Speaker: Kyosuke Adachi
Abstract: The purpose of this study is a design and development of proof-of-principle model for the Vertical FFA. Currently, magnetic field measurement and beam dynamics study are being conducted to design a multi-coil type electromagnet. In this presentation, the current status of beam dynamics study with Opera3d and tracking simulation will be reported.
4 replies on “Study of beam dynamics of a vertical FFA with multi-coil type electromagnet”
It is an interesting machine design for sure. Well done. We want to understand it in detail.
Question is about orbit and optics. How do you obtain the trajectories on page 18: Do you use a 3D field map from the measurement or analytical field map? If it is analytical field map, how do they calculate the 3D field? Do you see the transverse tune is constant independent of energy?
Regarding RF cavity, does it have fixed frequency or it can sweep frequency? If latter, how much frequency modulation can be made?
Thank you for the comments.
The trajectories on page 18 were obtained by beam tracking using a 3D field map obtained from TOSCA.
The transverse tunes (4 eigen-values) look constant but are under examination in detail.
The frequency range of rf acceleration is 12-17MHz. Total number of turns is about 120 turns for the total rf voltage of about 200V.
I think the reason the starting point presented on slide 13 worked poorly was that the second picture on slide 8, which implies that the effect of a coil is fairly localized vertically, is not a very good one. This can be seen on slide 7: in the picture on the left, you can see that in fact the field is not very well localized. In addition, especially as you approach the top and bottom yokes, those yokes create distortions that cause the effect of the upper and lower coils to be different.
In fact, the iron does not so much function for field shaping in this magnet, but simply to reduce the magnetic reluctance. In that sense, the top and bottom return yokes are not particularly necessary. So you could cause the upper and lower coils to behave more like the central coils by simply removing the top and bottom return yokes, and extending the vertical yokes further up and down.
To handle the fact that the field is not very localized, you could instead construct a matrix relating the current in a coil to the field at a series of vertical positions. You can then solve the equations in a least squares sense to fine the currents, and this would also provide a rapid correction as you iterate.
Finally, as Shinji pointed out, I think that seeing how the tunes vary over your energy range is the real test of how well you were able to implement the scaling law.
Thank you for the comments.
Allow me to use that for reference in my research from now on.