Create overview of instruments that need frame-unwrapping

[SimonHeybrock]

We need to unwrap frames of raw data from NeXus files. This requires some chopper information, which may be tricky to get right. It would be good to have an overview of which instruments actually suffer from neutrons crossing into the next frame. Basically, are there neutrons that have TOF > 70 ms? This depends on the total flight path and the maximum wavelength (slowest neutrons) that an instrument has.

Use something like this (please check for correctness):

import scipp as sc
from scippneutron.conversion.tof import wavelength_from_tof

Ltotal = sc.linspace("Ltotal", 10.0, 180.0, 100, unit="m")
da = sc.DataArray(
    wavelength_from_tof(tof=70 * sc.Unit("ms"), Ltotal=Ltotal),
    coords={"Ltotal": Ltotal},
)
da.plot(vmin=0, vmax=12, linestyle="solid", marker=None, grid=True)

• Go through all initial instruments, and get:
  • Their maximum Ltotal (source->sample->maximum-detector distance).
  • Their longest used wavelength.
• Make an overview, e.g., by adding points the a figure like the above.

[jokasimr]

Instruments in tranche 1

Needs frame unwrapping	Name	max $L_{total}$	max $\lambda$	Comment
Yes	Dream	$79$ m	$4.3$ A (standard setting)	Needs WFM according to dream WFM-stiching page on confluence. See draft of concepts of operations for dream, chapter 3.4 figure 2. Celine recommends looking at the dream instrument construction proposal on page 19. That's where the number $4.3$ A comes from. But it seems the instrument can also be used with non-standard settings to reach larger wavelengths (up to 20 A?).
Yes	Loki	$30$ m	$10.49$ A (mode 1) $19.5$ A (mode 2)	loki chopper simulation results (fig 4c) seem to imply that, at least in mode 2, the TOF will exceed the frame width 70ms. See also figure 3.6 (top) in the loki proposal that indicates the instrument will need frame unwrapping also in mode 1.
Yes	Odin	$64$ m	$10.2$ A	Needs WFM and pulse skipping according to odin-optics-paper and the odin concepts of operations paper, see chapter 3.4.5 and in particular figure 4.
Yes	Bifrost	$162$ m	See figure 4 and 5 in the bifrost Concepts Of Operations document. The figures and the long beam guide indicate frame unwrapping will be needed.
Yes	NMX	$>156$ m	$3.55$ A	According to NMX instrument construction proposal (section "Instrument and layout"). The distance from source to sample is $156$ m, and the distance to the detectors is larger. That places the TOF above $70$ ms.
Yes	Estia	$39$ m	$11$ A	See estia system design document section 4.3.

[jokasimr]

From the above table it seems all tranche 1 instruments will need frame unwrapping. Did I misunderstand the task? @SimonHeybrock

(Is it correct that wavelength frame multiplication implies need for frame unwrapping?)

[SimonHeybrock]

(Is it correct that wavelength frame multiplication implies need for frame unwrapping?)

No, I don't think so.

[SimonHeybrock]

From the above table it seems all tranche 1 instruments will need frame unwrapping. Did I misunderstand the task?

Can't tell, there are some missing numbers. I could be that all instruments need it.