Maker Pro
Maker Pro

gamma ray detection

J

Jamie Morken

Jan 1, 1970
0
Hi all,

Is there a semiconductor replacement for the traditional geiger
avalanche tube with similar performance? Or what are the best types of
semiconductors to use for this? Ideally a 2dimensional array like a CCD
or CMOS camera, but a geiger camera is what I am thinking of. The
application is for measuring emissions from weak gamma sources to see if
single event emissions have a measureable beam angle.

cheers,
Jamie
 
B

Bret Cannon

Jan 1, 1970
0
Jamie Morken said:
Hi all,

Is there a semiconductor replacement for the traditional geiger avalanche
tube with similar performance? Or what are the best types of
semiconductors to use for this? Ideally a 2dimensional array like a CCD
or CMOS camera, but a geiger camera is what I am thinking of. The
application is for measuring emissions from weak gamma sources to see if
single event emissions have a measureable beam angle.

cheers,
Jamie
Silicon drift detectors are used to detect x-rays (see Amptek for example),
but due to the low atomic number they have poor sensitivity for higher
energy gamma rays.

High purity germanium detectors at liquid nitrogen temperatures have
excellent energy resolution, but can easily cost more than $100k each.
Mercury zinc telluride crystals are used for gamma detection, but need
pixelated electrodes for the best performance as well as sophisticated
electronics to deal with the high density of p-type traps and are also
expensive.

If you only want to detect gammas and not measure their energy, you might
want to look a plastic scintillators or perhaps thallium doped cesium iodide
crystals as less expensive alternatives to semiconductors.

Bret Cannon
 
O

Okkim Atnarivik

Jan 1, 1970
0
: > Is there a semiconductor replacement for the traditional geiger
: > avalanche tube with similar performance?

: If you want similar performance to a geiger tube, why not
: a geiger tube? It'd be difficult to match the active volume

The 'multipixel' version of the Geiger counter is known as the
Wire Chamber.

Regards,
Mikko
 
T

Tim Williams

Jan 1, 1970
0
John Larkin said:
I had to photograph that screen. How does one capture a full DOS
screen running under XP?

DOSBox.
 
J

Jamie Morken

Jan 1, 1970
0
One cute wire chamber version uses a single long wire that zigzags
between the mylar sheets, making a big s-curve. One uses
high-resistance wire, tungsten maybe. The current at the ends is
modulated by the wire resistance from the hit site, so you can
localize the hit location pretty well, than map that into an x-y
array.

ftp://jjlarkin.lmi.net/Peach.JPG

Wire chambers can be built by mere mortals, people who don't own semi
fabs.

I had to photograph that screen. How does one capture a full DOS
screen running under XP?

John

Hi John,

That is very cool, 400 pixels with a single wire! :) I guess the mylar
sheets are charged like a HV capacitor, and the wire is not charged but
has a constant current source put through it from the measurement
circuit, and somehow the modulations on the current can tell you
accurately what part of the wire had an electron/charged particle fly by
it? I guess it is like a network analyzer or something hooked up to the
wire. How does the sensitivity to gamma rays compare to a typical off
the shelf geiger counter? Also do you use electrical insulation between
adjacent columns and rows to prevent detection cross-talk? Sorry for
all the questions but it is an interesting device. :)

I think one limitation though may be detecting nearly spaced or
simultaneous events, since there is only one wire, if there are multiple
electrons/charged particles flying by in different locations I'm not
sure if that could be detected with one wire?

cheers,
Jamie
 
J

Jamie Morken

Jan 1, 1970
0
One applies the HV to the wire and grounds the aluminized mylar
sheets. There's some gas mixture that makes nice ion multiplier
effects. The wire is almost invisible, just a few mils in diameter, so
the electric field gradient close to the wire in insane. There's a
huge ion multiplier gain, close to geiger mode but not quite.

Path: s02-b33.iad!npeersf01.iad.highwinds-media.com!npeer01.iad.highwinds-media.com!news.highwinds-media.com!feed-me.highwinds-media.com!Xl.tags.giganews.com!border1.nntp.dca.giganews.com!nntp.giganews.com!local2.nntp.dca.giganews.com!nntp.supernews.com!news.supernews.com.POSTED!not-for-mail
NNTP-Posting-Date: Mon, 30 Aug 2010 19:20:46 -0500
From: John Larkin<[email protected]>
Newsgroups: sci.electronics.design
Subject: Re: gamma ray detection
Date: Mon, 30 Aug 2010 17:20:35 -0700
Message-ID:<[email protected]>
References:<[email protected]> <[email protected]> <[email protected]> <[email protected]> <[email protected]>
X-Newsreader: Forte Agent 1.91/32.564
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Lines: 91
X-Trace: sv3-Q9uYuCyTlCg2FmyYNsNTKrr+8KNWCj76dVWkeT++3zI1F6M7D79Ab0kUoqmrzNZVd7TGCO71vwk9BK1!uuGVoXaJdNzm9jwFH63PDmM4YlgRtwbymfltLvJTgElM2VncDjnRuHeg2IvqxRetyCKpPX2kpsLE!6p62fA==
X-Complaints-To: www.supernews.com/docs/abuse.html
X-DMCA-Complaints-To: www.supernews.com/docs/dmca.html
X-Abuse-and-DMCA-Info: Please be sure to forward a copy of ALL headers
X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint properly
X-Postfilter: 1.3.40
Bytes: 5218
Xref: Hurricane-Charley sci.electronics.design:752687
X-Received-Date: Tue, 31 Aug 2010 00:20:46 UTC (s02-b33.iad)



One applies the HV to the wire and grounds the aluminized mylar
sheets. There's some gas mixture that makes nice ion multiplier
effects. The wire is almost invisible, just a few mils in diameter, so
the electric field gradient close to the wire in insane. There's a
huge ion multiplier gain, close to geiger mode but not quite.

As I recall, we terminated each end of the wire, amplified the pulses
a bit, and triggered an ADC on the peak. Some simple math mapped the
two pulse amplitudes into position along the wire, with some
calibrations maybe. The product was a Safeway shopping cart sort of
thing with a big, like 1m square, detector on the bottom. The idea was
to sweep a floor looking for hot particles. Lots of facilities need to
do this. This sort of thing is a low-rate detector that will get
confused by multiple hits.

I also did a classic wire chamber thing for UCLA/CERN. That had a
zillion parallel wires per plane, with an amplifier, discriminator,
and time-digital converter per wire. Looking at the timing data, one
can interpolate the hit position to a fine fraction of the wire pitch.
Multiple planes gathered X-Y data and particle path curvature in the
magnetic fields. These were Gev particles that made a lot of ions in a
lot of chambers without slowing down much. These arrays generate
mountains of data on thousands of channels, and the problem is to
process huge rates of junk hits down to a set that's possible to
archive and analyze. We used a bunch of FPGAs in a data flow
peristaltic sort of thing. Messy.

John

Hi,

That X-Y wire chamber sounds very cool. I wonder if anyone ever tried
hooking it up to a strong gamma source instead of a particle source?
The experiment I was interested in was to see if a single gamma ray can
be detected by multiple "chambers" at the same time. It sounds like the
setup's you've worked with are capable of finding that out. Ie. one
experiement could be to record the X-Y grid distances between
simultaneous detections as they occur over time, and then average them
to see if the average distance is less than the distance that would be
expected if these simultaneous detections were from separate gamma rays.
If the distance is less then I think it could be assumed that a single
gamma ray was being absorbed twice.

cheers,
Jamie
 
M

Martin Brown

Jan 1, 1970
0
I had to photograph that screen. How does one capture a full DOS
screen running under XP?

Printscreen and paste the buffer into your favourite graphics app.

Regards,
Martin Brown
 
J

JW

Jan 1, 1970
0
The same as in DOS, or any MS OS since. Hold down the 'CTRL' key and
tap the 'Print Screen' key. The screen will be copied to the clipboard.
Open 'Paint' or another graphics program and paste it.

That seems to work fine for a DOS *window*, but a when running a full
screen DOS session CTRL + ENTER from the DOS command line, it does not
work. At least on my machine it doesn't, I get only whatever was on the
screen in Windows.
 
J

JW

Jan 1, 1970
0
That seems to work fine for a DOS *window*, but a when running a full
screen DOS session CTRL + ENTER from the DOS command line, it does not ^^^^^^^^^^^^
work. At least on my machine it doesn't, I get only whatever was on the
screen in Windows.

Correction ALT + ENTER.
 
M

Martin Brown

Jan 1, 1970
0
All I can ever capture is a plain white screen with black borders at
the top and bottom. This is a full-screen DOS graphics thing, from a
DOS PowerBasic program, written in 1997 to run under DOS.

Try running it as a Windowed DOS program and use Alt-PrtScrn when you
want to do screen capture. Otherwise I suspect you will need to install
some antique TSR with a Windowsian twist to make full screen DOS mode
PrintScreen capture behave like a normal Windows application. Blame
MickeySoft!

There is a possibility that PrintScreen is working, but that PowerBasic
is bypassing the screen buffer it is supposed to use.

Regards,
Martin Brown
 
T

Tim Williams

Jan 1, 1970
0
Martin Brown said:
Try running it as a Windowed DOS program and use Alt-PrtScrn when you
want to do screen capture. Otherwise I suspect you will need to install
some antique TSR with a Windowsian twist to make full screen DOS mode
PrintScreen capture behave like a normal Windows application. Blame
MickeySoft!

....Or install DOSBox...

Runs better anyway (semantically speaking, but always slower), since it's
fully 32 or 64 bit. Can't run NTVDM in 64 bit mode.

Tim
 
S

Sjouke Burry

Jan 1, 1970
0
Robert said:
Nope; "Write fault error writing device PRN".
Impossible to Abort/Retry until one re-issues CTRL + Print Screen.
Guess again.
I tried two dos-age grabbers, they did text oke, but graphics was
hopeless, with confused multiple copy's in the gif file.
If you(OP or others) want them, let me know.
 
Top