Humm
I had an interesting conversation with an old proffessor who worked with Crofton in England,
He told me they used rectified telsa coils for many years.
The trick is to use a sphere and tubes with a filament battery
inside the sphere. Sheilded the rectifing tubes don't arc over.
You tie the output of the telsa coil to the diode bank. Then tie the output of the diodes to the inside of the sphere rather like a Van de Graff. They also had a large length of pyrex pipe with home made diodes that were voltage adjusted by cranking up or down the plate for the specific voltage. They used vacuum tube filaments in large number for higher amperage.
Fusion is fun!
Larry Leins
Fusion Tech
tube rectifiers
Re: tube rectifiers
Very Interesting.... When I was in high school I tried to do that very thing... build a tesla coil and rectify the output using a series of 1B3's (the std TV Hv rectifier tube in the good ole days). Even planned to use batts for the filament drive since the 1B3's had ... 1 volt filaments.
Project was 0.5 MEV LINAC. It took me so long to build the Tesla coil, that I had time to learn about the various dangers inherent in this endeavor. I did get the coil to work.. at about the 1kW level, but I scuttled the LINAC because I couldnt afford the necessary vacuum pump. Probably saved my life.
Tesla coils seemed a bit troublesome as a well behaved HV voltage source because of the HF coupling to anything and everything. I didn't know to do the DC shielding. That sounds quite effective.....if you have the space to build large things.
Neat stuff.
Dave Cooper
Project was 0.5 MEV LINAC. It took me so long to build the Tesla coil, that I had time to learn about the various dangers inherent in this endeavor. I did get the coil to work.. at about the 1kW level, but I scuttled the LINAC because I couldnt afford the necessary vacuum pump. Probably saved my life.
Tesla coils seemed a bit troublesome as a well behaved HV voltage source because of the HF coupling to anything and everything. I didn't know to do the DC shielding. That sounds quite effective.....if you have the space to build large things.
Neat stuff.
Dave Cooper
Re: tube rectifiers & X-rays
Dave & Larry-
I still use 1B3GT's to rectify 9-kV NSTs at times. I mount the rectifier on a phenolic base with two D-cells in parallel and a knife switch. Works very well and is very durable (forgiving of high currents for short periods).
We had a former member of our group connect a HV diode (not sure what tube) to the output of his Tesla coil. The result was a real scare for him: x-ray burns on his face. All first degree burns. So, shielding is definitely needed. I have a reference table that shows a 1-mm lead sheet will stop x-rays up to 75 kV (Robertson, 1941). I use 1/16" (minimum) to be on the safe side.
Regards,
TIM
I still use 1B3GT's to rectify 9-kV NSTs at times. I mount the rectifier on a phenolic base with two D-cells in parallel and a knife switch. Works very well and is very durable (forgiving of high currents for short periods).
We had a former member of our group connect a HV diode (not sure what tube) to the output of his Tesla coil. The result was a real scare for him: x-ray burns on his face. All first degree burns. So, shielding is definitely needed. I have a reference table that shows a 1-mm lead sheet will stop x-rays up to 75 kV (Robertson, 1941). I use 1/16" (minimum) to be on the safe side.
Regards,
TIM
Re: tube rectifiers & X-rays
Hi Dave:
My first serious xray was a high school project built from a tv flyback... thank God, I had scientifically trained folks for neighbors.
I ran with the nerd pack in Dallas.
(My best friends girlfriend's father was the resident Physcian in charge of Radiology and Nuclear Medicine at Dallas Memorial.)
Rather than panic they gave good advice and I followed it like a good boy. I lived to tell the tale.
At the science fair I took only pictures with me with a detailed write up.
Hi Tim:
Sounds like the input I got from the old guy. The xrays are very mean and unfiltered.... lots of burning rays. (>20 rem) I plan to use 2x2's (12.5 kv) in series for my rectifiers. Why?
I had them. 1B3's were my second choice. I worked at a place
that used 440 volt main lines in a telsa setup to run an xray
testing shop. It ran at 1 mev. They used it to xray steam and jet turbines and large parts for metalurgical analysis. Lots o Concrete. The control room was 200 yds from the work.
When I get to the testing point, Don't think I'm hanging out.
This stuff is really serious fun! Rectifing is a very serious thing to do...bad enough at 40 kv but life threatening at 200-500 kv.
I been planning this move for a long time now but safety has not gone out the window. Yes I have a full acre of space to play in.
I've been a busy bee. My shielded facility needs just a few weeks of dry weather so I can finish pouring the walls. Then comes the rfi shield welding inside the building. Lead is your friend!
Fusion is fun!
Larry Leins
Fusion Tech
My first serious xray was a high school project built from a tv flyback... thank God, I had scientifically trained folks for neighbors.
I ran with the nerd pack in Dallas.
(My best friends girlfriend's father was the resident Physcian in charge of Radiology and Nuclear Medicine at Dallas Memorial.)
Rather than panic they gave good advice and I followed it like a good boy. I lived to tell the tale.
At the science fair I took only pictures with me with a detailed write up.
Hi Tim:
Sounds like the input I got from the old guy. The xrays are very mean and unfiltered.... lots of burning rays. (>20 rem) I plan to use 2x2's (12.5 kv) in series for my rectifiers. Why?
I had them. 1B3's were my second choice. I worked at a place
that used 440 volt main lines in a telsa setup to run an xray
testing shop. It ran at 1 mev. They used it to xray steam and jet turbines and large parts for metalurgical analysis. Lots o Concrete. The control room was 200 yds from the work.
When I get to the testing point, Don't think I'm hanging out.
This stuff is really serious fun! Rectifing is a very serious thing to do...bad enough at 40 kv but life threatening at 200-500 kv.
I been planning this move for a long time now but safety has not gone out the window. Yes I have a full acre of space to play in.
I've been a busy bee. My shielded facility needs just a few weeks of dry weather so I can finish pouring the walls. Then comes the rfi shield welding inside the building. Lead is your friend!
Fusion is fun!
Larry Leins
Fusion Tech
Re: tube rectifiers & X-rays
Larry,
Yeah, sounds like you've been keeping busy. I did a discharge tube demo when Richard came to visit not too long ago. I was running the tube at p=approx. 15-20 mTorr with a 3.5 kV DC supply and we detected some mild x-radiation from it. I think we were both a little surprised, since the potential was so low, relatively speaking. Yes, "lead is good."
Regards,
TIM
Yeah, sounds like you've been keeping busy. I did a discharge tube demo when Richard came to visit not too long ago. I was running the tube at p=approx. 15-20 mTorr with a 3.5 kV DC supply and we detected some mild x-radiation from it. I think we were both a little surprised, since the potential was so low, relatively speaking. Yes, "lead is good."
Regards,
TIM
Re: tube rectifiers & X-rays
I did post this caution elsewhere in one of the discussion threads... I have measured Xrays as low as 1500 to 1600 volts using the Monitor 4 radiation detector. It is a simple G-M device, with and end on detector with a ~6 um thick mica window.
At these potentials shielding is accomplished with a piece of paper, alum foil or what not.. Travel distance in air is only a fraction of an inch. But it goes up rapidly with voltage .At 3-4 kv Xrays will penetrate Alum. foils and paper.... Above about 6 KeV you should be thinking of shielding.
Dave Cooper
At these potentials shielding is accomplished with a piece of paper, alum foil or what not.. Travel distance in air is only a fraction of an inch. But it goes up rapidly with voltage .At 3-4 kv Xrays will penetrate Alum. foils and paper.... Above about 6 KeV you should be thinking of shielding.
Dave Cooper