Abstract:
Disclosed is a device for generating a laser radiation including a box and an electrode, the electrode including a column extending along an axial direction and a collar surrounding the column and having a first face perpendicular to the axial direction and a second face parallel to the first face, the second face facing the box. The generating device includes a ring having a third face bearing against the box, the ring defining a hole emerging on the third face and accommodating the collar, the hole being defined along the axial direction by a bearing face arranged in the ring, perpendicular to the axial direction and facing the box, the first face bearing against the bearing face.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to a device for generating a laser radiation and an associated fabrication method. 
         [0002]    Many types of devices provided for generating a laser radiation include a box in which a gas having a population inversion is confined. Such a population inversion, in which a first “high” energy state is more populated than a second, lower energy state, is necessary for the stimulated emission to become the dominant radiation for a laser radiation to be emitted. 
         [0003]    In order to obtain such a population inversion, it is necessary for the gas contained in the box to be stimulated by an outside energy source. In particular, a plasma is frequently maintained in the box through the application of a difference in potential between two electrodes of the box. Each electrode then covers a hole of the box and must therefore ensure both the electricity transfer and the sealing between the inside and the outside of the box. 
         [0004]    The box is frequently made from glass or vitroceramic, which imposes significant constraints on it regarding the methods used to fasten the electrode to the box. In particular, an indium alloy is frequently used to stick the electrode to the box. However, such an alloy is sensitive to corrosion and must be isolated from the outside by a sealing gasket. Yet the stresses, in particular shear stresses, tend to deteriorate the seal, and therefore the alloy, during the lifetime of the device. This results in a loss of sealing and the contamination or loss of the inside gas. 
         [0005]    During the laser emission, the generating device reaches high temperatures of up to 120 degrees Celsius (° C.). Thus, the generating device is subject to large-amplitude thermal variations between the usage periods and the idle periods. 
         [0006]    Furthermore, it is difficult to separate two parts adhered with such an indium alloy, which makes the device difficult to maintain. A device is known from document WO03/023325 A1 for generating a laser radiation in which a glass ring is inserted between the electrode and the box. The ring is fastened by molecular adhesion to the box and with an indium alloy to the electrode. However, such a ring increases the total height of the relief formed by the electrode, which increases the bulk of the device and makes the latter even more sensitive to shear stresses. 
         [0007]    Furthermore, connections by molecular adhesion and with an indium alloy are difficult to produce and highly sensitive to any damage of the affected surfaces. Yet the aforementioned device does not allow easy monitoring of the state of the surfaces involved in the connection between the ring and the box or the electrode. Here again, this results in a risk of deterioration of the device. 
       SUMMARY OF THE INVENTION 
       [0008]    The aim of the invention is to propose a device for generating a laser radiation that is more reliable. 
         [0009]    To that end, the invention relates to a device for generating a laser radiation including a box and an electrode, the electrode including a column extending along an axial direction and a collar at least partially surrounding the column in a plane perpendicular to the axial direction, the collar having a first face perpendicular to the axial direction and a second face parallel to the first face, the second face facing the box. The generating device further includes a ring for fastening the electrode to the box, the ring having a third face bearing against the box and a fourth face parallel to the third face, the ring defining a first hole and a second hole coaxial to one another, each hole extending along the axial direction, the first hole emerging on the fourth face and at least partially accommodating the column, the second hole emerging on the third face and accommodating the collar. A transverse dimension measured along a direction perpendicular to the axial direction is defined for each hole, the transverse dimension of the first hole being strictly smaller than the transverse dimension of the second hole, the second hole being defined along the axial direction by a bearing face arranged in the ring, the bearing face being perpendicular to the axial direction and facing the box, the first face of the collar bearing against the bearing face of the ring. 
         [0010]    Such a device for generating a laser radiation is less sensitive to any shearing effects applied on the electrode, and the risks of deterioration of the connections between the ring and the electrode are therefore reduced. The device is therefore more reliable. 
         [0011]    The generating device further comprises one or more of the following features, considered alone or according to any technically possible combination(s):
       the column, the collar, the first hole and the second hole are cylindrical with a circular base around a main axis parallel to the axial direction, the main axis being shared by the column, the collar, the first hole and the second hole;   the ring has an inner side face defining the first hole in a plane perpendicular to the axial direction, a play between the column and the inner side face being greater than or equal to 10 micrometers;   a hydrophobic material is inserted between the column and the inner side face;   the ring is made from a material transparent to the visible radiation;   the first face of the collar is fastened to the bearing face of the ring by an adhesive material;   the third face is fastened to the box by molecular bonding;   the generating device is a laser gyrometer.       
 
         [0019]    The invention also relates to a fabrication method for at least one device for generating a laser radiation including a box, the method comprising the following steps:
       providing at least one electrode including a column extending along a first axis and a collar at least partially surrounding the column in a plane perpendicular to the first axis, the collar having a first face perpendicular to the first axis and a second face parallel to the first face,   providing a support having at least one opening, each opening extending along a secondary axis,   providing, for each electrode, a ring for fastening the electrode to the box, the ring having a third face and a fourth face parallel to the third face, the ring defining a first hole and a second hole coaxial to one another, each hole extending along a main axis, the first hole emerging on the fourth face and the second hole emerging on the third face, the second hole being defined along a direction parallel to the main axis by a bearing face arranged in the ring, the bearing face being perpendicular to the main axis,   causing the fourth face of each ring to bear against a support such that each main axis is combined with the secondary axis of a corresponding opening,   depositing an adhesive material on the bearing face of each ring,   positioning each electrode in an inserted position in which the column is at least partially accommodated in an opening of the support and in the first hole of the corresponding ring, the collar being accommodated in the second hole of said ring, the first face of the collar facing the bearing face of the ring, and   applying a force on the third face of each electrode tending to press the first face of the collar against the bearing face of the corresponding ring.       
 
         [0027]    Optionally, a plurality of electrodes are provided during the step for providing at least one electrode, an assembly being defined for each electrode at the end of the application step, each assembly comprising an electrode and the corresponding ring, the method further comprising a step for simultaneous fastening to the box of each assembly, the third face of each ring bearing against the box when the assembly comprising the ring is fastened to the box. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]    The features and advantages of the invention will appear upon reading the following description, provided solely as a non-limiting example, and done in reference to the appended drawings, in which: 
           [0029]      FIG. 1  is a partial sectional view of one embodiment of a device for generating a laser radiation including a box, an electrode and a ring fastening the electrode to the box; 
           [0030]      FIG. 2  is a sectional view of the ring of  FIG. 1 ; 
           [0031]      FIG. 3  is a sectional view of a plurality of assemblies each formed by a ring and an electrode, each assembly bearing against a support; and 
           [0032]      FIG. 4  is a flowchart of the steps of a fabrication method for the generating device of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0033]      FIG. 1  provides a partial sectional view of one embodiment of a device  10  for generating a laser radiation. 
         [0034]    The device  10  is able to emit a laser radiation such as a monochromatic radiation. 
         [0035]    The device  10  contains a gas G and is configured to emit the radiation when the gas G is excited by an electricity source. For example, the device  10  is configured to emit the radiation when a difference in electric potential is applied to two electrodes in contact with the gas G. In particular, the device  10  is configured to emit the radiation when a plasma is generated in the gas G by application of the difference in electric potential. 
         [0036]    The device  10  is a laser gyrometer. A laser gyrometer is a device able to measure an angular speed along at least one plane using the Sagnac effect. 
         [0037]    The gas G is for example a Helium-Neon mixture. 
         [0038]    The device  10  comprises a box  15 , at least one electrode  20  and a ring  25 . 
         [0039]    The box  15  defines a chamber  30  able to contain the gas G. 
         [0040]    The box  15  is configured to prevent the exchange of material between the chamber  30  and the outside of the box  15  when the electrode  20  and the ring  25  are fastened to the box  15 . 
         [0041]    The box  15  is made from an electrically insulating material. For example, the box  15  is made from glass or vitroceramic. In particular, the box  10  is made from glass having a low thermal expansion coefficient, such as Zerodur®. 
         [0042]    The box  15  includes at least one wall  35 . 
         [0043]    In particular, the box  15  includes a plurality of walls  35 , only one of which has been shown in  FIG. 1 . The other walls  35 , not shown, have been indicated by broken lines in  FIG. 1 . 
         [0044]    The walls  35  of the box  15  define the chamber  30  and separate the chamber  30  from the outside of the box  15 . 
         [0045]    The box  15  is for example a prismatic box, or a parallelepiped box. 
         [0046]    The wall  35  has an outer face  40  and defines a first opening  45 . 
         [0047]    The outer face  40  is planar. The outer face is perpendicular to a direction called axial direction D 1 . 
         [0048]    The first opening  45  is open on the outer face  40 . 
         [0049]    The first opening  45  traverses the wall from the chamber  30  to the outside of the box  15 . The first opening  45  is configured to allow contact between the gas G contained in the chamber  30  and the electrode  20 . 
         [0050]    The first opening  45  extends along the axial direction D 1 . For example, the first opening  45  is cylindrical with a circular base. 
         [0051]    The term “cylinder” means that the first opening  45  is defined by two planes parallel to one another and by a surface delimited by all of the straight lines parallel to a straight line called generatrix of the cylinder and intersecting a closed curve, called guide curve of the cylinder. When the parallel planes are perpendicular to the generatrix, the cylinder is said to be “straight”. 
         [0052]    A first axis A 1  is defined for the first opening  45 . “Axis of a cylinder” refers to a straight line parallel to the generatrix and traversing the center of the guide curve. The first axis A 1  is parallel to the axial direction D 1 . 
         [0053]    The guide curve is circular. Such a cylinder is then called “cylindrical with a circular base around the first axis A 1 ”. 
         [0054]    The two planes defining the first opening  45  are perpendicular to the axial direction D 1 . 
         [0055]    The electrode  20  is provided to electrically connect the gas G contained in the chamber  30  and the outside of the box  15 . 
         [0056]    The electrode  20  is made from an electrically conductive material, such as a metal material. For example, the electrode  20  is made from aluminum. 
         [0057]    The electrode  20  comprises a column  50 , a collar  55  and an end wall  60 . 
         [0058]    The column  50  extends along a main axis Ap. 
         [0059]    The column  50  is cylindrical with an annular base. In particular, the column  50  is defined by two coaxial cylinders. The axis of the two cylinders defining the column  50  is called main axis Ap. 
         [0060]    In particular, the two cylinders defining the column  50  have a circular base. In other words, the column  50  is cylindrical with a circular base and is traversed by a cylindrical hole with a circular base coaxial to the column. 
         [0061]    Alternatively, both cylinders have a polygonal base, for example a square base. 
         [0062]    The column  50  has an inner face  65  and an outer face  70 . The column  50  is defined, in a plane perpendicular to the main axis Ap, by the inner face  65  and the outer face  70 . 
         [0063]    Each of the inner face  65  and the outer face  70  is cylindrical with a circular base around the main axis Ap. 
         [0064]    When the column  50  is cylindrical with a circular base, the column  50  has a first inner diameter di 1  and a first outer diameter de 1 . 
         [0065]    The first inner diameter di 1  is measured between two points of the inner face  65  that are connected by a segment perpendicular to the main axis Ap and traversing the main axis Ap. The first inner diameter di 1  is comprised between 10 millimeters (mm) and 40 mm. 
         [0066]    The first outer diameter de 1  is measured between two points of the outer face  70  that are connected by a segment perpendicular to the main axis Ap and traversing the main axis Ap. The first outer diameter de 1  is comprised between 10 mm and 40 mm. 
         [0067]    When the column  50  has a square base, the column  50  has an outer side length. The outer side length is the length of one side of the outer face  70 . The outer side length is comprised between 10 mm and 40 mm. 
         [0068]    The collar  55  is cylindrical with an annular base around the main axis Ap. 
         [0069]    The electrode  20  is defined along the main axis Ap by the collar  55  and by the end wall  60 . 
         [0070]    The collar  55  has a first face  75 , a second face  80  and a peripheral face  85 . 
         [0071]    The first face  75  is perpendicular to the main axis Ap. The first face  75  is planar. 
         [0072]    The second face  80  is parallel to the first face  75 . The second face  80  is preferably planar. 
         [0073]    Among the first face  75  and the second face  80 , the first face  75  is closest to the end wall  60 . Thus, the first face  75  defines the outer face  70  along a direction parallel to the main axis Ap. 
         [0074]    The peripheral face  85  defines the collar in a plane perpendicular to the main axis Ap. The peripheral face  85  surrounds the collar in a plane at the main axis Ap. 
         [0075]    When the column  50  is cylindrical with a circular base, the peripheral face  85  is cylindrical with a circular base around the main axis Ap. 
         [0076]    Alternatively, when the column  50  is cylindrical with a square base, the peripheral face  85  is cylindrical with a square base around the main axis Ap. 
         [0077]    The collar  55  has a second outer diameter de 2 . The second outer diameter de 2  is the diameter of the peripheral face  85 . The second outer diameter de 2  is strictly larger than the diameter of the first opening  45 . The second outer diameter de 2  is comprised between 1 centimeter (cm) and 3 cm. 
         [0078]    The collar  55  has a thickness e greater than or equal to 2 mm. The thickness e of the collar  55  is measured, along a direction parallel to the main axis Ap, between the first face  75  and the second face  80 . 
         [0079]    An example ring  25  has been shown in  FIG. 2 . 
         [0080]    The ring  25  is configured to fasten the electrode  20  to the box  15  in a fastening position. 
         [0081]    The ring  25  is made from a material transparent to the visible radiation. For example, the ring  25  is made from glass. Alternatively, the ring  25  is made from vitroceramic. 
         [0082]    The visible radiation is the set of electromagnetic waves having a wavelength in a vacuum comprised between 400 nanometers (nm) and 800 nm. 
         [0083]    The ring  25  is cylindrical with a circular base around a second axis A 2 . Alternatively, the ring  25  is a parallelepiped. 
         [0084]    The ring  25  has a third outer diameter measured in a plane perpendicular to the second axis A 2 . The third outer diameter is larger than or equal to the second outer diameter de 2  increased by 4 millimeters. 
         [0085]    The ring  25  has a third face  90 , a fourth face  95 , a first inner side face  100 , a second inner side face  105  and a bearing face  110 . 
         [0086]    The ring  25  defines a first hole  115  and a second hole  120 . 
         [0087]    The third face  90  is perpendicular to the second axis A 2 . The third face  90  is planar. 
         [0088]    The third face  90  is provided to be fastened to the outer face  40  of the box by molecular bonding. In particular, the third face  90  is polished. 
         [0089]    The fourth face  95  is parallel to the third face  90 . The fourth face  95  is perpendicular to the second axis A 2 . The fourth face  95  is preferably planar. 
         [0090]    The fourth face  95  is provided to allow a viewer to observe the third face  90  and the bearing face  110  through the fourth face  95 . In particular, the fourth face  95  is polished. 
         [0091]    The first inner side face  100  defines the first hole  115  in a plane perpendicular to the second axis A 2 . The first inner side face  100  is defined in a direction parallel to the first axis A 2  by the fourth face  95  and by the second hole  120 . 
         [0092]    The first inner side face  100  is cylindrical around the second axis A 2 . 
         [0093]    The second inner side face  105  defines the second hole  120  in a plane perpendicular to the second axis A 2 . The second inner side face  105  is defined in a direction parallel to the first axis A 2  by the third face  90  and by the bearing face  110 . 
         [0094]    The second inner side face  105  is cylindrical around the second axis A 2 . 
         [0095]    The bearing face  110  is annular around the second axis A 2 . For example, the bearing face  110  is annular with a circular base. Alternatively, the bearing face  110  is annular with a polygonal base, for example a square base. 
         [0096]    The bearing face  110  is planar. The bearing face  110  is perpendicular to the second axis A 2 . 
         [0097]    The bearing face  110  defines the second hole  120  along a direction parallel to the second axis A 2 . 
         [0098]    The bearing face  110  is opposite the fourth face  95 . In particular, at least one portion of the ring  110  is defined along a direction parallel to the second axis A 2  by the fourth face  95  and by the bearing face  110 . 
         [0099]    The bearing face  110  is rough. For example, the bearing face  110  is not polished after machining. 
         [0100]    The first hole  115  is configured to accommodate the column  50  when the ring  25  fastens the electrode  20  in the fastening position. 
         [0101]    The first hole  115  extends along the second axis A 2 . For example, the first hole  115  is cylindrical around the second axis A 2 . The first hole  115  is preferably a straight cylinder. 
         [0102]    When the column  50  is cylindrical with a circular base, the first hole  115  is cylindrical with a circular base. 
         [0103]    Alternatively, the first hole  115  is cylindrical with a polygonal base. For example, when the column  50  is cylindrical with a square base, the first hole  115  is cylindrical with a square base, therefore parallelepiped. 
         [0104]    The first hole  115  emerges on the fourth face  95 . 
         [0105]    The first hole  115  emerges on the bearing face  110 . 
         [0106]    A first transverse dimension Dt 1  is defined for the first hole  115 . The first transverse dimension Dt 1  is measured along a direction perpendicular to the second axis A 2 . 
         [0107]    When the first hole  115  is cylindrical with a circular base, the first transverse dimension Dt 1  is a diameter of the first hole  115 . 
         [0108]    When the first hole  115  is cylindrical with a square base, the first transverse dimension Dt 1  is a length of one side of the square. 
         [0109]    The first transverse dimension Dt 1  is strictly larger than the first outer diameter de 1 . 
         [0110]    The first transverse dimension Dt 1  is greater than or equal to the first inner diameter di 1  and less than or equal to the second outer diameter de 2  minus twice the thickness e. 
         [0111]    The second hole  120  is configured to accommodate the collar  55  when the ring  25  fastens the electrode  20  in the fastening position. 
         [0112]    The second hole  120  and the first hole  115  are coaxial to one another. 
         [0113]    The second hole  120  extends along the second axis A 2 . For example, the second hole  120  is cylindrical around the second axis A 2 . The second hole  120  is preferably a straight cylinder. 
         [0114]    The second hole  120  is for example cylindrical with a circular base when the peripheral face  85  is cylindrical with a circular base. 
         [0115]    Alternatively, the second hole  120  is cylindrical with a polygonal base. For example, the second hole  120  is for example cylindrical with a square base, therefore parallelepiped, when the peripheral face  85  is parallelepiped. 
         [0116]    The second hole  120  emerges on the third face  90 . 
         [0117]    The second hole  120  is defined, in a plane perpendicular to the second axis A 2 , by the bearing face  110 . 
         [0118]    A second transverse dimension Dt 2  is defined for the second hole  120 . The second transverse dimension Dt 2  is measured along a direction perpendicular to the second axis A 2 . 
         [0119]    When the second hole  120  is cylindrical with a circular base, the second transverse dimension Dt 2  is a diameter of the second hole  120 . 
         [0120]    When the second hole  120  is cylindrical with a square base, the second transverse dimension Dt 2  is a length of one side of the square. 
         [0121]    The second transverse dimension Dt 2  is strictly greater than the first transverse dimension Dt 1 . The second transverse dimension Dt 2  is strictly greater than the second outer diameter de 2 . 
         [0122]    The second hole  120  has a depth P. The depth p is measured along a direction parallel to the second axis A 2  between a point of the third face  90  and a point of the bearing face  110 . 
         [0123]    The depth p is strictly greater than the thickness e of the collar  55 . For example, a difference between the depth p and the thickness e of the collar  55  is greater than or equal to 50 μm, preferably greater than or equal to 100 μm. The depth p is further less than or equal to 200 μm. 
         [0124]    When the electrode  20  is kept in the fastening position by the ring  25 , the first axis A 1 , the second axis A 2  and the main axis Ap are combined. The first axis A 1 , the second axis A 2  and the main axis Ap are then all parallel to the axial direction D 1 . 
         [0125]    When the electrode  20  is kept in the fastening position by the ring  25 , the third face  90  bears against the outer face  40  of the box  15 . The bearing face  110  then faces the box  15 . 
         [0126]    Preferably, the third face  90  is fastened to the outer face  40  of the box  15  by molecular bonding. Molecular bonding is a technique for fastening parts to one another in which two very smooth surfaces free of contamination adhere to one another going to Van der Waals forces. 
         [0127]    When the electrode  20  is kept in the fastening position by the ring  25 , the first face  75  of the collar  55  bears against the bearing face  110  of the ring  25 . Preferably, the first face  75  is fastened to the bearing face  110  by an adhesive material  125  received between the first face  75  and the bearing face  110 . 
         [0128]    The adhesive material  125  is for example an indium alloy. 
         [0129]    The adhesive material  125  has a thickness comprised between 50 micrometers (μm) and 150 μm. 
         [0130]    When the electrode  20  is kept in the fastening position by the ring  25 , a distance, measured along the axial direction D 1 , between the second face  80  and the outer face  40 , is less than or equal to 100 μm. 
         [0131]    Preferably, when the electrode  20  is kept in the fastening position by the ring  25 , a mechanical play between the column  55  and the first inner side face  100  is greater than or equal to 10 μm. For example, the play is greater than or equal to 100 μm. 
         [0132]    A seal  130  is inserted between the outer face  70  of the column  50  and the first inner side face  100 . The seal  130  is configured to isolate the adhesive material  125  from the outside atmosphere. In particular, the seal  130  is configured to protect the adhesive material  125  from corrosion. 
         [0133]    The seal  130  is made from a hydrophobic material. For example, the seal  130  is made from a resin, such as an epoxy resin. Alternatively, the seal  130  is made from a silicone glue. According to another alternative, the seal  130  is made from a silicone varnish. 
         [0134]    A fabrication method of the device  10  will now be described, in one embodiment suitable for the fabrication of a plurality of devices  10 . 
         [0135]      FIG. 4  shows a flowchart of the steps of the fabrication method. 
         [0136]    During a supply step  200 , at least one electrode  20  is supplied. For example, a plurality of electrodes  20  is supplied. A ring  25  is also supplied for each electrode  20 . 
         [0137]    Furthermore, a support  135  is also supplied. 
         [0138]    The support  135  is for example a plate. 
         [0139]    The support  135  is made from a rigid material, such as a metal material, for example steel. Alternatively, the support  135  is made from another material, ceramic, or glass. 
         [0140]    The support  135  has a planar face  140 . 
         [0141]    The support  135  has at least one second opening  145 . In particular, the support  135  has a second opening  145  for each electrode  20 . 
         [0142]    Each second opening  145  extends along a secondary axis As. Each secondary axis As is perpendicular to the planar face  140 . 
         [0143]    Each second opening  145  is cylindrical around the corresponding second axis As. For example, each second opening  145  is cylindrical with a circular base. Alternatively, each second opening  145  is cylindrical with a polygonal base, for example with a square base. 
         [0144]    A third transverse dimension Dt 3  is defined for each second opening  145 . The first third transverse dimension Dt 3  is measured along a direction perpendicular to the secondary axis As. 
         [0145]    When the second opening  145  is cylindrical with a circular base, the third transverse dimension Dt 3  is a diameter of the second opening  145 . 
         [0146]    When the second opening  145  is cylindrical with a square base, the third transverse dimension Dt 3  is a length of one side of the square. 
         [0147]    The third transverse dimension Dt 3  is strictly larger than the first outer diameter de 1 . For example, the third transverse dimension Dt 3  is equal to the first transverse dimension Dt 1 . 
         [0148]    Each second opening  145  is configured to at least partially accommodate the column  50  of an electrode  20 . 
         [0149]    During a placement step  210 , each ring  25  is placed bearing against the planar face  140  of the support  135 . The main axis Ap of each ring  25  is then combined with the secondary axis As of the corresponding second opening  145 . 
         [0150]    During a deposition step  220 , the adhesive material  125  is deposited on the bearing face  110 . The deposition step  220  is for example done after the placement step. Alternatively, the adhesive material is deposited before the ring  25  is placed. 
         [0151]    During a positioning step  230 , each electrode  20  is placed in a respective inserted position. When the electrode  20  is in the inserted position, the column  50  is at least partially accommodated in the corresponding second opening  145  and in the first hole  115  of the ring  25 . In particular, each column  50  successively traverses the first hole  115  and the second opening  145  along a direction parallel to the secondary axis As. 
         [0152]    The collar  55  is then accommodated in the second hole  120 . In particular, the collar  55  is surrounded by the second inner side face  105  in a plane perpendicular to the second axis A 2 . 
         [0153]    When the electrode  20  is in the inserted position, the first face  75  of the collar  55  faces the bearing face  110 . 
         [0154]    A single support  135 , three rings  25  and three electrodes  20  have been shown in  FIG. 3 . In  FIG. 3 , each electrode  20  is in the inserted position, and each ring  25  is bearing against the planar face  140 . 
         [0155]    During an application step  240 , a force having at least one component parallel to the main axis Ap is applied on the second face  80  of each collar  55 . The forces have been shown by arrows in  FIG. 3 . 
         [0156]    Each force is oriented toward the bearing face  110 . In particular, each force tends to press the first face  75  of the collar  55  against the bearing face  110  of the corresponding ring  25 . 
         [0157]    At the end of the application step  240 , a plurality of assemblies are then formed, each assembly comprising an electrode  20  and the ring  25  in which the electrode  20  is inserted. 
         [0158]    During a fastening step  250 , each assembly is fastened to the box  15  of at least one corresponding device  10 . For example, each box  15  receives a single corresponding assembly. 
         [0159]    Alternatively, at least one box  15  receives a plurality of assemblies. In other words, at least two assemblies are fastened to a same box  15 . 
         [0160]    During the fastening step  250 , each ring  25  is fastened to the corresponding box  15 . Each ring  25  then keeps the corresponding electrode  20  in its respective fastening position. 
         [0161]    Preferably, during the fastening step  250 , the assemblies are simultaneously fastened to the corresponding box or boxes  15 . For example, all of the assemblies are simultaneously attached on the corresponding box or boxes owing to the support  135 , then fastened to the corresponding box or boxes by molecular bonding. 
         [0162]    Owing to the ring  25 , the consequences of any shear forces applied on the electrode  20  are limited. In particular, the seal  130  is not very sensitive to these shear forces, and the risk of corrosion of the adhesive material  125  is limited. The device  10  is therefore more reliable. 
         [0163]    Furthermore, owing to the ring  25 , the height of the relief formed by the electrode  20  on the outer face  40  of the box  15  is reduced. The bulk of the device  10  is therefore reduced. 
         [0164]    Furthermore, due to the use of molecular bonding, it is relatively easy to separate the ring  25  from the box  15 . The maintenance of the device  10  and the replacement of a faulty electrode  20  or ring  25  are therefore made easier. 
         [0165]    Furthermore, it is easy to observe the interfaces between the third face  90  and the outer face  40  of the box  15  and between the first face  75  of the collar and the bearing face  110  through the fourth face  95 . These connecting interfaces can therefore be monitored by an operator, which facilitates the early detection of scratches or deterioration. A preventive intervention is then done easily, before the deterioration has caused permanent damage to the device  10 . 
         [0166]    The play between the outer face  70  and the first inner side face  100  prevents the temperature variations during the operation of the device  10  from causing the appearance of significant thermal stresses capable of damaging the ring  25  or the electrode  20 , which further improves the reliability of the device  10 . 
         [0167]    By using the ring  25 , it is easy to place several electrodes simultaneously on one or several boxes  15 . Thus, the fabrication method is made faster than the methods of the state of the art. In particular, the fabrication method is easy to automate. 
         [0168]    Furthermore, the fastening of the electrode  20  to the ring  25  has little risk of damaging the surfaces, which will be fastened to one another afterwards by molecular bonding. Here again, the reliability of the device  10  is improved.