Magnetron sputtering of Superconducting Multilayer Nb3Sn Thin Film

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In order to compare the R BCS of different material, the nomogram [8,27] of Fig.1.10 can be constructed for materials at 4.2 K, 500 MHz and a strong coupling factorof 4. Chosen a certain value of R BCS , on the corresponding curve there are all thematerials with different T C and ρ n having the same R BCS . Among the materialdescribed in Fig. 1.10, the ρ 0 of V 3 Si and Nb 3 Sn is the most small. Although the T c ofMgB 2 is higher than that of V 3 Si and Nb 3 Sn, its R BCS is the same order of that of V 3 Siand Nb 3 Sn because of the 2.3 meV energy gap of π bonding at 4.2K [28] . So, amongthese three kinds of material, Nb 3 Sn is the most stable and easy to obtain.The last problem is that why we used the thin film for the superconductor cavity.The first reason is that it is possible to use different substrates, which can improve thethermal stability and the mechanical stability. For example, the thermal conductivityand mechanical performance can be improved by the Cu substrate. The second reasonis to reduce the manufacture cost and the consuming of the superconductivity material.The third reason is to improve the performance of the superconductor, such as the T c ,RRR, Q value, H c and so on. For example, the performance of the MgB 2 thin film isbetter than that of the bulk of Nb most. But this is not always effective. For example,the Q value of the thin film Nb cavity is higher than that of bulk Nb cavity at lowaccelerator field, but it is always reversed at high field [29] .In other words, the thin film cavity always has a higher Q-slope, especially forinnovative superconductors. However, some kinds of superconductivity material cannot be used to shape the cavity by the bulk material because the material is brittle andthe distortion can change the crystal lattice to change the superconductivityperformance, such as Nb 3 Sn, MgB 2 , and so on.Fig.1.11 the Q 0 of Nb18
Of course, there are some other kinds of superconductor, such as organicsuperconductor, molecular superconductor and high temperature superconductor. TheRRR of organic superconductor is lower, so it is not proper to be used for theaccelerator cavity because of higher R BCS . The thin film of the molecularsuperconductor is some difficult to be obtained. The critical H and the critical currentof the high temperature superconductor are somewhat lower than that of acceleratorcavity needed.In the conclusion, the Nb 3 Sn thin film is very important for the superconductorcavity. There are two methods to manufacture the Nb 3 Sn thin film: the diffusionmethod and multilayer deposition method. In this thesis, we focus on the multilayerdeposition method.Fig.1.12 the different kinds of supercondoctor19
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 and 22: superconducting magnet construction
Page 23 and 24: 775°C. From the same diagram, it i
Page 25: two types of electrons at the Fermi
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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