SU600637A1 - Drift chamber - Google Patents

Description

one

The invention relates to technical physics, namely to wire coordinate detectors of accelerated elementary particles in experimental studies.

A drift chamber is known, which is a cavity filled with a mixture of gases of a certain composition, inside of which there is a flat periodic structure formed by a system of thin wires stretched one parallel to the other. The elementary cell of this periodic structure consists of a signal element and two drift gaps symmetrically arranged with respect to it, bounded by wires located along the perimeter of a rectangular section. These wires drift gap serves the distributed electric potential so that in the internal volume to obtain a uniform electrostatic field directed to the signal element 1.

When charged particles pass through the volume of the drift gap, a chain of electrons is formed along the particle trajectory in the gas, which, under the action of an electrostatic field, moves uniformly (“dip”) to the signal element. A thin wire (about 20 microns in diameter) is usually used as a signal element; A positive potential is applied to it, which is high enough so that near the wire, in the region of high electric field strength, the propagation of drifting electrons takes place under the action of the impact ionization mechanism.

Measuring the time between the passage of a particle and the appearance of an electrical signal on a signal element and the electron drift velocity in the finished mixture, determine the distance from the signal element to the point of passage of the particle, i.e. its coordinate.

When an electron cloud is planted from the propagated drift electrons, an electrical signal appears on the wire of the signal element.

Closest to the invention is the drift chamber, which is an elongated parallelepiped formed by drift-gap wires stretched between two boards along the perimeter of the transverse rectangular section; In the geometric center of the cross section, a signal element from a pair of closely spaced wires (1 mm) lying on both sides of the plane of the longitudinal symmetry of the chamber is pulled. When a charged particle emerges in the left drift gap, an electronic slug is planted on the left wire of the signal element, and when it passes in the right drift gap, on the right, i.e.

It uniquely determines the coordinate of the particle 2.

However, in such a drift chamber, despite the fact that the electronic trace rather strictly preserves the shape of the trajectory of the part along the entire drift path, the information not only from one wire of the signal element prevents the track from being recovered, but only restores one coordinate. Therefore, it is necessary to take a package from the chambers, which leads to an increase in the size of the experimental setup. In addition, in this chamber, one signal element requires two channels of electronics — one for each of a pair of wires. Only one channel is involved in the work, either left or right, i.e., the electronics are used in half. At the same time, significant electrostatic repulsive forces between closely spaced wires of a signal element with an increase in the chamber length (length of wires) require considerable complication of the signal element design.

The aim of the invention is to eliminate these drawbacks, namely the possibility of unambiguously determining the track (and ne coordinates) of the particle, increasing the length of the chamber and maximizing the effective use of the electronics channels.

Said object is achieved in that the signaling element drift chamber vynolnen mnogonrovolochnym, wherein several signal irovolok arranged sequentially in the depth camera interleaved at step transversality offset relative to the plane of the camera symmetry around each signal wire has cathode nrovoloki such that they form vertices of an isosceles transom, the middle line of which is in the plane of symmetry.

All of the rollers are mounted on two frame frames, which are fastened with transverse struts to the inner sides of the thin-walled metal box of rectangular section enclosed in the chamber, electrically insulated from the inside at high potential areas, and the ends of the box are sealed with plugs.

FIG. 1 schematically shows the proposed drift chamber, general view; in fig. 2 - the same cross section; in fig. 3 - the central part of the chamber and the signal element.

In the proposed drift chamber, on both sides of the multiwire signal element, there are gaps bounded by stringers 1 along the perimeter of a rectangular section. The signal element consists of several signal thin wires 2 connected through resistors 3 to the anode lamella + U &. From the signal lines 2 there are leads to the amplifiers of the electronics channels. Anode wires 4 are laid at the beginning and at the end of the signal element, also

connected to the anode lamella +: 6a, but not having outputs to the amplifiers. Signal wires 2 are surrounded by cathode wires 5, which form the tops of an isosceles tranecia. All wires are fixed on two non-rectangular frame frames 6 of electrically insulating material, which are attached with cross-section struts 7 to a thin-walled metal box 8 of rectangular cross-section, glued inside from the inside, protecting the box in areas of high potentials. The ends of the box sealed with plugs.

Drift camera works as follows.

Voltage 1 of the drift gap is supplied with a constant voltage, increasing from the value of UQ on the central to the max.

extreme wires, for example, with the help of a reznstorny divider stress (as shown in Fig. 2 and 3). The cathode wires 5 are interconnected and with the central wires of the drift gap (in FIG.

3 with the same digital indices at the potential and shown at the wires connected to each other and under the same potential). On the anode wire 4 and the signal wire 2 serves positive

potential + f / a. As a result, electrostatic uniform zero voltages of E, directed towards the sigal element of the drift chamber, are formed inside the drift points, and the electrostatic forces,

acting on the signal wires 2 are practically balanced.

With the passage of the charged particle through the base of the drift gap, a chain of free

electrons - track (for example in Fig. 3, such a track is shown by a pictor). Under the action of electrostatic iol E, the intensity of the electron chain drifts at a constant speed from right to left and lands

In parts along all the signal wires 2 from the bottom to the top. Since the signal wires are laid out with displacement, on any track the electrical impulses on them appear non-simultaneously,

The corresponding electronics can restore the track in the form of digital information, which is not suitable for further automatization of processing in scientific research.

The advantages of the proposed drift chamber are as follows;

a) one cell of the drift chamber makes it possible to unambiguously restore the full projection of the particle track, giving at least three coordinates

when using all channels of electronics;

b) each signal wire operates on the left side and on the left drift point;

c) as shown by experimental studies, the cathode electrodes surrounding

the signal electrode allows one to balance the electrostatic forces acting on the signal electrode, as a result of which there is a real opportunity to increase the length of the elementary cell of the drift chamber to 3 m or more, which is very important for modern research facilities.

Claims (2)

1. A drift chamber, made in the form of an elongated parallelepiped of thin wires located along the perimeter of the transverse rectangular section, with a signal element in the plane of longitudinal symmetry, which in order to unambiguously determine the particle track while simultaneously increasing the chamber length, the signal the chamber element is made of multi-wire, with several signal pro; ii, and around each signal wire cathode wire so arranged that they form the vertices of an isosceles trapezium, the middle line of which is in the symmetry of the symmetry. 2. A chamber according to claim 1, characterized in that all the wires are fixed on two frame frames, which by means of transverse struts are attached to the inner sides of the thin-walled metal box of rectangular cross section enclosed in the chamber, in areas of high potentials, and the ends of the box sealed with plugs. Sources of information taken into account in the examination 1. Materials of the international conference on the method of wire chambers. Dubna, JINR, D13-164, 1975, p. 38 2.Walenta, A.N. "Nucl Instr and Methods, 111, 1973, 467. VTV --r; -v-rf f