US3845424A - Superconducting cavity resonator - Google Patents

Superconducting cavity resonator Download PDF

Info

Publication number
US3845424A
US3845424A US00313998A US31399872A US3845424A US 3845424 A US3845424 A US 3845424A US 00313998 A US00313998 A US 00313998A US 31399872 A US31399872 A US 31399872A US 3845424 A US3845424 A US 3845424A
Authority
US
United States
Prior art keywords
resonator
cavity
lines
resonator cavity
superconducting
Prior art date
Legal status (The legal status 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 status listed.)
Expired - Lifetime
Application number
US00313998A
Other languages
English (en)
Inventor
H Martens
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Siemens AG
Siemens Corp
Original Assignee
Siemens Corp
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 Siemens Corp filed Critical Siemens Corp
Application granted granted Critical
Publication of US3845424A publication Critical patent/US3845424A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P7/00—Resonators of the waveguide type
    • H01P7/02—Lecher resonators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P7/00—Resonators of the waveguide type
    • H01P7/06—Cavity resonators
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S505/00—Superconductor technology: apparatus, material, process
    • Y10S505/825—Apparatus per se, device per se, or process of making or operating same
    • Y10S505/866—Wave transmission line, network, waveguide, or microwave storage device

Definitions

  • ABSTRACT In a superconducting cavity resonator, the need to separate the input and output coupling lines from the resonator cavity by the use of vacuumtight microwave windows is avoided by instead having the tubular line(s) for coupling electromagnetic energy into and out of the cavity open into the resonator cavity from below the cavity.
  • the invention concerns a superconducting cavity resonator with at least one tubular line, for coupling electromagnetic energy in and out of the cavity, which opens into the resonator cavity without vacuumtight separation.
  • Superconducting cavity resonators which either consist completely of superconductive material or have a superconducting surface bounding the resonator cavity, are particularly well suited as resonators and as separators for particle accelerators. Such resonators also have other applications, for instance, as frequency standards. Niobium is usually preferred as the superconductive material for cavity resonators, but other superconductive materials, particularly lead, can also be used. 1
  • tubular lines for instance, one or several tubular lines, for instance,
  • the condition of the surface layer in which these ac currents flow is of great importance.
  • the surface resistance and therefore the quality factor Q of the resonator, as well as the critical magnetic field H, measured under the action of alternating fields depend substantially on the condition of the surface.
  • a high critical magnetic field is important so that the cavity resonator can be operated with highfrequency power as high as possible with at the same time, high Q. If the critical magnetic field is exceeded, the ac losses increase steeply and the quality Q of the resonator decreases considerably.
  • the cavity resonators In order to achieve a high Q and a high critical magnetic field H on the one hand the cavity resonators should be initially manufactured with surfaces already as smooth and free of contamination as possible and on the other hand, provision should be made during the operation of the cavity resonators so that the surface properties do not deteriorate.
  • For smoothing and purifying the surfaces during manufacture chemical and electrochemical polishing methods are used, and in the case of niobium surfaces, annealing methods are also used. When annealing is used, in addition to a purification of the niobium surface by outgassing, a grain growth of the niobium also occurs so that the number of grain boundaries at the niobium surface is decreased.
  • ln niobium cavity resonators particularly high Q and critical magnetic fields can be achieved by providing the surface bounding the resonator cavity with a niobium oxide layer through anodic oxidation. Through the oxidation of the surface, the resonatorsurface effective for superconduction is relocated away from the surface proper into a lower and purer niobium layer. At the same time, the niobium oxide layer serves as a protective layer for this deeper-located effective surface as described in Physics Letters, vol. 34A, 1971, p.439 to 440.
  • the superconducting cavity resonator must be cooled to low temperatures.
  • the resonator is arranged in the helium tank of a cryostat. By pumping off the helium vapor above the liquid helium present in the helium tank, temperatures down to 1.2 K can be obtained.
  • the tubular lines for coupling the electromagnetic energy in and out of the resonator cavity were introduced from above into the coolingmedium vessel of the cryostat and also open into the resonator cavity from above.
  • these lines opened directly into the resonator cavity and were not separated from the resonator cavity in a vacuumtight manner, i.e., the entire interior of the lines formed a common gas space with the resonator cavity, so that the lines could be utilized at the same time for evacuating the resonator cavity as described in Journal of Applied Physics, vol. 39 (l969), p.2606 to 2609 and 44l7 to 4427.
  • the soution according to the present invention is based on the surprising discovery that, contrary to previous understanding and belief, contamination due to cryo-pumping action has only a relatively small influence on the Q of the superconducting cavity resonators.
  • a much stronger detrimental effect is that of small dirt and dust particles, which in spite of the most careful cleaning procedures remain in the tubular feed lines to the resonator cavity and, in the case of feed lines opening into the resonator cavity from above, drop into the resonator cavity and carbonize in the strong microwave field prevailing there.
  • Such dirt particles can drop into the resonator cavity even if it is closed off vacuumtight by a microwave window, since they can drop off from this microwave window itself or from the parts located between the microwave window and the resonator cavity proper.
  • the tubular line by arranging the tubular line, to open into the resonator cavity from below, any dropping of dust or dirt particles into the resonator cavity is avoided without the need for a vacuum-wise separation of the resonator cavity from the parts of the tubular line which are at a higher temperature.
  • the line can therefore serve at the same time as a pump line for evacuating the resonator cavity.
  • An opening of the line or lines from below is understood here to mean that the line rises before opening into the resonator cavity.
  • the last section of the line before opening into the resonator cavity should run at an angle against the horizontal or vertically from below, so that the parts of the line adjacent to the opening of the line are at a lower level than the opening itself.
  • the line coming from below can also open into a laterally situated part of the wall of the resonator. However, it is preferable to let the line open into the resonator cavity at the bottom side of the resonator.
  • tubular lines opening into the resonator cavity for coupling electromagnetic energy in and out
  • all lines open into the resonator cavity from below, so that in no case can dirt or dust particles drop into the resonator cavity from above.
  • tubular lines which do not serve for coupling electromagnetic energy in and out but serve exclusively as pump lines for evacuating the resonator cavity, should preferably open into the resonator cavity from below.
  • Such additional pump lines may be of advantage particularly in resonators with large physical dimensions.
  • the lines brought through the bottom of the cryostat in which the cavity resonator is situated may open into the resonator cavity coming from below in a straightline.
  • the line or lines may form a bend. Since gas molecules that may come from the end of the line which is at a higher temperature cannot traverse in a straight line, such a bend forms a cooling trap for gases entering through the line and thereby additionally prevents the contamination of the resonator surface due to the already mentioned cryo-pumping effect.
  • the bend of the line or lines which serves as a cooling trap, is situated lower in the coolant vessel than the'lowest point of the resonator cavity.
  • the bend in the line is cooled down first'so that residual gases that may be present in the resonator cavity are drawn off from the resonator cavity into the bend through the cryo pumping effect of thebend.
  • the line or lines has a bend the line can be introduced into the cryostat from above the cryostat and still achieve the advantages of the present invention since the portion of the line entering the resonator cavity will still be entering from below the cavity.
  • the opening of the lines into the resonator cavity from below has advantages not only in the case of cavity resonators with bare, superconductive surfaces, but also in the case of a niobium cavity resonator, the surface of which is anodically oxidized since even in the case of a surface protected in this manner, dirt and dust particles dropping into the resonator cavity have a detrimental effect on the electric properties of the resonator.
  • FIG. 1 shows schematically, in cross section, a cavity resonator of the TE type arranged in the coolant vessel of a cryostat with coupling lines entering from below;
  • FIG. 2 shows a different cross section through the cavity resonator according to FIG. 1;
  • FIG. 3 shows schematically, in a longitudinal cross section, part of a separator structure of the HEM, type with a coupling line entering from below.
  • the cavity resonator of the TE type shown in FIGS. 1 and 2 is operated at X-band, i.e., in the range of about 8 to 12 GHz.
  • the longitudinal cross section shown in FIG. 2 is perpendicular to the longitudinal cross section shown in FIG. 1.
  • the cavity resonator consists of a cupshaped resonator part 1 with a resonator cavity 2 in the form of a circular cylinder and is closed downward by a coupling member 3.
  • a disc-shaped flange 4 At the bottom of the coupling member 3 is attached a disc-shaped flange 4, into which two rectangular waveguides 5 and 6 which serve as the coupling lines are soldered or welded.
  • the coupling stubs 7 and 8 which continue the lines 5 and 6 toward the resonator cavity 2.
  • indium ring seals 11 and 12 are provided between the resonator part 1, the coupling member 3 and the flange 4.
  • the overall resonator is located in the helium vessel 13 of a conventional cryostat, which can be filled with liquid helium 14.
  • the parts of the cryostat which serve for thermal insulation and surround the helium vessel, such as vacuum spaces and a radiation shield, are not shown in FIG. 1.
  • the tubular lines 5 and 6 form a bend 15 within the helium vessel 13 and are brought out of the cryostat upward through the cover 16 of the cryostat.
  • a pump connection 17 for pumping off the helium vapor is provided in the cryostat cover.
  • the lines 5 and 6 may be connected at their end 18, which is at room temperature, with a suitable microwave source, for instance, a klystron.
  • a branch 19 which is suitably arranged, i.e., so that it does not interfere with the propagation of the microwaves, which can be connected with a vacuum pump.
  • the bend I5 is situated in the coolant tank at a lower level than the lowest point of the resonator cavity and serves as a cooling trap for gas molecules that may enter from the ends 18 and 19 of the lines 5 and 6.
  • the lines 5 and 6 and the resonator cavity 2 are already evacuated via the con-' nection 19 prior to immersion of the resonator into the helium bath 14. If the resonator is immersed into the helium bath, or after insertion of the resonator into the helium vessel 13, the latter is filled with helium, the bend 15 is the first part of the whole arrangement cooled to a low temperature.
  • the parts 1, 3 and 4 consist of solid niobium.
  • the resonator cavity 2 has an inside height and an inside diameter of 4l mm; the coupling apertures 9 and 10 have a diameter of 1.5 mm each.
  • the coupling stubs 7 and 8 each are 40 mm long and have a rectangular cross section of about 10 X 23 mm
  • niobium surfaces bounding the resonator cavity 2 are smoothed first mechanically and subsequently further by chemical or electrochemical polishing methods and are finally provided with a protective niobium oxide layer of between about 0.1 and l um thickness by anodic oxidation. All other parts of the resonator as well as the waveguides 5 and 6 were very carefully cleaned.
  • a resonator treated in this manner was first inserted into the helium vessel 13 of the cryostat with feed lines 5 and 6 opening into the resonator from above, i.e., upside down from the illustration in FIG. 1, the feed lines 5 and 6 being brought out in a straight line without a bend through the cryostat cover 16.
  • an unloaded Q of about 2 10 with a critical magnetic field of about 50 milliteslas was measured at a temperature of about 1.5 K and a microwave frequency of 9.5 GHz.
  • carbonized dirt particles were found at the underside of the resonator cavity underneath the coupling holes.
  • FIG. 3 shows a section of a particle separator for particle accelerators of the HEM type in a lengthwise cross section.
  • the resonator wall 32 which encloses the resonator cavity 31 and consists, for instance. of niobium is of rotational symmetry with respect to the longitudinal axis 33, so that the cross section of the resonator cavity is always circular.
  • a tubular line 35 for coupling in the microwave energy opens into the resonator cavity 31 from below via a coupling hole 34.
  • the line 35 may, for instance, be a rectangular waveguide, but it can also be designed as a coaxial line and have an additional inner conductor 36.
  • the resonator according to FIG. 3 is arranged in a cryostat with horizontal longitudinal axis.
  • the line 35 can then be bent similarly as the line 5 shown in FIG. 1 and be brought out of the cryostat at the top.
  • Another possibility consists, as already mentioned, of feeding the line from below through the bottom of the cryostat.
  • the examples of embodiments shown in the figures can be modified in many ways.
  • the line 5 in FIG. 1 can, for instance, have also several bends. However, it is always essential that the line opens into the resonator cavity from below.
  • a superconducting cavity resonator with one or more tubular lines for coupling electromagnetic energy in and out of the resonator with a coolant vessel surrounding said superconducting cavity resonator wherein the invention comprises tubular lines for coupling having a bend prior to opening into said resonator cavity, with said lines opening into said cavity from below and said bend situated in the coolant vessel lower than the lowest point of the resonator cavity and ing into the resonator from below, said pumping lines having a bend before opening into said cavity. which bend is disposed lower in the coolant vessel than the lowest point of the resonator cavity, to thereby serve as a cooling trap for the gaseous molecules entering through the pumping line.

Landscapes

  • Particle Accelerators (AREA)
  • Control Of Motors That Do Not Use Commutators (AREA)
  • Superconductor Devices And Manufacturing Methods Thereof (AREA)
US00313998A 1971-12-24 1972-12-11 Superconducting cavity resonator Expired - Lifetime US3845424A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE2164529A DE2164529C2 (de) 1971-12-24 1971-12-24 Supraleitender Hohlraumresonator

Publications (1)

Publication Number Publication Date
US3845424A true US3845424A (en) 1974-10-29

Family

ID=5829189

Family Applications (1)

Application Number Title Priority Date Filing Date
US00313998A Expired - Lifetime US3845424A (en) 1971-12-24 1972-12-11 Superconducting cavity resonator

Country Status (6)

Country Link
US (1) US3845424A (enExample)
JP (1) JPS4874797A (enExample)
CA (1) CA954598A (enExample)
DE (1) DE2164529C2 (enExample)
FR (1) FR2164918B1 (enExample)
GB (1) GB1412959A (enExample)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
USD247432S (en) 1977-02-28 1978-03-07 The United States Of America As Represented By The Field Operations Bureau Of The Federal Communications Commission Fine and coarse tuning assembly for cavities
US4227153A (en) * 1978-07-26 1980-10-07 The United States Of America As Represented By The Secretary Of The Navy Pulse generator utilizing superconducting apparatus
US5052183A (en) * 1991-01-04 1991-10-01 The United States Of America As Represented By The Secretary Of The Army Open cryogenic microwave test chamber
US6212404B1 (en) * 1997-08-01 2001-04-03 K&L Microwave Inc. Cryogenic filters

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS59807Y2 (ja) * 1975-07-30 1984-01-11 株式会社東芝 クウドウキヨウシンキ
DE3901554A1 (de) * 1989-01-20 1990-08-02 Dornier Luftfahrt Direktgekuehlte supraleitende cavity

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3348135A (en) * 1964-06-03 1967-10-17 David W Howgate Method and apparatus for analysis of gaseous discharge products from flames by electron-paramagnetic resonance
US3748421A (en) * 1971-07-29 1973-07-24 Raytheon Co Microwave melter apparatus

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3348135A (en) * 1964-06-03 1967-10-17 David W Howgate Method and apparatus for analysis of gaseous discharge products from flames by electron-paramagnetic resonance
US3748421A (en) * 1971-07-29 1973-07-24 Raytheon Co Microwave melter apparatus

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
Schwettman et al., The Application of Superconductivity To Electron Linear Accelerators, International Advances in Cryogenic Eng., Proc. of the 1964 Cryogenic Eng. Conf. TP480A3(V10Pt2) 1964, pp. 88, 92. *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
USD247432S (en) 1977-02-28 1978-03-07 The United States Of America As Represented By The Field Operations Bureau Of The Federal Communications Commission Fine and coarse tuning assembly for cavities
US4227153A (en) * 1978-07-26 1980-10-07 The United States Of America As Represented By The Secretary Of The Navy Pulse generator utilizing superconducting apparatus
US5052183A (en) * 1991-01-04 1991-10-01 The United States Of America As Represented By The Secretary Of The Army Open cryogenic microwave test chamber
US6212404B1 (en) * 1997-08-01 2001-04-03 K&L Microwave Inc. Cryogenic filters

Also Published As

Publication number Publication date
DE2164529B1 (de) 1973-06-14
DE2164529C2 (de) 1974-01-10
FR2164918B1 (enExample) 1978-02-10
FR2164918A1 (enExample) 1973-08-03
GB1412959A (en) 1975-11-05
JPS4874797A (enExample) 1973-10-08
CA954598A (en) 1974-09-10

Similar Documents

Publication Publication Date Title
Aune et al. Superconducting TESLA cavities
US2725474A (en) Oscillation circuit with superconductor
US8674630B1 (en) On-axis RF coupler and HOM damper for superconducting accelerator cavities
AU684463B2 (en) Microwave resonator
US2994009A (en) High frequency tube apparatus
US3784452A (en) Method of treating the surface of superconducting niobium cavity resonators
Graber et al. Reduction of field emission in superconducting cavities with high power pulsed RF
Padamsee A new purification technique for improving the thermal conductivity of superconducting Nb microwave cavities
US2880357A (en) Electron cavity resonator tube apparatus
Dhakal et al. Design and performance of a new induction furnace for heat treatment of superconducting radiofrequency niobium cavities
US4081573A (en) Method for preparing superconductive Nb3 Sn layers on niobium surfaces for high-frequency applications
Hillenbrand et al. Superconducting Nb3Sn cavities with high quality factors and high critical flux densities
Martens Superconducting cavity resonator
US3493809A (en) Ultra high q superconductive cavity resonator made of niobium having a limited number of crystal grains
CN108432350B (zh) 加速腔以及加速器
US3441880A (en) High q radio frequency circuit employing a superconductive layer on a porous thermally matched substrate
DE2164529C2 (de) Supraleitender Hohlraumresonator
Diepers et al. Superconducting niobium TE011 mode cavities with high critical magnetic field and high Q value
US3441881A (en) High q radio frequency circuits employing a superconductive layer on a thermally matched aggregate metallic substrate
Lorkiewicz et al. Surface tin coating of tesla couplers at desy as an antimultipactor remedy
DE69025128T2 (de) Magnetrone
Zapfe-Duren et al. A new flange design for the superconducting cavities for TESLA
US3297906A (en) High frequency electron discharge device of the traveling wave type having an interconnected cell slow wave circuit with improved slot coupling
Doderer et al. Liquid helium cooled sample stage for the investigation of microwave irradiated samples by scanning electron microscopy
US3210593A (en) Method and apparatus for the broadbanding of power type velocity modulation electron discharge devices by interaction gap spacing