MAPSOLENOID reference frame

[roblin]

I have a field map that was created for a set of solenoid coils (2 pairs of 3 coils of various radii) . This is a high homogeneity set of coils for a polarized target. I have a R,Z, Br,Bz map of the whole assembly.

I am using the MAPSOLENOID element. Now, how do I place that relative to the rest of the beam ?


I have to model the solenoidal system in two configurations.

1) the beam going along Z experiencing mostly the longitudinal solenoidal field.

2) the solenoid rotated 90 degrees (to produce a field along X and polarize the solid target in transverse)..

for 1), I used YAW=PITCH=TILT=0.0 (solenoid along z, parallel to floor) and enter with the beam at zero angle. This is a no-brainer, it works as expected.

for configuration 2),

My beam is going to arrive in the Z,Y plane with an angle. The idea is that the bending from the solenoid (which is opposite to the angle i come in) will result in a net zero angle at the exact center (to maximize resolution in the spectrometers detecting the scattered electrons).

Therefore, I set EYAW=1.57 and placed a kicker with VKICK=0.19 in front of the MAPSOLENOID. (0.19 is the expected bending from the solenoidal field now seen at 90 degrees, eventually, I will get ELEGANT to optimize it and find the exact one by tracking.).

I am not sure for 2), what the software does regarding the EYAW. Does it rotates relative to the center of the map or the start/end of the map element?

Yves

[michael_borland]

Yves,

The error tilts/yaw/pitch are imposed at the start of the element. Elegant transforms the beam coordinates in the opposite direction, under the
assumption of small angles. So your second simulation isn't going to give the expected results.

It isn't 100% straightforward to implement this in elegant because it involves a change of the reference trajectory. In the next release, their is (likely to be) a new, general-purpose field map integration facility. This will probably do what you need.

My suggestion for now is to use the SCRIPT element and an external program/script to implement this

--Michael