-- JamesCrittenden - 18 Jan 2020

Tuning at the beginning of the shift

Open the strip tool files /home/erpopr/mlc/striptool_files/MLC_piezo_cntrl_vltg.stp and /home/erpopr/mlc/striptool_files/MLC_tuning_angle.stp

Open in EDM RF Operations/Cavity Tuners (MLC)

In RF Operations/MLC Operations put all six cavities in Kly Loop. Pay attention to 2k Heater, Pressure and blower speeds. When 6 cavities are in Kly Loop, set heater to 6 W.

This will need to be adjusted at more cavities are tuned and turned on.

With all cavities on, the heater should be at 0 W. Goal for blower speeds is 20-25%. Goal for pressure is 12.5 Torr.

Begin tuning cavities:

What is the value for the tuning angle?
  1. f zero, go to -5000 in Move Relative Command (MRC) in the Cavity Tuners EDM screen. (Do this only at the first tuning of the day.)
  2. f already -5000 (or something), enter a MRC of -100. Look for response in the tuning angle. If no response, increase the command to -200 (or more if needed) and watch. When the tuning angle approaches zero, take smaller steps to avoid overshoot. When near zero (Cavity 6 will still be fluctuating a lot around zero.), declare the cavity tuned, click OFF and ON to put the cavity in cavity loop.
  3. nd go to the next cavity. Adjust the heater as necessary.

Even-numbered cavities are stiffened. The tuners may not react at all to steps less than 20.

NB: After the cavities have been running for a while, do not make such large changes (+-5000) as at the beginning of the shift.

How to determine if retuning needed

Watch the piezo control voltages in the strip tool. If one of them is trending toward a limit, it will need retuning when it gets close to it.

Scales: Cavities 2,4,6: -16k to 16k. Cavities 1,3,5: 0 to 32k.

For example, Cavity 6 does this on a regular basis. The limit is 16384, as for all even-numbered (stiffened) cavities.  
When it reaches 14000, announce that it will need retuning within some period of time.

Go to kly_loop. Example of a step sequence for retuning cavity 6: 1000, 100, 50 10. Watch the tuning angle carefully with each step.
Use larger steps until it starts to respond. Also watch the field. Approach 1200 kV gradually. Cavity 6 is stiffened, so a step smaller than 100 will do nothing until one is close to target.

Cavity 1 can sometimes be retuned with small steps in cavity_loop.

January 19, 2020 MLC tuning diary
Cavity 6
Tuning angle started pegged at zero. Step of -5000 put it to -90 degrees. Responded to a step of -800.
Cavity 5
Started at -40 degrees. Used step of -20.
Cavity 4
Starts at -70. A step of -20 makes it go further negative. Used steps of -100 until it turned around.
Cavity 3
Started at +10 degrees. Goes up with a step of +20. Several steps of 200 and a step of 400 turn it around.
Cavity 2
Started at -90. Step of -20 make it go further negative. Used steps of -400 to get it to turn around.
Cavity 1
Started at -75 degrees. Overshot several times on purpose, with decreasing overshoots.
This procedure was done on this day with the intention of avoiding the recent experience of
occasional forward power spikes.

Later, Cavity 6 needed retuning.
Started pegged at +80. Reacted to several steps of +500.
Overshot with a step of +80. Recovered with a step of +40.

Some notes
If striptool plots look wrong, click Autoscale.
Clicking on the box containing the value being plotted will set the Y axis to the units and range for that quantitity.
Choose which variable is on top by unchoosing and choosing it in the control window.

Topic revision: r3 - 20 Jan 2020, JamesCrittenden
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