Most Penetrating X ray, Boron

With Boron $B$,

$v_{boom}=3.4354*\cfrac{density}{Z}=3.4354*\cfrac{2340}{5}=1607.80\,ms^{-1}$

$S_{p\,B}=\cfrac{1607.8}{1061.42}*0.2=0.303\,m$

This is the most penetrating X ray using Boron $B$, at $30\,cm$.

$V_{min}=\cfrac{1}{2}\cfrac{M}{qN_A}\left(3.4354*\cfrac{density}{Z}\right)^2$

$V_{min}=\cfrac{1}{2}*\cfrac{10.806}{6.0221*10^{23}*1.6021*10^{-19}*10^{3}}*\left(3.4354*\cfrac{2340}{5}\right)^2$

$V_{min}=0.1445\,V$

For a length of $d=10\,cm$,

$v_{min}=\cfrac{0.1445}{0.1}=1.445\,V$

Compare this to copper $Cu$ of density $8960\,kgm^{-3}$,

$V_{min}=\cfrac{1}{2}*\cfrac{63.546}{6.0221*10^{23}*1.6021*10^{-19}*10^{3}}*\left(3.4354*\cfrac{8960}{29}\right)^2$

$V_{min}=0.3710\,V$

For a length of $d=10\,cm$,

$v_{min}=\cfrac{0.371}{0.1}=3.71\,V$

Boron requires less voltage.

Both $v_{min}$ are resonance value, only at exactly these values are X rays emitted.

The value of $V_{min}$ for copper however, does not compare with the post "X Ray, Inner Electron Cloud And Just As Shocking TWO" dated 15 Oct 2017, where,

$I_{res}=1.1974 A$

because the electric resistance of copper is very low at $16.78 nΩ·m$. 

Given a voltage of $3.71\,V$, the current need not be at $I_{res}=1.1974\,A$ unless the cross sectional area of the wire is at,

$V=3.71=1.1974*16.78*10^{-9}*\cfrac{0.1}{A_x}$

$A_x=1.1974*16.78*10^{-9}*\cfrac{0.1}{3.71}=5.41\text{e-10}\,m^2$

The electron cloud at resonance and colliding particles at $v_{boom}$ are different phenomenon.  It may not be correct to associate them.

Then again $v_{min}$ for a solid has never been verified.  How much free space is there, within a solid, to accommodate basic particles?

Good night.