logbook)

28th and 29th of august, we cleanned, with Loïc, mirrors S3 then P1 successively using only ultra pure water with the spin coater.

we measured the finesse after each cleaning by modulation technique and in both cases, F ~ 12 500 !!!

maybe the mirror surfaces have been covered by some hydrocarbure during the summer ?
or by an other contaminant which is difficult to clean with only water ?
we decided to clean the mirrors first with an isopropanol solution and then with ultra pure water and the spin coater.

Fri Aug 30 17:46:15 2019

Finesse measurement after mirror cleaning using the spin coater

today I cleaned S3 with isopropanol and then with pure water on spin coater.
Finesse is only 10 700.(coupling 50% ? => to be confirmed...)

maybe we have to redo the procedure with a different way of cleanig (pushing less on the mirror ... ?)

Ronic Chiche wrote:

Last Finesse measurement in air : ~ 17 000 the 20th of may (see logbook)

from 28th to 30th of august, we cleanned, with Loïc, mirrors S3 then P1 successively using only ultra pure water with the spin coater.

we measured the finesse after each cleaning by modulation technique and in both cases, the finesse did not change !

Tue Sep 3 18:04:03 2019

Finesse measurement after mirror cleaning using the spin coater

Following finesse measurements (start @10700):
Clean P1 with SC (water) + isoprop (wipe) finesse @15000
Clean S2 with SC (water) + isoprop (wipe) finesse @13000
Clean P4 with SC (water) + isoprop (wipe) finesse @11000

We have to take into account that "cleaning" the mirror change the alignment axis in the cavity so the finesse can change because of that. It would explain the erratic nature of these results which seem to not show any effective cleaning.

Ronic Chiche wrote:

today I cleaned S3 with isopropanol and then with pure water on spin coater.
Finesse is only 10 700.(coupling 50% ? => to be confirmed...)

maybe we have to redo the procedure with a different way of cleanig (pushing less on the mirror ... ?)

Ronic Chiche wrote:

Last Finesse measurement in air : ~ 17 000 the 20th of may (see logbook)

from 28th to 30th of august, we cleanned, with Loïc, mirrors S3 then P1 successively using only ultra pure water with the spin coater.

we measured the finesse after each cleaning by modulation technique and in both cases, the finesse did not change !

100

Tue Jun 16 13:03:52 2020

Finesse measurement after confinement

After 3 months without human presence, finesse has been measured 3 times with average optimization:
- 16150
- 16067
- 16172
Last measurement was on 6th of november 2019, finesse was 17000. So it didn't change or just slightly.

We used the last Onefive telescope (used with CVBGs). Coupling reached ~30% (see pink curve on image attached).
Cavity vacuum is ~1.2e-9 mbar and pneumatic valves were still openned after these 3 months.

Attachment 1: sweep_parameters.PNG

Attachment 2: tek00007.png

Attachment 3: tek0009CH1.isf

Attachment 4: tek0010CH1.isf

Attachment 5: tek0011CH1.isf

Fri Sep 27 16:17:36 2019

After mirrors were going back from LMA for cleaning and thermal anealing, they have been installed in FP cavity for Finesse measurement.

after getting strange results when the cavity is closed (very low Finesse...maybe too much ethanol inside cavity procucing some lineic losses), we get 12k-12k5 Finesse with primary vacuum (~4 mbar) and a clean lock (very flat transmission signal and quite noiseless reflection signal)
we let the cavity pumped all the WE to see if we can measure a difference or not at lower pressure.

Mon Sep 30 11:30:32 2019

To complete these observations:

Finesse has been measured on thursday, right after cleaning the cavity with ethanol @6000.
Finesse has been measured on friday, after opening the cavity for few tens of minutes @12000-12500. The cavity was openned while locking and the transmission was continuously and ~linearly increasing.
Finesse has been measured today after ~50h pumping with primary vacuum @17000. It's back to the highest value we've ever measured on this cavity.

Parameters @17000 finesse:

Input power: 7.85 mW (Koheras + AOM + 2*EOM)
Coupling: 70-75% => Pin ~ 5.9 mW
Transmission through S2 and P4: 50 µW (transmission estimated to 1.5 ppm) => Pcav ~ 33 W => G ~ 5600
It is compatible with a simulation with nominal parameters for mirrors and adding 47ppm by mirror of losses (absorption and scattering) which indicates 17k of Finesse and 4100 of power gain.
in this simulation, the coupling should be 94% instead of the 70-75% measured. It is possible that the losses (47 ppm) are not the same on all mirrors.

Ronic Chiche wrote:

After mirrors were going back from LMA for cleaning and thermal anealing, they have been installed in FP cavity for Finesse measurement.

Tue Apr 2 17:59:18 2019

Finesse after removing wires

19/04/01: We removed the wires from the beam path in the cavity. Finesse stayed at 3400. FSR: 33.342 MHz.

When locked:

Input Power: ~4mW
Through S2: ~0.950uW
Through S3: ~0.930uW
Through P4: ~0.850uW

Tue May 21 17:49:30 2019

Finesse after cleaning (new suprasil mirror)

15/05/19-20/05/19:

Cleaning of the mirrors:

Initial finesse 14000 @air
S2 with isopropanol, finesse 17000 @air
P4 with isopropanol, finesse 17000 @air
S3 with isopropanol, finesse 17000 @air
S3 with first contact, finesse 17000 @air
S2 with first contact, finesse 17000 @air

Mon Apr 8 10:18:31 2019

Finesse measured this morning after P1 SUPRASIL being into the cavity for two days. In order to check if it's getting dirty.

Finesse still ~= 11 000

363

Mon Sep 16 12:03:30 2024

Finding correct motors position and parameters to keep the lock during a move

this morning, I try to find a new region for MOT.03 and MOT.06 where we can move them without unlocking the cavity.

I started from the position:
MOT06 : ~ -785 000
MOT03 : ~ -200 000

and I do -10 000 steps (dz = 10k x 6nm = 60µm) at a time on both motors.
previously a good region for MOT.06 was -900 000 !

I moved also the laser cavity by 40µm to cancel the beating with the RF frequency.

MOT06 : ~ -795 000
MOT03 : ~ -191 000

Max power after optimazing the CEP ~ 65kW => I need to realign => 78kW
I need to increase the D parameter on the PID to compensate the (85kW / 78kW ratio).

I changed the MOT.03 and MOT.06 speed to 30steps/s => it seems a bit better.
but I still see some lock losses during a move.

.... to be continued...

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