in order to avoid any laser induced damages on the EIB, we installed a fully hardware (analog) protection.

If the EIB_SAS control goes away for any reason, the DC value on an external quadrant photodiode (IBJM) is used as trigger to unlock the PMC.

The IBJM_DC value is about 2 Volts if the bench position is into +/- 100urad range.

If the DC value of the IBJM is below 0.1V (beam out) +5V is sent on the PMC perturb (PMC error signal offset) and 0V if IBJM_DC is more than 0.8V.

The PMC become unable to relock and start to scan, the peak power transmited by the PMC is still the maximum power
but with a really low duty cycle (mean power <1W).

If the bench back in the rigth position or if the unlock was due to the PMC unlock itself, the system is fast enough to recover the null tension on the PMC perturb allowing the relock of the system.

No changes has been observed on the PMC lock behavior in standard conditions.

The attached plot shows a short time when the beam was handly block / unblock in front of IBJM.

Note : The IBJM_DC monitor value has to be multiply by -2.