Emittance growth at rfq end

[comunian]

Dear Didier,
I've observed a transverse emittance growth at the end of any rfq, also with RFQ_1.ini, in the last very short drift.

Emittance_growth.png (19.4 KiB) Viewed 1755 times

rfq_end_drift.PNG (47.96 KiB) Viewed 1755 times

A so short drift cannot induce a so large emittance increase.
May you know why ?
Best Regards,
Michele Comunian

[comunian]

Dear Didier,
reading the post,
I've removed from the emittance calculation the not accelerated particles.
The problem of transverse emittance growth is mitigate, but still present.
As you can see from the figures.

Emittance_growth_with_longitudinal_cut.png (21.66 KiB) Viewed 1748 times

Emittance_cut.PNG (7.8 KiB) Viewed 1748 times

Best Regards,
Michele Comunian

[Didier]

Dear Michele,

Actually, the growth you see is due to the Fringe field section including gap of the RFQ, the drift has nothing to do with it. The Toutatis save the emittances at the cell end position.

Regards,

Didier