[Fast-Neutrons] Congrats! Re: First fast neutron images at Phoenix

Mon Nov 18 10:43:23 CET 2019

Hello Michael, Burkhard and Eberhard.

Thank you Michael for these nice images. I too am impressed by the
resolution of your thermal images with an L/D of only 35, and agree that it
would be good to take thermal images with a camera rather than a neutron
image plate. The ordinary Fuji n-plates are just x-ray plates with extra
6LiF and I think only ~10% efficient. ~20 years ago Fuji made special
n-plates for ILL that were ~25% efficient but they are no longer available
(?). You should be able to reduce the exposure well below 20 minutes with a
camera and a good 6LiF/ZnS thermal neutron scintillator even with only
10**4 n.cm-2.s-1. See the images Robert Zboray showed in Sydney from a very
low flux Triga reactor, one of which I reproduced in my Munich talk.

It would also be good to compare your fast neutron image with a thermal
neutron image using the same detector and L/D (with different
scintillators). With such small objects, that can be put close to the
scintillator, it would be interesting to see if fast neutrons still have
some advantage for imaging such defects.

I also found Burkard's and Eberhard's comments about the best material and
thickness for a fast neutron Siemens star interesting. It would be good to
see images with these different resolution objects. I also printed a
plastic Siemens star, but 40 mm thick, which I have not yet been able to
test. A final trivial point; please don't use exponent e4 instead of 10**4
for flux; e has a different meaning for mathematicians.

Thanks again for sharing. Alan
______________________________________________________
   Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE
                               from my telephone
<Alan.Hewat at NeutronOptics.com> +33.476.98.41.68
        http://www.NeutronOptics.com/hewat
______________________________________________________

On Mon, 18 Nov 2019, 08:42 Burkhard Schillinger, <
Burkhard.Schillinger at frm2.tum.de> wrote:

> Hello Michael,
>
> congratulations for these nice images!
> For a fast neutron image, that resolution is pretty good. Probably
> better than ours - which shows that a high collimation is also
> important for fast neutrons if you have large samples.
>
> I am also surprised again by your thermal image at L/D of only 35 -
> but that's what you get when you can put the samples up close to the
> detector.
>
>
> For an edge - about everything scatters fast neutrons, but I have
> tried with a 10 mm thick polyethylen pattern (Siemens Star) that was
> 3D printed at our lab. When putting it directly on the detector, it
> was a good measure to test the screen. The 1.5 mm thickness screen was
> much better than the 2.4 mm.
> Not sure what really happens if you take it further away - I assume
> that 10 mm thickness is a good compromise between attenuation and
> scattering blur. You might try 10 mm steel as well, but iron is also a
> diffuse scatterer.
> A perfect edge does not exist.
>
> Good luck with your new 'toys', and Happy Holidays!
>
> Burkhard
>
>
>
>
> > Good day to all,
> >
> > I am happy to announce that we've taken our first fast neutron
> > images at the Phoenix facility in Wisconsin, USA!  Our source is
> > operational now with a source strength of approximately 1.5e12 n/s
> > and an L/D of 450 to achieve a flux at the image plane of
> > approximately 5e5 n/cm^2-s.  Over the next few weeks, we will be
> > increasing our beam current and changing our target to a different
> > material.  We expect to get to full power and have a source strength
> > of 3e13 n/s and a flux at the image plane of approximately 1e7
> > n/cm^2-s.
> >
> > The image attached was taken using a Varex XRD 1621 digital detector
> > array and a PP:ZnS(Cu) screen provided by RCTritec.  The
> > scintillator field of view is 310mm x 310mm, but we plan to use the
> > full field of view of the detector eventually, which is 430mm x
> > 430mm.  The image was taken last night and acquired with 15 frames
> > at 20 seconds each.  The frames were then added and the offsets were
> > applied for background corrections.  The sample is a simulated M982
> > military round.  It is 155mm in diameter.  The outside casing is
> > 1/8" steel and the inside simulant is an HMX equivalent, 6% 6656
> > binder (simulated with 204 epoxy). Chemically it is similar to HMX
> > and RDX but with much less nitrogen.  I have outlined some of the
> > defects of interest that we want to see.
> >
> > We would like to measure the resolution of the system next so I
> > would like to ask if anyone has advice on what material to use as an
> > edge and how thick it should be?  We do not yet have any kind of
> > standard measurement technique for this that I'm aware of, so I
> > would like to know what others are doing.
> >
> > I've also attached a new image we acquired using thermal neutrons of
> > several different military grade .50 caliber ammunition.  We took an
> > X-ray image for comparison and that is shown as well.  The X-ray was
> > done at 350kV but I don't recall the current.  The neutron image was
> > acquired using our thermal neutron generator with heavy water
> > moderator, the L/D was 35 and the flux was approximately 1e4
> > n/cm^2-s.  The exposure time on a neutron sensitive image plate was
> > 20 minutes.
> >
> > I hope everyone is well, it was great to meet so many of you in
> > Garching last month and I wish you all happy holidays as they
> > approach us soon.
> >
> > Best regards,
> > Michael
> >
> > Michael Taylor Ph.D.
> > Neutron Radiography Product Manager
> > Phoenix LLC
> > 2555 Industrial Drive
> > Madison, WI 53717
> > 608-515-3214
>
>
>
> --
> Dr. Burkhard Schillinger
> Technische Universität München - FRM II
> Heinz Maier-Leibnitz Zentrum
> Lichtenbergstr.1
> D-85748 Garching
> Germany
> Tel. +49 89 289-12185
>
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