Visit to Jon Rosenstiel's

Post by **Frank Sanns** » Thu Jan 16, 2020 11:20 pm

Today I had the pleasure again of visiting Jon Rosenstiel. It was not a formal West Coast HEAS like we have done in the past but rather an informal visit.

Here is a shot of Jon at his new cube fusor and some close ups. He was gracious enough to remove the lead shielding so I could take a peak. Really top notch components and machining! Absolutely first rate all of the way!

Also as usual, the visit also led to great discussions. Many aspects of the important details and parameters were pondered. I am going to start a separate technical thread on what I know and what Jon knows on such matters. I am in the midst of some other business (which will also be shared in the very near future here) but it will be a few days before I can put my thoughts down on that.

Post by **Richard Hull** » Fri Jan 17, 2020 12:16 am

Thanks Frank for the photos. We don't get enough personal images of others at their fusor's. It is nice to see Jon's friendly face again. He has been to a number of HEAS events in the past and is one of the best among us "old boys. I note Jon has a Keithley electrometer on his shelf. (Probably a 610 - one of their best ever). Good man! It teaches just how electrical the real world is and how vast exchanges of electric currents occur at every instant among all objects in motion.

I am envious of his machining abilities. A true machinist. I, on the other hand, tend to use the four lathes and milling machine here to whittle metal into more or less what I think is O.K. I like his hand hewn table of "heat stinks" for the cubed fusor. Cool beans...

God, how I hate 4 jaw independent chucks and will do anything to escape having to use them. I am the eccentric and not my machinings. Naturally, I have successfully used them in the past, but I look at it as a great way to burn off a lot of life setting up the work. Jon probably made a living off the use of 4 jaw independents.

Jon, Is that a Hornyak button or BC720 neutron detector in the copper tube or foil covered assembly?? They are no good for low neutron numbers, but can be just dandy above 50k n/s, keeping the counts relatively low so no counts are missed, especially at the mega mark and above.

Richard Hull

ian_krase · Post by **ian_krase** » Fri Jan 17, 2020 3:27 am

I'm curious where the high vacuum pump is.

Jim Kovalchick · Post by **Jim Kovalchick** » Fri Jan 17, 2020 6:17 am

Ian, trace it out from his chamber to the vacuum valve. Looks like a turbo to me.

I'm interested in what he's trying to detect with the pmt.

Jim K

Post by **Frank Sanns** » Fri Jan 17, 2020 10:54 am

The PMT was the way all of us detected neurons back at the start of these forums. Inside is a Hornyak button or BC720.

He is using that on a sled to do inverse square measurement to determine where the neutrons were being formed and if they were directional. This came from a previous post of mine in another thread. Jon of course ran with it and built the setup and has some measurements.

Jim Kovalchick · Post by **Jim Kovalchick** » Fri Jan 17, 2020 11:14 am

Thanks Frank. I figured he was looking at either proton recoil or xrays/gammas because I dont see a moderator.

Jon Rosenstiel · Post by **Jon Rosenstiel** » Fri Jan 17, 2020 1:18 pm

One day it’s a fusor, the next a pumping station. On the pumps (Leybold D16A backing and Pfeiffer TPH-190 turbo) is my Ortec hpGe detector getting its annual bump and bake. Wrapped up in foil is an aluminum rod in contact with the detector’s cooling rod. Heat tape wrapped around the upper portion of the Al rod heats the detector’s germanium crystal to around 100 C. Purpose is to drive off and pump out any contaminates that may have settled on the crystal’s surface. The DMM on the left is reading the resistance of the detector’s internal temperature sensor. (694 ohms = 101 C) Thermocouple thermometer on the right indicates temperature of the aluminum rod. Variac behind the TC thermometer controls power to the heat tape. Pressure at the time this image was taken was 1.1E-06 Torr. After cooldown the pressure will drop nearly an order of magnitude.
Jon Rosenstiel

Post by **Richard Hull** » Fri Jan 17, 2020 1:42 pm

Wow! I wish I had an HPGe detector! Bill Kolb and I drool over what Jon can do with that system... Needle points for isotopic lines instead of our smooth sine wave humps found in our Na:Tl gamma specs. This is the cat's pajamas of gamma spec work. I liken it to the 3He detector for neutrons. A world of difference in the hunt for gamma isotopes just as the 3He is for sniffing out neutrons.

The need for liquid nitrogen makes for a tedious startup, but it is more than worth it when there is real delicate gamma sniffing is to be done, as there is no substitute for this work with an HPGe system.

As regards to Jon's directional work with the Scintillation detector, I still have the 2.5 Inch formal BC 720 scintillator I bought from Bircron in 1999 ($300), and the 5 inch BC 720 I bought in 2002 ($595.00). The 2.5" is mounted with scintillator ready to rock and roll in my lab. I have 4 Hamamatsu 5" mint PMTs in original cartons (hamfest buys back in 2005). I might have to assemble a 5 inch unit to finally have the nearly $600 spent way back then on the huge BC 720 pay off...finally. I'll probably monkey with the ready 2.5" unit first. I haven't used it since 2001. The reason is a warranted 0.5% efficiency for the BC720 scintillator. Worthless of low neutron numbers....!

In the beginning I think I unloaded about $15,000 over the first 5 years of Fusor work! I was a working electronics engineer at that time with a fully paid for home, no car loan and blessedly, no children and my wife was the treasurer of a local company....Money was never an issue for us. We planned our life like a rigid, immutable economic road map.

To answer Jim's query.......No need for a moderator with the BC-720 it is a block of hydrogenous plastic with rings of scintillator powder embedded like a target. Its gross inefficiency is due to knock-off protons failing to travel far in the plastic and relies on the rare occurrence of a proton slamming onto the scintillation powder creating a flash for the PMT. The up side is total gamma immunity. I'll post a photo of the big BC-720 soon. Gotta' dig it out of my box of scintillation plastics. Well, I discovered I had the smaller BC-720 out of the detection system and probably have Tom Dressel's hornyak button in the detection system. The real BC-720 smaller 2.25" item I found in the big box of scintillation plastic.... check out the photos.

Back then fusor III would barely tickle the smaller BC 720 it with 50k n/s and then came the glorious 3He tubes to the rescue. I even purchased a monster BF3 tube that never got used as the 3He tube was where the counting was to be found as bare wisps of neutrons caused real useful counts in this super detector. Now, perhaps I might take a giant leap backward into inefficient, yet wonderfully directional, neutron detection.

I suppose much of this original work and discussion related to hornyak and BC 720 scintillation detection is to be found on the Intranets section of this effort if someone is stimulated enough to search it out.

Nice warm glow of the ionization gauge there in the picture, Jon. Never used one in spite of having 3 naked ion gauge tubes on conflats, 2 glass tubes like yours and 4 Varian controllers for them. ( all at surplus of course...) I stumbled onto 2 heated 100 millitorr Baratrons for $10 each at a New York Teslathon back in 2003. With 4 useful decades and total gas specific immunity, they were a wonderful avoidance of the complexity of the ion gauge system.... Or any other gauge system for that matter in fusor work)

Richard Hull