we need to get this manz a bunker so that at least he can survive the impending doom... Also think of all the extra experiments he could do if he had an underground bunker to use once that garage got filled up!
When I was in college one of my profs was telling stories about his vacuum experiences. One; he had carefully set the system up, using all the lessons learned earlier (e.g. new copper gaskets) but it would not pump down. Tore the rig apart and found a fly in one of the tubes. Turns out flies out gas rather well. :^)
Mine had a story like that about an early big accelerator. One of the builders left a sandwich from their lunch in the beam pipe. You can pump a long time on a ham sandwich.
Well, I once forgot switched on flashlight inside vacuum chamber (ion beam sputtering). Pumping was a bit slower than usual but marginally ok. I was pretty shocked when opened a window and saw the light...
I've worked with the large diffusion pump system for years and understood the theory, but THIS is what I've always wanted to see. Thank you this is awesome.
Yeah, right? I used to run ion deposition chambers with twin DPs each the size of a home water heater. Never had the time to really understand how they worked.
they're so simple that it's a pleasure to take one apart for cleaning - leaking krytox was the biggest problem, it was $2000+ per gallon back in the 90's
Similar experience here, I'm a design engineer for a company manufacturing electron beam welders. Always wondered what exactly was going on inside the diff pumps we use, plus the added bonus of seeing a mini EB gun.
Glass diffusion pumps are still commonly used for neon sign work and were also in quite common use for producing one off vacuum tubes and the like. The advantage is in the ability to connect to an all glass manifold for gas back filling or to the pumped item directly with glassworking techniques rather than metal working techniques. As a side note DC-704 and other silicone based diff pump oils cause great havoc when exposed to atmosphere while hot resulting in an horrid black tar which cannot be removed except by aggressive mechanical means. The much safer (read: expensive) option is a Polyphenyl Ether based oil like Santovac-5 which contains no silicon.
"Here's a cool video about my glass vaccuum pump" "oh don't mind this homemade crt, I was just using it because this didn't work for my mass spectrometer"
Hi, I worked for a company, before I retired, that made photomultipliers and they used mercury/glass diffusion pumps for many years. They also made some of the first television camera tubes and I think these were pumped down using mercury/glass diffusion pumps too. They had a glass blowing department where new glassware was made when required. Very interesting video, thanks very much.
My god, that’s genuinely fascinating. Makes me kind of sad about being born after everything slowly shifted towards semiconductors, even though that’s plenty interesting as well ;) Funnily enough i still managed to have some contact points with some quite serious photomultiplier tubes due to the (admittedly crazy) idea of frankensteinig together a broken large format drum scanner in my dorm room LOL
As you explained in the video, the silicon oil absorbs unwanted substances, so the mechanical pump is always needed to bring the vacuum down, draining out such substances, as you did, and then getting out the residual gas. It also helps to drain down the oil vapour. If you turned the mechanical pump off, you'd contaminate your vacuum chamber, even if you cool the top of the diffusion pump with liquid nitrogen. Therefore you must have an automatic valve to shut out the connection with the chamber if electricity goes out. Actually they are a pain in the neck to use, so people prefer turbo-pumps which are far cleaner, if they can afford them, that is. By the way, great video! I really appreciate your resourcefulness.
Turbopumps are hard to scale, though, and a big installation needs a lot of them. This is why in big vacuum furnaces you will see diffusion pumps used to create the high vacuum. They are also often used in synchrotrons in tandem with cryopumps.
Hello. I am a SEM operator. I was just studying up on SEM theory, particularly the pumping systems, turbomolecular pumps and oil diffusion pumps. I couldnt find a really good demo or video to see exactly the flow paths. Your video that is brand new, perfect timing, it really answered a lot of question of the actual flow paths for me. Thanks a million. I love your approach, discussed in the beginning of your behind the scenes video. I also learned most of my engineering skills on my own in life, garage, fixing and building things, not in the university. I am very grateful for you wonderful sharing. Raanan
Great video as always! Few notes though, as you have shown it, forvacuum mechanical pump could still reach absolute vacuum with infinite time, which is not true for real pumps. Real mechanical pumps have a hard limit on the pressure they can achieve (even given INFINITE time!), largest limiting factor being "dead space" of the pump(turbopumps excluded). Dead space is a volume of gas at exhaust pressure(1 atm for forvacuum pumps exhausting directly outside) which is left when exhaust valve is closed. If you think about plunger/piston type pump, it is the volume which is left when cylinder is compressed completely. Air in dead space at atmospheric pressure then is expanded to full cylinder volume, decreasing the pressure until intake valve opens, which limits the minimal pressure one can achieve. You don't seem to have a return path for electrons in your crt, you are charging the screen which screws with focus and makes it fuzzy. Also you could try to deposit ZnS as a classic green luminophore. Edit: fixed grammar to make it feel less like I had a stroke. Merged another comment.
@@ipissed sorry, I maybe should rephrase it in the morning, didn't mean to sound like I'm attacking. But what I want to focus on, is that main limiting factor for pumps relying on change of working area volume is the amount of dead space, limiting pressure even before molecular flow sets in.
Interesting point about the charging of the screen. How best to fix this? Deposit a clear conductive layer beneath the phosphor and wire it to the filament? I wonder if I can manipulate my CRT oscilloscope’s trace with a high voltage near the screen...
@@Scrogan traditionally you would rely on material of phosphor having strong secondary emission so for each electron hitting you get multiple electrons leaving. Then you would need rest of internal surface up to an election gun covered with positively biased conductor to capture and remove those secondary electrons. Also from what I seem to recall phosphors on old screen looked grainy, I am not sure, but that might have been done on purpose to increase secondary electron emission.
Thanks for this description, suddenly pumps make a lot more sense, reminds me of multi-stage refrigeration where one of the limits is the temperature of the heat dump, same with the pressure of your air 'dump'.
I’ve been trying for a while to wrap my mind around how and why diffusion pumps work. Not quite there yet, but thank you for increasing the clarity a lot!
I like how I can sit down after working all day with work stuff running through my head and instantly be engrossed by one of your videos, and having just enough knowledge to understand what you are very eloquently explaining. I think it has more to do with the fact that you make it very easy to follow along even if someone has no clue what a diffusion pump is.
At work we use liquid ring pumps(very clever pump IMO), dry screw pumps, roots blowers, and steam jets(venturi) to pull high vacuum for distillation processes. We use this vacuum post reaction and during distillation of various chemicals.
I'd think nichrome should work well as an electron emitter at dull red heat since chromium oxide is an excellent source of electrons, I'd heat it in air one time to get some oxide.
Sorry to blow your idea. The nichrome will burn out long before it begins to emit. I have tried this in my tubemaking with zero results. Oh well! Stick with the tungsten with the barium carbonate.
Thank you. Worked as a mass spectroscopist using GCMS, He leak detectors, and isotopic ratio mass spectrometers. System pressures were 10 -8 microns or lower with a good vacuum. Use dry nitrogen or argon to let the system up to atmospheric pressure. This reduces pumping time. Water from water vapor in the air is an enemy as far a getting a good vacuum. You might get some vacuum gauges. A 1946 tube with a meter or a Pirani gauge is good for rough vacuums down to about 1 micron. For higher vaccums, use a hot cathode or a cold cathode vacuum gauge and controller.
Wow! Great video! I worked for a vacuum furnace company. They would have two guys clean the inside of the entire furnace with alcohol prior to the first run up. This minimized the outgassing but took the better part of a day. It would take quite a while to pump down(rough out) the first time. One time the valve controlling the diffusion pump vacuum flow was installed incorrectly. The roughing pump pulled the oil out of the diffusion pump coating the inside of the furnace. If I remember correctly, it took several days to clean it all out.
I first encountered oil diffusion pumps in graduate school. Our Beckman ultracentrifuge had a standard reciprocating piston pump to get most of the air out of the chamber. Then you switched on the oil diffusion pump to get a very high vacuum. I'd never heard of such a thing before and was fascinated by how they function with zero moving parts. This was in the early 80s, no internet or Google back then so I had a bit of a job finding the information.
Great explanation. Whoever invented this... wow. "We could push those last few molecules out with vapor molecules we boil and move around right inside the chamber!" I bet the rest of the people standing around looked at them like they were nuts.
Very nice explanation. One of the hard limits of a diffusion pump is the back flow from desorption of the pump fluid. I've only worked with mercury pumps preferring a Balzer any day
CRT's are super cool. We need to get you into a glass blowing class so you can make a suitable neck, and play around more with your glass experiments. Awesome video as always, thanks!
I worked with lots of cryos and turbos and lots of mechanical pumps even with Roots blowers boosting them but I never worked with diffusion pumps. Very interesting.
I am in need of a vacuum wood kiln. I was just reviewing Sprengel pumps and other less conventional pumps. Like you said the volume that needs to be evacuated makes these less practical. Especially when time is money. Awesome video as always. You are a fascinating dude.
Very nice video and beautiful pump! Gives me flashback to my PhD there we used a 50 liter diffusion pump to vacuum a huge high voltage discharge system. The stove was firmly attached to its bottom and the running tap water was used for cooling. The engineers told me that the hot oil would burn if no pre-vacuum created prior to heating it up.
I worked where they mirrored glass on a machine that had a mercury diffusion pump, That thing could pull a vacuum in a 20 cubic foot chamber in like 5 seconds, then the aluminum filaments would start up and deposit onto the glass in about 5 seconds. It was very cool.
I didn't think heat was used in a mercury vacuum pump. I thought it worked by circulating the Mercury to the top of the system and letting it fall through a restricted opening over and over?
@@lvstofly You describe a Sprengel pump, which is not the same. Cody'sLab built one, there's a vid. A mercury diffusion pump works just like this oil version.
The diffusion pump by itself is amazing. But the CRT demo is awesome. That has to be the most simple vacuum tube i have ever seen. I had never thought of making one using more standard laboratory glassware.
Fantastic! Thanks for showing. I used Diff pumps for almost ten years in EM but of course even servicing them you can't see how they work. Great idea to show everyone!
Was watching the how it's made and whatnot. Color is HARD with all the phosphors and grids (tech ingredients had a great series on this). But black and white (which may use multiple phosphors) or black and green, or black and red is easier. the hardest part is the phosphor coating i think (that and maybe digging for how to make a good electron gun). Seems you are beating me to it to a certain degree! Best of luck, and i hope to do the same someday!
Thank you for this amazing video. I've always wanted to actually see what's going on in my metal diffusion pump. Now I know! The CRT is an astonishing achievement too, well done there. Barium carbonate is converted to barium oxide upon heating, and barium oxide would combine with with moisture from the atmosphere to form barium hydroxide so as you say quite rightly it cannot be subjected to the air once applied and heated.
Diffusion pumps are really interesting pieces of equipment. The downside with them is that no matter what one does, they will always out gas oil into the chamber, due to the vapor pressure of the oil. Though, for a lot of stuff, that isn't a major issue.
Worked with diff pumps for a long time. Cool to see one like this. Btw, you should have insulation near the heat source to prevent rapid cooling at the bottom. Also, with the plastic.. helium can penetrate some with no issue and it's even used to outgas helium (used as a carrier gas) from thicker material by pushing through plastic or PTFE loops.
the reason why they don't use diffusion pumps as a single stage is because the pressure difference that they create is pretty low. so this can (very roughly speaking) either get your pressure from 1 bar to 0.99 bar or from 0.01 bar to almost 0, that's why it makes sense to use a mechanical pump as the first stage to get you to that 0.01 in the first place.
Love your channel! You are heating the diff pump oil too much, you do not want it to boil. The correct temp is just where there is slight movement on the surface of the oil and the temp varies with the type of oil used. 702 = 180-190C 704 = 220-230C Yes never ever use plastic tubing in vacuum systems - thick wall latex is acceptable. Me? I used to be a high vacuum service tech.
@@hellelujahh Reduces the efficiency. The goal is the oil vapor streaming at supersonic speeds to impart its kinetic energy to gas molecules deflecting them down away from the inlet and compressing them. When you boil the oil the vapor streaming is chaotic, and if liquid oil droplets impede the vapor stream.
Wow! This is really cool! As you can see from my TH-cam channel, I've been using diffusion pumps for many years, but never had the opportunity to "see" them in action! Great video! Thanks!
Electron microscopes tend to use either pure tungsten or a LaB6 (lanthium hexaboride) tip if they are purely thermally driven. This means they are easily user replaced in the lab and we dont have to handle sealed units when replacing the tip. Using your material for extra brightness would caus problems with that. Extra brightness is always nice but honestly, we burn through tips every few years, so replaceable is key. For extra brightness we tend to use a FEG (field emission gun) which draws electrons out using electric fields (with or without additional heating). Really interesting video btw, having used oil diffusion pumps for years its nice to watch it working.
As a note; Modem electron microscopes use lanthanum hexaboride emitters, and they have isolation valves such that the source never gets exposed to air. A separate vacuum backing for the source keeps it at very low vacuum (10^8 or better) and there are interlocks for vacuum level that must be closed before the sample chamber is opened to the source
Be, without the aquadag on the edge of the front of the tube you are probably getting some X-Ray leakage. I love the demonstration. Your channel is fantastic.
I know this is a joke.... but... I'd actually be curious if he could build a particle collider (I'm almost certain he could). I mean... he's done homemade superconductors.... I think a beam collider would be well within his ability. I think the only hard part would be creating some sort of detector to collect the collision products.
The oil & chemical industries uses steam ejectors - those work off of the momentum transfer method too. Like the bottom of your diff. pump ejectors can be staged and the final pressure (vacuum) is determined by the overall compression ratio. I worked with those in the 90's and the roar of the steam was deafening.
Really cool! I think this is the first video that illustrates how diff pumps work that well on youtube. I actually seen one of those pumps in a store in Shanghai but didn't really think it can work (that well), given how small that inlet is.
I recently learned about turbomolecular pumps. The way it was explained is that you can wait for random motion of molecules or impart a specific motion on molecules to move them. High vacuum pumps do the latter.
Great video as always! I didn't know that diffusion pumps came in glass! A lot of systems in the semi industry have moved away from diffusion pumps in favor of cryo or turbo pumps for achieving high vacuum in sensitive systems where any backstreaming(what you talk about around 5:37 ) could be catastrophic. If anyone wants to learn some more about vacuum systems "A User's Guide to Vacuum Technology" by John F. O'Hanlon is, from my understanding, the industry standard for vacuum systems. Certainly at a minimum quite a good resource. It was one of the required textbooks for my thin films class.
I love this guy. A lot of what he does may seem unbelievable, but originally it was just other humans that figured it out so he says "I'm a human" and proceeds to apply science to demonstrate amazing phenomenon. Having some underlying education helps. Of course it takes a dedicated individual to pull it off. I'm not trying to minimize his achievements at all. My overall point is all you need is the brain you were born with to do amazing things.
I cannot believe how much cool stuff is in there! I just learned about oil diffusion pumps and electron guns in the context of high-tech cryoEM and you just make all of this in your basement XD
Very cool video! I work at a high vacuum company, we use diffusion pumps large enough to fit inside. This is my first time actually seeing one operate. Its a concept quite difficult to understand with out a visual, I will be showing this to future recruits. I also liked your explanation of molecular flow in everyday terms. I'd like to know what type of oil you used. And yes, too bad that particular pump was made with such poor conductance. I'm not sure how difficult it would be to home build and Ion Pump? That would be very cool to see, and help you achieve UHV. Keep experimenting!
Maybe try heating the filament slowly and to a lower peek current. I suspect the barium oxide is acting as an insulator allowing the tungsten to reach too high a temperature. Also, the barium carbonate could act as an oxidizer with respect to tungsten at high temperatures so best to decompose it slowly at a lower temperature.
Fascinating..I've read about diffusion pumping..never worked anywhere that used it though... does look more finicky compared to the tmp and cryopump set up I'm more used to in commercial work.
I worked with an elektron-microscope which used an impeller-pump like the compressor side of a turbocharger to build a solid vacuum. Never heard of this pump, cool!
It is really cool to be bale to see inside of the glass diffusion pump and watch the oil boil and condense. I just wanted to share some notes from my past experience with these and other high vacuum systems. The reason it is called a "diffusion" pump is because the gas molecules (mostly oxygen and nitrogen) bounce out of the vacuum chamber, into the body of the pump, and diffuse into the small oil vapor droplets that reach it up to the top of the pump. The pumping performance relies on gas solubility as a function of temperature. At the top, it is coolest where gasses are more soluble in the oil. At the bottom, it is hot where the gas molecules are less soluble and will be liberated as gas molecules. It is then up to the backing pump to take these liberated gas molecules away. Silicone oil is preferred since because of its higher gas solubility and because it is more stable for a long period of time. A diffusion pump that size should be around 800 W. I had a 900 W diffusion pump at my old place of work that was similarly sized albeit metal. After cleaning that 900 W pump with trichloroethylene and servicing its larger backing pump, I was able to get our 3 gal vacuum chamber down to 10^(-8) Torr - which is a typical ultimate pressure for diffusion pumps. The primary disadvantage of diffusion pumps is their pumping speeds and the contamination (like you mentioned). For these reasons, they are not used for semiconductor fabrication. Turbo pumps are most commonly used since they can pull a high vacuum very fast and don't use as much power as a diffusion pump. Cryo pumps are a little slower than turbos but offer the similar vacuum performance and are not prone to oil contamination. This is one of the reasons why cryo pumps are used on thin film deposition equipment in the semiconductor fabrication industry.
Worked in high vacuum metalization for about 25 years we used to climb in some of them to clean them. Ours had bell covers that lifted when we hit a certain mbar. Boy tell you what them bells pop in atmosphere the heated oil would flash and the explosions was some kind of loud🤣 Make your ass jump anywhere in the plant. I’ve seen them blow hard enough to deflect the main shaft which were very thing stainless steel. This is a really cool model and I enjoyed this thoroughly. I have to show this vid to my brother this is too cool
About your claim that you don't technically need the roughing pump (at ~5:10). My experience is if the outlet of the diffusion pump is above a certain pressure, the oil in the diffusion pump increasess in volume (due to dissolved gas) and spills over into your system. The excess air pressure can also burn (oxidize) the oil making it char. This is a problem especially when the power goes out -- if it comes back on unattended, your roughing pump doesn't pump down fast enough, and the pressure is too high when the oil starts moving again. Just nitpicking -- your videos are so cool!
@@corwinweber693 Barium is not radioactive.It is even used as a contrast liquid, for example to take x-rays of blood vessels. Yes, then it is injected.
I loved that . yes outgassing, araldite do low outgass epoxy, chrome , nickle are low outgass coatings. high vacuum is another beautiful world. I would love to see a lathe / mill made cryo pump.
I remember replacing a mercury diffusion pump on an ancient Joel SEM in college and replacing it with a turbomolecular pump. The original pump had a rather large quantity of mercury in it. The turbomolecular pump was wayyy quicker and took a lot less power during pumpdown. 🤓❤
Hey Ben, Just reaching out to you quickly, is it a way to reach out to you via email? I'd like to urgently collaborate with you on something. Thanks in advance!
As always, the awesomeness of this content is inversely proportional to the usability for my own little projects. Correction - make that inverse square.
A glass pump with mercury would sure look cool though.
Cody, you've got yourself a project!
But people will know I got the idea from another TH-camr! 😆
@@theCodyReeder Challenge people to find the video you got the idea from at the start of your video :)
Offer some mercury for the project. A colab!
Collab with Cody and Applied science would be awesome.
Applied Science: Oh yeah, and I made a CRT out of some things I had lying around, NBD.
Yeah, just a toss-away bit of info that literally no one can duplicate in their garage. I love this channel.
Well in my garage I painted a picture frame black today. Sooo, that's a thing too.
I made some horse head bookends.
I farted, so I made a smell.
we need to get this manz a bunker so that at least he can survive the impending doom... Also think of all the extra experiments he could do if he had an underground bunker to use once that garage got filled up!
When I was in college one of my profs was telling stories about his vacuum experiences. One; he had carefully set the system up, using all the lessons learned earlier (e.g. new copper gaskets) but it would not pump down. Tore the rig apart and found a fly in one of the tubes. Turns out flies out gas rather well. :^)
The one thing all stem profs have to deal with, bugs in their systems.
Mine had a story like that about an early big accelerator. One of the builders left a sandwich from their lunch in the beam pipe. You can pump a long time on a ham sandwich.
@@sealpiercing8476 pumping ham sounds like a sex act with a fat lady or a farm animal.
Pumped a cricket down to high 4 scale Torr lol
Well, I once forgot switched on flashlight inside vacuum chamber (ion beam sputtering). Pumping was a bit slower than usual but marginally ok. I was pretty shocked when opened a window and saw the light...
I've worked with the large diffusion pump system for years and understood the theory, but THIS is what I've always wanted to see. Thank you this is awesome.
Yep, same ICR-FTMS with 2x 1600l/sec Edwards diff pumps with 2x1800W heaters and SAME roughing Alcatel pumps like in video ...
Used Diff pumps a lot, no how they work, seen a hundred diagrams and only your channel showed me one running....cheers!
same, I maintained a set of big Varian diffusion pumps for over a decade - it's very cool to see a glass version
know*
Yeah, right? I used to run ion deposition chambers with twin DPs each the size of a home water heater. Never had the time to really understand how they worked.
they're so simple that it's a pleasure to take one apart for cleaning - leaking krytox was the biggest problem, it was $2000+ per gallon back in the 90's
Similar experience here, I'm a design engineer for a company manufacturing electron beam welders. Always wondered what exactly was going on inside the diff pumps we use, plus the added bonus of seeing a mini EB gun.
Glass diffusion pumps are still commonly used for neon sign work and were also in quite common use for producing one off vacuum tubes and the like. The advantage is in the ability to connect to an all glass manifold for gas back filling or to the pumped item directly with glassworking techniques rather than metal working techniques. As a side note DC-704 and other silicone based diff pump oils cause great havoc when exposed to atmosphere while hot resulting in an horrid black tar which cannot be removed except by aggressive mechanical means. The much safer (read: expensive) option is a Polyphenyl Ether based oil like Santovac-5 which contains no silicon.
Yep Santovac5 is what i have used
"Here's a cool video about my glass vaccuum pump"
"oh don't mind this homemade crt, I was just using it because this didn't work for my mass spectrometer"
mmm.. including BaCon!
I applaud the glass maker that did this
He probably makes the sickest bongs
@@momsspaghetti7165 The chinese also makes the sickest drugs...
I do glass blowing making vacuum tubes and I had the same reaction! Some of these guys are amazing!
Its amazing that thing doesn't implode.
Hi, I worked for a company, before I retired, that made photomultipliers and they used mercury/glass diffusion pumps for many years. They also made some of the first television camera tubes and I think these were pumped down using mercury/glass diffusion pumps too. They had a glass blowing department where new glassware was made when required. Very interesting video, thanks very much.
My god, that’s genuinely fascinating. Makes me kind of sad about being born after everything slowly shifted towards semiconductors, even though that’s plenty interesting as well ;)
Funnily enough i still managed to have some contact points with some quite serious photomultiplier tubes due to the (admittedly crazy) idea of frankensteinig together a broken large format drum scanner in my dorm room LOL
although it must have been mundane at the time, it's very interesting to think of these production processes now.
As you explained in the video, the silicon oil absorbs unwanted substances, so the mechanical pump is always needed to bring the vacuum down, draining out such substances, as you did, and then getting out the residual gas. It also helps to drain down the oil vapour. If you turned the mechanical pump off, you'd contaminate your vacuum chamber, even if you cool the top of the diffusion pump with liquid nitrogen. Therefore you must have an automatic valve to shut out the connection with the chamber if electricity goes out. Actually they are a pain in the neck to use, so people prefer turbo-pumps which are far cleaner, if they can afford them, that is.
By the way, great video! I really appreciate your resourcefulness.
Turbopumps are hard to scale, though, and a big installation needs a lot of them. This is why in big vacuum furnaces you will see diffusion pumps used to create the high vacuum. They are also often used in synchrotrons in tandem with cryopumps.
Hello. I am a SEM operator. I was just studying up on SEM theory, particularly the pumping systems, turbomolecular pumps and oil diffusion pumps. I couldnt find a really good demo or video to see exactly the flow paths. Your video that is brand new, perfect timing, it really answered a lot of question of the actual flow paths for me. Thanks a million. I love your approach, discussed in the beginning of your behind the scenes video. I also learned most of my engineering skills on my own in life, garage, fixing and building things, not in the university. I am very grateful for you wonderful sharing. Raanan
1:55 You can not unsee those eyes on the vakuum
pump, once you have seen them.
rofllll you right xD
I spent more time than I care to admit trying to decide if they were functional bolts/screws or if he’d stuck googly eyes on it...
Ty Hu
or maybe googly eyes were placed on top of functional bolts or screws. O_O
@@BothHands1 lol
lollerskates! LMAO!
Some serious work went into making that apparatus. Great video!
While it might not be the most practical diffusion pump ever, that pump is still a thing of beauty.
Great video as always! Few notes though, as you have shown it, forvacuum mechanical pump could still reach absolute vacuum with infinite time, which is not true for real pumps. Real mechanical pumps have a hard limit on the pressure they can achieve (even given INFINITE time!), largest limiting factor being "dead space" of the pump(turbopumps excluded). Dead space is a volume of gas at exhaust pressure(1 atm for forvacuum pumps exhausting directly outside) which is left when exhaust valve is closed. If you think about plunger/piston type pump, it is the volume which is left when cylinder is compressed completely. Air in dead space at atmospheric pressure then is expanded to full cylinder volume, decreasing the pressure until intake valve opens, which limits the minimal pressure one can achieve.
You don't seem to have a return path for electrons in your crt, you are charging the screen which screws with focus and makes it fuzzy. Also you could try to deposit ZnS as a classic green luminophore.
Edit: fixed grammar to make it feel less like I had a stroke. Merged another comment.
He never said a mechanical pump would ever work with time, he said the factor was time.
@@ipissed sorry, I maybe should rephrase it in the morning, didn't mean to sound like I'm attacking. But what I want to focus on, is that main limiting factor for pumps relying on change of working area volume is the amount of dead space, limiting pressure even before molecular flow sets in.
Interesting point about the charging of the screen. How best to fix this? Deposit a clear conductive layer beneath the phosphor and wire it to the filament? I wonder if I can manipulate my CRT oscilloscope’s trace with a high voltage near the screen...
@@Scrogan traditionally you would rely on material of phosphor having strong secondary emission so for each electron hitting you get multiple electrons leaving. Then you would need rest of internal surface up to an election gun covered with positively biased conductor to capture and remove those secondary electrons. Also from what I seem to recall phosphors on old screen looked grainy, I am not sure, but that might have been done on purpose to increase secondary electron emission.
Thanks for this description, suddenly pumps make a lot more sense, reminds me of multi-stage refrigeration where one of the limits is the temperature of the heat dump, same with the pressure of your air 'dump'.
I’ve been trying for a while to wrap my mind around how and why diffusion pumps work. Not quite there yet, but thank you for increasing the clarity a lot!
I like how I can sit down after working all day with work stuff running through my head and instantly be engrossed by one of your videos, and having just enough knowledge to understand what you are very eloquently explaining. I think it has more to do with the fact that you make it very easy to follow along even if someone has no clue what a diffusion pump is.
New videos from this channel work better than SSRIs at alleviating depression.
At work we use liquid ring pumps(very clever pump IMO), dry screw pumps, roots blowers, and steam jets(venturi) to pull high vacuum for distillation processes. We use this vacuum post reaction and during distillation of various chemicals.
Amazing. The amount of effort that goes into your videos is truly inspiring.
I'd think nichrome should work well as an electron emitter at dull red heat since chromium oxide is an excellent source of electrons, I'd heat it in air one time to get some oxide.
That is actually interest, could be worth a try.
And you can buy it precoiled for vape pens really cheaply on aliexpress.
Sorry to blow your idea. The nichrome will burn out long before it begins to emit. I have tried this in my tubemaking with zero results. Oh well! Stick with the tungsten with the barium carbonate.
Thoriated tungsten is probably the way to go: much better work function than pure tungsten, and can recover after exposure to atmosphere.
Thank you.
Worked as a mass spectroscopist using GCMS, He leak detectors, and isotopic ratio mass spectrometers.
System pressures were 10 -8 microns or lower with a good vacuum.
Use dry nitrogen or argon to let the system up to atmospheric pressure.
This reduces pumping time.
Water from water vapor in the air is an enemy as far a getting a good vacuum.
You might get some vacuum gauges. A
1946 tube with a meter or a Pirani gauge is good for rough vacuums down to about 1 micron. For higher vaccums, use a hot cathode or a cold cathode vacuum gauge and controller.
Wow! Great video!
I worked for a vacuum furnace company. They would have two guys clean the inside of the entire furnace with alcohol prior to the first run up. This minimized the outgassing but took the better part of a day. It would take quite a while to pump down(rough out) the first time. One time the valve controlling the diffusion pump vacuum flow was installed incorrectly. The roughing pump pulled the oil out of the diffusion pump coating the inside of the furnace. If I remember correctly, it took several days to clean it all out.
I haven't used one of these since the 60s!
LaB6 emitters work well when exposure to air will occur. In fact, my picture is the LaB6 cathode in my plasma chamber!
Man, that vacume pump demonstration with the beads is awesome. I never understood why it was so hard to "get it all" I do know. Thanks.
I first encountered oil diffusion pumps in graduate school. Our Beckman ultracentrifuge had a standard reciprocating piston pump to get most of the air out of the chamber. Then you switched on the oil diffusion pump to get a very high vacuum. I'd never heard of such a thing before and was fascinated by how they function with zero moving parts. This was in the early 80s, no internet or Google back then so I had a bit of a job finding the information.
Great explanation. Whoever invented this... wow. "We could push those last few molecules out with vapor molecules we boil and move around right inside the chamber!" I bet the rest of the people standing around looked at them like they were nuts.
Very nice explanation. One of the hard limits of a diffusion pump is the back flow from desorption of the pump fluid. I've only worked with mercury pumps preferring a Balzer any day
CRT's are super cool. We need to get you into a glass blowing class so you can make a suitable neck, and play around more with your glass experiments. Awesome video as always, thanks!
cryogenic CRT ?
I worked with lots of cryos and turbos and lots of mechanical pumps even with Roots blowers boosting them but I never worked with diffusion pumps. Very interesting.
I am in need of a vacuum wood kiln. I was just reviewing Sprengel pumps and other less conventional pumps. Like you said the volume that needs to be evacuated makes these less practical. Especially when time is money. Awesome video as always. You are a fascinating dude.
Very nice video and beautiful pump! Gives me flashback to my PhD there we used a 50 liter diffusion pump to vacuum a huge high voltage discharge system. The stove was firmly attached to its bottom and the running tap water was used for cooling. The engineers told me that the hot oil would burn if no pre-vacuum created prior to heating it up.
That's because it lowers the boiling point
Interestingly enough I was reading into DIY CRTs just this week and got interested in it again. Now this video. Can't be a coincidence!
It's no coincidence. We're watching everything you do.
Great video again Ben. Given the complexity of pump I think one has to be a master glass blower to make one. Very impressive!
I worked where they mirrored glass on a machine that had a mercury diffusion pump, That thing could pull a vacuum in a 20 cubic foot chamber in like 5 seconds, then the aluminum filaments would start up and deposit onto the glass in about 5 seconds. It was very cool.
I didn't think heat was used in a mercury vacuum pump. I thought it worked by circulating the Mercury to the top of the system and letting it fall through a restricted opening over and over?
@@lvstofly You describe a Sprengel pump, which is not the same. Cody'sLab built one, there's a vid. A mercury diffusion pump works just like this oil version.
The diffusion pump by itself is amazing. But the CRT demo is awesome. That has to be the most simple vacuum tube i have ever seen. I had never thought of making one using more standard laboratory glassware.
Nice of us to show us your massive bong, Ben!
Wish I could have seen this made :) love functional glass
Fantastic! Thanks for showing. I used Diff pumps for almost ten years in EM but of course even servicing them you can't see how they work. Great idea to show everyone!
One of my many "One day i want to..." projects is an open source CRT display.
Was watching the how it's made and whatnot. Color is HARD with all the phosphors and grids (tech ingredients had a great series on this). But black and white (which may use multiple phosphors) or black and green, or black and red is easier. the hardest part is the phosphor coating i think (that and maybe digging for how to make a good electron gun).
Seems you are beating me to it to a certain degree! Best of luck, and i hope to do the same someday!
Waking up to this with a cup of green tea is delightful. Thank you for the explanation. Lab science has always been my favorite.
Dang that's a nice... diffusion pump.
Nice
...bong
Try using the filament assembly from a miniature T5 fluorescent tube - it’s pre-coated with emitter!
Probably contaminated with mercury.
Absolutly fascinating. Never thought about the gas molecules behaving differently at that pressure. The whole opaque thing makes sense now.
Thanks for showing the 2 failures at the end.
Thank you for this amazing video. I've always wanted to actually see what's going on in my metal diffusion pump. Now I know! The CRT is an astonishing achievement too, well done there. Barium carbonate is converted to barium oxide upon heating, and barium oxide would combine with with moisture from the atmosphere to form barium hydroxide so as you say quite rightly it cannot be subjected to the air once applied and heated.
Diffusion pumps are really interesting pieces of equipment.
The downside with them is that no matter what one does, they will always out gas oil into the chamber, due to the vapor pressure of the oil.
Though, for a lot of stuff, that isn't a major issue.
Worked with diff pumps for a long time. Cool to see one like this. Btw, you should have insulation near the heat source to prevent rapid cooling at the bottom. Also, with the plastic.. helium can penetrate some with no issue and it's even used to outgas helium (used as a carrier gas) from thicker material by pushing through plastic or PTFE loops.
The most beautiful kind of vacuum pumps.
Imagine how awesome it would be if your neighbor's garage had this going on! Never change Applied Science, never change!
the reason why they don't use diffusion pumps as a single stage is because the pressure difference that they create is pretty low. so this can (very roughly speaking) either get your pressure from 1 bar to 0.99 bar or from 0.01 bar to almost 0, that's why it makes sense to use a mechanical pump as the first stage to get you to that 0.01 in the first place.
These later episodes of Dr. Stone are absolutely lit!
Love your channel!
You are heating the diff pump oil too much, you do not want it to boil.
The correct temp is just where there is slight movement on the surface of the oil and the temp varies with the type of oil used.
702 = 180-190C
704 = 220-230C
Yes never ever use plastic tubing in vacuum systems - thick wall latex is acceptable.
Me? I used to be a high vacuum service tech.
I thought the same too
What is the result of boiling the oil? Less efficient pumping? More oil molecules escaping?
Also curious about the consequences of boiling the oil!
Does excessive heating crack the oil molecules into shorter ones?
@@hellelujahh Reduces the efficiency. The goal is the oil vapor streaming at supersonic speeds to impart its kinetic energy to gas molecules deflecting them down away from the inlet and compressing them. When you boil the oil the vapor streaming is chaotic, and if liquid oil droplets impede the vapor stream.
Being former electron microscope serviceman, you did make my day with this video.
Wow! This is really cool! As you can see from my TH-cam channel, I've been using diffusion pumps for many years, but never had the opportunity to "see" them in action! Great video! Thanks!
Electron microscopes tend to use either pure tungsten or a LaB6 (lanthium hexaboride) tip if they are purely thermally driven. This means they are easily user replaced in the lab and we dont have to handle sealed units when replacing the tip. Using your material for extra brightness would caus problems with that. Extra brightness is always nice but honestly, we burn through tips every few years, so replaceable is key. For extra brightness we tend to use a FEG (field emission gun) which draws electrons out using electric fields (with or without additional heating).
Really interesting video btw, having used oil diffusion pumps for years its nice to watch it working.
It’s amazing what percolation type stuff can do
Yup my bong is amazing man
Instant click when i see Applied Science. Definitely learned something too, as always
Never knew you needed that deep of a vacuum to get a cathode tube to work very interesting indeed 👌
this has to be one of the craziest youtube channels ever...
As a note;
Modem electron microscopes use lanthanum hexaboride emitters, and they have isolation valves such that the source never gets exposed to air. A separate vacuum backing for the source keeps it at very low vacuum (10^8 or better) and there are interlocks for vacuum level that must be closed before the sample chamber is opened to the source
Be, without the aquadag on the edge of the front of the tube you are probably getting some X-Ray leakage. I love the demonstration. Your channel is fantastic.
"Well, the reason I built the Hadron Collider in the basement was..." Answer in next weeks Applied Science video.
typical Friday afternoon
instructions unclear, accidentally built a Hardon Collider instead
I know this is a joke.... but... I'd actually be curious if he could build a particle collider (I'm almost certain he could).
I mean... he's done homemade superconductors.... I think a beam collider would be well within his ability. I think the only hard part would be creating some sort of detector to collect the collision products.
@@BRUXXUS -- Next week on Applied Science: "Hi guys. I've just started a "Go Fund Me" for a hadron collider. A few million bucks should suffice."
BRUXXUS A LINAC should be no problem I guess. :D
Everything about this video is insightful, amazing and fascinating at the same time. Very well explained too. Thanks!
The oil & chemical industries uses steam ejectors - those work off of the momentum transfer method too. Like the bottom of your diff. pump ejectors can be staged and the final pressure (vacuum) is determined by the overall compression ratio. I worked with those in the 90's and the roar of the steam was deafening.
Really cool! I think this is the first video that illustrates how diff pumps work that well on youtube. I actually seen one of those pumps in a store in Shanghai but didn't really think it can work (that well), given how small that inlet is.
That's some high-test screwing around right there.
I recently learned about turbomolecular pumps. The way it was explained is that you can wait for random motion of molecules or impart a specific motion on molecules to move them. High vacuum pumps do the latter.
Now THIS is exhilarating!
Great video as always! I didn't know that diffusion pumps came in glass! A lot of systems in the semi industry have moved away from diffusion pumps in favor of cryo or turbo pumps for achieving high vacuum in sensitive systems where any backstreaming(what you talk about around 5:37 ) could be catastrophic. If anyone wants to learn some more about vacuum systems "A User's Guide to Vacuum Technology" by John F. O'Hanlon is, from my understanding, the industry standard for vacuum systems. Certainly at a minimum quite a good resource. It was one of the required textbooks for my thin films class.
Thanks for the book recommendation!
I love this guy. A lot of what he does may seem unbelievable, but originally it was just other humans that figured it out so he says "I'm a human" and proceeds to apply science to demonstrate amazing phenomenon. Having some underlying education helps.
Of course it takes a dedicated individual to pull it off. I'm not trying to minimize his achievements at all. My overall point is all you need is the brain you were born with to do amazing things.
Ben: if MacGuyver were real, he would have a statue of you that he prayed to every night. You are amazing!
I cannot believe how much cool stuff is in there! I just learned about oil diffusion pumps and electron guns in the context of high-tech cryoEM and you just make all of this in your basement XD
Very cool video! I work at a high vacuum company, we use diffusion pumps large enough to fit inside. This is my first time actually seeing one operate. Its a concept quite difficult to understand with out a visual, I will be showing this to future recruits. I also liked your explanation of molecular flow in everyday terms.
I'd like to know what type of oil you used. And yes, too bad that particular pump was made with such poor conductance.
I'm not sure how difficult it would be to home build and Ion Pump? That would be very cool to see, and help you achieve UHV. Keep experimenting!
For some reason I found the tungsten trace quite lovely indeed! Bravo!
Maybe try heating the filament slowly and to a lower peek current.
I suspect the barium oxide is acting as an insulator allowing the tungsten to reach too high a temperature. Also, the barium carbonate could act as an oxidizer with respect to tungsten at high temperatures so best to decompose it slowly at a lower temperature.
Wanted to see inside an operating diffusion pump since I learned about the theory many years ago. Thanks for sharing!
thank you for educating people on this channel. I look for next video!
Fascinating..I've read about diffusion pumping..never worked anywhere that used it though... does look more finicky compared to the tmp and cryopump set up I'm more used to in commercial work.
I worked with an elektron-microscope which used an impeller-pump like the compressor side of a turbocharger to build a solid vacuum. Never heard of this pump, cool!
This was like "Applied Science meets Glasslinger" ..... I approve!
Next time Ben will have a dress on.
Eeehh... "Ben meets Dalibor" would be better
Did glasslinger ever finish his/hers?
It is really cool to be bale to see inside of the glass diffusion pump and watch the oil boil and condense. I just wanted to share some notes from my past experience with these and other high vacuum systems. The reason it is called a "diffusion" pump is because the gas molecules (mostly oxygen and nitrogen) bounce out of the vacuum chamber, into the body of the pump, and diffuse into the small oil vapor droplets that reach it up to the top of the pump. The pumping performance relies on gas solubility as a function of temperature. At the top, it is coolest where gasses are more soluble in the oil. At the bottom, it is hot where the gas molecules are less soluble and will be liberated as gas molecules. It is then up to the backing pump to take these liberated gas molecules away. Silicone oil is preferred since because of its higher gas solubility and because it is more stable for a long period of time. A diffusion pump that size should be around 800 W. I had a 900 W diffusion pump at my old place of work that was similarly sized albeit metal. After cleaning that 900 W pump with trichloroethylene and servicing its larger backing pump, I was able to get our 3 gal vacuum chamber down to 10^(-8) Torr - which is a typical ultimate pressure for diffusion pumps. The primary disadvantage of diffusion pumps is their pumping speeds and the contamination (like you mentioned). For these reasons, they are not used for semiconductor fabrication. Turbo pumps are most commonly used since they can pull a high vacuum very fast and don't use as much power as a diffusion pump. Cryo pumps are a little slower than turbos but offer the similar vacuum performance and are not prone to oil contamination. This is one of the reasons why cryo pumps are used on thin film deposition equipment in the semiconductor fabrication industry.
Anyone who can build a CRT using a flask, coils of wire, glow-in-the-dark paint and a broken lightbulb is a science hero...
Nice bong dude
Worked in high vacuum metalization for about 25 years we used to climb in some of them to clean them. Ours had bell covers that lifted when we hit a certain mbar. Boy tell you what them bells pop in atmosphere the heated oil would flash and the explosions was some kind of loud🤣 Make your ass jump anywhere in the plant. I’ve seen them blow hard enough to deflect the main shaft which were very thing stainless steel. This is a really cool model and I enjoyed this thoroughly. I have to show this vid to my brother this is too cool
Perhaps thE very best channel "out there" IMHO !
He just straight up made a TV from scratch for demonstration purposes! That is damn impressive.
About your claim that you don't technically need the roughing pump (at ~5:10). My experience is if the outlet of the diffusion pump is above a certain pressure, the oil in the diffusion pump increasess in volume (due to dissolved gas) and spills over into your system. The excess air pressure can also burn (oxidize) the oil making it char. This is a problem especially when the power goes out -- if it comes back on unattended, your roughing pump doesn't pump down fast enough, and the pressure is too high when the oil starts moving again.
Just nitpicking -- your videos are so cool!
I celebrate fixing my TV. Ben just makes his own.....
This would make a sick bong
Hollllllllly shieet. This is awesome. Those who have used them, know how awesome this is.
"Obviously, boiling mercury is not so great."
But let's work with barium. Um. Isn't that at least a little bit radioactive?
@@corwinweber693 Barium is not radioactive.It is even used as a contrast liquid, for example to take x-rays of blood vessels. Yes, then it is injected.
pizzablender It’s somewhat poisonous, though.
best understatement of the year 2020
@@GRBtutorials The useful stuff all is
I loved that . yes outgassing, araldite do low outgass epoxy, chrome , nickle are low outgass coatings. high vacuum is another beautiful world. I would love to see a lathe / mill made cryo pump.
My favourite hit or miss guy
I remember replacing a mercury diffusion pump on an ancient Joel SEM in college and replacing it with a turbomolecular pump. The original pump had a rather large quantity of mercury in it. The turbomolecular pump was wayyy quicker and took a lot less power during pumpdown. 🤓❤
That diffusion pump looks like a wicked water pipe
Hey Ben,
Just reaching out to you quickly, is it a way to reach out to you via email? I'd like to urgently collaborate with you on something.
Thanks in advance!
This is exciting.
@@Spit823 Indeed. Whatcha up to Louis?
Y’all definitely should. I’ve learned a ton from both of y’all’s channels.
That's a majorly impressive hunk of glass. 😯
As always, the awesomeness of this content is inversely proportional to the usability for my own little projects. Correction - make that inverse square.