LCLS LLRF System October 10-13, 2005

LLRF05

B. Hong, R. Akre, A. Hill, D. Kotturi, H. Schwarz

SLAC, Stanford, Menlo Park, CA 94025, USA

Work supported under DOE Contract DE-AC03-76SF00515

OutlineOverview of LCLS Injector RF SystemLCLS RF Stability RequirementsLow Noise RF Distribution SystemRF Control and Monitoring System

LCLS INJECTOR / LINAC The LCLS linac consists of 4 sections. The injector L0 (2 S-Band

Klystrons) will reside in an off axis tunnel at the end of sector 20. L1 will have 1 S-band and 1 X-band klystron to feed their linacs, respectively. L2 (28 klystrons) and L3 (48 klystrons) are made up of the current main SLAC linac sectors 21 to 30.

The site layout of the LCLS linac

LCLS RF Stability Requirements Phase and Amplitude requirements by the physics design:• LCLS specifications require RF stability of 0.1%rms in amplitude

and 100fSrms in a 850nS fill time S-Band structure, but the tightest tolerance is 125fSrms in a 100nS fill time X-Band structure. See Table on next page.

Bandwidths of the X-band System• Beam seen due to structure fill time ~ 10MHz• Structure RF Bandwidth ~ 40MHz• XL4 Klystron > 100MHz Bandwidths of the S-Band System• Beam seen due to structure fill time ~ 1.2MHz• Structure RF Bandwidth ~ 16MHz• 5045 Klystron ~ 10MHz The bandwidth for the system will be determined based on

noise levels of the as built RF system and rise times of interest, somewhere between 1.2MHz and 10MHz.

Parameter Symbol |ΔI/I0| < 12% |ΔE/E0| < 0.1% Unitmean L0 rf phase (2 klystrons) 0 0.10 0.10 S-band deg

mean L1 rf phase (1 klystron) 1 0.10 0.10 S-band deg

mean LX rf phase (1 klystron) x 0.5 0.5 X-band deg

mean L2 rf phase (28 klystrons) 2 0.07 0.07 S-band deg

mean L3 rf phase (48 klystrons) 3 0.5 0.15 S-band deg

mean L0 rf voltage (1-2 klystrons) ΔV0/V0 0.10 0.10 %

mean L1 rf voltage (1 klystron) ΔV1/V1 0.10 0.10 %

mean LX rf voltage (1 klystron) ΔVx/Vx 0.25 0.25 %

mean L2 rf voltage (28 klystrons) ΔV2/V2 0.10 0.10 %

mean L3 rf voltage (48 klystrons) ΔV3/V3 0.5 0.08 %

BC1 chicane ΔB1/B1 0.01 0.01 %

BC2 chicane ΔB2/B2 0.05 0.05 %

Gun timing jitter Δt0 0.8 0.8 psec

Initial bunch charge ΔQ/Q0 2.0 4.0 %

RMS tolerance budget for <12% rms peak-current jitter (column 3) or <0.1% rms final e− energy jitter (column 4). The tighter tolerance is in BOLD, underlined text and both criteria, |DI/I0| < 12% and |DE/E0| < 0.1%, are satisfied with the tighter tolerance applied. 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.

Phase Noise of SLAC Master Oscillator

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

Old Oscillator New Oscillator

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

Noise Floor -143dBc/38Hz = -158dBc/Hz < 16fS rms Jitter in 10MHz BW

LINAC Front End 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

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

MASTERAMPLIFIERS

MAIN LINAC (SECTOR 0) RF/TIMING SYSTEM

1

476MHzMASTEROSCILLATOR

PEP PHASESHIFTER+-720 Degreesin 0.5mS

SLC COUNTDOWNCHASSIS 476MHzDivide to 8.5MHz

Master TriggerGenerator MTGSyncs Fiducial to8.5MHz Damping Ringand 360Hz Power Line

8.5MHz

360Hz LineSync.

476MHz

360Hz

Fiducial GeneratorSyncronized to:360Hz Power Line8.5MHz Damping Ring476MHz RF Distribution

SumFiducialto RF

Main Drive Line (MDL)476MHz RF plus360Hz FiducialTo:Main Linac - 2 milesDamping RingsPEPNLCTAEnd Station AFFTBORION

RF Distribution SystemM ain D rive L ine (M D L )4 7 6 M Hz R F3 6 0 Hz F id uc ia lF ro m S e c to r 0 (2 km ) RF HUT Coupler

476MHz Ref.

M D L to L inac S e c to rs 2 1 to 3 0P E P and R e s e arc h Yard

LCLS Sector 20 RF Reference System

T IM ING R F

1 1 9 M Hz 4 7 6 M HzO U T

T rac k/Ho ld1 2 0 Hz

T IM ING S YS T E MF ID O

L C L S M a s te r O s c .4 7 6 M Hz P L L4 7 6 M Hz w ith

3 6 0 H z F id uc ia l

TR IG G E R S3 0 pS rms J itte r 1 1 9 M H z

O U T

476MHz to 2856MHzMULTIPLIER

2856MHz2Watt Amplifier

2856MHz16 Way Distribution20dBm each

119MHz2W Amplifier

G unL 0 AL 0 BL 0 T C A VL 1 SL 1 XL IN A CE X P E R IM E N T S

1 1 9 M HzD ig itize r C lo c ks1 6 W ay D is trib u tio n2 0 d B m e ac h

G unL 0 AL 0 BL 0 T C A VL 1 SL 1 X

2 8 3 0 .5 M Hz L O1 6 W ay D is trib utio n2 0 d B m e ac h

2830.5MHz LO Gen2856MHz in119MHz in 2830.5MHz out

G unL 0 AL 0 BL 0 T C A VL 1 SL 1 X

2830.5MHz2Watt Amplifier

RF MONITOR

RF MONITOR

RF CONTROL

RF CONTROL

RF CONTROL

RF CONTROL

RF CONTROL

RF CONTROL

RF MONITOR

Phase Control

Phase Control

476MHz LO16 Way Distribution20dBm each

476MHz2Watt Amplifier

Phase Control

2 8 5 6 M HzL A S E R L O C KR e fe re nc e

Phase Control

P has e C o ntro l

Power Monitor

Power Monitor

1 1 9 M HzM o nito r

Power Monitor

PowerMonitor

L A S E R D io d eP has e No is eM e as ure m e nt

CHASSIS Needed to be Built

L A S E R D io d eO utp ut

L O P has e M o nito r

PhaseControl

Linac Phase Reference System Main Drive Line - 3 1/8 Rigid Coax Anchored to Concrete Floor Every Sector

Must not introduce noise over 2 miles. Diurnal Temperature Variations 200fS rms/Sector Phase Reference Line - Each Sector Independent 1/2 “ Heliax

332ft/Sector. Diurnal Temperature Variations 640fS rms errors

The PAD measures phase noise between the reference RF and the high power system. The

beam sees 3.5uS of RF from SLED.

Noise LevelsRF Reference Noise Floor

Oscillator -148dBc/Hz SSB at 2856MHzRF -138dBc/Hz SSB at 2856MHz

Integrated Noise -138dBc/Hz at 10MHz = -65dBc = 32fS rmsSNR = 65dB for phase noise

Added noise from MIXER (LO noise same as RF)SNR of 62dB

ADC noise levelsSNR of 70dB – 14bit ADS5500 at 119MSPS 8.5MHz

RF Control and Monitor Points Summary

RF Gun 1 Klystron 3 RF monitors Beam Phase Cavity 1 IQ modulator 1 RF monitor L0-A Accelerator 1 Klystron 2 RF monitors L0-B Accelerator 1 Klystron 2 RF monitors L0-T Transverse Accelerator 1 Klystron 2 RF monitors L1-S Station 21-1 B, C, and D accelerators

1 Klystron 4 RF monitors L1-X X-Band accelerator X-Band S25-Tcav 1 Klystron 2 RF monitors S24-1, 2, & 3 Feedback 3 Klystrons S29 and S30 Feedback 2 IQ modulators 476MHz

Totals 2856MHz 10 modulators 16 monitors

RF Monitor LO 2830.5MHz : RF 2856MHz IF 25.5MHz (8.5MHz x 3 in sync with timing fiducial) Double-Balanced Mixer Mixer IF to Low Pass Filter and Amp Amp output to ADC (119MSPS or 102MSPS)

MIXER

LO RF

IF

2830.5MHzReference

2856MHzRF Signal

AMP25.5MHz BP Filter

ADC 14bit 119MSPS1kWord FIFOColdfire microControllerEPICS on RTEMS

SLAC Linac RF – New ControlThe new control system will tie in to the IPA Chassis with 1kW of drive power available. Reference will be from the existing phase reference line or the injector new RF reference

I and Q will be controlled with a 16bit DAC running at 119MHz. Waveforms to the DAC will be set in an FPGA through a microcontroller running EPICS on RTEMS.

Existing System Accelerator

Klystron

Next SectorMDL 476MHz

SubBooster

6 X2856MHz

Sub Drive Line

High PowerPhase ShifterAttenuator

SLED

Phase &AmplitudeDetector

ExistingPhaseReferenceLine

-45dB200MW

3kW

20mW

1W1mW

To NextKlystron

I

RF LO

Q

1

2

3

4

IQ Modulator

1kW Amp2856MHz

IPA

RF Sub-Systems RF Gun Beam Phase Cavity L0-A Accelerator L0-B Accelerator L0-T Transverse Accelerator L1-S Station 21-1 B, C, and D accelerators L1-X X-Band accelerator S25-Tcav S24-1, 2, & 3 Feedback S29 and S30 Feedback

The RF Monitor unit will be capable of measuring phase and amplitude for 2 RF channels.

The RF Control unit will be of two versions. The fast version will digitize a 1k sample of data to drive an IQ modulator. The slow version will be capable of setting an I and Q value on a pulse to pulse basis.

RF Gun The RF Gun will be driven from klystron 20-6. The RF monitors on the gun will be used in feedback loops to control the operating frequency along with providing phase and amplitude information to the longitudinal feedback.

RF MONITOR

RF MONITOR

RF MONITOR

RF CONTROL

M o d ula to rH ig h V o ltag eM o nito r

E xis ting P has eR e fe re nc e

K lys tro nD riveM o nito r

K lystron S tation 20-6L C L S C o n tro lS ys te m P o in ts

E xis tingIP AC ha s s is

E xis tingM o nito rC o up le rs

K ly s tro nF o rw a rd

IQ M o dula to r K L YS T R O N

2 8 5 6 M H zR e fe re nc eF ro m R FH U T

1/2 Heliax is 4dB / 100ft @ 3GHz

TU N N EL

M K S UR e f le c te dP o w e r

E xis ting P A D

L0-G U NS L E D

L C L S C o ntro lS ys te m T C

S o lid S ta teS ub -B o o s te rA m p lif ie r

CHASSIS Needed to be Built

IQ D e mo dula to r

L O D is tr ibutio n

R F In

IQ D e mo dula to r2 8 3 0 M H zR e fe re nc e

IQ D e mo dula to rR F H U T C e l l 1

C e l l 2

G UN W a te rTemp Ana lo gCo ntro l

Beam Phase CavityThe Beam phase cavity will be used to measure the bunch position relative to the RF. The measurement will be done at 120Hz and provide information to the feedback system. The cavity is located between L0-A and L0-B accelerator structures.

RF CONTROL

RF MONITOR

L C L S C o ntro lS ys te mP o ints

1/2 Heliax is 4dB / 100ft @ 3G Hz

R FBeamPhaseC av ity

L C L S C o ntro lS ys te m T C

R F O u t

R F In

2 8 5 6 M HzR e fe re nc e

IQ D e mo dula to r

IQ M o dula to rF o r C a libra t io n

R F H U T

L O D is tributio n2 8 3 0 .5 M Hz

TU N N EL

L0-A - First accelerator in the off axis injectorL0-B has the similar control scheme.

RF

IN1

RF

OU

T2

E xis tingIP AC ha ss is

IQ M o dula to r

TU N N EL

E xis ting P A D

M K S UR e f le c te dP o w e r

E x is tingM o nito rC o up le rs

2 8 3 0 M H zR e fe re nc e

S o lid S tateS ub -B o o s te rA m p lif ie r

IQ D e modula to r

K L Y S T R O N

IQ D e modula to r

R F H U T

2 8 5 6 M HzR e fe re nc eF ro m R FH U T

LO D is tribution

K ly s tro nF o rw a rd

Klystron S ta tion 20-7L C L S C o ntro lS ys te mP o ints

A c c O u t

1/2 Heliax is 4dB / 100ft @ 3GHzL C L S C o ntro lS ys te m T C

A c c In

L0-A

S L E D

E xis ting P has eR e fe re nc e

K lys tro nD riveM o nito r

M o d u lato rH ig h V o ltag eM o nito r

RF MONITOR

RF MONITOR

RF CONTROL

CHASSIS Needed to be Built

Injector Transverse Deflector CavityStation 20-5 and Station 24-8 will be connected to the new control system and used to drive the L0 and Sector 25 transverse deflector cavities, respectively. The cavity is used to impart on the beam a deflection vs. longitudinal position correlation. The beam is deflected to a screen where bunch length can be measured.

RF

IN1

RF

OU

T2

RF MONITOR

RF MONITOR

RF CONTROL

R F H U T

IQ D e mo dula to r

L C L S C o ntro lS ys te mP o in ts

L O D is tributio n

IQ M o dula to r

E xis ting P has eR e fe re nc e

2 8 5 6 M H zR e fe re nc eF ro m R FHU T

E xis tingIP AC ha ss is

K lys tro nD riveM o nito r

A c c In

TU N N EL

2 8 3 0 M H zR e fe re nc e

K lystron S ta tion 20-5

S L E D

E xis ting P A D

1/2 Heliax is 4dB / 100ft @ 3GHz

L0-T

L C L S C o ntro lS ys te m T C

K ly s tro nF o rw a rd

M K S UR e f le c te dP o w e r

E xis tingM o nito rC o up le rs

IQ D e mo dula to r

K L YS T R O N

A c c O u t

S o lid S ta teS ub -B o o s te rA m p lif ie r

M o d ula to rH ig h V o ltag eM o nito r

CHASSIS Needed to be Built

L1-SThe L1 linac consist of klystron 21-1 powering 3

accelerator structures in the main linac.

S L E D

21-1B

RF

IN1

RF

OU

T221-1C

RF

IN1

RF

OU

T221-1D

A c c C O u t

IQ D e mo dula to r

IQ D e mo dula to r

A c c D O u t

M o d ula to rH ig h V o ltag eM o nito r

K lys tro nD riveM o nito r

RF MONITOR

RF MONITOR

RF MONITOR

RF CONTROL

CHASSIS Needed to be Built

RF

IN1

RF

OU

T2

2 8 3 0 M H zR e f e re nc e

2 8 4 5 M HzR e fe re nc eF ro m R FHUT

E xis tingIP A C ha ss is

IQ D e mo dula to r

IQ D e mo dula to r

L O D is tr ibu tio n

A c c B O u t

A c c B In

IQ M o dula to r

K lys tro nF o rw a rd

L C L S C o ntro lS ys te mP o in ts

E xis ting P A D

K L YS T R O NS o lid S tateS ub -B o o s te rA m p lif ie r

M K S UR e f le c te dP o w e r

E xis tingM o nito rC o up le rs

Klystron S ta tion 21-1

R F H U T

TU N N EL

L C L S C o ntro lS ys te m T C 1/2 Heliax is 4dB / 100ft @ 3G Hz

E xis ting P has eR e f e re nc e

X-Band 2nd order correctionAn X-band accelerator structure will be located at station 21-2, just before BC1. The beam will be run on the decelerating crest to remove the second order curvature in the bunch vs longitudinal position correlation before compression in BC1.

RF MONITOR ?

RF MONITOR

RF CONTROL

2 8 5 6 M H zR e f e re nc e

IP A C ha s s is

4 X M ultiplie rP ha s e S hifte rAmplifie r

2 8 4 5 M H zR e f e re nc eF ro m R F H U T

10dBm In Mon Out

D is tributio n

IQ D e mo dula to r

IQ D e mo dula to r

10dBm In

4 X M ultiplie rP ha se S hifte rAmplifie r

Mon Out

A c c O u t

A c c In

L C L S C o ntro lS ys te m P o ints

K ly s tro nF o rw a rd

IQ M o dula to r T W T A m p lif ie r K L YS T R O N

P A D

M o nito rC o up le rs

M K S UR e f le c te dP o w e r

RF

IN1

RF

OU

T2

TU N N EL

R F H U T

Klystron S ta tion 21-2

E xis ting w ith ne wR F H e ad

CHASSIS Needed to be Built

3/8 Heliax is 15dB / 100ft @ 12GHz1/2 Heliax is 4dB / 100ft @ 3G Hz

L C L S C o ntro lS ys te m T C

10dBm In

4 X M ultiplie rP ha s e S hifte rAmplifie r

Mon Out

D is tributio n

??

LOF re que nc yS hifte r

Mon Out

S24-1, 2, and 3 (Three Units)Two klystrons in sector 24 will be used to correct the phase and amplitude of the RF as seen by the beam in LCLS L2 before the beam enters BC2. The klystron phase and amplitude will be adjusted based on bunch length and energy measurements. A third klystron will be capable of use by the feedback system if one of the other two should fail.

M K S UR e f le c te dP o we r

E xis tingIP AC ha s s is

IQ M o dula to r

E xis ting P A D

E xis tingM o nito rC o up le rs

S o lid S tateS ub -B o o s te rA m p lif ie r

K L YS T R O N

Klystron Station 24-1, 2, and 3 Control for Feedback

L C L S C o ntro lS ys te mP o in ts

1/2 Heliax is 4dB / 100ft @ 3GHzL C L S C o ntro lS ys te m T C

S L E D

E xis ting P has eR e fe re nc e

Amp / S plitte r

RF CONTROL

CHASSIS Needed to be Built

S29 and S30 Phase Control (Two Units)The phase of sectors 29 and 30 will be adjusted in opposite directions to change the average amplitude of the RF as seen by the beam as it passes through the sectors without effecting the average phase as seen by the beam.

IQ M o dula to r4 7 6M Hz

Sector 29 and 30 Phase Control

L C L S C o ntro lS ys te m P o ints

M ain D rive L ine4 7 6 M Hz E xis ting P has e R e fe re nc e

L C L S C o ntro lS ys te m T C

AmpE xis tingS ub-B o o s te rD riv e Unit

To Sector Phase Reference and RF DriveRF CONTROL

CHASSIS Needed to be Built