set term pdf fontscale 0.5 size 3in,3in
outfile='spiral.pdf'
set output outfile
set timestamp offset graph 0.55,0.85 font ',8'
set label 'examples/example10/fixed_pitch/spiral.gnu' at graph 0.7,0.1 left font ',8' noenhance
unset border
unset xtics
unset ytics
unset ztics

set parametric
 set samples 100000
set xrange [-8.0:8.0]; set yrange [-8.0:8.0]
#set xlabel 'x'; set ylabel 'y'; set zlabel 'z'
radius=7.112
set arrow from 0,0,-1 to 0,0,20; set label 'B_z' at 0.5,0.5,18 
set arrow from radius,-1,6.3 to radius,1.5,6.7 lt -1 lw 2 size 7,2,60
splot [t=0:20] radius*cos(t), radius*sin(t), t not