WO2019122924A1 - Chambre à vide, pièces associées et procédé de fabrication associé - Google Patents

Chambre à vide, pièces associées et procédé de fabrication associé Download PDF

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Publication number
WO2019122924A1
WO2019122924A1 PCT/GB2018/053750 GB2018053750W WO2019122924A1 WO 2019122924 A1 WO2019122924 A1 WO 2019122924A1 GB 2018053750 W GB2018053750 W GB 2018053750W WO 2019122924 A1 WO2019122924 A1 WO 2019122924A1
Authority
WO
WIPO (PCT)
Prior art keywords
window
chamber
vacuum
vacuum chamber
wall
Prior art date
Application number
PCT/GB2018/053750
Other languages
English (en)
Original Assignee
Teledyne E2V (Uk) Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Teledyne E2V (Uk) Limited filed Critical Teledyne E2V (Uk) Limited
Priority to EP18829959.8A priority Critical patent/EP3729205A1/fr
Publication of WO2019122924A1 publication Critical patent/WO2019122924A1/fr

Links

Classifications

    • G—PHYSICS
    • G04—HOROLOGY
    • G04F—TIME-INTERVAL MEASURING
    • G04F5/00—Apparatus for producing preselected time intervals for use as timing standards
    • G04F5/14—Apparatus for producing preselected time intervals for use as timing standards using atomic clocks
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J3/00—Processes of utilising sub-atmospheric or super-atmospheric pressure to effect chemical or physical change of matter; Apparatus therefor
    • B01J3/004—Sight-glasses therefor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16J—PISTONS; CYLINDERS; SEALINGS
    • F16J12/00—Pressure vessels in general
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16J—PISTONS; CYLINDERS; SEALINGS
    • F16J15/00—Sealings
    • F16J15/02—Sealings between relatively-stationary surfaces
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B7/00—Mountings, adjusting means, or light-tight connections, for optical elements
    • G02B7/007—Pressure-resistant sight glasses
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21K—TECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
    • G21K1/00—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating
    • G21K1/006—Manipulation of neutral particles by using radiation pressure, e.g. optical levitation

Definitions

  • This invention relates to vacuum chambers having a window, parts therefor and a method for manufacturing such vacuum chambers, and particularly but not exclusively to vacuum chambers included in cold atom or cold ion apparatus.
  • Cold atoms or ions are used to achieve quantum mechanical effects for use in cold atom clocks, gravimeters or other apparatus.
  • the desired cold state is achieved by using a laser or lasers to reduce the kinetic energy of the atoms or ions in a low vacuum environment.
  • the cold matter is then manipulated using lasers to produce an effect caused by the characteristic under investigation. Lasers may then be used to measure the effect produced.
  • Vacuum chambers are also used in non-quantum technology applications.
  • a vacuum chamber comprises: a vacuum chamber wall having an aperture therethrough and an electromagnetic radiation transmissive window positioned in the aperture, the window having an external face external to the chamber and an internal face internal to the chamber, the external face having a larger area than the internal face, a peripheral surface of the window being inclined relative to the normal to the plane of the internal and external faces, with a vacuum seal between the window and the wall at the inclined peripheral surface and the vacuum seal being extensive over less than or equal to two thirds of the dimension of the peripheral surface in a direction from the internal face to the external face.
  • the vacuum seal is extensive over one third or less of the dimension of the peripheral surface in a direction from the internal face to the external face.
  • the window configuration and vacuum within the vacuum chamber provide optical surfaces with good flatness. Flatness is particularly important for applications where light must travel several times through the window, where any deviations can lead to radiation losses and affect performance.
  • the window flatness may be better than or equal to 40 nm over the central 90% of the window.
  • the window may be
  • the external face and the internal face of the window are substantially parallel.
  • the window is of circular cross section but other
  • the ratio of the thickness of the window to the diameter of the window is 1:5.
  • the window has a thickness of less than lOmm.
  • the window may have a thickness of less than 5 mm.
  • the peripheral surface of the window may be inclined at an angle of between 1 degree and 10 degrees relative to a normal to the internal face.
  • the inclination may be at an angle greater or smaller than this range. In one embodiment, the angle of inclination is approximately 2 degrees.
  • the peripheral surface may be inclined at the same angle around its entire extent as this provides symmetry which can be desirable for applications where mechanical and thermal stresses are to be minimised where possible. In other applications which are less tightly constrained the angle of inclination is non-constant around the periphery.
  • the window is brazed to the wall using filler material.
  • the window is sealed to the wall by a joint formed using a solid- liquid interdiffusion (SLID) process.
  • SLID solid- liquid interdiffusion
  • layers of metallic materials having different melting points are brought into contact.
  • a re-melting temperature which is generally between the melting points of the initial materials. Bonds can thus be made at a low temperature and subsequently withstand higher temperature of use.
  • the window is sealed to the wall by a weld, which may be, for example, a laser weld.
  • the internal face of the window may be supported by a ledge or lip of the wall.
  • the chamber wall and the peripheral surface of the window may be substantially parallel to each other over the contact area between the window and the chamber wall.
  • the contact area may have a length of between 0.5 mm and 5 mm in a direction from the internal face to the external face. In one embodiment, the contact area has a length of approximately 1 mm.
  • the contact area between the window and the wall may be located in a region extensive over two thirds of the peripheral surface from the internal face towards the external face, and may be located in a region extensive over one third of the peripheral surface from the internal face towards the external face.
  • a portion is flexible to mitigate stress due to differential thermal expansion.
  • the chamber wall may include a window frame within which the window is positioned and the window frame is joined to a portion of the chamber wall. This is particularly advantageous where several windows are located within a vacuum chamber as it allows the vacuum seal of each window/frame subassembly to be tested prior to it being joined to the main part of the chamber wall.
  • the window frame or frames may comprise at least one of stainless steel, molybdenum, nickel copper alloy and mu-metal.
  • the chamber wall may comprise at least one of stainless steel, molybdenum, nickel copper alloy and mu-metal.
  • the vacuum chamber may be such that joint leakage via the vacuum seal is lower than or equal to 10 10 mbar litres per second.
  • the vacuum pressure within the chamber may be lower than or equal to 10 8 mbar.
  • a method of manufacturing a vacuum chamber includes the steps of:
  • an electromagnetic radiation transmissive window in an aperture in a wall of the vacuum chamber, the window having an external face external to the chamber and an internal face internal to the chamber, the external face having a larger area than the internal face, a peripheral surface of the window being inclined relative to the normal to the plane of the internal and external faces;
  • outward deformation which may be produced by stresses in the subassembly when the window is sealed to the wall is at least somewhat compensated by the deformation inwardly when the vacuum is produced.
  • This may provide a robust structure with good optical flatness, particularly if the deformation inwardly and deformation outwardly substantially match to provide net zero deformation.
  • the peripheral surface of the window may be substantially parallel to the surface of the wall with which it is in contact.
  • the step is included of, during the vacuum sealing step, heating the window and applying force to the window in a direction inwards towards the interior of the vacuum chamber.
  • the window may be being heated to a temperature in the range 200 to 300 degrees Celsius.
  • the chamber wall including a window frame having the aperture therethrough, and the steps are included of making a vacuum seal between the window and the window frame, testing the vacuum seal prior to the window frame being joined to a portion of the chamber wall and joining the window frame to the portion with a vacuum seal.
  • a window assembly for a vacuum chamber comprises: a window frame having an aperture therethrough and an
  • electromagnetic radiation transmissive window positioned in the aperture, the window having an external face external to the chamber when included therein and an internal face internal to the chamber, the external face having a larger area than the internal face, a peripheral surface of the window being inclined relative to the normal to the plane of the internal and external faces, with a vacuum seal between the window and the window frame wall at the inclined peripheral surface and the vacuum seal being extensive over less than or equal to two thirds of the dimension of the peripheral surface from the internal face to the external face.
  • Figure 1 schematically illustrates in cross-sectional view a magneto-optical trap apparatus including a vacuum chamber in accordance with the invention
  • FIG. 2 schematically illustrates part of another vacuum chamber in accordance with the invention
  • FIG. 3 schematically illustrates part of a vacuum chamber in accordance with the invention
  • FIG. 4 schematically illustrates part of a vacuum chamber in accordance with the invention
  • Figures 5a and 5b schematically illustrate plan and cross-sectional views respectively of a window and surrounding frame
  • Figures 6a, 6b and 5c schematically illustrate plan, cross-sectional and perspective views respectively of a window and its surrounding frame
  • FIGS. 7a, 7b and 7c schematically illustrate steps included in a method in accordance with the invention.
  • a magneto-optical trap (MOT) apparatus 1 includes a vacuum chamber 2 within which laser cooled atoms 3 are held during operation.
  • First and second windows 4 and 5 of N-ZK7 glass are positioned in opposite sides of the vacuum chamber 2 in respective apertures 6 and 7 through the wall 8 of the vacuum chamber.
  • the wall material is at least one of stainless steel, molybdenum, nickel copper alloy and mu-metal.
  • the windows 4 and 5 are joined to the surrounding wall 8 by hermetic seals.
  • Another suitable glass material is N-BK7 glass, also available from SCHOTT AG.
  • Other glasses may be used instead, for example, fused silica glass.
  • the windows 4 and 5 are transmissive to electromagnetic radiation and allow laser light to be introduced into the chamber 2 during operation. Reflective surfaces 9 within the vacuum chamber 2 direct laser radiation to a region where cold atoms are held during operation.
  • the MOT 1 also includes an atomic source 10, which in this embodiment is a source of rubidium atoms, arranged to dispense rubidium atoms into the vacuum chamber.
  • a pump tube 11 is extensive through the chamber wall 2 to give a connection to an external vacuum pump (not shown) to produce a vacuum within the vacuum chamber 2.
  • the vacuum required is dependent on the purpose of the vacuum chamber. For example, for an MOT holding cold atoms, a suitable vacuum may be lower than or equal to 10 8 mbar.
  • a single laser may be used and reflective surfaces arranged within and/or external to the vacuum chamber 2 such that the laser output light makes several passes through the chamber 2.
  • two or more lasers are used. In an initial operating mode, the laser or lasers are directed to reduce the kinetic energy of atoms in the central region of the vacuum chamber 2 and hence cool them. In subsequent operating modes, laser radiation is used to produce a quantum effect and then monitor the quantum effect.
  • the windows 4 and 5 are nominally identical and sealed in the same manner.
  • the first window 4 is circular in plan view and has an external face 12 which is of larger surface area than its internal face 13 and is substantially parallel thereto.
  • the peripheral surface 14 of the window 4 is inclined at an angle of about 2 degrees relative to the normal to the planes of the external face 12 and internal face 13. It should be noted that the taper is exaggerated in the drawings for the purposes of clarity.
  • the ratio of the thickness of the window 4 to the diameter of the window 4 is between approximately 1:3 and 1:8 and in this embodiment is approximately 1:5.
  • the thickness of the window 4 is less than lOmm.
  • the chamber wall 8 surrounding the window 4 includes a cylindrical portion 15 having an inner surface portion 16 which is inclined at substantially the same angle as the peripheral surface 14 of the window 4 such that the two surfaces are substantially parallel.
  • the window 4 is sealed to the surrounding inner surface portion 16 using a solid-liquid interdiffusion (SLID) process using gold and tin to form the bond.
  • the vacuum seal is made by brazing using filler material or by some other suitable process such as laser welding.
  • the contact area between the window 4 and the inner surface portion 16 of the wall 8 is located in a region which is extensive over two thirds of the peripheral surface 14 from the internal face 13 towards the external face 12.
  • the contact area has a length of approximately 1 mm in this embodiment, illustrated by arrow“a”.
  • Figure 2 illustrates part of another embodiment showing the configuration of a tapered window 17 similar to that shown in the embodiment of Figure 1 and a portion of a vacuum chamber wall 18 to which it is sealed.
  • the stainless steel wall 18 includes a circular inwardly-projecting portion 19 of molybdenum.
  • the circular portion 19 has an inclined surface 20 which is hermetically sealed to the periphery of the window 17.
  • Figure 3 illustrates part of another embodiment.
  • an inwardly projecting ring 21 includes sections 2la, 2lb and 2lc at different angles and is of a thickness and material which allows movement with, for example, thermal changes, to reduce stresses that might otherwise occur during manufacturing and/or operating processes.
  • a window 22 is sealed to a section 2la of the ring 21.
  • a suitable material for ring 21 is molybdenum.
  • the wall 23 of the vacuum chamber may be of stainless steel.
  • Figure 4 illustrates part of another embodiment showing the configuration of a tapered window 24 similar to that shown in the embodiment of Figure 1 and a portion of a vacuum chamber wall 25 to which it is sealed.
  • An inwardly projecting ring 26 is angled downwardly as shown.
  • a tapered window 27 is hermetically sealed to a window frame 28.
  • the peripheral surface 29 of the window 27 is inclined and is bonded to an inclined surface of the window frame 28 which is substantially parallel to the peripheral surface 29 to give a vacuum seal. After sealing, the join between the window 27 and frame 28 is tested. If satisfactory, the frame and window subassembly is then joined to the remainder of the vacuum chamber wall by welding or some other suitable technique.
  • Figures 6a, 6b and 6c illustrate a window frame and a tapered window having a different configuration.
  • a method in accordance with the invention includes positioning an electromagnetic radiation transmissive window 30 in an aperture in a wall 31 of a vacuum chamber 32, the window 30 having an external face 33 external to the chamber and an internal face 34 internal to the chamber 32.
  • the external face has a larger area than the internal face.
  • a peripheral surface 35 of the window 30 is inclined relative to the normal to the plane of the internal and external faces 33 and 34.
  • a vacuum seal 36 is then made between the peripheral surface 35 of the window 30 and the wall 31.
  • the vacuum seal is made using a solid-liquid interdiffusion (SLID) process with gold and tin to form the vacuum seal.
  • the window is heated to a temperature in the range 200 to 300 degrees Celsius. Force is applied to the window in a direction substantially normal to the internal face and external face of the window and in a downward direction.
  • SID solid-liquid interdiffusion
  • the window 30 When the sealing step is complete and the window 30 is sealed in position, the window 30 has a deformation in a direction outwardly from the interior of the chamber as shown by arrow“a”. The deformation occurs because stresses are produced as the wall 31 recovers from the heat used in sealing process and because of the configurations of the wall 31 and of the window 30.
  • a vacuum is then produced within the chamber as shown in Figure 7b, resulting in the sealed window 30 becoming deformed in an inward direction towards to interior of the chamber, as shown by arrow“b”.
  • the amount of deformation in the inward and outward directions is such that they substantially cancel out one another to provide a window with good optical flatness.
  • the window flatness may be better than or equal to 40 nm over the central 90% of the window.
  • the chamber wall may include a window frame having the aperture

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Gasket Seals (AREA)
  • Stabilization Of Oscillater, Synchronisation, Frequency Synthesizers (AREA)

Abstract

L'invention concerne une chambre à vide comprenant une paroi de chambre à vide (2) traversée par une ouverture (6) et une fenêtre de transmission de rayonnement électromagnétique (4) positionnée dans l'ouverture. La fenêtre (4) a une face externe (12), externe à la chambre et une face interne (13), interne à la chambre, la face externe (12) et la face interne (13) étant sensiblement parallèles et la face externe ayant une surface plus grande que la face interne. Une surface périphérique (14) de la fenêtre est inclinée par rapport à la perpendiculaire au plan des faces interne et externe, avec un joint à vide entre la fenêtre et la paroi au niveau de la surface périphérique (14) inclinée.
PCT/GB2018/053750 2017-12-21 2018-12-21 Chambre à vide, pièces associées et procédé de fabrication associé WO2019122924A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP18829959.8A EP3729205A1 (fr) 2017-12-21 2018-12-21 Chambre à vide, pièces associées et procédé de fabrication associé

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB1721557.5A GB2570441B (en) 2017-12-21 2017-12-21 Vacuum chamber, parts therefor and method for manufacturing the same
GB1721557.5 2017-12-21

Publications (1)

Publication Number Publication Date
WO2019122924A1 true WO2019122924A1 (fr) 2019-06-27

Family

ID=61131670

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB2018/053750 WO2019122924A1 (fr) 2017-12-21 2018-12-21 Chambre à vide, pièces associées et procédé de fabrication associé

Country Status (3)

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EP (1) EP3729205A1 (fr)
GB (1) GB2570441B (fr)
WO (1) WO2019122924A1 (fr)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005011450A2 (fr) * 2003-07-31 2005-02-10 Mattson Technology, Inc. Agencement de fenetre
JP2010103483A (ja) * 2008-08-11 2010-05-06 Honeywell Internatl Inc 冷却原子一次周波数標準器のための物理パッケージ
EP2829925A2 (fr) * 2013-07-22 2015-01-28 Honeywell International Inc. Emballage physique de capteur atomique à panneaux et coins externes optiquement transparents

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1328791A (en) * 1969-05-05 1973-09-05 Secr Defence Windows for pressure vessels
FR2619186B1 (fr) * 1987-08-03 1989-12-01 Grandjean Daniel Perfectionnements aux hublots d'observation etanches, pour enceintes sous vide, et a leurs procedes de fabrication
DE8811508U1 (de) * 1988-09-12 1988-11-10 Leybold AG, 6450 Hanau Schauglas für Vakuumapparaturen
ATE432482T1 (de) * 2000-02-18 2009-06-15 Drukker Internat B V Fenster
JP2005329330A (ja) * 2004-05-20 2005-12-02 Yokogawa Electric Corp 高温・高圧用容器用窓の構造

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005011450A2 (fr) * 2003-07-31 2005-02-10 Mattson Technology, Inc. Agencement de fenetre
JP2010103483A (ja) * 2008-08-11 2010-05-06 Honeywell Internatl Inc 冷却原子一次周波数標準器のための物理パッケージ
EP2829925A2 (fr) * 2013-07-22 2015-01-28 Honeywell International Inc. Emballage physique de capteur atomique à panneaux et coins externes optiquement transparents

Also Published As

Publication number Publication date
EP3729205A1 (fr) 2020-10-28
GB201721557D0 (en) 2018-02-07
GB2570441A (en) 2019-07-31
GB2570441B (en) 2022-03-09

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