CEA Codes forum

Dear All,

In the example "RFQ_1" (see the figure "Examples") provide by Tracewin, the longitudinal Norm_rms_emittance blow ups at the end of the lattice (See figure "Norm_rms_..")
Is that correct?

Dear Bruce,

Happy new year.
By default Toutatis excludes from rms emittance calculations the particles that are detached and far from the core of the beam.
This is not the case in TraceWin, so at the end of the RFQ when you arrive in the DRIFT elements these particles are again included in the emittance calculations and so the longitudinal emittance becomes huge. You have to exclude them also in TraceWin as shown in the attached picture.
Regards,

Didier

Dear Didier,

Happy new year, Thanks you very much for your help.

If you allowed me to ask more things. This is related to crosschecked with RFQGen codes. I am wondering if you know it.

1) The transverse curvature(TC) in TraceWin, is the Rho coeficient in RFQGen codes?
2) The cell types 3 (front-end cell) and 4 (transcell) to simulate the radial matching part, that in general are more than 4 cells, if use
more than two cell, one front-end cell and one transcell, all the particles are lost. Do you have any suggestion?

Thanks for the help,

Bruce

Dear Bruce,

the TC in Tracewin is the pole tip radius in mm. I am not familiar with RFQ Gen code and can not help you about the possible similarity.

Regarding the radial matching section, after called RMS, there is something specific here. Toutais does not consider the RMS to be made of several cells has there is no geometrical periodicity here but treats the RMS as one block. By the way , this block contains the gap. This block is then one single cell of type 3. The same for the fringe field seciton at the end. The trancell is actually the first cell of the periodic channel. Also it helps for dealing with the transition from no modulation to some modulation. To conclude, do not be confused with the concept of number cells in the RMS for a good matching that can be found in the litterature, a RMS has actually no repeating cell pattern.

If you want the RMS to be as long as N x Beta x Lambda then adjust the RFQ_Cell length paramater to N x Beta x Lambda with N being recommended to be greater or equal to 2.

I hope it helps,

Romuald

Dear Romuald,

Thanks you very much for your explanation. It is very useful.

About the TC parameter, the Rho is the vane-tip transverse radius of curvature in RFQ Gen. Thus, it is the same (Sorry for did not include the definition before).

Regard to the RMS, I can see for the example (RFQ_1 in TraceWin) that the equivalent cell length is about 6 x Beta_0 X lambda.

If you allow me with one more question. From the literature the Vane average radius Ro at the RMS decreased rapidly before enter to the Sharper Section. From the example in TraceWin, the Ro has the same value as the enter of the Sharper section. Could you tell me a little more about it?

Thanks again for your help and time,

Bruce

Hi

the R0 given is the value at the end of the RMS meaning where it connects to the channel. From z= 0 to z= RMS_length, the R0 evolves getting this increasing force. The profile follows the Crandall formulation used in Parmetq.

Best,

Romuald

Dear Romuald,

Thanks again for your explanation.

By that way, Is there an electronic version of your Ph. D thesis, which is cited in Toutatis reference?

Best regards,

Bruce

Dear Brucce,

Otherwise, it is also available for download on the website.

Regards,

Didier

Dear Didier,

Thank you very much for the document.

Best regards,

Bruce