The TTF2 / VUV-FEL Linac RF System · Digital I/O Detection mixer RF 1300 MHz LO 1300.25 MHz IF 250 kHz time amlitude • downconversion of cavity ﬁeld to IF frequency at 250 kHz

04

RF System

Ayvazyan / Simrock, DESY MAC Meeting, Nov. 9th 20

The TTF2 / VUV-FEL Linac

Outline

• Overview of RF System• High Power RF - Klystron - Modulator - RF Waveguide Distribution

• Low Level RF Control System - Configuration - Hardware - Software

• Summary


VUV-FEL RF System Diagram ACC1 ACC5 ACC4 ACC3 ACC2 ACC6 RF-Gun 3rd harm.

Mod 4 (10 MW)

Mod 5 (5 MW)

Mod 6 (10 MW)

Mod 7 (10 MW)

SMES

Mod 2 (5 MW) Mod 3 (5 MW)Mod 1 (5 MW)

Teststand Hall 2

For Test (Cavities,Couplers, Waveguides)

2 x 5 MW

3.3 MW3.3 MW3.3 MW

3.3 MW 6.7 MW


Klystrons• 5 MW Klystron THALES TH2104C• 10 MW Multi Beam Klystron THALES TH1801

Operation Frequency: 1.3GHzCathode Voltage: 117kVBeam Current: 131AMax. RF Peak Power: 10MWRF Pulse Duration: 1.5msRepetition Rate: 10Hz

The prototype has been in opera-tion at TTF since May 2000and has 14000h operation hours


ModulatorsThe FNAL Modulators

• 3 modulators delivered to TTF byFNAL since 1994

• They are continuously in operationunder different operation conditions

• Comprehensive maintenance duringshutdown, e.g. oil conditioning,cleaning and check of HV

• Improvement of subsystems (e.g. HVswitch, HVPS etc.) are continuing.They are ready for 10Hz operation

The FNAL Modulators


Modulators (2)Industry made Modulators(PPT Modulator)

• 2 modulators are in operation, have now complete remote controland new RF interlocks (simpler version of the interlock underdevelopment)

• Low leakage inductance pulse transformer (<200µH) resulting inshorter HV pulse rise time of <200µs

HVPS and Pulse Forming Unit Pulse Transformer


RF Power Waveguide Distribution• Distribution of klystron output power to the cavities• Protection of the klystron from reflected power• Control of phase and loaded Q

ACC1 ACC3ACC2

ACC4 ACC5


Cavity Loaded Q and Phase Adjustment

Motorized three stub waveguide tunersused to adjust phases and loaded Q forall cavities

- Improvement from to30°± 3°±


RF Control Requirements

• Amplitude and Phase Stability:

- amplitude

- for phase (fast fluctuations)

• Other requirements:- ACC1: cav. 1-4 at 12 MV/m, cav. 5-8 at 20 MV/m phase of accel-erating field -10.8 deg.- 3rd harmonic cavity at 14 MV/m at 183 deg.- S-Band cavity at 2856 MHz phase stability < 1 deg.- RF Gun operation without field probe. rep. rate, pulse length andpower must be variable.

σA A⁄ 104–<

σϕ 0.1°<

Gradient

Power

Detuning

TimePhase


RF Control Tasks List

Cavities to be controlled:

• RF gun

• Vector-sum of cryomodule 1

• 3rd harmonic cavity (3.9 GHz) (in 2006)

• Vector-sum of cryomodules in locations 2+3

• Vector-sum of cryomodules in locations 4+5+(6) (in 2006)

• S-Band cavity at 2.856 GHz

• Provide stable phase reference for laser, and diagnostics


Schematic of the Digital RF System

Tuner

Cavity 1

DirectionalCouplerForward

ReflectedRF

RF

RFLO

LO

LO

DSP/FPGADAC

DAC

I

Q

Tuner

Cavity 8

......8x

Tuner

Cavity 9

Tuner

Cavity 16

......8x

Cryomodule Cryomodule

Klystron Circulator

Power Transmission Line Power Transmission Line

ADC

ADC

ADC

VME

SUN

FieldProbe

IncidentWave

ReflectedWave

Power

Power

fref = 9.02775 MHz÷9

flofrf

frf = 144×fref ≅ 1300 MHz

flo = (144+1/36)×fref ≅ 1300.25 MHz

S&H

-1

TransientDetection

I/Q

VectorModulator

I Q

WaveguideTuner

1 MHz Clock

200kW

4×8 channelADC board14 bit @ 1 MHz

250 kHz

ADC

ADC

ADC


Digital I/O Detection

mixer

RF

1300 MHzLO

1300.25 MHz

IF250 kHz

time

amlitude

• downconversion of cavity fieldto IF frequency at 250 kHz

• complete phase and amplitudeinformation of the acceleratingfield is preserved.

• sample IF signal at 1MHz rate• subsequent samples describe

real and imaginary componentof the cavity field.

t0 t1

t2 t3

x0

x1

x2

x3


Control AlgorithmD

AC

DA

C

ReIm

Cavity 32......8x

Cavity 25

klystronvector

modulator masteroscillator

1.3 GHz Cavity 8......8x

Cavity 1

cryomodule 4

...cryomodule 1

. . . .LO 1.3 GHz

+ 250 kHz250 kHz

ADC

f = 1 MHzs

. . . . ...

vector-sumΣ( )ab

a -b

1 8( )ab

a -b

25( )ab

a -b

32( )ab

a -b

DSPsystemsetpoint

tablegaintable

feed

tableforward

++digital

low passfilter

ImRe ImRe ImRe

clock

LO

ADC

LO

ADC

LO

ADC

ImRe

power transmission line

1.3GHzfield probe

04

ware

annels for the control


Digital Feedback Hard• DSP System- New hardware, faster DSPs (C67), input ch

of 8/16/24 cavities- 8 channel ADC board- 8 channel DAC board- Gigalink interface between boards


Digital Feedback Hardware (2)

• Downconverter based on AD 8343• RF Gun detectors (forward and reflected power)- AD8347 IQ demodulator (for feedback)- Schotty diode for amplitude (redundant)- HMC precision phase detector (redundant)- AD 8302 for cavity detuning

Gun Control BoxDownconverters


Digital Feedback Hardware (3)

Gun and ACC1 ACC2, ACC3, ACC4 & ACC5

04

ware

oint, feedback gain and

face

rement, Loaded Q and


Digital Feedback Soft

• DSP System- Exception detection and handling

• DOOCS DSP Server- Parameter based operation, tables for setp

feedforward calculated by server

• DOOCS Finite State Machine Server- Automated operation, Simple operator inter

• Application tools- Adaptive feedforward, Beam phase measucavity detuning measurement...


0.02

0.04

0.06

0.08

30

210

60

240

90

270

120

300

150

330

180 0

Module 1 (ACC1*)

12345678

0.02

0.04

0.06

30

210

60

240

90

270

120

300

150

330

180 0

Module 1 (ACC1*)

1

2

34

567

8

0.02

0.04

0.06

30

210

60

240

90

270

120

300

150

330

180 0

Module 1 (ACC1*)

1

234

5

678

Beam Based Calibration- Good beam required to get sufficient signal (8nC, 30µs, 15MV/m)- Preliminary calibration (to 10%)- Gradient calibration (to 3-5%)


Exception Handling - Cavity quench detection mechanism (algorithms) - Exception handling procedure

Module 1* at high gradient1-st quench in Cavity 2 2-nd quench in Cavity 6 3-rd quench in Cavity 1 Eacc=19[MV/m] Eacc=21[MV/m] Eacc=24[MV/m]


Automation of RF Operation

- High degree automation of accelerator operation- Reduce workload of operators- Maximize availability of accelerator

Check/reset interlocks,Find source, check limits...

Adjust feedback loop,

Optimize beam parameters

High voltage is applied,

RF is not permitted

RF_ON

RF_STDBY

HV_ON

Start-up procedureIDLE

Graphical representation of logical dependencies


Master Oscillator and Frequency DistributionSystem

• Master Oscillator:- Required frequencies:50Hz, 1MHz, 9MHz, 13.5 MHz, 27MHz, 81MHz, 108 MHz, 1.3GHz,1.517GHz, 2.856GHz- Required stability:Within macro-pulse and between macro-pulses: 0.1psLong term: 1ps (minutes), 2ps (hours) 10 ps (days)

• Frequency Distribution:- Temperature stabilized coaxial distribution- Highly stable fiber optic monitoring system


Summary

• Commissioning of RF for TTF2 / VUV-FEL is well underway

• All main RF components (klystron / modulator / waveguide) havebeen successfully tested

• LLRF Control System is operational

• New Master Oscillator and frequency distribution are presentlybeing installed and commissioned

• Automation of RF operation under development

Documents

The TTF2 / VUV-FEL Linac RF System · Digital I/O Detection mixer RF 1300 MHz LO 1300.25 MHz IF 250 kHz time amlitude • downconversion of cavity ﬁeld to IF frequency at 250 kHz