Magnetron sputtering of Superconducting Multilayer Nb3Sn Thin Film

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stoichiometric composition is metastable at room temperature and is only stable at1940°C. The aluminium content of the A15 phase decreases with decreasingtemperature; the homogeneity range at 1000°C is 19~22 at.% Al.Nb 3 GeThe most striking feature of Nb 3 Ge phase field is that the stoichiometriccomposition is not included at equilibrium, the highest solubility of Germaniumbeing 23 at.%. At 1000°C, the homogeneity range of the A15 phase is very narrowand is centered at 18 at.% with total width of 1 at.%. It has not been possible torise T C above 17~18 K in bulk sample either by quenching or other means.Metastable stoichiometric, or near stoichiometric, Nb 3 Ge can be prepared as thinfilms with critical temperature of 23 K. But the big problem is that the material isvery brittle, which meaning is that a strike or vibration can change the A15structure and cease the superconductor.Nb 3 SnNb 3 Sn is the only A15 material that has given promising results when appliedto the construction of a real cavity [19] : Tin was reactively diffused into an Nb bulkcavity and the Q-factor was in the order of 10 11 , the accelerating field beinglimited to about 12 MV/m.Fig.1.7The Niobium-Tin phase diagramAccording the phase diagram of Fig. 1.7, the A15 phase is unstable below14
775°C. From the same diagram, it is seen that several spurious phases are alsopossible, and this can represent a limitation for the fabrication of superconductingcavities. Besides T C , however for Nb-Sn system there is another quantityundergoing a much stronger variation in the narrow composition range between24.5 at. % and 25 at.% Sn: the resistivity in normal state just before transition.Resistivity indeed changes from 20 μΩ cm at 24.4 at. % tin to less than 4 μΩcm at25 at.% tin; this sharp change being a direct consequence of the perfectly orderedstate of Nb 3 Sn. This consideration is absolutely critical: for everybody wishing tocarry on further investigation on Nb 3 Sn, it is mandatory to look for low resistivity.The parameters comparison between Nb and Nb 3 Sn are shown in Table 1.4 [1] .Table 1.4 the parameters of Nb 3 Sn and NbFig 1.8 the crystal structure of MgB 2Another important new superconductivity material is the magnesium diboride15
Page 1: UNIVERSITÀ DEGLISTUDI DI PADOVAFac
Page 7 and 8: IndexINDEX ........................
Page 9 and 10: IntroductionThe superconductor acce
Page 11 and 12: Fig. 1.1 Disc-loaded traveling-wave
Page 13 and 14: In Type-II superconductors, vortex
Page 15 and 16: needed for preventing the supercond
Page 17 and 18: The B1 crystal structure has a cubi
Page 19 and 20: NbN cavities literature, is often h
Page 21: superconducting magnet construction
Page 25 and 26: two types of electrons at the Fermi
Page 27 and 28: Of course, there are some other kin
Page 29 and 30: as shown in Fig.2.3. The four opera
Page 31 and 32: Fig.2.8 turbomolecular pumpFig. 2.9
Page 33 and 34: Fig. 2.14 The chamber covered with
Page 35 and 36: Fig. 2.17 the gasket and the magnet
Page 37 and 38: shown in Fig. 2.21 and Fig. 2.22. T
Page 39 and 40: Fig. 2.26 The interface of the surf
Page 41 and 42: Fig. 2.30 put the sample into the T
Page 43 and 44: Fig. 2.34 the performance of the th
Page 45 and 46: 1008038.5°{110}69.6°{211}sample1s
Page 47 and 48: 2dsinθ= nλ (2.3)Fig.2.44 the diff
Page 49 and 50: Chapter 3 Multilayer deposition of
Page 51 and 52: 1 minute. The time of depositing mu
Page 53 and 54: chamber 1 and is connected to the s
Page 55 and 56: 3.2.2.2 Analysis resultⅠ The thic
Page 57 and 58: In order to detect the component of
Page 59 and 60: measure the RRR. So the resistance
Page 61 and 62: 110100903480relative Intensity70605
Page 63 and 64: frequency of the cavity which is in
Page 65 and 66: Fig. 3.28 the inductor coilDuring t
Page 67 and 68: Fig. 3.32 fixing the sample with Nb
Page 69 and 70: second transition temperature is th
Page 71 and 72: source is the bulk Nb sample. Altho
Page 73 and 74:
of 1A in the Fig. 3.37 and Fig. 3.4
Page 75 and 76:
Table 3.10 the description of the p
Page 77 and 78:
1101001.0A10'-IND3 45 6 7 9 1011 12
Page 79 and 80:
1101009080341.8A10'INDrelative inte
Page 81 and 82:
Reference1. A. Godeke, Nb3Sn FOR RA
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Magnetron sputtering of Superconducting Multilayer Nb3Sn Thin Film

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