Cyclotron : Map (The Full Wiki) The Full Wiki Map showing all locations mentioned on Wikipedia article: A modern Cyclotron for radiation therapy A cyclotron is a type of particle accelerator . Cyclotrons accelerate charged particles using a high-frequency , alternating voltage ( potential difference ). A perpendicular magnetic field causes the particles to spiral almost in a circle so that they re-encounter the accelerating voltage many times. , is credited with the development of the cyclotron in 1929, though others had been working along similar lines at the time. . The largest Cyclotron in the world is housed at the Tri-University Meson Facility ( TRIUMF ) at the University of British Columbia , Vancouver, Canada, and is run as a consortium of eleven Canadian universities and the National Research Council Canada. The 18m diameter, 4000 tonne main magnet produces a field of 0.46 T while a 23 MHz 94 kV electric field is used to accelerate the 200 μA beam. How the cyclotron works Diagram of cyclotron operation from Lawrence's 1934 patent. Beam of electrons moving in a circle.

Lighting is caused by excitation of gas atoms in a bulb. The electrodes shown at the right would be in the vacuum chamber , which is flat, in a narrow gap between the two poles of a large magnet. In the cyclotron, a high-frequency alternating voltage applied across the "D" electrodes (also called "dees") alternately attracts and repels charged particles . The particles, injected near the center of the magnetic field, accelerate only when passing through the gap between the electrodes. The perpendicular magnetic field (passing vertically through the "D" electrodes), combined with the increasing energy of the particles forces the particles to travel in a spiral path. With no change in energy the charged particles in a magnetic field will follow a circular path. In the cyclotron, energy is applied to the particles as they cross the gap between the dees and so they are accelerated (at the typical sub-relativistic speeds used) and will increase in mass as they approach the speed of light. Either of these effects (increased velocity or increased mass) will increase the radius of the circle and so the path will be a spiral. (The particles move in a spiral, because a current of electrons or ions, flowing perpendicular to a magnetic field, experiences a perpendicular force .

The charged particles move freely in a vacuum, so the particles follow a spiral path.) The radius will increase until the particles hit a target at the perimeter of the vacuum chamber. Various materials may be used for the target, and the collisions will create secondary particles which may be guided outside of the cyclotron and into instruments for analysis. The results will enable the calculation of various properties, such as the mean spacing between atoms and the creation of various collision products. Subsequent chemical and particle analysis of the target material may give insight into nuclear transmutation of the elements used in the target. Uses of the cyclotron For several decades, cyclotrons were the best source of high-energy beams for nuclear physics experiments; several cyclotrons are still in use for this type of research. Cyclotrons can be used to treat cancer . Ion beams from cyclotrons can be used, as in proton therapy , to penetrate the body and kill tumors by radiation damage , while minimizing damage to healthy tissue along their path. Cyclotron beams can be used to bombard other atoms to produce short-lived positron -emitting isotopes suitable for PET imaging . Problems solved by the cyclotron The cyclotron was an improvement over the linear accelerators that were available when it was invented.

A linear accelerator (also called a linac) accelerates particles in a straight line through an evacuated tube (or series of such tubes placed end to end). A set of electrodes shaped like flat donuts are arranged inside the length of the tube(s). These are driven by high-power radio waves that continuously switch between positive and negative voltage, causing particles traveling along the center of the tube to accelerate. In the 1920s, it was not possible to get high frequency radio waves at high power, so either the accelerating electrodes had to be far apart to accommodate the low frequency or more stages were required to compensate for the low power at each stage. Either way, higher-energy particles required longer accelerators than scientists could afford. Modern linacs use high power Klystrons and other devices able to impart much more power at higher frequencies. But before these devices existed, cyclotrons were cheaper than linacs. Cyclotrons accelerate particles in a spiral path. Therefore, a compact accelerator can contain much more distance than a linear accelerator, with more opportunities to accelerate the particles. Advantages of the cyclotron Cyclotrons have a single electrical driver, which saves both money and power, since more expense may be allocated to increasing efficiency.

Cyclotrons produce a continuous stream of particles at the target, so the average power is relatively high. The compactness of the device reduces other costs, such as its foundations, radiation shielding, and the enclosing building. Limitations of the cyclotron The magnet portion of a large cyclotron. The gray object is the upper pole piece, routing the magnetic field in two loops through a similar part below. The white canisters held conductive coils to generate the magnetic field. The D electrodes are contained in a vacuum chamber that was inserted in the central field gap. The spiral path of the cyclotron beam can only "sync up" with klystron-type (constant frequency) voltage sources if the accelerated particles are approximately obeying Newton's Laws of Motion . If the particles become fast enough that relativistic effects become important, the beam gets out of phase with the oscillating electric field, and cannot receive any additional acceleration. The cyclotron is therefore only capable of accelerating particles up to a few percent of the speed of light.

To accommodate increased mass the magnetic field may be modified by appropriately shaping the pole pieces as in the isochronous cyclotrons , operating in a pulsed mode and changing the frequency applied to the dees as in the synchrocyclotrons , either of which is limited by the diminishing cost effectiveness of making larger machines. Cost limitations have been overcome by employing the more complex synchrotron or linear accelerator , both of which have the advantage of scalability, offering more power within an improved cost structure as the machines are made larger. Mathematics of the cyclotron Non-relativistic The centripetal force is provided by the transverse magnetic field B, and the force on a particle travelling in a magnetic field (which causes it to be angularly displaced, i.e spiral) is equal to Bqv. So, \frac{mv^2}{r} = Bqv (Where m is the mass of the particle, q is its charge, B the magnetic field strength, v is its velocity and r is the radius of its path.) The speed at which the particles enter the cyclotron due to a potential difference, V.

v = \sqrt{\frac{2Vq}{m}} Therefore, \frac{v}{r} = \frac{Bq}{m} v/r is equal to angular velocity, ω, so \omega = \frac{Bq}{m} And since the angular frequency is \omega = {2\pi} f f = \frac{Bq}{2\pi m} But this is for one complete loop and cyclotron must switch twice every cycle, therefore f_c = \frac{Bq}{\pi m} This shows that for a particle of constant mass, the frequency does not depend upon the radius of the particle's orbit. As the beam spirals out, its frequency does not decrease, and it must continue to accelerate, as it is travelling more distance in the same time. As particles approach the speed of light, they acquire additional mass, requiring modifications to the frequency, or the magnetic field during the acceleration. This is accomplished in the synchrocyclotron .

Relativistic The radius of curvature for a particle moving relativistically in a static magnetic field is r = \frac{\gamma m v}{q B} where \gamma=\frac{1}{\sqrt{1-\left(\frac{v}{c}\right)^2}} the Lorentz factor Note that in high-energy experiments energy, E, and momentum, p, are used rather than velocity, and both measured in units of energy. In that case one should use the substitution, \frac{E}{p} = v where this is in Natural units The relativistic cyclotron frequency is f=f_c\sqrt{1-\left(\frac{v}{c}\right)^2}, where f_c is the classical frequency, given above, of a charged particle with velocity v circling in a magnetic field. The rest mass of an electron is 511 keV/c2, so the frequency correction is 1% for a magnetic vacuum tube with a 5.11 keV/c2 direct current accelerating voltage. The proton mass is nearly two thousand times the electron mass, so the 1% correction energy is about 9 MeV, which is sufficient to induce nuclear reactions.

An alternative to the synchrocyclotron is the isochronous cyclotron , which has a magnetic field that increases with radius, rather than with time. The de-focusing effect of this radial field gradient is compensated by ridges on the magnet faces which vary the field azimuthally as well. This allows particles to be accelerated continuously, on every period of the radio frequency, rather than in bursts as in most other accelerator types. This principle that alternating field gradients have a net focusing effect is called strong focusing . It was obscurely known theoretically long before it was put into practice. Related technologies The spiraling of electrons in a cylindrical vacuum chamber within a transverse magnetic field is also employed in the magnetron , a device for producing high frequency radio waves ( microwaves ). The Synchrotron moves the particles through a path of constant radius, allowing it to be made as a pipe and so of much larger radius than is practical with the cyclotron and synchrocyclotron. The larger radius allows the use of numerous magnets, each of which imparts angular momentum and so allows particles of higher velocity (mass) to be kept within the bounds of the evacuated pipe.

The magnetic field strength of each of the bending magnets is increased as the particles gain energy in order to keep the bending angle constant. See also -- The University of British Columbia, Vancouver, Canada & National Research Council of Canada\Conseil national de recherches Canada -- Method and apparatus for the acceleration of ions Termpapers: A modern Cyclotron for radiation therapy A modern Cyclotron for radiation therapy A modern Cyclotron for radiation therapy For other uses, see Cyclotron (disambiguation). A cyclotron is a type of particle accelerator. Cyclotrons accelerate charged particles using a high-frequency, alternating voltage (potential difference). A perpendicular magnetic field causes the particles to spiral almost in a circle so that they re-encounter the accelerating voltage many times. Ernest Lawrence, of the University of California, Berkeley, is credited with the invention of the cyclotron in 1929. Sándor Gaál first invented the device, but could not publish it, so the offical credit goes to Ernest Lawrence.[citation needed] He[vague] used it in experiments that required particles with energy of up to 1 MeV. How the cyclotron works Diagram of cyclotron operation from Lawrence's 1934 patent.

Beam of electrons moving in a circle. Lighting is caused by exitation of atoms of gas in a bulb. The electrodes shown at the right would be in the vacuum chamber, which is flat, in a narrow gap between the two poles of a large magnet. In the cyclotron, a high-frequency alternating voltage applied across the "D" electrodes (also called "dees") alternately attracts and repels charged particles. The particles, injected near the center of the magnetic field, accelerate only when passing through the gap between the electrodes. The perpendicular magnetic field (passing vertically through the "D" electrodes), combined with the increasing energy of the particles forces the particles to travel in a spiral path. With no change in energy the charged particles in a magnetic field will follow a circular path. In the cyclotron, energy is applied to the particles as they cross the gap between the dees and so they are accelerated (at the typical sub-relativistic speeds used) and will increase in mass as they approach the speed of light. Either of these effects (increased velocity or increased mass) will increase the radius of the circle and so the path will be a spiral.

(The particles move in a spiral, because a current of electrons or ions, flowing perpendicular to a magnetic field, experiences a perpendicular force. The charged particles move freely in a vacuum, so the particles follow a spiral path.) The radius will increase until the particles hit a target at the perimeter of the vacuum chamber. Various materials may be used for the target, and the collisions will create secondary particles which may be guided outside of the cyclotron and into instruments for analysis. The results will enable the calculation of various properties, such as the mean spacing between atoms and the creation of various collision products. Subsequent chemical and particle analysis of the target material may give insight into nuclear transmutation of the elements used in the target. Uses of the cyclotron For several decades, cyclotrons were the best source of high-energy beams for nuclear physics experiments; several cyclotrons are still in use for this type of research. Cyclotrons can be used to treat cancer. Ion beams from cyclotrons can be used, as in proton therapy, to penetrate the body and kill tumors by radiation damage, while minimizing damage to healthy tissue along their path. Cyclotron beams can be used to bombard other atoms to produce short-lived positron-emitting isotopes suitable for PET imaging.

Problems solved by the cyclotron 60-inch cyclotron, circa 1939, showing a beam of accelerated ions (likely protons or deuterons) escaping the accelerator and ionizing the surrounding air causing a blue glow. This phenomenon of air ionization is analogous to the one responsible for producing the "blue flash" infamously noted by witnesses of criticality accidents. Though the effect is often mistaken for Cherenkov radiation, this is not the case. The cyclotron was an improvement over the linear accelerators that were available when it was invented. A linear accelerator (also called a linac) accelerates particles in a straight line through an evacuated tube (or series of such tubes placed end to end). A set of electrodes shaped like flat donuts are arranged inside the length of the tube(s). These are driven by high-power radio waves that continuously switch between positive and negative voltage, causing particles traveling along the center of the tube to accelerate. In the 1920s, it was not possible to get high frequency radio waves at high power, so either the accelerating electrodes had to be far apart to accommodate the low frequency or more stages were required to compensate for the low power at each stage.

Either way, higher-energy particles required longer accelerators than scientists could afford. Modern linacs use high power Klystrons and other devices able to impart much more power at higher frequencies. But before these devices existed, cyclotrons were cheaper than linacs. Cyclotrons accelerate particles in a spiral path. Therefore, a compact accelerator can contain much more distance than a linear accelerator, with more opportunities to accelerate the particles. Advantages of the cyclotron • Cyclotrons have a single electrical driver, which saves both money and power, since more expense may be allocated to increasing efficiency. • Cyclotrons produce a continuous stream of particles at the target, so the average power is relatively high. • The compactness of the device reduces other costs, such as its foundations, radiation shielding, and the enclosing building. Limitations of the cyclotron e magnet portion of a large cyclotron. The gray object is the upper pole piece, routing the magnetic field in two loops through a similar part below. The white canisters held conductive coils to generate the magnetic field. The D electrodes are contained in a vacuum chamber that was inserted in the central field gap.

The spiral path of the cyclotron beam can only "synch up" with klystron-type (constant frequency) voltage sources if the accelerated particles are approximately obeying Newton's Laws of Motion. If the particles become fast enough that relativistic effects become important, the beam gets out of phase with the oscillating electric field, and cannot receive any additional acceleration. The cyclotron is therefore only capable of accelerating particles up to a few percent of the speed of light. To accommodate increased mass the magnetic field may be modified by appropriately shaping the pole pieces as in the isochronous cyclotrons, operating in a pulsed mode and changing the frequency applied to the dees as in the synchrocyclotrons, either of which is limited by the diminishing cost effectiveness of making larger machines. Cost limitations have been overcome by employing the more complex synchrotron or linear accelerator, both of which have the advantage of scalability, offering more power within an improved cost structure as the machines are made larger.

Mathematics of the cyclotron [edit] Non-relativistic The centripetal force is provided by the transverse magnetic field B, and the force on a particle travelling in a magnetic field (which causes it to be angularly displaced, i.e spiral) is equal to Bqv. So, (Where m is the mass of the particle, q is its charge, v is its velocity and r is the radius of its path.) The speed at which the particles enter the cyclotron due to a potential difference, V. Therefore, v/r is equal to angular velocity, ω, so And since the angular frequency is ω = 2πfc Therefore, A pair of "dee" electrodes with loops of coolant pipes on their surface at the Lawrence Hall of Science. The particle exit point may be seen at the top of the upper dee, where the target would be positioned This shows that for a particle of constant mass, the frequency does not depend upon the radius of the particle's orbit. As the beam spirals out, its frequency does not decrease, and it must continue to accelerate, as it is travelling more distance in the same time.

As particles approach the speed of light, they acquire additional mass, requiring modifications to the frequency, or the magnetic field during the acceleration. This is accomplished in the synchrocyclotron. Relativistic The radius of curvature for a particle moving relativistically in a static magnetic field is where the Lorentz factor Note that in high-energy experiments energy, E, and momentum, p, are used rather than velocity, and both measured in units of energy. In that case one should use the substitution, where this is in Natural units The relativistic cyclotron frequency is , fc is the classical frequency, given above, of a charged particle with velocity v circling in a magnetic field. The rest mass of an electron is 511 keV, so the frequency correction is 1% for a magnetic vacuum tube with a 5.11 kV direct current accelerating voltage. The proton mass is nearly two thousand times the electron mass, so the 1% correction energy is about 9 MeV, which is sufficient to induce nuclear reactions. An alternative to the synchrocyclotron is the isochronous cyclotron, which has a magnetic field that increases with radius, rather than with time.

The de-focusing effect of this radial field gradient is compensated by ridges on the magnet faces which vary the field azimuthally as well. This allows particles to be accelerated continuously, on every period of the radio frequency, rather than in bursts as in most other accelerator types. This principle that alternating field gradients have a net focusing effect is called strong focusing. It was obscurely known theoretically long before it was put into practice. Related technologies • The spiraling of electrons in a cylindrical vacuum chamber within a transverse magnetic field is also employed in the magnetron, a device for producing high frequency radio waves (microwaves). • The Synchrotron moves the particles through a path of constant radius, allowing it to be made as a pipe and so of much larger radius than is practical with the cyclotron and synchrocyclotron. The larger radius allows the use of numerous magnets, each of which imparts angular momentum and so allows particles of higher velocity (mass) to be kept within the bounds of the evacuated pipe.

The magnetic field strength of each of the bending magnets is increased as the particles gain energy in order ] [Betatron A betatron is a cyclotron developed by Donald Kerst at the University of Illinois in 1940 to accelerate electrons. The betatron is essentially a transformer with a torus-shaped vacuum tube as its secondary coil. An alternating current in the primary coils accelerates electrons in the vacuum around a circular path. • How it works In a betatron, the magnetic field spins the injected electrons and accelerates them at the center where there is a ring-shaped vacuum tube changing the magnetic field and producing an electric field in the vacuum ring. The stable orbit for the electrons satisfies where θ0 is the flux with the orbit at r0 is the radius and H0 is the magnetic field at r0. In other words, the magnetic field at the orbit must be half the average magnetic field over its circular cross section. Etymology The name "betatron" (a reference to the beta particle, a fast electron) was chosen during a departmental contest.

Other proposals were rheotron, inductron, and even Ausserordentlichhochgeschwindigkeitelektronenentwickelndenschwerarbeitsbeigollitron, supposedly German for "extraordinarily high-speed electron producing hard work by golly-tron.". Applications Betatrons were historically employed in particle physics experiments to provide high energy beams of electrons—up to about 300 MeV. If the electron beam is directed at a metal plate, the betatron can be used as a source of energetic x-rays or gamma rays; these x-rays may be used in industrial and medical applications (historically in radiation oncology). The Radiation Center, the first private medical center to treat cancer patients with a betatron was opened by Dr. O. Arthur Stiennon, in a suburb of Madison, Wisconsin in the late 1950s[1]. Limitations Because the mass of the electron increases at relativistic speeds, the cyclotron becomes less efficient at higher energies, placing an upper limit on its beam energy. These relativistic effects are accommodated in the next generation of accelerators, the Synchrotrons.

Synchrocyclotron A part of a magnet from the Orsay synchrocyclotron, now used by the proton therapy center (to be replaced in 2008 by newer technologies) A synchrocyclotron is a cyclotron in which the frequency of the driving RF electric field is varied to compensate for the mass gain of the accelerated particles as their velocity begins to approach the speed of light. This is in contrast to the classical cyclotron, where the frequency was held constant. It differs from a cyclotron in that it has a single D(ee) instead of two Ds. Synchrocyclotrons have not been built since the isochronous cyclotron was developed. Isochronous cyclotrons maintain a constant RF driving frequency and compensate for the relativistic mass gain of the accelerated particles by increasing the magnetic field with radius. Isochronous cyclotrons are capable of producing much greater beam current than synchrocyclotrons. See also • Cyclotron — this contains a mathematics section that assumes constancy of mass, and an extensive see also section.

• Betatron SYNCHROCYCLOTRON The two fundamental differences between this machine and the orthodox cyclotron are that (1) in this machine, only one dee is used instead of two & (2) the frequency of oscillating electric field is made to decrease continuously instead of keeping it constant so as to maintain the resonance with ion frequency. One terminal of the oscillating electric potential varying periodically is applied to the dee and the other terminal is earthed. The proton or deuterons to be accelerated are made to move in circles of increasing radii. The acceleration of particles takes place as they enter or leave D. at the outer edge, the ion beam can be removed with the aid of electrostatic deflector. It was possible to produce 200MeV deuterons and 400MeV α-particle with the first synchrocyclotron ADVANTAGES The chief advantage of the synchrocyclotron is that there is no need to restrict the no of revolutions executed by the ion before its exit. As such, the potential difference supplied between the dees can be much smaller. The smaller potential difference needed across the gap has the following uses: 1.

There is no need for a narrow gap between the dees as in the case of convention cyclotron, because strong electric fields for producing large acceleration are not required. Thus only one dee can be used instead of two, the other end of the oscillating voltage supply being connected to earth. 2. The magnetic pole pieces can be brought closer, thus making it possible to increase greatly the magnetic flux density. 3. The frequency valve oscillator is able to function with much greater efficiency. The main drawback of this device is that, as a result of the variation in the frequency of the oscillating voltage supply, only a very small fraction of the ions leaving the source are captured in phase-table orbits of maximum radius and energy so that the output beam current is rendered weak.

Thus the machine produces high energy ions, though of small intensity Large Hadron Collider The Large Hadron Collider (LHC) is the world's largest and highest-energy particle accelerator, intended to collide opposing beams of protons or lead ions, each moving at approximately 99.999999% of the speed of light.[1] The LHC was built by the European Organization for Nuclear Research (CERN) with the intention of testing various predictions of high-energy physics, including the existence of the hypothesised Higgs boson[2] and of the large family of new particles predicted by supersymmetry.[3] 27 kilometres (17 mi) in circumference, it lies underneath the Franco-Swiss border between the Jura Mountains and the Alps near Geneva, Switzerland.

It is funded by and built in collaboration with over 10,000 scientists and engineers from over 100 countries as well as hundreds of universities and laboratories.[4] On 10 September 2008, the proton beams were successfully circulated in the main ring of the LHC for the first time.[5] On 19 September 2008, the operations were halted due to a serious fault between two superconducting bending magnets.[6] The LHC will not be operational again until the summer of 2009.[7] The LHC was officially inaugurated on 21 October 2008,[8] in the presence of political leaders, science ministers from CERN's 20 Member States, CERN officials, and members of the worldwide scientific community.[9] • Purpose A simulated event in the CMS detector, featuring the appearance of the Higgs boson. A Feynman diagram of one way the Higgs boson may be produced at the LHC. Here, two quarks each emit a W or Z boson, which combine to make a neutral Higgs.

It is theorised that the collider will produce the elusive Higgs boson, the last unobserved particle among those predicted by the Standard Model. The verification of the existence of the Higgs boson would shed light on the mechanism of electroweak symmetry breaking, through which the particles of the Standard Model are thought to acquire their mass. In addition to the Higgs boson, new particles predicted by possible extensions of the Standard Model might be produced at the LHC. More generally, physicists hope that the LHC will enhance their ability to answer the following questions:[10] • Is the Higgs mechanism for generating elementary particle masses in the Standard Model indeed realised in nature?[11] If so, how many Higgs bosons are there, and what are their masses? • Are electromagnetism, the strong nuclear force and the weak nuclear force just different manifestations of a single unified force, as predicted by various Grand Unification Theories? • Why is gravity so many orders of magnitude weaker than the other three fundamental forces? See also Hierarchy problem. • Is Supersymmetry realised in nature, implying that the known Standard Model particles have supersymmetric partners?

• Will the more precise measurements of the masses and decays of the quarks continue to be mutually consistent within the Standard Model? • Why are there apparent violations of the symmetry between matter and antimatter? See also CP-violation. • What is the nature of dark matter and dark energy? • Are there extra dimensions[12], as predicted by various models inspired by string theory, and can we detect them? Of the possible discoveries the LHC might make, only the discovery of the Higgs particle is relatively uncontroversial, but even this is not considered a certainty. Stephen Hawking said in a BBC interview that "I think it will be much more exciting if we don't find the Higgs. That will show something is wrong, and we need to think again. I have a bet of one hundred dollars that we won't find the Higgs." In the same interview Hawking mentions the possibility of finding superpartners and adds that "whatever the LHC finds, or fails to find, the results will tell us a lot about the structure of the universe."[13] As an ion collider The LHC physics program is mainly based on proton–proton collisions.

However, shorter running periods, typically one month per year, with heavy-ion collisions are included in the program. While lighter ions are considered as well, the baseline scheme deals with lead ions.[14] (see A Large Ion Collider Experiment). This will allow an advancement in the experimental program currently in progress at the Relativistic Heavy Ion Collider (RHIC). The aim of the heavy-ion program is to provide a window on a state of matter known as Quark-gluon plasma, which characterized the early stage of the life of the Universe. Design The LHC is the world's largest and highest-energy particle accelerator.[15][16] The collider is contained in a circular tunnel, with a circumference of 27 kilometres (17 mi), at a depth ranging from 50 to 175 metres underground. Superconducting quadrupole electromagnets are used to direct the beams to four intersection points, where interactions between protons will take place. Once or twice a day, as the protons are accelerated from 450 GeV to 7 TeV, the field of the superconducting dipole magnets will be increased from 0.54 to 8.3 tesla (T).

The protons will each have an energy of 7 TeV, giving a total collision energy of 14 TeV (2.2 μJ). At this energy the protons have a Lorentz factor of about 7,500 and move at about 99.9999991% of the speed of light. It will take less than 90 microsecond (μs) for a proton to travel once around the main ring – a speed of about 11,000 revolutions per second. Rather than continuous beams, the protons will be bunched together, into 2,808 bunches, so that interactions between the two beams will take place at discrete intervals never shorter than 25 nanoseconds (ns) apart. However it will be operated with fewer bunches when it is first commissioned, giving it a bunch crossing interval of 75 ns.[18] CMS detector for LHC The LHC will also be used to collide lead (Pb) heavy ions with a collision energy of 1,150 TeV.

The Pb ions will be first accelerated by the linear accelerator LINAC 3, and the Low-Energy Injector Ring (LEIR) will be used as an ion storage and cooler unit. The ions then will be further accelerated by the PS and SPS before being injected into LHC ring, where they will reach an energy of 2.76 TeV per nucleon. Detectors The Large Hadron Collider's (LHC) CMS detectors being installed. Six detectors have been constructed at the LHC, located underground in large caverns excavated at the LHC's intersection points. Two of them, the ATLAS experiment and the Compact Muon Solenoid (CMS), are large, general purpose particle detectors.[16] A Large Ion Collider Experiment (ALICE) and LHCb have more specific roles and the last two TOTEM and LHCf are very much smaller and are for very specialized research. The BBC's summary of the main detectors is:[20] Test timeline The first beam was circulated through the collider on the morning of 10 September 2008.[21] CERN successfully fired the protons around the tunnel in stages, three kilometres at a time.

The particles were fired in a clockwise direction into the accelerator and successfully steered around it at 10:28 local time.[22] The LHC successfully completed its first major test: after a series of trial runs, two white dots flashed on a computer screen showing the protons traveled the full length of the collider. It took less than one hour to guide the stream of particles around its inaugural circuit.[23] CERN next successfully sent a beam of protons in a counterclockwise direction, taking slightly longer at one and a half hours due to a problem with the cryogenics, with the full circuit being completed at 14:59.

In the original timeline of the LHC commissioning, the first "modest" high-energy collisions at a center-of-mass energy of 900 GeV were expected to take place before the end of September 2008, and the LHC was expected to be operating at 10 TeV by the time of the official inauguration on 21 October 2008.[27] However, due to the delay caused by the above-mentioned incident, the collider will not be operational again until spring 2009, after the winter shutdown which had already been scheduled to start at the end of November 2008.[28] In the meantime, the superconducting magnets will be trained to work at the full current throughput,[29] such that the LHC will reach the full 14 TeV design energy in the 2009 run.[18] Expected results Once the supercollider is up and running, CERN scientists estimate that if the Standard Model is correct, a single Higgs boson may be produced every few hours. At this rate, it may take up to three years to collect enough data unambiguously to discover the Higgs boson.

Similarly, it may take one year or more before sufficient results concerning supersymmetric particles have been gathered to draw meaningful conclusions.[15] Proposed upgrade Main article: Super Large Hadron Collider After some years of running, any particle physics experiment typically begins to suffer from diminishing returns; each additional year of operation discovers less than the year before. The way around the diminishing returns is to upgrade the experiment, either in energy or in luminosity. A luminosity upgrade of the LHC, called the Super LHC, has been proposed,[30] to be made after ten years of LHC operation. The optimal path for the LHC luminosity upgrade includes an increase in the beam current (i.e., the number of protons in the beams) and the modification of the two high-luminosity interaction regions, ATLAS and CMS. To achieve these increases, the energy of the beams at the point that they are injected into the (Super) LHC should also be increased to 1 TeV. This will require an upgrade of the full pre-injector system, the needed changes in the Super Proton Synchrotron being the most expensive.

Cost The total cost of the project is expected to be €3.2–6.4 billion.[16] The construction of LHC was approved in 1995 with a budget of 2.6 billion Swiss francs (€1.6 billion), with another 210 million francs (€140 million) towards the cost of the experiments. However, cost over-runs, estimated in a major review in 2001 at around 480 million francs (€300 million) for the accelerator, and 50 million francs (€30 million) for the experiments, along with a reduction in CERN's budget, pushed the completion date from 2005 to April 2007.[31] The superconducting magnets were responsible for 180 million francs (€120 million) of the cost increase.

There were also engineering difficulties encountered while building the underground cavern for the Compact Muon Solenoid, in part due to faulty parts loaned to CERN by fellow laboratories Argonne National Laboratory, Fermilab, and KEK.[32] David King, the former Chief Scientific Officer for the United Kingdom, has criticised the LHC for taking a higher priority for funds than solving the Earth's major challenges; principally climate change, but also population growth and poverty in Africa.[33] Computing resources The LHC Computing Grid is being constructed to handle the massive amounts of data produced by the Large Hadron Collider. It incorporates both private fiber optic cable links and existing high-speed portions of the public Internet, enabling data transfer from CERN to academic institutions around the world. The Open Science Grid is used as the primary infrastructure in the United States, and also as part of an interoperable federation with the LHC Computing Grid. The distributed computing project LHC@home was started to support the construction and calibration of the LHC. The project uses the BOINC platform, enabling anybody with an internet connection to use their computer idle time to simulate how particles will travel in the tunnel.

With this information, the scientists will be able to determine how the magnets should be calibrated to gain the most stable "orbit" of the beams in the ring.

Safety of particle collisions Main article: Safety of particle collisions at the Large Hadron Collider The upcoming experiments at the Large Hadron Collider have sparked fears among the public that the LHC particle collisions might produce doomsday phenomena, involving the production of stable microscopic black holes or the creation of hypothetical particles called strangelets.[34] Two CERN-commissioned safety reviews have examined these concerns and concluded that the experiments at the LHC present no danger and that there is no reason for concern,[35][36][37] a conclusion expressly endorsed by the American Physical Society, the world's second largest organization of physicists.[38] Operational challenges The size of the LHC constitutes an exceptional engineering challenge with unique operational issues on account of the huge energy stored in the magnets and the beams.[19][39] While operating, the total energy stored in the magnets is 10 GJ (equivalent to one and a half barrels of oil or 2.4 tons of TNT) and the total energy carried by the two beams reaches 724 MJ (about a tenth of a barrel of oil, or half a lightning bolt).[40] Loss of only one ten-millionth part (10−7) of the beam is sufficient

 to quench a superconducting magnet, while the beam dump must absorb 362 MJ, an energy equivalent to that of burning eight kilograms of oil, for each of the two beams.

These immense energies are even more impressive considering how little matter is carrying it: under nominal operating conditions (2,808 bunches per beam, 1.15×1011 protons per bunch), the beam pipes contain 1.0×10-9 gram of hydrogen, which, in standard conditions for temperature and pressure, would fill the volume of one grain of fine sand. On 10 August 2008, computer hackers defaced a website at CERN, criticizing their computer security. There was no access to the control network of the collider.[41][42] Construction accidents and delays • On 25 October 2005, a technician was killed in the LHC tunnel when a crane load was accidentally dropped.[43] • On 27 March 2007 a cryogenic magnet support broke during a pressure test involving one of the LHC's inner triplet (focusing quadrupole) magnet assemblies, provided by Fermilab and KEK. No one was injured. Fermilab director Pier Oddone stated "In this case we are dumbfounded that we missed some very simple balance of forces".

This fault had been present in the original design, and remained during four engineering reviews over the following years.[44] Analysis revealed that its design, made as thin as possible for better insulation, was not strong enough to withstand the forces generated during pressure testing. Details are available in a statement from Fermilab, with which CERN is in agreement.[45][46] Repairing the broken magnet and reinforcing the eight identical assemblies used by LHC delayed the startup date,[47] then planned for November 2007. • problems with a magnet quench on 19 September 2008 caused a leak of six tonnes of liquid helium, and delayed the operation for several months.[48] The LHC is expected to be restarted in June 2009.[49] In popular culture The Large Hadron Collider was featured in Angels & Demons by Dan Brown, which involves dangerous antimatter created at the LHC being used as a weapon against the Vatican.

CERN published a "Fact or Fiction?" page discussing the accuracy of the book's portrayal of the LHC, CERN, and particle physics in general.[50] The movie version of the book has footage filmed on-site at one of the experiments at the LHC; the director, Ron Howard, met with CERN experts in an effort to make the science in the story more accurate.[51] CERN employee Katherine McAlpine's "Large Hadron Rap"[52] surpassed three million YouTube views on 15 September 2008.[53][54][55] BBC Radio 4 commemorated the switch-on of the LHC on 10 September 2008 with "Big Bang Day".[56] Included in this event was a radio episode of the TV series Torchwood, with a plot involving the LHC, entitled Lost Souls.[57] CERN's director of communications, James Gillies, commented, "The CERN of reality bears little resemblance to that of Joseph Lidster's Torchwood script."[58] The LHC plays a major role in the science fiction novel Flashforward by Robert J. Sawyer.

As the first ion collisions occur in the ALICE detector everyone in the world experiences a two-minute 'flashforward' to a time twenty one years ahead. The novel, which received the Aurora Award in 1999, follows the efforts of CERN scientists to provide an explanation for the event and deal with the human problems presented by knowledge of the future. A TV adaptation is being developed by ABC.[59] In the Stargate: Atlantis episode Brain Storm, one of the main characters refers to the Hadron Collider as an example of a source of unnecessary paranoia in respect to a scientific experiment going wrong Posted by Cyclotron - New World Encyclopedia Cyclotron Next (Cynic) A modern cyclotron for radiation therapy. A cyclotron is a type of particle accelerator . Cyclotrons accelerate charged particles using a high- frequency , alternating voltage (potential difference). A perpendicular magnetic field causes the particles to spiral almost in a circle so that they re-encounter the accelerating voltage many times. Ernest Lawrence, of the University of California, Berkeley, is credited with development of the cyclotron in 1929, though others had been working along similar lines at the time.

Contents 11 Credits As a cyclotron accelerates particles in a spiral path, it allows particles to be accelerated over a greater distance than a linear accelerator. Cyclotrons provide high-energy beams for nuclear physics experiments and ion beams to treat cancerous tissue. They may also be used to bombard other atoms to produce short-lived, positron-emitting isotopes suitable for PET imaging . How the cyclotron works Diagram of cyclotron operation from Lawrence's 1934 patent. Beam of electrons moving in a circle. Lighting is caused by excitation of atoms of gas in a bulb. The electrodes shown at the right would be in the vacuum chamber, which is flat, in a narrow gap between the two poles of a large magnet. In the cyclotron, a high-frequency alternating voltage applied across the "D" electrodes (also called "dees") alternately attracts and repels charged particles. The particles, injected near the center of the magnetic field, accelerate only when passing through the gap between the electrodes. The perpendicular magnetic field (passing vertically through the "D" electrodes), combined with the increasing energy of the particles forces the particles to travel in a spiral path.

With no change in energy, the charged particles in a magnetic field will follow a circular path. In the cyclotron, energy is applied to the particles as they cross the gap between the dees and so they are accelerated (at the typical sub-relativistic speeds used) and will increase in mass as they approach the speed of light. Either of these effects (increased velocity or increased mass) will increase the radius of the circle and so the path will be a spiral. (The particles move in a spiral, because a current of electrons or ions, flowing perpendicular to a magnetic field, experiences a perpendicular force. The charged particles move freely in a vacuum, so the particles follow a spiral path.) The radius will increase until the particles hit a target at the perimeter of the vacuum chamber. Various materials may be used for the target, and the collisions will create secondary particles which may be guided outside of the cyclotron and into instruments for analysis. The results will enable the calculation of various properties, such as the mean spacing between atoms and the creation of various collision products. Subsequent chemical and particle analysis of the target material may give insight into nuclear transmutation of the elements used in the target.

Advantages of the cyclotron Cyclotrons have a single electrical driver, which saves both money and power, allowing more funds to be allocated to increasing efficiency Cyclotrons produce a continuous stream of particles at the target, so the average power is relatively high The compactness of the device reduces other costs, such as its foundations, radiation shielding, and the enclosing building Limitations of the cyclotron The spiral path of the cyclotron beam can only "synch up" with klystron-type (constant frequency) voltage sources if the accelerated particles are approximately obeying Newton's Laws of Motion. If the particles become fast enough that relativistic effects become important, the beam gets out of phase with the oscillating electric field, and cannot receive any additional acceleration. The cyclotron is therefore only capable of accelerating particles up to a few percent of the speed of light. To accommodate increased mass the magnetic field may be modified by appropriately shaping the pole pieces as in the isochronous cyclotrons, operating in a pulsed mode and changing the frequency applied to the dees as in the synchrocyclotrons, either of which is limited by the diminishing cost effectiveness of making larger machines.

Cost limitations have been overcome by employing the more complex synchrotron or linear accelerator, both of which have the advantage of scalability, offering more power within an improved cost structure as the machines are made larger. Problems solved by the cyclotron 60-inch cyclotron, c. 1939, showing a beam of accelerated ions (likely protons or deuterons) escaping the accelerator and ionizing the surrounding air causing a blue glow. This phenomenon of air ionization is analogous to the one responsible for producing the "blue flash" infamously noted by witnesses of criticality accidents. Though the effect is often mistaken for Cherenkov radiation, this is not the case. The cyclotron was an improvement over the linear accelerators that were available when it was invented. A linear accelerator (also called a linac) accelerates particles in a straight line through an evacuated tube (or series of such tubes placed end to end). A set of electrodes shaped like flat donuts are arranged inside the length of the tube(s). These are driven by high-power radio waves that continuously switch between positive and negative voltage, causing particles traveling along the center of the tube to accelerate.

In the 1920s, it was not possible to get high frequency radio waves at high power, so either the accelerating electrodes had to be far apart to accommodate the low frequency or more stages were required to compensate for the low power at each stage. Either way, higher-energy particles required longer accelerators than scientists could afford. Modern linacs use high power Klystrons and other devices able to impart much more power at higher frequencies. But before these devices existed, cyclotrons were cheaper than linacs. Cyclotrons accelerate particles in a spiral path. Therefore, a compact accelerator can contain much more distance than a linear accelerator, with more opportunities to accelerate the particles. Uses of the cyclotron For several decades, cyclotrons were the best source of high-energy beams for nuclear physics experiments. Several cyclotrons are still in use for this type of research. Cyclotrons can be used to treat cancer . Ion beams from cyclotrons can be used, as in proton therapy, to penetrate the body and kill tumors by radiation damage, while minimizing damage to healthy tissue along their path. Cyclotron beams can be used to bombard other atoms to produce short-lived positron-emitting isotopes suitable for PET imaging .

Mathematics of the cyclotron Non-relativistic The centripetal force is provided by the transverse magnetic field B, and the force on a particle travelling in a magnetic field (which causes it to be angularly displaced, that is, spiral) is equal to Bqv. So, (Where m is the mass of the particle, q is its charge, v is its velocity and r is the radius of its path.) The speed at which the particles enter the cyclotron due to a potential difference, V. Therefore, v/r is equal to angular velocity, ω, so And since the angular frequency is Therefore, This shows that for a particle of constant mass, the frequency does not depend upon the radius of the particle's orbit. As the beam spirals out, its frequency does not decrease, and it must continue to accelerate, as it is traveling more distance in the same time. As particles approach the speed of light, they acquire additional mass, requiring modifications to the frequency, or the magnetic field during the acceleration. This is accomplished in the synchrocyclotron.

Relativistic The radius of curvature for a particle moving relativistically in a static magnetic field is where the Lorentz factor Note that in high-energy experiments energy, E, and momentum, p, are used rather than velocity, and both measured in units of energy. In that case one should use the substitution, where this is in Natural units The relativistic cyclotron frequency is , is the classical frequency, given above, of a charged particle with velocity circling in a magnetic field. The rest mass of an electron is 511 keV, so the frequency correction is 1 percent for a magnetic vacuum tube with a 5.11 kV direct current accelerating voltage. The proton mass is nearly two thousand times the electron mass, so the 1 percent correction energy is about 9 MeV, which is sufficient to induce nuclear reactions. An alternative to the synchrocyclotron is the isochronous cyclotron, which has a magnetic field that increases with radius, rather than with time. The de-focusing effect of this radial field gradient is compensated by ridges on the magnet faces which vary the field azimuthally as well.

This allows particles to be accelerated continuously, on every period of the radio frequency, rather than in bursts as in most other accelerator types. This principle that alternating field gradients have a net focusing effect is called strong focusing. It was obscurely known theoretically long before it was put into practice. Related technologies Magnetron: The spiraling of electrons in a cylindrical vacuum chamber within a transverse magnetic field is also employed in the magnetron, a device for producing high frequency radio waves (microwaves). Synchrotron: The synchrotron moves the particles through a path of constant radius, allowing it to be made as a pipe. It can thus have a much larger radius than is practical with the cyclotron and synchrocyclotron. The larger radius allows the use of numerous magnets, each of which imparts angular momentum, and so allows particles of higher velocity (mass) to be kept within the bounds of the evacuated pipe. The magnetic field strength of each of the bending magnets is increased as the particles gain energy in order to keep the bending angle constant. See also

Question: Ernest Lawrence of the University of California, Berkeley, is credited with the development in 1929 of what type of particle accelerator that accelerates charged particles using a high-frequency, alternating voltage in a perpendicular magnetic field, causing them to spiral and encounter the accelerating voltage many times?
Answer: Cyclotron