Process and apparatus for treating inner surface treatment of chamber and vacuum chamber

A rod driver is used to drive a rod so as to move a broach through a continuous vacuum chamber in the axial direction. The broach is provided at the leading end of the rod with cutting and finishing edges at a plurality of stages in the axial direction. The cutting edges each have chip breakers in their outer periphery. The broach is moved in the vacuum chamber to cut the inner surface of the vacuum chamber, so that a new surface is formed. During the cutting at least one of an inert gas, nitrogen, and a mixture of the inert gas and nitrogen is supplied to the cutting edges. The outer diameter of the finishing edge is same as the desired inner diameter of the vacuum chamber and the finishing edges are effective in forming such a vacuum chamber with greater precision and the least friction. As a contaminated and decomposed layer on the inner surface of the vacuum chamber is removed in the axial direction of the inner surface of the vacuum chamber for certain, moreover, gas desorption, from a new surface, originating from thermal desorption and photodesorption generated at the time of synchrotron radiation can be minimized to satisfy a requirement for a vacuum vessel.

BACKGROUND OF THE INVENTION 
The present invention relates to a process and apparatus for treating the 
inner surface of a vacuum chamber, and more particularly to a process for 
treating the inner surface of a vacuum chamber for use as a vacuum vessel 
such as a vacuum chamber in a charged particle accelerator to reduce gas 
desorption from the inner surface of the vacuum chamber produced by at 
least either thermal desorption or photodesorption. 
In order to accelerate charged particles with high energy in a charged 
particle accelerator, it is necessary to prevent charged particles from 
scattering because of a collision of charged particles with residual 
gases, that is, to prevent the loss of such charged particles. The 
environment in which the charged particles are accelerated should be set 
in a ultrahigh vacuum to prevent such a loss. Consequently, a vacuum 
vessel such as a ultra--clean vacuum chamber and the like is employed in 
the charged particle accelerator to actually attain a high or ultrahigh 
vacuum environment. Moreover, the most important task is to reduce the gas 
desorption from the vacuum vessel itself in addition to increasing the 
pumping speed of a vacuum pump to achieve a high or ultrahigh vacuum. 
In this case, aluminum alloy, stainless steel, copper or the like is 
normally used for the vacuum vessel, called a vacuum chamber, of the 
charged particle accelerator. A factor governing gas desorption from the 
vacuum vessel using such a metal is thermal desorption in which absorbed 
molecules on the inner surface of the vacuum chamber are caused to be 
desorbed by thermal energy. 
However, what greatly affects the pressure in the charged particle 
accelerator other than the normal thermal desorption originates from the 
presence of high-energy particles in the vacuum vessel. For example, 
electrons and positrons whose orbits have been altered by a bending magnet 
or the like in a electron storage ring generate electromagnetic waves 
called synchrotron radiation due to radiation. The inner wall of the 
vacuum chamber is irradiated with the synchrotron radiation, which causes 
gas desorption called photodesorption from the inner surface of the vacuum 
chamber. 
With respect to photodesorption, a description has been given in "Vacuum" 
(volume 33, number 7 (1983) pp. 397-406). The gas desorption caused by the 
photodesorption raises the pressure in the vacuum chamber and results in 
introducing the scattering and attenuation of stored electrons. 
In order to reduce gas desorption as much as possible, there have been 
proposed various methods of treating the inner surfaces of vacuum chambers 
for the purpose of not only cleaning the inner surfaces of vacuum chambers 
but also removing chemical compounds and contaminants causing such gas 
desorption. Chemical treatments using acid cleaning, alkali etching and 
the like are most common by used methods of treating the inner surfaces of 
vacuum chambers. Chemical treatments of the sort mentioned above have also 
been referred to in "Vacuum" (volume 38, number 8-10 (1988) pp. 933-936). 
In addition to chemical treatments, there is a discharge cleaning method in 
which the inner surface of a vacuum vessel is bombarded with the ions 
generated by electric discharge. Moreover, another one known as a 
pre-baking treatment method comprises the steps of heating a vacuum 
chamber at high temperatures in a vacuum furnace to remove compounds on 
the inner surface of the vacuum chamber by evaporating them, and removing 
the gas contained in the material of the vacuum chamber by diffusing the 
gas so as to discharge the gas from the material. In this way, attempts 
have been made to reduce gas desorption from the inner surface of the 
vacuum chamber by cleaning the inner surface thereof. 
In the aforementioned prior art, a lubricant may be used to reduce the 
friction between the material of a vacuum chamber and a plug or the like 
when a billet is formed by extrusion into a vacuum vessel such as the 
vacuum chamber of a charged particle accelerator. In this case, it is 
feared that a contaminated layer is formed on the inner surface of the 
vacuum chamber because of the lubricant. Thermal desorption or 
photodesorption may thus cause gas desorption from the contaminated layer. 
When a vacuum chamber is formed by hot extrusion, moreover, a contaminated 
layer as a source of gas desorption may be formed as air and impurities 
react on the inner surface of the high-temperature vacuum chamber. In a 
case where a vacuum vessel is manufactured by roll-forming out of a rolled 
sheet, moreover, there also arises problems that such a contaminated layer 
is formed during the step of producing the sheet material by rolling. 
In order to reduce gas desorption from the contaminated layer due to 
thermal desorption or photodesorption, the process of chemically treating 
the inner surface of the vacuum chamber needs changing depending on the 
material used when the inner surface is subjected to the chemical 
treatment. Nevertheless, there still arise problems that since chemicals 
are used, the inner surface of the vacuum chamber tends to become coarse 
in exchange for removal of the gas desorption layer, that the scale of 
facilities necessary for the inner surface treatment tends to become 
larger since those for rinsing the chemicals used for processing purposes 
and preventing environmental pollution are required, and that a compound 
layer as a source of gas desorption is newly formed on the inner surface. 
In the case of the discharge cleaning utilizing ion bombardment, on the 
other hand, the gas itself used for discharge is allowed to penetrate into 
the vacuum chamber material and the problem is that the material itself 
has to be removed by sputtering. Further, the high-temperature heat 
treatment called pre-baking may incur a reduction in material strength 
since the vacuum chamber material passed through the heat treatment in the 
vacuum furnace becomes softened. Particularly, aluminum alloy, for 
example, is not fit for the pre-baking treatment in view of material 
strength as it may melt down. In addition, no consideration has been given 
to energy saving notwithstanding the use of such an energy-consuming 
vacuum furnace. 
Incidentally, the vacuum chamber as an object for patent herein is 
generally as long as several meters and hardly fitted in a processing 
apparatus after it undergoes so-called machining such as boring. In other 
words, it has been difficult to treat the inner surface of such a vacuum 
chamber. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a process for treating the 
inner surface of a vacuum chamber to ensure that a contaminated or 
decomposed layer as a source of gas desorption on the inner surface of a 
vacuum chamber such as a continuous vacuum chamber of which inner surface 
is difficult to be machined or bored. 
Another object of the present invention is to provide an apparatus for 
treating the inner surface of a vacuum chamber to ensure that a 
contaminated or decomposed layer as a source of gas desorption on the 
inner surface of a vacuum chamber such as a continuous vacuum chamber of 
which inner surface is difficult to be machined or bored. 
Still another object of the present invention is to provide a vacuum 
chamber so designed as to reduce gas desorption due to thermal desorption 
or photodesorption originating from a contaminated layer by applying the 
aforementioned process of treating the inner surface and to attain a high 
or ultrahigh vacuum environment when used as a vacuum vessel. 
A further object of the present invention is to provide a vacuum chamber 
with a plurality of vacuum chambers coupled together for a charged 
particle accelerator. 
In a first embodiment of the present invention made to accomplish the 
object above, a broach having at least one cutting edge which is in 
contact with the inner surface of a vacuum chamber and has cutouts in its 
outer periphery is used to cut off a contaminated layer on the inner 
surface of the vacuum chamber while the broach and the vacuum chamber are 
unidirectionally moved relatively to each other in the axial direction. 
Preferably, the contaminated layer on the inner surface of the vacuum 
chamber is cut off while at least either inert gas or a mixture of 
nitrogen and inert gases is being supplied to the cutting surface of the 
vacuum chamber being treated by the broach. 
Further, the contaminated layer on the inner surface of the vacuum chamber 
is preferably cut off while a solvent for the contaminants contained in 
the contaminated layer is being supplied to the surface of the vacuum 
chamber being cut by the broach. 
Still further, the contaminated layer on the inner surface of the vacuum 
chamber is preferably cut off while at least either inert gas or a mixture 
of nitrogen and inert gases is being supplied to the cutting surface of 
the vacuum chamber and while a solvent for the contaminants contained in 
the contaminated layer is being supplied to the surface of the vacuum 
chamber being cut by the broach. 
In a second embodiment of the present invention, a process for treating the 
inner surface of a vacuum chamber wherein a broach having a plurality of 
cutting edges each having cutouts in their outer peripheries is used to 
cut off a contaminated layer on the inner surface of the vacuum chamber by 
unidirectionally moving the broach and the vacuum chamber relatively to 
each other in the axial direction and wherein finishing edges, as an 
integral part of the broach, having the same external diameter as that of 
the final-stage cutting edge in the axial direction are used to finish the 
inner surface of the vacuum chamber with predetermined precision. 
A third embodiment of the present invention comprises a support, means for 
anchoring a vacuum chamber to the support and holding the vacuum chamber, 
a broach having at least one cutting edge which is in contact with the 
inner surface of the vacuum chamber and has cutouts in its outer 
periphery, and broach drive means to which the broach arranged on the 
support is fitted. The broach drive means unidirectionally moves the 
broach relatively to the vacuum chamber in the axial direction to cut off 
a contaminated layer on the inner surface of the vacuum chamber. 
A fourth embodiment of the present invention comprises a support, a broach 
having at least one cutting edge having cutouts in its outer periphery and 
an outer peripheral configuration, excluding the cutouts, substantially 
similar to the inner peripheral configuration of a vacuum chamber as an 
object to be treated, means for anchoring the broach to the fitting 
support, and vacuum chamber drive means for holding the vacuum chamber and 
unidirectionally moving the vacuum chamber relatively to the broach in the 
axial direction to cut off a contaminated layer on the inner surface of 
the vacuum chamber. 
A fifth embodiment of the present invention comprises a support, means for 
anchoring a vacuum chamber to the support and holding the vacuum chamber, 
a broach having a plurality of cutting edges having cutouts, and broach 
drive means to which the broach arranged on the support is fitted. The 
broach drive means unidirectionally moves the broach relatively to the 
vacuum chamber in the axial direction to cut off a contaminated layer on 
the inner surface of the vacuum chamber. The outer diameter of each 
cutting edge, excluding the cutouts, is set greater than that of the 
immediately preceding one in the direction of the rearmost edge face from 
the front edge face. 
Preferably, at least one cutout is provided in the circumferential 
direction of each cutting edge and cut through the cutting edge in the 
axial direction of the broach, and the cutouts of the adjoining cutting 
edges are mutually located at different circumferential positions. 
Further, the broach is preferably provided with finishing edges having the 
same contour and dimension excluding the final-stage cutting edge and its 
cutouts. The finishing edges are used to finish the inner surface of the 
vacuum chamber with predetermined precision. 
Still further, the broach is preferably provided, between the adjoining 
cutting edges and between the finishing edges, with a chip storage space 
large enough to accommodate chips of the contaminated layer and hold them 
until the broach slips out of the rear end of the vacuum chamber. 
Still further, there may be arranged a liner for putting the height of the 
vacuum chamber and the cutting edge of the broach in correct alignment on 
at least one side of the vacuum chamber where the broach is fitted in. 
Still further, there may be arranged a front guide on at least one side of 
the vacuum chamber where the broach is fitted in. 
Still further, there may be provided means for supplying either inert gas 
or a mixture of nitrogen and inert gases, or lower alcohol to the surface 
of the vacuum chamber being cut by the broach. In this case, the means for 
supplying the fluid to the cut surface may include a main fluid channel 
formed in the axial direction of the broach shaft of the broach and jet 
channels radially extending from the main fluid channel. 
Another embodiment of the present invention includes providing a vacuum 
chamber whose contaminated layer on the inner surface thereof has been cut 
of through the process of treating the inner surface of the vacuum chamber 
or a vacuum chamber whose contaminated layer on the inner surface thereof 
has been cut off by an apparatus for treating the inner surface of the 
vacuum chamber. 
In still another embodiment of the present invention, flanges each provided 
on both sides of the vacuum chamber are fitted with second flanges that 
can be coupled to the former flanges, respectively, to form a vacuum 
vessel and there are provided means for evacuating inside the space formed 
in the vacuum vessel, and also means for accelerating charged particles 
existing in the internal space of the vacuum vessel thus evacuated. 
Even though such a contaminated layer originating from a lubricant and the 
like is formed at the time of extrusion forming, the broach having at 
least one cutting edge in the axial direction or what is similar in 
contour to the vacuum chamber is used according to the present invention 
to cut off the contaminated layer on the inner surface of the vacuum 
chamber by moving the broach relatively to the vacuum chamber in the axial 
direction to ensure that the contaminated layer is removed. Consequently, 
the release, from the inner surface of the vacuum chamber, of gas stored 
in the contaminated layer due to thermal desorption or photodesorption is 
greatly reduced. 
By supplying at least either inert gas as a single substance or the mixture 
of nitrogen and inert gases to the surface of the vacuum chamber to be cut 
by the broach or otherwise supplying lower alcohol as a solvent for the 
contaminants contained in the contaminated layer to the surface of the 
vacuum chamber to be cut thereby, the contaminated layer on the inner 
surface of the vacuum chamber is scraped off, so that the effect of 
reducing gas desorption is increased with efficiency. In this case, the 
use of finishing edges having substantially the same contour and dimension 
as those of the final-stage cutting edge makes it possible to increase 
precision on the inner surface of the vacuum chamber. 
In order to move the broach relatively to the vacuum chamber, there are two 
methods that can be employed: one for moving the vacuum chamber while the 
broach is fixed and another for moving the broach while the vacuum chamber 
is fixed. In the case of the former, an apparatus for treating the inner 
surface of a vacuum chamber comprises a support, means for anchoring the 
vacuum chamber to the support, a broach having at least one cutting edge 
whose contour is substantially similar to the inner contour of the vacuum 
chamber, and broach drive means for moving the broach in the axial 
direction of the vacuum chamber to cut off the contaminated layer on the 
inner surface of the vacuum chamber. Whereas in the case of the latter, an 
apparatus for treating the inner surface of a vacuum chamber comprises a 
support, means for anchoring to the support a broach having at least one 
cutting edge whose contour is substantially similar to the inner contour 
of the vacuum chamber, and vacuum chamber drive means for moving the 
vacuum chamber in the axial direction of the vacuum chamber to cut off the 
contaminated layer on the inner surface of the vacuum chamber. 
In a case where the broach has the plurality of cutting edges in any one of 
the apparatus for treating the inner surface of a vacuum chamber, cutting 
will be carried out smoothly if the outer diameter of each cutting edge 
ranging from the front stage to the final stage of the broach is set 
greater than that of the immediately preceding one. In the case of the 
broach having the plurality of cutting edges, chips will be preventing 
from growing longer and from being caught by the cutting edge coming up 
from the rear, provided at least one cutout (chip breaker) is made in the 
circumferential direction of each cutting edge in such a manner that the 
cutouts of the lengthwise adjoining cutting edges are not overlapped in 
the circumferential direction. 
Moreover, the provision of a plurality of finishing edges for finishing the 
inner surface of the vacuum chamber with predetermined precision, the 
finishing edge being substantially similar in contour and dimension to the 
final-stage cutting edge, makes available an inner surface offering 
desired smoothness. Since a sufficiently-large chip storage space is 
formed between the lengthwise adjoining cutting edges and between the 
finishing edges, chips are prevented from being caught by the cutting edge 
coming up from the rear. The use of the liner for putting the inner 
surface of the vacuum chamber and the cutting edge of the broach in 
correct alignment on either one side of the vacuum chamber where the 
broach is fitted in or the other where it is drawn allows the cutting edge 
to be smoothly driven at the front and rear ends of the vacuum chamber. 
The provision of the front guide on one side of the vacuum chamber where 
the broach is fitted in and a rear guide on the other side behind the 
finishing edge also allows the broach to be smoothly fitted in and drawn. 
Even though such a contaminated layer originating from a lubricant and the 
like is formed at the time of extrusion forming, the broach is used 
according to the present invention to cut off the contaminated layer on 
the inner surface of the vacuum chamber to ensure that the contaminated 
layer is removed. Consequently, the release, from the inner surface of the 
vacuum chamber, of gas stored in the contaminated layer due to thermal 
desorption or photodesorption is considerably reduced. It can also be 
dispensed with to subject the inner surface to chemical treatment, which 
makes unnecessary any facility for use in applying chemical treatment, 
rinsing chemicals after treatment, preventing environmental pollution or 
the like. In addition, there is no possibility that the inner surface of 
the vacuum chamber is damaged by the chemical treatment. Basically, it is 
improbable for a compound layer as a source of gas desorption to be newly 
generated when such a chemical treatment is applied to the inner surface 
of the vacuum chamber. 
As discharge cleaning utilizing ion bombardment is not needed, on the other 
hand, discharged gas is prevented from penetrating into the vacuum 
chamber, and vacuum chamber material is also prevented from being 
sputtered during the discharge cleaning process. As no high-temperature 
heat treatment for pre-baking is required, not only the softening of the 
vacuum chamber material resulting from such high-temperature heat 
treatment in a vacuum furnace but also a reduction in the strength of the 
vacuum chamber material is prevented. Moreover, an energy-consuming vacuum 
furnace can also be dispensed with and this will contributes to energy 
saving. 
In other words, the process and apparatus for treating the inner surface of 
a vacuum chamber according to the present invention can be employed for 
obtaining a vacuum chamber in which the gas desorption caused by thermal 
desorption and photodesorption originating from synchrotron radiation has 
been reduced.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to the drawings, a description will be given of a process and 
apparatus for treating the inner surface of a vacuum chamber and a vacuum 
chamber. 
FIG. 1 is an elevational view of an apparatus for treating the inner 
surface of a vacuum chamber according to the present invention with a 
schematic illustration of its construction, part of which is shown in 
cross section. An apparatus 30 for treating the inner surface of a vacuum 
chamber embodying the present invention comprises a broach 10 having a 
plurality of cutting edges, a rod 32 whose one end is coupled to the 
broach 10 and which is used to move the broach 10, a rod driver 34 for 
giving driving force to the rod at one end opposite to the other where the 
rod 32 is coupled to the broach 10, a chamber stopper 35 and a vacuum 
chamber anchoring tool 36 for anchoring a vacuum chamber 20 as an object 
to be treated, a liner 37 for putting the vertical positions of the 
cutting edges of the broach 10 and the inner surface of the vacuum chamber 
20 in correct alignment so that the broach 10 may be fitted into and drawn 
from the vacuum chamber 20, and a support 38 for loading the vacuum 
chamber 20 as an object to be treated. The vacuum chamber 20 is used as a 
vacuum vessel or vacuum chamber which accelerates or stores electrons and 
positrons after the inner surface treatment is completed as will be 
described later. 
Referring to FIGS. 1 to 3 inclusive, a procedure for implementing the 
process for treating the inner surface of a vacuum chamber according to 
the present invention will be illustrated. 
FIG. 2 is a diagram illustrating the broach 10 set at the right end of the 
vacuum chamber 20 immediately before the inner surface thereof is treated. 
Before the inner surface treatment, the vacuum chamber 20 is formed so 
that it has a desired contour normally by extrusion or drawing. The vacuum 
chamber is made of stainless steel, aluminum alloy, copper or the like. 
The vacuum chamber 20 having the desired contour is placed on the support 
38 of the apparatus 30 for treating the inner surface of a vacuum chamber 
and anchored on the support 38 by means of the vacuum chamber stopper 35 
and the anchoring tool 36. 
The broach 10 having cutting edges substantially similar in contour to the 
inside of the vacuum chamber 20 is coupled to one end of the rod 32. The 
rod 32 is passed through the vacuum chamber 20 and linearly driven by the 
rod driver 34 in the axial direction, that is, from right to left in the 
drawings. The broach 10 is located on a liner 37a for putting the vertical 
positions of the cutting edges of the broach 10 and the inner surface of 
the vacuum chamber 20 in correct alignment. 
Subsequently, the rod driver 34 is started to linearly drive the rod 32 
toward the left-hand side. In a case where the rod 32 is a ball screw, the 
rod driver 34 is what has a gear for driving the ball screw, a motor and 
the like. Since a linear movement is essential to the rod 32, what is 
capable of hydraulic linear driving may be employed as the rod driver 34. 
When the rod driver 34 is operated, the broach 10 coupled to the rod 32 is 
fitted into the vacuum chamber 20 and moved forward while cutting edges 
formed on the outer periphery of the broach 10 are cutting the inner 
surface of the vacuum chamber 20. At this time, the vacuum chamber 20 
receives counter force accompanying the inner surface cutting and what 
causes the vacuum chamber 20 to move in the direction in which the broach 
10 moves. However, the vacuum chamber stopper 35 resists against the force 
and prevents the vacuum chamber 20 from moving in the same direction. 
Simultaneously, the vacuum chamber anchoring tool 36 prevents the vacuum 
chamber 20 from moving vertically even if the vacuum chamber 20 receives 
force in the vertical direction with respect to the direction in which the 
broach 10 moves forward. 
While cutting the inner surface of the vacuum chamber 20, the broach 10 
moved to the left by the rod 32 moves further forward. FIG. 1 refers to a 
state wherein the broach 10 is inside the vacuum chamber 20 and FIG. 3 to 
what shows the broach 10 outside the vacuum chamber 20 after it has 
completed the operation of cutting the inner surface of the vacuum chamber 
20. 
A liner 37b is arranged on the support 38 so as to put the surface of the 
cutting edge on the broach 10 and the inner surface of the vacuum chamber 
20 in correct alignment when the broach 10 is drawn out of the vacuum 
chamber 20. The broach 10 is drawn in such a manner that it is mounted on 
the liner 37b. 
When the broach 10 is moved like this in the vacuum chamber 20, the inner 
surface of the vacuum chamber 20 is subjected to inner surface treatment 
by cutting. Since the vacuum chamber 20 as an object to be treated is as 
long as several meters, the so-called boring applicable only to small 
parts is not applicable in this case. However, the apparatus for treating 
the inner surface of a vacuum chamber using a broach for cutting makes it 
possible to subject any vacuum chamber to boring that has heretofore been 
difficult to use for cutting the inner surface of any long vacuum chamber. 
The effect of such an inner surface treatment will be described later. 
Referring to FIGS. 4 to 7 inclusive, a description will subsequently be 
given of a broach for use in the apparatus for treating the inner surface 
of a vacuum chamber as shown in FIG. 1. 
FIG. 4 is an elevational view of the broach 10. The broach 10 includes a 
broach shaft 16 as the nucleus and is provided with a front guide 14 as a 
guide for use when it proceeds through the vacuum chamber 20. Cutting 
edges 11a to 11d are formed behind the front guide 14. With respect to the 
plurality of cutting edges 11a to 11d for cutting the inner surface of the 
vacuum chamber 20, their outer diameter slightly decreases in the backward 
direction of the broach 10. Regarding the vacuum chamber 20 which is 
circular in cross section, for example, the diameter of the cutting edge 
11b is greater than that of the cutting edge 11a, and the diameter of the 
cutting edge 11c is grater than that of the cutting edge 11b. 
In an example of the broach 10 shown in FIG. 4, the diameter of the cutting 
edge 11d is greatest and this diameter is made a finishing dimension of 
the inner surface of the vacuum chamber 20. With the dimension of the 
cutting edge 11 like this, the inner surface of the vacuum chamber 20 is 
cut each time the cutting edge 11 of the broach 10 passes through the 
vacuum chamber 20 and the inner diameter of the vacuum chamber 20 is thus 
enlarged. The machining precision of the inner diameter dimension can be 
increased by decreasing the quantity of the cutting carried out by one 
cutting edge 11. Although there are four cutting edges 11 in an example of 
the broach 10 shown in FIG. 4, the number of cutting edges should be 
determined in accordance with the finishing dimension and a margin to be 
cut up. 
Finishing edges 12 are formed behind the final-stage cutting edge 11d. The 
diameter of the finishing edge 12 is the same as that of the final-stage 
cutting edge 11 and the number of finishing edges is determined in 
accordance with the finishing surface precision. In order to reduce 
surface roughness, the number of finishing edges 12 may be increased. 
There are three finishing edges attached in this embodiment of the present 
invention. The shape of the edge also affects the finishing surface 
precision. 
A rear guide 15 is provided behind the finishing edge 12 and together with 
the front guide 14, used to guide the broach 10 when it proceeds in the 
vacuum chamber 20. The rear guide 15 may be omitted, depending on the 
number of finishing edges 12 since the diameter of the rear guide 15 is 
the same as that of the finishing edge 12. 
The cutting edge 11 is provided with cutouts called chip breakers 13. 
FIGS. 5a, 5b are sectional views of broaches 10 with illustrations of chip 
breakers. FIGS. 5a, 5b are those viewed from the direction in which the 
cutting edge 10 is moved. The cutting edges 11 are formed on the outer 
periphery of the broach shaft 16. The adjoining cutting edges 11 are 
illustrated in FIGS. 5a, 5b. In an example of the broach 10 of FIG. 4, 11a 
and 11c represent the cutting edge shown in FIG. 5a, whereas 11b and 11d 
represent what is shown in FIG. 5b. 
As the broach 10 proceeds in the vacuum chamber 20, the cutting edges 11 
cut the inner surface of the vacuum chamber 20 and produce thin chips. As 
the chip continuously grows longer in the circumferential direction of the 
cutting edge 11, it may be caught by the next cutting edge 11 and may 
scratch the inner surface of the vacuum chamber 20, thus badly affecting 
the planing of the surface thereof. 
Since the broach 10 is provided with the chip breakers 13 in this 
embodiment of the invention, the chip is broken at the position of the 
chip breaker 13. The chip breakers 13 thus work to cut the chips in 
lengths lest they continuously grow longer in the circumferential 
direction and the chips are prevented from being caught up by the cutting 
edge 11 coming up from the rear, that is, from badly affecting the 
operation. 
As shown in FIGS. 5a, 5b, different circumferential positions have been 
assigned to the respective chip breakers 13, with a phase 
difference(f1-f2) provided. The chip breakers 13 are cutouts and the 
vacuum chamber is not cut at these positions. When the outer diameter of 
the cutting edge 11 coming up from the rear is greater than that of the 
preceding one, no cutting is carried out at the circumferential position 
corresponding to the chip breaker 13 of the preceding cutting edge 11. 
Then the cutting edge 11 coming up from the rear will have to cut the 
portion left out by the preceding one and the cutting quantity tends to 
increase. In order to prevent the cutting quantity from excessively 
increasing in a specific portion, it is only needed to provide a phase 
difference between the chip breakers by continuously arranging cutting 
edges having the same outer diameter. Consequently, it has been arranged 
in this embodiment of the invention that at least the adjoining cutting 
edges 11 have the chip breakers 13 at different positions, so that the 
portion left uncut by the chip breaker 13 of the preceding cutting edge 11 
is cut by the next one. 
Although 11a and 11c are assumed representative of the cutting edges in 
FIG. 5a, and 11b and 11d representative of those shown in FIG. 5b for 
convenience of illustration in this embodiment of the invention, that is, 
the cutting edges 11a, 11c are set in phase with each other, the cutting 
edges 11a, 11b, 11c and 11d may needless to say be set so that they should 
mutually have an equal phase difference. 
FIG. 6 is a sectional side view of the broach 10 for use in cutting the 
inner surface of the circular vacuum chamber 20 to treat the surface 
thereof. A chip storage space 17 is formed between the vacuum chamber 20 
and the broach shaft 16. Given that the outer diameter of the broach shaft 
16 is d1 and that the inner diameter of the vacuum chamber 20 is d2, the 
height of the chip storage space 17 in the radial direction becomes 
(d2-d1) / 2. 
FIG. 7 is a partial sectional elevational view of broach 10 and the vacuum 
chamber 20 to illustrate the function of the chip storage space 17. The 
broach 10 proceeds to the left in the vacuum chamber 20 to treat the inner 
surface of the vacuum chamber 20. The rod 32 is coupled to the front guide 
14 of the broach 10 and secured to the broach 10 with a nut 31. The chip 
storage space 17 is provided in between the broach shaft 16 and the inner 
surface of the vacuum chamber 20. The chips produced by the cutting edge 
11 are retained in the chip storage space 17 and held between the broach 
10 and the vacuum chamber 20; therefore, the cutting surface is prevented 
from being scratched thereby. 
Referring to FIGS. 8 and 9, the effect of the process of treating the inner 
surface of a vacuum chamber will subsequently be described. 
FIG. 8 is a diagram exemplary illustrating the conditions of the inner 
surface of a vacuum chamber before and after cutting. There exists a 
contaminated and decomposed layer 21 on the inner surface of the vacuum 
chamber 20 as a result of extrusion or drawing carried out to form the 
vacuum chamber at the preceding step before the broach 10 is used for 
cutting purposes. 
When the broach 10 is used to treat the inner surface of the vacuum 
chamber, the contaminated and decomposed layer 21 on the surface thereof 
is removed and a vacuum chamber material 22 appears as the outermost 
layer. Consequently, not only gas desorption from the vacuum chamber due 
to thermal desorption but also photodesorption based on synchrotron 
radiation in an electron storage ring is considerably reduced when the 
vacuum chamber is used. 
FIG. 9 is a graphic representation illustrating results of photodesorption 
tests with synchrotron radiation by way of example. The graph shows the 
results of irradiation of synchrotron radiation generated in the electron 
storage ring on oxygen-free copper subjected to two kinds of inner surface 
treatments. The integrated values of radiation dosage are shown on the 
abscissa axis, the values corresponding to the number of irradiated 
photons after synchrotron radiation is exposed. Whereas yield values are 
shown on the ordinate axis, each indicating the number of photons desorbed 
by one photon, and equivalent to the quantity of gas desorption. If the 
yield value is small, photodesorption from the vacuum vessel will be low 
and the scattering probability of charged particles revolving in the 
vacuum chamber will become lower. Therefore, the life of the charged 
particles is prolonged when the yield value is small and this makes 
available a high-performance vacuum chamber for use as an accelerator 
vacuum chamber. 
As shown in FIG. 9, the yield value in the inner surface cutting treatment 
is lower in the whole irradiation area than what is obtained from the 
conventional electrolytic polishing treatment. Therefore, the contaminated 
layer 21 as a source of gas desorption is more effectively removed by 
cutting the inner surface than the case of electrolytic polishing, and gas 
desorption is smaller. Moreover, an inner surface layer as a source of gas 
desorption is hardly formed during the inner surface cutting treatment in 
comparison with the electrolytic polishing treatment. In other words, it 
is presumed that the electrolytic polishing newly forms an oxide due to 
the polishing work during the inner surface treatment. This also proves 
that the technique of removing the contaminated layer 21 by means of the 
inner surface treatment using such a broach is more effective in reducing 
gas desorption than the surface treatment using electrolytic polishing. 
Referring to FIGS. 10 and 11, a description will subsequently be give of a 
process for treating the surface of a vacuum chamber by supplying fluid to 
the cutting surface. 
FIG. 10 is a vertical sectional view of a broach capable of supplying gas 
and liquid to the cutting surface of a vacuum chamber. In this embodiment 
of the invention, a main fluid channel 44 is formed close to the central 
part of the broach 10 in the axial direction of the broach 10 from the 
rear end of the rear guide 15. Jet channels 46 are also formed radially 
from the main fluid channel 44 toward the outside of the broach. 
FIG. 11 is a sectional view taken on line A--A of FIG. 10, wherein the main 
fluid channel 44 and the jet channels 46 are formed in the broach shaft 
16. A plug 40 is provided at the entrance of the main fluid channel 44 of 
the rear guide 15 of the broach 10 and used for introducing fluid such as 
gas and liquid. When a hose 42 is coupled to the plug 40, the fluid can be 
supplied to the vacuum chamber 20 from the outside. 
A description will subsequently be given of the effect of the invention at 
the time the inner surface treatment is made while fluid is being 
supplied. The fluid supplied via the hose 42 to the main fluid channel 44 
is passed through the jet channels 46 before being jetted in between the 
cutting edge 11 and the inner surface of the vacuum chamber being cut 
thereby. As shown in the embodiment of FIG. 8, the material 22 of the 
vacuum chamber 20 is exposed when the contaminated and decomposed layer 21 
is cut off. 
In this embodiment of the invention, the inner surface of the vacuum 
chamber may be protected by controlling the conditions thereon since the 
inner surface thereof is cut while a specific gas or liquid is being 
supplied at the time the inner surface treatment is made. The inner 
surface of the vacuum chamber 20 exposed at the time of cutting can be 
prevented from being oxidized because of the atmosphere created by 
supplying inert gas such as argon gas. 
A liquid may also be supplied during the inner surface treatment. Lower 
alcohol or the like may be used in this case. While such lower alcohol is 
being supplied, cutting may be carried out to prevent the layer thus 
exposed from being contaminated again by removing those soluble by the 
solvent. 
When the contaminated layer is cut off, gas together with the liquid may be 
supplied. With the gas and the liquid supplied in combination, the 
respective effects may simultaneously be obtained. In the case of the 
process of treating the inner surface of the vacuum chamber by supplying 
gas or liquid to the cutting surface thereof as shown in FIGS. 10 and 11, 
the gas or liquid is supplied from the rear end of the broach 10 through 
the broach shaft 16. However, the gas or liquid may be supplied from the 
front side of the broach 10 along the rod 32. 
FIG. 12 is an elevational view of a broach for use in treating the inner 
surface of a rectangular vacuum chamber. In this embodiment of the 
invention, the vacuum chamber is octagonal in cross section and even if it 
is polygonal in cross section, the constitutional elements of the broach 
10 are basically similar to those used in the case of the circular one of 
FIG. 4; namely, the broach 10 comprises the front guide 14, the cutting 
edges 11 each having the chip breakers 13, the finishing edges 12, and the 
rear guide 15. The effect of this embodiment of the invention is similar 
to what has been described in reference to the broach 10 circular in cross 
section of FIG. 4. In a side view of FIG. 12, a coupling bolt hole 33 is 
provided to couple the front guide 14 to the rod 32. 
FIG. 13 is a perspective view of the vacuum chamber obtained through the 
process of affixing the branch pipes, flanges and the like required by 
welding after treating the inner surface of the vacuum chamber. When the 
inner surface of the vacuum chamber of the accelerator is treated 
according to the present invention, for example, the inner surface of the 
continuous vacuum chamber is cut in the axial direction, so that the 
contaminated and decomposed layer 21 is removed. Consequently, gas 
desorption due to thermal desorption and photodesorption based on 
synchrotron radiation in an electron storage ring is considerably reduced. 
In addition, the number of charged particles is restrained from decreasing 
in the accelerator such as an electron storage ring. 
As the vacuum chamber produced in accordance with the process of treating 
the inner surface of the vacuum chamber and in the apparatus therefor 
offers high surface planing precision, it is applicable to not only a 
storage ring but also an accelerator, a waveguide and the like. 
FIG. 14 is a diagram illustrating the construction of an apparatus for 
treating the inner surface of a vacuum chamber as a modified embodiment of 
the present invention by moving a vacuum chamber with a broach being fixed 
unlike the case of FIG. 1. While the rod driver 34 is used to move the 
broach 10, the inner surface of the vacuum chamber 20 is treated in the 
embodiment of the invention as shown in FIG. 1. It is however possible to 
treat the inner surface of the vacuum chamber 20 with the broach 10 fixed 
according to the present invention as shown in FIG. 14. 
In the modified embodiment of the invention as shown in FIG. 14, the rod 32 
for supporting the broach 10 is anchored to the support 38 with a fixture. 
On the other hand, vacuum chamber holders 62, 63 are used to couple the 
vacuum chamber 20 as an object to be treated to a vacuum chamber driver 
61, whereby the vacuum chamber 20 together with the vacuum chamber driver 
61 is moved to the right. In this case, though the driving source of the 
vacuum chamber driver 61 is not shown, a drive system such as a ball screw 
or hydraulic drive unit, similar to what is shown in FIG. 1, for pressing 
the vacuum chamber from the left-hand side may be employed. A drive unit 
for pulling the vacuum chamber to the right may also be used. 
When the vacuum chamber driver 61 thus constructed is operated, the inner 
surface of the vacuum chamber 20 is cut by the cutting edges formed on the 
outer periphery of the broach 10. At this time, the vacuum chamber 20 
receives counter force accompanying the inner surface cutting and what 
causes the vacuum chamber 20 to pull back in the direction opposite to the 
arrow of FIG. 14. However, the vacuum chamber holder 62 resists against 
the counter force and causes the vacuum chamber 20 to move together with 
the vacuum chamber driver 61. Even when vertical force is applied to the 
direction in which the vacuum chamber 20 proceeds because of an error in 
the dimension of the inner diameter of the vacuum chamber, the vacuum 
chamber holder 63 stops the vacuum chamber 20 from deflecting in the 
perpendicular direction and causes the vacuum chamber 20 to move together 
with the vacuum chamber driver 61. 
Even in the modified embodiment of FIG. 14, the contaminated and decomposed 
layer 21 on the inner surface of the vacuum chamber 20 can be removed as 
it moves in the axial direction. When the chamber is used as a vacuum 
chamber, gas desorption due to thermal desorption and photodesorption can 
considerably be restrained. 
In the case of the modified embodiment of FIG. 14, the rod 32 and the 
broach 10 attached to the right end of the rod are not moved at the time 
the inner surface of the vacuum chamber 20 is treated. Consequently, the 
hose 42 needs not attaching and detaching when the vacuum chamber 20 as an 
object to be treated is replaced in a case where gas and liquid is 
supplied from the left-hand side of the cutting surface by means of broach 
10. The gas and liquid supply system can thus be simplified in 
construction and readily operated. 
FIG. 15 is an elevational view of a vacuum chamber according to the present 
invention. As shown in FIG. 15, a flange 50 is fitted to both ends of the 
vacuum chamber 20 subjected to the inner surface cutting treatment by 
means of broach 10 and used to couple chambers together to form a vacuum 
vessel 23. One end of the vacuum vessel 23 is coupled to a sealing flange 
51 and the other to a pumping system 70 to complete an airtight vessel. 
The gas contained in the vacuum vessel 23 separated by the sealing flange 
from the atmosphere is discharged via a pumping chamber 71 into the 
pumping system 70 equipped with a gate valve and a vacuum pump. 
FIG. 16 is a top view of a charged particle accelerator formed with an 
annular vacuum vessel and refers to an example of a synchrotron as a 
circular accelerator. Charged particles such as electrons and ions are 
supplied with energy from a RF(Radio Frequency) cavity 81 in the vacuum 
vessel 23 that has been evacuated before being accelerated. In order to 
revolve charged particles stably in the vacuum vessel, two-, four- and 
six-pole electromagnets 80 are arranged in such a way as to surround the 
vacuum vessel. As the number of gas molecules existing in the vacuum 
vessel decreases because of evacuation, it is likely to considerably 
lessen the probability that charged particles collide with gas molecules 
during the time they are accelerated. Consequently, the number of charged 
particles to be scattered and lost in the vacuum vessel is considerably 
reduced. Particularly when the charged particles are electrons, they will 
emit electromagnetic waves called radiation if their orbits are bent by 
the electromagnetic or magnetic field. The inner wall of a vacuum vessel 
is then irradiated with such electromagnetic waves, thus releasing 
quantities of gas due to photodesorption. The gas collides with the 
charged particles and causes the charged particles to become lost and 
short-lived. As the degree of cleanliness in the vacuum vessel of the 
accelerator is raised according to the present invention, the 
photodesorption is made reducible by a large margin, which results in 
prolonging the life of charged particles. Moreover, the controllability of 
the beam shape of a beam as a collection of charged particles is unproved 
as their scattering is lessened. 
As set forth above, the contaminated and decomposed layer formed on the 
inner surface of the vacuum chamber is removable for certain in the axial 
direction of the surface thereof when raw material is used to form the 
vacuum chamber according to the present invention. It is therefore 
possible to significantly reduce the gas desorption from the vacuum vessel 
due to thermal desorption and photodesorption originating from the 
synchrotron radiation generated in the electron storage ring. 
Moreover, the chemical surface treatment of the vacuum chamber and also the 
facilities required therefor become unnecessary. There is also no 
possibility that the inner surface is ruined by the chemical surface 
treatment and that the compound layer as a source of gas desorption is 
newly formed. 
Further, discharge cleaning can also be dispensed with and this prevents 
not only the chamber material from being sputtered during the discharge 
cleaning process but also the discharge gas itself from penetrating into 
the material. 
Still further, the pre-baking is not needed, whereby any reduction in 
material strength can be avoided. 
As a result, it is possible to obtain vacuum chambers offering the least 
gas desorption due to thermal desorption and photodesorption originating 
from the synchrotron radiation.