AMPLITUDE Magma 200 Manual

CFEL –Magma 200
Amplitude Laser
Start-up procedure

[ p.2 ] Start-up procedure / September 2019
I. General Warning
Golden rule: Pump first, seed second!
There is serious danger to the laser system if the full power of the previous amplifier is seeded into
the next one wihtout the amplifier diode been on. The crystal is convergent without the pump on so it
will focus the high energy pulses.
The reverse is true for the shunt down procedure. First shut down the seed then turn down the
diodes.
Figure 1: Key Rack which allows remote control of the several shutters and diodes of the laser system
The shutter keys of MP1 and MP2 should be turned off before starting the warm-up procedure.

[ p.3 ] Start-up procedure / September 2019
II. Laser composition
Figure 2: Laser installation in the CFEL laboratory
The laser system Magma 200 is composed of:
4 laser-head units on the optical tables:
•Magma 25
•MP1
•MP2
•Compressor
Several electronics units:
•One rack oscillator situated near the regenerative amplifier
•One pulseshaper rack unit that control the shape of the laser spectrum also situated near the
regenerative amplifier
•Several PCs (1 host with direct control and 2 remote-controlled in rack, see the Control
Command manual)
•Four racked diode control units (1 for the regenerative amplifier and the MP1 and 2 for the
main amplifier)
•One HV unit to control the regenerative amplifier pockels cell

[ p.4 ] Start-up procedure / September 2019
•Two diagnostics control racks (one for each multipass amplifier –MP1 and MP2) which
control the shutter, check the temperature of the laser system and control the motorized
mount of each system.
Cooling devices:
•One deionized chiller for the regenerative and MP 1 amplifier
•Three standard chillers to cooled down each amplifier crystal
•One chiller to cooled down the two MP2 amplifier diodes
III. Preliminary start-up:
12 hours before the used of the laser system all the chiller and deionization module should be
started on (DI value should be above 0.5 MOhm.cm and the alarm of the control will switch off by
itself).
Figure 3: on the left a chiller, on the right deionization control unit

[ p.5 ] Start-up procedure / September 2019
IV. Laser sart-up
The Shutter of MP1 and MP2 should be turned off before starting the warm-up procedure.
IV. 1. Synchronization
Log into the host PC located near the regenerative amplifier. Start the control program ElliOOs,
login Amplitude and no password (see the manual of the Control Command: CCM for more
information) and select the sub-menu Instruments/ Selectpulse.
Figure 4: General interface of the ElliOOs software which allow control of the different laser part
On the first menu of the selectpulse interface, one should see the several synchronization channel
the channel “front-end”, “diodes regen-MP1”, “Diodes MP2”, “Camera MP1”, “Camera Regen”, and
“Camera Compressor” are ON. They should be lit green as can be seen of the next picture.

[ p.6 ] Start-up procedure / September 2019
Figure 5 : First menu of the SelectPulse interface
IV. 2. Regulation Stabilizer
Go into the menu Regulation of the CCM and checked that each regulation is turn OFF and
connected to the right camera.
Figure 6: Regulation interface –Regulation menu

[ p.7 ] Start-up procedure / September 2019
On the sub-menu settings of the regulation interface one can see the camera selection for the
regulation. For the regen beam stabilization the NF Regen should be selected, for the MP1 => NF MP1,
for MP2 => NF MP2.
Figure 7 : Regulation interface –Settings menu
IV. 3. Pump diodes
Once the chillers and deionization module are on and the flow meter are lightning the flow
measured in green. Then turn on the control unit of all the diode on the rear panel. Turn ON the HV
power supply.
Figure 8: Front of the diode control unit
Select the sub-menu diode of the regenerative amplifier.

[ p.8 ] Start-up procedure / September 2019
Figure 9 : Diode control interface (regenerative amplifier)
First check that the current is sent to 0 %, then slide the power supply and output to the green
position as can be seen on the picture above. Then slowly increase the set current (10 % step) to the
standby value of 50 %.
The same process needs to be repeated for three other diodes: diode MP1, diode MP2 (1) and
diode MP2 (2). If you are preparing the laser for operation the next day (recommended if possible), set
the value to standby mode, if it is for operation as soon as possible, set the values to operation mode
(2-3 hours warm up).
Standby mode: all diodes at 50 %
Operation mode: Regen diode at 53 %, diode MP1 at 95 %, both MP2 diodes at 80 %. Wait for
thermalization => it will be best to wait at least two hours before continuing the start-up procedure.

[ p.9 ] Start-up procedure / September 2019
IV. 4. Regenerative amplifier
First the oscillator control unit (see bellow) needs to be turned on. Check that the rear panel is ON,
in standby mode the laser button should be red then turn the laser key to “laser ON”.
Figure 10 : Front panel of the front-end
Log into the Lasers –Magma25 menu of the CCM the Laser diode and Shutter should be slid ON.
Check that the pulse picker is activated and that the delays are set on the Magma 25 module (see
pictures below).
Figure 11: Magma 25 (regenerative amplifier) control software –Main sub-menu

[ p.10 ] Start-up procedure / September 2019
Figure 12 : Magma 25 (regenerative amplifier) control software –Synchro sub-menu
Open the Regen shutter and check that the seed going into MP1 is minimized (use IR card) and the
shutter of MP1 is OFF.
Now return to the diode interface and slowly ramp up the pumps
Set the regenerative amplifier pump to 53 % in slow steps of 1 % (to have ~8.2 mJ displayed in
camera energy-tab) while monitoring the beam profile with the cameras. Check that there is a proper
beam on NF and FF camera and that the profile seems coherent with previous laser use.

[ p.11 ] Start-up procedure / September 2019
IV. 5. Diodes ramp-up to nominal value and regenerative amplifier final
amplification
Go into the respective interface and slowly (by 10 % increased) ramp up the diode power of MP1
and MP2. The nominal value for MP1 diode is 95 %, while the nominal value for MP2 diode is 80 %.
Go in to the regen stabilizer software and turn on the Regen beam stabilizer (stabilization tab) and
turn on recording of the beam position (camera tab).
Figure 13 : Regulation interface –Regulation sub-menu
Go back to the NF camera menu and check the beam profile and pointing. Increase the pump of
the regen to 58 % in steps of 1 %. Check the energy unto the camera ”energy” sub menu, it should be
to be around 32 mJ. The energy value recording can be started.

[ p.12 ] Start-up procedure / September 2019
Figure 14: NF Regen camera interface –energy sub-menu
Before further amplification can be made the regenerative amplifier’s spectrum needs to be
checked. Typically, 15 min warm-up of the regenerative amplifier at full energy is needed for the
regenerative amplifier spectrum to be at his nominal value, see picture bellow.
A spectrometer has been set-up to look at the leak of the first mirror after the regenerative
amplifier. The supply spectrometer is an Avantes spectrometer the Avasoft software can be used on
any Windows PC to measure the spectrum of the regenerative amplifier. A reference spectrum is saved
on the host PC in the folder home/document/DATA_FOR_CFEL (see “how to check regen spectrum”
for more information, beware the calibration file of the spectrometer is needed to get the correct
measurement).

[ p.13 ] Start-up procedure / September 2019
Figure 15 : Red: reference spectrum of the regen after thermalization (~15min). Black: Regen spectrum at full power before
thermalizing.
IV. 6. First Multipass amplifier –MP1
First check that no energy is seeded into MP1 and that the laser diode is still ON.
Figure 16: Regen to MP1 turning mirror and attenuation. At the top of the picture one can see the NF and FF camera of the
regenerative amplifier
1st
turning mirror
Regen to MP1
Attenuation
NF and FF regen
camera

[ p.14 ] Start-up procedure / September 2019
Open the shutter of the MP1 amplifier
Figure 17 : Key Rack –MP1 shutter key
Gradually turn the half-wave plate (at the center of Figure 16) to increase the energy inside the
MP1 amplifier until the camera after MP1 detects the beam. If the beam profile of MP1 looks correct
(as seen on Figure 18) at low energy, turn the wave-plate until the camera displays the lineout profiles
of the beam, which means the MP1 regulation can be activated as the centroid of the beam is
calculated.
Figure 18: NF MP1 with low energy output out of MP1. The software does not calculate the centroid yet as the lineout profile
are not traced on the image.

[ p.15 ] Start-up procedure / September 2019
Switch on the beam stabilization as soon as the lineout profiles are displayed.
Figure 19: MP1 regulation interface –Regulation sub-menu
Wait until the beam is centered on the camera indicated by red crosshair on the NF MP1 camera
menu or wait for the regulation of MP1 to switch to “Aligned”.
Check that no energy is seeded in MP2 and proceed to send the whole regen energy in MP1 by
turning the previously mentioned waveplate (while checking the beam profile on the near field MP1
camera) to reach 85 mJ output.

[ p.16 ] Start-up procedure / September 2019
IV. 6. Second Multipass amplifier –MP2
Make sure the input of the compressor is blocked and open MP2 shutter..
Figure 20: Key Rack –MP2 shutter key
Open the camera for MP2 and start to send a small portion of energy into MP2 until the camera
display shows the line-profiles of the beam on the sides of the screen, see Figure 22. The halfwave
plate situated between MP1 and MP2 should be used to slowly increased the seed energy, see Figure
21.
Figure 21 : MP1 to MP2 attenuation
MP1 to MP2
Attenuation

[ p.17 ] Start-up procedure / September 2019
Figure 22: NF MP2 camera interface
If the beam profile resembles the standard one at low energy, turn on MP2 beam stabilizer. Wait
until the beam is centered on the camera indicated by red crosshair on the NF MP2 camera menu or
wait for the regulation of MP2 to switch to align mode.
Propagate the low energy beam through the compressor.
Check the beam via the NF compressor camera. If it looks correct, turn the compressor attenuation
(in the compressor rotation menu) to dump all the MP2 energy before going through the compressor.
Proceed to send the whole MP1 energy in MP2 (while checking the beam profile on the near field MP2
camera) to reach 230-240 mJ at the output of the amplifier. Finally turn the compressor attenuation
waveplate in order to reach up to 210 mJ at the compressor output.

[ p.18 ] Start-up procedure / September 2019
IV. 7. Safety Checks
During the use of the laser system a safety checks can be implemented so that if the laser system
would deviate too much from its “standard points” a security will alert and cut the seed of the laser
system.
The beam safety function is based on the beam profile, beam position and beam intensity.
First go through all the cameras and activate the beam-profile safety-checks in the ”Profiles and
Gabarits” menu of the camera modules
Figure 23: Profile and Gabarits menu of a camera module
Second, double-click the “Safety” icon on the main menu in order to open the interlock menu
(Figure 24). If the laser is aligned to its nominal points, all the interlocks should be green. If some are
red check the modules are faulty, if some are grey they are not activated. The interlock can be turned
on via clicking the “Nominal” tab as highlighted on Figure 25.

[ p.19 ] Start-up procedure / September 2019
Figure 24: Safety panel situated on the main interface of the CCM
Figure 25: Safety menu click into nominal for activation once the start-up procedure of the laser system is completed.

[ p.20 ] Start-up procedure / September 2019
V. Putting the system in stand-by mode:
For this system it is crucial to turn down the seed first and then the pumps!!!
The reason is that the thermal lenses of the crystals would cause the seed to be focused when the
pumps would be ramped down first. The focused seed then can damage the optics in the amplifiers.
Giant pulses are not a problem because the system is a low rep-rate system, it is designed to have
a very high gain per pulse
Turn off the interlock system checking the beamprofiles etc. Via clicking the ”manual” tab in the
safety check menu.
Turn off the beam pointing stabilizer of MP2.
Turn down the seed going into MP2 via the half-wave-plate before MP2. See picture of start-up
procedure showing the waveplate for this! Minimize the seed into MP2 using an IR card.
Turn off the beam pointing stabilizer of MP1.
Turn down the seed into MP1 via the half-wave-plate after the regen amplifier. Make sure the seed
going into MP1 is minimized using an IR card.
Turn off the beam pointing stabilizer of the regen amplifier
Ramp down the pump diodes:
MP2-diode 1: down to 50 % in steps of 10 %
MP2-diode 2: down to 50 % in steps of 10 %
MP1: down to 50 % in steps of 10 %
Regen: down to 50 % in steps of 1 %
Close the shutters for MP2, MP1 on the key rack units and close the regen shutter by pressing the
shutter button on the oscillator (the Front-end key shuts down the oscillator, which is not
recommended for day-to-day operation).Close the output port of the compressor to avoid dust
accumulation inside the module.
When restarting the laser the next day, follow the start-up procedure of section IV. where the first
steps are only needed to be checks and not performed as the laser is already in a thermalized state.