R. Akre, P. Emma, P. Krejcik LCLS RFakre@, emma@, [email protected] April 29, 2004 LCLS RF...

R. Akre, P. Emma, P. Krejcik

LCLS RF akre@ , emma@, [email protected]

April 29, 2004

LCLS RF Stability Requirements

LCLS Requirements

The SLAC Linac

SLAC Linac Stability Data

SPPS Measurements

LCLS RF System



April 29, 2004

LCLS INJECTOR / LINAC



April 29, 2004

LCLS Machine Stability Tolerance BudgetLCLS Machine Stability Tolerance Budget

X-bandX-band XX--

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.



April 29, 2004

LINAC RF and Timing System

PEP PHASE SHIFT ON MAIN DRIVE LINE MDL RF with TIMING Pulse – Sync to DR

Master Oscillator is located 1.3 miles

from LCLS Injector1.3 Miles to

LCLS Injector



April 29, 2004

Linac Phase Reference SystemMain Drive Line - 3 1/8 Rigid Coax Anchored to Concrete Floor Every SectorPhase Reference Line - Each Sector Independent 1/2 “ Heliax



April 29, 2004

Linac Phase Reference SystemMain Drive LineMain Drive Line

3 1/8 inch Rigid Coax with 3 1/8 inch Rigid Coax with 30watts30watts

Length = 31 Sectors, 15.5 Length = 31 Sectors, 15.5 furlongs 2miles, 3km : Velocity = furlongs 2miles, 3km : Velocity = 0.98c0.98c

Anchored at each sector next to Anchored at each sector next to coupler and expansion jointcoupler and expansion joint

Purged with dry nitrogenPurged with dry nitrogen

Phase Length Range 100Phase Length Range 100S/YearS/Year

Phase Length Range 40Phase Length Range 40S/DayS/Day

Accuracy Based on SLC Fudge Accuracy Based on SLC Fudge FactorFactor

0.50.5S/Sector Total VariationS/Sector Total Variation

0.2S rms / Sector

Phase Reference LinePhase Reference Line

½ inch Heliax Cable with 1.2 Watts½ inch Heliax Cable with 1.2 Watts

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

Length = 1 Sector, 0.5 furlongs, 332ft, Length = 1 Sector, 0.5 furlongs, 332ft, 400k400kS in ½” HeliaxS in ½” Heliax

Temperature Coefficient 4ppm/Temperature Coefficient 4ppm/CC

Waveguide Water Waveguide Water T = 0.1T = 0.1C rmsC rms

85% of the cable is regulated to 0.185% of the cable is regulated to 0.1C C rmsrms

15% may see variations of 215% may see variations of 2C rmsC rms

Average Temperature Variation = 0.4Average Temperature Variation = 0.4C C rmsrms

= 0.64= 0.64S rmsS rms



April 29, 2004

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.



April 29, 2004

LINAC RF MEETS ALL LCLS SPECIFICATIONSfor 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.



April 29, 2004

LINAC RF is Out of LCLS Specs in 1 Minute

14 minutes data taken using the SCP correlation plot

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

Amplitude

22-6

0.20%pp

Amplitude

22-7

0.43%pp

Phase

22-6

1.2 Deg pp

Phase

22-7

1.2 Deg pp



April 29, 2004

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< .08Frms

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

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

SLAC Linac Accelerator Water Temperatures T< .08Frms

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



April 29, 2004

Linac Phase Stability Estimate Based on Energy Linac Phase Stability Estimate Based on Energy Jitter in the ChicaneJitter in the Chicane

SLAC LinacSLAC Linac

1 GeV1 GeV 30 GeV30 GeV9 GeV9 GeV

ee Energy (MeV) Energy (MeV)

BPM

221/21/2< 0.1 deg (100 fs)< 0.1 deg (100 fs)

EE/E/E00 0.06% 0.06%



April 29, 2004

LCLS Phase Noise Associated Time Referenced to Beam Time

LCLS Laser Need to Measure10uS to 1mS

LCLS Gun 1.1uS SLED / Accelerator 3.5uS Phase Detector (Existing) 30nSDistribution System 200nS

1km @ c-97%c=100nS

Far Hall Trigger 2uS3km @ c-80%c=2uS

TIME

-3.5us SLED Starts to Fill

-1.1uS Gun Starts to Fill

-2uS Far Hall TrigRF Starts Trip

Beam Time 0Reference



April 29, 2004

Phase Noise of SLAC Main Drive Line

Noise Floor of About -120dBc/38Hz = -136dBc/Hz = 120fS 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



April 29, 2004

SPPS Laser Phase Noise Measurements

Phase Noise of Output of Oscillator with Respect to Input

Measurement done at 2856MHz with External Diode



April 29, 2004

Jitter determination from Electro Optic sampling

Er

Principal oftemporal-spatial correlation

Line image camera

polarizer

analyzer

EO xtal

seconds, 300 pulses: z = 530 fs ± 56 fs rms t = 300 fs rmsseconds, 300 pulses: z = 530 fs ± 56 fs rms t = 300 fs rms

single pulse

A. Cavalieri

centroidwidth



April 29, 2004

LINAC SECTOR 20 – LCLS INJECTOR

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



April 29, 2004

LCLS RF System – Sector 20 Layout

100ft ½” Heliax = 0.3ºS/ºF



April 29, 2004

Beam Trigger for User Facility

Wide Bandwidth – Rising Edge of 8nS ?

Low Phase Noise – 30fS Stability

Design Needs Input



April 29, 2004

LCLS RF System

Injector RF – FY06Upgrade of existing system / Lower Noise Timing requirementsInjector/L1 Phase Reference SystemPhase and Amplitude measurement systemSolid State Sub-BoostersBeam Phase Monitor System

X-Band RF system – FY06Linac Phase Reference System – FY07 Linac Feedback Control – FY07Far Hall Trigger – FY08Feedback Development – FY07



April 29, 2004

Near Term (6 Month) Tasks

Measure Phase Noise and Response of SPPS Laser

Install New Oscillator, -157dBc/Hz floor, in Accelerator and Measure Phase Noise

Determine Type of RF Phase and Amplitude Measurement System

R. Akre, P. Emma, P. Krejcik LCLS RFakre@, emma@, [email protected] April 29, 2004 LCLS RF...

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