Engineering of the power prototype of the ESRF HOM damped cavity*

V. Serrière, J. Jacob, A. Triantafyllou, A.K. Bandyopadhyay, L. Goirand, B. Ogier

*This work, carried out within the framework of the ESRFUP project, has received research funding from the EU Seventh Framework Programme, FP7.

13th ESLS RF Meeting, Desy, Hamburg, 30th September - 1st October 2009

• IntroductionThe new ESRF cavity Objectives

• Aluminum prototypeDesign optimizationExperimental validation

• Copper power prototypeDesign aspectsTechnology of fabrication

• Perspectives and future work

Summary

13th ESLS RF Meeting, Desy, Hamburg, 30th September - 1st October 2009 1Anna Triantafyllou-E.S.R.F.

Introduction

The development of the new 352 MHz cavity for the ESRF is based on the 500 MHz European HOM damped normal conducting cavity.

2

Cavity body HOM damper

Tuner

Cou

pler

Vacuum pump

Anna Triantafyllou-E.S.R.F. 13th ESLS RF Meeting, Desy, Hamburg, 30th September - 1st October 2009

Introduction

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300 mA of beam current :

- Design margin in terms of power per coupler window : 500 mA of stored beam.

- Design margin in terms of HOM damping : 1A of bunch instability threshold to anticipate possible discrepancies between numerical and experimental data.

9 MV of accelerating voltage :

New ESRF cavities objectives :

- Installation of 18 new single-cell cavities.

- The system should be operational with 12 cavities.

Anna Triantafyllou-E.S.R.F. 13th ESLS RF Meeting, Desy, Hamburg, 30th September - 1st October 2009

Aluminum prototype

Design optimization :

1 damperfor the remaining HOMs : fc = 1.05 GHz d = 160 mm

The vacuum pump port is not degrading the quality factor

Length before C48 ferrites = 840 mmDissipated power @ 352 MHz < 100 Watt

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2 dampers not in the same plane : to avoid the high impedance 758 MHz mode measured on the previous prototype

2 dampersfor the lowest HOMs : fc = 452 MHz d = 230 mm

Anna Triantafyllou-E.S.R.F. 13th ESLS RF Meeting, Desy, Hamburg, 30th September - 1st October 2009

Aluminum prototype

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- Good correlation between measured and calculated data.

- All the measured impedances of the HOMs are lower than the L.C.B.I.

4000

3000

2000

1000

0

imp

ed

an

ce (

Oh

ms)

3.0x109

2.52.01.51.00.5

frequency (Hz)

Measurements GdifidL calculations Threshold (1A)

Validation of the numerical model :

@ 352 MHz :Rs/Q =145QCu : 30 k

Rs=4.35 MΩ

Ridge width = 60 mm

Anna Triantafyllou-E.S.R.F. 13th ESLS RF Meeting, Desy, Hamburg, 30th September - 1st October 2009

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Design aspects

- The gap problems between the ridges and the cavity body are eliminated by splitting the HOM dampers in three parts.

Copper prototype

Coupling section

Intermediate section

Absorber

Coupling section e-beam welded to the cavity body.

In the ridge zones, the electrical continuity

will be established by means of RF fingers.

Anna Triantafyllou-E.S.R.F. 13th ESLS RF Meeting, Desy, Hamburg, 30th September - 1st October 2009

Copper prototype

Anna Triantafyllou-E.S.R.F.

Design aspects- In house design of the cooling system.

*Thanks to Lin Zhang for his advice in thermal computations

Maximum temperature : 56°C

Cooling channels

Heat flux computed for the degraded operation 9MV with 12 cavities :

713th ESLS RF Meeting, Desy, Hamburg, 30th September - 1st October 2009

1. Machining of the pieces

Copper prototype

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Establishment of technological process (1/3)

2.The gap is avoided by splitting the dampers inthree parts. The first part is e- beam welded to the body.

e-Cavity body

Couplingsection

Beam stop: will be removed after welding by turning

e-

constant 15 mm thickness

all around thee-beam welding

Anna Triantafyllou-E.S.R.F. 13th ESLS RF Meeting, Desy, Hamburg, 30th September - 1st October 2009

3.The vacuum flanges, outlets and pipes are brazed in a single step

Turning this assembly

Brazing of the S.S. and the Cu

TIG welding of the flanges

Copper prototype

Copper plating the SS surface

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Establishment of technological process (2/3)

Anna Triantafyllou-E.S.R.F. 13th ESLS RF Meeting, Desy, Hamburg, 30th September - 1st October 2009

Machining of the end discsBrazing step to attach the cooling system and the outlets.

Intermediate coupling sectionsBrazing of the vacuum flanges and the cooling system.

Brazing of C48 ferrites on CopperBrazing on the ridges

TIG welding of the Cover.

Establishment of technological process (3/3)

Copper prototype

Frequency tuningby machining the end disc

The end discs are added in a last brazing step.

10Anna Triantafyllou-E.S.R.F. 13th ESLS RF Meeting, Desy, Hamburg, 30th September - 1st October 2009

Copper prototype

Alternative Fabrication process

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Division of the cavity body in 3 parts

Machining of the cooling system in

each part.

e beam welding to add the water box covers

in each part.

Coupling sections and outlets are joined by e beamfrom the internal face.

e-

Outlets brazing before the cavity assembly

e beam welding for the 3 shells assembly

- e beam welding to join the angles.- e beam welding for the end discsafter the frequency tuning steps.

Anna Triantafyllou-E.S.R.F. 13th ESLS RF Meeting, Desy, Hamburg, 30th September - 1st October 2009

Anna Triantafyllou-E.S.R.F. 13th ESLS RF Meeting, Desy, Hamburg, 30th September - 1st October 2009

Copper prototype

Stress calculation :

Stress < 27 MPa40 MPa < Stress < 57 MPa

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- max water pressure = 15 Bars

The Maximum stress computed in the e beam weld area

is reduced by increasing the e beam welding surface.

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Conclusions and Perspectives

Validation of the simulation model by an aluminum prototype.

Two different fabrication processes for the power prototype.

Ferrite infra red test bench under development.

Delivery of three prototypes expected by the end of 2010 followed by tests.

Anna Triantafyllou-E.S.R.F. 13th ESLS RF Meeting, Desy, Hamburg, 30th September - 1st October 2009