Method of controlling beam of charged particles in cyclotron

FIELD: physics.

SUBSTANCE: method of controlling a beam of charged particles in a cyclotron involves focusing the beam in an axial injection system and turning the beam using the electric field of a spiral inflector from the axial direction in the axial injection system to the median plane of the cyclotron. The beam is further focused by the force of the electric field of the spiral inflector, which acts on particles diverging from the central trajectory in the direction across the direction of motion of the central particle on the central trajectory and across the direction of the turning force of the electric field, acting on the central particle moving on the central trajectory. Equipotential lines of the electric field in the inflector in the direction across the beam are concentric arc shaped.

EFFECT: significant reduction of axial dimensions and beam divergence at the output of the inflector, reduced longitudinal dimensions of the beam, best transmission coefficient of the beam in the cyclotron.

2 cl, 15 dwg

 

The technical field.

The invention relates to the field of cyclotron technology and can be used in cyclotrons with external injection system, which passes through axial axial channel in the yoke of the electromagnet of the cyclotron.

The level of technology.

Focusing of the beam during its transportation system external injection is performed by various electro-optical and magneto-optical elements. An important aspect in the management of the charged particle beam in the cyclotron is the rotation of the beam from the axial direction in the median plane of the cyclotron, where the acceleration. Known methods of effecting rotation of the beam from the axial direction in the median plane of the cyclotron, which consists in the fact that:

1. The beam affects the turning force of the electric field of a plane capacitor (electrostatic mirror) with the direction of the field approximately 45° to the movement of the beam (P. Mandrillon, "Injection into cyclotrons", In proceedings of the CERN accelerator school, 28 April - 5 May 1994, Belgium, p.153-168). This effect is greatly deteriorate the optical properties of the rotatable beam, which reduces the efficiency of its acceleration in the cyclotron. In addition, a double pass of the beam through the mesh, forming a rotating electric field, leads to the loss of intensity of the beam, the beam has a damaging of vozdeystviyna a grid of mirrors and affects the operational characteristics of the inflector.

2. The beam affects the turning force of the electric field of the inflector, formed in a parabolic or hyperbolic laws. The choice of these forms of influence on the beam requires off-axis beam injection. In addition, relevant inflectors are large, which requires additional space for their accommodation in the centre of the cyclotron. For these reasons, this method has not found wide application in cyclotron technology (R.W.Muller. "Novel inflectors for cyclic accelerators", Nucl. Instr. and Meth. 54, 1967, p.29-41).

3. The closest to the specified invention a method of controlling the charged particle beam in the cyclotron, figure 1, is the effect on the beam turning force of the electric field of the inflector, formed with the influence on the beam magnetic field so that at each point of the trajectory of the Central particle beam electric field is directed perpendicular to the velocity of the Central particle (D.V.Altiparmakov, P.Belicev. "Numerical simulation of Real VS Theoretical Spiral Inflector", In proceedings of the 15thConference on Cyclotrons and Their Applications, 14-19 June 1998, Caen, France, p.536-539), (prototype). The corresponding electric field is formed in the spiral inflector, which is characterized by its compactness and the optimal combination of conditions of production and operation. However, the influence of electric and magnetic fields on the charged beam h is stitz when his turn in the spiral inflector leads to an increase of the vertical emittance and, accordingly, the size of the beam. The beam at the exit of the inflector is always vertically divergent. Such effects on the beam passing through the spiral inflector, is the factor limiting the efficiency of the acceleration in the cyclotron. As an example for comparative analysis, we consider the influence of electric and magnetic fields on the test charged particle beam during its rotation in the spiral inflector with transverse emittance at the entrance to the inflector presented in figure 2 and 3. When turning the test beam in a spiral inflector cross emittance transformed into the form presented in figure 4 and 5.

Cross emittance test beam at the entrance and the exit of the inflector represented in the phase plane distance (u, h) - pulse (pu, ph) of the moving system of coordinates tied to the movement of the center of the particle along the Central trajectory, with the direction transverse to the axes u and h as shown in Fig.

The presented results show that the passage of the spiral inflector there is a significant increase in the transverse emittance beam, especially vertical (u - direction). In addition, as in u and h directions of the beam at the exit of the inflector is divergent. This effect is illustrated also u (axial) and h (median) profiles of the test beam when it is passing through the spiral inflector, which are presented in Fig.6 and 7, respectively.

Another feature of the passage of a charged particle beam through the spiral inflector is the appearance of additional longitudinal size of the beam. This feature is associated with a different path length, which pass the charged particle beam when turning in the inflector. In this example, the longitudinal size of the test beam at the entrance of the inflector is taken equal to zero. With the passage of the spiral inflector longitudinal size of the test beam is increased to ±11° from the phase of the accelerating RF voltage Fig.9. The increase in the longitudinal size of the beam leads to a decrease in the efficiency of the acceleration in the cyclotron. Presents the behavior of the beam when passing through the spiral inflector is typical for any shape of the beam at the entrance of the inflector.

Disclosure of the invention.

One of the most important parameters for restricting the movement of a charged particle beam acceleration in the cyclotron, is the aperture of the magnetic and accelerating cyclotron systems that determine the vertical size of the beam.

The invention solves the problem of increasing the efficiency of acceleration of the beam in the cyclotron by:

1. reduce vertical angular divergence and beam size at the beginning of the acceleration, i.e., after the output beam of the spiral inflector.

2. reduce dopolnitelnoj the longitudinal size of the beam, caused by passing the beam through the spiral inflector.

The essence of the present invention is that the beam of charged particles accelerate in the cyclotron with the axial injection system, turning the beam from the axial direction in the axial injection system in the median plane of the cyclotron electric field in the spiral inflector. The beam advanced focus the strength of the electric field of the spiral inflector, which acts on particles that deviate from the main path, in the direction transverse to the direction of motion of the Central particle of the Central path and transverse to the direction of the turning force of the electric field acting on the Central particle, moving along the Central trajectory. This equipotential lines of the electric field in the inflector have the shape of concentric arcs in the direction transverse to the direction of movement of the beam.

Distinctive features of the invention are:

1. additional focusing of the charged particle beam strength of the electric field of the spiral inflector;

2. the shape of the equipotential lines of the electric field in the inflector in the form of concentric arcs in the direction transverse to the direction of movement of the beam.

The technical result of the use of additional focusing power of e is aktionscode field spiral inflector is expressed in a significant reduction in axial size and divergence of the beam at the exit of the inflector, that provides the best coefficient of the beam in the cyclotron. The technical result of the invention also be seen in the reduction of the longitudinal size of the beam caused by passing the beam through the spiral inflector. This effect allows to increase the efficiency of the grouping of the beam and to increase the trapping beam in the acceleration in the cyclotron center.

In turn, more focus is provided by the effect on the beam of the electric field of the spiral inflector formed so that the equipotential lines of the field have the form of concentric arcs in the direction transverse to the movement of the beam.

Consider the use of additional focusing of the beam strength of the electric field of the spiral inflector. For the comparative analysis will take used in the previous example, the cross-emittance at the entrance to the inflector presented in figure 2 and 3. The motion of the charged particle beam through the spiral inflector under the action of turning and additionally focusing forces transverse emittance test beam at the exit of the inflector transformed into the form presented in figure 10 and 11. Profiles of the test beam in u (axial) and h (median) directions when passing through the spiral inflector presented, with the responsibility on Fig and 13.

The results show that the proposed method is more focus can significantly reduce the vertical size and the beam divergence at the exit of the inflector. It should be noted that this increases the size of the beam in the median transverse direction. However, this does not reduce the efficiency of passage of the beam in the cyclotron center, as in the median direction of the aperture limitations in the cyclotron is not as significant as in axial.

The proposed method allows to reduce the longitudinal size of the beam caused by passing the beam inside the inflector, and thereby to increase the efficiency of acceleration of the beam in the cyclotron.

In the above example, the use of additional focusing of the beam made it possible to reduce the longitudinal size of the test beam at 1.5 times up to ±7° from the phase of the accelerating RF voltage, Fig against ±11° in the case where additional focus was not used, Fig.9.

List of figures.

Figure 1. Diagram of the cyclotron with the axial injection system and spiral inflector, where the numbers indicate:

1 - cyclotron electromagnet;

2 - accelerating cyclotron system;

3 - axial injection system;

4 - spiral inflector;

Figure 2. Transverse u-pu emittance of the test beam in the axial direction on whatev spiral inflector, the effective area of the emittance εrms=15 π·mm·mrad.

Figure 3. Transverse h-ph emittance test beam in

the median direction at the entrance to the spiral inflector, the effective area of the emittance εrms=18 π·mm·mrad.

Figure 4. Transverse u-pu emittance of the test beam in the axial direction at the exit of the spiral inflector, the effective area of the emittance εrms=110 π·mm·mrad.

Figure 5. Transverse h-ph emittance of the test beam in the median direction at the exit of the spiral inflector, the effective area of the emittance εrms=55 π·mm·mrad.

6. Profile of the test beam axis and with the passage of the spiral inflector.

7. Profile of the test beam axis h when passing through the spiral inflector.

Fig. View spiral inflector from the entrance.

Direction transverse to the axes u and h of the moving system of coordinates tied to the movement of the center of the particle along the Central trajectory:

u - axis in the axial direction;

h - axis in the median direction;

Eu- the turning direction of the electric field.

Fig.9. The percentage of the number of particles of the test beam at the exit of the spiral inflector, depending on the phase shift of the particle beam with respect to the Central particle.

Figure 10. Transverse u-pu emittance test beam (effective area εrms=38 π·mm·mrad) in the axial load is flax direction at the exit of the spiral inflector with more focus.

11. Transverse h-ph emittance test beam (effective area εrms=120 π·mm·mrad) in the median direction at the exit of the spiral inflector with more focus.

Fig. Profile of the test beam axis u with the passage of the spiral inflector with more focus.

Fig. Profile of the test beam axis h when passing through the spiral inflector with more focus.

Fig. The percentage of the number of particles of the test beam at the exit of the spiral inflector with additional focus depending on the phase shift of the particle beam with respect to the Central particle.

Fig. Form turning and additional focusing of the electric field of the spiral inflector.

The implementation of the invention.

The method of controlling the beam in the cyclotron includes additional focusing of the charged particle beam strength of the electric field of the spiral inflector by exposure to the beam passing through the spiral inflector, additional h (median) - component of the electric field is directed towards the centre of the working gap of the inflector. Effect of geometrical features of the movement of the beam in the spiral inflector additional focusing of the beam in h (median) direction leads to a significant reduction in the size and divergence of the beam in u (axialen the m direction at the exit of the inflector.

An example of performing the method. Figure 1 shows the diagram of the cyclotron. The beam received at the source of charged particles, focus and move along the line of axial injection into the cyclotron center. The rotation of the beam from the axial direction in the median plane of the cyclotron, as well as additional beam focusing is carried out by the electric field of the spiral inflector. At the exit of the inflector beam enters the working area of the cyclotron, where its acceleration.

Spiral inflector is an electrostatic capacitor, placed in the Central region of the cyclotron consists of two electrodes. The electric field generated between the electrodes acts on the charged particle beam passing between the electrodes, and rotate it 90 degrees from the axial direction in the median plane of the cyclotron. Exposure to electric and magnetic fields on the beam is characterized by electric and magnetic radii defined by the formulas:

Electric radius

The magnetic radius

where T is the kinetic energy, q is the charge of an ion,

Eo- the electric field strength, p is the time

In a magnetic field.

The Central trajectory of a particle in spirlnolactone represented by a system of equations in the coordinate system, attached to the center of the cyclotron:

where θ is the angle of rotation from 0° at the entrance to the inflector to 90° at the exit of the inflector, k' is the slope parameter of the electrodes.

As an example, consider the spiral inflector with electric radius equal to 45 mm, the magnetic radius equal to 35 mm, the inflector is designed to rotate the beam of charged particles48CA+8with respect to mass-to-charge A/Z=6 for acceleration in the cyclotron in the magnetic field of 1.24 T. In this case, the slope parameter of the electrodes k'=0. The distance between the electrodes of the inflector 12 mm when the width of the electrodes 30 mm

Turning the beam electric field in the spiral inflector is directed perpendicular to the velocity of the Central particle. The formation of a rotating electric field is carried out on the basis of the system of equations (3).

To provide additional focusing of the charged particle beam when it passes through the spiral inflector added to h (median) component of the electric field, directed to the center of the working gap of the inflector. For this purpose, the electric field of the inflector is formed so that the equipotential lines of the electric field in the transverse movement of the beam direction have the form of concentric d is g, as shown in Fig.

The required form of the electric field is achieved by making the electrodes form arcs in the transverse movement of the beam direction. The radius of curvature of the surface of the electrodes in the transverse movement of the beam direction in this example is 65 mm, While an additional component of the electric eld Eh, acting on the beam in h (median) direction. For additional h - component of the electric field was directed toward the center of the working gap of the inflector, the center of curvature of the arcs must be in the direction of the main rotating components of the electric field Unit. In this case a reduction of the radius of the arcs describing the equipotential lines, leads to increased exposure to additional focusing power. Accordingly, the increase of the radius of the arcs describing the equipotential lines, leads to a weakening of additional focusing power. Change the radius of the arcs describing the equipotential lines, allows you to change additional force focusing the beam as it passes through the spiral inflector, and thus gives an opportunity to optimize the conditions for the acceleration of the beam in the cyclotron.

1. The method of controlling the charged particle beam in the cyclotron, which includes the focus of the beam in the axial injection system and the rotation of the beam e the practical field in the spiral inflector from the axial direction in the axial injection system in the median plane of the cyclotron, characterized in that the beam advanced focus the strength of the electric field of the spiral inflector, which acts on particles that deviate from the main path, in the direction transverse to the direction of motion of the Central particle of the Central path and transverse to the direction of the turning force of the electric field acting on the Central particle, moving along the Central trajectory.

2. The method according to claim 1, characterized in that the equipotential lines of the electric field in the inflector have the shape of concentric arcs in the direction transverse to the movement of the beam.



 

Same patents:

The invention relates to nuclear engineering and is intended for use in the separation of charged particle energies, for example, at one stage of selection of isotopes from their natural mixture

FIELD: physics.

SUBSTANCE: method of controlling a beam of charged particles in a cyclotron involves focusing the beam in an axial injection system and turning the beam using the electric field of a spiral inflector from the axial direction in the axial injection system to the median plane of the cyclotron. The beam is further focused by the force of the electric field of the spiral inflector, which acts on particles diverging from the central trajectory in the direction across the direction of motion of the central particle on the central trajectory and across the direction of the turning force of the electric field, acting on the central particle moving on the central trajectory. Equipotential lines of the electric field in the inflector in the direction across the beam are concentric arc shaped.

EFFECT: significant reduction of axial dimensions and beam divergence at the output of the inflector, reduced longitudinal dimensions of the beam, best transmission coefficient of the beam in the cyclotron.

2 cl, 15 dwg

FIELD: physics.

SUBSTANCE: in compliance with this process, beam of particles is turned by electric field in helical inflector (2) from axial direction in the system of axial injection to cyclotron median plane. Note here that said inflector injects particles moving in trajectory (3) to create a spatial separation in vertical between their trajectories and inflector infrastructure. Thus, beam particle may not envelope the case of inflector (1), moving there under. Note here that beam particles vertical oscillations occur in symmetry with median plane owing to the fact that helical inflector is located so that its plates feature asymmetric position at its outlet relative to accelerator median plane. Inflector design allows the transfer of beam particles to cyclotron plane at a definite angle. Particle with sufficient angle with median plane of cyclotron deflects from vertical and at a distance therefrom sufficient for its trajectory to be located at different level in vertical relative to inflector case.

EFFECT: axial beam injection into compact cyclotron with superhigh magnetic field.

7 dwg

FIELD: physics.

SUBSTANCE: deflecting plate (210) for deflecting charged particles is made in the form of a metal-coated printed circuit board, the deflecting plate (210) having a recess (300) formed in the metal coating.

EFFECT: generation of an electric field with an improved spatial characteristic.

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