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LAN_403

Carbon_Rod

Sun Aug 20 2006, 03:20AM

Registered Member #65 Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155

Awards, citations, and rank get dropped in here very rarely. Many members would surprise you with their backgrounds and level of experience.

Actually there were studies done with shielded spacecraft that found some secondary radiation sources caused more DNA damage than normal exposure levels. A little off topic I know â€“ but still notable if you plan on testing shielding.

A pulse system may work under certain constraints if it is a single stage accelerator â€“ however from the vague description the generated beam will likely be inconsistent in its behaviour. Some meter based Geiger counters may integrate ambient exposure levels if the spike in levels is too intermittent. So the meter may falsely show lower than normal exposure. The name-badge unit advice is rather brilliant and inexpensive.

It seems rather curious for reproducible experimental use. However it does sound like an interesting project.

Good luck,

Simon

Mon Aug 21 2006, 12:56AM

Registered Member #32 Joined: Sat Feb 04 2006, 08:58AM
Location: Australia
Posts: 549

NeilThomas wrote ...

Rather than worry about integrating force and suchlike, go for the easy route and consider energy. Once the electron has fallen through 100kV, it will have an energy of 100keV. I think this is still non-relativistic speed, so if you want the velocity from this just invert E=1/2mv2 (in consistent units of course), where m is the electron rest mass.

The rest mass energy of an electron is 511keV. Since the 100keV electron kinetic energy is a fifth of the rest mass energy I really would consider relativity applies. That's not too hard. Gamma = (511keV + 100keV) / 511keV = 1.20. So time and space will affected by a factor of about 20%.

If you want to work out the velocity, solve for Gamma = 1 / sqrt(1 - B^2), where B is the proportion of the speed of light (.5 = half speed of light = 1.5 x 10^8 m/s).

I don't think any of that will help you design the system but it's worth understanding.

As to x-rays, yes you'll definitely get them at this energy. You should do a little research if you weren't aware of this before.

Sulaiman

Mon Aug 21 2006, 07:39AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Simon,
I don't understand your maths/formula
e.g. for a 50 MeV accelarator, Gamma = 100
what does this mean physically?

attune

Mon Aug 21 2006, 04:40PM

Registered Member #259 Joined: Sun Feb 26 2006, 05:57PM
Location: Friday Harbor, Wa
Posts: 18

Sweet! I was not aware that the effect of relativity was significant at this velocity. 511kV is within Marx capability...if such a voltage were applied to an accelerator, no matter what particle was being accelerated, would new electrons be created?

Bored Chemist

Tue Aug 22 2006, 06:00AM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

You need at least twice that.

Dr. Slack

Tue Aug 22 2006, 07:27AM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

e.g. for a 50 MeV accelarator, Gamma = 100
what does this mean physically?

What does anything mean physically, especially when it goes relatavistic or quantum? For me, physically only works for good ol' Newton, relativistic mechanics gives that queasy feeling of having to imagine riding on electrons and seeing the world foreshortened in your direction of travel, and other easy-to-do things (not). In your frame of reference (stationary standing next to the accelerator), it means the electron has got heavier by the Lorentz factor (related to gamma by a sqrt)

Gamma as used/defined above is just (total energy) / (rest energy). For a good Newtonian approximation, gamma is close to 1, the higher it goes the less adequate Newton is.

There's a good reason for just considering energy, rather than speed, force or aceleration in acceletrators. Once gamma is into double figures, the particles barely get any faster, just get heavier as they absorb more energy.

I'd like to think that muons generated in the upper atmosphere by cosmic particles reach the surface of the earth in spite of their short lifetime not because their clocks run slow, or the atmosphere appears shorter in their direction of travel, but because they are actually travelling faster than light and somehow we contrive to measure it wrong, but, particles in a circular accelerator keep going round at the same speed as the energy goes up, and that configuration is much more difficult to mis-understand.

Simon

Wed Aug 23 2006, 03:56AM

Registered Member #32 Joined: Sat Feb 04 2006, 08:58AM
Location: Australia
Posts: 549

Sulaiman wrote ...

Simon,
I don't understand your maths/formula
e.g. for a 50 MeV accelarator, Gamma = 100
what does this mean physically?

It's very simple, contrary to what most people expect of special relativity (it's general relativity that's hard). Simply put, gamma is the factor by which relativity does weird things.

For a 50MeV electron (gamma ~= 100) shooting down a 100m pipe (as measured by someone standing next to it), the distance would only seem like 1m. If it took 100 years to travel to a distant star (as measured by someone at the star), to the electron it would only seem like 1 year.

As to the idea of sticking 511kV somewhere and generating an electron, remember that my chocolate bar doesn't spontaneously burst into a gazillion electrons just because there's enough energy for it.

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