FAQ - Roll your own preamp (Richard Hester design)

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Richard Hull
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FAQ - Roll your own preamp (Richard Hester design)

Post by Richard Hull » Sat Oct 17, 2020 5:57 am

Long lost images from the massive losses of images and files last year still haunts us.
Richard Hester was a brilliant star here in the 2004-2010 time frame. His many useful circuits are now lost.
I have found one of a nice little charge sensitive preamp he designed which I had printed out.
I have scanned it and now post it here as part of a FAQ that I hope to improve upon with testing and more input as time goes by. Unlike other FAQs, I welcome input as long as it is constructive and rigidly to the point. I hope this is be a monument to Richard's work here as it expands and grows within this FAQ.

You can catchup on the original post where the written thread begins in 2010 at.....

viewtopic.php?f=13&t=6092&p=34536&hilit ... ive#p34536

Alas this is a high noise, yet good content running post for 6 Pages!!!!! Whew All great subsequent posted images by Richard are apparently lost forever. (sob) Sadly, this post and it superb effort may have been his swan song. (among his last)

For Nembies
A charge sensitive pre-amp is needed for neutron counter tubes of the 3He and BF3 proportional type. They are very hard to come by, normally, and if you have some electronic skills, know how to properly shield "front end" preamps in an enclosed metal box with short input cables and mount the few front end component in mid air, then this might be for you. All components are still available.

update:

I have altered the original file to include Richards total pre-amp and post amp. I have altered his original a bit for HV bias components with proportional neutron tubes. His original was for a PMT


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HesterCSA_POST_SHAP-UPDT.gif
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Re: FAQ - Roll your own preamp (Richard Hester design)

Post by Cai Arcos » Sat Oct 17, 2020 10:01 am

Richard:

I distinctly remember the "Pathetically Simple Charge Sensitive Amplifier". The simplest CSA I've ever seen! I printed it a couple years back but after an hour of searching I'm afraid It is lost to the sand of times...
Searching for it in Google, I found the diagram in Fred's fusor Page (http://www.fusor.eu/monitors.html). It references the original thread where the image is now lost. However, I remember that the image had a brief but comprehensive explanation of the workings of the circuit which I found most helpful.

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Re: FAQ - Roll your own preamp (Richard Hester design)

Post by Jon Rosenstiel » Sat Oct 17, 2020 5:45 pm

Missing images in Richard Hester thread have been restored. (Also restored schematic for the "Pathetically Simple Charge Sensitive Amplifier")

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Re: FAQ - Roll your own preamp (Richard Hester design)

Post by Richard Hull » Sat Oct 17, 2020 5:52 pm

Wow! Thank you Jon!!

I will still wring out this simple circuit. I have all the parts.

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

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Re: FAQ - Roll your own preamp (Richard Hester design)

Post by Jon Rosenstiel » Sat Oct 17, 2020 8:10 pm

Glad I could help out. I’m going to attempt to restore all of Richard Hester’s missing images/schematics/files.

Jon R
I like old-timey heavy electronics that you don't have to hold down
with one hand while pushing the on/off button with the other.

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Re: FAQ - Roll your own preamp (Richard Hester design)

Post by Richard Hull » Sun Oct 18, 2020 3:28 am

I applaud your willing to take the project on, Jon. Best of luck in the effort and hope you are successful to the fullest. I hope that Richard is doing well and prospering where ever he is.

I spent the end of the day trying to hand-hew end plates for a small re-purposed box for the pre-amp above. I hope I can squeeze the components in this little box.

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

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Re: FAQ - Roll your own preamp (Richard Hester design)

Post by Joe Gayo » Mon Oct 19, 2020 5:23 am

I converted Richard Hester's design to a PCB with a few modifications (the main one being a high voltage bias connection with a 2nd order RC filter). I'm building a number of these boards late next week. I'm willing to sell completed and tested boards or just the bare boards. Is anyone interested?

I have a picture of the board but it doesn't seem to allow me to add an attachment?

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Re: FAQ - Roll your own preamp (Richard Hester design)

Post by Richard Hull » Mon Oct 19, 2020 7:10 pm

Joe great work. I would be interested in a bare board or two. Post prices both ways for folks in two places. 1. Here or in posted addition to the original post and 2. in the trading post.

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

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Re: FAQ - Roll your own preamp (Richard Hester design)

Post by Richard Hull » Mon Oct 19, 2020 8:48 pm

Please refer to the first posting here as I have updated the diagram using Richards last CSA postamp circuit. (different from his first pass in his original posting)
I have added the full diagram for using the much more sensitive 3H3 or BF3 proportional tubes. His original circuit as for use with PMTs. The bias circuit is critical.

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

Joe Gayo
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Re: FAQ - Roll your own preamp (Richard Hester design)

Post by Joe Gayo » Mon Oct 19, 2020 9:20 pm

Some thoughts:
Before making my iteration I looked through all of Richard Hester's designs and made changes -
- I think the anode connection of D6 is less than optimal since the feedback bandwidth is already pretty low and the performance degrades at higher count rates (I increased the bandwidth in my iteration)
- The FET change seems an unnecessary degradation in performance as this FET is sourced from process 51 and is meant for switching applications and has a low transconductance
- The bias filter should be 2nd order or more

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