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

[Burkhard Schillinger]

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