Multipactor in Low Pressure Gas and in ... - of Richard Udiljak

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Voltage [V] 10 4 10 3 10 2 10 0 N=1 N=3 N=5 N=9 N=7 10 1 Frequency − Gap product [GHz⋅mm] Figure 2.3: Multipactor susceptibility chart based on the constant initial velocity approach. Parameters used are: W0 = 3.68 eV, W1 = 23 eV, W2 = 1000 eV, and Nmax = 9. 12
who produced charts of this type [30]. Characteristic for the Hatch and Williams charts are that the multipactor zones are wider than the Sombrin charts for increasing voltage. This occurs since a constant vimpact/v0 implies that v0 increases as the impact velocity increases. When e.g. Wimpact = 3000 eV, this means that for k = 2.5 the initial energy W0 = 480 eV, clearly an unrealistic initial velocity. Voltage amplitude [V] 10 4 10 3 10 2 10 0 N=1 N=3 N=5 N=9 N=7 10 1 Frequency − Gap product [GHz⋅mm] Figure 2.4: Multipactor susceptibility chart produced with the constant k assumption. Parameters used are: k = 2.5 (corresponding to an initial W0 = 3.68 eV when Wimpact = W1), W1 = 23 eV, W2 = 1000 eV, and Nmax = 9. By knowing the secondary electron emission characteristics of a material as given by the parameters W1, W2, and W0 or k, multipactor charts for that material can be designed. However, Woode and Petit [31] performed a large series of multipactor experiments during the 1980’s and used the Hatch and Williams charts to fit the experimental data. By tuning the k and W1 parameters for each zone, they were able to produce multipactor charts that fit the experimental data quite well (cf. Fig. 2.5). The problem with this empirical approach is that it has to assume different values for the first cross-over point for each zone in order to obtain good fitting. This is clearly an unphysical approach and will not contribute to an improved understanding of the phenomenon, 13
Page 1 and 2: Thesis for the degree of Doctor of
Page 3: Multipactor in Low Pressure Gas and
Page 6 and 7: Conference contributions by the aut
Page 8 and 9: viii
Page 10 and 11: 3.2.4 Key findings . . . . . . . .
Page 12 and 13: xii
Page 14 and 15: xiv
Page 16 and 17: addition, it is difficult to make c
Page 18 and 19: numerical study of the phenomenon i
Page 20 and 21: to physically damage microwave comp
Page 22 and 23: odd positive integer (N = 1,3,5...)
Page 24 and 25: σ se [−] 2.5 2 1.5 1 0.5 W 1 W m
Page 28 and 29: even though it may be sufficient fr
Page 30 and 31: where φL and φR are the left and
Page 32 and 33: (cf. Fig. 2.7). When taking the env
Page 34 and 35: 2.1.4 Methods of suppression Many o
Page 36 and 37: Noise (dBm) Power #1 (dBm) Match #1
Page 38 and 39: andom spread in emission velocities
Page 40 and 41: Figure 2.12: Multipactor experiment
Page 42 and 43: where kn is a factor determining th
Page 44 and 45: allows for another design margin, w
Page 46 and 47: Boundary function Method One of the
Page 48 and 49: carriers, because the NLSQ method r
Page 50 and 51: multipactor discharge. Using a Mont
Page 52 and 53: the assumption of a constant ratio
Page 54 and 55: Voltage (V) 10 3 10 2 10 1 10 −2
Page 56 and 57: 3.1.3 Main results The main result
Page 58 and 59: lytical model is obviously needed.
Page 60 and 61: where 〈vt 2 〉 represents the av
Page 62 and 63: these quantities in the range from
Page 64 and 65: analytical. Attempts were made to f
Page 66 and 67: only model, the inclusion of ionisa
Page 68 and 69: Normalised Voltage 1.1 1.05 1 0.95
Page 70 and 71: Voltage [V] 10 3 10 0 µ=0 µ=0.75
Page 73 and 74: Chapter 4 Multipactor in irises A c
Page 75 and 76: h l Figure 4.1: The geometry used i
Page 77 and 78:
N e /N 0 [−] 3 2.5 2 1.5 1 Multip
Page 79 and 80:
to compensate for electron losses i
Page 81:
4.4 Main results This analysis has
Page 84 and 85:
support for the qualitative analyti
Page 86 and 87:
where R(t) is the average position,
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where d stands for the gap width, V
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there are different oscillatory vel
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Phase [degrees] 60 50 40 30 20 10
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G 100 90 80 70 60 50 40 30 20 10 0
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possible for quite large Ro/Ri-valu
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upper right region of the figures,
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σse,max the zones become wider and
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G 50 45 40 35 30 25 20 15 10 5 0.2
Page 104 and 105:
creasing ratio Ri/Ro was observed.
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Chapter 6 Detection of multipactor
Page 109 and 110:
Amplitude of acceleration [Gm/s 2 ]
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tipactor events that are short-live
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software and the time evolution of
Page 115 and 116:
ditional test sample, a resonant ca
Page 117 and 118:
the FFT. It was concluded that ther
Page 119 and 120:
6.2.1 Single carrier When using the
Page 121 and 122:
Reference signal generator Phase co
Page 123 and 124:
Amplitude [A.U.] 2.5 2 1.5 1 0.5 De
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Chapter 7 Conclusions and outlook T
Page 127 and 128:
tioned there were multipactor in no
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References [1] W. Henneberg, R. Ort
Page 131 and 132:
[27] A. Ruiz et al, “Ti, V, and C
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[51] D. Wolk, D. Schmitt, and T. Sc
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[75] R. Udiljak, Multipactor in low
Page 137:
Included papers A-F 123
Page 141:
Paper B R. Udiljak, D. Anderson, M.
Page 145:
Paper D R. Udiljak, D. Anderson, M.
Page 149:
Paper F V. E. Semenov, N. Zharova,
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