123 lines
5.0 KiB
Markdown
123 lines
5.0 KiB
Markdown
---
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title: BEAMDATA.txt
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section: 5
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---
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# NAME
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beamdata.txt --- beam launcher data for **gray**(1)
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# FORMAT
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The beam launcher data can be provided in three ways, each with a corresponding
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file format.
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## 0D format
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The beam parameters are given as fixed numbers, independent of the values of
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the launch angles α, β. In this case the format is as follows:
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f ! comment
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x₀ y₀ z₀
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w₀₁ w₀₂ d₀₁ d₀₂ φ
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where:
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- *f* is the frequency (GHz)
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- *x₀, y₀, z₀* are the launcher position (cm)
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- *w₀₁, w₀₂* are the beam waists in the two principal directions (cm)
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- *d₀₁, d₀₂* are the distances of the beam waists from the launch point (cm)
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- *φ* is the rotation angle from the horizontal direction to the first
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principal direction (deg)
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Note: this case implies simple astigmatism, i.e. the amplitude and phase
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ellipses in the beam transverse plane are aligned.
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## 1D format
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The beam parameters, including the launch position and angles, are given as a
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function of the launcher steering angle *θ* in tabular format. The data will be
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interpolated by GRAY to obtain the actual beam parameters at a given pair of
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launch angles.
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The format is as follows:
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f ! comment
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nrows
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θ α β x₀ y₀ z₀ w₁ w₂ k₁ k₂ φ_w φ_R
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θ α β x₀ y₀ z₀ w₁ w₂ k₁ k₂ φ_w φ_R
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...
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The first two lines contain the frequency (GHz) and the number of table rows.
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The rest of the file contains the whitespace-separated records, one row per
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line, where:
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- *θ* is the mechanical steering angle (unused)
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- *α, β* are the poloidal and toroidal launch angles (deg)
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- *x₀, y₀, z₀* are the launcher position (mm)
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- *w₁, w₂* are the beam widths in the two principal directions (mm)
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- *k₁, k₂* are the wavefront curvatures in the two principal directions (mm⁻¹)
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- *φ_w, φ_R* are the rotation angles of the amplitude and phase
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ellipses in the transverse plane at the launch point (deg)
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## 2D format
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The beam parameters, including the launch position, are given as a
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function of the two launch angles α, β. The format is as follows:
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nbeams
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id mode f na nb
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α β x₀ y₀ z₀ w₁ w₂ k₁ k₂ φ_w φ_R
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α β x₀ y₀ z₀ w₁ w₂ k₁ k₂ φ_w φ_R
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...
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id mode f na nb
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α β x₀ y₀ z₀ w₁ w₂ k₁ k₂ φ_w φ_R
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α β x₀ y₀ z₀ w₁ w₂ k₁ k₂ φ_w φ_R
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...
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The first line specifies the number of beams described by the file.
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The rest of the files consists of *nbeams* 2D tables preceded by a header where:
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- *id* is a string identifier of the beam
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- *mode* indicates where the beam has O-mode (*1*) or X-mode (*2*)
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polarisation
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- *f* is the frequency (GHz)
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- *nα, nβ* are the numbers of rows and columns of the table
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The 2D table is stored in row-major order over *nα×nβ* lines, that is, the
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*i,j*-th record is stored on the l-th line, with *l = i + nα×j*.
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The poloidal angle *α(i,j)* must be monotonic along *i* and the toroidal angle
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*β(i, j)* must be monotonic along *j*.
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Each line stores one record with the same fields as in the 1D format.
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Note: even if this format allows to define multiple independent beams in the
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same file, this feature is not used by **gray**(1), which always load the first
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table.
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# EXAMPLES
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1. A valid 0D beamdata.txt file
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170 ! f
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950.0 0.0 62.0 ! x₀ y₉ z₀
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2.1 2.1 162.0 162.0 0.0 ! w₀₁ w₀₂ d₀₁ d₀₂ φ
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2. A valid 1D beamdata.txt file
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170 ! f
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27 ! nrows
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-7.5 25.93 19.75 7067.6 -41.45 4233.6 42.70 43.99 -5.899E-4 -5.363E-4 -3.15 -3.15
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-5.0 31.23 19.99 7067.8 -41.48 4233.6 42.70 43.99 -5.899E-4 -5.364E-4 -2.32 -2.32
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-2.0 37.61 20.09 7068.1 -41.51 4233.5 42.69 43.98 -5.900E-4 -5.364E-4 -1.09 -1.09
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3.5 49.29 19.77 7068.7 -41.58 4233.2 42.67 43.97 -5.902E-4 -5.366E-4 -2.11 -2.11
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3. A valid 2D beamdata.txt file
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1 ! nbeams
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example 1 137.6 6 2 ! id mode f nα nβ
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-7.96 -12.99 4352 -161.2 907 16.46 28.67 -2.48E-05 -2.36E-03 -21.79 5.61
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4.82 -13.18 4392 -149.4 976 15.80 26.29 -4.71E-05 -2.56E-03 -17.88 8.85
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14.52 -13.40 4416 -138.6 1031 15.30 24.50 -1.72E-04 -2.80E-03 -14.87 11.95
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24.86 -13.70 4438 -125.4 1091 14.92 22.66 -4.36E-04 -3.19E-03 -11.63 15.84
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36.12 -14.12 4455 -109.2 1159 14.90 20.80 -8.64E-04 -3.81E-03 -8.29 20.21
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48.76 -14.72 4466 -89.0 1235 15.74 18.91 -1.38E-03 -4.80E-03 -7.66 23.62
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-9.80 -6.93 4353 -132.0 904 16.71 29.36 -1.71E-04 -2.28E-03 -10.02 8.52
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2.84 -7.14 4392 -123.8 972 16.03 26.82 -1.85E-04 -2.46E-03 -7.62 10.46
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12.39 -7.38 4416 -116.4 1025 15.53 24.95 -3.05E-04 -2.67E-03 -5.78 12.41
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22.50 -7.72 4437 -107.4 1084 15.13 23.06 -5.55E-04 -2.99E-03 -3.79 14.90
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33.42 -8.18 4454 -96.5 1149 14.57 21.17 -9.75E-04 -3.51E-03 -10.43 14.82
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45.51 -8.80 4465 -83.0 1222 15.65 19.32 -1.48E-03 -4.35E-03 0.41 20.57
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