LCLS LLRF Reference R.Akre September 2, 2008

RF HUT Coupler Main Drive Line (MDL) MDL to Linac Sectors 21 to 30 476MHz Ref. 476MHz RF FSJ4-50 0.8dB/30ft PEP and Research Yard +1.3dBm in RF Hut 360Hz Fiducial From Sector 0 (2km) LCLS LLRF 476MHz Linac Ref. ZX60-3011 Amp ~16dB gain@476MHz NC LASER Reference NC LASER 476MHz NC Existing Sector 21 380-208-38 LKG26-36 4 x +10dBm out LSR SPAC LASER TIMING SYSTEM J15 J14 ROOM +7dBm in J15 FIDO Out 119MHz MDL 476MHz 380-208-40 LKG25-33 LASER Diode Output MDL SPAC 380-208-40 LKG26-33 RF Hut +13dBm out J14 VME BASED 380-208-?? LKG25-?? 13dBm in LCLS 476MHz PLL LASER PHASE LASER Diode Signal Processor Track/Hold Sample and Hold PLL FEEDBACK TRBR with DAC offset adjust 2856MHz and 119MHz LI20 TRBR 404 Trig 2 In and Error Monitor LKG26-24 20dB 119MHz 476MHz CH3 - LCLS 119MHz 10dBm OUT 380-208-29 16dBm OUT CH0 -2856MHz LSR PAD LKG25-36 LSR PAD 380-208-60 LKG25-36 LCLS VHF Dual Dist LASER 380-208-34 LKG25-30 2830.5MHz LO Gen CH2 -119MHz NC LSR PAD 4x 119MHz VHF2 4x 476MHz VHF1 380-208-28 LKG28-21 LKG25-36 119MHz Synchronizer 18dBm OUT 17dBm OUT LASER SINGLE Divide 112 to 25.5MHz CH1 -2856MHz PULSE 476MHz In SSB Mix to 2830.5MHz LSR PAD LKG25-36 MEASUREMENT 119MHz Out 385-011 LKG2117 4X to 102MHz EVG +13dBm in 2856MHz in 25.5MHz out +13dBm 25.5MHz in 476MHz to 2856MHz 102MHz out 2830.5MHz out CH2 - S21 119MHz MULTIPLIER X-Band LO Gen REF PAD 380-208-51 380-208-60 LKG26-21 +17dBm J15 J15 25.5MHz out LKG28-30 380-208-22 LKG26-27 out Clock - 102MHz Local Osc - S-Band L1X PAD J15 LCL SPAC CLK SPAC 21-2 Kly PAD L2 476MHz J15 L2 SPAC RF Reference - S-Band 380-208-40 LKG27-27 J14 380-208-40 LKG28-18 J14 380-208-40 LKG26-18 J14 RFR SPAC 2830.5MHz 380-208-40 LKG27-36 J14 102MHz VHF 5W Amplifier S-Band 10W Amp CH3 - 25.5MHz LKG26-21 L2 Amp 380-208-27 LKG28-15 REF PAD 380-208-60 2856MHz 380-208-26 LKG27-21 380-208-18 LKG26-16 S-Band 10W Amp 102MHz +17dBm out S21 S22 2830.5MHz -23dBm 380-208-27 LKG27-33 16 Way Dist 22dBm X-Band 4x S23 2.8-2.9GHz Distribution 380-208-21 LKG27-18 MULTIPLIER S24 380-208-20 LKG28-12 2856MHz -20dBm Gun 20-6 Gun1 PAD L0A 20-7 Gun2 PAD Gun 20-6 Gun1 PAD L1S PAD +6dBm in 2.8-2.9GHz Distribution L0B 20-8 L0A/B PAD L0A 20-7 Gun2 PAD L1X PAD 380-208-50 LKG28-36 380-208-20 LKG27-30 TCAV0 20-5 TCAV0 PAD L0B 20-8 L0A/B PAD Ref PAD L1S 21-1 L1S PAD TCAV0 20-5 TCAV0 PAD LASER PAD Gun L1X 21-2 L1X PAD L1S 21-1 Linac PCAV1 PAD L0A LASER PAC Ref PAD L0B PCAV1 PAD LASER PAD L0TCAV L1S CH0 - 2856MHz REF PAD 380-208-60 LKG26-21 2856MHz from CH1 - S21 2856MHz Sector 21 SBDU REF PAD LKG26-21

Figure 1. LCLS Sector 20 LLRF distribution system FS-714-114-10-C0

The LLRF distribution system is shown in figure 1. The 476MHz is picked off the Main Drive Line (MDL), amplified and used as a reference for a PLL. The LCLS 476MHz PLL is used to track the linac RF reference during LCLS beam time and hold the reference during PEP phase shifts on the MDL. The output of the 476MHz PLL drives a 6 times multiplier to generate 2856MHz. The 2856MHz is then divided down to 25.5MHz which is Single Side Band (SSB) mixed to generate the 2830.5MHz Local Oscillator (LO). The LO is used to down mix the 2856MHz RF to an Intermediate Frequency (IF) of 25.5MHz. The IF is then digitized with a sample rate of 102MHz. The 25.5MHz generated from the dividers is multiplied by 4 to generate 102MHz used for the digitizer clocks. The goal of the RF distribution system is to achieve the LCLS specifications on the RF phase and amplitude as seen by the beam. LCLS LLRF 476MHz Main Drive Line Amplifier

476MHz is picked off the Main Drive Line (MDL) at sector 20 down stream of the expansion joint and upstream of the sector 21 anchor. At this point, the 476MHz has noise floor of -153dBc/Hz with signal level at +2dBm the noise floor is at -151dBm/Hz, 23dB above the thermal noise level.

The following 2 Minicircuits amplifiers were initially designed to be used in series figure 2. The power level was sufficient to eliminate the second amplifier and use only the ZX60-3011 with no attenuation. The output levels of the chassis are +10dBm in this configuration.

Input Power ZX60-3011 -5dB PAD ZHL-2010 4 Way Splitter NF 10dB 2.5dB 5dB 3.5dB 6dB Out Op point -11dBm 5dBm 0dBm 22dBm 16dBm P1dB 21.4dBm 30dBm IP3 31dBm 46dBm Gain 10dB eq 16dB -5dB 22dB -6dB NF Contribution 0.25dB 0.19dB 0.17dB 0.14dB Total added Noise = 0.75dB base on noise power at input of -164dBm/Hz Chassis NF 2.5dB 0.31dB 0.32dB 0.18dB Chassis NF Total 3.31dB

Noise Floor at output of amplifier chassis is -142dBm/Hz at 476MHz.

Field Determined ZHL-1010

+10dBm 476MHz FP-N REMOVED 04/08

476MHz from MDL ZX60-3011 476MHz RP-N

RP-N 476MHz RP-N +1dBm +17dBm +17dBm

476MHz RP-N ZFSC-4-1 Figure 2. 476MHz Linac Ref. WD-380-208-38-C0 SPAC, Slow Phase and Amplitude Controllers

There are 6 slow PACs used in the reference system.

1. MDL 476MHz - controls the phase of the laser, injector, L1, L2, and timing system.

2. Laser 476MHz - controls the RF reference which the laser oscillator locks to.

3. RF Reference 2856MHz - controls the phase of the RF to the RF reference distribution and to the Local Oscillator, LO, generator.

4. LO Reference 2830.5MHz - controls the phase of the Local Oscillator distributed to the PADs.

5. Clock 102MHz - controls the phase of the 102MHz clock distribution used to clock PADs and PACs.

6. L2 Reference 476MHz - controls the phase of the 476MHz reference which feeds linac sectors 21, 22, 23, and 24.

All the PACs use the PAC control board which has an Arcturus uCDIMM Coldfire based module running EPICS on RTEMS. The uCDIMM is used to setup and load waveforms into the Spartan FPGA. The FPGA is programmed as 2 arbitrary 2048 sample arbitrary waveform generators. In the SPAC mode, the waveforms are constants and written to the 2 DACs when changed through EPICS. The 2 DACs output voltages to the I and Q channels of the modulator. There are two types of RF heads used in the PACs. One is an S-Band module with built in amps, couplers and IQ modulator, figure 3. The other is a VHF unit which covers 102MHz and 476MHz and is made with connectorized amplifiers, couplers, splitters, mixers and filters mounted on a plate, figure 4. The S-Band chassis takes -3dBm input and outputs up to +7dBm. The VHF unit takes +7dBm input and has an output of up to +13dBm.

ACCELERATE STANDBY TRIGGER CLOCK TRIGGER TRIGGER 120Hz 120Hz SSSB SSSB 119MHz Monitor TTL Gate Monitor Chassis RP BNC RP N FP BNC RP BNC Ext Trig J12 Trig 2 J16 FP BNC RP 15 Pin D RF INPUT RF OUTPUT RF OUTPUT Monitor Monitor To SSSB I MONITOR Q MONITOR FP N FP N RP N FP BNC FP BNC

H9 H10 J3 J2 H7 J10 SSSB H6 P5 RF Module Trig TTL 17 to 30uS MATCHING FILTER NETWORK

3 16bit DATA

16 bit E

Amp I T I I&Q MODULATOR DATA I H Amp 1 CLK XILINX CONTROL / 2856MHz Ref MAX5875 E 2 RF LO J5 -3dBm 2 X 16 bit DAC SPARTAN 3 Arcturus uC5282 R N

RP N Q 119MHz Clock FPGA Microcontroller Module E

16bit DATA T (1MHz to 200MHz) CS/

4 Q CLK with 10/100 Ethernet Q CLK E R T MATCHING J4 A H W

FILTER E

NETWORK R

AD8099 Diff Amp N E T Control Control C O M

Temperature SLOW ADCs t Monitor Temperature H12 PAC Temp Monitor t IQ Temp SSSB Temp SSSB P-FWD RF INPUT NC SSSB P-RFL Monitor SSSB PWR +5V Control Board Diode -12V FP BNC

Figure 3. S-Band (2856MHz or 2830.5MHz) PAC Chassis FS 380-208-40-C0 TRIGGER EXTERNAL CLOCK Monitor TTL TRIGGER 120Hz SSSB SSSB 119MHz FP BNC Gate Monitor Chassis RP N 60nS NIM RP BNC FP BNC RP 15 Pin D

RF INPUT RF OUTPUT I MONITOR Q MONITOR Monitor Monitor RF OUTPUT FP BNC FP BNC FP N FP N RP N H9 H10 J2 H7 J3 SSSB H6 P5 Trig RF Module F4 ATT1 TTL 90 deg Phase 17 to 30uS VAT-10 Shift SLP-1.9 with 102 or Cable M3 16bit DATA

16 bit E 476MHz ZX30-12-4 ZFSC-2-1W F I ZHL-1010 CPL9 ZX60-4016E I DATA T RP N ZX30-12-4 LO RF -6dBm 14dBm I CLK XILINX CONTROL / H ZX30-12-4 J5 MAX5875 E 7dBm 17dBm 16dBm 15dBm ZP-2MH ZP-2MH 2 X 16 bit DAC SPARTAN 3 Arcturus uC5282 R CPL8 ZFSC-2-1W N LO RF 119MHz Clock FPGA Microcontroller Module E 12dBm -6dBm 16bit DATA T

F CS/ I (1MHz to 200MHz) M4 with 10/100 Ethernet F5 Q CLK PE8000-50 0dBm ATT2 Q CLK E R T J4 A H W E

VAT-10 R

SLP-1.9 AD8099 Diff Amp N E

Temperature T Monitor t Control Control C O M

RF INPUT Monitor Temperature SLOW ADCs Diode t Monitor FP BNC H12 PAC Temp IQ Temp SSSB Temp SSSB P-FWD SSSB P-RFL SSSB PWR +5V Control Board -12V

Figure 4. VHF (476MHz or 102MHz) PAC Chassis FS 380-208-40-C0 LCLS 476MHz PLL

ZP-2MH-S+ 10dBm RP-N J12 476MHz from MDL RF LO F 3dB I ZP-2MH 13dBm LO 10-16dBm 50MHz to 1GHz IF DC to 1GHz Typical LO-RF and LO-IF iso = 47dB J8 Sig In Conversion Loss = 6dB FP-BNC J3 120Hz TRBR Mon J15 Trig1Out PLL Feedback RP-BNC J8 120Hz TRBR In J11 Trig1In SD-714-114-60-C2 Track and Hold Track and Hold Amp FP-RJ45 J5 Ethernet J13 Ethernet DC Offset Digital 4uV minimum step in 10V range Error Output 40nV/sqrtHz noise floor - 10kHz BW FP-9 pin D J6 COM Port P1 COM 2.5e6 steps = 22 bit device Reduce range to 100mV plus offset RP-BNC J7 Trig2 In J12 Trig2In Board Input Power 100mV/4uV = 25k = 15bit system +5VD @ 650mA FP-BNC J4 Trig2 Out J16 Trig2Out +5VA @ 250mA -5VA @ 60mA J5 I Out

+13dBm C RF ZFSC-4-1 +16dBm

500-14299B 119MHz ULN ZHL-1010 ZX30-12-4 Quadrupler +12dBm +23dBm 476MHz FP-N J1

+12dBm LNDQ-119-12-12 476MHz RP-N J10 ZFL-2HAD ZHL-1010 +-5V = -+0.8ppm Sensitivity 12V 525mA Max error 30fS = 5mdeg @476MHz 15V 110mA 476MHz RP-N J11 21.7dBm P1 30dBm P1 5mdeg / 15mS = 1/3 deg/S = 0.9mHz 46dBm IP3 0.9mHz/476MHz = 2e-12 33dBm IP3 11dB Gain 10V/1.6ppm x 2e-12 = 12uV 12dB Gain 12uV error allowable on control signal NF 5.9dB NF 3.3dB Should have step size of < 4uV VSWR IO 1.02 1.28 VSWR IO 1.6 50-1000MHz +10dBm Bandwith ~ 5kHz to 20kHz ZFL-2HAD 50-1000MHz ZFSC-2-1W +1dBm 119MHzFP-N J2

+13dBm 119MHzRP-N J9 Figure 5 LCLS 476MHz PLL WD380-208-29C0

The amplified 476MHz from the MDL feeds the LCLS 476MHz PLL, shown in figure 5. The track and hold PLL supplies the LCLS LASER with a clean 476MHz signal, taking out the 720degree phase shifts in the linac RF used to fill different PEP buckets and the effects of the 360Hz fiducial. This type of track and hold has been used in SPPS to achieve Beam to RF noise levels of less than 150fS rms jitter as measured by the SPPS EO experiment. The 119MHz Ultra Low Noise (ULN) oscillator has output noise floor of -176dBc/Hz. The oscillator specification is shown in figure 6. A TRBR trigger from LI20 404 is connected to the "Trig 2 In", J7 BNC, on the PLL chassis to trigger the sample start time. Figure 6. 119MHz Low Noise Oscillator

The noise floor at the output of the quadrupler is expected to be about 3dB higher plus 12dB from multiplication, -161dBc/Hz. The amplifier and output dividers will add less than 1dB of noise to the floor. The output noise floor at 476MHz should be below -160dBc/Hz. LCLS VHF Dual Distribution

+13dBm VHF2 Out FP-N

VHF2 IN ZHL-2010 VHF2 Out RP-N

RP-N ZHL-1010 VHF2 Out RP-N 0dBm +20dBm 12V 525mA Field Determined 30dBm P1 VHF2 Out RP-N 46dBm IP3 ZB4PD1-500-S 11dB Gain NF 3.3dB VSWR IO 1.6 ZHL-2010 +17dBm 50-1000MHz VHF1 Out FP-N 12V 0.9A 30dBm P1 46dBm IP3 VHF1 IN ZHL-1010 VHF1 Out RP-N 22.4dB Gain RP-N VHF1 Out RP-N NF 3.35dB 13dBm +23dBm VSWR IO 1.16-1.19 Field Determined 50-1000MHz VHF1 Out RP-N ZB4PD1-500-S Figure 7. LCLS LLRF VHF Dual Dist. Chassis WD-380-208-34-C0

The LCLS Dual Distribution Chassis is used to fan out the outputs of the 119MHz and the 476MHz from the LCLS 476MHz PLL Chassis. The schematic is shown in figure 7. VHF1 channel is used for the 476MHz signal and the outputs are about +17dBm. VHF2 channel is used for the 119MHz signal and the outputs are about +18dBm.

The input 119MHz noise floor is about -168dBc/Hz. The output noise floor will increase 5dB due to the input 10dB attenuator and by about 1dB due to the amplifier to give an output noise floor of -162dBc/Hz. The 119MHz outputs feed the Laser and the Reference PAD.

The input 476MHz noise floor is about -160dBc/Hz. The 6dB input attenuator and the amplifier will add 2dB to the noise floor, raising it to about -158dBc/Hz. The 476MHz outputs feed the Laser, the 6X multiplier, and the Timing 119MHz Synchronizer. 476MHz to 2856MHz Multiplier

The 476MHz to 2856MHz multiplier is expected to add 16dB to the noise floor, mostly due to multiplication by 6. The output of 2856MHz noise floor is expected to be below -144dBc/Hz. Figure 8 is the drawing for the multiplier and a photo of the RF section in the chassis.

+18dBm 476MHz RP-N J1 +13dBm in +9dBm out 2856MHz RP-N J2 +17dBm out ZX60-3011 +12V 120mA -20dB Wenzel LNFM-476-6-13-9 +20dBm P1 2856MHz FP-N J3 +32dBm IP3 -2dBm out 9.6dB Gain NF 1.8dB VSWR I 1.7 O 1.8 400-3000MHz

Figure 8. 476MHz to 2856MHz Multiplier FS-380-208-22-C0 S-Band 10W Amp - Distribution Amplifier

An SPAC, Slow Phase and Amplitude Controller, chassis contains an IQ modulator and is used to control the phase and amplitude of the RF feeding the distribution amplifier. The output of the distribution amplifier feeds the 16 way distribution chassis. There are two amplifiers used in the sector 20 RF system, one for the RF, 2856MHz, and another for the LO, 2830.5MHz distribution. Specifications for the amplifier are listed below, and the chassis diagram is shown in figure 9.

Model number AM38A-2.85S-35-40 from Microwave Amplifiers Ltd.

Frequency Range (GHz): 2.800 to 2.900 Gain Small Signal: 35dB min Gain Flatness: 1dB p-p max RF Input Drive: +15dBm max Output Power @ 1dB GCP: +40dBm min IP3 +50dBm typ Non-Harmonic Spurious: -60dBc min Noise Figure @ 25º C: 4dB typ Output Return Loss: 10dB min, 14dB typ Input Return Loss: 10dB min, 14dB typ Power Supply: +12/15V DC, 3.5A max Connectors: SMA Female Dimensions (LWH): 150x70x25mm Operating Temp Range (baseplate): 0 to +60C

Features:

Class A Linear Design Unconditional stability Reverse polarity protection Open & short circuit protection Over temperature protection

The amplifier will be run at an output power level of 33dBm and maintain the noise floor below -144dBc/Hz.

+35dBm out 0dBm in Pulsar CS10-05-436/10 Pulsar CS20-05-436/10 2856MHz RP-N J3 2856MHz RP-N J4 AM38A-2.85S-35-40 AM38A 10W Amp - 35dB gain +12V 3.2A -20dB +40dBm P1 2856MHz FP-N J2 35dB Gain +15dBm out 2856MHz FP-N J1 RL I 20dB O 14dB 2.8-2.9GHz

Figure 9. S-Band 10W Amplifier FS-380-208-27-C0 2830.5MHz Local Oscillator Generator

ZFSC-2-2 FRONT PANEL N J3 25.5MHz +13dBm 25.5MHz J5 +17dBm REAR PANEL N 0dBm -4dBm +10dBm 0dBm ZFSC-2-2 HMC-C007 /8 LNPDN-14-10-E-0-25.5 1 +23dBm REAR PANEL N 2856MHz in 358MHz in 2 S 2 102MHz J7 S 1 4 x 10dBm in 358MHz out 25.5MHz out 25.5MHz to 102MHz BX5122PM BXMP1003 ZMSCQ-2-50 102MHz 5V 100mA 15V 200mA 6dB LNVQ-25.5-10-10-1 15V 65mA 24V 425mA ZFSC-2-2 REAR PANEL N J6 15V 40mA +7dBm

CAP PI NETWORK +20dBm +11dBm +16dBm F5 SLP-30 90 0

0 25.5MHz 90 deg Hybrids JSPQ-80 ZMSCQ-2-50 JYPQ-30 DC Block JSPQ-80 - BEST!!! J4 REAR PANEL N 2856MHz In +V 1 2 -3dBm 3 + - 15V 4mA 10dB 10dB -V

25.5MHz DIPLEXER Balancing Hybrid

FRONT PANEL N J1 8V @ 65mA 0dBm 2830.5MHz F with regulator I LO RF -6dBm

REAR PANEL N 8dBm J9 2830.5MHz

LO RF 8V @ 65mA F I with regulator REAR PANEL N J8 DIODE 2830.5MHz Test DETECTOR 3.3V 2856MHz to 2830.5MHz SSB IQ Modulator

DC 0 to 1 Volt J2 FRONT PANEL BNC In Diode Det

Figure 10. 2830.5MHz LO Generator Block Diagram FS-380-208-28-C0

The 2830.5MHz LO Generator block diagram is shown in figure 10 and a picture of the chassis in figure 11. The noise floor of the 2856MHz feeding the chassis is -144dBc/Hz. The divider output at 25.5MHz is -150dBc/Hz. At 102MHz this is expected to increase by 12dB to -138dBc/Hz.

102MHz noise floor is -138dBc/Hz : -138dBc/Hz x 50MHz x2 SSB = -58dBc -58dBc is 0.072degs rms or at 102MHz is 2pS rms jitter.

2pS clock jitter on 25.5MHz signal can add -70dBc to the SNR At 2856MHz -70dBc is 0.32mRadians rms, 0.018Degrees rms, or 18fSrms.

The 102MHz feeds the Clock SPAC, which feeds the VHF 5W Amplifier, which feeds the 16 Way Distribution Chassis. The 16 way distribution chassis fans out the clock to all PADs and PACs in sector 20 and sector 21.

The 25.5MHz signal is routed to the X-Band LO Generator where it is used to SSB generate an LO signal for the X-Band PADs. 2830.5MHz Noise Floor

The noise floor of the 25.5MHz is about -150dBc/Hz. This level should easily be held all the way to the IF port of the mixer where the level is about 0dBm. At this point the 25.5MHz mixes with the 2856MHz in a single side band modulator. The -150dBc/Hz is expected to add 1dB to the 2856MHz input noise level of -144dBc/Hz. This gives the 2830.5MHz a noise floor of -143dBc/Hz.

The RF and LO noise levels of about -143dBc/Hz, an IF mixed product is expected to have a noise level of -140dBc/Hz. In a 10MHz bandwidth the noise level would be -67dBc. This is equivalent to a jitter of 26fS rms.

Figure 11. 2830.5MHz LO Generator Chassis FS-380-208-28-C0 L2

L2, LCLS linac 2 between BC1 and BC2, consists of linac klystrons 21-3 to 24-6. The 4 sectors of linac get their 476MHz RF reference from the L2 Amp chassis, shown in figure 12. The 6dBm coupled output is used to supply the reference to sector 21 through a piece of 1/2 inch heliax. The main, 16dBm, output drives a 7/8 inch heliax run through the tunnel to sector 24. Couplers in the 7/8 inch heliax pick off power for sectors 22 and 23. The L2 amplifier is feed from the L2 SPAC.

10dBm max ZHL-1010 16dBm out from L2 PAC ZX30-12-4-S ZX30-12-4-S 476MHz RP-N 476MHz RP-N 18dBm 17dBm -12dB -12dB 5dBm out 476MHz FP-N

6dBm out 476MHz RP-N Figure 12, L2 Amp FS-380-208-18-C0 Appendix A

Synchronization of RF Signals wrt Timing Fiducial

Signals of interest: Multiple of 25.5MHz 25.5MHz to generate 2830.5MHz LO for LCLS RF measurements 1 102MHz clock for ADCs and DACs 4 119MHz clean LCLS 119MHz for Laser reference 14/3 119MHz linac locked to fiducial 14/3 119MHz lcls timing system synchronized to linac 14/3 476MHz linac MDL phase distribution 56/3 476MHz LCLS 476MHz PLL used for laser locking 56/3 2830.5MHz LCLS LO to measure phase 111 2856MHz RF 112 11.4GHz RF 448

Every three 25.5MHz cycles, 8.5MHz, all phases line up

There are three items that need to be resynchronized in the RF distribution system: 1. The 119MHz to the laser which can be off by a 476MHz bucket (this has the timing systems 476MHz reference as a harmonic) 2. The 25.5MHz which can be off by a 2856MHz bucket. 3. The laser oscillator which can be out by a 476MHz Bucket.

Following the below items in the presented order to get back to operational conditions.

Turn off any feedback driving the LASER PAC and MDL PAC.

MDL PAC - 119MHz Linac

The MDL PAC shifts the phase of the LCLS injector and L1 RF with respect to the MDL. Since this phase shifter is used to adjust the injection phase into L2, there is a feedback that may move this by as much as ±180 degrees at 2856MHz, or ±30 degrees at 476MHz. The reference 476MHz to the timing system also passes through this phase shifter. This is the first item which needs to be checked since it can shift the phase of the 476MHz going to the timing system. Turn off any feedback driving the MDL PAC. Rotate the phase so that I is about -32000 +-5000 and Q about 0 +-5000. These numbers are good as of April 22, 2008. You should check the archiver and/or MDL PAC window to verify these numbers are close to the operating point.

25.5MHz

The 25.5MHz is generated by division of the 2856MHz by a divide by 112. The 25.5MHz is used to generate the 102MHz clock frequency and the 2830.5MHz local oscillator. For the PADs to read the correct phase, the 102MHz clocks and the 2830.5MHz local oscillator must be at the correct phase with respect to the trigger system. This is accomplished by rotation of the RF Reference phase shifter while monitoring channels 2 and 3 of the Reference PAD.

The two Reference PAD signals used to set up this phase are channel 2, 119MHz FIDO, and channel 3, 25.5MHz. Both signals are viewed from the "Global", "Reference" window, figure A1, first row in the Phase & Amplitude section.

Figure A1, Global Reference Window

The 25.5MHz, since it is divided down from 2856MHz, can be off by a 2856MHz cycle. Resolution of measurement needs to be below 350pS, 3.2 degrees at 25.5MHz or 15 degrees at 119MHz.

Since, the phase of the 102MHz digitizer clock will move with the phase of the 25.5MHz, you will not see the movement of the 25.5MHz phase on Channel 3 of the Reference PAD until it jumps a 119MHz trigger cycle. This will occur about every 28 revolutions.

Alignment of the 25.5MHz is done by full cycle rotations of the RF Ref PAC. First monitor channel 3, 25.5MHz, of the Reference PAD and rotate the RF Ref Phase with the LLRF GUI, Figure A2, to get to 0±3 degrees. Next monitor channel 2, 119MHz FIDO, on the Reference PAD and rotate the RF Ref phase shifter to get to 0±15 degrees. The 25.5MHz is now synchronized to the linac fiducial.

Figure A2, LLRF GUI

102MHz

If the 25.5MHz is synchronized to the linac fiducial, the 102MHz will be synchronized since it is a harmonic. 119MHz Linac

The linac 119MHz is locked to the linac fiducial and the linac timing system. The 25.5MHz adjustment uses this signal as a reference to ensure the LCLS RF is synchronous.

119MHz LCLS The 119MHz out of the LCLS local oscillator chassis is used for the laser system. The phase can be read from the LASER PAD CH3 "LCLS 119MHz". To synchronize this to the linac fiducial, rotate the MDL PAC one cycle one direction and the RF Ref PAC six cycles the other direction. Both these PACs need to be rotated in a ration of 1:6 to maintain the 25.5MHz phase to fiducial. During rotation of the MDL PAC, the reading on channel 3 of the LASER PAD will not change. This is due to the PAD clock moving with the signal.

476MHz MDL and LCLS The 476MHz of the LCLS local oscillator is phased locked to the main drive line of the linac to which the timing fiducial is synchronized.

The LASER 119MHz to Linac 119MHz The Laser 119MHz needs to be synchronized to the Linac 119MHz so the laser does not jump 476MHz buckets. This will be done by changing the laser feedback to lock to the Laser 119MHz phase.

To Finish

Turn on the laser feedback and MDL PAC feedback.

Matlab - RF Sync GUI The Matlab "RF Sync GUI" when run will perform the above steps and sync the RF system. The GUI is shown in figure A3. Figure A3, RF Sync GUI Appendix B RF Cables

The stability of the RF cables is expected to cause larger errors in phase measurement than any other components. The expected errors are tabulated below given in total phase change range based on the length of cable and the surrounding temperature in each environment. The Laser cable routing has been changed to go directly from the RF Hut to the Laser Room through the gallery in a temperature stabilized conduit. The length of the conduit is about 12 ft and the temperature variations are expected to be within ±0.2ºF.

Temperature Coefficient of 2.8ppm/ºF and Cable length is 1200ºS/ft All Cables except LASER are less than 100ft New Laser run is 53ft Distances feet and errors in degrees S total range RF Hut Down Linac Wall Injector Total Unit Ft degS ft degS ft degS ft degS ft degS DegS Laser 8 0.054 25 0.017 10 0.014 10 0.007 85 0.58 0.68 Gun 8 0.054 25 0.017 10 0.014 10 0.007 40 0.27 0.37 L0-A 8 0.054 25 0.017 10 0.014 10 0.007 30 0.21 0.31 B Phas 8 0.054 25 0.017 10 0.014 10 0.007 20 0.14 0.24 L0-B 8 0.054 25 0.017 10 0.014 10 0.007 20 0.14 0.24 L0-T 8 0.054 25 0.017 10 0.014 10 0.007 10 0.07 0.17 L1-S 8 0.054 25 0.017 50 0.068 0.14 L1-X 8 0.054 25 0.017 60 0.081 0.16 Laser2 8 0.054 15 0.021 30 0.21 0.29

Temperature Variations: RF Hut ±1ºF : Penetration ±0.1ºF : Linac : ±0.2ºF Shield Wall ±0.1ºF : Injector ±1ºF : Laser Room ±1ºF Distribution of Cables

Trig LCLS RF HUT TRIG from PAC 2830.5MHz LO Amp / Splitter ??dBm Comm Terminal Server TCAV 20-5 -3dBm LO ETH1 Ethernet ETH2 Ethernet for Fast Feedback RF Gun 20-6 PAD L0A 20-7 CH1 From Klystron Drive Coupler L0B 20-8 CH0 PAC OUT

L1S 21-1 CH2 KLY BEAM Voltage CH3 L1X 21-2 Klystron Forward 102MHz Clock In Out LCLS RF HUT 240ft = 2.5dB 1/2 Superflex 15dBm 102MHz Clock 8dBm Amp / Splitter = 1.6dB LDF4 FP test = 3dB LDF1 TCAV 20-5 18dBm 20dBm outputs RF Gun 20-6 3dB Splitter L0A 20-7

L0B 20-8

L1S 21-1

L1X 21-2 12dBm 102MHz Clock In LCLS RF HUT SSSB 2856MHz RF PAC Amp / Splitter 240ft = 17dB 1/2 Superflex = 10dB LDF4 -3dBm Coupled Out TCAV 20-5 In 2856MHz Out 17dBm In 2856MHz Out IPA RF Gun 20-6 SSSB Control Control & Monitor L0A 20-7 GATE GATE from BCS Trig F.P. J6 L0B 20-8 Front Panel Trig to PAD Comm J9 Terminal Server L1S 21-1 ETH1 J10 Ethernet J8 L1X 21-2 ETH2 Ethernet for Fast Feedback 140ft = 25dB 3/8 Superflex Ext Trig J12 Accelerate TRIG RF HUT Trig 2 J16 Standby TRIG KLYSTRON STATION

Distribution of RF signals to klystron stations. All of these cables are within local feedback loops. Linac Sector 0 RF Number of cables per device MDL Reference cables are 8ft and can drift +-50fS

L0, L1 - 5 Klystrons 476MHz PLL Cable Drift Based on Specifications 2830.5MHz LO Temperature variations Most Devices Amp / Splitter are in tunnel 100fS rms jitter PAD and temp co of 5ppm/degC +-2.3pS drift Laser 1 Laser +-290fS Laser

RF Gun 5 RF Gun +-370fS RF Gun L2 - 4 Sectors 2 +-310fS Specifications L0A L0A L0A 70fS rms jitter 2 +-240fS +-5pS drift Phase Cavity Phase Cavity Phase Cavity

L0B 2 L0B +-240fS L0B L3 - 6 Sectors 4 +-140fS L1S L1S L1S Specifications 150fS rms jitter 2 +-160fS L1X L1X L1X +-5pS drift 1 +-500fS L2 Ref L2 Ref L2 Ref

RF HUT The outline of RF phase reference system to PAD and device to PAD is shown above. Phase errors due to long term drifts are listed. The drifts listed above are calculated from temperature variations and assume that creeping of the cable is minimal.