Layout of the Synchronisation System for the VUV-FELDipl. Ing. Henning Christof WeddigDESY Hamburg

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RF System RequirementsSystem Length200 m (VUV_FEL); 3 km (XFEL)RF Phase Noise (within macropulse 1 ms)0.05o RMS (at 1.3 GHz) ~0.1 psRF Phase Noise (during 100 ms time)0.15o RMS (at 1.3 GHz) ~0.3 psRF Phase Stability (short term

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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