CEA Codes forum

Hi,
is there a way to get the bunch center rf phase at the exit of the RFQ? I can not find the data in toutatis.out or anywhere else.
Background; I need to know the RF phase at the time, that the bunch leaves the RFQ at a specific point (end wall).
I could interpolate from the last known cell center phase, but this gets ab bit tricky with transition cells (with external .vane file), Also since toutatis is a t-code, there should be a way to get this information directly, right?

I am using an imported .vane file generated from parmteq vane data. As I understand, the phase in the cell block is only used to plot the separatrix. So how can I find the bunch phase?

I hope you have some suggestions.

Best regards,
Hendrik

Hi,

I am sorry for this late reply. We are actually working on this topic Didier and myself. There is some history there due to compatibility with TraceWin nomenclature and Toutatis specificities. I tell you how the P0 parameter is calculated in your version and what is about to be released soon as we have changed the way the beam phase is calculated.

In your version: the parameter P0 (6th column) in out file corresponds to the value P0 = (Zcenter- ZSync0 + ZG) * 2*Pi/(beta*lambda)

where Zcenter is the average z poosition of the particles, ZSync0 is z position of a reference particle transported since the beginning and this particle is first placed at the center of the bunch and then does not see any phase error nor space charge, and ZSync is similar to ZSync but does see phase error. Finally the parameter ZG = ZSync - ZSync0, thus if no phase error, ZG = 0. Also, if the bunch center behaves as the test particle, you get P0 = 0.

A the creation of Toutatis, we decided to transport a test particle to compare its phase to the phases of the other particles seeing the error, space charge and so on. Finally for many reason, we decided to use data in .inp file to build a reference particle. This has advantages and drawbacks that I could detail if you want me to. Anyhow, in the version that is about to be released:

P0 is now derived from the beam center beta evolution and the energy gain calculated via A, voltage and reference PhiS or reference beta in .inp if present. By doing so, if you reduce the voltage compared to nominal, you will see a phase slippage that provides the same beta evolution until the voltage is not too low (meaning no bunch anymore...).

It is important to notice that even if Toutatis is a T code, getting the phase at exit is not so straight forward as at RFQ entrance, the image effects changes the beta and Toutatis only simulates what happens on the downstream side of the plate. This makes that the real accel/deccel effect induced at entrance is not properly simulated. This artificially creates a phase evolution dependance on current for the beam center at entrance. And thus, we finally decided to build a more robust reference by looking at the evolution of the energy gain compared to nominal, cell after cell.

I hope I have not been too complicated. Anyhow, do not hesitate to sollicit me.

Best,

Romuald