Build my own mass spectrometer?

[leright]

I am a double major in EE and physics and I was thinking that a great senior project would be to design and build my own mass spectrometer. I would not only like to build the basic device, but also calibrate the device so that it provides the m/q value based on the radius of curvature caused by the B-field, and also provides the relative abundance of these m/q values, like a real mass spectrometer. I would like this to be displayed on an LCD screen of some sort possibly.

I have a good understanding of how mass spectrometers work and it seems like this is feasible. Am I out of my mind? I have 2 years before my senior design project is due, and I think I am going to get started on my project very soon. I plan on designing all of the power electronics (such as the rectifier and ripple voltage reduction circuitry) myself. Any advice or suggestions?

I want to find a project that is heavy on the E&M calculations since it is one of my favorite topics, and this came to mind. It seems like an exciting endeavor.

Thanks.

 

[Rach3]

This is in the wrong place - it probably belongs in one of the engineering forums.

 

[leright]

oops. Could someone move it over to there please?

 

[Rach3]

Have you worked with high vacuum before? You need that for MS or anything with ions - my understanding is that's its extremely tough to work with. And expensive.

 

[leright]

Have you worked with high vacuum before? You need that for MS or anything with ions - my understanding is that's its extremely tough to work with. And expensive.

Nope. Never. I suppose I am a complete novice and I have lots of learning to do.

As far as money goes, I think I am willing to spend n more than 3000 dollars on my senior design project, and my university might provide some funding also. And even then, 3 grand is pushing it... more realistically around 1 grand.

 

[leright]

anyone have experience with this? Is a system that generates high vacuum easily constructed, or is there a lot of expensive equipment I'd need to buy? Ideally, I would like to design and build as much as possible from scratch. I suppose I would need all kinds of specially treated materials, low vapor pressure materials, very dry conditions and many many high powered vacuum pumps, correct?

Perhaps this problem is one where an engineer would be more capable of answering than a physicist. It does seem more like an engineering problem, for the most part. Maybe it should be in one of the engineering forums.

 

[leright]

anyone want to offer any criticism to this idea, or pointers? Is this a reasonable endeavor for an undergrad. I have around 2 yrs to do this project.

 

[leright]

I suppose I will post this in the general engineering forum.

 

[nbo10]

You need to find an advisor that will let you work in and use his lab. Otherwise you're looking at an extremely expensive project. And you're going to need a machine shop. Look through Review of Scientific Instruments and I'm sure there are a few decent book out there.

 

[Manchot]

Is a system that generates high vacuum easily constructed, or is there a lot of expensive equipment I'd need to buy?

How much vacuum are we talking about? If you only need to get down to about 50 mTorr, you can probably get away with a mechanical roughing pump. They're expensive, but they're not that expensive. If you need to go lower than this, you'll start running up costs like crazy. In that case, you'll need another pump (in addition to your roughing pump), such as a cryo-pump, a diffusion pump, or a turbomolecular pump. It doesn't matter which you pick: they're all well outside of your price range (usually $10k and up).

EDIT: I just found a used diffusion pump on eBay for $500. I guess I was wrong about that.

 

[leright]

How much vacuum are we talking about? If you only need to get down to about 50 mTorr, you can probably get away with a mechanical roughing pump. They're expensive, but they're not that expensive. If you need to go lower than this, you'll start running up costs like crazy. In that case, you'll need another pump (in addition to your roughing pump), such as a cryo-pump, a diffusion pump, or a turbomolecular pump. It doesn't matter which you pick: they're all well outside of your price range (usually $10k and up).

EDIT: I just found a used diffusion pump on eBay for $500. I guess I was wrong about that.

I am thinking along the lines of 0.5 microTorr in this application.

 

[Gokul43201]

leright, before you commit yourself to thousands of bucks worth of vacuum equipment (for the traditional approach, you'd likely need a roughing pump backing a turbo pump), you might want to read this recent article: Hao Chen, Zheng Ouyang, R. Graham Cooks, "Thermal Production and Reactions of Organic Ions at Atmospheric Pressure" Angewandte Chemie, 118(22), 3738 (2006)

(the link to interscience does not seem to work right now - you could email Chen for a copy of the article)

 

[leright]

Thanks Gokul. I have read this artcle http://www.physorg.com/news64203374.html

It is quite interesting, but I will still need to work with high vacuum in the mass spectrometer itself. Also, this technique does not produce fragment ions, which, imo, is a downside in this application. The fragmentation ions tell a lot about a compound if it is unknown.

 

[Manchot]

0.5 microTorr? I don't want to say that it's impossible with off-the shelf parts, but you'll be spending a lot of money, and I'm afraid that it's probably out of your price range. Aside from your roughing pump and your turbo/diffusion/cryo-pump, you'll also need something like a thermocouple to measure pressures in the mTorr range, and something like a cold-cathode or ionization gauge to measure pressures in the microTorr range. That's without considering the difficulty you'll most have sealing your device from atmosphere, which absolutely loves to permeate everything. (Trust me on this: I know all too well.)

Does your university have a clean room where they do semiconductor work? If they do, they most likely have an evaporator or two in there that can pump down to the nTorr-microTorr range, as well as someone who knows lots more about vacuum systems than I do. You might want to make an appointment with him or her to discuss your options, and to point you in the right direction.

 

[Gokul43201]

Or, you can walk to the nearest Analytical Chemistry lab on campus and speak to the Mass Spec technicians there.

Do you have a budget?

 

[leright]

Or, you can walk to the nearest Analytical Chemistry lab on campus and speak to the Mass Spec technicians there.

Do you have a budget?

I go to a fairly small university (~5000 students) and the chemistry program is roughly 50 students. The "mass spec technician" would be one of the professors. We have one mass spectrometer, one NMR, one IR spectrometer, one electron microscope, one gas chromotograph, etc. We have only one of everything. It's not like we have entire labs with just mass spectrometers, so there is no need for a "mass spectrometer" technician. However, I will talk to some chemistry professors to see what they say. I they just give me a weird look or something, I will know this is outside my skill level and budget. :p

 

[leright]

0.5 microTorr? I don't want to say that it's impossible with off-the shelf parts, but you'll be spending a lot of money, and I'm afraid that it's probably out of your price range. Aside from your roughing pump and your turbo/diffusion/cryo-pump, you'll also need something like a thermocouple to measure pressures in the mTorr range, and something like a cold-cathode or ionization gauge to measure pressures in the microTorr range. That's without considering the difficulty you'll most have sealing your device from atmosphere, which absolutely loves to permeate everything. (Trust me on this: I know all too well.)

Does your university have a clean room where they do semiconductor work? If they do, they most likely have an evaporator or two in there that can pump down to the nTorr-microTorr range, as well as someone who knows lots more about vacuum systems than I do. You might want to make an appointment with him or her to discuss your options, and to point you in the right direction.

I doubt my university has anything like that. However, I remember back a long time ago, during university chemistry, a professor showed us a simple mass spectrometer. It really didn't look too fancy. The real mass spectrometer we have is a quite large machine and quite expensive, but the one I was shown by a prof was quite simple looking...not REALLY simple, but it looked like something I could build.

 

[Gokul43201]

I go to a fairly small university (~5000 students) and the chemistry program is roughly 50 students. The "mass spec technician" would be one of the professors. We have one mass spectrometer, one NMR, one IR spectrometer, one electron microscope, one gas chromotograph, etc. We have only one of everything. It's not like we have entire labs with just mass spectrometers, so there is no need for a "mass spectrometer" technician. However, I will talk to some chemistry professors to see what they say.

Professors may be busy or unavailable (or may not know much about the technical challenges involved in building a mass spec). If you can talks to a prof that can help you, great! But you might also ask your prof if the dept has someone (in more of a technical capacity) that is responsible for maintenance of various instruments. Smaller depts will often hire one such person.

 

[amk12]

Hey,
Did you end up building the mass spectrometer? Any updates?

 

[leright]

Hey,
Did you end up building the mass spectrometer? Any updates?

No, I decided to bail on the idea. :)

 

[amk12]

I am sorry to hear that. I was actually looking into something similar for my senior design, but I guess it is too hard to accomplish.
Best luck!