[Fast-Neutrons] First fast neutron images at Phoenix
Trtik Pavel (PSI)
pavel.trtik at psi.ch
Tue Nov 19 16:42:36 CET 2019
Hi Michael, hi everybody
very nice, congratulations!
Regarding the resolution assessment, may I suggest you also try Fourier Ring Correlation (FRC) for resolution assessment. It has got the advantage that it does not require a test pattern, one just needs to have 2 corresponding images of the given object, so here you can use 2 x 7 projections from the original stock.
FRC has been created for the cases of imaging modalities for which the provision of perfect imaging test objects/patterns is difficult (such as for TEM), which seems to be the case here as well.
With best regards
Paul Scherrer Institut
5232 Villigen PSI
Telefon: +41 56 310 55 79
E-Mail: pavel.trtik at psi.ch
From: fast-neutrons-bounces at neutronsources.org <fast-neutrons-bounces at neutronsources.org> On Behalf Of Michael Taylor
Sent: Samstag, 16. November 2019 19:46
To: fast-neutrons at neutronsources.org
Subject: [Fast-Neutrons] First fast neutron images at Phoenix
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.
Michael Taylor Ph.D.
Neutron Radiography Product Manager
2555 Industrial Drive
Madison, WI 53717
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