| ID |
Date |
Author |
Category |
Subject |
|
136
|
Thu Apr 7 11:11:31 2022 |
Max, Sebastian | Laser | dye changed, pulse energy measurements |
We changed the dye at 10am.
We increased the pump power for the dye Laser to 480mJ (before 450mJ). New calibration factor is 29 for Quanta Ray monitor signal.
We get now 17mJ UV pulse energy after SHG. Pulse energy before was 14mJ. |
|
145
|
Fri Apr 8 00:06:37 2022 |
Patrick | Laser | Connection to the laser pc |
To login to the laser pc use the command
xfreerdp -g 1920x1080 -u atplaser atppc023.campus.gsi.de |
|
148
|
Fri Apr 8 02:14:05 2022 |
Wilfried | Laser | Laser timings adjusted |
Since we use the middle window as a reference for the laser pulse timing, the fact that the window is 2.25 m behind the target has to be taken into account. From here the ions have 10 ns less time of flight to the middle of the electron cooler than they need for half a revolution. The signals were still symmetrically aligned around the reference bunch as it was done yesterday. Therefore, the delay of the laser pulse was reduced by 10-ns on the oscilloscope, which led both photodiode histograms move 3 bins further to the right (towards larger times till common stop, since the pulse arrives earlier).
Since the RF frequency is turned down from ~ 1 MHz to ~ 400 kHz during injection/preparation, the laser does not fire reliably and the beam stabilization does not work very well during this period. This was solved by increasing the window in which the Q-Switch signal is accepted from 2 microseconds to 5 microsececonds. The laser is now firing regularly and with high power also during the preparation time and the beam position stabilization works very well. |
|
149
|
Fri Apr 8 03:54:39 2022 |
Patrick | Laser | Q-switch window |
The solution of increasing the Q-switch window from 2us to 5us described in ID:148 fulfills its purpose, but the window is unstable.
We saw the laser jumping across the screen which was because the Laser had a lot of hickups.
The hickups come from the signal which determines the duration of the window.
This window "flickers". It gets very small, leaving no time for coincident events which fire the laser.
This is probably an issue with the NIM module.
Compare the picture below: The oscilloscope freezes and only the first of the yellow pulses is visible which should repeat and span 5us at the moment.
After looking at the different signals to trigger the laser on the oscilloscope, the laser does not fire anymore when used in the external trigger mode.
However, all signals are looking good and everything should be in the same state as before.
The internal Q-switch works as good as before. |
|
152
|
Fri Apr 8 08:17:52 2022 |
Sebastian | Laser | Laser Ext Trig is working |
We (Max, Kristian, Danyal, me) fixed the "external trigger" problem.
1.) The delay between lamp sync and Q-switch trigger was too long. The delay must be 200µs (3rd picture)!
2.) The settings from the left Dual Timer (upper and lower part) in the ESR Laser Lab (above QuantaRay laser) were wrong and are now adjusted. Settings are depicted in the attached photos (1st and 2nd pic).
4th picture shows the pulse train of the pump laser. |
|
160
|
Fri Apr 8 11:16:57 2022 |
Kristian | Laser | Wavemeter |
We changed the fiber to the wavemeter. The third fiber worked best and we could operate the WM at low exposure times, i.e., below the laser repetition rate. We used the neutral density filter to adapt the laser power that only one laser pulse is measured by the WM each time (Exposure time =34ms)
This way, there are no frequency jumps. The jitter is slighly different at each wavelength which was ~5GHz peak to peak.
We optimized the fiber coupler and slightly optimized the jitter to <4GHz. |
|
180
|
Sat Apr 9 05:26:25 2022 |
Patrick | Laser | Wavemeter |
| The wavemeter still shows large spikes from time to time. The exposure time is still at 34ms. |
|
182
|
Sat Apr 9 06:42:23 2022 |
Kristian | Laser | Laser step size |
We changed the laser step size to 0.002 nm which corresponds to 5.75 GHz. |
|
186
|
Sat Apr 9 16:55:19 2022 |
Rodolfo | Laser | |
16:15 I have changed the dye (of both oscillator and amplifier).
16:27 I have increased the pump energy (@ 532 nm) from 476 mJ to 507 mJ.
- UV output energy @ 322,8 nm: 12 mJ. (Before was at 9 mJ).
- New calibration factor is 160 for Quanta Ray monitor signal. |
|
188
|
Sat Apr 9 19:09:57 2022 |
Rodolfo | Laser | Optimization - Resonator of dye laser |
I have tuned a bit the resonator of the dye laser.
The total output energy after the main amplifier is 86 mJ (@ 645,6 nm)
The laser wavelength read by the wavemeter appears to be more stable (on the windows computer). We can see the histogram once the present scanning is finished. |
|
196
|
Sun Apr 10 08:53:26 2022 |
Kristian, Max | Laser | Timing verified |
timing is still good.
we checked the relative timing between laser and ions. the time difference between photodiodes, PMTs and particle detectors is still the same as original (see ELOG ID 169). The common stop of changed a slightly so that everything appears one bin later. |
|
197
|
Sun Apr 10 11:11:18 2022 |
Kristian, Max | Laser | additional WM readout |
since the WM readout still does not work reliably, I started a python script at atppc023 that saves timestamp and wavemeter frequency. in folder wavemeter at the desktop.
it is about 1 MB / h
Rename the old file and restart when you change the wavelength range. |
|
202
|
Sun Apr 10 15:29:53 2022 |
Rodolfo | Laser | Status - Laser system |
We have checked the laser system.
- The pump laser has ~ 23Mio shots. The total output energy has dropped to about 475 mJ. Maybe it is time to install new fresh flashlamps. In case the accelerator is going to have any mantainance tomorrow (Monday) then we can take the oportunity to exchange the flashlaps.
- The dye laser is pumped with 470 mJ (angle of lambda/2 plate = 112°).
- The energy after the second harmonic is 11,3 mJ @ 646 nm. We are using the Sarper's calibration table (635 nm - 646 nm) |
|
208
|
Mon Apr 11 11:05:35 2022 |
Sebastian, Kristian | Laser | Check laser power |
we checked the UV laser power at 10:15 am. It was only 8.5 - 9 mJ. Pumping power was 460 mJ, which is the maximum output of the current system. We should change the flashlamps soon |
|
211
|
Mon Apr 11 18:46:31 2022 |
Rodolfo, Sarper and Konstantin | Laser | Alignment-check |
We cross-checked the laser-ion alignment. The horizontal position was optimized. However,
since the laser beam is much larger than the ion beam, this was not an issue for measurements, which
have been performed during the last shifts.
The modified parameters of the stabilization system are attached. |
|
212
|
Mon Apr 11 18:57:18 2022 |
Rodolfo | Laser | New flashlamps |
We (Sarper, Konstantin and me) have changed the old flashlamps (with ~ 26 Mio. shots) by new "fresh" ones. We have also exchange the dye. Here are some parameters of the laser we measured with the new flashlamps and dye*:
- Output energy after the Quanta-Ray (@ 532 nm): 598 mJ.
- Seed energy for Cobra (@ 532 nm): 505 mJ.
- Correction factor for monitor; 15.9.
- Output energy after Cobra's main amplifier cell (@ 640 nm): 107 mJ.
- Output energy after SHG (@ 320 nm): 15.8 mJ.
* all values are average over 500 shots.
** below you can see a picture of the "old" flashlamps. |
|
213
|
Mon Apr 11 22:14:51 2022 |
Konstantin, Sarper | Laser | Changing of the wavelength range |
It is planned to change the scan range of the laser wavelength from 322.41 - 322.0 nm to 322.01 - 321.6 nm @ 4 a.m. |
|
220
|
Tue Apr 12 15:05:56 2022 |
Rodolfo | Laser | Laser status |
We have checked the laser power at 14:15 *
- Pump energy after Q-Ray @ 532nm: 559 mJ.
- Seed energy for Cobra @ 532 nm: 505 mJ (before 481 mJ).
- Correction factor for monitor: 28.8.
- UV-Energy after SHG @ 321.6 nm: 13.7 mJ.
* All values are averaged over 500 shots |
|
224
|
Wed Apr 13 15:41:29 2022 |
Rodolfo & Sarper | Laser | Laser status |
We have checked the power of the laser and optimized it "a bit".
- Seed energy for the Cobra @ 532 nm: 508 mJ (before 496 mJ)*
- New correction factor for the Monitor: 43.
- UV energy after the SHG @ 321.1 nm: 11.6 mJ*
*Average over 500 pulses. |
|
231
|
Thu Apr 14 19:46:46 2022 |
Sarper & Konstantin & Rodolfo | Laser | Laser power |
We checked the laser power before starting the new scan range.
- Seed energy before Cobra @ 532 nm: 513 mJ (before 499 mJ).
- New correction factor for Monitor: 71.25.
- UV output energy after SHG @ 320.1 nm: 11 mJ
All values are averaged over 500 laser pulses. |