Increasing the FP-cavity power , posted by Ronic Chiche at ThomX igloo about lasers and optics
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Last friday, with Daniele, we did some realignement on the 2nd CVBG of the compressor : the beam shape seems better, now.
this morning, we checked that the injection path (periscope and injecton mirrors) is not sensitive to the polarization state of the beam.
we checked also the power at the input of the FPC for 70% amplifier ratio : 40W ! |
New design for PDH boxes, posted by Ronic Chiche at Optical room about detectors and electronics 
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A new design has been studied for the 5 PDH boxes to better match the low (33MHz) repetition rate of the ThomX laser.
the 5 PDH boxes have been modified and tested (see the attached report).
A mixer has been integrated to the PDH box for a more simple use. |
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New locking scheme, posted by Ronic Chiche at Optical room about detectors and electronics
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Before, the locking scheme was to produce an error signal with the PDH box, send its output to the electronic amplifier box and then to the laser EOM
for the fast loop and to the Laselock input. The drawback was changing one loop gain, changes also the other loop gain.
Now, the locking scheme is the error signal coming from the PDH box is directly sent to the Laselock input and in a same time to the electronic |
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lock oscillateur 33MHz - synthé 500MHz, posted by Ronic Chiche at Optical room about detectors and electronics
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pour préparer le lock cavité-anneau, j'ai un setup de lock en salle optique entre le laser OneFive 133MHz et un synthé à
533MHz (133MHz x4).
ce matin, j'ai pu locker les 2 ensembles avec le laselock avec une stabilité RMS, je pense inférieure à la ps. |
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lock oscillateur 33MHz - synthé 500MHz, posted by Ronic Chiche at Optical room about detectors and electronics
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régler le problème 1:
Kevin m'a apporté un déphaseur Minicircuits JSPHS-661 (400-660MHz / 180° de phase) qui permet de déphaser le 500MHz
de ~ 1ns avec une tension DC 0-10V. |
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lock oscillateur 33MHz - synthé 500MHz, posted by Ronic Chiche at Optical room about detectors and electronics
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Today, I installed a DB9-DB9 female-male cable on the PZT connector of the FP-cavity.
the PZT is connected between pins 1 and 2, with a capacitance around 70nF.
I need to make a prolongator cable BNC-DB9 female to connect it to the feedback system. |
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lock oscillateur 33MHz - synthé 500MHz, posted by Ronic Chiche at Optical room about detectors and electronics
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Today, I connected the BNC-DB9 female prolongator cable to the FP-cavity PZT cable (DB9-DB9) and to the channel B of the Laselock.
I additionnaly connected the reflected laser beam (normally connected to scope ch2) to the spectrum analyzer @ 1GHz to observe the 30th harmonic
of the laser comb. |
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ThomX ring injection kicker noise => USB communication issue with Alphanov amplifier, posted by Ronic Chiche at ThomX igloo about detectors and electronics
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several times already, when the electrons ring injection kicker is running @10Hz, we observed peaks at the same frequency on reflected and transmitted
photodiodes,
at the exact moment when the kicker is activated. we have in addition, USB communication issues with the Alphanov amplifier... the connection is |
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lock oscillateur 33MHz - synthé 500MHz, posted by Ronic Chiche at Optical room about detectors and electronics
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this afternoon, I installed the frequency detection scheme in the bunker :
- I changed the large reflected photodiode DET100 by a fast small DET10.
- a 50ohms splitter is connected to the photodiode : |
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lock oscillateur 33MHz - synthé 500MHz, posted by Ronic Chiche at Optical room about detectors and electronics
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this afternoon, I tried to lock the FP-cavity on a local 500MHz synthesizer as a frequency reference
(it's faster to change the frequency from the sythesizer than from the FP cavity !!!)
I found some parameters on the PID of the Laselock to phase-lock the reference and the FP-cavity |
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lock oscillateur 33MHz - synthé 500MHz, posted by Ronic Chiche at Optical room about detectors and electronics
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this morning, I added a Thorlabs lowpass filter at 1kHz after the mixer and a resistor at the Laselock output to the FP-cavity PZT.
I set the PID with P=10 and I=D~0
in attachement, a plot of the 500MHz mixer output, before and during the lock. |
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lock oscillateur 33MHz - synthé 500MHz, posted by Ronic Chiche at Optical room about detectors and electronics
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this afternoon, I firstly connected the HV output of the Laselock to the FP-cavity PZT : https://elog.lal.in2p3.fr/FPC/THOMX+commissioning/248
locking the FP-cavity on the local synthesizer works better with the improved HV output range.
the ~20Hz oscillation in the beating signal of the FP-cavity/synthesizer is still there. |
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lock oscillateur 33MHz - synthé 500MHz, posted by Ronic Chiche at Optical room about detectors and electronics
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this afternoon, we were able to lock the laser on the FP-cavity and the FP-cavity on the Ring reference oscillator in a same time from the control room.
the procedure when laser, cavity and reference oscillators are far in frequency, is :
1) start the amplifier to get the laser signal in the reference photodiode used to measure the 33MHz. |
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lock oscillateur 33MHz - synthé 500MHz, posted by Ronic Chiche at Optical room about detectors and electronics
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after a sudden FP-cavity Finesse increase, we had to install the Fast Feedback Loop in order to continue to lock the cavity.
this afternoon, I was able to lock both the FP-cavity and the Laser on the 500.25MHz oscillator reference.
I had to change the CEP to reduce the effective Finesse and help to get a better stabililty => P ~ 25kW inside the FP-cavity for 30% of laser |
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bunker temperature curve, posted by Ronic Chiche at ThomX igloo about detectors and electronics
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Adding one photodiode in reflection, posted by Ronic Chiche at ThomX igloo about detectors and electronics
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this morning, I added a DET36 photodiode in reflection (I used a thin beam splitter) to better measure the coupling over the full beam size.
this DET36 photodiode is sent to the "laser locking" oscilloscope with the other signals :
CH1 :transmission |
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First stable X-rays production, posted by Ronic Chiche at ThomX igloo about detectors and electronics
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this morning, we locked the laser on the FP-cavity with about 48-49kW stable in the FP-cavity (for 32% of amplifier ratio).
and then we locked the FP-cavity on the RF reference (500MHz beating lock + 33MHz beating for starting lock search).
the starting lock search voltage has been chosen between -20mV and +20mV. |
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locking, posted by Ronic Chiche at ThomX igloo about detectors and electronics
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during the last days we changed the FP-cavity - RF reference locking system to force the right bucket:
in addition to the 500MHz beating which is the signal input to the PID, we added a 33MHz beating signal which is the trigger signal of the PID.
then, the lock is triggered only when this trigger signal is close to 0. |
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lock oscillateur 33MHz - synthé 500MHz, posted by Ronic Chiche at Optical room about detectors and electronics
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This morning with Daniele, we changed the laser/RF locking scheme :
1) we use the laser 33MHz internal photodiode to do some beating with the 33MHz RF generator (A Rigol generator locked on the 500MHz Ring oscillator).
this beating is only for monitoring purpose, in order to manually adjust the laser frequency at the beginning of a run. |
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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. |