[Nexus-developers] Some more definitions

[freddie.akeroyd at stfc.ac.uk]

Hi Mark,


> -- I am missing something important: IMHO each TOF instrument has a
> pulse defining chopper. This is the
>    chopper, which sends the signal to start counting time-of-flight.
> There may be tons more choppers but they
>    are only there to have the neutron packet  win the Miss Neutron
> Pulse
> Beauty competition.  From what I know,
>    the distance of the pulse defining chopper to the sample is very
> important in order to calculate the total flight
>    length of the neutron for DA.  Now, no chopper was in the tofraw on
> the wiki.  I think I have to add this.  Any
>   opinions?

We have TOF instruments with no choppers at ISIS, the SXD instrument
being an example - they get their timing signal from the synchrotron
extraction pulse. Thus a chopper should be optional in TOFRAW. A chopper
will, however, always be present on a TOF instrument at a reactor
source.

Regards,

Freddie



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