LCLS Drive Laser Timing Stability Measurements
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LCLS Drive Laser Timing Stability Measurements. Department of Energy Review of the Linac Coherent Light Source (LCLS) Project Breakout - SC5 Control Systems August 11, 2004 Ron Akre. X -. X-band. LCLS Machine Stability Tolerance Budget. Lowest Noise Floor Requirement 0.5deg X-Band = 125fS

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LCLS Drive Laser Timing Stability Measurements

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Lcls drive laser timing stability measurements

LCLS Drive Laser Timing Stability Measurements

Department of Energy Review of theLinac Coherent Light Source (LCLS) ProjectBreakout - SC5 Control SystemsAugust 11, 2004Ron Akre


Lcls machine stability tolerance budget

X-

X-band

LCLS Machine Stability Tolerance Budget

Lowest Noise Floor Requirement

0.5deg X-Band = 125fS

Structure Fill time = 100nS

Noise floor = -108dBc/Hz @ 11GHz 5MHz BW

-134dBc/Hz @ 476MHz

RMS tolerance budget for <12% rms peak-current jitter or <0.1% rms final e− energy jitter. All tolerances are rms levels and the voltage and phase tolerances per klystron for L2 and L3 are Nk larger, assuming uncorrelated errors, where Nk is the number of klystrons per linac.

P. Emma


Linac rf and timing system

LINAC RF and Timing System

LCLS must be compatible with the existing linac operation including PEP timing shifts

Master Oscillator is located 1.3 miles from LCLS Injector

1.3 Miles to LCLS Injector

PEP PHASE SHIFT ON MAIN DRIVE LINE

MDL RF with TIMING Pulse – Sync to DR


Linac phase reference system

Linac Phase Reference System

  • Main Drive Line - 3 1/8 Rigid Coax Anchored to Concrete Floor Every Sector

  • Phase Reference Line - Each Sector Independent 1/2 “ Heliax

  • Must not introduce noise over 2 miles


Linac phase reference system1

Linac Phase Reference System

  • Phase Reference Line

  • ½ inch Heliax Cable with 1.2 Watts

  • Phase Reference for 8 PADs (Klystrons) in the sector

  • Length = 1 Sector, 0.5 furlongs, 332ft, 400kS in ½” Heliax

  • Temperature Coefficient 4ppm/C

  • Waveguide Water T = 0.1C rms

  • 85% of the cable is regulated to 0.1C rms

  • 15% may see variations of 2C rms

  • Average Temperature Variation = 0.4C rms

  •  = 0.64S rms

  • Main Drive Line

  • 3 1/8 inch Rigid Coax with 30watts input power 30mW out

  • Length = 31 Sectors, 15.5 furlongs 2miles, 3km : Velocity = 0.98c

  • Anchored at each sector next to coupler and expansion joint

  • Purged with dry nitrogen

  • Phase Length Range 100S/Year

  • Phase Length Range 40S/Day

  • Accuracy Based on SLC Fudge Factor

  • 0.5S/Sector Total Variation

  • 0.2S rms / Sector


Phase noise of slac main drive line

Phase Noise of SLAC Main Drive Line

Old Oscillator

New Oscillator

Noise Floor -120dBc/38Hz = -136dBc/Hz = 120fS rms Jitter in 5MHz BW

Noise Floor -133dBc/38Hz = -149dBc/Hz < 60fS rms Jitter in 5MHz BW

New Oscillators Have a noise floor of -157dBc/Hz @ 476MHz

11fS rms Jitter in 5MHz BW or 31fS rms Jitter in 40MHz BW

Above plots give upper limits, much of which could be from measurement system


Phase noise of slac main drive line1

Phase Noise of SLAC Main Drive Line

Old Oscillator

New Oscillator

New Oscillators Have a noise floor of -157dBc/Hz @ 476MHz

11fS rms Jitter in 5MHz BW or 31fS rms Jitter in 40MHz BW

Above plots give upper limits, much of which could be from measurement system


Slac linac rf

SLAC Linac RF

The PAD measures phase noise between the reference RF and the high power system. The beam sees 3.5uS of RF from SLED cavity which the klystron fills and is then dumped into the accelerator structure.


Linac rf meets all lcls specifications

LINAC RF MEETS ALL LCLS SPECIFICATIONS

for 2 Seconds when running well

Amplitude fast time plots show pulse to pulse

variation at 30Hz. Standard deviation in percent

of average amplitude over 2 seconds are

0.026% for 22-6 and 0.036% for 22-7.

Phase fast time plots show pulse to pulse variation

at 30Hz. Standard deviation in degrees of 2856MHz

over 2 seconds for the three stations are

0.037 for 22-6 and 0.057 for 22-7.


Linac rf is out of lcls specs in 1 minute

LINAC RF is Out of LCLS Specs in 1 Minute

Phase

22-6

1.2 Deg pp

Amplitude

22-6

0.20%pp

Amplitude

22-7

0.43%pp

Phase

22-7

1.2 Deg pp

14 minutes data taken using the SCP correlation plot

Note that 22-6 and 22-7 are correlated in phase and amplitude

They also track the temperature of the water system


Phase as seen by electron is difficult to measure

Phase as Seen by Electron is Difficult to Measure

Accelerator Water Temperature Effects on SLED Phase[1]

The tuning angle of the SLED cavity goes as:

 = tan -1 (2QLT), Where T = L/L = -/

QL= 17000= 10-5 / F Thermal expansion of copper.

=tan -1 (0.34T)Where T is in F.

For small T, (S)= 20T(F)

The relation between the tuning angle  and the measured output phase of the klystron 

varies with the time after PSK with about the following relation:

 /  = 0.35just after PSK (S)= 7T(F)

 /  = 0.50800nS after PSK (S)= 10T(F)

 / T~ +8.5 S / F for SLED Cavity

Accelerator Water Temperature Effects on the Accelerator Phase[2]

The phase change of the structure goes as follows:

 = fWhere  = phase through structure

 = Angular frequency

f = Filling time of structure

 = f = / x f/ = -L/L = -T = -10-5 T / F for copper

 = -10-5 T / F22856MHz0.84S = -0.15 T rad/F = -8.6 T S / F

 / T = -8.6 S / F for Accelerator Structure

Water / Accelerator Temperature Variation is 0.1F rms

 through structure is 0.86F rms

[1] Info from D. Farkas

[2] Info from P. Wilson


Phase as seen by electron is difficult to measure1

Phase as Seen by Electron is Difficult to Measure

  • Accelerator Water Temperature Effects on the Phase Through the Accelerator-8.6 S / F

  • SLAC Linac Accelerator Water TemperaturesT< .08Frms

  • Phase Variations Input to Output of Accelerator > 0.5ºS-Band rms

  • Single Measurement Can’t Determine the Phase the Beam Sees Passing Through the Structure to LCLS Specifications

  • Feedback on Input Phase, Output Phase, Temperature, Beam Based Parameters (Energy and Bunch Length) is Required to Meet LCLS Specifications


Linac sector 20 lcls injector

LINAC SECTOR 20 – LCLS INJECTOR

RF Stability < 50fS rms : Timing/Trigger Stability 30pS rms

Using LASER as LCLS RF OSCILLATOR is UNDER CONCIDERATION


Lcls rf system sector 20 layout

LCLS RF System – Sector 20 Layout

100ft ½” Heliax = 0.3ºS/ºF

Tunnel Temperature < 0.1deg F rms


Spps laser phase noise measurement

SPPS Laser Phase Noise Measurement

R. Akre, A. Cavalieri


Spps laser phase noise measurements

SPPS Laser Phase Noise Measurements

Phase Noise of Output of Oscillator with Respect to Input

Measurement done at 2856MHz with External Diode

Need to verify these results and check calibration

R. Akre, A. Cavalieri


Spps laser amplitude of phase transfer function

SPPS Laser Amplitude of Phase Transfer Function

Phase Modulation placed on RF Reference and measured on Diode at Laser output.

During the Blue part of the curve the modulation amplitude was reduced by 12dB to prevent laser from unlocking. Data taken 10/22/03 R. Akre, A. Cavalieri


Spps laser phase jump tracking

SPPS Laser Phase Jump Tracking

R. Akre, A. Cavalieri


Spps laser phase jump tracking1

SPPS Laser Phase Jump Tracking

Laser Phase Error – Output Phase to Input Reference - Modulated with 1 Hz Square Wave

0.25pS pk Square Wave

2.0pS pk Square Wave


Linac phase stability estimate based on energy jitter in the chicane

SLAC Linac

1 GeV

30 GeV

e- Energy (MeV)

Linac Phase Stability Estimate Based on Energy Jitter in the Chicane

BPM

9 GeV

sE/E0 0.06%

Df 21/2< 0.1 deg (100 fs)

P. Emma


Electro optical sampling

Electro-Optical Sampling

Timing Jitter

(20 Shots)

200 mm thick ZnTe crystal

Single-Shot

e-

<300 fs

Ti:Sapphire laser

e- temporal information is encoded on transverse profile of laser beam

170 fs rms

Adrian Cavalieri et al., U. Mich.


Lcls phase noise associated time referenced to beam time

LCLS Phase Noise Associated Time Referenced to Beam Time

  • LCLS Laser~200uS Off Scale Below

  • LCLS Gun1.1uS

  • SLED / Accelerator 3.5uS

  • Phase Detector (Existing)30nS

  • Distribution System200nS

    • 1km @ c-97%c=100nS

  • Far Hall Trigger2uS

    • 3km @ c-80%c=2uS

Except for the LASER common mode noise levels below ~100kHz would not cause instabilities – the entire system would track the deviations

-3.5us SLED Starts to Fill

-2uS Far Hall Trig

RF Starts Trip

-1.1uS Gun Starts to Fill

Beam Time 0

Reference

TIME


Beam trigger for user facility

Beam Trigger for User Facility

  • Single Pulse with 30fS stability (1Hz to 3GHz BW)

  • Tightest Noise Tolerance of LCLS

  • Wide Bandwidth

  • Low Phase Noise

    • 30fS Stability today

    • 10fS Stability tomorrow

    • 1fS The Day After

  • Currently users are expected to use local beam timing measurement, EO, to achieve this.


Fy04 tasks

FY04 Tasks

  • Complete phase measurement system

  • Complete measurements in the SLAC front end

  • Preliminary design for SLAC linac RF upgrade

  • Complete Design of 1kW Solid State S-Band Amp


Fy05 tasks and resources ready to ramp up

FY05 Tasks and ResourcesReady to Ramp Up

  • Start on X-Band system

  • Complete SLAC Linac Front End Upgrades

  • Complete Design of Phase Reference System

  • Complete Design of LLRF Control System

  • Define Beam Phase Cavity Monitor

  • Further Studies on Linac Stability

SLAC Klystron Department to Support 75% of RF manpower

Manpower available from other SLAC groups (ARDA, ARDB, NLC, and Controls) and LBNL


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