Laser Amplifier used at 70%, posted by Ronic Chiche at ThomX igloo about lasers and optics 
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today, I installed a laser dump just before the telescope to avoid any high power (50W instead of 17W usually) issue in the injection line.
last time, we saw some plastic mounts of the polarizers slightly burnt because of some small misalignment.
I used a thorlabs LB2 (see picture) which is able to manage 80W CW or 25J/cm2 pulses => this is OK in both cases : 50W CW / 1.5µJ/pulse |
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High frequency noise, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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Today, the lock of the FPC was particularly bad (maybe the worst ever seen), with a lot of high frequency noise.
the lock was impossible during several minutes !
we tried to switch off all the equipments of the machine, one by one without any effect on the lock. |
High frequency noise, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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At the end of the day, we found out what was the origin of this noise : some road renovation work with jackhammer and road roller just at the entrance
of the "Igloo".
this origin was 100% correlated with a large increase of the accelerometer signal. |
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High frequency noise, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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After this observation, we did a test with Daniele to try to correlate the road traffic in front of the Igloo with the lock losses observed on the FPC.
We didn't see any clear correlation. Cars or buses are not the direct origin of the FPC lock losses... only when some heavy load is hitting
the building, we observed a clear correlation. |
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High frequency noise, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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we did some tests with Marie to make some vibrations on the door.
below, I exhibit some pictures of the scope with the accelerometer plugged on it without or with noise...
this level of noise is not able to make the FPC loosing the lock. |
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High frequency noise, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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This morning, I installed a high-voltage probe (1:1000) on the AC-line to see if one could detect a correlation between lock losses and AC-line voltage
variations.
I observed many lock losses but without any variation or correlation of the AC-line signal (scope set in "peak detect" with "envelope" |
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Noise issue, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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since several days, we see that the locking is more and more unstable and the lock duration was sometime less than 20-30 seconds !
1) I tried to optimize the feedback loops
I discovered that the gain on the fast loop on the laser EOM was very low and was almost uneffective for the global stability of the lock (I |
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Noise issue, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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yesterday, in the same conditions, we had so many locking issues... exactly in the same way than before. :-(
so we still have "locking issues" depending on something we didn't find...
today, we removed the "1/2 voltage divider" before the PZT amplifier to get back the full dynamic. |
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Power shut down on September 23th, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | vacuum | detectors and electronics | cabling | software | utilities
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to anticipate the power shut down on next tuesday 23/09,
this afternoon, I switched off all the equipments except the oscillator connected on the UPS. |
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Power shut down on September 23th, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | vacuum | detectors and electronics | cabling | software | utilities
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this morning, I restarted all the equipments of the FPC.
everything was fine after being able to get back the correct PDH phase between modulation and demodulation...I got 88kW with 33% amplifier ratio
after basic alignment and CEP tuning. |
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Power shut down on September 23th, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | vacuum | detectors and electronics | cabling | software | utilities
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the 33MHz/500MHz RF frequencies from the Ring seems different from the previous state (maybe working at an energy of 50MeV instead of 70MeV which was
the previous energy ?).
so, I let the FPC at the present position and wait to discuss if it is necessary or not to move the FPC motors for the correct energy... |
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Power shut down on September 23th, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | vacuum | detectors and electronics | cabling | software | utilities
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This morning I did a phase alignment on the PDH signal generator (Rigol DG4102)
this procedure ensure that both phases of the sine wave signals are aligned before finding the correct phase for maximizing the error signal.
so, from now on, in case of power shut down, one just need to : |
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Accelerometer measurement, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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with Daniele, we placed the accelerometer on top of the fiber amplifier box which is inside the housing.
the goal was to try to detect a correlation with some possible accoustic noise coming from the bubbles of the water, cooling the amplifier box baseplate.
we monitored a long trend of the transmission which is perturbated when high frequency noise arises, and the accelerometer signal. |
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polarization measurement of the FP cavity beam, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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today, with Daniele, we did a simple polarization measurement in transmission of the FP cavity beam.
1) we locked the FP cavity and measured 82.5kw (for 33% amplifier ratio) with the power-meter moved a little bit further (this is maybe the reason
why the power is a little bit lower than usually measured). |
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Power shut down on August 29th, posted by Ronic Chiche at ThomX igloo about detectors and electronics
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This morning, all the equipments have been switched off due to a power shut down tomorrow morning.
Only the Onefive oscillator is still ON, connected to the Uninterruptable Power Supply (UPS). |
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Power shut down on August 29th, posted by Ronic Chiche at ThomX igloo about detectors and electronics
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after alignment, CEP adjustment and optimizing the PDH phase, I got back ~92kW in the FPC for 33% amplifier ratio.
Ronic
Chiche wrote:
This morning, all the equipments have been switched off due to |
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Alignment correction during the summer break, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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I restarted the FPC system this morning.
after some classic alignement procedure (some LEFT steps on the cavity injection motors X & Y) and CEP tuning,
I got 92kW for 33% amplifier ratio. |
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laser operation again with machine OFF, posted by Ronic Chiche at ThomX igloo about lasers and optics
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The laser start at 33% with 92 KW optimized and
P=0.03
I=0.0005 |
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Xrays experiment with prostate, posted by Ronic Chiche at ThomX igloo about lasers and optics
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Today we do XRays for experiment.
The laser start to 33% at 93 KW but Pgain = 0.033
The laser is locked so stable for the moment. We have Xrays and the system is stable. |
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Suite tests stabilité, posted by Ronic Chiche at ThomX igloo about lasers and optics
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We continue to find what gives high freq. perturbation.
The laser starts at 92 KW it is stable and locked to the RF. NO high freq parturbation.... With the machine off. (30 min of lock)
We put now the machine ON (All in warming exept pulsed elements)... => the system is very stable NO delock, NO high freq perturbations. The |
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Stability test Without and with , posted by Ronic Chiche at ThomX igloo about lasers and optics
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The laser starts at 93 KW.
This morning I operated the laser locked with the RF for 1h30 without any delock. All the machine was switch off.
All the system was very stable. Sometimes the 20 Hz perturbation was visible but no delocking. |
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Tuning of the slow feeback loop analog BW + fast feedback loop gain + PID, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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Today with Daniele, we tuned the potentiometer after the Laselock which drives the analog BW of the PID on the laser PZT,
and we tuned also the fast loop gain (with the rotary potentiometer dedicated to it) => the PID parameters have changed.
so, the recipies has changed => to be updated |
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New recipies with additionnal attenuation before the diffuser, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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With optical attenuation only
For ~ 92kW power in the FP-cavity:
Alplhanov amplifier ratio : 33% |
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New recipies with additionnal attenuation before the diffuser and new x3 amplifier on laser PZT, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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With optical attenuation + x3 amplifier on laser PZT channel + feedback tuning
Temporary recipie for ~ 92kW power in the FP-cavity:
(in the previous scheme, without x3 laser PZT amp, a good lock was achieved for a PDH signal power noise ~ 70 mV rms) |
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laser PZT amplifier, posted by Ronic Chiche at ThomX igloo about detectors and electronics
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this afternoon, I added the Gain = 2.8 amplifier at the output of the Laselock to drive the laser PZT.
the power supply of the board is disymetric to address the correct maximal dynamic range of the amplifier (~ 30V) and voltage drop (~ 2V) related
to the power supply voltage. |
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long run to test the appearance of high frequency noise, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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Today with Daniele, we did 6 long runs at different power (23kW, 46kW, 66kW, 73kW, 92kW, 92kW)
All the lock loss in between these several runs are due to FPC locking parameters change.
most of the few lock losses during the stable power duration, are due to 20Hz oscillation noise or because we forgot to center properly the PZT |
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long run to test the appearance of high frequency noise, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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today, long run directly at full power (33% amplifier ratio) => 98kW in the FPC at the very begining of the run.
(P=0.05 / I=0.0005 / D=0.6)
10-40 min : almost misalignment effect (CEP did not change so much) |
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optical attenuator added on the diffuser + new PID parameters, posted by Ronic Chiche at ThomX igloo about lasers and optics | detectors and electronics
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Today we did several long runs (~1h each) at ~23kW, 46kW, 66kW with different PID parameters which seems better.
P = 0.1
I = 0.0015 |
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Recipies for different FPC power, posted by Ronic Chiche at ThomX igloo about lasers and optics
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For ~ 46kW power in the FP-cavity:
Alplhanov amplifier ratio : 20%
Axis 18 position : -0004710 steps |
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Recipies for different FPC power, posted by Ronic Chiche at ThomX igloo about lasers and optics
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For ~ 23kW power in the FP-cavity:
Alplhanov amplifier ratio : 15%
Axis 18 position : -0016014 steps |
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Recipies for different FPC power, posted by Ronic Chiche at ThomX igloo about lasers and optics
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For ~ 66kW power in the FP-cavity:
Alplhanov amplifier ratio : 25% |
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day by day run for X-ray production, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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the RF frequency changed from 500.1003MHz to 500.0913MHz => it reduced by 9kHz @ 500MHz which is equivalent to 600Hz @ 33MHz (we measured 500Hz @
33MHz). the electron orbit length increased, so we have to increase the cavities length => increase motor values by ~ 68µm.
for the laser cavity : 1.496 560 mm => 1.564 560 mm |
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day by day run for X-ray production, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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at the begining of the day, we started to get ~81kW in the FPC for 33% amplifier ratio and after ~1h, we got 84kW after CEP and alignment tuning.
at the end of the day, we got 89kW without walking alignment.
we tried to improve a bit the robustness of the FPC and RF locks: |
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day by day run for X-ray production, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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today with Alice, we planned to do a long run with ~80kW in the FPC to check if the lock problems are coming from the interaction with the machine or
not.
the goal is to check this assumption on a full day comparable with a day of X-ray production. |
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day by day run for X-ray production, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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we observed that :
- the MOT.03 motor always exhibits some perturbations on the transmitted, reflected and PZT signals (see "peaks" in the picture) in
contrary to the MOT.06 motor. |
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day by day run for X-ray production, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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last thing we tried :
we removed the threshold on the FPC/RF error signal.
=> we cannot choose automatically the RF bucket anymore (we need to manually let the phase drift slowly and start the lock at the right moment). |
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day by day run for X-ray production, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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This morning, I added an amplifier on the 33MHz beating signal in between the mixer+LPF and the scope/Laselock.
it seems to improve the robustness of the RF/FPC lock.
because of this gain, I increased the upper and lower thresholds on the search criterion of the RF/FPC lock from +/-50mV to +250mV/-200mV |
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day by day run for X-ray production, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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major result of the day: X-ray vertical scan by moving the hexapod
abscise : hexapod position
ordinate : xray flux in asynchronous condition |
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day by day run for X-ray production, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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this morning, Kevin reduced the steering current in the IcePap controllers of the FP cavity motors.
the motor MOT.06 was producing a pattern in the Transmission signal when it was moved and doing a lock loss very often.
so, we changed its current from 0.8A to 0.4A and it fixes the problem => no more systematic lock loss. |
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day by day run for X-ray production, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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this morning, I restarted the cavity after the Christmas shutdown.
everything went fine.
I got ~ 86kW for 33% laser amplifier ratio after optimization of the CEP and alignment with walking procedure. |
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day by day run for X-ray production, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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today we did x-rays => we got 41 000 pA at maximum and 90kW in the FPC for 33% amplifier ratio.
finally, I changed the strategy for the feeback on RF.
i removed the integration and derivative parameters and reduced the gain parameter : |
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day by day run for X-ray production, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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this morning, I restarted the lock of the CFP after almost 2 weeks without operation.
after quick alignment and CEP tuning, I got 88kW for 33% ratio for the laser amplifier.
the FPC seems pretty far from the RF frequency (2.8kHz @ 33MHz) but it's possible the present RF frequency has been tuned for 61.5 or 70MeV |
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day by day run for X-ray production, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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this morning, the cavity was pretty misaligned => basic alignment in y direction helps a lot => 93kW for 33% amp ratio.
the Rigol 33MHz generator phase was adjusted : phase ch2 = phase ch1 (40 deg) + 36 deg = 76 deg.
Ronic |
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day by day run for X-ray production, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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today, the alignment of FP cavity was so bad that I tuned the 01 mode by error (CEP and alignment)... insead of the 00 mode !!!
I was able to reach ~30kW and was limited at this value, so I used the camera to check what was happening and saw the 01 mode.
so, I moved the lock on a 00 mode and redid a full tuning (CEP and alignment). |
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day by day run for X-ray production, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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today, after 1 week of vacation, I was able to easily lock the cavity with 92kW with 33% amp ratio without too much optimizations (no walking alignment).
could it be related to the nice weather we got during this week ?
as in the past we observed more noise when the weather was changing and we had very difficult locking procedure after a simple weekend... |
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day by day run for X-ray production, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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Today, I removed the NKT oscillator from the bunker to put it in the PLIC room.
I locked the FP cavity and obtained 97kW with 33% amplifier ratio, without any alignment, just by changing a little bit the CEP.
Ronic |
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day by day run for X-ray production, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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New locking parameters (I got 98kW for 33% amp ratio) :
Axis 18 position : +0009420
P = 0.05 |
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day by day run for X-ray production, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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We had a long run without any lock loss during ~1h with the 23kW recipie in the morning.
during the afternoon, we had some few lock losses but the FPC system was globally quiet and stable,
but at the end of the day, I observed more and more frequent high frequency noise which implies lock losses. |
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day by day run for X-ray production, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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long run yesterday at relatively low power (~23kW) with double loop (FPC + RF) between 10am and 6pm
Ronic
Chiche wrote:
We had a long run without any lock loss during ~1h with the 23kW recipie |
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day by day run for X-ray production, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | detectors and electronics
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long run today at relatively nominal power (~90kW) with double loop (FPC + RF) between 13:30am and 6:30pm
Ronic
Chiche wrote:
long run yesterday at relatively low power (~23kW) with double loop |
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Possible causes for the noise in the FP-cavity system, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | vacuum | detectors and electronics
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list of possible causes of the high frequency noise which makes the system loosing the lock => to be checked.
(if you have some new idea, I will edit the post)
1- Laser |
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Possible causes for the noise in the FP-cavity system, posted by Ronic Chiche at ThomX igloo about mechanics | lasers and optics | vacuum | detectors and electronics
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4.3 - Vibrations of the mirror mounts due to temperature related to cavity power (the electrons machine is OFF)
1) to test this possible issue, we plan to make a run at low power in the FP-cavity, around 10kW, instead of ~90kW as usual.
for that, I will need to change the diffuser position on axis 18 to get the same error signal for the locking. |