Ryan's Fusor v1 Progress

Current images of fusor efforts, components, etc. Try to continuously update from your name, a current photo using edit function. Title post with your name once only. Change image and text as needed. See first posting for details.
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Ryan Copeland
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Ryan's Fusor v1 Progress

Post by Ryan Copeland »

Hi all,

It has been a while since my last update and I have made some significant progress.

I was able to snag a working Varian Turbo V-250 MacroTorr off of eBay a while ago. I did some very basic cleaning of the flange and covered it while I figured out the controller situation. I ended up finding a working controller and I just completed the first test with the turbo pump. The backing pump is a generic HVAC dual-stage rotary vane pump (not permanent) that I attached an oil trap to. The gauges are IntstruTech Worker Bees (Convection Gauges) and they bottom out at about 1e-4 Torr. I also have a cold-cathode high-vacuum gauge from the same company that I have not tested yet. One convection gauge was placed near the backing pump and the other was connected to the opening of the turbo. I wanted to see if the turbo and controller actually worked and if there were any weird noises or temperature problems. As far as I can tell, there were no weird noises (except for the controller powering up), and the turbo spun up to about 28 krpm (rated to 57 krpm) on Low Speed Mode. At this point, my convection gauge bottomed out, which was a success for me.

Initial (messy) setup for the first test of the turbo and controller.
Initial (messy) setup for the first test of the turbo and controller.

The vacuum gauge panel during the first test of the turbo. The middle number is the rough side and the bottom number is the turbo side. These convection gauges read zero once below 1e-4 Torr.
The vacuum gauge panel during the first test of the turbo. The middle number is the rough side and the bottom number is the turbo side. These convection gauges read zero once below 1e-4 Torr.

I have also created a 3D model of what I am working towards. This model is not finished and is missing several parts particularly in the rack mount. It also does not include any of the radiation shielding that I am adding on. The front viewport will have a USB camera and will be surrounded by lead sheets and will have a 1 inch lead brick right behind the camera. More lead sheeting will be placed between the operator station and the chamber. I also have a good scintillation detector (tested with low-energy X-rays) to check for radiation leakage.

Rough 3D model of the planned build. The model is missing several things, including the added lead shielding.
Rough 3D model of the planned build. The model is missing several things, including the added lead shielding.

I have gotten all the pieces in the model and have just started assembly of the chamber (a CF 4.5" 4-way cross) by attaching the 30kV HV feedthrough to it, including a rudimentary grid.

Start of chamber assembly with the main CF 4.5" 4-way cross and the 30kV HV feedthrough.
Start of chamber assembly with the main CF 4.5" 4-way cross and the 30kV HV feedthrough.

In terms of neutron detection, I got my hands on an old Eberline PNC-4 detector with the detector tube. The unit as a whole does not work, but I pulled the tube and attached it to my newly acquired Ludlum 2200. I followed Richard Hull's guide to setting it up with the tube and I think it is working. I'm getting about 1.5 cpm over a 10 minute span with the detector in HDPE. I can't be sure until I start doing fusion though.

Neutron detection tube from an Eberline PNC-4 on top of its included moderator block.
Neutron detection tube from an Eberline PNC-4 on top of its included moderator block.

And finally, I constructed the resistor chain described in Richard Hull's guide for easy HV measurement, using 10 100 Mohm 1/2 Watt resistors. I placed them in a 3D printed jig inside of a PVC pipe and filled it with mineral oil. I tested it and it works perfectly.

I am now working on chamber assembly and getting experience with the turbo. I also poured my own custom lead shielding and I am getting better at making more complex shapes that I will use for the fusor window and camera.
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Richard Hull
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Re: Ryan's Fusor v1 Progress

Post by Richard Hull »

Great work in assembly and work arounds on resistor chain to make a good HV meter arrangement. It looks like you will soon be in the business of doing fusion. Thanks for the visual update. These are much appreciated and serve to inspire and instruct others.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Ryan Copeland
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Re: Ryan's Fusor v1 Progress

Post by Ryan Copeland »

Chamber Success!

I have just completed the assembly of the chamber and frame after several long nights. I rearranged several components on the rough vacuum side to make things more accessible. I hooked up the turbo (Varian Turbo V-250) and roughing pump to give it a test. I was very happy with the results.

The rough pumping speed is a bit low as it is just an HVAC vacuum pump, but as soon as the turbo turns on, the pressure drops very quickly. I was also finally able to test my ion gauge, which is an InstruTech CCM500 Hornet cold cathode gauge. It powers up and seems to read out well. After about five minutes with the turbo running, the chamber reached a pressure of 1.01e-5 Torr. I think I could have gone a bit lower if left for longer. I was initially worried about the quickly rising pressure when the chamber was sealed from the turbo, but I think it was mostly due to water vapor/outgassing as it slowed after a few minutes. I have not yet done a bakeout, but I will look into getting the hardware to do it. After an hour of the chamber being completely sealed from all pumps, the pressure rose to ~2.9e-4 Torr. I'm fairly certain I have a small leak, but I am very happy that I do not have an uncontrollable leak that I have to hunt down.

I am going to redesign part of the rough vacuum side to include my second convection gauge. I also used a Conflat blank in the front just for testing, but I will soon replace this with the swagelok adapter for gas injection. The only thing I am worried about is that my grid and feedthrough stalk seem to be sagging a bit, but I will see if there is any plasma hotspots or anything else when I hook up the HV.

Overview of the system (don't mind the rat nest of cables). I am still working on the front panel of the rack to mount the turbo controller and the voltage controls.
Overview of the system (don't mind the rat nest of cables). I am still working on the front panel of the rack to mount the turbo controller and the voltage controls.


Closer view of the chamber and turbo pump. The yellow box on the right is the ion gauge. The turbo pump is suspended by the flange and is not touching the table.
Closer view of the chamber and turbo pump. The yellow box on the right is the ion gauge. The turbo pump is suspended by the flange and is not touching the table.


Lowest pressure I got during a quick test. The top number is the ion gauge in the chamber and the middle number is the convection gauge on the foreline/turbo exhaust.
Lowest pressure I got during a quick test. The top number is the ion gauge in the chamber and the middle number is the convection gauge on the foreline/turbo exhaust.


The pressure in the chamber after about an hour of being sealed from all pumps. (The convection gauge is also sealed in the kf flange section and the rough pump is brought to atmospheric pressure).
The pressure in the chamber after about an hour of being sealed from all pumps. (The convection gauge is also sealed in the kf flange section and the rough pump is brought to atmospheric pressure).


This is my first attempt at assembling a Conflat system and I am thrilled with the results so far!
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Richard Hull
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Re: Ryan's Fusor v1 Progress

Post by Richard Hull »

Conflat is the way to go beyond the Turbo pump. I like the fact that you worked to make things more accessible in your vacuum chain. This makes things neat and easy to correct or change out components for both repairs and upgrades. Good methodical work. This shows good deliberation and planning.

Your reports and images are appreciated by all, I am sure.

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Ryan Copeland
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Re: Ryan's Fusor v1 Progress

Post by Ryan Copeland »

Thank you very much Richard. The way I have been doing things is to download 3D parts from Kurt Lesker and place them into my CAD drawing so I can mess with the configuration until it is something I think would work the best.

This is the latest CAD model I have of the system.

Updated CAD model of the Fusor v1. It does not include radiation shielding as it covers up several important parts for the overview picture.
Updated CAD model of the Fusor v1. It does not include radiation shielding as it covers up several important parts for the overview picture.

I plan on adding a kf25 ball valve near the rough connection to the chamber in order to have convection gauge measurements of both the chamber and rough pump/turbo exhaust side during the pressure range where I cannot turn on the ion gauge yet. When the ion gauge can be turned on, I can close the left most Conflat valve so there are no kf flanges exposed to the central Conflat chamber, which I hope will reduce the leak rate and give me a better ultimate pressure.

Now that I plan to have six valves, I thought I should include a labeled image.

Labeled valves for the Fusor v1. I'm not sure if it is following the convention, but all except one are labeled as [where the air is coming from] to [where it is going].
Labeled valves for the Fusor v1. I'm not sure if it is following the convention, but all except one are labeled as [where the air is coming from] to [where it is going].


For anyone interested, this is a simplified diagram of the system plumbing.
For anyone interested, this is a simplified diagram of the system plumbing.

I have the system isolation valve so I can re-pressurize the rough pump and connecting bellows hose to atmosphere to prevent back streaming of oil into any of the critical components. I will do this when leaving the system off so that the chamber and rough measurement side can stay under vacuum. If you have any questions, please let me know.
Ryan Copeland
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Re: Ryan's Fusor v1 Progress

Post by Ryan Copeland »

I haven't posted an update in a long while, but I am making progress.

I have kept my chamber under vacuum ever since December with occasional pump-downs. I think I have a lot of volatiles in the chamber because when I closed the main valve the pressure would drastically increase, then level off over the course of a day and stay under vacuum two or three months. I finally decided to do a bakeout after testing and getting large fluctuations in chamber pressure when using a heat gun. I got a silicone heating tape, made by BriskHeat that can heat up to 200 degrees Celsius with a thermostat.

Chamber with silicone heating tape wrapped around it. I added insulation when doing the bakeout.
Chamber with silicone heating tape wrapped around it. I added insulation when doing the bakeout.

I pumped my chamber down to about 2x10^-6 Torr, then I started the heating tape and was careful to monitor the temperature of the turbo and the ion gauge with thermocouples so that I did not exceed their limits. The pressure rose steadily, even while the turbo was running at full speed. It eventually leveled off at 6x10^-6 Torr and I left the heating on and the turbo running for about an hour. After that, I turned off heating and took apart the insulation to let the chamber come back down to room temperature, which took another hour or so. Then sealed off the chamber as I let the turbo spin down. I took images of the pressure readouts when I sealed the chamber and then an hour after. These are the results that I got before and after the bakeout.

Before Bakeout:
Ultimate Pressure: 9x10^-7 Torr
Pressure After 1 Hour: 8x10^-5 Torr

After Bakeout:
Ultimate Pressure: 3x10^-7 Torr
Pressure After 1 Hour: 3x10^-6 Torr

I think these are good results for my first bakeout. I will check the pressure over time to see how much better it is. Would several bakeouts over a couple of weeks help to free more volatiles? Or would one long bakeout be the only way?

Hopefully I will have a long update soon on my finished transformer, I am doing the final soldering and then I should be able to test it.
JoeBallantyne
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Re: Ryan's Fusor v1 Progress

Post by JoeBallantyne »

Your pressures are orders of magnitude lower than needed to do a glow discharge fusor.

Time to get HV and D2 supply hooked up and try for some neutrons.

You are going to backfill with D2 from 3e-7 torr up to something like 1e-2 torr or 10 microns. So a bit less than 5 orders of magnitude.

Joe.
Ryan Copeland
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Re: Ryan's Fusor v1 Progress

Post by Ryan Copeland »

Thank you Joe, I should say that I am conditioning the chamber in my free time as a sort of side project just to improve the quality of the vacuum. As you said, I am far below the pressures of fusion.
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Dennis P Brown
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Re: Ryan's Fusor v1 Progress

Post by Dennis P Brown »

Might I suggest - especially during back out - add a small fan to blow rm temp air across the base of the turbo (the part with fins.) This will extend the life of the bearings and oil. Could place it under and draw air downward around the fins.
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Liam David
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Re: Ryan's Fusor v1 Progress

Post by Liam David »

Great work!

Dennis and Joe make valid points. Turbos will heat up when pumping a lot of gas (PdV) that's also preheated via your tape, so extra cooling is advised at the bearings even if the flange temperature is below the maximum specified in the manual.

You mentioned that the heater tape goes up to 200C, but what did the chamber actually reach? I'm surprised that the pressure rose to only 6e-6 during bakeout, so either the temperature was on the low side or you have a really clean chamber. Either way though, great result! The pressure after 1 hour tells the story and I don't think further bakeout is necessary. The effectiveness of one or multiple bakeouts is just a function of total heating time and temperature.

There's one thing I want to mention that no one has explicitly stated on the forums, at least to my knowledge. Let's say that you have a base pressure (all valves fully open, turbo/diff at full speed) of 1e-6 torr. The vast majority of us throttle the high vacuum pump while adding deuterium so that we don't "waste" deuterium. This often leads to a ~10x reduction in effective pumping speed, so your base pressure is now 1e-5 torr. Once the power is switched on, those deuterons and electrons love to kinetically knock gas off the walls, and the increased chamber temperature increases desorption. In other words, your effective base pressure during operation isn't 1e-6 torr and may instead be 5e-5 torr. It's this final number that one seeks to lower using a bakeout. Sure, one can do fusion with a base pressure of a few mtorr, but that extra purity really makes a difference.
Ryan Copeland
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Re: Ryan's Fusor v1 Progress

Post by Ryan Copeland »

Thank you Liam and Dennis. It was not shown in the picture I posted, but I did use several fans to keep certain components cool, as well as insulation over the chamber to more effectively heat the chamber. I had two small 120mm pc fans blowing air over both the fins of the turbo as well as the case of the ion gauge in the back, both components were frequently monitored for temperature increases. The fans were small but they moved a significant amount of air. I had a couple of other fans in the garage moving a steady flow of air over the system to the outside just for controlling any fume buildup.

The ion gauge manual specified that the electronics module needs to be kept below 70 C and the turbo inlet flange should be kept under 120 C. I used thermocouples on these areas as well as a thermal camera (on non reflective surfaces) for keeping track of the system as a whole. I frequently spot-checked certain areas such as the bottom of the turbo and the area around the ion gauge with an infrared thermometer. For the turbo, the area around the bottom with the fins heated up slowly over the two hours of operation to a maximum temperature of 32 C, just warm to the touch. The ion gauge case went up to 40 C.

I realize that I forgot to mention the actual chamber temperature in my other post, but I measured it with the infrared thermometer and it read 60 C, but it was on a reflective surface, so that might be off. The chamber definitely did not reach anywhere close to 200 C, so I would like to retry a bakeout at some point to get it above 100 C.

Also thank you for pointing out the reduction of pumping speed and the desorption. I had planned on doing a plasma cleaning once the HV was connected, but I will also run a test with the valve mostly closed to see what base pressures I can reach in that state. I am using the Varian Turbo V-250 pump, which has a listed pumping speed of 250L/s (N2) and I am certain this is quite oversized for my 4.5" cross chamber even with the 2.75" reduction leading to the turbo.

For the plasma cleaning, is there an precedent to using a higher concentration of Oxygen (~80%)? I figure the more chemically reactive ions would have a better effect when cleaning, but I am not sure if they would affect the stainless steel in any negative way or if it is negligible.
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Dennis P Brown
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Re: Ryan's Fusor v1 Progress

Post by Dennis P Brown »

I use deuterium; oxygen is not so good since it creates rust. Also, peroxides (via water vapor) would also be created and that is rather reactive in a bad way for various metals as well. For a steel chamber not the best idea and not too good for detectors exposed to the ions.

Still, very small amounts so is maybe worthwhile.

If you have access to argon that is a good species to ionize to clean a chamber if you don't want to use deuterium.
Ryan Copeland
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Re: Ryan's Fusor v1 Progress

Post by Ryan Copeland »

Thank you very much for the information Dennis, I think I will go the safe route then and just use some deuterium. It will also give me some more experience with the characteristics of a deuterium plasma. I purchased an excess of D2O knowing that I still needed to figure out all the small things about that side of the operation, so I'm not worried about running out any time soon.
JoeBallantyne
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Re: Ryan's Fusor v1 Progress

Post by JoeBallantyne »

Ryan - I noticed that you are using the Specstar pump which I believe is the same one I bought and tested for single pump fusion. (9.8CFM dual stage HVAC pump you can get on Amazon for about $250 or so.)

I'm curious what kind of vacuum will your Specstar pull? Did you use the in box oil with it, or are you using some other oil?

The Specstar I have, only pulled down to about 15 microns with inbox oil when hot, and got down to about 6 microns or so with Inland 19 ULTRA oil when hot.

I would like to compare performance of the pumps, to see if there is any significant difference in performance from pump to pump. When your pump is hot, what is the lowest vacuum it will pull, when you are measuring the vacuum with a gauge directly on the intake?

Thanks.

Joe.
Ryan Copeland
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Re: Ryan's Fusor v1 Progress

Post by Ryan Copeland »

Hi Joe, I will pull that pump off and test it with the gauge directly on the inlet. As for oil, I am using the one that came in the box. I was thinking of swapping it out for better oil, but I just left it as-is for now.

For longer runs, I keep a medium desk-type fan at full speed pointed at the pump housing because it tends to get warm. I will see how it operates without the fan and see if it helps at all. I will say that the vacuum connector for that pump gave me quite a bit of trouble when one of the flare fittings snapped right off when I tried to torque an end cap onto it, so it is sealed with JB weld, which seems to work okay. I also have several conversion fittings to get it to KF-25, so that could be a concern for leaks.

Give me a couple of hours and I will report back.
Ryan Ginter
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Re: Ryan's Fusor v1 Progress

Post by Ryan Ginter »

Try to keep at least a few inches between your gauge and the pump inlet. Placing it too close can cause the thermocouple to foul, resulting in the gauge providing a worse reading than the true state in the chamber. If the gauge is already fouled you can attempt to clean it by gently swirling acetone over it.

Edit: I just realized you're using a pirani gauge. The warnings about fouling still apply.
Ryan Copeland
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Re: Ryan's Fusor v1 Progress

Post by Ryan Copeland »

Hi Ryan, because of the several adapters I had to use to get to KF-25, there is about 6 inches between the inlet of the pump and anything I can connect. With the gauge, it is another 4 inches away. I used a backup gauge and if I suspect fouling, I will look into cleaning it. Thank you for the advice.

I finished the test with the pump and I will report the data from it. Firstly, the pump is a Specstar 2 Stage rotary vane vacuum pump, model VB280(2VB-4). The gauge I used is a InstruTech CVG101 "Worker Bee" Convection Gauge. Before the test, I set the atmospheric pressure of the gauge to the local barometric pressure while it was detached. The gauge has a listed accuracy of +/- 10% at the pressure range for the test in N2 on its data sheet. Here is the pump and the adapters:

Specstar Pump Label.
Specstar Pump Label.


Mess of adapters to get from the original flare fittings to KF-25. Note the epoxy near the bottom of the brass from where one of the connections sheered off.
Mess of adapters to get from the original flare fittings to KF-25. Note the epoxy near the bottom of the brass from where one of the connections sheered off.

I placed a piece of black electrical tape on the housing for the rotary vanes to use as a low-reflectivity surface for the infrared thermometer to measure on. Before turning on the pump, its temperature was 23.6 C. I began the test with the fan off and noted the pressure and temperature at geometric intervals beginning at 15 seconds and continuing until 64 minutes. At this point, I turned on the fan that was 5 inches from the pump pointing at the rotary vane housing. I continued to note the pressure and temperature at 5 minute intervals until 94 minutes, when I stopped the test. I recorded the pressure in Torr, as that is what my controller is set up for, but this can be converted to microns given that the room temperature was 24 C and local barometric pressure was 752 Torr. Here is the raw data and a simple graph:

Raw data from the test.
Raw data from the test.

Graph of temperature and pressure during the test. The green line denotes when I started the fan.
Graph of temperature and pressure during the test. The green line denotes when I started the fan.

At the start of the test, the pressure quickly dropped as expected. The lowest pressure achieved was 9.60 mTorr at 2-4 minutes after startup. After this point, the temperature began increasing along with the pressure. The maximum temperature the pump reached was 46.4 C at just about an hour of run time, and that corresponded to the maximum pressure during the test of 14.4 mTorr. When I turned on the fan, the temperature began to drop along with the pressure. Both seemed to be nearing a stable point by the end of the test. The cooling had a noticeable effect, but I am unsure how significant that would be for the high vacuum pump.

It is likely that there are some leaks along the brass adapters, but I was not able to check the rate of leaking in fear of oil backstreaming into the gauge. As soon as I stopped the pump, I removed the gauge from the inlet. There was likely some amount of backstreaming, but I do not think it was harmful.
JoeBallantyne
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Re: Ryan's Fusor v1 Progress

Post by JoeBallantyne »

Thanks Ryan! I have exactly the same model pump you have.

Your data corresponds really well with mine, so at least our pair of pumps have very consistent performance. I measured my pressures with an MKS901p on the inlet.

My pump with in box oil pulled down to a minimum pressure of about 5.5 microns after a few minutes when it was still cold, but the pressure rose as the pump warmed up, and once it was up to temp of ~120F it was pulling about 14.5 microns or so. Which is basically identical to what you saw before you started up your fan. Even with your fan running 13.2 microns isn't much different from 14-15.

I expect that if you replaced your oil with Inland 19 ULTRA, your pump would also pull about 6-7 microns when hot, just like mine does.

Nice to corroborate performance between pumps.

Thanks.

Joe.
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Re: Ryan's Fusor v1 Progress

Post by JoeBallantyne »

On my pump I just left the original plastic caps on the two connectors I wasn't using - as the pump has 3 different vacuum connections on the input. The plastic caps all have o-ring or rubber seals internally, and seem to hold a vacuum just fine.

Just before shutting off the pump, I just open one of those caps a bit, to release the vacuum, and as soon as I hear the pump starting to pump against atmospheric pressure, I shut it off. That way I never get any backstreaming at all. Those plastic caps are designed to be vacuum tight when they are only finger tight, so they are basically just a built in vacuum vent.

I used these two adapters to connect to the top 3/8 flare connector on the Specstar pump. Unfortunately that does mean you are stuck with an NPT between the two. I have been unable to find a one piece female flare to KF16 adapter. Ideally it would be made from brass.

3/8 female flare to 1/4 female NPT
https://www.amazon.com/gp/product/B01N0L4ETJ

1/4 male NPT to KF16
https://www.amazon.com/QMINOX-Adaptor-t ... B097H47GJ2

Joe.
JoeBallantyne
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Re: Ryan's Fusor v1 Progress

Post by JoeBallantyne »

In your case, the other thing you can do is just take off the KF16 clamp before shutting off the pump, and then remove the vacuum gauge from the KF connection immediately before you shut off the pump.

Joe.
Ryan Copeland
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Re: Ryan's Fusor v1 Progress

Post by Ryan Copeland »

Hi Joe, I'm glad that the data was useful. I may end up changing the oil in the future, but for right now I will focus on getting neutrons since my pressures are low enough.

I was unclear about my worry of backstreaming in my previous post. In my fusor setup, I have a valve dedicated to venting the rough side of the system to atmosphere through a filter. This is the ATM valve seen in my valve diagram a further up. I was worried about backstreaming from the pump to my gauge during this specific test because they were so close together, which is why I detached them as quickly as possible.

I should have probably just left the plastic caps on the pump, but at the time I didn't trust the plastic to hold up to extended duration vacuum, so I tried to switch them for brass, which ended up backfiring. I'm glad that the epoxy doesn't seem to have too much of an effect on its performance.
JoeBallantyne
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Re: Ryan's Fusor v1 Progress

Post by JoeBallantyne »

I think your plan to focus on neutrons is spot on. You have a turbo, and can pull your fusor down really low, so the vacuum your backing pump pulls is basically irrelevant.

Good luck getting neutrons!

Joe.
Last edited by JoeBallantyne on Thu May 23, 2024 1:00 pm, edited 1 time in total.
Ryan Copeland
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Re: Ryan's Fusor v1 Progress

Post by Ryan Copeland »

Thank you very much Joe. I should have an update soon on the transformer, whether good or bad. I'm going to clean up the setup a bit and get it ready for the HV tests.
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