SU1462521A1 - Ionization sensor of cross-sectional distribution of a charged particle beam - Google Patents

Description

The invention relates to the technique of a physical experiment, in particular I to accelerator technology and can be used on accelerators of various types to measure the transverse distribution in beams of charged particles.

The aim of the invention is to increase the speed and noise immunity.

The drawing shows a diagram of the proposed sensor.

The drawing shows the studied beam 1 extracting capacitor 2 with a reflective 3 and extracting 4 electrodes connected to different poles of a DC voltage source 5, a two-coordinate position-sensitive, for example matrix, collector 6, connected to the extracting capacitor through a resistive voltage divider 9. Extracting electrode 4 made with a slit perpendicular to the axis of the extracting capacitor. An analysis capacitor 8 is placed behind the extraction electrode 4 so that its electric field is directed perpendicular to the slit 10 of the extraction electrode 4 and at an angle of 45 ° to the axis of the extraction capacitor

2 -; - The input plate of the analyzing capacitor 8 is provided with a slot 1 1, a coaxial slot 10 of the extracting electrode-4. The position-sensitive collector 6 is placed on the inner side of the input plate of the analyzing capacitor 8.

o The sensor operates as follows. The investigated beam 1 ionizes the residual gas of the beam transport path. The electric field of the extracting capacitor 2 formed by the reflective 3 and the extracting 4 electrodes connected to different poles of the DC voltage source 5, ionization particles, for example electrons, are simultaneously transferred to the plane of the extracting electrode'4. The electrons entering the slot 10 of the extracting electrode 4 form a ribbon beam, the spatial distribution in which in the direction along the slot 10 corresponds to the density distribution of the investigated beam 1 in this direction. Since ionizing electrons in a uniform electric field acquire energy proportional to the distance traveled, the energy distribution of electrons in the ribbon beam corresponds to the density distribution of the studied beam in the extraction direction. After the passage of the gap 11, the ribbon bundle by the electric field of the analyzed capacitor 8 is directed to the two-coordinate position-sensitive collector 6.

In the case when the electric field of the analyzing capacitor 8 is directed at an angle of 45 ° to the initial direction of movement of the ribbon beam, the distance V from the gap 11 to the point where the ionization electron hits the collector is related to the distance X from the origin of the electron to the pulling electrode 4 by the ratio

Y = 2- | ^ - X, (1) where E <and E _r are the intensities of the extracting and analyzing fields, respectively. The speed acquired by the electron in the extracting electric field, v

where e, ta is the charge and mass recoverable. particles.

Unfolding the electron velocity parallel to V _{1 (} and vertical V _A relative to the plane of the analyzing capacitor 8 components, taking into account the fact that sin 45 ° = cos 45 *, we have

Conditions for electron to hit the collector:

where t is the electron motion time in the analyzer 8, and = eEi is the particle acceleration in this m field.

Where from

Of distances

2eE <"mm eE ₂

and the maximum distance Z _{e of the} electron from the input plate of the analyzing capacitor 8

Z = —— X

E

As a result, a two-coordinate distribution of ionization electrons is formed on collector 6, which is incident on the braking plate of the analyzing capacitor 8, which eliminates the formation of false secondary emission flows in this plate5.

The connection of the analyzing capacitor 8 with the extracting capacitor 2 through the resistive voltage divider 9 ensures the constancy of the E отношения ratio regardless of the magnitude K of the supply voltage. This means that the scale of the distribution of ionization particles on the collector 6 does not depend on the magnitude of the supply voltage, which significantly reduces the requirements for a constant voltage source.

corresponding to the density distribution of the studied beam 1 in a transverse section of the plane drawn through slots 10 and 11 perpendicular to the extracting electrode 4. The distribution scale on the collector 6 in the direction perpendicular to the extraction direction is always 1: 1, as in a conventional profilometer. The scale in the direction of extraction is determined by the ratio indicated above and can be selected depending on the experimental conditions. So, when E ₂ = 2E |. the distribution scale on collector 6 in the extraction direction is also 1: 1, i.e. Y = X. The formation time of the distribution of ionization particles on the collector 6 corresponds to the time of their movement from the place of occurrence to the point of contact with the collector. When the characteristic size 1 00 mm and the extraction field intensity ¹ 1 kV / cm for the ionic components that time is l / 30-50 ns, for electrons ^ 1, 53 ns. The construction of high voltage sawtooth generators with such repetition periods is associated with very serious difficulties.

The application of the invention provides a high noise immunity of the sensor, since the secondary-emission electrons arising on the structural elements of the sensor under the action of scattered particles of the studied beam cannot enter the collector 6, since their energy either exceeds or is less than the energy of the electrons arising in the controlled region simple 20.

Claims (1)

Claim An ionization sensor for the distribution of the density of a beam of charged particles over a cross section, comprising a 25 extraction capacitor formed by a reflective and extraction electrodes connected to a constant voltage source, an analysis capacitor located 30 behind the extraction electrode, and a two-coordinate position-sensitive collector, while the extraction electrode is made a through slit oriented perpendicular 35 but to the longitudinal axis of the extraction capacitor, characterized in that, in order to increase For the speed and noise immunity of the sensor, the analyzing capacitor is galvanically connected to the extraction capacitor through a resistive divider, the electrodes of the analyzing capacitor are oriented at an angle of 45 to the axis of the extraction capacitor, 45 a gap is made in the input electrode of the analyzing capacitor, the coaxial passage gap of the extracting electrode, and the collector is placed on the inner surface 50 of the input electrode, while the distance Y from the center of this gap to the center of the collector and the transverse dimension X of the region controlled space, as well as the distance Z 55 between the electrodes of the analyzing capacitor and the distance X _max between the reflective and extracting electrodes are selected according to the following. At the same time, they cannot expressions where E *. and E _g is the electric field B between the reflective and extracting electrodes and the electric field of the analyzing capacitor, respectively.