# The building of a proton accelerator

Regards

#### James Jackson

ZapperZ, I'm well aware of that thanks. I was replying to the post that said 'some kid build an accelerator in his house', not the OP (which I've alread replied to).

#### ZapperZ

Staff Emeritus
2018 Award
dlgoff said:
It's possible that he could make a small Van de Graff and use inonized hydrogen as his proton source.

But probably not for $400. Regards No, not even with$1000. I still think he doesn't know what he's getting himself into. Here's why:

1. How does one ionize hydrogen? It's one thing to have H2 gas in a discharge tube to cause an excitation and view the transition lines. It's another to completely strip off the electron.

2. Not only that, you have to strip the electron with enough energy so that you have the chance to separate them out. So how do you maintain the ionized H's long enough to accelerate them?

3. Once you get that, you realize that to make any significant transport, you have to be in ultra-high vacuum (better than 10^-10 Torr). This is more crucial for protons than electrons since protons are way larger and has a large scattering cross-section than electrons. UHV pumps are NOT cheap.

4. Even when you accomplish that, this is a very HOT process. The protons will have very high momentum in all directions. Even if you put them in a uniform field, the transverse momentum will still be there and will, sooner or later, cause the protons to hit the walls.

5. You can minimize Point 4 using solenoids and steering coils, but hey, this now requires high current power supplies to work those solenoids and steering coils. This is not even a $10,000 project - it is way more. 6. If you have managed to overcome Problems 1,2,3, 4 and 5, then be prepared for radiation sickness sooner or later. Fast protons (not even high energy) hitting materials such as stainless steel, etc can cause the material to become "hot". The residual radiation from these can stay for a long time (people who work in proton colliders cannot go into the detector for hours and even days after shut down). Like I said, I don't think this person knows what he's getting himself into.... Zz. #### juvenal #### dlgoff Science Advisor Gold Member ZapperZ said: No, not even with$1000. I still think he doesn't know what he's getting himself into. Here's why:

1. How does one ionize hydrogen? It's one thing to have H2 gas in a discharge tube to cause an excitation and view the transition lines. It's another to completely strip off the electron.

2. Not only that, you have to strip the electron with enough energy so that you have the chance to separate them out. So how do you maintain the ionized H's long enough to accelerate them?

3. Once you get that, you realize that to make any significant transport, you have to be in ultra-high vacuum (better than 10^-10 Torr). This is more crucial for protons than electrons since protons are way larger and has a large scattering cross-section than electrons. UHV pumps are NOT cheap.

4. Even when you accomplish that, this is a very HOT process. The protons will have very high momentum in all directions. Even if you put them in a uniform field, the transverse momentum will still be there and will, sooner or later, cause the protons to hit the walls.

5. You can minimize Point 4 using solenoids and steering coils, but hey, this now requires high current power supplies to work those solenoids and steering coils. This is not even a $10,000 project - it is way more. 6. If you have managed to overcome Problems 1,2,3, 4 and 5, then be prepared for radiation sickness sooner or later. Fast protons (not even high energy) hitting materials such as stainless steel, etc can cause the material to become "hot". The residual radiation from these can stay for a long time (people who work in proton colliders cannot go into the detector for hours and even days after shut down). Like I said, I don't think this person knows what he's getting himself into.... Zz. When I was an undergrad, I worked with a 2Mev Van de Graff that had been donated to the University by the then Atomic Energy Commission. We could strip electrons with RF on both hydrogen and helium (4Mev in this case). We used a crude 1024 channel analyzer to gather data from photomultipler tubes detectors. Maybe some day he'll be luck like I was and get to work with and see an accelerator. Regards #### ZapperZ Staff Emeritus Science Advisor Education Advisor 2018 Award dlgoff said: When I was an undergrad, I worked with a 2Mev Van de Graff that had been donated to the University by the then Atomic Energy Commission. We could strip electrons with RF on both hydrogen and helium (4Mev in this case). We used a crude 1024 channel analyzer to gather data from photomultipler tubes detectors. Maybe some day he'll be luck like I was and get to work with and see an accelerator. Regards Exactly. You just don't need something with 13.6 eV to strip off an electron off a Hydrogen if you want to obtain a bare proton. You need something orders of magnitude bigger! That's why I brought up Point 2. I think your last point is what is missing in most people that either do not fully understand how science works, or do not understand what is involved in something like this. People should grab every opportunity they can when there's a chance to see an actual scientific facility and talk to people who do these things. I have highlighted this, but if anyone is in the NYC/Long Island area, you will miss a wonderful opportunity if you do not go to one of Brookhaven's Summer Sunday Tours. See what is involved in doing meticulous, careful science, and see how wide of an area that is studied in just that one laboratory. http://www.bnl.gov/community/summer_sunday.asp One might even get to see an accelerator or two there. Zz. #### James Jackson CERN do summer schools... I wouldn't be surprised if SLAC didn't too. #### mmisk Bnl ZapperZ said: One might even get to see an accelerator or two there. Zz. I have a dozen pics I took at BNL in fall of 2003, I think it was just after the first RHIC run. If anybody wants I can put on a website. #### Cyclotron Boy Yep- that linear accelerator was indeed my first accelerator project. It involved extremely high voltages and vacuums, both of which can be dangerous. But most dangerous of all was the enormous amount of X-rays I was producing with my machine. Constructing a linear accelerator is quite difficult, and a good overview of the entire process is available in "The Amateur Scientist" by C. L. Strong, 1960. The book has an article from the Amateur Scientist column in Scientific American outlining the construction of a static-electricity driven electron accelerator. With the addition of a ion gun, a proton accelerator would be feasible, but extremely difficult. My first machine took over a year of my "free time" to complete. The other machines took even that much more time. It is important to examine both the scope of the project and your own dedication to the project before starting anything as difficult as a particle accelerator. -Fred #### cscott mmisk said: I have a dozen pics I took at BNL in fall of 2003, I think it was just after the first RHIC run. If anybody wants I can put on a website. I would love to see them! #### mmisk Here are some BNL pictures from October 2003. Sadly even this isn't really 'made in the USA' - most of the metal came from Russia. http://www.rant.st/snowboarder/BNL/BNL.html [Broken] Last edited by a moderator: #### dlgoff Science Advisor Gold Member Outstanding mmisk. Thanks for posting them. #### CarlB Science Advisor Homework Helper Gosh, if I wanted to ionize hydrogen I think I could do it a lot cheaper than$400. Of course you're going to have to find a lot of parts at your local scientific salavage yard, and you will be risking your life in the process of building the thing.

It turns out that when I was in college I helped maintain equipment that created plasmas, which are combinations of ions and electrons. When you make a plasma out of hydrogen gas, what you end up with is first atomic hydrogen ions, and later, after you knock the extra hydrogen off, protons.

First, get a (very low pressure) more or less pure hydrogen atmosphere. Second, put a probe out in the middle of it with an extremely sharp point on it. Third, put a high positive voltage on your probe. The sharp point will create an extremely high electric field and this will ionize whatever gas is around.

The result of all this will be a steady flow of electrons into your probe and ions (protons) away from it. The protons that get created by the ionization will be attracted towards the negative plate and this will be the beginning of your beam.

To learn how to do this, in a practical manner, it would be best to first learn about vacuum tubes. Take a good look inside some, and when you've read enough to recognize what a "plate" and a "cathode" looks like, you're ready to start thinking of your own designs. Of course you'll probably be building in stainless steel rather than glass. That means learning how to run machine tools could be useful.

Once you get your source of hydrogen ions (as described above) you need to accelerate them and strip off the neutral hydrogen. The way this is done is with dangerous high voltages and various magnetic and electric fields.

The basic idea is to make everything you don't want go away by arranging for it to collide with some sort of "beam stop". For example, hydrogen ions weigh more than protons, but they have the same charge. So at the same energy (i.e. number of volts you've accelerated them by) they tend to travel straighter in a magnetic field. So you leave a free curved path for your protons to curve around, but your hydrogen ions go more straight, hit the walls and are turned back into neutral hydrogen.

To get all the diffusion pumps and stuff, you need to hang around at auctions and surplus yards. This stuff regularly gets thrown away for scrap prices. Check out your local large University, they may have a monthly auction or a salvage yard. Probably the perfect situation would be to work at a metal reclamation yard near a large scientific establishment. You'll get all kinds of incredible equipment for free.

Carl

#### WhiteWolf

In high school, Michio Kaku built his own particle accelerator around the football field over the Christmas break. According to him, it did usually blow every fuse in his house.

No, not even with $1000. I still think he doesn't know what he's getting himself into. Here's why: 1. How does one ionize hydrogen? It's one thing to have H2 gas in a discharge tube to cause an excitation and view the transition lines. It's another to completely strip off the electron. 2. Not only that, you have to strip the electron with enough energy so that you have the chance to separate them out. So how do you maintain the ionized H's long enough to accelerate them? 3. Once you get that, you realize that to make any significant transport, you have to be in ultra-high vacuum (better than 10^-10 Torr). This is more crucial for protons than electrons since protons are way larger and has a large scattering cross-section than electrons. UHV pumps are NOT cheap. 4. Even when you accomplish that, this is a very HOT process. The protons will have very high momentum in all directions. Even if you put them in a uniform field, the transverse momentum will still be there and will, sooner or later, cause the protons to hit the walls. 5. You can minimize Point 4 using solenoids and steering coils, but hey, this now requires high current power supplies to work those solenoids and steering coils. This is not even a$10,000 project - it is way more.

6. If you have managed to overcome Problems 1,2,3, 4 and 5, then be prepared for radiation sickness sooner or later. Fast protons (not even high energy) hitting materials such as stainless steel, etc can cause the material to become "hot". The residual radiation from these can stay for a long time (people who work in proton colliders cannot go into the detector for hours and even days after shut down).

Like I said, I don't think this person knows what he's getting himself into....

Zz.
It is possible to build a smaller scale project, why does it have to be so large and expensive. I was looking into doing this also and it was suggested to build a synchrocylotron they have been build as small as 30 cm in diameter. I dont know what the cost of parts is, but I'm sure its more in your range.

Staff Emeritus

This thread is four years old.

We're trying to tell you the same thing in the thread you started - this is not cheap. Ultra high vacuum systems run thousands of dollars, and without one, your beam won't get very far. You got on my case for "being negative" when I pointed this out, but it is nonetheless true.

#### hamster143

Staff Emeritus
While I agree 10^-10 is more than is needed, I don't think 10^-6 is good enough. That gives you a mean free path of around 100 meters, so if you go with 1/10 of a mean free path, that's 10m - around 10 turns of a frisbee sized machine. If you don't want an enormous voltage on the accelerator, that's not enough: I'd say you need a few x 10^-8 torr.

I'm not an expert on vacuum, but this seems to me to be pushing what a diffusion pump can do: I'd go with an ion pump or a turbopump.

#### hamster143

A few points:

- "frisbee sized" is actually quite big for a cyclotron. The Rutgers system referenced in the other thread is about that size (r_max = 5 inches).
- Don't forget that radius increases with energy, you have to correct for that. Path ~ 2/3 * revolutions * circumference.
- 50 revolutions with 100 VAC between electrodes should get protons to 14 keV, which is IMHO quite respectable. In a 5-inch chamber, 50 revolutions would be equal to the total path of 27 m or 0.27 of a mean free path.
- If the vacuum is not good enough, you're going to lose output current. At a 0.27 of a mean free path, you'd lose 25% of protons. Depending on the initial current, and depending on what you do with protons once they are accelerated, you could still see output at 3x - 5x mean free path.

This is all theoretical, though.

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