SANS Xpress

Small-angle scattering measure-by-courier service using the LOQ and SANS2D instruments.

Purpose

SANS Xpress Access at ISIS is suitable for:

  • new and infrequent users who want to test the feasibility of a potential SANS experiment prior to submitting a full proposal
  • existing users that need to probe their results or systems further because they are not yet sufficiently well-understood, or well-developed, to warrant a proposal in their own right
  • existing users that have a ‘desperate need’ to make a small number of additional measurements on samples related to their recent beam time proposals (eg, to complete a parametric data set, or ‘round-off’ a PhD thesis)
  • the facilitation of ‘blue sky’ and/or ‘in-house’ research
  • commercial users only requiring small durations of beam time and who are willing to accept ISIS involvement in the running of their samples – billing for this service is on a per hour basis.

But, please note, SANS Xpress Access is not intended to provide data of high statistical precision.

Principles

At least 1 day per cycle on the LOQ instrument will be devoted to Xpress Access, depending on demand. It may also be possible to run small numbers of Xpress Access samples as the instrument schedule permits.

Due to its high over-subscription, Xpress Access samples will only be run on the SANS2D instrument when there is a clear and justifiable case for doing so.

No guarantee is given that measurements will take place on any particular day, even if advertised, and normal peer-reviewed experiments will usually take priority. When Xpress Access samples cannot be run as advertised they will be held over – subject to their useful lifetime – until a new measurement session can be scheduled, or will be returned to the user if so requested.

Above all, it is expected that Xpress Access samples will be straightforward and uncomplicated, and easily run on a sample changer.

Experimental criteria

We prefer to use an incident neutron beam collimated to 8 mm in diameter so as to maximise the number of Xpress Access samples that can be mounted on the sample changers in one session. Solution/ dispersion samples should therefore be contained in 10 mm wide rectangular cuvettes of 1 mm or 2 mm path-length.

The duration that each Xpress Access sample is measured for will be at the discretion of the instrument scientists on the day.

Measurements will normally be performed at 25°C (298 K). However, applicants may discuss other measurement temperatures in the range 5-95°C (ie, those possible with the normal circulator baths used on LOQ/SANS2D) with us. Temperature variation work will only be performed after all ambient temperature measurements are completed (to remove the possibility of thermally-induced damage to other samples), and only if time permits.

Do remember that you must treat, for example, a background solvent as an Xpress Access sample in its own right; i.e. if your sample is a surfactant in an electrolyte solution you must not only supply that sample, but also the pure electrolyte solution!!!

Sample containers & shipping

Solution/dispersion samples should be contained in 10 mm wide rectangular cuvettes of 1 mm or 2 mm path-length. Some powders can also be contained in cuvettes.

Solid samples and granular materials should be contained in aluminium foil 'envelopes'. Leave small 'wings' of foil (5 mm is plenty) on either side of the 'envelope' for mounting purposes.

Xpress Access samples may be sent by whatever route is appropriate to the hazard that they present, but is the legal responsibility of the sender to ensure that they comply with all necessary packaging and transport regulations.

Where ISIS supplies transport packaging it should normally be used for sample shipment.

Measurements

At the start of each Xpress Access session the Instrument Team will, as a matter of routine, measure:

  • the scattering from an intensity calibration standard;
  • the background scattering for the intensity calibration standard;
  • the transmission of each of the above;
  • a 'direct beam' transmission

They will then measure the scattering and the transmission of each Xpress Access sample.

Data output

New and commercial applicants will be provided with fully reduced and corrected (ie, instrument-independent) data. More experienced applicants may simply be provided with details of the relevant files and expected to perform their own data reduction.

No analysis or interpretation of the data will be provided for any users, except where this is part of a separate collaboration or contract.

Beamtime limits

SANS Xpress Access must not be viewed as a way to circumvent the normal peer-review process associated with the Direct Access or Rapid Access mechanisms. For this reason, the Instrument Team reserve the right to cap excessive usage(*) and report those applicants to the relevant Facility Access Panel (FAP3). FAP3 may, in turn, require a Direct Access or Rapid Access proposal before further beam time is allocated.

(*) As a rough guide, more than 4 Xpress Access samples a cycle, or 12 Xpress Access samples a year.

Data policy

Data collected using SANS Xpress Access are subject to the normal ISIS policy regarding publication of scientific results, and bibliometric criteria, among others, will be used to assess the productivity of the scheme.


Online proposals: Apply for beamtime here
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