Re: Meanwhile, back in the lab...

"Gregory L. Hansen" <glhansen@xxxxxxxxxxxxxxxxxxxxx> wrote in message
news:d6gp2r$2tn$1@xxxxxxxxxxxxxxxxxxxxxxxxxxx
|
| 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.

Nice story. Too bad we don't see more like this on these groups.

FrediFizzx

http://www.vacuum-physics.com/QVC/quantum_vacuum_charge.pdf
or postscript
http://www.vacuum-physics.com/QVC/quantum_vacuum_charge.ps

.

Relevant Pages

  • 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...
    ... >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)
  • 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 ... We have a wonderful imaging plate that's loaded with lithium-6; ... Plan B was to use dysprosium foil, which activates in neutrons and emits ...
    (sci.physics)