deletions | additions       diff --git a/Nobeam_failures_are_.tex b/Nobeam_failures_are_.tex  index 430d7a4..4dd866f 100644  --- a/Nobeam_failures_are_.tex  +++ b/Nobeam_failures_are_.tex 
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``No-beam'' failures are defined to start when the beam current drops below a given limit.   For several facilities this is currently not the case. ALBA, BESSY-II and LSLS-UVX consider a  closure of the photon shutters by an interlock equivalent to a loss of the electron beam.  For some facilities a ``no-beam'' failure stops not when the beam is back to   the nominal current $I_{\hbox{nom}}$ but only  when the interlock is cleared that prevents the beamline shutters from opening   (ALBA, BESSY II, LNLS-UVX, SPring-8) or   when the insertion devices move back to their closed positions (SLS).   PETRA III adds an amount of time to allow for the warm-up of the optical components at the beamlines.   These practices are oriented to use a beam availability understood as photon beam availability.   Facilities are counting Here facilities count  the time the photon beam is ready to be used at the beamlines. ``Low-beam-current'' failuresdo  vary significantly between facilities. At Spring-8, for example, a beam decay of about 0.1\% starts a ``low-beam-current'' failure,   while at BESSY-II it starts only at 9\% beam decay.   The reason for this difference comes from the required current stability for the experiments  that can vary significantly between light sources. experiments.  LNLS-UVX and PETRA III do not account for ``low-beam-current'' failures at all (  $I_{\hbox{tol}}$ = $I_{\hbox{min}}$). 
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A ``downtime'' often only ends after the photon shutter or insertion device control is   given back to the users, which is not compatible with the ``no-beam'' rule.   This can be solved by having additional failure types for ``photon-shutter-closed'' or   ``insertion-devices-blocked-open'' while when  there is not a ``no-beam'' failure. The application of this new metrics metric  will disentangle failures of different nature. A former ``downtime'' at ALBA would then be the sum of ``no-beam'' and ``photon-shutter-closed'' failures.  It would allow a better comparison to facilities like the SLS, SLS  that do not have a global photon shutter interlock.  If several failures are recorded for a single incident,   then it should be recorded if a one  failure was preceded by another: if the photon-shutters are interlocked, the beam is then dumped and afterwards it takes five   minutes until the insertion-devices are unblocked, then it should be visible from the failure   data that these were not three but was rather  only one cause of  interruption in to  user operation. The authors decided agreed  to allow arbitrary limits for ``no-beam'' failures; in practice this does not make a large difference:   situations are rareat the evaluated facilities  where the stored  current drops from the nominal beam current to less than 50\% but not to zero.  ``Low-beam-current'' failures vary significantly with the definition of the $I_{\mbox{tol}}$ limit.  Nevertheless comparing the tolerated beam decay is still a  useful way  to judgethe promised  current stability of at  a facility. For those facilities where the limits are similar, the failure rateswill  allow a meaningful comparison of the reliability of the injection process.