How to reduce the input port reflection (O1,1) for a twt in CST

Hello,

I'm quite new to the subject of these tubes. I've made some basic models but when it gets to the point of creating a port I see that reflections from the input port seem excess to me.
For example an incident amplitude of 1 in port signals view has a value of 0.4 for O1,1 which I guess is pretty much.
I've tried changing port sizes, of course this makes differences but not much. I want to learn how to minimize these reflections, any help will be appreciated deeply.

PS: I can send a basic model as example.

hi,
what is the S11 number you are getting?

I can send the project file if you like. It'll be better for you to analyze. I've kept the number of turns small as they don't affect the reflections as far as I've observed, and simulations take less time. I've written what the parameters change in the description, only the phase parameter is unnecessary (it's there because I've started the project as slow wave structure).
Please let me know if you come up with something.
Thanks for you interest!

PS: Number of pulses is set to 20, the default value. Whatever I do the steady state condition is not met but again, it seems nothing to do with reflections.

Today I was working on the optimizer section. I've used the VSWR values (ordinate) with "<" operator as target for my specified frequency values (abscissa). It seems to work as the reflections are getting lower. This is the first time I'm using the optimizer, hopefully I'm doing it right. I just wanted to share this new information so anyone with similar problems could benefit from it.
Any help/suggestion is appreciated.