deletions | additions       diff --git a/sectionPROPOSED_PRIM.tex b/sectionPROPOSED_PRIM.tex  index 1244ab6..e5405d9 100644  --- a/sectionPROPOSED_PRIM.tex  +++ b/sectionPROPOSED_PRIM.tex 
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\subsection{Primary Failure Modes in Practice}  ``No-beam'' events are defined to start when the beam current drops below a given limit. For  several facilities this is currently not 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 other facilities a ``no-beam'' event stops not when the beam is back to   the nominal current $I_{\hbox{nom}}$ but when the interlock flags that prevent  the beamline shutters from opening are cleared.   Others add 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 the time the photon beam is readily to be used at the beamlines.   In this sense the closure of the photon shutters for whatever reason has an  impact on the beam availability.   We propose to distinguish between a photon beam availability at the beamlines and an  electron beam available at the storage ring.   A ``no-beam'' event would only be defined by a loss of the electron beam current and a  ``photon-shutter-closed'' event would be recorded only if the photon shutters are forced   closed while there is not already a ``no-beam'' event.   The application of this new metrics will disentangle events of different nature.  The authors decided to allow arbitrary limits for ``no-beam'' events, to ease the application for different kind of facilities.  It does not make a large difference in practice: situations are rare at the evaluated facilities where the  current drops from the nominal beam current to less than 50\% but not to zero.   ``Low-beam-current'' events will vary significantly with the definitions of the $I_{\hbox{tol}}$ current limit.   At Spring-8, for example, a beam decay of about 0.1\% starts a ``low-beam-current'' event,   while at BESSY-II it starts only at 9\% beam decay.   The reason of this difference comes from the required current stability for the experiments  that can differ significantly between light sources.  The number and duration of ``low-beam-current'' events do tell how well a facility   meets their promised beam current stability.  Table~\ref{tab:pf-limits} shows the current limits for the primary  failure modes for the seven facilities.  The column $I_{\hbox{nom}}$ shows the maximum current in the given mode.  The current $I_{\hbox{inj}}$ is the typical value when injection would start in this mode,  below $I_{\hbox{tol}}$ it would be considered a ``low-beam-current'' event.   The column $I_{\hbox{min}}$ shows the condition under which a ``no-beam'' event would start.  Most facilities do not just have a current limit, but a combination of either  the current being below a limit or the photon shutters being closed.  \begin{table}  \centering  \caption{\label{tab:pf-limits} Primary failure mode limits} 
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\end{ruledtabular}  \end{table}  ``No-beam'' events are defined to start when the beam current drops below a given limit. For  several facilities this is currently not 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 other facilities a ``no-beam'' event stops not when the beam is back to   the nominal current $I_{\hbox{nom}}$ but when the interlock is cleared that prevents  the beamline shutters from opening.   Others add 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 the time the photon beam is readily to be used at the beamlines.   In this sense the closure of the photon shutters has an impact on the beam availability.   ``Low-beam-current'' events do vary significantly between facilities.   At Spring-8, for example, a beam decay of about 0.1\% starts a ``low-beam-current'' event,   while at BESSY-II it starts only at 9\% beam decay.   The reason of this difference comes from the required current stability for the experiments  that can differ significantly between light sources.  \subsection{Discussion of the Proposed Primary Failure Modes}  {\em ``No-beam''} events are defined to start when the beam current drops below a given limit.  For several facilities this is currently not the case.   Table~\ref{tab:pf-limits} shows that ALBA, BESSY II and LNLS-UVX do consider a closure of  the photon shutters by an interlock equivalent to a loss of the electron beam.   Other facilities, like the SLS do not have these kind of interlocks.  We propose that these events can be distinguished: a ``no-beam'' event would be only   defined by loss of beam current and a ``photon-shutter-closed'' event would be   recorded only if the photon shutters are forced close while there is not a ``no-beam'' event.  A similar situation applies to the end of a ``no-beam'' event.   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.   Again this This  can be solved by having additional event types for ``photon-shutter-closed'' or 'insertion-devices-blocked-open'' ``insertion-devices-blocked-open''  while there is not a ``no-beam'' event. This solution requires The application of this new metrics will disentangle events of different nature.  A former ``downtime'' at ALBA would  then be the sum of ``no-beam'' and ``photon-shutter-closed'' events.  It would allow a better comparison  to record facilities like the SLS,   that do no have a global photon shutter interlock.  If several events are recorded for a single incident,   then it should be recorded  if the event was preceded by another failure: 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 this was these were  not three rather but was  only oneindividual  interruption in user operation. The authors decided to allow arbitrary limits for ``no-beam'' events,   but in reality this does not make a large difference:   situations are rare at the evaluated facilities where the current drops from  the nominal beam current to less than 50\% but not to zero.   {\em ``Low-beam-current''} eventscan  vary significantly with the definition of the $I_{\mbox{tol}}$ limit.At SPring-8 already a beam decay of about 0.1\% causes a ``low-beam-current'' event, while at BESSY II up   to 9\% additional beam decay is still tolerated as insignificant for the users.  The comparison of the number and duration of ``low-beam-current'' events for BESSY II and   SPring-8 won't be useful therefore.  Nevertheless comparing the tolerated beam decay is still useful.  For those facilities where the limits are similar, the failure rates will allow a  meaningful comparison of the reliability of the injection process.    The authors decided to allow arbitrary limits for ``no-beam'' events, to ease the application for different kind of facilities.  It does not make a large difference in practice: situations are rare at the evaluated facilities where the  current drops from the nominal beam current to less than 50\% but not to zero.