/* solve ring-beam problem
/* r'' = 2IQ/(m.gamma.c.r)*(1-beta)

"fma_ra.rpn/s" @

0 sto tlim sto dt sto x sto x' sto t sto dt 
100 sto I       
I 3e9 * sto I cle
9.11e-28 sto me
4.8e-10 sto qe 
1 3e9 * 1e-13 * sto Q
Q qe / me * sto M
3e8 sto c
.2 sto x
1.187 sto gamma sqr rec 1 - chs sto beta 
2 I * Q * M / gamma / c / 1 beta - * sto const
90e-12 sto tlim
1e-12 sto dt
cle

udf
fn
swap pop rec const * 

udf
end
pop tlim - chs abs dt 100 / < 

udf
go
solve
t 1 "t = %le\n" fprf
x 1 "x = %le\n" fprf
x' 1 "x' = %le\n" fprf
3 popn
cle