\begin{table}%t3
%\centering
\par
 \caption {\label{t:Rescale_Vinitial}Calculations of particle kinetic energies (in \rm{keV}) under different $V_{\rm initial}$
 ($V_{i}$) conditions.}
  \begin{tabular}{llllll}
 \hline\hline
 \noalign{\smallskip}
 & Acc. time & Min $E_k$ & Aver $E_k$ & Max $E_k$\\
 \hline
 $V_i=200~\rm{eV}$\\ %& Acc. time & Min $E_k$ & Aver $E_k$ & Max $E_k$\\
 $10^3$  protons & 0.1 \rm{s} & 7.43 & 19.21  & 30.02 \\
 $10^3$ electrons & 0.006 \rm{s} & 0.198 & 0.258 & 0.323 \\
 $V_i=2~\rm{keV}$ \\ %& Acc. time & Min $E_k$ & Aver $E_k$ & Max $E_k$\\
 $10^3$  protons & 0.056 \rm{s} & 1.26 & 19.85 & 44.24 \\
 $10^3$ electrons & 0.0024 \rm{s} & 1.99 & 2.17 & 2.36\\
 $V_i=10~\rm{keV}$ \\ %& Acc. time & Min $E_k$ & Aver $E_k$ & Max $E_k$\\
 $10^3$  protons & 0.032 \rm{s} & 8.49 & 27.66 & 63.37 \\
 $10^3$ electrons & 0.001 \rm{s} & 9.89 & 10.28 & 10.68 \\
 \hline
 \end{tabular}
 \end{table}