[pstricks] how to output a eps file in right size?

[bear]

hi all,
    Pstricks is nice but I have a problem
    I dont want to run latex every time to generate a figure written with
pstricks
in my document, but to save it to a eps file. How to let its size fit well in
document?
Below is my pstricks. The problem is that it is a4paper in size and cannot too
large to embed in my document. can I save it just in the size of the figure
alone?

\documentclass[10pt,a4paper]{article}
\usepackage{multido,pstricks}
\def\particle#1#2{%
  \pscircle[fillstyle=solid,fillcolor=black](#1,#2){2pt} %particle
 
\pscircle[linestyle=dotted,dotsep=1.5pt,linewidth=0.5pt,linecolor=gray](#1,#2){6pt

}}
\psset{linewidth=2pt}
\begin{document}
  \begin{pspicture}(7,7)
    \psgrid[subgriddiv=0,griddots=10,gridlabels=0,gridcolor=lightgray](0,0)(6,6)
%grid
    \psline[linewidth=1.5pt]{-}(-1,6)(7,6) %boundary
    \psdots[dotscale=1,dotstyle=o,fillstyle=solid,fillcolor=red](3,6.5)  %photon
    \psline[linewidth=0.5pt]{->}(3,6.5)(3,5.5) %direction
    \multido{\ia=0+1}{7}{%
      \multido{\ib=0+1}{7}{\particle{\ia}{\ib}}}
  \end{pspicture}
  \hspace{30pt}%
  \begin{pspicture}(7,7)
    \psgrid[subgriddiv=0,griddots=10,gridlabels=0,gridcolor=lightgray](0,0)(6,6)
%grid
    \psline[linewidth=1.5pt]{-}(-1,6)(7,6) %boundary
    \psdots[dotscale=1,dotstyle=o,fillstyle=solid,fillcolor=red](3,6.5)  %photon
    \psline[linewidth=0.5pt]{->}(3,6.5)(3,5.5) %direction
    \input{rs.data}
  \end{pspicture}
\end{document}