DESY Experiences in Hydroforming of Elliptical RF Cavities · W. Singer. DESY Experiences in Hydroforming. Hydroforming Workshop, September 1, 2010, FNAL, USA Hydroforming of cells

W. Singer. DESY Experiences in Hydroforming. Hydroforming Workshop, September 1, 2010, FNAL, USA

DESY Experiences in Hydroformingof Elliptical RF Cavities

W. Singer

• Introduction• Hydroforming technique (necking, expansion)• Nb tubes for hydroforming• Examples of RF performance


Introduction

Advantages of seamless cavity fabrication

• no RRR degradation in the welding seam, in the heat affected zone HAZ and in the weld overlapping

• no risk of equator weld contamination due to not sufficiently clean preparation for welding

• no problem with pits in the HAZ, that are intensively in discussion last time

• lower cost of fabrication can be expected, especially for large series.

• less scattering in performance statistic of seamless cavity compare to welded cavities is to expect .


Hydroforming consists of two steps:a) reduction of diameters at ends of tubes and iris areas (necking)b) tube expansion at the equator

Hydroforming technique


Several necking methods were check out before the current necking procedure was established

• spinning

• necking by profile ring

• hydraulic necking

• electromagnetic strike necking,

• verjungen (diameter reduction by push the tube end through the set of rings of smaller diameter)

• rotary swaging (rundkneten)

Step 1: necking

Principle of rotary swaging


Not uniform necking at the iris area of tube end done at company HTI by spinning ( hole appeared during centrifugal barrel polishing).

Step 1: necking• necking by spinning

KEK necking machine (successful on Cu-tubes)

In principle it works


Principle of diameter reduction in the tube end and iris area

Step 1: necking (by profile ring)Improvement of the necking procedure and development of DESY

necking equipment provided the success (combination of radial and axial movement )

Principle of DESY necking equipment


Reduction mechanism.

Seamless technique by hydroforming: step 1- necking

DESY Necking machine: new PC controlled necking procedure

Tubes after reduction in the iris areas

DESY developed necking equipment (by profile ring)

Step 1: necking (by profile ring)


Conclusion to necking:• spinning: works (essential wall thickness reduction close to iris, probably this can be improved by parameter optimization)

• necking by profile ring: works (best results)

• hydraulic necking: does not work (not round shape)

• electromagnetic strike necking: works for Cu, can work on Nbonly for bimetallic NbCu tubes (resistance of Nb is to high ), the shape is not sufficiently under control due to single strike

• verjungen: works only for single cells (time consuming due to many rings, not optimal shape of the necking)

• rotary swaging (rundkneten): works (damaging of the surface, significant work hardening)


Dependence of the elongation on temperature. It make sense to perform hydroforming of niobium at room temperatures

Step 2: Expansion (Hydroforming)

First question. Hydroforming conditions ,parameters?

Is the room temperature appropriate for hydroforming? Yes

DESY data


Dependence of maximum elongation of niobium versus strain rate (H, M, S different literature data).

Correct strain rate should be chosen for hydroforming

Chosen strain rate is between 0.01 sec-1 and 0.001 sec-1

1sec, −•

∂∂

=tεεStrain rate

Compilations of C. Antoine

How fast to perform the deformation (hydroforming)?


0

50

100

150

200

250

0,00 0,20 0,40 0,60 0,80

Epsilon

Sigm

a, N

/mm

2Heraeus Tube7. Paralel to axis, contin.

Heraeus Tube7. Circum ferential, contin.Heraeus Tube7. Paralel to axis, stepw ise

Heraeus Tube7. Circum ferential, stepw ise

Comparison of the tensile test in continues and pulse regimeThe strain before necking can be increased by using a periodic stress fluctuation (pulse regime). Probably the pull-release regime of the deformation artificially increases the work-hardening of Nb in low-yield strength regions and therefore shift the break to higher elongations.

Pulsing of the pressure during hydroforminghelps


DESY hydroforming machine

DESY hydroformingmachine

• Designed and build in Russia (INR, Troitsk)

• Equipped with hydraulic systems and software at DESY

• From dimension is in position to produce only units of 3 cells

Fixed MatrixMovable MatrixTube

Pcyl sensor Lsensor

Oil Hydr system

Water Hydr. system

Rsensor

Ptube sensor

Principle of hydroforming


1 0 0 .0 0

0 .0 0

2 0 .0 0

4 0 .0 0

6 0 .0 0

8 0 .0 0

2 5 3 61 2 0 0 4 0 0 6 0 0 8 0 0 1 0 0 0 1 2 0 0 1 4 0 0 1 6 0 0 1 8 0 0 2 0 0 0 2 2 0 0 2 4 0 0

0 .e n d 1 0 0 0 .5 0 2 8 .5 7

b e g 3 9 9 .3 7 1 8 .2 7

gr1

6 5 .0

4 1 .7

4 5 .0

4 7 .5

5 0 .0

5 2 .5

5 5 .0

5 7 .5

6 0 .0

6 2 .5

2 5 .8-0 .1 2 .0 4 .0 6 .0 8 .0 1 0 .0 1 2 .0 1 4 .0 1 6 .0 1 8 .0 2 0 .0 2 2 .0 2 4 .0

m e a s

c a lc u

C u r 1 1 .6 9 5 0 .5 4

gr2

Init. LoadSaveZero

Stop ResetCut

Load Dcalc. ShowdataSave Dcalc.

0.5P in tube

8Feb2000Date

2:20 Time

D :\ 1 c e ll h yd ro fo rm in g \ D a ta \ N io b iu m D 8 3 m m P r1 .s toPath

Niobium 137*83.0*2.6mm. L0=51.6.Drossel=300, kran on -8, kran off 135.Niobium tube Pr1. During of hydroforming (18-6mm of length) the shape was conical, dD=5mm). Smooth surface, inside and outside. Calibrated at 560bar. Thickness at equator =2.2mm.

C o m m e n ta ry

P in cylindery1

Lengthx2 Radiusy2

25.76Length, mm

0 .8 4 .3 2 5 .8 4 1 .7 3 .1

2 .8 4 .6 2 5 .8 4 1 .7 3 .1

0

0

Data

PROCESS START

5 2 2 6 6 8t0

1 4 .9P ze ro

7 2 .1 6L ze ro

2 4 .7 0

6 5 .0 0 2 4 .1 7

7 0 .5 0 2 3 .6 5

7 5 .5 0 2 3 .1 2

8 3 .5 0 2 2 .0 7

9 0 .0 0 2 1 .0 2

9 7 .5 0 1 8 .9 2

0 1 .5 0 1 6 .8 2

0 4 .0 0 1 4 .7 1

0 6 .5 0 1 2 .6 1

0 7 .0 0 1 0 .5 1

0 6 .0 0 8 .4 1

0 5 .0 0 6 .3 1

0 3 .0 0 4 .2 0

0 1 .0 0 2 .1 0

9 9 .0 0 0 .0 0

0 .0 0 0 .0 0

0 .0 0 0 .0 0

0 .0 0 2 5 .7 5

4 2 .0 0 2 5 .2 2

5 6 .5 0

0

0

D c a lc

41.70Radius, mm

1 0 7 .8

0 .0

2 0 .0

4 0 .0

6 0 .0

8 0 .0

1 0 0 .0

2 5 .8-0 .1 2 .0 4 .0 6 .0 8 .0 1 0 .0 1 2 .0 1 4 .0 1 6 .0 1 8 .0 2 0 .0 2 2 .0 2 4 .0

m e a s

c a lc uC u r 1 8 .9 2 9 7 .5 0

gr3

P in tubey3Lengthx3

41.70R 1 41.70R 2

0.00d R

93.6Pstab

0.10dL

25.66L teor

4.4Pcylinder

-1 9 .6P c y lze ro

0.80Pscale170P tu b e m a x

130P c y l m a x

4 1 .7 5R te o r

0 .9 4K Pstart

0 .9 9K P s ta b

5 0 0 0T p a u se , m se c

0 .0d P c o r.%

T im e P tu b e L , m m R ,m m P c y l

FEM Simulation of the

hydroforming

Pressure-axial displacement

Radius-axial displacement

PC control allows reproducibly repeat the forming parameters

Front panel of the software for hydroforming - machine


Hydroforming of cells can be done or as three cells simultaneously or cell by cell (hydroforming of the 9-cells

from one tube piece can be done on the same way)

All steps of hydroforming optimized and checked on the Cu dummies


Synchronization mechanism for multi cell fabrication by

hydroforming

Some ideas contributed to hydroforming success

Nonsymmetrical mould for hydroforming

Fixed MatrixMovable MatrixTube

Pcyl sensor Lsensor

Oil Hydr system

Water Hydr. system

Rsensor

Ptube sensor

Developed ideas summarized in the patent.

W.Singer, I.Jelezov; No. 10 2007 037 835 ; 18 September 2008


Fabrication steps of 9 cell cavity by hydroforming as option 3x3


Z145: 9-cell as 3x3 cell cavity hydroformed at DESY, completed at E.ZANON (reached ca. 30 MV/m).

Two new 9-cell cavities are currently in completing at E.ZANON


Conclusion to hydroformimng

• Hydroformig of 9-cell cavity from one tube-piece is feasible

• Dimensions of a new machine have to be foreseen for that.

• DESY machine is a laboratory equipment. For industrial equipment more moulds (intermediate constraints), less sensors for parameter measurements has to be foreseen

• Experiences of INR (Russia) designers would be reasonable to use

• Computer simulations are helpful on the starting stage

• PC controlled hydraulic allows to optimize and reproduce the forming parameters


Bulk Nb tube fabrication.Several techniques of the tube fabrication have been taken

into consideration at DESY

• Tube production by back extrusion from the ingot part:

• Tube production by spinning

• Tube production by deep drawing

• Tube processing by flow forming

• Welded Nb tubes.

• Seamless Nb tubes produced on powder metallurgical way


Principle of seamless tube fabrication by back

extrusion

• Seamless tubes: back extrusion (W.C. Heraeus)

Different tubes with covers from Nb1% Zr produced by back

extrusion at the company W.C. HERAEUS (Germany)

(Plunger)


0

50

100

150

200

250

0,00 0,20 0,40 0,60

Epsilon

Sig

ma,

N/m

m2

Heraeus Tube7. Paralel to axis, contin.

Heraeus Tube7. Circum ferential, contin.

Strain - stress curve of of back extruded Nb tube (drawback:

anisotropic properties)

Microstructure of back extruded Nb tube

produced from a pill taken from ingot

Only small cavities (ca. 3,9 GHz) have been successfully hydroformed from back extruded tubes


Fabrication of the seamless pot from Nb plate by spinning is possible without intermediate annealing

• Spinning

Cavities hydroformed from spun tubes (reached up to 42 MV/m)


• Deep drawingPrinciple of deep drawing; a-first step, b-second and further steps

Successful tube fabrication by collaboration of Fa. Bravo and INFN Legnaro

Single cell cavity fabricated at Fa. Butting (Germany) in collaboration with DESY from deep drawn tube produced at the company B.J. Enterprise (USA) (reached 39 MV/m

In some cases bad inside surface of tubes (cracks, removed by machining)


• Flow forming

Flow forming of niobium spun tubes at MSR (Germany). Precise wall thickness after flow forming.

Tolerances within of +/- 0,1 mm


Stress-strain curves and microstructure of Nb tubes produced by combination of spinning and flow forming. Tensile tests done in circumferential direction

Microstructure and texture of Nb tubes produced by combination of spinning and flow forming

Best result was achieved by combination of spinning (or deep drawing) with flow forming: appropriate microstructure and mechanical properties

Nb tubes,ID=150 mm

0

20

40

60

80

100

120

140

160

180

0 5 10 15 20 25 30 35 40 45

dL/L0*100

F/S0

, N/m

m2

Nb-1B1-1 780C 1h Nb-1B1-2 780C 1h Nb-1B3-1 800C 1h Nb-1B3-2 800C 1h Nb-1T1-1 780C 1h Nb-1T1-2 780C 1h Nb-1T3-1 800C 1h Nb-1T3-2 800C 1h

Such tubes used for fabrication of multi cell cavities

R.CrooksR.Crooks


Top cell (tube top)

(Tube bottom) Bottom cell

T-map on 3-cell hydroformed cavities from spun+ flow formed tubes at Eacc = 27 MV/m, (JLab) indicating several hot-spots in the equator area,

mostly on the top cell (relation to the tube fabrication method).

Poster THP043 LINAC08

Tube after spinning

Cavity inside surface

Cavity inside surface

Ca. 30 MV/m after BCP only


Tubes: Roy Crooks: Black Laboratories, L.L.C., Newport

News, VAHigh purity Nb tube production

developed and coordinated with ATI Wah Chang

Heavily deformed billet, processed for fine grain structure

Shaped by forward extrusion and flow-forming (more in presentation of

Roy Crooks) Black Lab. Tubes.

Cracks in few cells at the iris1,3 GHz cells hydroformed at DESY from Black Lab tubes


Conclusion to tube fabrication

• Back extrusion from the ingot part: does not work (do not provide the required mechanical properties)• Spinning: works for short tubes (small cracks on the top part of the tube)• Deep drawing: works (DESY experiences, in some cases cracks on the inside surface. Good experiences of E. Palmieri)• Flow forming: works well in combination with spinning, deep drawing, extrusion. Best DESY tubes• Welded Nb tubes. Does not work (ruptures at the HAZ)• Powder metallurgical tubes: does not work (not sufficient purity, porosity)• Fabrication of long tubes for 9-cell cavities is proven by Black Lab (Roy Crooks presentation)


Some best seamless single cell cavities. Preparation and RF tests: K.Saito, P.Kneisel

Hydroform ed single cell Nb cavity 1K2

1,00E+09

1,00E+10

1,00E+11

0 10 20 30 40

Eacc, MV/m

Qo

1K2, Nb100 Heraeus, HT1400°C, BCP, EP

Hydroform ed single cell Nb cavity 1BT1

1,00E+08

1,00E+09

1,00E+10

1,00E+11

0 10 20 30 40

Eacc, MV/m

Qo

1BT1, Nb200 Cabot, BCP, EP, HT 140°C

Examples of RF performance: single cells


Surface treatment at DESY: 40 μm BCP, 800 °C heat treatment, tuning; 170 μm electropolishing (EP), ethanol rinsing, 800 °C heat treatment; 48 μm EP, HPR, assembly and evacuation1E+09

1E+10

1E+11

0 5 10 15 20 25 30 35Eacc (MV/m)

Q0

T = 2 K

Examples of RF performance: 9-cell cavity


Conclusions

• High accelerating gradient up to 40 MV/m can be achieved in hydroformed cavities

• Fabrication of the 9-cell cavities (3x3 units) of TESLA like shape is proven.

• The main remaining task is industrialization of the fabrication technique.


ACKNOWLEDGMENTSMany thanks to my colleagues at DESY who works with me

these years and significantly contributed to the development of hydroforming technology:

I. Jelezov, X. Singer, H. Kaiser, G. Weichert, G. Meyer, T. Khabiboulline, I. Gonin, V. Puntus, A.Stepanov; A. Scassirskaja,

A. Sulimov.Many thanks to A. Matheisen, B. van der Horst, G. Kreps, H.

Wen and A. Ermakov for support in our work.

Significant contribution to the success of hydroformingdevelopment was done by P. Kneisel (JLab) and K. Saito (KEK)

due to state of the art preparation and RF tests of the hydroformed cavities.

The work was done in collaboration with INR (Russia). The work was supported in part by European CARE program.

Documents

DESY Experiences in Hydroforming of Elliptical RF Cavities · W. Singer. DESY Experiences in Hydroforming. Hydroforming Workshop, September 1, 2010, FNAL, USA Hydroforming of cells