Emma rf system alan wheelhouse astec daresbury laboratory
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EMMA RF System Alan Wheelhouse, ASTeC, Daresbury Laboratory. Content. EMMA RF System Overview Specification RF System Progress RF Cavity High Power RF System Waveguide Distribution System LLRF System Cabling & Connections Plan. RF System Overview. RF Cavities.

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EMMA RF System Alan Wheelhouse, ASTeC, Daresbury Laboratory

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EMMA RF System Alan Wheelhouse,ASTeC, Daresbury Laboratory

Commissioning Workshop Alan Wheelhouse


  • EMMA RF System Overview

    • Specification

  • RF System Progress

    • RF Cavity

    • High Power RF System

    • Waveguide Distribution System

    • LLRF System

    • Cabling & Connections

  • Plan

Commissioning Workshop Alan Wheelhouse

RF System Overview

RF Cavities

High Power RF Amplifier System

Waveguide Distribution System

Commissioning Workshop Alan Wheelhouse

RF Cavity

Commissioning Workshop Alan Wheelhouse

Cavity Design & Specification

* LLRF + Distribution

Commissioning Workshop Alan Wheelhouse

RF Cavity Progress

Input Coupler construction

(Times Microwave)

  • All 20 cavities delivered

    • Delays due feed-through delivery from Times Microwave

  • 14 cavities tested

    • Tests on-going

  • Tuners sticking

    • Sheered copper spring

    • Spring replaced with lighter force copper spring

    • Silver plated

  • Q0≈20000 achieved

  • Four cavities successfully conditioned

    • One conditioned to 10kW

    • Three conditioned to 5kW

Cavity construction

Tuning range 0- 25 mm

Commissioning Workshop Alan Wheelhouse

RF Cavity Evaluation

  • Procedure defined

  • 14 cavities tested

    • Rest being tested presently

  • Pick probe altered on a number of cavities

    • Optimisation for 40 dB transmission

  • QL≈10,000 achieved

Commissioning Workshop Alan Wheelhouse


Commissioning Workshop Alan Wheelhouse

CPI VIL409 HPRF System

  • 45kV switch mode power supply

  • Charging capacitor

  • CPI IOT VKL-9130B

    • Tested to 100kW

    • 5.5MHz bandwidth

  • Bruker solid state amplifier

    • Tested to 1.8kW (linear)

  • WR650 waveguide output

    • Via a circulator


Solid State Amplifier



Charging Capacitor


Commissioning Workshop Alan Wheelhouse

Factory Acceptance Tests

  • Factory acceptance tests completed Sept 09

  • Power requirements met across the frequency band

    • 90kW at waveguide

    • Up to 96kW from IOT

    • Efficiency > 50%

    • Gain typically > 20dB

  • HV pulse droop - 1.25kV

  • HV ripple 150V @ 44kV

    • 0.34% (Spec ±0.5%)

  • Grid voltage ripple 0.4V @ 95V

    • 0.42% (Spec ±1%)

  • X-ray levels 10µSv/h seen at the IOT (Spec 2.5µSv/h)

  • Issue with parameters reading values during off periods!



Commissioning Workshop Alan Wheelhouse

Trip Response Times

  • Trip response time and repeatability issue

  • Improvements made to the trip circuit

  • Repeatable trip response times of 80µs achieved

  • Wire crowbar test successfully performed at 40kV

    • 6” AWG32 wire with enamel

    • Stored energy < 18J (Spec 15J)

1 TTL pulse from PIN diode

2 Fault

3 RF pulse

4 Nesting pulse to SS amp

Commissioning Workshop Alan Wheelhouse

Site Acceptance Tests

  • Delivered 23rd September 2009

  • Installation and site acceptance completed 2nd October 2009

    • Power level and frequency responses checked

    • Issue with EPICS interface

    • Now resolved

    • Temporary water fittings used from ALICE

    • Operations manual being prepared

    • Draft operations manual supplied 23rd November 2009

Commissioning Workshop Alan Wheelhouse

Harmonic and Noise Tests

  • Input tuned for 1.29875GHz

  • X-ray levels at 90kW level

    • 11.2µSv/h seen at the IOT for 1.2960GHz

    • 9.5Sv/h seen at the IOT for 1.3000GHz

    • 13µSv/h seen at the IOT for 1.3015GHz

  • 0.3µSv/h at the cubicle panel

  • Warning labels to be added to panels

Commissioning Workshop Alan Wheelhouse

EPICS Interface

  • EPICS interface working

  • Labview program modified so that values read zero when off

  • EPICS controls layout being designed

EPICS Dummy Screen

Commissioning Workshop Alan Wheelhouse


Commissioning Workshop Alan Wheelhouse

Waveguide Distribution System

Commissioning Workshop Alan Wheelhouse

Test Set-Up


Mega hybrid splitter

Output cable

Bridge section

Balance load


Transition / Phase shifter


Commissioning Workshop Alan Wheelhouse

Test Set-Up (2)

Cable support bracket

End launch transition

to 7/8 IEC

Phase shifter with McLennan motor

Balance load

Load tuners (isolation trimmers)

E plane tuners

Angled flange

Floor support bracket

Directional coupler

Adjustable shorting bars

Commissioning Workshop Alan Wheelhouse

Flange & Gasket Assembly

Angled flange


Commissioning Workshop Alan Wheelhouse

Phase Shifter Characteristics

  • Phase shifter resolution

    • 0.1° = 0.01mm

  • Full range = 196°

    • Spec : 180°

  • As the phase shifter goes further in it approaches the waveguide cut-off

Commissioning Workshop Alan Wheelhouse

Input Return Loss

All output cables were terminated in precision 50Ω loads

Input return loss <30dB



Commissioning Workshop Alan Wheelhouse

Output Responses

Single input tests

The 3 dB amplitude difference due to the hybrid splitter

All cables and their phase shifters set to produce a co-phase output at the lowest operating frequency

  • The reference port is 1/2 LHT

    • Midway phase value after cable trimming

  • Phase setting, over full bandwidth > 180°



Commissioning Workshop Alan Wheelhouse

Differential Output Phase

Phase shifters set to 0° and 180°

Measurements performed with respect to the reference port

Demonstrates that full phase shift control can be achieved

0° setting

180° setting

Commissioning Workshop Alan Wheelhouse


  • Sample of isolation between output ports

  • Isolation between ports:

    • > 42 dB (Typically 50 dB)

    • Optimised using balance load tuners

  • Worst case path is via the 1/2 hybrid

    • Strongest coupling to the backward wave or isolation path within the ring

  • Isolation between half rings is a sum of the hybrid coupling and isolation of the input hybrid splitter

Left hand ring

Right hand ring

Commissioning Workshop Alan Wheelhouse

Further Tests

  • Directional coupler coupling

    • Forward: -40.5 to -39.8 dB (± 0.35 dB)

    • Reverse: -40.5 to -39.75 dB (± 0.375 dB)

    • Spec : 40 ± 0.5 dB

  • Directional coupler directivity

    • Forward: > 41 dB

    • Reverse: > 42 dB

    • Spec : >40 dB

  • Some degree of variation of coupling and directivity seen versus phase shift

    • Due to parasitic interaction with the phase shifter short circuit.

  • Cable attenuation : 0.048 dB/m at 1.3 GHz

Commissioning Workshop Alan Wheelhouse

Llrf control SYSTEM

Commissioning Workshop Alan Wheelhouse


  • Provides the stabilisation of the accelerating field

  • Results from tests at 5kW (~140kV) per cavity

    • Phase 0.0093° (Spec 0.3°)

    • Amplitude 0.006% (Spec 0.3%)

  • Libra system developed by I-Tech

  • Procedures being defined for the timing, cresting and phase setting

  • Presently under-going additional programming

    • For the stepper motors and the controllers

    • For adapting the system to lower sampling frequency (81.25MHz) to aid the timing issue

Commissioning Workshop Alan Wheelhouse

Cabling & Connections

Commissioning Workshop Alan Wheelhouse

Cabling & Connections

  • LLRF rack designed

    • Build on going

    • Cabling being pulled in

  • Cavity

    • 2 thermal cut-out interlock switches fitted to the water circuits

    • In series with the water flow trip on the return

  • Tuner and phase shifter control

    • Drawings for PCUs and Lantronics systems being drawn up

Commissioning Workshop Alan Wheelhouse


Commissioning Workshop Alan Wheelhouse


  • HVPS Commissioning1 day

  • Waveguide Distribution

    • Installation3 days

    • Commissioning3 days

  • LLRF

    • Cable calibration3 days

    • Low power tests1 week

    • High power tests1 week


    • Screen layout1 week

    • CommissioningIn parallel with above work

  • Timescales dependent on electrical work

Commissioning Workshop Alan Wheelhouse

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