LCLS LLRF System

LCLS LLRF System October 10-13, 2005

LLRF05

R. Akre, B. Hong, D. Kotturi, A. Hill, S. Heinz

SLAC, Stanford, Menlo Park, CA 94025, USA

Outline

Overview of LCLS Injector RF SystemLCLS RF Stability RequirementsLow Noise RF Distribution SystemRF Control and Monitoring SystemRF Vacuum InterlocksRF PPS Requirements

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% Unit

mean 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 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.

Low Noise RF Distribution System

LINAC RF meets all LCLS specifications for 2 seconds when running well, but it is out of LCLS specs in 1 minute.

New phase lock oscillator will reduce the noise floor in the RF System. See next page.

The improved RF and Timing Reference System at the front end of the main linac and the new RF and Timing System at the end of sector 20 for LCLS L0 and L1 will reduce phase noise levels and eliminate the phase and frequency shift on the main linac. ?

The laser will be phase locked to the cleaned up. ?

Phase Noise of SLAC Main Drive Line

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 H z R F3 6 0 H z F id uc ia lF ro m S e c to r 0 (2 km )

RF HUT Coupler476MHz 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 IN G R F

1 1 9 M H z 4 7 6 M H zO U T

T rac k/H o ld1 2 0 H z

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 H z 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 H zD ig itize r C lo c ks1 6 W ay D is trib utio 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 H z 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 H zL 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 H zM o nito r

Power Monitor

PowerMonitor

L A S E R D io d eP has e N o 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 SystemMain Drive LineMain Drive Line

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

Length = 31 Sectors, 15.5 furlongs Length = 31 Sectors, 15.5 furlongs 2miles, 3km, 2miles, 3km, 1e7 1e7 SS : Velocity = : 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, 400k400kSS in ½” Heliax 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

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

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

beam sees 3.5uS of RF from SLED.

RF Control and Monitoring System

Bandwidth of S-Band System Upper Frequency Limit – 10MHz

– Beam seen due to structure fill time ~ 1.2MHz– Structure RF Bandwidth ~ 16MHz– 5045 Klystron ~ 10MHz

Lower Frequency Limit – 100kHz– Fill time of SLED Cavity = 3.5uS about 100kHz– Laser – Needs to be measured ~ 100kHz

Bandwidth of X-Band System?

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 Sector

MDL 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 ulato 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

Klystron S ta tion 20-6

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

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


IQ D e mo dula to r

L O D is tributio 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 rTe mp Ana lo gC o 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


R FBeamPhaseC av ity


R F O u t

R F In

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

IQ D e mo dula to r

IQ M o dula to rF o r C a libra tio 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


IQ M o dula to r

TU N N EL

E xis ting P A D





IQ D e mo dula to r

K L YS T R O N

IQ D e mo dula to r

R F H U T


L O D is tributio n




A c c O u t

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

A c c In

L0-A

S L E D




RF MONITOR

RF MONITOR

RF CONTROL


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 Sectpr 25 transverse deflector cavity, respectively. The cavity is used to deflect the beam with 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 O D is tributio n

IQ M o dula to r





A c c In

TU N N EL



S L E D

E xis ting P A D


L0-T





IQ D e mo dula to r

K L YS T R O N

A c c O u t




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

T2

21-1C

RF

IN1

RF

OU

T2

21-1D

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



RF MONITOR

RF MONITOR

RF MONITOR

RF CONTROL


RF

IN1

RF

OU

T2



E xis tingIP A C ha s s is

IQ D e mo dula to r

IQ D e mo dula to r

L O D is tributio n

A c c B O u t

A c c B In

IQ M o dula to r



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



K lystron 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 @ 3GHz


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 HzR e fe 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 HzR e fe re nc eF ro m R F HUT

10dBm InMon Out

D is tributio n

IQ D e mo dula to r

IQ D e mo dula to r

10dBm In


Mon Out

A c c O u t

A c c In



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


RF

IN1

RF

OU

T2

TU N N EL

R F H U T

K lystron S ta tion 21-2

E xis ting w ith ne wR F H e ad


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


10dBm In


Mon Out

D is tributio n

?

?

L OF 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.



IQ M o dula to r

E xis ting P A D



K L YS T R O N

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


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

S L E D


Amp / S plitte r

RF CONTROL


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 6 M Hz

Sector 29 and 30 Phase Control


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


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

To Sector Phase Reference and RF DriveRF CONTROL


RF Vacuum Interlocks

This requirement involves klystron stations 20-5, 20-6, 20-7, and 20-8 where new sections of waveguide will be added.

The long runs of waveguide will have ion-pumps with controllers. An interlock sum output of the controllers will be provided to tie into the 24 volt interlock chain of the associated Modulator Klystron Support Unit, MKSU.

Separate status lines with latches need to be available to determine where faults originate.

Sector 20 RF - PPS Requirements

• In the main linac, all the klystrons will use the existing PPS system. For the klystrons operating the off axis injector in sector 20 the PPS system will require upgrades to allow access to the off axis injector during linac operation. Access to the linac will not be allowed during LCLS injector operation.

Documents

LCLS LLRF System