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Applying for Beam Time

Submitting Proposals
Proposals are submitted online through ( http://www.ncnr.nist.gov/howprop.html) and is generally related to the current call for proposals ( http://www.ncnr.nist.gov/call/current_call.html). Although this process is a formal refereed process that amounts to 25 % of the total beam-time available, unrefereed beam-time requests ( http://www.ncnr.nist.gov/requests.html) may be submitted at any time and must also be submitted using this form. An additional 38 % of the available beam-time is also available through this unrefereed mechanism.

Additional Instructions for Your Proposal
Currently we are asking for beam time requests to be submitted with a paper describing the following:
  1. General overview of the experiment.
    1. Should include an explanation of what the problem you wish to address is and how you expect neutrons to help?
    2. Drawings representative of the proposed idea of the experiment?
    3. Size and electrical requirements of the equipment you will bring.
    4. If available, references to already published literature on the subject?
  2. What equipment do you want us to provide?
  3. What spatial resolution do you need for the experiment?
  4. How much time do you wish to have?
    1. How many days (2 to 5 days are common requests)?
    2. What is your preferred time (dates)?
    3. Do you prefer weekends to weekdays or does this not matter to you?
  5. What potential safety hazards are there associated with the experiment?
    • This is a crucial point to consider since we will not be allowed to run an experiment if it doesn't fall inside the umbrella of currently reviewed experiments (i.e., the safety committee usually needs at least 4 weeks notice using a formal written proposal if it is very unusual).
The facility currently has the capability of running at 30 fps @ 0.254 mm spatial resolution with a 20 cm  25 cm field of view. If the detector is run at or less than 7.5 fps then the detector bin size is 0.127 mm. The beam is 25 cm in diameter with the beam characteristics described in Table 1.

Table 1. General beam characteristics are described here. The last column shows the values for no filter for the sake of comparison to other neutron radiography facilities (we are not currently able to run in this configuration).

L
(m)
Aperture
d
(cm)
L/d
Beam
diameter
(cm)
15 cm bismuth filter
Fluence Rate
(cm-2 s-1)
No filter
Fluence Rate
(cm-2 s-1)
2 2    100 8 5.1 107 3.0 108
3 2    150 13 3.4 107 2.0 108
4 2    200 17 2.5 107 1.5 108
6 2    300 26 1.7 107 1.0 108
6 1.5  400 26 1.0 107 5.9 107
6 1.0  600 26 4.3 106 2.5 107
6 0.5 1200 26 1.0 106 5.9 106
6 0.1  6000  26 4.3 104 2.5 105

Here L is the distance from aperture to sample, and d is the aperture diameter. Note that the highest fluence rates have a smaller beam diameter. The current detector will reach saturation when the beam fluence rate is about 108 cm-2 s-1. That will not occur with the parameters we have here. The more the intensity is the better the signal will be so you must balance the resolution you need with the fluence rate. The larger the fluence rate is, the lower the beam resolution will be. There will be a minimum of 5 cm separation between the object you are radiographing and the imaging plane of the detector. This distance is likely to be the ultimate factor in determining the spatial resolution if the L/d ratio is less than 600.

If you are running at 30 fps the data rate is about 40 megabytes (MB) per second. In one hour you can expect to take 160 gigabytes of data. We handle this here using a RAID 0 drive to take the data and then back it up afterward to external hard drives. The standard hard drive can take about 10 MB per second of bandwidth. If you use a RAID 0 system with 4 hard drives you can achieve a 40 MB per second rate. I do not recommend using RAID 0 for backup since a failure of one drive will wipe out all your data and will not be recoverable. Other RAID numbers (1,...,5,...) have more reliability factor built in, but will never give the bandwidth performance of the RAID 0 system. In any case you should prepare for the amount of data you will capture so you can take it home and analyze it. We use IDL (from Research Systems Inc.) to analyze data. Our software is available to you and we can show you how to use it. To use the source code you will need to have a full version of IDL. One can also use software like Matlab, but we do not have any software analysis tools written for Matlab at this time.

Reactor Access

The following steps are required to be followed for accessing the facility here at NIST.

Be sure to follow the following instructions for access to NIST ( http://www.ncnr.nist.gov/experiments.html) and sign up online for access and the tour and training by health physics. If you do not then they will not be able to schedule you in that morning.

To walk through the steps necessary, each person should visit this website and follow these steps:

  • Select "First Time User"
  • Carefully follow through all of the steps on this page.
  • Be sure to have a "Trustworthy memo" (follow this online template verbatim http://www.ncnr.nist.gov/trustworthy.html) written on institution letterhead and signed by a supervisor. You will provide this to the reactor facility on the day you arrive. This is a standard requirement that everybody is required to do.

You will want to download ( http://www.ncnr.nist.gov/visitor/training.html) and go over the health and safety training program on your computer at your home institution prior to coming to NIST. When you get here then you can take the official quiz. This training usually takes 4 or 5 hours, but if you do it beforehand while you are at your home institution then you only need about 30 minutes the first day to take the quiz. That way you optimize your time here at the lab.

Once you have taken the exam you will not need to take it again for 2 years. However, you will be required to undergo safety training for using the beam line that I will conduct.


Inquiries or comments: David Jacobson

Online: May 2006   -   Last update: November 2006