CLIC Workshop 2009

CLIC Workshop 2009CLIC Workshop 2009

A. Andersson 2009-10-14A. Andersson 2009-10-14

12GHz Phase Monitor

12GHz Phase Monitor

Alexandra AnderssonCERN

Alexandra AnderssonCERN


A. Andersson 2009-10-14A. Andersson 2009-10-14See: Erk Jensen, 4th CLIC Advisory Committee (CLIC-ACE)

• Drive beam phase jitter leads to luminosity drop.• Δφ at 1 GHz causes 12 Δφ at 12 GHz!• Requirement at 1GHz (order of magnitude):

drive beam phase jitter <0.02° (3.5E-4, 50 fs)drive beam energy jitter <O(1E-4)

(With a feed-forward, this may be relaxed by a factor 10!)

• Requirement at 12GHz (order of magnitude): drive beam phase jitter <0.2° (3.5E-3, 50 fs)drive beam energy jitter <O(1E-4)

Energy and phase stability requirements in CLIC

Energy and phase stability requirements in CLIC



• Drive beam gun– Beam current changes acceleration!

at full loading:

– Phase jitter from the source

• Sub-harmonic buncher– Flips phase every 244ns. Creates also systematic error at 2.05 MHz

• via klystron:– Voltage

– Klystron body temperature:

– Drive power

– … filament current, magnet current, waveguides...

See: Erk Jensen, 4th CLIC Advisory Committee (CLIC-ACE)

K

T 1

dB

log3.2 inP

I

I

RIV

R

V

V

0

I

I

V

V 2

VVVL

2/32



Sub-task 1: CERN will determine the specifications and will produce a conceptual design report of the RF monitor. CERN and INFN will attend together to the electromagnetic design and then they will produce a building design of the monitor. CERN will develop and realize the related electronics. INFN will build prototypes of the monitor that will be measured and tested in lab. A final version of the monitor will be built and the performances of the system will be tested in CTF3.Sub-task 2: The electro-optical monitor will be designed by PSI. PSI will implement prototypes of the system, which includes pick-up, laser, electro optical detector and electronics. The performances of the system will be tested in the existing facilities at PSI.

Phase monitor development Phase monitor development Task 5. Drive Beam Phase Control

1. Design, build and test a low-impedance RF beam phase monitor with a resolution of 20 fs

2. Design, build and test an electro-optical phase monitor with a resolution of 20 fs

Vladimir Arsov, PSIOverview of the Phase

Measurement System at SLS/PSIWG3:15-Oct-2009, 11:30

in 40-S2-C01

This Presentation

Ready for beam tests in 2012 Ready for beam tests in 2012

Fabio Marcellini, INFNBeam Phase Monitor for CLIC

and CTF3: pick-up designWG3: 15-Oct-2009, 16:00

in 40-S2-C01



Timing Reference Timing Reference •Laser based timing distribution systems are making a lot of progress and can achieve femtosecond stability over a few kilometers•Otherwise, the outgoing main beam could be used as a reference at each turnaround•A very stable local oscillator needs to keep time for up to 160μs until the drive beam passes.

Phase referencesPhase measurements

Phase corrections

Laser based timing distribution systems

Local Measurements

Matthias FelberFemtosecond optical

synchronization system for FLASHWG3: 15-Oct-2009, 12:00

in 40-S2-C01F. Ömer Ilday

Long distance Optical Fibers with fs resolutionWG3 :15-Oct-2009, 11:00

in 40-S2-C01



Drive Beam

Main Beam Outgoing

PETS

Accelerating Structure

LO

21km

RF

Phase locked to low frequency refernce to prevent slow drift

Phase measurements in CLIC Phase measurements in CLIC



1 10 100 1k 10k 100k 1M 10M-180

-160

-140

-120

-100

-80

-60

-40

offset frequency, [Hz]

nois

e po

wer

, dB

c

Phase Noise LO

Filtering by beam path

Filtered noise

Local OscillatorLocal Oscillator•We need an Local Oscillator with «23fs integrated phase jitter•The beam path provides some noise filtering below 3kHz•The system here seems to come in around ~4fs

O5k€



Electronics challengesElectronics challenges•Device non-linearities•Phase detectors are inherently non-linear device•Suppose a detector with an RF input consisting of a pure (sin) amplitude modulated signal. It has frequency components: f0, f0-fm, f0+fm

•But all products of these are created at the input as well•2nd order: DC, 2f0, 2f0-2fm, 2f0+2fm, 2f0-fm, 2f0-fm, fm, 2fm

•And 3rd, and 4th, and ...•Which mix with the LO and all its harmonics: f0, 2f0, 3f0...

•These are all weighted by complex coefficients that depend on device parameters and parasitics. Complex → AM-PM conversion•And for an nth order product, on the amplitude•Thus, it is possible to find an operating point where the non-linear terms are small enough

nV0



•Mixing to baseband directly from 12GHz to avoid long device chains•The amplitude-squared dependant DC-DC term can be made small enough at low input levels•It follows a square law as expected•IF frequency response could be better

-16 -15 -14 -13 -12 -11 -10 -9 -8-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

1.4

Input power, dBm

Pha

se o

ffse

t, d

egre

es

-100 -10 -1 -0.1 -0.01 0.01 0.1 1 10 100-2

-1.5

-1

-0.5

0

0.5

offset frequency, MHz

outp

ut,

dB

frequency response to offset input

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1-2

0

2

4

6

8

10

12

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16

Input amplitude, a.u.

DC

Pha

se o

ffse

t, d

egre

es

measured

square fit

curves: various amplitudes

curves: various frequencies

Looking at a 12GHz mixerLooking at a 12GHz mixer



Managing non-linearities and noise

Managing non-linearities and noise



ConclusionsConclusions•An important topic for CLIC•Electronics already realised and tested at 30GHz for similar requirements.•Migration to 12GHz under way – similar and different approach•Should have electronics prototype to bench test and to test with CTF3 signals from TBTS in 2010

CLIC Workshop 2009

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Transcript of CLIC Workshop 2009