High Flux Backscattering Spectrometer

HFBS: Planning your measurement

If you have an idea for a measurement, and want to discuss feasibility and other practical matters, please contact one of the instrument scientists. If this is the first time you will be doing an experiment on HFBS, we strongly encourage you to discuss your plans with one of the local contacts.

Applying for beamtime (submitting requests and proposals)

To obtain beamtime on the HFBS, you must submit either a request or a proposal, both of which can be accessed by clicking here

Access to the NCNR

Purpose of Visit	To get access, you MUST apply each time	Deadlines
First Time Facility User	Click here for detailed instructions.	35 calendar days before arrival is required unless you are a U.S. citizen or permanent resident (with a green card), in which case a minimum of two business days is needed.
Returning Facility User	Click here to log in to your NCNR IMS account and request a visit.	Two business days in advance is needed.
Non-User Visit (examples: tour, talk, seminar, etc.)	Click here to access our visitor registration page and fill out the request form.	Two business days in advance is needed.
All other requests	Contact our User Office at ncnraccess@nist.gov or (301) 975-8200.

Rough estimate of the time required for measurements

The following information is presented so that prospective users can get an idea how long their measurement may take.

A vanadium sample in the form of a hollow cylinder, a 10% scatterer, was measured with a dynamic range of +/-27 µeV for 100 minutes. The sample, which was mounted onto the closed cycle refrigerator but measured at room temperature, was completely illuminated by the neutron beam. Note that the beam size is 30 mm x 30 mm square. The average total count rate in a detector was 108 counts/minute and the signal to background ratio was 400:1. At the end of the 100 minute count time, the intensity at the peak maximum was about 333 counts per detector or about 5.5% relative error.

It is important to note that a larger dynamic range will result in a proportionately longer measuring time (to achieve the same counting statistics, same energy bin size). For instance, you would have to measure about 33% longer at the +/-36 µeV dynamic range to get the same statistics as in the measurement discussed above.