  This paper presents the possibility of using very thin Low Gain Avalanche
Diodes (LGAD) ($25 - 50\mu$m thick) as tracking detector at future hadron
colliders, where particle fluence will be above $10^{16}\; n_{eq}/cm^2$. In the
present design, silicon sensors at the High-Luminosity LHC will be 100- 200
$\mu$m thick, generating, before irradiation, signals of 1-2 fC. This
contribution shows how very thin LGAD can provide signals of the same magnitude
via the interplay of gain in the gain layer and gain in the bulk up to fluences
above $10^{16}\; n_{eq}/cm^2$: up to fluences of 0.1-0.3$\cdot 10^{16}\;
n_{eq}/cm^2$, thin LGADs maintain a gain of $\sim$ 5-10 while at higher
fluences the increased bias voltage will trigger the onset of multiplication in
the bulk, providing the same gain as previously obtained in the gain layer. Key
to this idea is the possibility of a reliable, high-density LGAD design able to
hold large bias voltages ($\sim$ 500V).
