NXmx total_flux

[lucagelisio]

The quantity total_flux is currently defined as flux incident on beam plane in photons per second.
For pulsed light sources, like free electron lasers, the temporal profile of each pulse is rarely reliably known.
It would be therefore desirable and more accurate to express total_flux in photons.

Would it be possible to have either photons/second or photons as unit of measurement for total_flux?

[yayahjb]

total_flux was added to deal with the flux in photons/s/cm^2 summed over the beam area in cm^2, which is why it is in photons/s and it is not a good idea to change dimensionality by a change in units. For the case in which temporal profiles are not known, I would suggest we add a new suffix _integrated for the time integral of any existing tag and two new definitions: flux_integrated in photons/cm^2 and total_flux_integrated in photons for the time integrals of flux and total_flux respectively.

…

On Thu, Feb 24, 2022 at 7:23 PM Luca Gelisio ***@***.***> wrote: The quantity *total_flux* is currently defined as flux incident on beam plane in *photons per second*. For pulsed light sources, like free electron lasers, the temporal profile of each pulse is rarely reliably known. It would be therefore desirable and more accurate to express *total_flux* in photons. Would it be possible to have either photons/second or photons as unit of measurement for *total_flux*? — Reply to this email directly, view it on GitHub <#986>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABB6EAJXEZIZAGCUMLOTNHLU43DZPANCNFSM5PI3NRBQ> . Triage notifications on the go with GitHub Mobile for iOS <https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675> or Android <https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub>. You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[lucagelisio]

Thanks a lot Herbert, I like your proposal.
total_flux is a required entry, could this become recommended, or alternatively require this one or its integrated version?

[phyy-nx]

Discussion from NIAC telco today: what we need is a way to specify that the user must supply one of total_flux, flux_integrated, or total_flux_integrated. There doesn't seem to be an easy way to write that specification using NXDL, so it's recommended this issue be brought up in the next NIAC meeting in early March 2022.

[benajamin]

I think that it could be accomplished by requiring a "pointer" field be present whose value is the name of the flux measure being provided. An existing example is the signal attribute for NXdata.

[phyy-nx]

Feedback from Spring NIAC 2022: using an NXmonitor class may be better here. See NXstxm for example. (This comment is meant as a springboard for more discussion here).

[lucagelisio]

This sounds sensible to me!

[benajamin]

XML has a choice element that requires exactly one object from a set be present. It would need to be used in the NXDL schema to define a tag that you could then use in NXmx.