7 years

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Jeremy Sims
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Joined: Mon Jan 19, 2015 4:54 pm
Real name: Jeremy Sims
Location: Southern Ohio

7 years

Post by Jeremy Sims »

Hello everyone, it has been a long time, I remember reading Mr. Hull's post when I first started that said something along the lines of "Life happens" and it surely did. Changed jobs twice, moved into an apartment that requires me to work 40 hours, depression, actual years went by with the frame of the fusor rusting outside in the mud at my old cabin. There were various times I would work on it for a few days then lose interest and put it aside again, where it would sit for months. Last year I pulled the old frame from its grave and started the process of cleaning it up. Things progressed slowly from there, I now have a large collection of non-working vacuum pumps. Today I finally switched on the diffusion pump I bought 7 years ago and held my breath. It takes 15 minutes for it to warm up and during that time the gauges slowly climbed back up to around 30 microns after they had reached 4 microns on just the roughing pump. Then they dropped steadily back down until the main chamber had reached 0.1 mTorr. By that time the coolant water temperature had reached 86 degrees which is already 6 above allowable so I switched the diffusion off. So I will be addressing that issue with perhaps a blower fan on the radiator instead of computer fans, however the air temp in the garage was already 80 so I may have to run something else. The cold cap itself is supposed to be cooled with liquid nitrogen but I just used ice water for now ran though a Breg polar care cube.
A few other things of note: the main chamber itself has remained sealed for almost three years after I put in the grid. It takes 10 minutes at most to pump to 4 microns. The diffusion pump with the oil still in it sat for probably 5 years.
Current Specs:
Roughing pump: Leybold Trivac D16B
Diffusion pump: Varian HS-2
Cold cap
Foreline gauge: KJL-6000 thermocouple
Main chamber: 4.625 CF cross with the grid located in the downward pipe. The pipe is jacketed to allow for cooling.
Main chamber gauge: 300 series Convection KJL

At the moment, I only need a few more items to be purchased in the coming months.
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Dennis P Brown
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Location: Glen Arm, MD

Re: 7 years

Post by Dennis P Brown »

Congratulations on getting the system up and running; and it appears to be in excellent shape. Your two stage pumps and diffusion pump are each working very well. While a cold trap isn't necessary the baffles are essential. Using ice water might be more trouble than its worth rather then just cooling water from a sink or other faucet.

My DP oil is over ten years old and still works great so if one seal's it off, that stuff seems to really last.

Nice and professional set up. Do you have a power supply yet or are those gauges to the right your power supply? If so, what is it - i.e. home made and if so, the type? Will you generate deuterium or plan on adding a lecture bottle? Does your main chamber have a gate/butterfly valve to control the vacuum exhaust rate?

I have an identical DP and those two closed off ports are used as a coolant line into the hot oil chamber to cool the DP oil after shut down. I found that this allowed me to open the DP within 10 minutes after full operation - a useful feature when one is adjusting that area of the pump. Certainly not important but easy to install.
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Richard Hull
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Re: 7 years

Post by Richard Hull »

Typically, the mechanical punp will go into the microns range and then the diff pump, as the oil rises to 70-90 deg C will blow out any water vapor in the oil towards the mechanical pump. This will cause a pressure rise in the system until the mechanical pump passes the water vapor out of the system. At this point, the pressure will really plunge as the oil hits 120deg C+. (water all boiled off and exhausted)

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.
Jeremy Sims
Posts: 28
Joined: Mon Jan 19, 2015 4:54 pm
Real name: Jeremy Sims
Location: Southern Ohio

Re: 7 years

Post by Jeremy Sims »

Thank you Dennis! Right now my power supply is a dental x-ray transformer that has been sitting in its tank for awhile. I have done one plasma run on a previous build in 2019. I will be posting its build pictures a bit later. The gauges on the right are not completely wired in yet. The main valve to chamber is in the 90 elbow right above the cold trap. Maybe a bit hard to tell because it is operated by a thumb ratchet.
I had been wondering whether to incorporate the cooling line to the cold trap at all but that cooling device was a nice find for $4 so I figured try it for awhile. So at the moment there are two coolant lines. The one for the cold trap is pumped ice water. The other, which feeds the tube wrapped around the diffusion, is just a normal 12v water pump that sends the water through a radiator designed for computers. I do have a full lecture bottle and a needle valve. One of the last items I need is the regulator.
Attachments
Plasma run from 2019. @20 microns
Plasma run from 2019. @20 microns
plasma run from 2019
plasma run from 2019
main valve
main valve
Jeremy Sims
Posts: 28
Joined: Mon Jan 19, 2015 4:54 pm
Real name: Jeremy Sims
Location: Southern Ohio

Re: 7 years

Post by Jeremy Sims »

I did a plasma run today to try to test voltage metering. I built the system for an analog meter exactly as described in the FAQ using an string of Megaohm resistors. But first I wanted to hook a multimeter to the end of the resistor string. The multimeter is a Klein Tools Autoranging. The negative lead was originally hooked to the end of the string and the positive to ground. Upon powering up the main switch the meter immediately jumped to @-240mv. The variac has its own switch and had not been powered on. Switching on the variac had no effect until I moved the dial slightly. Then the multimeter dropped to zero and slowly climbed with moving the variac in the range of -20 to -50mv. During this time I used a raspberry pi with camera to observe the plasma at 15-25 microns. The camera did freeze up at on point but was fine after restarting pi. As soon as I cut power back down to zero on the variac the mm would again read in the -200 to -400mv range. I then switched the lead hookup on multimeter (I don't know why I hooked it backwards to begin with.) Did another run. The system holds vacuum well enough for me to shut the roughing pump off for short periods. So I could hear a little bit of arcing at higher voltages/ higher pressure. Plasma looked good but then I noticed the mm was now reading volts. I turned the variac it changed voltage. I switched mm to AC and it corresponded to the volts on variac. I was still attached to the pos. at end of resistor string.. negative to ground.. At this point I was worried I had shorted the x-ray transformer internally to ground. I first did a resistance test across its ground to its variac hookup points. Did not read any shorts. With hv transformer unhooked I turned the variac and the mm again registered the changing voltage. Even after shutting the variac completely off I was still getting almost 10v AC. I slowly started disconnecting things till the pi was the only thing left running and I was reading 5v. I have no idea what is going on...

Other pertinent info: The whole system has its own dedicated switched 20amp outlet, but it is on house ground.
The hv is a 100ma dental x-ray with 60k ballast. No current metering yet.
Sorry I can't not post more pictures at the moment slow connection.

Any ideas are much appreciated
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Richard Hull
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Re: 7 years

Post by Richard Hull »

Variacs rarely go to zero volts unless the use adjusts the detent stop where the brush is fully on the usual thick zero turn tab. Often, it is on the pad and the the first turn. Some small voltage is normal.

I have no idea of your resistor string value and how it is hooked up. What are the values? did you figure on the meter's impedance? give us a diagram or schematic of your rough hookup with values. Millivolt values or readings on a DVM are of no value in high voltage measurement schemes. what would you expect in volts on your DVM at 20kv from the supply?

Are all the voltage you are reporting variac voltages or high voltages from your string? Lots here we have no clue about. Values and schematic with images of your resistor string would help.

DVM's are real easy to destroy in a mis-wired or mis-calculated string.

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.
Jeremy Sims
Posts: 28
Joined: Mon Jan 19, 2015 4:54 pm
Real name: Jeremy Sims
Location: Southern Ohio

Re: 7 years

Post by Jeremy Sims »

I went to draw up schematics and didn't even get the resistor string drawn before I realized the many things I did wrong this morning. Namely not connecting the lv end of the string to ground through the 1 Meg/ne2 as in the faq. The resistor string is a 600meg followed by 4 100meg. I connected that end to ground and everything cleared up. Thanks!
Jeremy Sims
Posts: 28
Joined: Mon Jan 19, 2015 4:54 pm
Real name: Jeremy Sims
Location: Southern Ohio

Re: 7 years

Post by Jeremy Sims »

With both voltage and current gauges finally wired up, time to post some pics. Eventually I will also have everything running through an arduino to collect data and a better camera system than the pi's. The current is being fed through the 100 microamp gauge from the case ground of the transformer. I did not see a good way to do this from the shell as it is sitting on a metal base which is then bolted to the metal frame and so on. The gauge is shunted with a 5.6 ohm 2 watt resistor as the resistance across the gauge was 5000 ohm. So 1/1 scale micro/milli. The kv gauge above the amp gauge is not wired in yet, waiting on longer bnc. Kilovolt gauge beside chamber is connected to 1 X 10e9 meg string I also popped open the transformer case to correct the arcing. My original A/C hookup points were too close together and the oil was still too low. I moved the hookups and then put a bead of silicone around the top cover to prevent leakage after I filled to top. The hv output terminal on top also has an oil cup.
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Jeremy Sims
Posts: 28
Joined: Mon Jan 19, 2015 4:54 pm
Real name: Jeremy Sims
Location: Southern Ohio

Re: 7 years

Post by Jeremy Sims »

Small run to test current gauge, 4 minutes. About 15milliamp peak with pressure peak at 35 micron.
Attachments
Beginning plasma 25 microns
Beginning plasma 25 microns
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about 8 milliamp
about 8 milliamp
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15 milliamp peak
15 milliamp peak
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Richard Hull
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Re: 7 years

Post by Richard Hull »

Nice looking setup and plenty of photos so all can see you work in sections. This is how we share. A picture is often worth a thousand words. Thanks

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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Dennis P Brown
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Re: 7 years

Post by Dennis P Brown »

Agree, both nice set up approach and great pics. I noticed the transformer and that it might be one that exceeds 40kV. As such, has it been soaked in oil (maybe under vacuum first)? I ask this because at very high voltages those windings can short out destroying the x-former.
Jeremy Sims
Posts: 28
Joined: Mon Jan 19, 2015 4:54 pm
Real name: Jeremy Sims
Location: Southern Ohio

Re: 7 years

Post by Jeremy Sims »

It's been under oil for at least 5 years now. That 1 picture without oil was taken when I first put the case together. Originally I had put that kf fitting in to try and draw out the air but I didn't follow through with that. I've had it up to about 25kv so far. If I remember right it was rated 100kv, I may be wrong on that.
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