| 12 |
|
field = vfp.Field() |
| 13 |
|
# add the qpole |
| 14 |
|
# note, parameters are should be [ r_x, r_y, phi, q], where r is the position vector, phi is the angle of the quadrupole in radians, and q is the charge magnitude |
| 15 |
< |
field.add_element('quadrupoles' , [ [ 0, 0, 1.0, 100] ] ) |
| 15 |
> |
field.add_element('quadrupoles' , [ [ 0, 0, 0.0, 100] ] ) |
| 16 |
|
|
| 17 |
|
# draw the charges for the field on the document |
| 18 |
|
doc.draw_charges(field) |
| 19 |
|
|
| 20 |
|
# start drawing the field lines |
| 21 |
|
# we are going to draw 20 field lines comming off of the quadrupole at uniformly spaced angles. |
| 22 |
< |
N = 49 |
| 22 |
> |
N = 37 |
| 23 |
|
for i in range(N): |
| 24 |
|
# compute the angle that the line will start off at |
| 25 |
< |
angle = i * 2.*math.pi / (N-1) |
| 26 |
< |
# generate the line |
| 27 |
< |
# this takes the initial position, the x and y components of the initial direction, and whether or not should go forward |
| 28 |
< |
# or backward. |
| 29 |
< |
line = vfp.FieldLine( field, [0.1*math.cos(angle),0.1*math.sin(angle)], start_v=[math.cos( angle ) , math.sin( angle )],directions='forward' ) |
| 25 |
> |
angle = float(i) * 2.0* math.pi / float(N-1) |
| 26 |
> |
direction = 'forward' |
| 27 |
> |
|
| 28 |
> |
if (math.fabs(angle - 0.0) < 1.0e-3): |
| 29 |
> |
direction = 'backwards' |
| 30 |
> |
if (math.fabs(angle - math.pi) < 1.0e-3): |
| 31 |
> |
direction = 'backwards' |
| 32 |
> |
|
| 33 |
> |
print angle, direction |
| 34 |
> |
# generate the line this takes the initial position, the x and y |
| 35 |
> |
# components of the initial direction, and whether or not should |
| 36 |
> |
# go forward or backward. |
| 37 |
> |
line = vfp.FieldLine( field, [0.15*math.cos(angle),0.15*math.sin(angle)], start_v=[math.cos( angle ) , math.sin( angle )],directions=direction ) |
| 38 |
|
# draw the lin on the document |
| 39 |
< |
doc.draw_line(line,arrows_style={'min_arrows':1,'scale':0.4,'max_arrows':3}) |
| 39 |
> |
doc.draw_line(line,arrows_style={'min_arrows':1,'scale':0.5,'max_arrows':2}) |
| 40 |
|
|
| 41 |
|
# write the document |
| 42 |
|
doc.write() |
