Dr. Syphers,
I have heard a lot of concern about black holes resulting from an atom smasher. I understand that these black holes would be of little consequence due to size and stability, but you mentioned to another student that they would quickly "evaporate." How can a black hole evaporate... actually, what exactly IS ia black hole?
Thanks,
Lindsay
P.S. Thanks so much for your time, which this project must have taken a lot of. Your answers were very complete and I feel like I have a greater knowledge about supercolliders and such. I really enjoyed getting to ask you questions, so thank you!
----
Thank you Lindsay,
About 100 years ago, Albert Einstein developed a new theory called the General Theory of Relativity. The theory describes how particles and light behave in reference frames that are accelerating. In particular, the theory shows that gravity can actually be thought of as space and time being "curved" by the presence of mass and energy. Thus a large star curves space around it and planets and spacehips traveling nearby will follow trajectories in space and time due to this curvature. For most "ordinary" cases, it gives the same results as Newton's old theory of gravity -- elliptical orbits, and so forth. However, Einstien's new theory was even more successful, as it explained why the planet Mercury's orbit seemed to "precess" in a way that Newton's theory of gravity couldn't explain. The theory also predicted that light rays will actually be "bent" in a strong gravitational field. This was soon observed to be true through measurements made during a total solar eclipse, and Einstein became world famous overnight!
Anyway, this same theory predicts that if there is enough mass and energy in one place in space, the gravity can be so strong -- space-time can be so curved -- that nothing can get away from the object, not even light. Since light cannot escape this region, it is called a "Black Hole." It requires a great deal of mass in a very small region of space. To date, there has not been any definitive evidence of a Black Hole, though there are some fairly good candidate regions of space that seem to imply a Black Hole might be there (like at the very center of the galaxy).
It wasn't until the 1970's that another famous scientist, Stephen Hawking, developed a theory that showed that a Black Hole (should one exist) should actually evaporate. His theory brings "quantum mechanics" into the Black Hole picture, and involves what are called "virtual particles" being created and instantly annihilated near the "edge" of the Black Hole. Anyway, he shows that this quantum mechanical process can lead to the evaporation of the Black Hole; the larger the Black Hole the longer it would take to evaporate. So, IF little Black Holes "could" be produced in our accelerators, they'd be very very tiny and would last only a very very short time.
I've only given the flavor of the issue; maybe we can talk more details in a future posting. Maybe you'll get to study it in more detail in college(!). It's very fascinating stuff!!
Thanks, and have a great school year,
-Mike Syphers
Monday, December 8, 2008
Saturday, December 6, 2008
Just a question...
Dr. Syphers,
I was just wondering about your take on the entire science vs. religion arguement... Do you face a personal conflict or does it not affect your work at all?
Also, where do you personally see your work in its effects on future technology and generations
Thanks,
Melissa
----
Hi Melissa,
Thanks for your question. I've never personally seen any conflict between science and religion, so it has not affected me in my work or in my daily life.
Science is a "process," through which we try to get closer to the truth of the physical world. That is to say, what we do as scientists is to collect facts through experiments and observations, develop detailed theories that can predict these facts, then test these theories with very well controlled experiments to see if the theories break down. There can be several "theories" that predict the same observed facts. The difference will be if a theory can predict something that has not been observed before. If we do an experiment and we see something that a theory cannot predict, then that theory goes out the window. If a theory predicts something, and we do an experiment and find that prediction to be true, then that gives credence to that particular theory. Note, however, it doesn't prove that the theory is correct either! It just says it's better than the other theories that don't predict this outcome. In this way, we can get closer and closer to the real truth of "how" the physical universe is put together and what the rules are that it appears to follow.
Through this process -- the scientific method -- we try to better understand how the world works. As far as "why" it works that way -- how did it all get started? why are we able to understand it, anyway? "who" made up the rules that we discover? etc. -- these and many others are questions that science cannot even address. So, I really don't think there is any conflict here at all. Science and Religion is not an "either - or" situation. Many, if not most, scientists that I know are very spiritual people. I even know ministers who are scientists and I had a close and well-known colleague (now deceased) who worked with me at Fermilab and was a Jesuit Priest.
-Mike Syphers
----
Hi again, Melissa,
To answer your last question, I'll just say (which I probably said in some earlier posting) that the effects of our research on future generations is very hard to predict. What's not hard to predict is that there will almost certainly be an effect. Every piece of technology we have today -- iPods, computers, flat screen TV's, cars, planes, everything! -- can be directly connected to scientific research that was performed in the past, typically years or decades, sometimes even hundreds of years ago.
-Mike Syphers
I was just wondering about your take on the entire science vs. religion arguement... Do you face a personal conflict or does it not affect your work at all?
Also, where do you personally see your work in its effects on future technology and generations
Thanks,
Melissa
----
Hi Melissa,
Thanks for your question. I've never personally seen any conflict between science and religion, so it has not affected me in my work or in my daily life.
Science is a "process," through which we try to get closer to the truth of the physical world. That is to say, what we do as scientists is to collect facts through experiments and observations, develop detailed theories that can predict these facts, then test these theories with very well controlled experiments to see if the theories break down. There can be several "theories" that predict the same observed facts. The difference will be if a theory can predict something that has not been observed before. If we do an experiment and we see something that a theory cannot predict, then that theory goes out the window. If a theory predicts something, and we do an experiment and find that prediction to be true, then that gives credence to that particular theory. Note, however, it doesn't prove that the theory is correct either! It just says it's better than the other theories that don't predict this outcome. In this way, we can get closer and closer to the real truth of "how" the physical universe is put together and what the rules are that it appears to follow.
Through this process -- the scientific method -- we try to better understand how the world works. As far as "why" it works that way -- how did it all get started? why are we able to understand it, anyway? "who" made up the rules that we discover? etc. -- these and many others are questions that science cannot even address. So, I really don't think there is any conflict here at all. Science and Religion is not an "either - or" situation. Many, if not most, scientists that I know are very spiritual people. I even know ministers who are scientists and I had a close and well-known colleague (now deceased) who worked with me at Fermilab and was a Jesuit Priest.
-Mike Syphers
----
Hi again, Melissa,
To answer your last question, I'll just say (which I probably said in some earlier posting) that the effects of our research on future generations is very hard to predict. What's not hard to predict is that there will almost certainly be an effect. Every piece of technology we have today -- iPods, computers, flat screen TV's, cars, planes, everything! -- can be directly connected to scientific research that was performed in the past, typically years or decades, sometimes even hundreds of years ago.
-Mike Syphers
Friday, December 5, 2008
Atom Smasher LHC
Do you have any advice for the skeptics out there that think the LHC collider may create a black hole?
-AG
----
There are equations and theories that can be written down, which show that any black hole formed in our accelerators would be VERY VERY small, and live for only VERY VERY short lengths of time. So short and so small, that they probably cannot be detected, certainly not very easily. They evaporate very quickly. But, to fear that they can be formed and destroy the earth (or even destroy the accelerator!) are totally unfounded.
One simple argument people point out is that we here on earth are constantly bombarded by particles from outer space. The sun and stars and distant galaxies spew out particles all the time (we call them Cosmic Rays) and pass through the earth. (They're passing through you right now!) We constantly detect these particles with our detectors here at Fermilab all the time. In fact, if you're interested, your teacher can see about getting a Cosmic Ray Detector through the QuarkNet program -- visit the web site:
http://quarknet.fnal.gov/
The point is, the particles from space often have MUCH more energy than we can produce with our accelerators. And these particles have been reaching the earth for billions of years -- and the earth is STILL HERE! So, if black holes can be formed this way, they've already been formed (and evaporated) and haven't harmed the earth. So, there should be no worry about the energies that we reach with our accelerators.
-Mike Syphers
-AG
----
There are equations and theories that can be written down, which show that any black hole formed in our accelerators would be VERY VERY small, and live for only VERY VERY short lengths of time. So short and so small, that they probably cannot be detected, certainly not very easily. They evaporate very quickly. But, to fear that they can be formed and destroy the earth (or even destroy the accelerator!) are totally unfounded.
One simple argument people point out is that we here on earth are constantly bombarded by particles from outer space. The sun and stars and distant galaxies spew out particles all the time (we call them Cosmic Rays) and pass through the earth. (They're passing through you right now!) We constantly detect these particles with our detectors here at Fermilab all the time. In fact, if you're interested, your teacher can see about getting a Cosmic Ray Detector through the QuarkNet program -- visit the web site:
http://quarknet.fnal.gov/
The point is, the particles from space often have MUCH more energy than we can produce with our accelerators. And these particles have been reaching the earth for billions of years -- and the earth is STILL HERE! So, if black holes can be formed this way, they've already been formed (and evaporated) and haven't harmed the earth. So, there should be no worry about the energies that we reach with our accelerators.
-Mike Syphers
Thursday, December 4, 2008
The speed of light...
I read in one of your posts that the accelerators are getting closer to the speed of light. How are you able to calculate their speed?
Carrie
----
Hi Carrie,
We both calculate and measure the speed. First of all, we keep track of how much energy we have given the particles. Then, using a relationship derived by Einstein, you can calculate their speed:
Here, c = speed of light, E = total energy a particle has, and mc^2 = the rest energy
of the particle = its mass times the speed of light squared. You can see that as E gets larger and larger, v gets closer and closer to c (but never quite reaches it).
[p.s. -- let me know if my notation isn't understandable. It's hard to embed equations in the written text, at least for me...]
As for actually measuring the speed, we can time the particle beam as it goes around our accelerators. For instance, the time it takes -- at the speed of light -- to go around the Tevatron is 0.000021 seconds (21 microseconds). That seems pretty small, but we have oscilloscopes and other equipment that can measure this time extremely accurately (like to +/- picoseconds or better). Of course, to get a good measurement of the speed this way, we need to know the distance traveled. The circumference of the Tevatron is actually 6283.19 meters (two pi kilometers!), accurate to a fraction of a centimeter. As the particle beam wanders around, we can steer it with small electromagnets to make sure it is centered within the pipe that it travels in. We can move it around by small fractions of a millimeter to make sure it is on the right orbit everywhere.
-Mike Syphers
----
It sounds like you really enjoy to travel and see the United States. That is something that I would really like to get the chance to do one day. Have you ever traveled out of the country for your job?
I do understand how you calculate and measure the speed of the accelerators. I do have another question though. How often does the speed increase getting closer to the speed of light?
-Carrie
----
Hi Carrie,
"Have you ever traveled out of the country for your job?"
Yes, I have. Over the past 20 years, I've traveled on business several times each to France, Switzerland, Italy, and Germany, and once each to Austria, The Netherlands, and Russia. I've had a couple of opportunities to go to Asia (India, China, and Japan) during that time, too, but I couldn't make those trips for various reasons; maybe some day...
"How often does the speed increase getting closer to the speed of light?"
We have a series of accelerators that give the particles energy. It's like the gears in a bicycle, say, where each stage or accelerator is better suited for its particular energy range. So, at Fermilab for example, the accelerators go something like this:
Proton at rest: energy = 938 MeV (= mc^2 of the proton)
Then, Kinetic Energy is provided by...
Straight accelerators:
Preacc: provides 0.75 MeV; total energy = 938.75 MeV
speed goes from 0 --> 4% the speed of light, c
Linac: provides 399.25 MeV; total energy = 1338 MeV
speed goes from 4 --> 71% c (takes a few microseconds)
Circular accelerators:
Booster: provides 7600 MeV; total energy = 8938 MeV = 8.938 GeV
speed goes from 71 --> 99.45% c (this takes 0.33 sec)
Main Injector: provides 142,000 MeV; total energy = 150.938 GeV = 0.151 TeV
speed goes from 99.45 --> 99.998% c (this takes about 1 sec)
Tevatron: provides 830,000 MeV; total energy = 981 GeV = 0.981 TeV
speed goes from 99.998 --> 99.99995% c (this takes about 20 sec)
Once particles in the Tevatron are at that final energy, we keep them at this energy/speed while they collide head-on with particles moving in the other direction around the circle.
Below is a plot of the speed (fraction of the speed of light) versus the kinetic energy we've given each of the protons. You can see how quickly the speed starts to approach the speed of light. By the time a proton goes through a billion volts (1 GeV), it's almost at 90% c. We can keep giving it energy (and that energy is real, and can do real work), but its speed doesn't change much after a few billion electron volts.
-Mike Syphers
----
Hi Dr. Syphers,
The places you have visited sound very interesting, and a lot of the same ones that I would enjoy seeing. Since you have been so many places, are you able to speak any other languages? If so, how many and what ones.
Finding the speed of an accelerator seems very long and complicated. How long has it taken you to fully understand everything that goes into them?
Thanks
Carrie
----
Hi Carrie,
a) I studied French in school, and one semester of Russian, for good measure. But, I only speak a little (tiny bit) of French these days. Most of the large physics labs that I visit and the conferences I go to tend to speak English, so that's been nice (for me). I always feel a bit odd, though, when the people from these other countries know English, but I don't know their native language. It's too bad for Americans that we don't have as many opportunities to need to learn other languages; it's not enough to just study them in High School.
b) To really understand the speed of the particles in these accelerators, one needs to have a good grasp of Einstein's special theory of relativity. While I learned a little about it in my senior year in high school (2nd year physics class), I studied it in much more detail in a course my sophomore year in college. To be very comfortable with it, however, probably took a few more years and more experience using it in problem solving.
Cheers,
-Mike Syphers
----
Hi Dr. Syphers,
a) That is really cool. Is is hard to learn Russian? I do agree that it is a bit odd that we do not get the chance to learn other languages unlike other countries that learn English at a young age.
b) This sounds very interesting. I have enjoyed my physics class so far and I cannot wait to learn so much more in the rest of the year!
Thank you,
Carrie
----
Hi Carrie,
a) Yes. It was hard for me, at least. It was learning a whole different alphabet, and we had to learn how to write all over again. (We actually started out with the large, lined paper that you use in 1st grade to learn how to print and write in Russian!) But, it was cool to learn about the language, even if I didn't go very far with it.
b) Thanks for your insightful questions and participation. I hope you enjoy the rest of your experience studying and thinking about physics!
-Mike Syphers
----
Hi!
Thank you very much for taking time out of your day for the past three weeks to talk to me. I enjoyed learning about your job, and your travels.
I wish you the best!
Carrie
Carrie
----
Hi Carrie,
We both calculate and measure the speed. First of all, we keep track of how much energy we have given the particles. Then, using a relationship derived by Einstein, you can calculate their speed:
Here, c = speed of light, E = total energy a particle has, and mc^2 = the rest energy
of the particle = its mass times the speed of light squared. You can see that as E gets larger and larger, v gets closer and closer to c (but never quite reaches it).
[p.s. -- let me know if my notation isn't understandable. It's hard to embed equations in the written text, at least for me...]
As for actually measuring the speed, we can time the particle beam as it goes around our accelerators. For instance, the time it takes -- at the speed of light -- to go around the Tevatron is 0.000021 seconds (21 microseconds). That seems pretty small, but we have oscilloscopes and other equipment that can measure this time extremely accurately (like to +/- picoseconds or better). Of course, to get a good measurement of the speed this way, we need to know the distance traveled. The circumference of the Tevatron is actually 6283.19 meters (two pi kilometers!), accurate to a fraction of a centimeter. As the particle beam wanders around, we can steer it with small electromagnets to make sure it is centered within the pipe that it travels in. We can move it around by small fractions of a millimeter to make sure it is on the right orbit everywhere.
-Mike Syphers
----
It sounds like you really enjoy to travel and see the United States. That is something that I would really like to get the chance to do one day. Have you ever traveled out of the country for your job?
I do understand how you calculate and measure the speed of the accelerators. I do have another question though. How often does the speed increase getting closer to the speed of light?
-Carrie
----
Hi Carrie,
"Have you ever traveled out of the country for your job?"
Yes, I have. Over the past 20 years, I've traveled on business several times each to France, Switzerland, Italy, and Germany, and once each to Austria, The Netherlands, and Russia. I've had a couple of opportunities to go to Asia (India, China, and Japan) during that time, too, but I couldn't make those trips for various reasons; maybe some day...
"How often does the speed increase getting closer to the speed of light?"
We have a series of accelerators that give the particles energy. It's like the gears in a bicycle, say, where each stage or accelerator is better suited for its particular energy range. So, at Fermilab for example, the accelerators go something like this:
Proton at rest: energy = 938 MeV (= mc^2 of the proton)
Then, Kinetic Energy is provided by...
Straight accelerators:
Preacc: provides 0.75 MeV; total energy = 938.75 MeV
speed goes from 0 --> 4% the speed of light, c
Linac: provides 399.25 MeV; total energy = 1338 MeV
speed goes from 4 --> 71% c (takes a few microseconds)
Circular accelerators:
Booster: provides 7600 MeV; total energy = 8938 MeV = 8.938 GeV
speed goes from 71 --> 99.45% c (this takes 0.33 sec)
Main Injector: provides 142,000 MeV; total energy = 150.938 GeV = 0.151 TeV
speed goes from 99.45 --> 99.998% c (this takes about 1 sec)
Tevatron: provides 830,000 MeV; total energy = 981 GeV = 0.981 TeV
speed goes from 99.998 --> 99.99995% c (this takes about 20 sec)
Once particles in the Tevatron are at that final energy, we keep them at this energy/speed while they collide head-on with particles moving in the other direction around the circle.
Below is a plot of the speed (fraction of the speed of light) versus the kinetic energy we've given each of the protons. You can see how quickly the speed starts to approach the speed of light. By the time a proton goes through a billion volts (1 GeV), it's almost at 90% c. We can keep giving it energy (and that energy is real, and can do real work), but its speed doesn't change much after a few billion electron volts.
-Mike Syphers
----
Hi Dr. Syphers,
The places you have visited sound very interesting, and a lot of the same ones that I would enjoy seeing. Since you have been so many places, are you able to speak any other languages? If so, how many and what ones.
Finding the speed of an accelerator seems very long and complicated. How long has it taken you to fully understand everything that goes into them?
Thanks
Carrie
----
Hi Carrie,
a) I studied French in school, and one semester of Russian, for good measure. But, I only speak a little (tiny bit) of French these days. Most of the large physics labs that I visit and the conferences I go to tend to speak English, so that's been nice (for me). I always feel a bit odd, though, when the people from these other countries know English, but I don't know their native language. It's too bad for Americans that we don't have as many opportunities to need to learn other languages; it's not enough to just study them in High School.
b) To really understand the speed of the particles in these accelerators, one needs to have a good grasp of Einstein's special theory of relativity. While I learned a little about it in my senior year in high school (2nd year physics class), I studied it in much more detail in a course my sophomore year in college. To be very comfortable with it, however, probably took a few more years and more experience using it in problem solving.
Cheers,
-Mike Syphers
----
Hi Dr. Syphers,
a) That is really cool. Is is hard to learn Russian? I do agree that it is a bit odd that we do not get the chance to learn other languages unlike other countries that learn English at a young age.
b) This sounds very interesting. I have enjoyed my physics class so far and I cannot wait to learn so much more in the rest of the year!
Thank you,
Carrie
----
Hi Carrie,
a) Yes. It was hard for me, at least. It was learning a whole different alphabet, and we had to learn how to write all over again. (We actually started out with the large, lined paper that you use in 1st grade to learn how to print and write in Russian!) But, it was cool to learn about the language, even if I didn't go very far with it.
b) Thanks for your insightful questions and participation. I hope you enjoy the rest of your experience studying and thinking about physics!
-Mike Syphers
----
Hi!
Thank you very much for taking time out of your day for the past three weeks to talk to me. I enjoyed learning about your job, and your travels.
I wish you the best!
Carrie
Wednesday, December 3, 2008
Accelerators
Q: I get what accelerator physics is, but how can we really use it in real life? And why do you need to switch over from the Tevatron to the LHC? How are they different?
Hello Dr. Syphers,
My name is Shannon...
I was a little confused about the LHC accelerator. I know what it is, but how does it work? Also, how is this different from the Tevatron?
----
Why Accelerators, and how do they work?
Hi all,
This is in response to several questions, like the ones above, which are fairly similar to each other, namely ...
"How can we use accelerator physics in real life? Why do we need to switch over to the LHC from the Tevatron? How does the LHC work? How is it different from the Tevatron??"
The accelerators I work on use electric fields to accelerate charged particles and give them more and more kinetic energy. You may have learned (or will learn) that a particle can gain energy by doing work on it; work is basically "force times distance"; and the force here is the force due to an electric field. So, by subjecting particles like electrons or protons (charged!) to electric fields we can give them kinetic energy and they speed up.
I should point out, however, that eventually they get closer and closer to the speed of light, which is a "limit" that they cannot cross, in accordance with Einstein's theory of special relativity. But, they can (and do) continue to gain energy. We see and use Einstein's theory in our work every day. In fact, these accelerators wouldn't work at all if we didn't know about relativity.
Most particle accelerators were developed to study elementary particles like electrons, protons, ions, etc. The first ones were built in the 1920's and 1930's. But there have been many "spin-offs" of these devices. For instance, the older-style television sets (before "flat screen" TV's) use electron beams in them. They are actually particle accelerators! You might have one in your home today. In this case, the electrons are subjected to electric fields that produce total voltages of 10,000 volts or so. We say, then, that an electron in this scenario would gain a total kinetic energy of 10,000 electron volts (10 keV). This is just shorthand that we use in the accelerator business, because we tend to deal with elementary particles like electrons and protons, etc. In terms of Joules of energy, 1 eV = 1.6 x 10^(-19) Joule.
Other spin-offs of accelerator physics have been in the field of medicine, where x-ray machines (electron accelerators), MRI machines, PET scans, etc. use technologies developed for particle accelerators. There is even proton and neutron cancer therapy treatments that use particles from accelerators. Accelerators are also used in industry for welding, chemical analysis, and many other uses. But what has driven all of this has been the quest to examine nature's smallest particles and most fundamental forces.
The Tevatron is the highest energy accelerator in the world today. It accelerates protons through a total of 1 Trillion volts (10^(12) volts). Thus, the protons each have an energy of 1 TeV (which is how the Tevatron got its name). The LHC will make protons with energies of 7 TeV. Both of these accelerators are used, or will be used, to collide particles going in opposite directions at these high energies. Particles in nature have not had these kinds of energies since just after the Big Bang, so we are reproducing conditions from way back then. The purpose of both of these accelerators is to learn how the universe is put together by creating and studying particles that existed in great numbers long ago.
There isn't a very large fundamental difference between the LHC and the Tevatron. The LHC is larger, has stronger magnets and will give particles 7 times more energy than the Tevatron does. This just allows us to create more particles with more energy and study smaller and smaller things, hopefully gaining further insights into how the universe works. In each case, particles pass through electric fields, giving them energy (and momentum). Then, they are directed around in a circle using electromagnets so that they can pass through the electric fields again and gain MORE energy. The required strength of the electromagnets depends upon the momentum of the particles; as the particles gain momentum the magnets have to be turned on stronger and stronger. So, since we can only build magnets "so strong," then the circles get bigger and bigger for higher particle energies. The Tevatron is 4 miles in circumference. The LHC is 17 miles around!
I've left out a lot of details here, but these blogs can get rather long...
I'm sure you have more questions, so have at it!
Cheers,
-Mike Syphers
----
Hi this is Will
I was just wondering, when you collide the particles do you actually see anything or because its so fast you only see what happens with the ultra high speed cameras? And what do they look like, explosions or like fireworks or what? Thanks again for doing this program.
----
Hi Will,
That's a great question. First of all, what does it mean to "see" something? I mean, really physically. When you "see" something, physically what happens is that photons enter your eye through the iris (the detector's limiting aperture), get focused by the eye's lens, and interact with molecules in your retina that create electrical signals which are transmitted to your brain. Based upon which portions of the retina are activated, and with what "intensity," the brain interprets what it detects to decide what it was you just "saw". Might you agree with all that?
So, the way we "see" things in our experiment is to allow the particles to collide, which creates new particles moving in lots of directions. These new particles interact with different parts of our detectors, which generate electrical signals that are monitored by computers (the "brains" of the experiment). The computer signals are stored and reconstructed later. These detectors have magnetic fields built in so that we can monitor how the charged particles move around -- thus, we can determine their charge (pos or neg) and most of the time their momentum as well. We have blocks of metal that can absorb particles, too. When these blocks heat up, we can determine what energy the particles had. We put all of this type of information from a single collision together, and allow the computer to reconstruct what happened. (Of course, the computer only does what a scientist tells it to do, so it's actually the scientists who program the computers that diagnose what happened.)
At the bottome of this response is an image of what the computer might reconstruct from a collision. The lines and curves emanating from the center are "tracks" reconstructed by the computer program to show where particles went. The colored bars along the circumference of the program indicate the amount of energy that the particles had.
As you can see, they do indeed look a little bit like "fireworks." Cool? or not?
Hello Dr. Syphers,
My name is Shannon...
I was a little confused about the LHC accelerator. I know what it is, but how does it work? Also, how is this different from the Tevatron?
----
Why Accelerators, and how do they work?
Hi all,
This is in response to several questions, like the ones above, which are fairly similar to each other, namely ...
"How can we use accelerator physics in real life? Why do we need to switch over to the LHC from the Tevatron? How does the LHC work? How is it different from the Tevatron??"
The accelerators I work on use electric fields to accelerate charged particles and give them more and more kinetic energy. You may have learned (or will learn) that a particle can gain energy by doing work on it; work is basically "force times distance"; and the force here is the force due to an electric field. So, by subjecting particles like electrons or protons (charged!) to electric fields we can give them kinetic energy and they speed up.
I should point out, however, that eventually they get closer and closer to the speed of light, which is a "limit" that they cannot cross, in accordance with Einstein's theory of special relativity. But, they can (and do) continue to gain energy. We see and use Einstein's theory in our work every day. In fact, these accelerators wouldn't work at all if we didn't know about relativity.
Most particle accelerators were developed to study elementary particles like electrons, protons, ions, etc. The first ones were built in the 1920's and 1930's. But there have been many "spin-offs" of these devices. For instance, the older-style television sets (before "flat screen" TV's) use electron beams in them. They are actually particle accelerators! You might have one in your home today. In this case, the electrons are subjected to electric fields that produce total voltages of 10,000 volts or so. We say, then, that an electron in this scenario would gain a total kinetic energy of 10,000 electron volts (10 keV). This is just shorthand that we use in the accelerator business, because we tend to deal with elementary particles like electrons and protons, etc. In terms of Joules of energy, 1 eV = 1.6 x 10^(-19) Joule.
Other spin-offs of accelerator physics have been in the field of medicine, where x-ray machines (electron accelerators), MRI machines, PET scans, etc. use technologies developed for particle accelerators. There is even proton and neutron cancer therapy treatments that use particles from accelerators. Accelerators are also used in industry for welding, chemical analysis, and many other uses. But what has driven all of this has been the quest to examine nature's smallest particles and most fundamental forces.
The Tevatron is the highest energy accelerator in the world today. It accelerates protons through a total of 1 Trillion volts (10^(12) volts). Thus, the protons each have an energy of 1 TeV (which is how the Tevatron got its name). The LHC will make protons with energies of 7 TeV. Both of these accelerators are used, or will be used, to collide particles going in opposite directions at these high energies. Particles in nature have not had these kinds of energies since just after the Big Bang, so we are reproducing conditions from way back then. The purpose of both of these accelerators is to learn how the universe is put together by creating and studying particles that existed in great numbers long ago.
There isn't a very large fundamental difference between the LHC and the Tevatron. The LHC is larger, has stronger magnets and will give particles 7 times more energy than the Tevatron does. This just allows us to create more particles with more energy and study smaller and smaller things, hopefully gaining further insights into how the universe works. In each case, particles pass through electric fields, giving them energy (and momentum). Then, they are directed around in a circle using electromagnets so that they can pass through the electric fields again and gain MORE energy. The required strength of the electromagnets depends upon the momentum of the particles; as the particles gain momentum the magnets have to be turned on stronger and stronger. So, since we can only build magnets "so strong," then the circles get bigger and bigger for higher particle energies. The Tevatron is 4 miles in circumference. The LHC is 17 miles around!
I've left out a lot of details here, but these blogs can get rather long...
I'm sure you have more questions, so have at it!
Cheers,
-Mike Syphers
----
Hi this is Will
I was just wondering, when you collide the particles do you actually see anything or because its so fast you only see what happens with the ultra high speed cameras? And what do they look like, explosions or like fireworks or what? Thanks again for doing this program.
----
Hi Will,
That's a great question. First of all, what does it mean to "see" something? I mean, really physically. When you "see" something, physically what happens is that photons enter your eye through the iris (the detector's limiting aperture), get focused by the eye's lens, and interact with molecules in your retina that create electrical signals which are transmitted to your brain. Based upon which portions of the retina are activated, and with what "intensity," the brain interprets what it detects to decide what it was you just "saw". Might you agree with all that?
So, the way we "see" things in our experiment is to allow the particles to collide, which creates new particles moving in lots of directions. These new particles interact with different parts of our detectors, which generate electrical signals that are monitored by computers (the "brains" of the experiment). The computer signals are stored and reconstructed later. These detectors have magnetic fields built in so that we can monitor how the charged particles move around -- thus, we can determine their charge (pos or neg) and most of the time their momentum as well. We have blocks of metal that can absorb particles, too. When these blocks heat up, we can determine what energy the particles had. We put all of this type of information from a single collision together, and allow the computer to reconstruct what happened. (Of course, the computer only does what a scientist tells it to do, so it's actually the scientists who program the computers that diagnose what happened.)
At the bottome of this response is an image of what the computer might reconstruct from a collision. The lines and curves emanating from the center are "tracks" reconstructed by the computer program to show where particles went. The colored bars along the circumference of the program indicate the amount of energy that the particles had.
As you can see, they do indeed look a little bit like "fireworks." Cool? or not?
Tuesday, December 2, 2008
Doomsday??
Hey, I'm Will. Thank you for participating in this program, it is very kind of you. I'm interested in doing some type of engineering and I'm interested in physics because of that. Do you think the machine your making could produce black holes and potentially destroy the world...a doomsday machine?
----
Hi Will,
No, I do not believe we have anything to worry about. This is an interesting question that has come up in the (sensationalized?) news media lately regarding the LHC accelerator coming on line in Europe. The earth is bombarded every second by particles that are emitted from the sun and other sources, particles with much higher energies than what we can make in our accelerators. These particles have been bombarding the earth for billions of years -- and the earth is still here.
But, perhaps in a later post, I can go into more detail about the black hole question. It is interesting to think about and discuss...
Cheers,
-Mike
----
Thanks for clearing that up. I did not know about all those other particles hitting the earth. It was just something I had seen on the news and thought you would be the perfect person to ask. If it ever did produce black holes, what would they do and how big would they be?
Thanks again, Will
----
Hi Will,
First of all, let me point out that while Einstein's theory of General Relativity predicts that Black Holes can exist, and while there are several very good pieces of evidence that specific Black Holes do exist (like at the center of our galaxy), there has never been an absolute observation that says "this IS a Black Hole." (However, I personally think that the evidence for a Black Hole at the center of our galaxy is very convincing!)
Having said that, let me point out also that the way space and time behave in the vicinity of extremely massive objects, like stars and galaxies, does not necessarily mean that space and time behave exactly that way at very very small scales (like near "point particles" such as electrons and quarks). We call electrons "point particles" because, to our knowledge, they don't appear to have any real size. But to be honest, maybe we just haven't learned how to look at that small a scale yet.
The reason I bring this up is because the Black Holes that would be predicted to be created at, say, the LHC would be extremely small. Extremely small. There is a formula (which, again, we don't know if it is truly applicable at very small scales) for the size of a Black Hole. The formula is
where in the formula, R is the radius of the Black Hole, M is the mass inside, G is Newton's gravitational constant, and c is the speed of light.
So, I'll ask you to do the calculation -- if the LHC collides two protons, each with 7 TeV of energy, and all of that energy is turned into mass, and that mass just sits there as a Black Hole, what would its radius be?
Here's a hint: Mc^2 for our particle will have a value of 14 TeV; 1 TeV of energy = 1 x 10^12 eV; and, 1 eV = 1.6 x 10^-19 Joules.
Note that the "radius" of a proton is about 10^-15 m, and the mass of this particle that would be created in the LHC is about 14,000 times heavier than a single proton.
Let me know what answer you get!
-Mike Syphers
----
R= 3.69 x 10^-48
WOW, that is small, since 10^50 is statistically impossible.....yeah there is nothing to worry about. Thanks for showing me that, i love numbers they really help show the magnitude, or lack there of, of the "black holes". Thanks again, Will.
----
Hi Will,
No, I do not believe we have anything to worry about. This is an interesting question that has come up in the (sensationalized?) news media lately regarding the LHC accelerator coming on line in Europe. The earth is bombarded every second by particles that are emitted from the sun and other sources, particles with much higher energies than what we can make in our accelerators. These particles have been bombarding the earth for billions of years -- and the earth is still here.
But, perhaps in a later post, I can go into more detail about the black hole question. It is interesting to think about and discuss...
Cheers,
-Mike
----
Thanks for clearing that up. I did not know about all those other particles hitting the earth. It was just something I had seen on the news and thought you would be the perfect person to ask. If it ever did produce black holes, what would they do and how big would they be?
Thanks again, Will
----
Hi Will,
First of all, let me point out that while Einstein's theory of General Relativity predicts that Black Holes can exist, and while there are several very good pieces of evidence that specific Black Holes do exist (like at the center of our galaxy), there has never been an absolute observation that says "this IS a Black Hole." (However, I personally think that the evidence for a Black Hole at the center of our galaxy is very convincing!)
Having said that, let me point out also that the way space and time behave in the vicinity of extremely massive objects, like stars and galaxies, does not necessarily mean that space and time behave exactly that way at very very small scales (like near "point particles" such as electrons and quarks). We call electrons "point particles" because, to our knowledge, they don't appear to have any real size. But to be honest, maybe we just haven't learned how to look at that small a scale yet.
The reason I bring this up is because the Black Holes that would be predicted to be created at, say, the LHC would be extremely small. Extremely small. There is a formula (which, again, we don't know if it is truly applicable at very small scales) for the size of a Black Hole. The formula is
where in the formula, R is the radius of the Black Hole, M is the mass inside, G is Newton's gravitational constant, and c is the speed of light.
So, I'll ask you to do the calculation -- if the LHC collides two protons, each with 7 TeV of energy, and all of that energy is turned into mass, and that mass just sits there as a Black Hole, what would its radius be?
Here's a hint: Mc^2 for our particle will have a value of 14 TeV; 1 TeV of energy = 1 x 10^12 eV; and, 1 eV = 1.6 x 10^-19 Joules.
Note that the "radius" of a proton is about 10^-15 m, and the mass of this particle that would be created in the LHC is about 14,000 times heavier than a single proton.
Let me know what answer you get!
-Mike Syphers
----
R= 3.69 x 10^-48
WOW, that is small, since 10^50 is statistically impossible.....yeah there is nothing to worry about. Thanks for showing me that, i love numbers they really help show the magnitude, or lack there of, of the "black holes". Thanks again, Will.
Monday, December 1, 2008
Super Job
Dr. Syphers,
In your job what is the most interesting or unusual project that you have had a chance to work on?
Johnathon
----
Hi Johnathon,
I'd have to say that the most interesting project I ever worked on was the Superconducting Super Collider project. I worked on it a little bit, off and on, for a few years, and then full-time for about 5 years. It was a brand new accelerator laboratory that was being built just south of Dallas, Texas. Construction started in 1989, but was stopped in 1993. I was the 67th employee to be hired to work on it; when the project was canceled in 1993, there were over 2000 people at the laboratory. So, I was there at the very beginning and got to participate in a lot of very important design decisions for the project. Congress decided in October of 1993, however, that the national budget needed to be balanced, and that we couldn't afford to continue building it. (The total cost was going to be about $8 -- $10 Billion.) The main accelerator was to be 53 miles in circumference (we had already built 17 miles of tunnel for it -- about the size of the LHC in Europe!) and the energy of the protons would have been 20 times the energy of the Tevatron that I work on today at Fermilab. It would have been the largest scientific instrument ever built. Even though it was halted, it was certainly the most interesting and exciting project I have ever gotten to work on, and it was perhaps the most valuable experience of my career.
-Mike Syphers
----
Dr. Syphers,
Thank you for the reply, and in your opinion do you think that it would have been more beneficial to us to complete that project or was it a good decision by the government to stop the project?
I think it was an unfortunate decision to stop the project. It was good to balance the budget, which the government should always try to do; but, I think it was a huge sacrifice to pull the plug on that project. Today, people look at the huge accelerator being built in Europe, and ask me, "Why aren't we building one that big?" And I have to tell them about the SSC project and its failure. So, I just hope people learn that it's important to do basic research -- for knowledge's sake and for the economy -- and that projects like this take a long time to build, that the pay-off can be huge, and that our representatives in Congress need to be told by the citizens that they (the citizens) think this is important.
-Mike Syphers
----
Thank you so much for your reply!
i find it amazing that one can actually love what they do all of their life.
is there anything you've done in phisics that has been noted on a larger scale??
have you made any important breakthroughs or discoveries?
-henry
----
Hi Henry,
I am sorry to report that I haven't made any scientific "breakthroughs" or "discoveries" on a very large scale. That doesn't really happen too often in life, or to too many people. But, like most scientists, I've done my share of small increments in knowledge that have helped things along. For instance, the Top Quark is an important particle of nature that was discovered at Fermilab in 1995. To discover it, we had to collide protons and antiprotons together and this required very tiny beams of particles moving head-on toward each other. As we accelerate these particles, there are many things along their journey which try to make the beams larger, so we have to work very hard to keep them small. In the late 1980's I figured out one of the mechanisms that was making the beam too large, and re-designed a beam transport system to keep the beam smaller. This helped reduce the beam size by about a factor of two, and thus helped generate more collisions for the Tevatron. Did I discover the top quark? No, but I certainly helped make the discovery possible. We all do our part, and it's all important. In more recent years, I've worked further on these types of problems, and the rate at which the Tevatron collides particles is about 300 times what it was in 1990! Will we discover the Higgs particle before the LHC does? We'll see...
-Mike Syphers
In your job what is the most interesting or unusual project that you have had a chance to work on?
Johnathon
----
Hi Johnathon,
I'd have to say that the most interesting project I ever worked on was the Superconducting Super Collider project. I worked on it a little bit, off and on, for a few years, and then full-time for about 5 years. It was a brand new accelerator laboratory that was being built just south of Dallas, Texas. Construction started in 1989, but was stopped in 1993. I was the 67th employee to be hired to work on it; when the project was canceled in 1993, there were over 2000 people at the laboratory. So, I was there at the very beginning and got to participate in a lot of very important design decisions for the project. Congress decided in October of 1993, however, that the national budget needed to be balanced, and that we couldn't afford to continue building it. (The total cost was going to be about $8 -- $10 Billion.) The main accelerator was to be 53 miles in circumference (we had already built 17 miles of tunnel for it -- about the size of the LHC in Europe!) and the energy of the protons would have been 20 times the energy of the Tevatron that I work on today at Fermilab. It would have been the largest scientific instrument ever built. Even though it was halted, it was certainly the most interesting and exciting project I have ever gotten to work on, and it was perhaps the most valuable experience of my career.
-Mike Syphers
----
Dr. Syphers,
Thank you for the reply, and in your opinion do you think that it would have been more beneficial to us to complete that project or was it a good decision by the government to stop the project?
I think it was an unfortunate decision to stop the project. It was good to balance the budget, which the government should always try to do; but, I think it was a huge sacrifice to pull the plug on that project. Today, people look at the huge accelerator being built in Europe, and ask me, "Why aren't we building one that big?" And I have to tell them about the SSC project and its failure. So, I just hope people learn that it's important to do basic research -- for knowledge's sake and for the economy -- and that projects like this take a long time to build, that the pay-off can be huge, and that our representatives in Congress need to be told by the citizens that they (the citizens) think this is important.
-Mike Syphers
----
Thank you so much for your reply!
i find it amazing that one can actually love what they do all of their life.
is there anything you've done in phisics that has been noted on a larger scale??
have you made any important breakthroughs or discoveries?
-henry
----
Hi Henry,
I am sorry to report that I haven't made any scientific "breakthroughs" or "discoveries" on a very large scale. That doesn't really happen too often in life, or to too many people. But, like most scientists, I've done my share of small increments in knowledge that have helped things along. For instance, the Top Quark is an important particle of nature that was discovered at Fermilab in 1995. To discover it, we had to collide protons and antiprotons together and this required very tiny beams of particles moving head-on toward each other. As we accelerate these particles, there are many things along their journey which try to make the beams larger, so we have to work very hard to keep them small. In the late 1980's I figured out one of the mechanisms that was making the beam too large, and re-designed a beam transport system to keep the beam smaller. This helped reduce the beam size by about a factor of two, and thus helped generate more collisions for the Tevatron. Did I discover the top quark? No, but I certainly helped make the discovery possible. We all do our part, and it's all important. In more recent years, I've worked further on these types of problems, and the rate at which the Tevatron collides particles is about 300 times what it was in 1990! Will we discover the Higgs particle before the LHC does? We'll see...
-Mike Syphers
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