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Layout of the Synchronisation System for the VUV-FEL. Dipl. Ing. Henning Christof Weddig DESY Hamburg. RF System Requirements. System Length200 m (VUV_FEL); 3 km (XFEL) RF Phase Noise (within macropulse – 1 ms) 0.05 o RMS (at 1.3 GHz) ~0.1 ps RF Phase Noise (during 100 ms time) - PowerPoint PPT Presentation
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Layout of the Synchronisation System for the VUV-FELDipl. Ing. Henning Christof WeddigDESY Hamburg
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System components
Ultra high stable master oscillatorRF distribution system (length at VUV-FEL about. 200 m)Temperature stabilized coaxial cables Local 1.3 GHz/2.856 GHz frequency generationFiber optic and coaxial system to monitor and correct long term phase drifts
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Frequencies to be distributed
the exact frequencies are multiples or divisions of the 9.027775 MHz reference frequency 1 MHz (timing of complete machine)9 MHz (master reference frequency)13.5 MHz (Laser new)27 MHz(Laser old)54 MHz(Laser for future use)81 MHz(distribution frequency)108 MHz(Streak camera [near RF Gun; Experimental Hall])1300 MHz(reference frequency for the linear collider)1517 MHz(reference frequency for beam position monitors)2856 MHz(LOLA = transverse deflecting cavity for bunch measurements)
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Block diagramme of MO (low level part)
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Phase noise requirements for the 1.3 GHz reference frequency
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Diagramm1
-80
-105
-125
-145
-155
-150
limit line
Integral = -90 dBc =0.00003 rad= 3 fs @ 1.3 GHz
Integral = -100 dBc= 0.00001 rad= 1 fs @ 1.3 GHz
Integral = - 95 dBc= 0.0000316 rad= 3 fs @ 1.3 GHz
Integral = -85 dBc= 0.00316 fs= 30 fs @ 1.3 GHz
Integral = -50 dBc= 0.003 rad366 fs @ 1.3 GHz
1RF cycle @ 1.3 GHz = 768 ps1 rad = 122 ps
overall phase jitter (double side band):2 * SQRT (366^2 + 30^2 + 3^2 + 1^2 + 3^2) = 2 * 367 fs = 734 fs = 0.7 ps
offset from carrier frequency (Hz)
Phase noise (dBc/Hz)
Phase noise limit line 1.3 GHz Reference Oszillator
Tabelle1
Frequency offsetPhase noisePhase noise
From carrierLocked conditionFree running
HzdBc/HzdBc/Hz
10-80< -60
100-105< -80
1000-125< -105
10000-145< - 135
100000-155< -155
1000000-150< - 150
Tabelle2
Tabelle3
Phase noise performance of a 27 MHz crystal oscillator
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Phase noise performance of a 81 MHz crystal oscillator
Phase noise is better above 400 Hz from carrier!
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MO front panel(low level part)
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Layout of the Reference frequency distribution system for TTF2
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The problem of long coaxial distribution links:Attenuation of coaxial cable vs frequency
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Phase stability of coaxial cable vs. Temperature cable
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Phase stability of coaxial cable vs. Temperature7/8 cable
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Advantages and disadvantages of coaxial cablesCoaxial cables for distribution: - high attenuation (e.g. 7/8 @ 1.3GHz A / 100m = 8dB)- physical dimensions- require temperature stabilization- can cause ground loops and pick up EMI
Fiber Optics for monitoring :- require active temperature stabilization- the system components are more expensive in comparison to coaxial line system components- high amplitude noise of a FO link
Solution:
A combination of both technologies will be implemented and studied at TTF2.
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Fiber optic distribution scheme
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First results of fiber optic stabilization
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