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High School Cyclotron

  1. May 31, 2008 #1
    Hi, my name is Peter Heuer, I am a high school student and an avid reader of physics forums :)

    I have been working with two friends over the last year and a half to build a small cyclotron to enter in a science fair. We have completed our design but are having trouble funding the project.

    We have created a website here with more information, this can be found by goggling "cyclotron kids"

    If anyone has any ideas on how to fund such a project or comments on the idea in general, please let me know!

    The website has an email at which I can be contacted.

    Thanks!
     
  2. jcsd
  3. May 31, 2008 #2
    Hey
    Sounds like a very interesting and ambitious project. To get founding is maybe one of the greatest for scientific projects today. There are plenty of ideas but not always money ...
    I have unfournately no help to give you but I wish you good luck with the project and hope that you can find founding for it in some way.
     
  4. May 31, 2008 #3

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    I hate to be a wet blanket, but I believe your device is inherently unsafe, undercosted, and may not actually work.

    Safety: I see no mention of any sort of interlock. You need a design so that you cannot open anything you shouldn't with the system energized. (And if you do, the system automatically shuts off)

    Also, you argue that you use AWG14 wire because its rated for 15 amps, and your design is for 14 amps with 10% ripple. Not only does this provide only a 7% margin, once you put your 10% ripple on it, you are now driving it beyond its specs.

    My table says for power transmission, you need AWG10 (without any ripple); AWG14 is only good to 6 amps.

    You say that heat is not a problem - without calculations. That's not convincing.

    Finally, you have selected an energy high enough for nuclear processes to occur. So how do you know you haven't activated any of your equipment? And if it is activated, how do you plan on disposing of this radioactive waste?

    Cost: In real life, projects need "contingency" - what do you do if the price of copper goes up? Or you discover you need AWG10 wire after you started making coils of AWG14? No large project - from home repair to building a cyclotron - is immune.

    As an example, how do you plan to get the iron in the right shape? How do you plan to move and stack it? (Safely) This may well cost money.

    Will it work? You don't say how big your magnet is, but given that your box is 34 x 39 cm, I used that. 6000 turns is just over 28,000 feet. That means the coils have a resistance of about 70 ohms, which means you need about 1000 V to get your 14 A. You don't have that with your setup.

    Going to AWG9 will solve this problem, but of course it will increase your copper cost by a factor of 4, which will increase your cost by $4000 or so. (See the above on contingency)

    I think you would be better off building a smaller cyclotron. The original Lawrence one fit in the palm of your hand.
     
  5. May 31, 2008 #4
    Let me answer each of those questions at a time:


    "I see no mention of any sort of interlock. You need a design so that you cannot open anything you shouldn't with the system energized. (And if you do, the system automatically shuts off)"

    Because of time constraints, our entire safety system was not "prettied up" for the grant proposal and website. We do, however, have a design for a number of safety systems along this line. All of the electrical systems of the cyclotron will be in an enclosed space that is locked during operation (but still well ventilated by a system of fans. The system will also have a number of easy-access and automatic "fuse" systems that will shut down systems such as the magnets if overheating occurs or the hydrogen source if the vacuum level starts to fall.



    "Also, you argue that you use AWG14 wire because its rated for 15 amps, and your design is for 14 amps with 10% ripple. Not only does this provide only a 7% margin, once you put your 10% ripple on it, you are now driving it beyond its specs.

    My table says for power transmission, you need AWG10 (without any ripple); AWG14 is only good to 6 amps.

    You say that heat is not a problem - without calculations. That's not convincing."


    Again another item that was no covered explicitly in the online documents for time reasons (though I believe it was mentioned) is the cooling system for the magnets. There will be a system of copper tubing bringing cooled water over the coils at all times. In addition, we will only be running the cyclotron for short periods - a few seconds at a time - so magnet heating will be minimal anyway. These two considerations make the AWG14 wire safe.

    "Finally, you have selected an energy high enough for nuclear processes to occur. So how do you know you haven't activated any of your equipment? And if it is activated, how do you plan on disposing of this radioactive waste?"

    At all times the radiation level near the cyclotron will be measured and the machine will be turned off if any hazard is realized. Cyclotrons operating at much higher energy levels then ours (see the Rutgers link on our website) have had no problem with radiation and thus we don't expect to have any either. However, we have designed a a lead-covered box that the cyclotron will be placed in to minimize even this small chance.

    "Cost: In real life, projects need "contingency" - what do you do if the price of copper goes up? Or you discover you need AWG10 wire after you started making coils of AWG14? No large project - from home repair to building a cyclotron - is immune."

    This is true. However, this is an issue any project must deal with. We have had our design inspected by several physicists, all of which offered suggestions but also seemed to think it would work.

    "As an example, how do you plan to get the iron in the right shape? How do you plan to move and stack it? (Safely) This may well cost money."

    Our cyclotron was designed with this in mind. We have access to a machining shop and have obtained the skills/help to do what we need to. The yoke was planned in such a way that it can be assembled fairly easily on-site; no piece weighs more than 90lbs and they can all be put together with simple bolts. Again these designs are not online, if you are interested I can email them to you.

    "You don't say how big your magnet is, but given that your box is 34 x 39 cm, I used that. 6000 turns is just over 28,000 feet. That means the coils have a resistance of about 70 ohms, which means you need about 1000 V to get your 14 A. You don't have that with your setup."

    We have run through these equations multiple times; the results are on our web page. Our system uses 240V wall current through a large transformer to provide the watts we need. If an unexpected problem occurs, we can also change the windings on the transformer fairly easily to adapt this design to different amperages.

    "The original Lawrence one fit in the palm of your hand."


    The issue with the original cyclotron is that it did hardly anything besides prove that it worked. This was our original plan, however we soon realized that in order to justify the costs of the project we needed to make a cyclotron that could actually perform experiments outside of the area of cyclotron resonance.

    I hope that answered your questions. There is more information on all these systems in "draft" form that have not been scanned, however summaries of most of them are on the design document on our web page.
     
  6. May 31, 2008 #5

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    I still don't see an interlock system.

    Look at it this way. A cyclotron designed by professionals and operated by professionals has an interlock system. Should a cyclotron designed and operated by amateurs be designed with less safety in mind?

    You also argue that you won't operate it unsafely. To my mind, this isn't good enough - you need to design a system that cannot be operated unsafely. For example, if you think that the magnet should only be operated for a few seconds, put a timer on it so it automatically shuts off.

    You mention that you didn't have the time to put some of this on the web - I think you can't afford not to. Nobody is going to put money or resources towards getting three kids killed, so it's to your advantage to have a well-designed safety system and to publish the details. It's up to you to convince your potential donors that this won't happen.

    As far as prompt radiation, you have to tell me how much is "too much", how you are going to detect it, whether the response is manual or automatic, and so on. But I am more worried about activation - having the beam make some part of the cyclotron radioactive. Even if you immediately shut off the beam, it's too late. "The other guys didn't have a problem" is not a particularly compelling answer to a safety-related question.

    As far as your magnet, I don't see a drawing of it or a table of its properties. I can't tell how much wire you need. The best I was able to do was to figure out how much wire you are buying from the weight and density of copper, and that's 12000 feet. So I was off by a factor of ~2 (not bad, considering there's no drawing). That's 30 ohms, and to support 14 A requires 420 V. Your transformer only gives 340 V. You say that that you've done these calculations multiple times - fine. Put them on the web site. Including this particular calculation.

    Changing the windings won't help. You've designed a 6 kW magnet (before losses - it's probably closer to 7 with losses), and it's ultimately getting plugged into a 4.8 kW source.

    You also have a problem with operating it for just a few seconds at a time. I don't know what the inductance is - 300 H maybe? 300 H and 30 ohms gives you a time constant of 10 seconds. That means it will take ~45 seconds just to get the magnet to full (99%) power - and another 45 seconds to bring it back to zero.

    You also didn't address the fact that your own design (14 A + 10% ripple) exceeds what you say is the safe current limit for this wire. Even if you ignore my arguments for thicker wire, your own numbers say you're exceeding the safe current limit.
     
  7. May 31, 2008 #6
    The first mistake you are making continually is to assume that the complete design is on the website. Again, due to time constraints we have not made presentable circuit diagrams/descriptions of the interlock systems.

    Our "potential donors" are getting different information. Many of our tech drawings for the chamber/magnet design do not scan well; we send potential donors copies by mail. You should understand that the website is made with the average person in mind, not a scientist. Thus we have tried to keep most of the complicated stuff in our actual funding proposals.

    I'm not sure how you are arriving with 30 ohms, I believe our calculations yielded 21 ohms which, although close, is possible.

    It is true that inductance is large, however we are confident that the cooling system will work. Even if it does not, it is not a safety hazard; all it will do is trip the automatic shut down system.

    I would like to see the table you are citing. However, the information on Fred Neill's website (a previous high school cyclotron builder) agrees with our numbers. He made, in fact, a fairly similar, if smaller magnet.






    At the level of 1.35 MeV,
     
  8. May 31, 2008 #7

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    Hey, I can only go by what you've posted, here and the site. If what's on the site is wrong or incomplete, you should fix it.

    For example, you've said 14 amperes average, you've said 10% ripple and you've said 15 amperes is the safe limit. Using your numbers and only your numbers, I get that your current exceeds your limit. Which number is wrong? 14? 15? Or 10?
     
  9. May 31, 2008 #8
    Both numbers are correct. The 15 amp safety limit is meant for every-day appliances etc. like household wiring. Since our system is cooled, insulated with enamel instead of thick plastic and running for a matter of seconds at peak, we can stretch that number a little bit.

    By the way, the magnets will be turned on slowly so that they can "warm up" at least part of the way below the max. current.
     
  10. May 31, 2008 #9

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    Deciding that you don't have to follow the safety limits on a piece of equipment - even something as simple as a piece of wire - is very dangerous.

    Accidents happen not because people do things they think are dangerous. They happen because people do things they think are safe - but aren't.

    Since it's clear your mind is made up, and that you won't take any safety commentary seriously (even by someone who has been doing accelerator physics experiments for the last 20 years), I guess all I can say is, "Good luck, be careful, and I hope you don't kill yourselves."
     
  11. May 31, 2008 #10
    I'm not sure why you think I won't take advice, I've been double checking my numbers and tables for the last half hour.

    I am still interested in seeing a link/copy of the table you are citing for your numbers. Although I remain convinced that a cooled magnet can safely exceed the recommended running temperature for cold wire (for what other reason would you cool it?) I would be much more worried if your 6 Amp figure was applicable.

    If the temperature switch flips, we can simply run the magnets on a lower current. The overall output particle velocity will of course be lowered but I would prefer that than to not build the accelerator at all (12AWG wire is vastly more expensive.)
     
  12. Jun 1, 2008 #11

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    One more question - have you acquired a license to operate such an accelerator in your state? While I am not a lawyer, it appears that the threshold in both New York and Maryland is 1 MeV. (Other states have different thresholds: I believe it's 100 keV for Pennsylvania)
     
  13. Jun 1, 2008 #12
    You might consider a test with just the magnet and coils. Apply the power you expect, make temperature, voltage and current measurements over time. Chart the results, and see what you get. You may wish to apply cooling and run a test.

    Test or not you will probably want the ability to monitor muliple sensors at a rapid rate and record the data. Implementing that at an early stage would probably be benificial.
     
  14. Jun 1, 2008 #13
    Posting your full designs and calculations would probably make potential donors more apt to give you money. Personally I've been terrified of radiation of any sorts since I turned on a microwave with the door open (my dad had it in his appliance work shop -- I was little, and didn't realize he had bypassed the door saftey switch!) So just the idea of "being possible to operate unsaftely," scares me. Safety first!

    Anyway, but, you know, a few big donations is one thing, but many small ones can be just as effective. You're kinda snubbing out smaller donors by not having your information up.

    And one other thing... have you thought about FedEx/Kinko's? I've been there a couple of times for special prints, I recall seeing a jumbo scanner linked to their computer network.
     
  15. Jun 1, 2008 #14
    1. We were unable to find any such legal restriction in our search, if you find anything PLEASE send it to us. We have determined that we seem to be safe legally in at least the radiation laws, however since none of us are lawyers it is possible we may have missed something.

    2. We will DEFINITLY test the magnets and all other systems before they are used with the actual cyclotron. I should also stress that THE INTERLOCK WILL DISABLE THE MAGNETS/HV SOURCE IF THE ELECTRONICS LOCKER IS OPENED. This will prevent accidents from happening.

    3. If you look, most of our information IS up, all that isn't are the scans of our tech drawings since they are not very good quality and can not be read easily without zooming in a lot. Kinkos was the first place we looked, however those scanners have a HUGE price (like $5 per square foot) for the output, making our total costs for that over $60 for something we could simply describe.
     
  16. Jun 1, 2008 #15

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    You can find links to the various state rules here.

    For Maryland, the appropriate law appears to be the Code of Maryland Regulations 26.12.01.01
     
  17. Jun 1, 2008 #16
    Thank you very much, I will look into that now.

    I want to let you know that, after checking the math and considering we have decided that AWG 12 wire would be a better choice. Thank you for your information.
     
  18. Jun 1, 2008 #17
    A search of the that legislation seems to read that that limit only applies to those devices that are being used in "the healing arts"
     
  19. Jun 2, 2008 #18

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    This is why it's worth spending some time and getting professional assistance in dealing with these laws. (Which may include writing a letter to the appropriate state agency, it may involve getting in touch with some local university's RSO, and it may even require a lawyer).

    The key seems to be Sec. I2: "No person shall receive, possess, use, transfer, own, or acquire a particle accelerator except as authorized in a registration issued pursuant to Part B of these regulations"

    Exemptions (Part B) are: "(a) Electronic equipment that produces radiation incidental to its operation for other purposes is exempt from the registration and notification requirements of this Part, provided that the dose equivalent rate averaged over an area of 10 square centimeters does not exceed 5 μSv (0.5 millirem) per hour at 5 centimeters from any accessible surface of such equipment. The production, testing, or factory servicing of such equipment shall not be exempt. (b) Radiation machines while in transit or storage incident thereto are exempt from the requirements of this Part. (c) Domestic television receivers are exempt from the requirements of this Part."

    That said, the only license form I saw was probably the one you found. However, I also suspect that most requests are from hospitals or their service providers. Not people wanting to build accelerators in their basements.

    While I am not a regulator, I can't imagine that you will be held to a lower standard than a professionally constructed and operated accelerator, so I think you should be prepared for that.
     
  20. Jun 2, 2008 #19
    Nor would we want to to, I'd rather have to change our design to comply with laws then be fried.

    We have discussed hiring a lawyer, at least for a consultation, but we were concerned that your average lawyer would no nothing about these somewhat obscure rules. Do you have any idea how to go about finding one that would know the laws in this area?
     
  21. Jun 3, 2008 #20

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    There are specialists in environmental law, which would be appropriate. But I'd start with writing the state agency and see what comes back: "you're OK of you keep it under an MeV" or "over my dead body".
     
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