DE1491465A1 - Collecting electrode for an electron beam tube, especially high-power traveling wave tubes - Google Patents

Description

H9U65

Siemens & Halske Munich 2, 9/21/6 $

Aktiengesellschaft Wittelabacherplatz 2

pa 65/2923

Collecting electrode for a cathode ray tube, in particular High performance traveling wave tube

The invention relates to a cathode ray tube, in particular a traveling wave tube of high power, with a Electron beam receiving cup-shaped collecting electrode, which is arranged coaxially to the beam axis and has a rotationally symmetrical interior, which has a changing inner diameter

909821/0415

USHBS

PA 9/492/499 - 2 -

has and in which the electron beam is concentric spreads to the beam axis.

Running time tubes such as Klystron intensifying stirrers or traveling wave tubes are known to require a collecting electrode for the electron beam. Such Collecting electrodes are generally in the form of a Cup-shaped metal parts, which are arranged coaxially to the electron beam axis and made of a good material Thermal conductivity, for example made of copper. Within this cup-shaped metal part, an electron beam usually tends to spread out on all sides, so that the majority of the electrons impinge on the side wall surface of the collecting electrode.

In the case of collecting electrodes of the known type described May the heat generated by the impact of the beam electrons on the collector wall, do not exceed a certain value if inadmissibly high temperature peaks should be avoided. The local heating of the collector depends on the power density the electrons with which the inner wall of the collecting electrode is applied. If the rotationally symmetrical Catcher has an axially parallel inner wall according to the most common constructions, is subject to a steadily expanding

909821/0415 ~. ³ ~

H9U65

PA 9/492/499 «. 3 -

Electron beam is the power density on the collector wall at the point of impact of the electron beam edge largest and then decreases towards the collector floor, while it is back on the actual collector floor can assume greater values. The power density deo electron impact is in this case about the Unevenly distributed length of the collecting electrode. This requires that to avoid local overheating the collector must be larger than necessary to absorb the total power of the electron beam were.

There are also cathode ray tubes with a rotationally symmetrical one formed collecting electrode known, the inner diameter in the electron entry direction becomes steadily or stepwise smaller. Such a collecting electrode may be more evenly loaded with beam power towards the collector floor than a collector with a cylindrical inner circumference, if one assumes a constantly rising electron beam. It remains however, an uneven distribution of the power density, especially in the front part of the collecting electrode can ground inadmissibly high. ·,

Furthermore, it is known that the XinneiirauS of the collecting electrode of a traveling wave tube in fiichtung on the delay

909821/0416

U9U65

ΡΛ 9/492/499 - 4 -

taper conically in order to prevent secondary electrons or reflected electrons from escaping to complicate the collecting electrode. In this case it can be near the edge of the electron beam, provided if it hits the conical part, the strain on the collector is lower than with a collector electrode with axially parallel inner wall. However, it is by no means obtained in the rear part of the collecting electrode a uniform power density on the collector wall arriving electrons.

The invention is based on the object of creating a collecting electrode for cathode ray tubes which guided the electron beam to be recorded Power is largely evenly distributed over the collector wall. To solve this problem, a cathode ray tube of the type mentioned according to the invention proposed that the surface lines of the interior of the collecting electrode approximates the differential equation

follow, where N is the constant-toroidal power guided by the electron beam when it enters the collecting electrode; ⁿ _to i die on; the inner wall of the collecting

909821/0415 - 5 -

H9H65

PA 9/492/499 - 5 -

electrode permissible power density "during electron impact and ζ is a coordinate in the longitudinal direction of the collecting electrode, while r_ is the respective inner radius of the

el

Collecting electrode as well as ei the respective angle between the inner wall of the collecting electrode and the Strahlachoe ■ means and r. as a puncture of ζ the respective beam radius with the consideration as if the edge of the electron beam would spread open unhindered even after hitting the collecting electrode M ^{, and S 4} V indicates the associated angle between the edge of the beam and the beam axis.

In the determination equation proposed according to the invention for the longitudinal section contour of the inner wall of the collector, N as the direct current power of the electron beam "when entering the collector and n _to n as the maximum power density permitted on the collector wall are constant values that are derived from the structure and operating data of a relevant tube The functions r, (z) and ^ vCz), which characterize the electron beam path, can be determined experimentally or by calculation for each specific tube arrangement. The desired surface line for the interior of a collecting electrode can then be found by graphical approximation or with an analog computer whose inner diameter changes depending on the z-axis.

909821 / OA15 " ⁶ "

H9U65

PA 9/492/499 - 6 -

ensures that the power carried by the electron beam is practically completely uniform on the inner wall of the catcher is distributed. The3 means an elimination of local power peaks on the collector wall during electron acceptance, so that the Collecting electrode compared to the well-known cup-shaped Electron beam catchers can be spatially smaller.

When constructing the collecting electrode of a cathode ray tube according to the invention, the best of these is used assumed that in the middle area of the interior of the collector at the location of a small axially parallel wall zone (α = 0) there is a maximum inner radius. The choice of this maximum inner radius depends on the structure of the Collecting electrode and the total power carried by the electron beam, giving the relationship

^r ao = r _h . N ₀ ⁽ V

Fulfills. In this relation ζ indicates the abscissa, at which the edge of the electron beam hits the wall surface with α - ο.

The (respective inner radius of the collecting electrode is appropriate in front of the point at which the edge of the jet strikes, selected slightly larger than the calculated beam radius. Of the

909821/0415 ~ ⁷

H9H65

VA 9/492/499 - 7 -

The advantage of this measure is that there is sufficient free space for possible deviations in the beam path of its nominal value, which can be based, for example, on variations in the electron injection, is present.

The invention will be explained in more detail below with reference to the figures of the drawing.

FIG. 1 shows the construction principle of the collecting electrode of a time-of-flight tube according to the invention. Included 1 denotes a cup-shaped collecting electrode shown in longitudinal section, which has a rotationally symmetrical has trained Innenraura with a changing diameter. In this collecting electrode, which can for example consist of copper and be part of the discharge vessel of a cathode ray tube should, an electron beam 2 enters, which within the collecting electrode according to the beam edge curve 3 continuously strives to spread. Provided, that the electron beam 2 is no longer decelerated within the collecting electrode 1, the power density ira beam cross-section is essentially constant and the individual electron trajectories are similar, The formula applies to the power density of the collecting electrode 1

909821/0415

H9H65

PA 9/492/499 - 8 -

This formula is approximately simplified to

N ₀ / r _a
n (z)? s -j-. ί ~ -. % -

^r b \ ^b

where the approximation is so good that "up to (P, - a ) ^ 30 ° with P ₁₃ ^ 15 ° the error remains smaller than 2 #, (in the given relation iot N is the equilibrium power of the electron beam in the collecting electrode , while all other quantities are functions of the coordinate ζ in the longitudinal direction of the collecting electrode, namely: n (z) the power density on the collecting wall, r, (z) the beam radius or - after the beam edge hits the collecting wall - the calculated value for this ; Γ ^ ίζ) the angle which the edge of the jet forms with the axis of the jet; r the inner radius of the collector

ti

and it is the angle that the inner wall of the Aufflinger with the abscissa includes ζ.) From this approximation for the power density n (z) it can be deduced that a uniform power density η is achieved on the inner wall of the collecting electrode if according to the invention the surface lines of the interior of the collecting electrode of the differential equation

909821/0415 "9 -

149H65

ΡΛ 9/492/499 - 9 -

dz = a ^A * r _b *> - b

follow. This differential equation can easily be solved by the fact that every electron collector with any contour deo interior has to have a zone, however narrow, in which the collector wall can be axially parallel and at this point - with a suitable choice of the radius - the permissible power density is not The abscissa ζ in Figure 1, at which this can be the case, results from the specified differential equation rait a - ο as:

Here r__ indicates a maximum collector radius, the Y / ahl of which depends on the power N and the overall construction (collector material, cooling, etc.). You can now divide the rear part of the catcher into even strips Zq, Z ₁ , z _{2 etc.} From 2 _Q , a starting rod c with the angle ti = ο is drawn to Z _1. For Z ₁ , the value u ₁ can then be obtained according to the formula

be calculated. This principle can be continued according to the known tangent train method. For the

909821/0416

U9U65

PA 9/492/499 - 10 -

Averaging the collector contour in front of the point ζ, it should be noted that in general on the abscissa ζ the inner radius of the collector electrode 1 does not coincide with the beam radius r-. will coincide, but already lies within the beam boundary. For values z <z there would therefore be the risk that the permissible power density at the edge of the beam would be exceeded. In the case of a graphical solution of the differential equation proposed according to the invention, it is therefore advisable to start with a chord towards the collector inlet and to continue calculating according to the chord pulling method. In most cases, however, it is sufficient to measure the wall slope ei with ^r r, = ^r v> directly at the edge of the beam according to the relationship

ei D "

"O

to be calculated as a function of ζ. The individual calculation values for the wall slope α along the edge of the beam result in a 2one from the directional field of the wall. The contour is expediently constructed in such a way that it both coincides with the directional field and, on the other hand, leaves a sufficiently clear space free for the target value of the beam edge in order to be able to take into account possible variations in the beam inclusion.

The following is a practical example for the collecting electrode of a wall according to the invention

909821/0415 - 11 -

U9U65

PA 9/492/499 - 11 -

derfeldröhrc described. This is based on a DC power loss H of 4.1 kW, while the construction of the tube should result in a maximum inner radius of r _Λ - 1.7 cn. Because of

HO

a known magnetic field course within the collecting electrode, which is partially magnetically shielded by a screening cylinder made of soft magnetic material in a manner known to me, the beam course r, (z) and ^ (z) was determined with an analog computer as shown in FIG shows. The distance ζ is indicated in centimeters on the abscissa and measured from the cathode surface of a corresponding traveling field tube, while the ordinate shows the beam radius r in centimeters or the angle of the beam radius £ * in degrees. In Figure 2, the course of r ^, ** / ^r b ¹ ^ ¹ ** ^ t / ^r b ^over ^ ^he abscissa ζ is plotted. With a permissible power density of η »= 100 W / cm and the specified values I for r and N, according to the above relationship, a = ο becomes the expression

^r b

found. The value ζ = 74.7 cm can then be taken from FIG. By dividing the rear part of the catcher into strips of z ^ = 75, 76, 77, 78 ... cm

909821/0415

U9U65

PA 9/492/499 - 12 -

the following table results with the approach explained with reference to FIG. 1:

ζ : 75; 76; 77; 78; 79; 80; (cm) r _a : 1.7; 1.65; 1.45; 1.15; 0.83; 0.45; (cm) ^: -3.5; -10; -14.4; -16.8; -1.8.9; -22.1; (Degree)

This results in a tangent line which can be grounded in a simplified manner in the practical construction. In the front part of the collector v / individual values for α are grounded along the edge of the beam r. calculated with the following results:

ζ = 70; 71; 72; 73; ' 74 (cm) « _r = 8.5; 7.4; 5.7; 6.5; 4.8 (degrees)

The direction tangents corresponding to the values for et are shown in FIG. 3 along the course of the beam edge, which corresponds to the curve r in FIG. Starting from ζ, a catcher contour corresponding to the dashed line 6 was then selected in the area z <z, which both coincides with the incline of the directional tangents 5 and leaves free space for variations in the beam path. After the value ζ , the tangent train determined above is first of all continuous

909821/0415 " ¹³ "

U9U65

PA 9/492/499 '- 13 -

Line 7 applied. On the other hand, there is the actually executed catcher contour, which is also used for the values z <z is indicated as dashed line 6, something simplified. The circular enlargement on the collecting base takes into account the fact that an ideal Tip is not possible and therefore at the bottom of the catcher resulting heat is advantageously dissipated evenly on several sides. In Figure 3 is € 8 still indicated a soft magnetic shielding cover. This shield is provided to protect the interior of the Auffänger against a magnetic Pührungsfeld, the usual for the bundled guidance of the electron beam a traveling wave tube is required to shield at least partially magnetically, so that a Spreading of the beam within the collecting electrodes is possible due to the space charge forces.

4 claims
3 figures

909821/0416

Claims (4)

I may not ferment:, i -.-. I fafc & i PA 9/492/499 -H ^ - claims 1. Cathode ray tube, in particular traveling wave tube of high power, with a cup-shaped collecting electrode which receives the electron beam and which is coaxial is arranged to the beam axis and has a rotationally symmetrical interior, v / elcher has a changing inside diameter and in which the electron beam is steadily concentric spreads to the beam axis, characterized in that the surface lines of the interior of the collecting electrode approximates the differential equation dz * ⁴ ^ * '* r _b ^K " ^{J A} b ^' N _Q follow, where N is that guided by the electron beam when it enters the collecting electrode .; DC power, η, the permissible power density on the inner wall of the collecting electrode during electron impact and ζ is a coordinate in · the longitudinal direction of the collecting electrode, while r_ is the respective Inner radius of the collecting electrode and α the respective Angle between the inner wall of the collecting electrode and the beam axis means and r ^ as puncture of ζ the respective beam radius with the consideration whether the edge of the electron beam also after 909821/0415 - 15 - U9U65 ΡΛ 9/492/499 - 15 - Impact on the collecting electrode would spread open unhindered, and f, the associated angle between the edge of the jet and the axis of the jet. 2. Cathode ray tube according to claim 1, characterized in that the collecting electrode is in its middle Area at a point ζ has a maximum Innenradiu3 r, which is equal to zero with ö relationship ao ~ FvTlL Fulfills. 3. Cathode ray tube according to claim 2, characterized in that that the inner radius of the collecting electrode in front of the point ζ is chosen so large that a light Space remains between the nominal value of the beam edge r - ^ (z) and the inner wall of the collecting electrode. 4. Cathode ray tube according to one of claims 1 to 3 »characterized in that the collecting electrode is magnetic is shielded. 909821/0415