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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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Transgalactic Instruments

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-----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

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-----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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