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ELETTRA FEL Parameter List
last updated 14/2/00
ELECTRON BEAM
General parameters :
ring circumference = 259.2 m
orbit time = 864 ns
orbit frequency = 1.157 MHz
r.f. frequency = 499.654 MHz
harmonic no. = 432
beta functions at ID centre (horiz., vert.) = 8.2, 2.6
dispersion function at ID centre = zero
momentum compaction factor = 0.00161
normal operating tunes = (14.3, 8.2)
FEL mode :
operating energy (first phase) = 1 GeV
no. of bunches = 4
bunch spacing = 64.8 m
bunch frequency = 4.626 MHz
energy loss/turn = 15.91 keV
damping times (horiz., vert., long.) = 82, 109, 65 ms
natural rms emittance = 1.74 nm rad
natural rms energy spread = 0.0397 %
natural rms bunch length = 6.28 ps
r.f. accel. voltage = 1.764 MV
synchrotron frequency = 16.1 kHz
synchrotron tune = 0.014
Beam sizes :
- Assuming 2 x natural emittance to account for Intra Beam Scattering
10 % coupling : emittances (h,v) = 3.16, 0.316 nm rad
beam sizes (h,v) = 0.161, 0.029 mm
100 % coupling : emittances (h,v) = 1.74, 1.74 nm rad
beam sizes (h,v) = 0.119, 0.067 mm
Bunch length and Energy spread :
Current/bunch
(mA)
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Measured rms bunch length (ps)
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Peak current (A)
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Expected rms energy spread (%)
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Measured rms energy spread (%)
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5
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21.4
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72
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0.135
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0.112
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10
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26.4
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118
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0.167
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-
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15
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29.4
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159
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0.186
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-
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20
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31.7
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198
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0.200
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-
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25
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34.0
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228
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0.215
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-
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Note:
1) Peak current estimated from ratio of peak to integrated intensity
in the streak camera image; approximately 10 % less than the calculated
value assuming a Gaussian with the quoted rms bunch length.
2) Expected energy spread assumes the same increase as for the bunch
length
3) Measured energy spread derived from optical klystron spectra
OPTICAL CAVITY
distance between mirrors = 32.4 m
distance from upstream mirror to undulator centre = 17.7
m
distance from downstream mirror to undulator centre = 14.7 m
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A
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B
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nominal radius of curvature of upstream mirror (m)
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19.0
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17.5
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nominal radius of curvature of downstream mirror (m)
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16.0
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17.5
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Rayleigh length (m)
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4.57
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4.59
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position of waist with respect to center of O.K.
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0.13 m
downstream
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1.5 m
upstream
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stability parameter g12
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0.72
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0.72
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mode size at waist
(w, 350 nm) (mm)
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0.71
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0.71
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mode size at mirrors
(w, 350 nm) (mm)
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2.88, 2.38
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2.62, 2.62
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UNDULATOR
type : APPLE-II permanent magnet, optical klystron configuration
period = 100 mm
No. periods per undulator section = 20
Minimum gap = 19 mm
Maximum K value, circular polarization = 5.85
K (1 GeV, 350 nm) = 5.080
K (1 GeV, 200 nm) = 3.784
modulator
type : electromagnetic, 3 pole
nominal maximum Nd = 80 (350 nm)
maximum field = 0.8 T
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