CHM 56 Russian tube
Posted: Sun Jan 15, 2023 12:05 pm
Russian tubes have been discussed quite a bit on this forum, but I'm sure there is still much to learn about them. Here is another bit of experience I thought I would share.
In the last year or so I purchased a CHM 56 tube on ebay for around 100 dollars. It was advertised as a high sensitivity He3 tube that operates in the proportional mode. Ever the sucker for a good neutron tube I thought I would try it.
I am happy to report that I am very satisfied with the tube. It works pretty seamlessly with my Ludlum 2200 even without a preamp. I simply added a resistor and MHV fitting and plugged it in. I buried it in a cardboard tube filled with ground up black HDPE plastic and put it close to my fusor. It seems to like 1400 volts. I initially set the threshold on the Ludlum until it only gave a few counts per minute. During initial exposure to neutrons I found that it counted too many xrays and adjusted the threshold upward until there was clear drop off of detector counts when I pulled it out of the moderator. At this setting I am still getting a few counts a minute background. So I think I found a sweet spot.
Sensitivity wise, I'm very happy so far. Today during a fusor run, it clearly showed fusion in progress at 30 kV and only a couple milliamps when my PNC-1 was barely twitching. Today while I ran my fusor at 53 kV and 15 mA, my PNC-1 very close to the chamber read 3000 cpm. The CHM 56 read around 12,000 cpm.
The CHM 56 is not a long tube. This makes it ideal for a compact fusor system.
This link is to a quick video show my tube and Ludlum arrangement this morning at 45 kV, 13 mA, and about 7000 cpm.
https://youtube.com/shorts/dEAsMKBZqs0?feature=share
Jim K
In the last year or so I purchased a CHM 56 tube on ebay for around 100 dollars. It was advertised as a high sensitivity He3 tube that operates in the proportional mode. Ever the sucker for a good neutron tube I thought I would try it.
I am happy to report that I am very satisfied with the tube. It works pretty seamlessly with my Ludlum 2200 even without a preamp. I simply added a resistor and MHV fitting and plugged it in. I buried it in a cardboard tube filled with ground up black HDPE plastic and put it close to my fusor. It seems to like 1400 volts. I initially set the threshold on the Ludlum until it only gave a few counts per minute. During initial exposure to neutrons I found that it counted too many xrays and adjusted the threshold upward until there was clear drop off of detector counts when I pulled it out of the moderator. At this setting I am still getting a few counts a minute background. So I think I found a sweet spot.
Sensitivity wise, I'm very happy so far. Today during a fusor run, it clearly showed fusion in progress at 30 kV and only a couple milliamps when my PNC-1 was barely twitching. Today while I ran my fusor at 53 kV and 15 mA, my PNC-1 very close to the chamber read 3000 cpm. The CHM 56 read around 12,000 cpm.
The CHM 56 is not a long tube. This makes it ideal for a compact fusor system.
This link is to a quick video show my tube and Ludlum arrangement this morning at 45 kV, 13 mA, and about 7000 cpm.
https://youtube.com/shorts/dEAsMKBZqs0?feature=share
Jim K