Synchrocyclotron

# Synchrocyclotron

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Encyclopedia

A synchrocyclotron is a cyclotron
Cyclotron
In technology, a cyclotron is a type of particle accelerator. In physics, the cyclotron frequency or gyrofrequency is the frequency of a charged particle moving perpendicularly to the direction of a uniform magnetic field, i.e. a magnetic field of constant magnitude and direction...

in which the frequency of the driving RF
Radio frequency is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals...

electric field
Electric field
In physics, an electric field surrounds electrically charged particles and time-varying magnetic fields. The electric field depicts the force exerted on other electrically charged objects by the electrically charged particle the field is surrounding...

is varied to compensate for relativistic effects as the particles' velocity begins to approach the speed of light
Speed of light
The speed of light in vacuum, usually denoted by c, is a physical constant important in many areas of physics. Its value is 299,792,458 metres per second, a figure that is exact since the length of the metre is defined from this constant and the international standard for time...

. This is in contrast to the classical cyclotron, where the frequency was held constant.

The two fundamental differences between this machine and the orthodox cyclotron are that
1. in this machine, only one dee
Dee
-Surname:*Arthur Dee, son of John Dee*Billy Dee*Bob Dee*Daisy Dee*Dave Dee*Ed Dee*Frances Dee, actress*Gandra Dee*Gerry Dee, Canadian comedian*Jack Dee, British comedian*Jeff Dee*John Dee, English mathematician and alchemist...

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

Synchrocyclotrons have not been built since the isochronous cyclotron was developed.

Isochronous cyclotron
Isochronous cyclotron
In particle accelerators an Isochronous cyclotron is a cyclotron that maintains a constant RF driving frequency, and compensates for the relativistic mass gain of the accelerated particles by alternating field gradient in space but constant in time...

s maintain a constant RF driving frequency and compensate for relativistic effects by increasing the magnetic field with radius. Isochronous cyclotrons are capable of producing much greater beam current than synchrocyclotrons.

The chief advantage of the synchrocyclotron is that there is no need to restrict the number 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