SPACE_CHARGE_COMP and field_map

[Changqiang_ciae]

We were tried to use Tracewin code to simulate the beam transmission in a separator magnet, the bending angle of the magnet is 180°，and the radius is 1000 mm，because of the magnetic field is inhomogeneous, we used the calculated 3D magnetic field instead of the hard-edge model in Tracewin, when the space charge effect is neglected(setting SPACE_CHARGE_COMP as 1.0), the simulated results seems are right, but when the space charge effect is considered, the results always are same as setting the SPACE_CHARGE_COMP is 1.0, it seems that there are no space charge effect in the FIELD_MAP area. Figure 1 is the beam spot when setting the SPACE_CHARGE_COMP as 1.0, and figure 2 is the beam spot when setting the SPACE_CHARGE_COMP as 0.1, the slightly different is caused by a drift distance(the space charge effect is considered in the DRFIT command, while not in the FIELD_MAP command in our simulation). The beam energy is 40 keV and current is 10 mA.

Figure 1 SPACE_CHARGE_COMP 1.0

Figure 2 SPACE_CHARGE_COMP 0.1
Here is our test command(only including the separator magnet part):
SPACE_CHARGE_COMP 1.0
DRIFT 0.01 300 200 00
SUPERPOSE_MAP_OUT 0 2000 0 0 0 180
SUPERPOSE_MAP 50 0 0 0 0 0
FIELD_MAP 0070 1850 0 240 -0.288019 0 0 0 dipoleh
DRIFT 5 300 200 00
The second question is that which kind of space charge routines we should select if the beam is ribbon shape, 2D or 3D? What is the difference between the two models?
We would appreciate a lot for your help!
Beast Regards!

[Didier]

Dear Changqiang_ciae,

That's exactly right, in tracking mode, when you use field maps that curve the central trajectory the space charge is not calculated. This is a much more complex development than the usual space charge in rectiligne frame and it has not yet been carried out and implemented. Probably in futur, bu I don't know when.
Please note that this is indicated in the manual in red.
Note also, that it is also possible in TraceWin to implement its own space charge routine and to use it.

Best Regards,

Didier