Meanwhile, back in the lab...


In our last episode, a neutron guide at NIST broke from radiation damage,
sending a chunk of glass through the magnesium window and destroying my
monochrometer.

The guide had been fixed weeks ago, the monochrometer recently replaced
and the shielding moved back in, allowing me access to that liquid
nitrogen dewar that had been blocked in for a month. I've adjusted the
rotation and tilt angles of the monochrometer to maximize flux, and now
I'm trying to take a beam picture to see what it looks like.

We have a wonderful imaging plate that's loaded with lithium-6; expose it
directly to the beam and read it out in the BAS-2000. So I built a jig to
hold it, brought Health Physics in to check the setup, gave it a 30 second
exposure, and brought it to Building 245 to read it. And found out the
BAS-2000 had been broken for some time, and there's no plans to fix or
replace it. So I tried reading it on the BAS-1800II, but that only
accepts magnetic plates, and this one isn't magnetic.

Plan B was to use dysprosium foil, which activates in neutrons and emits
betas with a half life of a few hours. Except our dysprosium foil is
small, and I wanted a larger picture. And big peices of dysprosium are
another one of those things you don't just buy at Staples.

Plan C is to activate a copper plate which we happened to have laying
around. That has a smaller capture cross-section and the isotope of
interest has a half-life of 13 hours, which translates to a whopping
exposure to get something useful. The reactor was down Monday and
Tuesday.

So I was ready to expose it today, after the talk by our guest speaker.
But Health Physics had some concerns about the amount of radioactive
material to be transported, and where it will be kept. And then they
disappeared for a while. Turns out they were trying to figure out how
many prompt gammas would be created. I don't think there'll be any, I got
some ENDF data that seemed to say no prompt gammas until 100 keV, and my
neutrons are little meV. And with hours to expose, wait out some
short-lived products, and transfer to an imaging plate, it just got late.
So we'll try it again tomorrow.

And science marches on. Sort of.

Nothing unusual, just another day in the lab.

--
"Tell me, Dr. Einstein, at what time does Boston arrive at this train?"
.

Relevant Pages

  • Re: Meanwhile, back in the lab...
    ... >In our last episode, a neutron guide at NIST broke from radiation damage, ... >The guide had been fixed weeks ago, the monochrometer recently replaced ... >neutrons are little meV. ... >short-lived products, and transfer to an imaging plate, it just got late. ...
    (sci.physics)
  • Re: Meanwhile, back in the lab...
    ... > In our last episode, a neutron guide at NIST broke from radiation damage, ... > Plan B was to use dysprosium foil, which activates in neutrons and emits ... > neutrons are little meV. ... > short-lived products, and transfer to an imaging plate, it just got late. ...
    (sci.physics)
  • Re: Meanwhile, back in the lab...
    ... a neutron guide at NIST broke from radiation ... Except our dysprosium foil is ... > neutrons are little meV. ... > short-lived products, and transfer to an imaging plate, it just got ...
    (sci.physics)
  • Re: Meanwhile, back in the lab...
    ... a neutron guide at NIST broke from radiation ... | We have a wonderful imaging plate that's loaded with lithium-6; ... Except our dysprosium foil is ... | neutrons are little meV. ...
    (sci.physics)