FR2942007A1 - Installation for drying large-sized pieces in e.g. synchrotron in hadrontherapy field, has gas analyzer connected to main chamber, and power circuit for powering pumping installations and heating coils - Google Patents

Abstract

The installation has an ultra-high vacuum pumping installation (30) connected separately to a main chamber (10). A control center (40) includes an operation management circuit with a microprocessor (41), programs (42) and a control and data input (44). The center is connected to a cold cathode gauge (13), a Pirani gauge (14) and a pressure gauge (25). Temperature sensors (18, 19) are associated with the main chamber and a vacuum pumping installation (20). A gas analyzer (16) is connected to the main chamber. A power circuit (43) powers the pumping installations and heating coils (11, 12). An independent claim is also included for a method for drying pieces to be exposed to a high vacuum or ultra-high vacuum.

Description

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FIELD OF THE INVENTION The present invention relates to a steaming plant for the preparation of parts intended to be exposed to a high or ultra-high vacuum.

The invention also relates to a method for steaming an exposed part at high vacuum. State of the art There are many areas of scientific research and medicine, using ultra-high vacuum facilities. Until recently it was a vacuum of about 10-8 up to 10-9 mbar and the current trend is to push ultra-high vacuum to 10-12 mbar. The parts used in these installations, which are generally stainless steel enclosures, must be particularly cleaned of any traces likely to pollute the enclosure. These are traces of products used during manufacturing or fingerprints, corresponding to carbon-based products. To eliminate these different pollutant compounds inside the equipment parts intended for ultra-high vacuum, it is necessary to pump the internal volume of the parts to eliminate all the molecules that can remain inside the parts. This cleaning of parts is done by steaming. For this, it is necessary to realize the vacuum in the volume of the room by pumping gradually, first with a primary pump and then a secondary pump and finally, an ion pump to eliminate and trap as much as possible, the molecules . These operations are generally done by heating the parts to a temperature of about 200 ° C so as to agitate the molecules and to unhook them from the inner wall of the room to be able to trap them by the pumps that eliminate these molecules or by an ion pump that traps the molecules. In general, there are currently two methods for cleaning or degassing parts for installations working in the ultra-high vacuum. One of the methods consists in using degassing furnaces which are in fact incubators making it possible to obtain a temperature of the order of 200 ° C. and a pressure of 10 -2 mbar. But this process is limited to a primary vacuum and not to a secondary vacuum or ultra-vacuum. The parts are introduced into the oven and the temperature obtained is measured in steps without being able to define and determine a temperature and vacuum cycle. 2

In addition, the ovens can only treat parts with a limited volume. This method does not allow to steam large installations. There is also no final control possible, since no gas analysis is done and no ultrahigh hold test is feasible. A second existing method consists in producing an in-line baking process. Thus, the equipment to be steamed is surrounded by heating cords and the equipment pumping system is used. This steaming is carried out on the site of the installation which can also use a mass spectrometer connected to a quill so as to analyze the residual gases before and after the parboiling. This method provides better results than the first method but the heating is relatively random and can be precise. There is no control or programming of the rise in temperature. In addition, the baking phases are very long because the rise in temperature can not be optimized. It is the same with the secondary vacuum or ultra-high vacuum. Finally, the chamber to be steamed must be equipped with pumping equipment. OBJECT OF THE INVENTION The object of the present invention is to develop an installation and a parboiling process making it possible to efficiently treat even large parts intended to work in the ultra-high vacuum by precisely controlling the parboiling and its result. DESCRIPTION AND ADVANTAGES OF THE INVENTION To this end, the present invention relates to an installation comprising a main chamber receiving the room or connected to the room, a room and room heating equipment, a pumping installation of vacuum for the primary vacuum and the secondary vacuum connected to the main chamber and provided with a cou-pure valve to cut the connection between the pumping installation and the main chamber, - an ultra-high vacuum pumping installation connected separately to the main chamber, a control unit comprising - an operation management circuit with a microprocessor, programs and a command and data input, connected to a set of vacuum gauges and temperature sensors associated with the

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main chamber and vacuum pumping system, and also a residual gas analyzer connected to the main chamber, and - a power circuit supplying the vacuum and ultra-high vacuum pumping systems and the heating means.

The invention also relates to a part steaming process intended to be exposed to a high vacuum to implement such an installation, this method being characterized in that a first baking cycle is performed for a boundary vacuum reading. cold then a second cycle for a vacuum and the determination of the spectrum of the species present in the chamber, according to which - during the first cycle of steaming, in cold, it performs a primary pumping and then a turbomolecular pumping in the room followed by pumping with an ion pump and when the pressure equilibrium is reached, the primary pumping circuit and the turbomolecular pumping circuit are separated to measure the cold vacuum in the chamber and an analysis is made. cold gas, and - during the second baking cycle the ion pump is stopped and the valve is opened to perform a secondary pumping, the enclosure is heated by controlling the rise in temperature and maintaining the temperature at a given value to unhook the molecules and pump them with the secondary pump which evacuates them, then the temperature is lowered and at a temperature of 80 ° C., the ion pump is started and when the equilibrium of the pressure is reached, the enclosure is closed and a reading is made of the hot limit vacuum, the residual gases are analyzed and the pumping stops, then the nitrogen is injected into the chamber to rise in pressure and it opens The enclosure The stoving installation and its method of implementation make it possible to efficiently treat large volume parts with gas analysis and ultrahigh strength tests. The installation and the method 30 make it possible to program the rise in temperature and optimize the temperature rise cycle for the very long baking phases. In general, the invention constitutes an assembly specially designed for steaming and for controlling the thermal cycle with primary, secondary and ultra-high vacuum equipment up to 10-12 mbar. The installation and the process allow a final control by placing under ultrahigh vacuum and measuring the minimum pressure that can be reached and measuring the composition of the residual gases. This

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final control allows, if necessary, to renew the operation if the objectives are not achieved. Thus, the installation performs the parboiling and the tests controlling or justifying the quality of the results.

The method provides a fast treatment compared to the known method and installation and especially a more reliable treatment. These results are also accessible to the user who will be able to interrogate the control unit to follow the evolution of the parboiling and control the results.

The quality of the results will be maintained until the installation of the part on the installation for which it is intended because the pure nitrogen injected lining the walls and prevents external pollution of the room or its enclosure. Nitrogen has the advantage of coming off very easily during the following pumping done on the installation equipped with the part. This protection, which is limited in time, is sufficient for delivery and assembly operations. According to another advantageous characteristic, the vacuum pumping installation comprises a primary pump and a secondary pump for respectively producing a primary vacuum and a secondary vacuum, and a pressure gauge, the primary pump, the secondary pump and the pressure gauge being connected to a pipe downstream of the valve connecting the pipe to the main chamber. According to another advantageous characteristic, the primary pump is a dry primary pump and the secondary pump is a turbomolecular pump. According to another advantageous characteristic, the main chamber is equipped with a cold cathode gauge and a Pirani gauge. According to another advantageous characteristic, the ultrahigh vacuum pumping installation is constituted by an ion pump. According to another advantageous characteristic, the main chamber is connected to a nitrogen supply. Drawings The present invention will be described in more detail below with the aid of an example of an ultrahigh vacuum oven installation and method, shown in the accompanying drawings in which: FIG. 1 is a block diagram of the installation according to the invention; FIG. 2 is a perspective view of an example of a stoving installation according to the invention; FIG. 3 is a diagram of the process; stoving according to the invention. DESCRIPTION OF EMBODIMENTS OF THE INVENTION FIG. 1 very generally shows an installation according to the invention for steaming rooms for the ultra-high vacuum. A piece P is schematically represented by a rectangle corresponding to a volume or an enclosure that must be cleaned to remove molecules and traces of pollutants remaining within the volume of the room and which do not allow to reach a vacuum pushed, to use this piece in an ultra-high vacuum installation. The piece P is placed in the installation or is connected thereto according to the dimensions of the part. The steaming plant according to the invention consists of a main chamber 10, for example in the form of a cylindrical volume in which the piece to be steamed P can be placed if it is small or on which the volume of the part to be steamed is connected by a tight connection. This case is schematically represented in FIG. 1. The main chamber 10 is connected on the one hand to a primary vacuum and secondary vacuum pump installation 20 and on the other hand to an ultrahigh vacuum pump installation 30. The chamber 10 is equipped with pressure sensors 13, 14, 15 and temperature 18, 19 as well as a gas analyzer 16 and a nitrogen source N2 (17). The installation comprises a control unit 40 provided with an input 44 such as a keyboard and a recording system 45 as well as a link 46 with a remote system 50, for example installed in the user's home. the room for data transmission. The control unit 40 is connected to the sensors 13, 14, 15, 18, 19 and to the analyzer 16 from which it receives the signals to process them and control the operation of the installation. According to established programs, it controls the heating means 11, 12 of the main chamber 10 and, if appropriate, of the piece P when it is not placed in the main chamber, the operation of the two pumps. 23, 24 of the primary vacuum pump system and secondary vacuum pump and the ultrahigh pump system 30. The control unit is connected to an input 44 such as a keyboard and a recorder 45, for example a memory of mass and / or printer. Through the data exchange link 46, the user 50 can access the data relating to the parboiling of his workpiece P and in particular to the result of the parboiling.

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The control unit 40 includes a microprocessor 41, a program memory 42 and a power circuit 43 to control and power the various equipment. In more detail, the main chamber 10 comprises a heating equipment 11 which can be split by heating equipment 12 placed on the room to be steamed P if it is external to the main chamber. These heating means 11, 12 are connected to the power circuit 43 which supplies them in a controlled manner. The primary vacuum pump and secondary vacuum pump 20 is formed by a pipe 21 connected through a controlled valve 22 to the main chamber 10; the pipe 21 is connected upstream of the valve 22 to a secondary pump 24 and then to a primary pump 23. The primary pump 23 is for example a dry primary pump working up to a pressure of about 10 -2 mbar; the secondary pump 24 is a turbomolecular pump taking over to pump the vacuum to 10-6 mbar. The pipe 21 is equipped with a pressure gauge 25 upstream of the valve 22. The main chamber 10 is connected directly to an ion pump 30 and to a pressure gauge such as a cold cathode gauge 13 and a dipstick Pirani 14. The cold cathode gauge 13 measures pressures from 10-3 to 10-12 mbar and the Pirani gauge 14 measures a vacuum range up to 10-3 mbar. This gauge 14 is used in parallel with the cold cathode gauge 13 in the case of a re-venting of the chamber 25 only, the valve 22 remaining closed. The ion pump 30 makes voids of between 10-6 and 10-12 mbar. The main chamber 10 is also connected to a gas analyzer 16 and to a nitrogen source 17, for example a nitrogen bottle. The temperature of the main chamber 10 and that of the part P are measured by temperature sensors 18, 19. The control unit 40 receives the signals from the pressure gauge 25 via a line S25, the signals from the pressure gauges 13 and 14 by signal lines S13, S14, those of the temperature sensor 18 of the main chamber 10 by the signal line S18 and the temperature of the temperature sensor 19 of the part P by the signal line S19 .

Depending on the signals thus received and the selected baking program specifying in particular the parameters of the parboiling and the objectives to be achieved, the control unit 40 defines control signals transmitted to the valve 22 via the line C22, the control of the primary pump 23 by the control line C23, the control of the secondary pump 24 by the control line C24. The heating element 11 is controlled by the control line C 11, the heating element 12 of the room P is controlled by the control line C12 and the ion pump 30 is controlled by the control line C30.

At the end of the baking cycles or during the cycle, the gas analyzer 16 transmits the results of the analysis by the signal line S16 to the control unit 40. FIG. 2 shows an embodiment of the invention. stoving installation described generally using FIG.

The main chamber 10 is constituted by a cylinder provided with different means of connection in the form of flanges, for example a flange 101 for the connection of the piece P and at its other end, a flange 102 for connecting the pumping installation. primary and secondary 20.

The cylindrical chamber 10 is surrounded by heating means 11 in the form of a coil. It is the same for the part P which is provided with heating coils 12, distributed around different elements of the part, for example fittings. All the flanges of part P are hermetically sealed by solid flanges.

The main chamber 10 is connected to the primary and secondary pumping installation 20 by the electro-pneumatically controlled valve 221. At the outlet of the valve 22, the gauge 25 is connected to the pipe 21 constituted by a set of flanged pipes also bearing the secondary pump 24 which is a turbomolecular pump and the primary pump 23. The main chamber 10 is also connected to the ion pump 30. It comprises a gas analyzer 16. On one side, it is equipped with the gauge Pirani 14 and on on the other side, it includes the cold cathode gauge 13. The nitrogen bottle is not shown. All of this equipment is installed on a frame 200. The connection with the control unit 40 and the equipment attached to this plant are not shown. FIG. 3 is a diagram showing the parboiling process according to the invention, carried out with an installation taken in the general sense

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as the one of Figure 1 or the embodiment of this installation shown in Figure 2. The baking process consists of a first cold cycle and a second heat cycle. 1st baking cycle During the first cycle, the following steps are carried out: Firstly in stage E1, the piece P is connected to the main chamber so as to communicate the interior volume of the room with the interior volume of the chamber 10 and form the enclosure in which it can be pumped. - In step E2, the primary and secondary pumping installation 20 is connected by opening the valve 22. - Then in a first pumping step E3, the primary pump 23 pumps the vacuum to about 10 -2 mbar - Then the secondary pumping makes it possible to reach 10-8 mbar 15 - Once this pressure is reached, the ion pumping 30 is started in the chamber 10 (valve 22 always open) - the measurement of the pressure supplied by the cold cathode gauge is monitored. 13 and the gauge 25 by the measurement steps E6 and E7. - Comparing (step E8) the two measured pressures PR and PR '. 20 - In case of equality of the two pressures, it controls the valve 22 (step E9) to close and isolate the chamber of the main chamber 10 and the piece P. - Let the ion pump 30 go to the maximum of pumping - The cold vacuum pressure is measured (step E10) and the analyzer 16 (step E 11) analyzes the gases. - The ion pump 30 is stopped (step E12) and the results are recorded (step E14), that is to say the cold limit vacuum and the species or the spectrum of the species present in the enclosure formed by the chamber The main cycle 10 and the piece P. 30 2nd cycle of steaming After this first cycle of steaming, the second cycle of steaming is carried out with, for starting conditions, the cold vacuum and the spectrum of all the species present in the steam cycle. enclosure formed by the main chamber 10 and the volume of the piece P. During the second cycle of steaming, the following operations are carried out: the ion pump 30 is stopped;

9 - The valve 22 (step E20) is opened to communicate the chamber 10 and the part P with the primary and secondary vacuum pumping installation 20. - The secondary vacuum pump 24, which has not been stopped, continues to pump (step E21). At the same time, the heating (step E22) of the main chamber 10 and of the room P is controlled; the temperature (step E23) and the heating time are monitored. This step can last several days. The heating agitates the molecules which are detached from the surfaces to which they are hooked so that the pressure increases. This is the phenomenon of degassing. The evacuation of the molecules is by pumping other than ionic pumping so as to evacuate the molecules to the outside. - Then, in a next step E24, the temperature is lowered to reach the limit of 80 ° C (step E25) and the ion pump 30 is started (step E26); the ionic pumping does not evacuate the molecules to the outside but it simply captures them. The pumping is monitored by measuring the pressure of the gauge 25 and cold cathode gauge 13 (pressures PR and PR ') (step E27). - In case of equality of the two pressures (step E28), it controls the closing of the valve 22 (step E29). Chamber 10 and Room P are again isolated. Expect ionic pumping to reach maximum. - The pumping is stopped (step E30) and the gases are analyzed (step E31) with the analyzer 16. - The cycle ends with the nitrogen injection (step E32) to temporarily neutralize the part. The bake cycles are fully automated and operations can be done efficiently and quickly.

Steaming according to the invention makes it possible to increase the limit vacuum, that is to say to push the limit vacuum beyond the present limits and to reduce the quantity of certain remaining species, such as water. At the end of steaming, the injection of pure nitrogen lined the walls of the room to prevent pollution of the enclosure while being able to easily fall out very easily when pumping is carried out once the piece has been installed. place on the installation for which it is intended. 10 15

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The protection provided by the nitrogen coating is sufficient to allow the disassembly of the part with respect to the parboiling plant, its closure, on-site transportation and relocation. The various stages of the bake cycles can be followed by the user of the part to control the efficiency of the operations himself. If the analysis done at the end of the second baking cycle shows that the results obtained are insufficient, the baking cycle is repeated. Parts thus parboiled are parts intended mainly for vacuum chambers or vacuum enclosures. These parts are used in vacuum installations such as particle accelerators such as synchrotrons and cyclotrons. The vacuum chambers are also used in medical applications, for example for the field of hadrontherapy. Finally, such facilities are used in nuclear physics in many research laboratories. 20

Claims (1)

CLAIMS 1 °) Stoving installation for the preparation of parts to be exposed to a high vacuum or ultra-high vacuum, characterized in that it comprises A- a main chamber (10) receiving the piece (P) or connected to the piece (P), - a heating equipment (11, 12) of the chamber (10) and the part (P), lo - a vacuum pumping installation (20) for the primary vacuum and the connected secondary vacuum to the main chamber (10) and provided with a shut-off valve (22) for cutting the connection between the pumping installation (20) and the main chamber (10), - an ultra-high vacuum pumping installation (30) separately connected to the main chamber (10), B- a control unit (40) comprising an operation management circuit with a microprocessor (41), programs (42) and a control and data input (44) connected to a set of vacuum gauges (13,14,25) and temperature sensors (18,19) associated with the main chamber (10) and the vacuum pumping system (20), and also a residual gas analyzer (16) connected to the main chamber (10), and - a power circuit (43) supplying the systems vacuum pump (20, 30) and ultrahigh vacuum (30) and the heating means (11, 12). 2 °) stoving installation according to claim 1, characterized in that the vacuum pumping installation (20) comprises a primary pump (23) and a secondary pump (24) for respectively producing a primary vacuum 30 and a secondary vacuum, and a pressure gauge (25), the primary pump (23), the secondary pump (24) and the pressure gauge (25) being connected to a pipe (21) downstream of the valve (22). ) connecting the pipe (21) to the main chamber (10). 3 °) parboiling installation according to claim 2, characterized in that the primary pump (23) is a dry primary pump and the secondary pump (24) is a turbomolecular pump. 51012 4 °) Stoving installation according to claim 1, characterized in that the main chamber (10) is equipped with a cold cathode gauge (13) and a Pirani gauge (14). 5 °) parboiling installation according to claim 1, characterized in that the ultra-vacuum pumping installation (30) is constituted by an ion pump. 6 °) steaming installation according to claim 1, characterized in that the main chamber (10) is connected to a nitrogen supply (17). 7 °) Process for steaming a part intended to be exposed to a high vacuum to implement the installation according to any one of Claims 1 to 6, characterized in that a first cycle of baking for a reading of the limit vacuum, cold, then a second cycle for a limit vacuum and the determination of the spectrum of the species present in the chamber of the room, during the first cycle of steaming, cold, is carried out primary pumping and then secondary pumping in the enclosure formed by the main chamber (10) and the workpiece (P), followed by pumping with the ion pump (30) and when the pressure equilibrium is reached the primary and secondary pumping circuit (20) is separated to measure the cold boundary vacuum in the enclosure (10, P) and the gases are analyzed cold and then the second baking cycle is carried out. the ion pump (30) is stopped and the valve (22) is opened for pumping. econdaire (24) and heated (11, 12) the chamber (10) or the piece (P) by controlling the rise in temperature and the temperature is maintained at a given value to unhook the molecules and pump them with the secondary pump (24) which evacuates them, then the temperature is lowered and at a temperature of 80 ° C., the ion pump (30) is started and when the pressure equilibrium is reached, the chamber (10) is closed and makes a reading of the hot limit vacuum, the residual gases are analyzed (16) and the pumping stops, then nitrogen (17) is injected into the chamber (10) to rise in pressure and the chamber is opened (10, P).