[ RadSafe ] Re: New Method for Making Improved Radiation Detectors

Fri Jun 1 20:04:08 CDT 2007

Jim,

> ....
> We are, however, investing in a lanthanum-bromide (LaBr3) spectrometer
> for high(er) resolution room-temperature spectometry. 

I haven't seen one of these. Can you give some ballpark figures,
I mean resolution, price etc. ?

>    Currently, for in-situ work,  we have a field portable (but not 
> conveniently so) liquid-nitrogen cooled high-purity germanium (HpGe) 
> spectrometer, and we should soon be receiving funding to invest in 
> one of the electrically-cooled portable HpGe units currently on the market.      

I have not had in my hands one (electrically cooled, that is,
I do make HPGe based MCAs :-), but I am told they are far from
being much more convenient than the plain LN2 ones. I don't remember
well now - the guy (a customer) told me about them a year or two
ago, but he spoke about lots of inconveniencies to carry with, if
you haven't looked down all the detail about them this might be
a good idea. These are products made by a competitor of mine company but
I am just sharing a memory, I am not at all certain how correct
that info is, just worth issuing a warning.

Dimiter

P.S. See my "walking" photo gallery:
http://www.flickr.com/photos/8359035@N02/sets/72157600228621276/  :-)

------------------------------------------------------
Dimiter Popoff               Transgalactic Instruments

http://www.tgi-sci.com
------------------------------------------------------

> Date: Fri, 01 Jun 2007 19:32:16 -0400
> From: "Jim Hardeman" <Jim_Hardeman at dnr.state.ga.us>
> To: <radsafe at radlab.nl>
> Subject: [ RadSafe ] Re: New Method for Making Improved Radiation Detectors
> 
> Dimiter --
> 
>   You're absolutely correct -- the resolution on these CZT detectors
> is pretty amazing for room-temperature spectrometers. Not only
> do they separate the Co-60 1173 and 1332 peaks well, but they
> also truly separate the Zn-65 1116 peak from the Co-60 1173 peak
> in our gamma standards -- something that I've never seen a NaI
> spectometer do. Unfortunately, due to their small size (any where
> from 7 x 7 x 3.5 mm to perhaps 10 x 10 x 5 cm) and low efficiency
> (typically ~2-3% relative efficiency) we've found CZT-based instruments
> to be of limited use -- at least for our purposes.    
> 
> We've been using and evaluating a number of handheld spectrometers 
> for quite some time, and both for our routine incident response and
> homeland security work, NaI-based spectrometers are still the "workhorses".
> We are, however, investing in a lanthanum-bromide (LaBr3) spectrometer
> for high(er) resolution room-temperature spectometry. In my opinion,
> LaBr3 has the advantage of high-resolution, like CZT, but at  an efficiency
> similar to (or in some cases surpassing) NaI spectrometers, and at 
> a cost that isn't "obscene". If the detector costs come down a little,
> I can see LaBr3 spectrometers being the "sweet spot" for room-temperature
> spectrometry -- at least until the next new, great thing comes along.
> 
>    Currently, for in-situ work,  we have a field portable (but not 
> conveniently so) liquid-nitrogen cooled high-purity germanium (HpGe) 
> spectrometer, and we should soon be receiving funding to invest in 
> one of the electrically-cooled portable HpGe units currently on the market.      
>  
> Jim Hardeman, Manager
> Environmental Radiation Program
> Environmental Protection Division
> Georgia Department of Natural Resources
> 4220 International Parkway, Suite 100
> Atlanta, GA 30354
> (404) 362-2675
> Fax: (404) 362-2653
> Personal fax: (678) 692-6939
> E-mail: Jim_Hardeman at dnr.state.ga.us 
> 
> 
> >>> Dimiter Popoff <didi at tgi-sci.com> 6/1/2007 18:05 >>>
> Thanks for posting that - pretty interesting, apparently the CdZnTe
> detectors keep on improving. This is the first time I see both
> the 1173 and 1332.5 lines on a CdTe spectrum, and the resolution
> appears to be decent - far from Ge, but well, no LN2.
> I wonder how good (if usable at all?) the efficiency would be,
> there are too few counts between the two peaks (which is not how
> things are) and I suspect that the spectrum might be looking like
> shown in log scale while being actually in linear... 
> 
> Whatever the details, looks like great progress for CdZnTe.
> 
> (I found the article with the photo/spectrum at
> http://www.bnl.gov/bnlweb/pubaf/pr/PR_display.asp?prID=07-57 )
> 
> Dimiter
> 
> P.S. See my "walking" photo gallery:
> http://www.flickr.com/photos/8359035@N02/sets/72157600228621276/  :-)
> 
> 
> ------------------------------------------------------
> Dimiter Popoff               Transgalactic Instruments
> 
> http://www.tgi-sci.com
> ------------------------------------------------------
> 
> 
> > Date: Fri, 1 Jun 2007 10:17:04 -0700 (PDT)
> > From: ROY HERREN <royherren2005 at yahoo.com>
> > To: radsafe at radlab.nl 
> > Subject: [ RadSafe ] New Method for Making Improved Radiation Detectors
> > 
> > For release on May 31, 2007, 1:00:00 PM
> >   Contacts: Pete Genzer, genzer at bnl.gov, (631)344-3174 or 
> > Mona Rowe, mrowe at bnl.gov, (631) 344-5056
> > 
> >    New Method for Making Improved Radiation Detectors 
> > UPTON, NY * Scientists at the U.S. Department of Energy's
> > Brookhaven National Laboratory, with funding from DOE's
> > National Nuclear Security Administration, have devised
> > ways to improve the performance of radiation detectors,
> > such as those used by law enforcement agencies to locate
> > and identify radioactive material.   The improved sensors,
> > for which the Laboratory has filed a U.S. provisional
> > patent application, can be used at room temperature, 
> > which makes them more practical and cost-effective than
> > existing detectors with similar performance, which must
> > be operated at very cold temperatures using expensive
> > liquid nitrogen. They can also more accurately detect
> > the X-rays and gamma rays emitted by radiological sources
> > such as dirty bombs and other illicit materials.   "Improving
> > the performance of radiation detectors could improve 
> > the efficiency and accuracy of cargo screening at U.S.
> > ports," said Brookhaven physicist Aleksey Bolotnikov,
> > one of the inventors.   Radiation detectors work by detecting
> > electrons and "holes" * vacancies left by liberated electrons
> > * when ionizing radiation or high-energy particles strike
> > the detector crystal. When the free electrons and holes
> > flow toward electrodes (an anode and a cathode) at either
> > end of the detector, they generate a signal that can 
> > be measured and recorded.   In an ideal detector, all 
> > of the electrons and holes created by the ionization 
> > process would arrive at the electrodes. But in reality,
> > holes travel a very short distance before getting trapped
> > by defects in the crystal. Also, because the electrostatic
> > field inside the detector causes some of the electrons
> > to drift, not all of them arrive at the anode. These 
> > losses lead to a subsequent inaccuracy in radiation measurements.
> > The Brookhaven-designed sensors improve on this situation
> > by combining methods to shield the detector and focus
> > the electrons toward the anode. In addition, the electrodes
> > at each end of the detector give information about how
> > many electrons/holes get trapped. This "correction factor"
> > can then be used to reconstruct the number of electrons/holes
> > originally created by incident gamma rays or high-energy
> > particles.   "Together, these techniques enhance the energy
> > resolution and efficiency of these detectors. In practical
> > terms it means that the improved devices will be able
> > to detect more minute quantities of radiation, detect
> > radioactive materials more quickly or from greater distances,
> > better identify the source of the radiation, and distinguish
> > illicit sources of concern from common naturally occurring
> > radioactive materials," Bolotnikov said.   The patent 
> > application covers the improved high-energy detectors,
> > as well as methods for making and using them. Details
> > of the electrode design and processing methods are also
> > included.   This technology is now available for licensing.
> > For licensing information, please contact: Kimberley 
> > Elcess, Principal Licensing Specialist, Brookhaven National
> > Laboratory, (631) 344-4151, elcess at bnl.gov.   Note to 
> > local editors: Aleksey Bolotnikov lives in South Setauket,
> > New York.         To see the National Nuclear Security 
> > Administration's press release, click here.    One of 
> > ten national laboratories overseen and primarily funded
> > by the Office of Science of the U.S. Department of Energy
> > (DOE), Brookhaven National Laboratory conducts research
> > in the physical, biomedical, and environmental sciences,
> > as well as in energy technologies and national security.
> > Brookhaven Lab also builds and operates major scientific
> > facilities available to university, industry and government
> > researchers. Brookhaven is operated and managed for DOE's
> > Office of Science by Brookhaven Science Associates, a
> > limited-liability company founded by the Research Foundation
> > of State University of New York on behalf of Stony Brook
> > University, the largest academic user of Laboratory facilities,
> > and Battelle, a nonprofit, applied science and technology
> > organization.   Visit Brookhaven Lab's electronic newsroom
> > for links, news archives, graphics, and more: http://www.bnl.gov/newsroom 
> >    
> > Roy Herren
> >        