FAQ - Introducing the Ludlum 2200! A perfect solution

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Richard Hull
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FAQ - Introducing the Ludlum 2200! A perfect solution

Post by Richard Hull »

This "Wonder-Box" has had a few posts related to it, but here is the FAQ!

NIM is a great solution for any and all nuclear measurement solutions. Nothing stands in the way of NIM in getting good nuclear measurement data. I, long ago, wrote a FAQ on NIM. NIM demands a great deal of fore-knowledge related to nuclear instrumentation. It also tugs at the wallet like a thirsty new-born calf. A full blown NIM system purchased used from E-bay can cost from $700 to over $1500. Over $3000 if bought new!

You may look at the Ludlum 2200 as a pre-wired NIM system in a box. E-bay prices for a warranted, working 2200 can range from $400 to $700. Regardless of the detector you might wish to test or set up for real nuclear measurement, the 2200 will handle it!

A recent superb post by Joe Ballantyne gives his use of the 2200 to test and choose his ideal neutron counting tube. You are recommended to this fine exposition as a real world example. It is deeply buried in the construction forum near the bottom of his long running post on his fusor.

viewtopic.php?t=14396

Below you will see the instrument in a detailed group of images. I will add to this post a number of tips and instructions all to be found in the thick owners manual. My goal is simplification of operation and explanation of the various controls. While all the knobs and dials may confuse many, they are really purposeful. A few will not be used by the rank amateur trying to build a neutron detection system. The beauty of this instrument is the it can be a Geiger counter, (Alpha-Beta),a PMT scintillator counter, (gamma), a neutron counter, and even an ion chamber based electronics platform!
You just need to supply the detector tube related to what nuclear counter you want to make. It will also test and qualify most any nuclear detector tube you might happen on to.

Now to the more detailed discussion of the knobs and what they do.

The first photos below show the front panel. I have numbered the knobs and variable controls for this discussion in image #2. I will cover the 2200 by the "blocks" that are akin to their NIM counter parts. These blocks make up this amazing all-in-one NIM-like instrument.

The input: Here you are on your own. What do you want to make? The C BNC connector at the lower right is where you plug in your detector. Cabling is also up to you. You will have to match whatever plug is on your detection tube to the Ludlum C BNC on the front of the 2200.
A Geiger counter will demand a GM tube. A scintillation counter will demand a PMT tube mated to its detection crystal. A neutron counter will demand a neutron detection tube. Most here will go for the neutron counter capability of the 2200. There are many neutron detection tubes to choose from. The best are BF3 tubes and 3He tubes. There are any number of relatively inexpensive Russian surplus neutron tubes on the market, (e-bay). Some Russian Neutron detectors are easy to use, others like Corona tubes, can be cantankerous to bring into good operation.

Powering the detector tube of choice: This is the first important block in any nuclear detection instrument. Detectors all demand a wide range of voltages to make them functional. These voltages range from about 300 volts, (cheap Russian GM tubes), to over 3000volts for some very large BF3 neutron tubes. The average for most all Geiger tubes runs from 300 volts to 1000 volts. PMT scintillation tubes start around 700 volts and can go as high as 1200 volts. 3He neutron tubes can demand from about 800 volts for a tiny tube to 2000 volts for a giant tube. BF3 neutron tubes start at 1000 volts for smaller tubes but even some small tubes need 1400-2000 volts!

Never fear...The 2200 has a variable power supply for most any detector tube from 0-2500 volts! If you don't know the operating voltage of your detection tube, you can slowly advance the voltage to it, until it starts to work or count, provided you have an appropriate small source of nuclear radiation for it to spring into action at the correct voltage.

Power knobs: It is best to print out a copy of the second image below to follow the by the numbers routine. There are 3 key knobs in the power block. Knob #8 is the on-off knob turn it from off to line the instrument powers up. Knob #2 instructs the meter to read only the high voltage on the lower scale of the meter to the left of it. It is in the correct position here "HV". Knob #5 is the high voltage control. It is best turned fully CCW to zero voltage before turning on the instrument. It is a ten turn knob that allows for fine voltage adjustment. A CW turn on the knob raises the voltage shown on the meter. On an unknown tube, raise the voltage very slowly. Once the counter starts to work at an optimum voltage, use a magic marker to write this voltage on the detector tube.

Visual indicators of counting: This output block consists of 2 selectable readouts of counting. At the top of the instrument is an LED digital counting display It advances a numerical count for each detection. It is always on and has 3 controls. The two pushbuttons to the right of the LED display start the count, "COUNT" and can freeze the count where it is at the press of the "HOLD" button. Note: the display is cleared when the count button is pressed to start a new count. The control marked #1 is a display dimmer control. Adjust it to suit your light level.
The second count readout is the rate meter. This uses the top scale on the analog meter face. This gives an average count rate in CPM by a needle moving about the average CPM count rate. This part of the rate meter has a number of controls. To turn the meter off HV adjust reading, turn knob #2 to "rate". This turns the rate meter on. There is a toggle switch just below the meter with "S"low and "F"ast postions. Fast can have the needle moving rather quickly oscillating around the correct CPM rate. In the slow position the needle smoothly floats up to an integrating average CPM rate. Knob #4 is the rate meter range switch. If you are counting at 23,000 cpm like a Geiger counter might, switch #4 will need to be in the X100 position. The little red button just below the meter with force the needle to zero in ratemeter mode.

You might say, "couldn't we just time the digital counter and get a precise number of detections over a minute?" Yes, they built in a timer on the 2200 for you to do just that! There are two black thumb wheels with a "minutes" label below it. It is just to the right of the meter. They are set to "01". The knob #3 is the timer multiplier. We see it is set to the X1 position. In this position based on the thumbwheel setting, the digital counter will count for 1 minute and then stop. X10 on knob #3 will count for ten minutes, etc.

Now, to what makes this thing count!

This is the electronic amplifier/ discriminator and level setting block of the instrument. It is the workhorse of the instrument and the most difficult to master. The manual stresses the little potentiometer at the very bottom of the 2200 marked "DISCR" needs to be set critically for the type of signal level that will come from you operating detector. This really sets the ultimate gain of the built in preamp. The lowest gain is fully CCW on this little screw driver adjust, "locked down pot". The highest gain is fully CW. WAIT! they recommend never banging the pot over to full CW against its stop as this will put so much gain on the preamp that you will have continuous noise counts or even oscillation. Proportional counters like neutron tubes need a lot of preamp gain. GM tubes give large output voltages and need almost no gain in the preamp at all. The 2200 manual give instructions on setting this critical pot. (You will need an O'scope and NIM type pulser to critically set this). it is critically set in conjunction with knob #7 "Threshold". For this adjustment the threshold is set to 1.00 and the DISCR pot is set to just detect a preset 10millivolt input pulse from the NIM pulser. (the counter just starts to count).

The above is a tough setting to achieve with accuracy without other electronic gear, as noted. It can be set with no instrument to a limited degree for high gain to work a proportional neutron tube by moving the knob #7 to the 0040 setting and moving the DISCR pot CW until the counter goes bonkers counting noise or just gets a count every now and then. Note: all this must be done with nothing hooked to the C BNC input!!!

If you ever want to set up a GM tube, the DISCR pot must be almost all the way CCW, (low gain).

Once the DISC is set. You are now ready to test your neutron tube.

Connect your tube with a proper cable. Make sure the tube is in a moderator. Turn the voltage control all the way to CCW zero volts.
Turn control #2 to HV. Set the control #7 to 1.00
Turn power on and set control #10 to X10 position (this will give you a 10 minute count as you try to make the tube count background)
Hopefully you have some basic knowledge of you tube's range of operational voltage.
Slowly bring the voltage up until you see the counter maybe count to 1 or 2 counts over a minute. (Background)
If you think you are too high in voltage for you tube, try turning Control #7 to a point below 1.00. This decreases the pulse height needed to start counting. It is an art form homing in on the operating point of your detector. However, it must be mastered.

If you have a source of neutrons place it beside the tube in the moderator and hit the count button. Hopefully, over a one minute timed count it is well above a one minute background count with no neutron source in with the tube.

Finally, now to knob #6 "WINDOW". This is not to be used and the toggle switch below it is set to "OFF". Just take it to 000 and ignore it until you are advanced enough to need to window detect. ( a far more rare instance)

You will note switch #2 has a battery position and control #8 has a BAT and CHG position. the 2200 can be made portable! You will need only NiCad rechargeable batteries installed if you go portable#2 in BAT position lets you see on the meter the battery state of charge in the marked zone.
With new batteries and plugged into the wall outlet switch #8 in the CHG position will charge the batteries. Once out in the field, #8 in the BAT position will turn the 2200 on. You will most likely never use battery power, but it is there if you want it.

There you have it! The Ludlum 2200 is the lower cost electronic neutron detection instrument if you have a neutron detection tube.

Remember to click on the annotated images to enlarge them for easy reading.


Richard Hull
Attachments
I had a bunch of untested BF3 neutron detector tubes to test and qualify to make sure they functioned as expected.
I had a bunch of untested BF3 neutron detector tubes to test and qualify to make sure they functioned as expected.
This is your reference image with the numbered dials referred to in the text above.
This is your reference image with the numbered dials referred to in the text above.
A close up of the lower important region of the 2200
A close up of the lower important region of the 2200
Ludlum 2200 (6).anno.jpg
Ludlum 2200 (13).anno.jpg
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Jim Kovalchick
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Re: FAQ - Introducing the Ludlum 2200! A perfect solution

Post by Jim Kovalchick »

Richard,
Thanks for this great FAQ. It could save some folks a lot of trouble and bucks when they might otherwise try to hodge podge a detection system together with NIM components. Don't get me wrong; I use NIM all the time. When it comes to proportional tubes NIM isn't necessarily easy, and ebay modules and preamps don't always work. A model 2200 in good shape is an easier bet.
One aspect of Model 2200's you didn't speak to yet is data output. Ludlum has been making these units for a while, and over time, they have added and improved data output. The current version has a RS 232 data connection with interface software available for download on the Ludlum website. Previous versions, including the one I'm using these days had a printer connection and an analog rate signal for a recorder. It's easy to use these outputs for analysis purposes.

Jim K
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Re: FAQ - Introducing the Ludlum 2200! A perfect solution

Post by Richard Hull »

Thanks for the input Jim. I have studied the output on our older 2200s. An external setup is possible with a micro controller, but is for others to muse over. I am thinking about a speaker/clicker that should be easy to implement. If I do it, I will add the update to this FAQ.

If I have one complaint, it is the preamp in the 2200. The internal preamp, one size fits all nature and the need to set the DISRC pot for the many different detectors can be tedious, but once done it is OK. Between testing and qualifying GM tubes with the pot set almost all the way CCW and the Proportional tubes with it set real close to the noise level all the way CW, it can be tricky to the uninitiated with no scope or pulser. Still, it works OK for most apps and tubes.

The discriminator pot can be set for proportional tubes and left there provided the Threshold pot is set high (CW) for GM tubes. The preamp can just be overdriven without harm. Perhaps much ado about nothing.

Certainly, I would never tie up my 2200 as a more or less permanent neutron counter as most might do here. It is far more valuable sitting on my bench as a tester and qualifier/verifier of any radiation detection tubes that I might encounter or seek to purchase.

Oh, thanks for the kind words related to the FAQ. I spent all day Monday photographing the set up, annotating the images and assembling the FAQ post here. The long text in the FAQ I generated between 1AM and 6 AM this Tuesday morning. Went to bed around 7AM! Being retired helps in this effort.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Jon Rosenstiel
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Re: FAQ - Introducing the Ludlum 2200! A perfect solution

Post by Jon Rosenstiel »

I’ll second Jim’s comments, great FAQ, Richard. Sure wish this was written twenty-some years ago when I was a newbie and was struggling mightily to understand the difference between the discriminator and threshold pots.

JonR
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Re: FAQ - Introducing the Ludlum 2200! A perfect solution

Post by Frank Sanns »

Yep. Great little unit. The Ludlum 2200 has been my goto for over 20 years. Here is a photo of my first Fusor setup.

Everybody was NIM happy so I did try that route for a while but always came back to my pair of 2200s. They are super versatile, accurate, and last and last. I like them so much I upgraded one to the newest incantation. Still work the same but a somewhat different front panel.
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FrankFusor.jpg
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Richard Hull
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Re: FAQ - Introducing the Ludlum 2200! A perfect solution

Post by Richard Hull »

For me, FAQs are written as I see a need for them. I bought my 2200 about 6 years ago and loved the hell out of it. It is only in the last few years I have seen posts about it, but Joes recent excellent post noted in my original post above, kicked me in the butt to generate this FAQ. I guess as Frank notes, I already had mine in the form of NIM since 2000. The first 2200, I ever saw, in person, was at HEAS 2009 when Eric Stroud brought his 3He neutron detector system to calibrate it against my fusor IV. He used the 2200 to assemble his neutron counter around his moderated 3He tube. I was amazed and impressed, but as I had a nice NIM setup it passed more or less un-noticed. It took me reading one of Jim Kovalchick's posts in 2018 to get my own 2200 off E-bay.

Slow to the game on getting this FAQ out, but hopefully this FAQ might assist future would-be fusioneers while, at the same time dry up E-bay of all available Ludlum 2200s. LOL

Richard Hull
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Eric is seen with his two Neutron counters the 2200 and an old snoopy.  HEAS 2009
Eric is seen with his two Neutron counters the 2200 and an old snoopy. HEAS 2009
4000574871_34aa6a97eb_m.jpg (24.52 KiB) Viewed 4685 times
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Ludlum 2000 (near identical unit but less expensive)

Post by Dennis P Brown »

I was certainly interested in the Ludlum 2200 since I have a number of detectors (Two BF3, a He3, and Geiger Tubes.) Though I couldn't find any units currently available on e-bay but did see a few Ludlum 2000 units. These are significantly lower in cost (I got my for a bit over $200 w/shipping) but in the image of the unit it appears to have no voltage control or sensitivity control. Yet researching the unit, it indicated these were available and adjustable. So I assumed they were maybe on the back of the unit.

Long story made short: these units have those controls mounted internally but are the same controls used on the 2200 unit. Further, these units have both the original holes and the required controls have wiring that allows them to be reinstalled into those front panel holes. Maybe this was done after market and not on the original units. Still, a few more units appear available that have this issue.

So I bought one and converted it into a more standard configuration. See the supplied photo's.

A few points. I converted the C-type BNC into a standard 5 kV BNC because all my tubes either have that type or I have a coupler to mate them.) In any case, on e-Bay a C-Type to STD BNC converter is sold if anyone wants to go that route. My HV BNC required a mounting plate to cover the large hole (which I made in twenty minutes.) Easy to de-solder and access because the front panel assembly separates from the main housing and internal wiring is long enough to make this easily work.

Be aware: The control knob for the geared unit's potentiometer requires an Allen driver so small I couldn't find any to fit it. So I took my smallest driver and using a grinder adapted it to fit this ultra small bolt. Required a microscope (my vision is no longer that sharp - thanks to my thesis. :( )

All in all, appears to work almost like the 2200 unit (it is missing a threshold adjuster and range function.) Otherwise, identical but can be had for about half the price or better. I will add that later 2000 units (more modern units) certainly have these knobs back on the front panel. So, the these older units (modified?) can still be converted rather easily.

I tested it with a Geiger tube and Uranium sample and appeared to work well (400 volts.) Using a BF3 tube and 1500 volts, got one to two counts per minute. No idea if that is real or not.
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Panel as delivered (note panel plugs for HV & Disc)
Panel as delivered (note panel plugs for HV & Disc)
Inside with HV & Disc controls
Inside with HV & Disc controls
After removing controls
After removing controls
Finished unit (note new HV BNC connection)
Finished unit (note new HV BNC connection)
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Richard Hull
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Re: FAQ - Introducing the Ludlum 2200! A perfect solution

Post by Richard Hull »

Good work! Nice kludge to move the sensitivity control. Learning by doing. The only way to warrant independence. So many young folks can't even swing a hammer or change out a faucet. Too busy on their smart phones to get involved in the doing.

Most of those landing here are older and somewhat adroit via life experiences. The younger folks arriving here vary from hopeful dolts to true amateur scientists with some experience far beyond their age.

I never thought I would say this but the higher demands made to make the various inducted award levels here has drastically fallen off. Those who arrive and achieve, always know that their success is due to some struggle and they learn along the way. I know I did. No matter how good you think you are, there is always room to learn via the self-directed learning adventure in life.

In my bio here, I note that I consider myself more of a teacher in these forums, often via tough love, exhorting the weak to get strong via the doing and the reading. A good friend of similar knowledge and skills sat down with me one evening over pizza and beer. We were saddened that all the knowledge and skills we have acquired will die with us. (we are old) We took some heart in that we have instructed many others in certain areas, imparting bits and pieces of what we won by the doing and the reading. School isn't out until that first shovel of dirt.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Michael Driscoll
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Re: FAQ - Introducing the Ludlum 2200! A perfect solution

Post by Michael Driscoll »

I have a couple 2200s and a 1000.

I see on the black knob on the right hand side of the front panel there is a position marked "Ext"
I would like to know what this setting does. I tried it and it seems to make the minute counter keep sampling forever.

Also mine has an unmarked BNC on the rear panel. Does anyone know what that does?

I wrote to Ludlum with the question and they told me to download the manual in a non-answer as the word "Ext" is not mentioned in the .pdf

I have extensively searched the Internet and got no answer.

Can someone here tell me?

Thanks,
Mike Driscoll
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Re: FAQ - Introducing the Ludlum 2200! A perfect solution

Post by Rex Allers »

The models since around 2000 changed the front panel and EXT disappeared, so the manuals since then won't mention it.

I have a 1990s 2200 and a manual from that period. EXT is mentioned, says, "X0.1, X1, X10 or an EXT for manual timing". Pretty cryptic. From guess and trial it seems in EXT there is no set count time period. In EXT you can still press Count to start counting but I think it will run forever, but can be stopped with the Hold button.

I think the intent is for the user to control via the Data port on the back. I haven't tried it but I think the input pins for Count and Hold can be used to start and stop a count.

I noticed that in the newer manuals where EXT went away the data port on the back went away too. Now a RS232 port. I think that serial port can be used to start/stop too, but I don't have a newer 2200 so didn't really look at how to do that.
Rex Allers
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Re: FAQ - Introducing the Ludlum 2200! A perfect solution

Post by JoeBallantyne »

Ludlum will send you the manual for your specific iteration of the 2200 (or for ANY of their old instruments) if you send them the serial number of your unit, and ask nicely. At least that has been my experience. AFAIK they have all the old manuals for all of their instruments. The manuals for the older iterations of their instruments are simply not up on the Ludlum website for easy download.

Joe.
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