US3489894A - High power chamber - Google Patents

Description

Jan. 13, 1970 R. D. CRAM HIGHTPOWER CHAMBER Filed July 21, 1966 INVENTOR ROBERTD RAM f j ATTORNEY United States Patent US. Cl. 250-41.9 3 Claims ABSTRACT OF THE DISCLOSURE A high power beam deflection chamber having vacuum tight walls of a low thermal conductivity material lined with a high thermal conductivity material which prevents localized heating and burn through of the low thermal conductivity walls when an intense particle beam is impinged on the walls.

This invention relates generally to high power beam deflection systems and more particularly to a chamber designed for handling deflected high power particle beams.

Deflection of charged particles and chambers for handling such charged particle beams are old and well known in the art. Such chambers are typically made of easily fabricated materials such as stainless steel which can be assembled into a vacuum chamber with ease.

The drawback with materials, such as stainless steel, is that they have a low thermal conductivity and if for some reason during the handling of the charged particle beam, the deflection is insufficient or overly sufficient the beam may strike the chamber wall and penetrate therethrough causing either a vacuum leak or a water leak for a water cooling chamber is affixed to portions of the exterior wall of the chamber.

Attempts have been made to design such chambers of high thermal conductivity material such as copper. However, such materials cannot be readily fabricated into chambers capable of maintaining high vacuums within the chamber.

To overcome these difficulties the present invention was devised and results in a chamber which absorbs the impact of the beam and dissipates its effect such that leaks are not realized.

Broadly speaking the present invention accomplishes this by fabricating the chamber from low thermal conductivity material which can easily be made vacuum tight and lining portions of the chamber with a high thermal conductivity material which prevents localized heating of the low thermal conductivity material which comprises the chamber wall.

The invention, features and embodiments thereof may be more fully appreciated by perusal of the following specification taken in conjunction with the drawings wherein FIGURE 1 shows an overall broken away view of a beam deflection chamber in which the present invention is used.

FIGURE 2 shows a sectional view of the chamber taken along the line 22 and FIGURE 3 shows an enlarged view of a typical corner of the chamber.

With reference now to FIGURE 1 in which there is shown a top sectional view of a typical beam deflection chamber, chamber 10, having an entrance port 11 and a multiplicity of exit ports 12, 13, 14, 15 and 16 which are arranged at varying angles with respect to the entrance port 11. A beam 17 passing along the center line of the entrance port 11 may be deflected through variousangles and out different exit ports by means of magnetic field techniques know to those skilled in the art. The amount of deflection, of course, is directly related to the strength of the field, the energy of the beam particles comprising the beam and their electric charge. When such beams comprise particles of varying energies charges or velocities the particles follow different paths when subjected to the same field. Thus for example the main portion of the beam 17 may be made to exit along the center line of exit 12 but a portion 18 of the beam may be deflected insufliciently to pass through either exit 12 or exit 13 and instead strike the chamber wall 19 at the V lying between the exit ports 12 and 13. In the prior art when this happened the beam, if of suflicient intensity and permitted to remain on a localized spot for a sufficient period of time, would burn through the wall totally disrupting the vacuum. When the vacuum is so disrupted it is necessary that the equipment be shut down and the chamber repaired. In the prior art the chamber walls were normally made of a low thermal conductivity material such as stainless steel whose heat capacity is one to two thousand watts per square centimeter. Since the beams normally passing through the chamber are 5000 watts or more it is easy to see that burn through of the stainless steel wall could occur in a very short period of time.

The present invention solved this problem encountered in the prior art by brazing onto selected portions of the chamber a strip 20 of high thermal conductivity material. Typically this is quarter inch thick copper strip 4 of an inch in width. This copper strip 20 is brazed to the chamber sidewalls 21 and 22 prior to fabrication of the chamber by the addition of a top plate 23 and a bottom plate 24. Normally the stainless steel material used in the construction of this chamber is so-called 304 stainless steel. The copper strip 20 was brazed to the respective side walls 21 and 22 by using a silver braze. It has been found that if a small fillet of brazing material is permitted to form at each side of the union between the strip 20 and the walls 21 and 22 without pin holes that good thermal conductivity and brazing has occurred between the walls and the strip 20.

Once the strip 20 has been brazed to the walls a top plate 23 and a bottom plate 24 which are then welded to the sidewalls 21 and 22 so as to form one continuous enclosed chamber 10 the top plates 23 and 24 are prefabricated to form the desired shape and the sidewalls 21 and 22 bent to the required angles.

During welding of the top and bottom plates to the sidewalls it is necessary that this welding be carefully done in order to prevent the change in permeability of the stainless steel being fabricated. As is well known when stainless steel of this type is welded a change in permeability could occur and such a change in permeability could cause a permutation of the magnetic field which would result in the beam being deflected in an improper manner. To avoid such a change in permeability it has been determined that chamfering of the corners of the sidewalls 21 and 22 and the top and bottom plates 23 and 24 at an angle of 45 as shown in FIGURE 3, coupled with use of a 310 stainless steel welding rod for the weldment that this change in permeability is minimized if not eliminated.

Once the main portion of the chamber has been welded together and vacuum tested cooling channels 29 are provided on each of the sidewalls 21 and 22 of the chamber. These cooling channels are formed from U shaped stainless steel channels and either welded or soft soldered to the sidewalls. These channels are then fitted with water intake and outlet nozzles 30 and 31 and with suitable conduits 32 across each of the exit ports.

A chamber built in the manner described has not burned through even when a beam having a 10,000 watts per square centimeter density was permitted to impinge on the sidewalls for a period of over one minute. In normal use beam powers of such magnitude are relatively rare except during initial test. In chambers, not utilizing the invention, it was found that beam powers of one to two thousand watts per square centimeter would readily burn through causing vacuum and/ or water leaks.

The tests have indicated that the described construction of the wall can withstand 35 to 40,000 watts per square centimeter.

Having now described one preferred embodiment of the present invention it is desired that the examples given herein be only by the way of illustration and not by way of limitation and that the invention be limited only by the appended claims.

What is claimed is:

1. A beam deflection chamber comprising a top plate, a bottom plate, sidewalls for maintaining said plates in spaced relationship, said sidewalls being interrupted to define an entrance port and an exit port, said plates and sidewalls being of a low conductivity material, cooling 20 means affixed to the exterior of said sidewalls, and a body of high conductivity material disposed contiguous to and in intimate contact with the interior of said walls.

2. The chamber of claim 1 wherein said walls are welded to said plates to hold said plates in said spaced relationship, said walls and said plates having their edges chamfered at an angle of 45 whereby said weldment does not adversely affect the permeability of said Walls and said plates.

3. The chamber of claim 1 wherein said body of high conductivity material comprises a copper strip and said low conductivity material comprises stainless steel.

References Cited UNITED STATES PATENTS 2,065,660 12/1936 Dallenbach 3l3- -l2 2,566,037 8/1951 Shewell 25041.9 3,187,237 6/1965 Craig et al. 335301 3,197,678 7/1965 Primas 25041.9

RALPH G. NILSON, Primary Examiner S. C. SHEAR, Assistant Examiner

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