Introduction

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Shireesh Apte
Posts: 26
Joined: Sun Sep 10, 2017 2:16 pm
Real name: Shireesh Apte

Introduction

Post by Shireesh Apte » Sun Sep 10, 2017 3:10 pm

I am a high school teacher in Texas. My students and I want to eventually build a fusor. We are currently in the process of building a 'star-in-a-jar' rudimentary apparatus. We ordered a high voltage power supply (claims 60 kV at 12 mA) that is supposed to be for electrostatic precipitators from China on ebay. Its input is 220 V so we have a 110 to 220 V converter plugged into a variac that we keep at 110 V. The high voltage power supply has two potentiometers, one we assume is to turn up the voltage. We do not know what the other one is for. We have this hooked up to a stainless steel coat hanger inner grid with a 1/4 inch copper pipe as outer grid in a large mason jar with a PVC lid. The inner grid is encased in a 25% ceramic plus 75% 'plaster of paris' hardened mixture. We made this by using an outer paper cylinder to drop the wet mixture in. Then we sealed both ends with tape and kept it in a 200 C oven for 24 hours. We then removed the paper and tape. Only the spherical grid at the end is exposed inside the Mason Jar. Our vacuum system is a 3 CFM rotary vane pump that the brochure says will go down to 5 Pa absolute or 38 microns approximately. We are using play-dough to tightly clamp the PVC lid on the mason jar since we cannot exactly find a matching ID. Our gauge on the rotary vane vacuum pump goes down to minimum hence we are assuming that we are operating at approximately < 100 microns; which should be good enough to get a plasma. Our issue is that we do see a plasma but it is at the upper end of the Mason Jar, i.e. where the inlet for the ceramic encased inner grid and the copper tubing is. It is purple in color. I will ask my students to post a video of the plasma as well as pictures next week at this site. We think we may either too deep - or not too much of a vacuum. We are going to run again tomorrow with the vacuum pump shut off to see if we get a plasma at slightly higher pressures. Once we post the pictures and video, any suggestions on how to get the plasma at the center will be welcome.
We realize this is obviously the first step toward eventual fusion. We anticipate at least getting to 'jump off' point by this academic year end (May 2018). We have contacted a deuterium supply that we found on these forums. We have ordered and received a gas regulator. We are in the process of looking at ordering a thermocouple pressure gauge, oil diffusion pump, needle valve, and assorted piping and valves. We also plan to build a (8 inch) stainless steel fusor from ss plates with 4 ports (vacuum, high voltage feedthrough, deuterium supply, and porthole). We will use powdered silver kept in a moderator to detect neutrons. The idea is that thermal neutrons will convert the silver to cadmium with emission of gamma rays, which we can detect using a geiger counter.
We will keep you posted.
Best regards,
Shireesh
Last edited by Shireesh Apte on Sun Sep 10, 2017 3:29 pm, edited 1 time in total.

Shireesh Apte
Posts: 26
Joined: Sun Sep 10, 2017 2:16 pm
Real name: Shireesh Apte

Posting shared link to video

Post by Shireesh Apte » Sun Sep 10, 2017 3:23 pm

A shared link to our video appears below. The video may not play when you click on the link. However, there is a download option available so that you may download to your computer and play it using your computer apps. This is what I had to do as well.

https://drive.google.com/file/d/0ByEkO9 ... sp=sharing

Best,
Shireesh

Niels Geerits
Posts: 53
Joined: Tue Jun 13, 2017 10:25 pm
Real name: Niels Geerits

Re: Introduction

Post by Niels Geerits » Mon Sep 11, 2017 3:38 pm

Shireesh, An easy way you guys can estimate the pressure is by measuring the voltage over and current through the fusor. You can check the FAQs on the best way to do this. I just put 100 1W 10M ohm resistors in series (15 cents each) + a single very precise 100k Ohm and a voltage meter in paralell to the 100k ohm resistor. This resistor chain is in paralell with the fusor. The current is measured by putting a 100 ohm resistor in series with the fusor and measuring the voltage across said resistor. If you measure a low voltage you have a high pressure, assuming your power supply is good. See this FAQ viewtopic.php?f=24&t=2795

Shireesh Apte
Posts: 26
Joined: Sun Sep 10, 2017 2:16 pm
Real name: Shireesh Apte

Re: Introduction

Post by Shireesh Apte » Tue Sep 12, 2017 12:09 am

Thanks Niels. We will check this out.
Best,
Shireesh

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Dennis P Brown
Posts: 1301
Joined: Sun May 20, 2012 2:46 pm
Real name: Dennis P Brown
Location: Glen Arm, MD

Re: Introduction

Post by Dennis P Brown » Tue Sep 12, 2017 3:03 pm

Play-dough to seal a vacuum chamber? Really? You appear to be using very low grade stuff to build your system. This concerns me for a high school. While I have read a bit on the Chinese electro-static power supply here (and I have my doubts it will provide the power it claims) it does appear to be capable of producing a dangerous voltage/current and you do not appear to have much knowledge of electrical systems - like safe wiring, standoffs, proper high voltage housing or feed-thru design, grounding, and there is more. While I appreciate using available stuff to build a vacuum system (my first vacuum/sputtering system, also in High School, was a wine bottle with its end cut off and a 'rubber' stopper for a electrode feed-thru), this approach has no place for use with any real (or semi-real) power supply. Be careful - if its rated power can supply even a few milli-amps, then it can kill.

Any attempt at a real fusor will absolutely require you first get a gauge that reads microns and you should wait for that to come in (and this should be one of the first items you get.)

As for getting a good plasma glow, once you achieve a few tens of microns and have a power supply of a few hundred to a thousands volts (no real current required so many cheap ways to do this) a plasma glow will be struck.

Shireesh Apte
Posts: 26
Joined: Sun Sep 10, 2017 2:16 pm
Real name: Shireesh Apte

Re: Introduction

Post by Shireesh Apte » Sun Sep 17, 2017 11:52 pm

Duniway has rebuilt diffusion pumps (speed: 105 L/s) at $600. Ebay does not seem to have any diffusion pumps any cheaper either. I searched the forums and it appears that I will need > 60 L/s for a robust vacuum. Is there anywhere else I should be looking for a cheaper diffusion vacuum pump?
Thank You and Best regards,

Shireesh Apte

MatthewL
Posts: 27
Joined: Mon Mar 06, 2017 12:13 am
Real name: Matthew Lallinger
Location: Houston, Tx

Re: Introduction

Post by MatthewL » Mon Sep 18, 2017 12:38 am

Ebay is usually the best place to find a diffusion pump that is inexpensive. With enough searching a good pump can be found for well under $300. Perhaps try different search terms. It can also be helpful to follow a search so that you can get notification emails when new listings appear. LabX.com can also have options as well.

Regards,
-Matthew

Shireesh Apte
Posts: 26
Joined: Sun Sep 10, 2017 2:16 pm
Real name: Shireesh Apte

Re: Introduction

Post by Shireesh Apte » Mon Sep 18, 2017 4:12 pm

Thanks Matthew, we will try that.
Best,
Shireesh

Shireesh Apte
Posts: 26
Joined: Sun Sep 10, 2017 2:16 pm
Real name: Shireesh Apte

Re: Introduction

Post by Shireesh Apte » Tue Oct 10, 2017 5:10 pm

We are still trying to get a low enough vacuum. We obtained a Fieldspace micron vacuum pressure gauge but we have been unable to pump down to below 500 microns (its upper set reading). I am going to change out the plastic tubing we are using for SS tubing sometime this week. We are using a 2 stage, 4 CFM rotary vane vacuum pump for now. My objective is to get plasma before I plunge into the fusion part of this project. Is it at all possible to get a vacuum of < 500 microns using silicone tubing? I am currently using garage door grease on the barb fittings before inserting the tubing over them to hopefully get an airtight seal but I am beginning to have serious doubts as to whether this is possible - hence the planned change to SS tubing with proper NPT adapters.

As regards the fusion part, I have a 4 way SS cross (2.75 inches) with CF flanges. I have ordered three CF to female NPT adapters with copper gaskets and one CF quartz view port. We have a deuterium supplier that we found and contacted thanks to these posts. Our Chinese Electroprecipitator unit is still functioning and the (extremely) brief user-guide on ebay says it can do a maximum of 60 KV, but we have never measured the output voltage. We will order a diffusion pump when we have plasma.

Best,
Shireesh Apte

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Richard Hull
Site Admin
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Joined: Fri Jun 15, 2001 1:44 pm
Real name: Richard Hull

Re: Introduction

Post by Richard Hull » Wed Oct 11, 2017 3:56 am

Read the FAQs on vacuum system and pump testing. Do not hook up any vacuum lines! Hook the gauge right to the pump's inlet....This should tell if the pump is even capable of going below 500 microns. Do not use garage door grease as it can easily outgas its volatiles ruining any chance of ever going below the vapor pressure of the grease.

Your questions should be posted in the new user forum or in the vacuum form. This is just your introduction forum and should not include questions or be used for seeking advice.

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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