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RE: New Detector
Thanks for the reply. So there is no great news really (except perhaps
about spending big money for another unusable gadget being in preparation).
Bigger Si detectors have been available for some time, which
have about the same resolution, efficiency and energy range.
However, they need neither liquid He nor liquid nitrogen; a small
Peltier suffices (cooling them to 0 C brings them to about 100 eV
FWHM). Since the Peltier consumes very little (typically gets
powered off the preamp power connector meant for a Ge or similar
detector), using them with a portable MCA is OK (I have tried
this with ours, at least, and it worked fine, just plug and play).
Dimiter
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Dimiter Popoff
Transgalactic Instruments
http://transgalactic.freeyellow.com
-----Original Message-----
From: "Doty, Patrick" <fpdoty@SANDIA.GOV>
Date: Sun, 20 Apr 2003 15:14:31 -0600
To: radsafe@list.vanderbilt.edu
Subject: RE: New Detector
It probably takes a small amount of helium, due to the small active volume
(1 x 1 x 0.25 mm3, as reported in "Gamma-ray spectrometers using
superconducting transition edge sensors with external active feedback bias"
IEEE Transactions on Applied Superconductivity ; March 2001; vol.11, no.1,
pt.1, p.743-6).
The absorber is a 250 micrometer thick film of tin. Energy resolution on
the order of 100 eV @ 60 keV has been reported. Presumably similar FWHM is
achievable for Co-57 gammas, however the PE cross section at 122 is ten
times lower than at 60 keV. Compton scattering in the detector dominates
the response to 662 keV or 1332 keV photons.
-----Original Message-----
From: Dimiter Popoff [mailto:tgi@cit.bg]
Sent: Saturday, April 19, 2003 9:55 AM
To: radsafe@list.vanderbilt.edu
Subject: RE: New Detector
The real question - which was already implied in at least one posting - is
"what is the daily consumption of liquid He?" . I'd prefer it expressed
in liters/day, but will manage the conversion, if necessary :-).
Also, I would be curious about the resolution - say, in keV FWHM @ 1332.5
keV
and @ 122 keV. If too small to talk 1332.5 keV, 661.6 keV would be
interesting, too.
Dimiter
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Transgalactic Instruments
http://transgalactic.freeyellow.com
-----Original Message-----
From: Elaine Marshall [mailto:emarshall@fnal.gov]
Sent: Friday, April 18, 2003 12:07 PM
To: radsafe@list.vanderbilt.edu
Subject: New Detector
Found the following article in today's news.
Weapons Lab Rolls Out New Radiation Detectors
L I V E R M O R E, Calif., April 18 A cell phone that will be able
to tell the difference between a "dirty bomb" and someone who's
undergone radiation treatment is among the next generation of
anti-terrorism tools being worked on by national weapons lab scientists.
The device, known as RadNet, is designed to make calls, surf the Web,
act as a Personal Digital Assistant, pinpoint locations with Global
Positioning System technology and sniff out nuclear materials with a
cutting-edge sensor. It is one of several national security projects
under development at Lawrence Livermore National Laboratory.
"It almost sounds like science fiction, but it's here today," said Simon
Labov, director of the new Radiation Detection Center at Lawrence
Livermore, which celebrated its formal opening Thursday with a display
of the RadNet and other devices.
U.S. Rep. Ellen Tauscher, D-Calif., who was at the lab for the opening
and for a daylong conference of emergency response officials, called the
projects "the kind of work and the kind of science that is fundamental
to our being able to protect the American people from weapons of mass
destruction."
Lab officials showed off their work with theatrical flair, whipping away
white cloths from some prototypes.
"This is called UltraSpec," Labov said as he displayed the Ultra-High
Resolution Gamma Ray and Neutron Spectrometers. "No other instrument
like it in the world."
The Ultra-Spec uses extremely low temperatures within one degree of
absolute zero, or -459 degrees Fahrenheit to measure gamma rays from
nuclear materials that might be present in terrorist bombs and weapons.
It works by recording, very precisely, the rise in temperature when a
single gamma ray hits the detector's superconducting material, which is
usually tin.
"At these low temperatures we get incredible sensitivity," Labov said.
Much of the technology on display Thursday uses gamma ray detection
because gamma rays travel farther than other substances emitted by
nuclear material and are easier to spot and identify, Labov said.
Nuclear material also emits neutrons, which is part of some of the
detection technology.
RadNet grabbed a lot of the attention Thursday with its small size
in the range of a cellular phone circa 1995 and big agenda.
Scientists hope to have prototypes ready for testing within a few months
and could have the devices ready for action in about two years.
The Associated Press
+++++++++++++++++++++++++++++++++++
+ Elaine T. Marshall
+ Fermi National Accelerator Laboratory
+ Facilities Engineering Services Section
+ Administration/Safety
+ Voice: (630 840-8756/Fax: (630) 840-4980
+ E-Mail: HYPERLINK "mailto:EMarshall@fnal.gov"EMarshall@fnal.gov
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