Status of the RF SystemS. Choroba, DESY

• XFEL RF Requirements• RF Station Layout• Status of the RF Components

– Klystron– Modulator– HV Pulse Cable– RF Waveguide Distribution

• Summary

XFEL RF RequirementsNumber of sc cavities: 960 total Power per cavity: 120 kWGradient at 20GeV: 23 MV/m Power per 32 cavities(4 cryo modules): 3.9MW Power per RF station: 5.2MW (including 10% losses in

waveguides and circulators and a regulation reserve of 15%)

Number of RF stations: 30 (27 active)Number of RF stations forinjectors: 5Macro beam pulse duration: 650µsRF pulse duration: 1.37msRepetition rate: 10Hz (50Hz) Average RF power per station: 71.2kW (150kW)

Layout of the RF-System

Multi Beam Klystron THALES TH1801 Measured performanceOperation Frequency: 1.3GHzCathode Voltage: 117kVBeam Current: 131ANumber of Beams: 7Cathode loading: 5.5A/cm2

Max. RF Peak Power: 10MWRF Pulse Duration: 1.5msRepetition Rate: 10HzRF Average Power: 150kWEfficiency: 65%Gain: 48.2dBSolenoid Power: 6kWLength: 2.5mLifetime: ~40000h

Multi Beam Klystron THALES TH1801 cont.

• 4 klystrons have been manufactured• The prototype PT has been in operation at TTF since May 2000

and has now 20000h operation hours• Series klystron #1 has been returned to the vendor after ca. 3000h

(gun arcing)• Series klystron #2 has been tested and returned to the vendor• Gun arcing has been investigated, the problem is identified and the

klystron has been modified• Modified klystron #1 has been sent back to DESY after successful

factory test and will be installed at TTF (if final test at DESY issuccessful)

• New klystron #3 is being tested at Thales and will be shipped to DESY in Zeuthen (if test is successful)

• More klystrons have been ordered

Multi Beam Klystron CPI VKL-8301

Design Features:•6 beams•HOM input and output cavity•Cathode loading: <2.5A/cm2

lifetime prediction: >100000h

Status:•Klystron has been succesfullytested at CPI in January 2005•Klystron is now at DESY and will be tested soon

The TOSHIBA E3736 MBKin cooperation with KEK

Design Features:•6 beams•Ring shaped cavities•Cathode loading: <2.1 A/cm2

Status:•Klystron has been testedsuccessfully up to 10MW peak, 1ms, 10Hz•Modulator needs modification foroperation at full pulse width•Test will continue at Toshiba in June/July 2005

Horizontal Klystron

• Next step: Modification towards a horizontal version• Horizontal klystrons are already in use e.g. the LEP

klystrons at CERN or the B-factory klytrons at SLAC• One vendor has already made a conceptual design of

a horizontal version• Final specification including all interfaces is pending,

prototypes must be built• Goal: test 2-3 horizontal prototypes within 2 years

Klystron Status Summary• Multi beam klystrons have been in use at TTF since

2000, gun arcing has been investigated, the problemhas been identified and modifications have beenmade

• 3 vendors have already manufactured or are near to manufacture klystrons meeting the XFEL klystronrequirements

• Lifetime of the klystron is expected to be >40000h limited by cathode lifetime, for cathode currentdensities <2.5A/cm2 the lifetime might be >100000h

• Specification, layout and construction for horizontal tunnel installation is pending

Modulators• Modulators must generate HV pulses up to 120kV

and 140A, 1.57ms pulse length and 10Hz (50Hz) repetition rate

• The top of the pulse must be flat within 1% • The bouncer type modulator with its simple circuit

diagram was chosen

The FNAL ModulatorWaveforms

•3 modulators have been developed, built and delivered to TTF by FNAL since 1994

•They are continuosly in operationunder different operation conditions

FNAL Modulator at TTF

Industry made Modulator

IGCT Stack

HVPS and Pulse Forming Unit•Industry made subunits (PPT, ABB, FUG, Beerwald)

•Constant power power supply forsuppression of 10Hz repetition rate disturbances in the mains

•Compact storage capacitor bankwith self healing capacitors

•IGCT Stack (ABB); 7 IGCTs in series, 2 are redundant

Industry made Modulator cont.•Low leakage inductance pulse transformer (ABB) L<200µH resulting in shorter HV pulse rise time of <200µs

•Light Triggered Thyristorcrowbar avoiding mercury of ignitrons

Pulse Transformer

KlystronVoltage 113kV

Klystron Current 132A

Modulator Status• 10 Modulators have been built, 3 by

FNAL and 7 together with industry

• 8 modulators are in operation

• 10 years operation experience exists

• Many vendors for modulatorcomponents are available

Modulator Status cont.Next Steps:

• Continue investigation of modulator operationat higher rep. rate up to 50Hz while keepingthe klystron average input power constant (at DESY Zeuthen)

• Write specification of modulator/pulse transformer for hall/tunnel installation(modular layout with low MTTR, higherMTBF, low EMI) and find vendors responsiblefor entire modulator

• Goal: test 2-3 full prototypes within 2 years

HV Pulse Cable• Transmission of HV pulses (10kV, 1.6kA, 1.57ms,

10Hz (50Hz)) from the pulse generating unit(modulator hall) to the pulse transformer (acceleratortunnel)

• Maximum length 1.5km

• Impedance of 25 Ohms (4 cable in parallel will give6.25 Ohms in total) to match the klystron impedance

• Triaxial construction (inner conductor at 10kV, middleconductor at 1kV, outer conductor at ground)

HV Pulse Cable cont.

diameter 30mmdielectric material: XLPE

HV Pulse Cable cont.

• Prototype cable has been delivered and and first test has been successful

• Experience with similiar cables in Europe and USA exists

• Minimum lifetime of the cables is 1010

pulses =111 years

HV Pulse Cable cont.

Klystron Voltage 128kVPrimary Current 1.1kA

Primary Voltage 10.6kV

Remaining problem: EMI needs investigation

RF Power Waveguide Distribution• Distribution of klystron output power to the

superconducting cavities• Protection of the klystron from reflected power• Control of phase and Qext

DETAIL

circulator

hybrid

loads

Q tuner

to cavity

RF from klystron

Cryomodule 1 Cryomodule 2 Cryomodule 3 Cryomodule 4

RF Waveguide ComponentsCirculator (Ferrite)3 Stub Tuner (IHEP, Bejing, China) E and H Bends (Spinner)

Type WFHI 3-4Peak input power, MW 0.4Average power, kW 8Min isolation at 1.3 GHz, dB >30Max insertion loss at 1.3 GHz, dB ≤0.08Input SWR at 1.3 GHz (for full reflection)

1.1

Type WFHL 3-1 WFHL 3-5Peak input power, MW 2.0 5.0Average power, kW 10 100Min return loss at 1.3 GHz, dB 32÷40 32÷40Max VSWR at 1.3 GHz <1.05 <1.05Max surface temperature, ∆T °C (for full average power)

20 30

Physical length, mm 385 850

Changing phase, degree 60Impedance matching range 1/3Zw 3ZwMax power, MW 2

* Zw – waveguide impedance

Directivity, dB 30Return loss, dB 35Coupling factor, dB(due to tolerance overlapping only 13 differentcoupling factors instead 18 are nessesary)

12.5; 12.0; 11.4;10.7; 10.1; 9.6;

9.1; 8.5; 7.8;7.0; 6.0; 4.8; 3.0

Accuracy of coupling factor, dB 0.2

Type WFHLL 3-1Peak input power, MW 1.0Average power, kW 0.2Min return loss at 1.3GHz, dB 32 40Max VSWR at 1.3 GHz 1.05Max surface temperature, T C (for full average power)

50

Physical length, mm 230

Hybrid Coupler (RFT, Spinner) RF Load (Ferrite)

RF Load (Ferrite)

RF Waveguide Distribution Status

• Waveguide components for the XFEL havebeen developed in cooperation with industryor are standard of the shelves components

• Operation experience of 10 years from TTF

• Development of integrated components has been started (e.g. circulator with integratedload) to allow faster and more reliableinstallation

Summary• For all RF system components vendors are available;

still need additional vendor for modulator• The HV pulse cable prototype has been

manufactured and tested• The problem of EMI needs further investigation• Industrialization process for the RF system

components is ongoing• Final design of XFEL versions of the RF system

components must be completed; but difficult to hiremore personnel