SC RF Studies in Europe - · – Final cleaning and drying (UV for bacteria and on line ... from G. Geschonke’s Poster for the ITRP visit to DESY. HIF05 Carlo Pagani 9 31 May 2005

SC RF Studies in Europe

Carlo PaganiINFN Milano and DESY

On leave from University of Milano

HIF0531 May 2005Carlo Pagani 2

SRF before TESLA

“Livingston Plot” from Hasan Padamnee


Limiting Problems

Poor material propertiesModerate Nb purity (Niobium from the Tantalum production)Low Residual Resistance Ratio, RRR Low thermal conductivityNormal Conducting inclusions Quench at moderate field

Poor cavity treatments and cleannessCavity preparation procedure at the R&D stagePoor rinsing and clean room assembly not yet introduced

Microphonics Mechanical vibrations in low beta structures High RF power required

MultipactoringMajor limit for HEPL and electron linacs to 1984 Poor codes and surface status

Quenches/Thermal breakdownLow RRR and NC inclusions

Field EmissionGeneral limit at those time because of poor cleaning and material defects


R&D waiting for big projects

MultipactoringA few computer codes developedSpherical shape realized at Genova and qualified at Cornell & Wuppertal

Field EmissionEmitters were localized and analyzedImproved treatments and cleanness

Quenches/Thermal BreakdownHigher RRR NbDeeper control for inclusions

1984/85: First great successA pair of 1.5 GHz cavities developed andtested (in CESR) at Cornell

Chosen for CEBAF at TJNAF for a nominal Eacc = 5 MV/m

Eacc

> 5 MV/m


Large project impact on SRF technology

In 1985 the successful test of a pair of SC cavities in CERS opened the door to the large scale application of SRF for electrons

The decision of applying this unusual technology in the largest HEP accelerators forced the labs to invest in Research & Development, infrastructures and quality control

The experience of industry in high quality productionshas been taken as a guideline by the committed labs

At that time TJNAF and CERN played the major rolein SRF development, mainly because of the project size

The need of building hundreds of cavities pushed the labs to transfer to Industry a large part of the production

The large installations driven by HEP produced a jump in the field

R&D and basic research on SRF had also a jump thanks to the work of many groups distributed worldwide

LEP

CEBAF


CEBAF and LEP II

LEP II & CERN

32 bulk niobium cavitiesLimited to 5 MV/mPoor material and inclusions

256 sputtered cavitiesMagnetron-sputtering of Nb on CuCompletely done by industryField improved with time<Eacc> = 7.8 MV/m (Cryo-limited)

352 MHz, Lact=1.7 m

1.5 GHz, Lact=0.5 m5-cell cavities

4-cell cavities

CEBAF

338 bulk niobium cavitiesProduced by EU industryProcessed at TJNAF in a dedicated infrastructure


Important technological steps

Use of the best niobium (and copper) allowable in the market at the time Industrial fabrication of cavity components with high level quality controlAssembly of cavity components by Industry via Electron Beam welding in clean vacuum Use of ultra pure water for all intermediate cleaning Use of close loop chemistry with all parameters specified and controlledCavity completion in Class 100 Clean Room

– Final cleaning and drying (UV for bacteria and on line resistivity control)

– Integration of cavity ancillaries

That is

New level on Quality Control


A great success for LEP II

0

5

10

15

20

25

30

4 4.2 4.4 4.6 4.8 5 5.2 5.4 5.6 5.8 6 6.2 6.4 6.6 6.8 7 7.2 7.4 7.6 7.8 8 8.2 8.4 8.6 8.8 9 9.2 9.4

Accelerating field [MV/m]

Num

ber o

f cav

ities

96 GeV100 GeV104 GeV

96 GeV:Mean Nb/Cu6.1 MV/m

100 GeV: 3500MVMean Nb/Cu6.9 MV/m 104 GeV: 3666MV

Mean Nb/Cu7.5 MV/m

design

Accelerating Field Evolution with time Final energy reach limited by

allowable cryogenic powerfrom G. Geschonke’s Poster for the ITRP visit to DESY


Same lessons learned

Bulk Niobium is preferred to push for gradient and quality factor

Magnetron sputtering looks better in some cases (LHC) when beam current is more important than accelerating field

Cryogenics systems are highly reliable and produced by industry

SRF ancillaries can be designed to be as reliable as the one required by the Normal Conducting RF technology

– 2 K operation and SRF quality controls end to be a plus

For high gradient, Eacc, and high quality factor, Q, Niobium quality has to be pushed to the possible limit

Quality control during cavity production and surface processing has to be further improved. High Pressure Rinsing can make the difference

Basic R&D and technological solutions must move together

When fabrication procedures are fully understood and documented,Industry can do as well and possibly better


The TESLA Mission

TTF: TESLA Test Facility• Full Prototype of the TESLA Linac: components and operation• Infrastructure: for cavity development and module assembly

Basic goals• Increase gradient by a factor of 5 (Physical limit for Nb at ~ 50 MV/m)• Reduce cost per MV by a factor 20 (New cryomodule concept and industrialization)• Make possible pulsed operation (Combine SRF and mechanical engineering)

as in 1995

Björn Wiik

Develop SRF for the future TeV Linear Collider


RSF for Higher Luminosity

yx

e

c.m.

b

σσN

EPL ×∝

nb = # of bunches per pulsefrep = pulse repetition ratePb = beam powerEc.m.= center of mass energy

L = LuminosityNe = # of electron per bunchσx,y = beam sizes at IPIP = interaction point

yx

2e

σσNL ∝ xσ

yσrepb fnL ×∝

Parameters to play withReduce beam emittance (εx

.εy ) for smaller beam size (σx.σy )

Increase bunch population (Ne )Increase beam powerIncrease beam to-plug power efficiency for cost

( )repbb fnNP ××∝ e

Potential advantages of SRF Technology• Higher conversion efficiency: more beam power for less plug power consumption• Lower RF frequency: relaxed tolerances and smaller emittance dilution


laser driven electron gun

photon beam diagnostics

undulatorbunch

compressor

superconducting accelerator modules

pre-accelerator

e- beam diagnostics

e- beam diagnostics

240 MeV 120 MeV 16 MeV 4 MeV

The TTF I Linac – 6 Year exp.


TTF II – VUV FEL

RF gun

400 MeV 120 MeV800 MeV

ACC 1ACC 2ACC 3ACC 4ACC 5

4 MeV

TESLA like tunnel for ACC 6 & ACC 7

Second BunchCompressor

ACC 4 & ACC 5 ACC 2 & ACC 3

VUV FEL User Facility• Linac Commissioning done

• SASE FEL Commissioning• High Gain done• Saturation coming soon


First 7 year balance (1992-98)(TESLA Cold Technology)

Funding

Major European Contributions(including personel)

DESY (+Germany) ~ 50%

France (CEA + IN2P3) 10-15%

Italy (INFN) 10-15%

and FNAL for US 10-15%

Design

Major European Contributions(in alphabetic order)

CEA/IN2P3

CERN

DESY

INFN


The TESLA Cavity

Hz/(MV/m)2≈ -1KLorentz

kHz/mm315∆f/∆l

mT/(MV/m)4.26Bpeak/Eacc

2.0Epeak/Eacc

Ω1036R/Q

TESLA cavity parameters

- Niobium sheets (RRR=300) are scanned by eddy-currents to detect avoid foreignmaterial inclusions like tantalum and iron- Industrial production of full nine-cell cavities:

- Deep-drawing of subunits (half-cells, etc. ) from niobium sheets- Chemical preparation for welding, cleanroom preparation- Electron-beam welding according to detailed specification

- 800 °C high temperature heat treatment to stress anneal the Nband to remove hydrogen from the Nb- 1400 °C high temperature heat treatment with titanium getter layerto increase the thermal conductivity (RRR=500)- Cleanroom handling:

- Chemical etching to remove damage layer and titanium getter layer- High pressure water rinsing as final treatment to avoid particlecontamination

Figure: Eddy-current scanning system for niobium sheets Figure: Cleanroom handling of niobium cavities

9-cell, 1.3 GHz

Major contributions from: CERN, Cornell, DESY, CEA-Saclay & INFN


A dedicated new infrastructure at DESY

Scanning niobium material for inclusionClean closed loop chemistry (Buffer Chemical Polishing – BCP)High Pressure Rinsing, HPR, and clean room dryingClean Room handling and assembling (Class 10 and 100)


Learning curve with BCP

3 cavity productions from 4 European industries: Accel, Cerca, Dornier, ZanonBCP = Buffered Chemical Polishing

Cornell1995

5-cellModule performance in the TTF LINAC

Improved weldingNiobium quality control

<Eacc> @ Q0 ≥ 1010 <Eacc> @ Q0 ≥ 1010

at Q = few 109

<1997>

<1999>

<2001>


Electro-Polishing & Baking for 35 MV/mThe AC 70 example

Electro-Polishing (EP)instead of

Buffered Chemical Polishing (BCP)• less local field enhancement• High Pressure Rinsing more effective • Field Emission onset at higher field

In Situ Baking

@ 120-140 ° C for 24-48 hours

• to re-distribute oxygen at the surface

• cures Q drop at high field

EP at the DESY plant• Low Field Emission 800°C annealing

120°C, 24 h, Baking• high field Q drop curedHigh Pressure Water Rinsing

Vertical and System Test in 1/8th Cryomodule


Radiation Dose from the fully equipped cavities while High Power Tested in “Chechia”“Chechia” is the horizontal cryostat equivalent to 1/8 of a TTF Module

Field Emission pushed to very high fieldBCP Cavities used in Modules 4 & 5 are in red, EP cavities in blue

BCP Cavities @ Eacc = 25 MV/m

EP Cavities @ Eacc = 35 MV/m

BCP = Buffered Chemical Polishing

EP = Electro-Polishing

Radiation dose producing50 nA of captured DarkCurrent: that is the TESLA safe limit giving200 mW of induced cryo-losses at 2 K


Performing Cryomodules

Required plug power for static losses < 5 kW/(12 m module)

Reliable Alignment Strategy

Sliding Fixtures @ 2 K

“Finger Welded” Shields

Three cryomodule generations to:improve simplicity and performances minimize costs


ACC4 & ACC5 Met Specs

Still some work at the module interconnectionCavity axis to be properly defined


Cold time[months]

Installation date

Type

13

161616

278

35

44

12

5

50

Feb 04M2*

Apr 03M3*M4M5

Jun 02M1*MSS

Jun 99M3

Sep 98M2

Jan 98M1 rep.

Mar 97M1

Oct 96CryoCap

Extensive Operation Experience

1

22

2

22

332

2


LCH and TESLA/ILC Module Comparison

From an LHC Status Report by Lyndon R. Evans

ACC 4 & ACC 5 in TTF ACC 2 & ACC 3 in TTF

∅ = 38”

∅ = 38” ∅ = 42”


TESLA Cryomodule Concept Peculiarities

PositiveVery low static lossesVery good filling factor: Best real estate gradientLow cost per meter in term both of fabrication and assembly

Project DependentLong cavity strings, few warm to cold transitionsLarge gas return pipe inside the cryomodule Cavities and Quads position settable at ± 300 µm (rms)Reliability and redundancy for longer MTTR (mean time to repair)Lateral access and cold window natural for the coupler

Negative ?Longer MTTR in case of non scheduled repairModerate (± 1 mm) coupler flexibility required


DA

C

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 kHz

250 kHz

AD

C

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

ImReImRe ImRe

clock

LOA

DC

LO

AD

C

LO

AD

C

ImRe

power transmission line

1.3GHzfield probe

3

cavity 36cavity 1 cavity 12

36

cavity 24

24121

Principle of RF Control

200 400 600 800 1000 1200 1400 1600 18000

5

10

15

400 600 800 1000 120011

11.5

12

12.5

zoomed region

acce

lera

ting

vol

tage

[M

V]

only feedback

(gain = 70)

with feedback and feedforward

control

beam

0 500 1300900 1700

300 700 1100

75

50

25

0

62.5

60.0

55.5

57.5

time [µs]

200 400 600 800 1000 1200 1400 1600 1800

−15−10

−50

5

with feedback and feedforward

control

only feedback

(gain = 70)

400 600 800 1000 1200

−1

−0.50

0.51

beam

300 700 1100

1

0

-1

zoomed region

15

10

5

0

-5

acce

lera

ting

pha

se[d

eg]

0 500 1300900 1700

time [µs]

Contributions to Energy Fluctuations

1. Lorentz Force2. Microphonics3. Bunch-to Bunch Charge Fluctuations4. Calibration error of the vector-sum5. Phase noise from master oscillator6. Non-linearity of field detector7. Klystron Saturation8. RF curvature (finite bunch length)9. Wakefield and HOMs

−80 −60 −40 −20 0 20 400

1

2

3

4

5

6

7∆f = - K · Eacc

2

grad

ient

[M

V/m

]

∆f [Hz]

K = 0.9 Hz(MV/m)2

0 500 1000 1500 2000−300

−200

−100

0

100

200

300

time [µs]

detu

nin

g [H

z]

Lorentz Force Detuning of D39 in Chechia

fill: 500 µs

flat: 800 µs

15 MV/m20 MV/m25 MV/m30 MV/m

Figure 3: Influence of radiation pressure on the resonance curve of a sc cavity. a) Static detuning during cw oper-ation and b) dynamical detuning during nominal TESLA pulse.

17:30 18:00 18:30−30

−25

−20

−15

−10

−5

cavity 1

time [h]

detu

nin

g [

Hz]

−40 −30 −20 −10 00

10

20

30

40

detuning [Hz]

no

. o

f m

easu

rem

en

ts

cavity 1 σ = 4 Hz∆f

Figure 2: Fluctuations of the cavity resonance frequency. a) Slow drifts over a period of one hour and b) prob-ability density of the cavity resonance frequency with an rms width of 2Hz - 7Hz.

Microphonics

Lorentz Force Detuning

Operation with Final State Machine

Measure Step Response

T11 T12 … T1n

T21 T22 … T2n

… … … …Tn1 Tn2 … Tnn

Closed LoopIdentification

WaveletFilter

new FFTable

calculateCorrection ofold FF Table

measure Control-Error

Adaptive Feed Forward can handle nonlinear systems throughlinarisation around the operating point.

0 500 1000 1500

−150

−100

−50

0

50

100

150

0 500 1000 1500

−3000

−2000

−1000

0

1000

2000

3000

4000

5000

0 500 1000 1500

−2000

0

2000

4000

6000

8000

10000

12000

14000

16000

tt

t t

∆ff

ffff∆E

few seconds.The calculation of a new feed forward table needs only a

0 500 1000 1500

−2000

0

2000

4000

6000

8000

10000

12000

14000

16000

Adaptive Feedforward

from TTF Console in Milano

Ancillaries: LLRF


Ancillaries: Power Coupler

• TTF III Coupler has a robust and reliable design.

• Extensively power tested with significant margin

• New Coupler Test Stand at LAL, Orsay

10 + 30 New Couplers in construction by industry

Pending Problems

• Long processing time: ~ 100 h

• High cost (> cavity/2)

• Critical assembly procedure

Dedicated laboratory at LAL/Orsay


Ancillaries: Cavity Tuners

The Saclay Tuner in TTF The INFN Blade-Tuner

Successfully operated with superstructures


The X-FEL

50%-60% funded by the German Government - European consensus establishedGreat opportunity for all TESLA Technology based Projects

– Machine reliability according to SRL standards– Industrial mass production of cavities (~ 1000) and modules (> 120)


feed cap

end cap cryomodule

supports

feed box

feed cap transfer line

Cryomodule Test Stand @ DESY

•Under construction

• Commissioning 2005/06


Cry3 adaptation in progress


The Ciemat 2K Quadrupole


Industrial Study

• Technology transfer from Research to Industry

• Review with industry of the cryomodule design and assemblyto focus:

• Cost drivers

• Critical steps of the assembly procedure

• Suggestion based on industrial experience in term of:

• Similar productions

• Labor organization

• Quality control


New QC in cavity production

From Valdemar Singer


EU Funding: CARE-JRA1

JRA1–SRF 5M€ from EU

Improved cavity fabrication

Thin film cavity production

Seamless cavity fabrication

Surface preparation

Materials analysis

Power couplers

Cavity tuners

Low level RF control

Cryostat integration test

Beam diagnostics

CARE is funded at the level of 15.2 M€ over 5 years


TTF: Raw data for trendsEsurf = 2 Eacc for β=1 (TESLA)

Taking into account all data from 1995

1/1/1995 1/1/1997 1/1/1999 1/1/2001 1/1/2003 1/1/2005

0

10

20

30

40

50

60

70

80

90

Emax FE start

Esurf [MV/m]

Date


Average of “best” > 40 MV/mAverage of “safe” (no FE)> 30 MV/m

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.00

10

20

30

40

50

60

70

80

ANL

ANLIPN

MSU

LNL

LANL

LANL

Average TTFChemically etched cavitiesMax Eacc = 28 MV/mFE onset @ 21 MV/m

CEA/CNRS

SNS production

Sur

face

Ele

ctric

Fie

ld [M

V/m

]

β

Field Emission region Field Emission free operation

5 cavitiesTRASCO/RIA

Peak electric field on surface

?

Cavities hitting high magnetic field limitations, as well as TTF, are not taken into account in these averages


Coupler Development at LAL-Orsay

TTF III

Clean room assemblyHigh Power Coupler Test Stand

Alternative Designs


New design with piezos• CARE/JRA-SRF

• SOLEIL upgrades

• larger rigidity

• Fabrication of 2 tuners since beginning of 2005• 12 NOLIAC piezos, 2 PHYTRON stepping motors ordered• Coll. with IPN Orsay: CEA send NOLIAC piezos to IPN for

characterization, and IPN send P.I. piezos for tests on tuners• Coll. with INFN-Milano for measurement with stress sensors @ 2K

New Saclay Tuner for XFEL

HIF0531 May 2005Carlo Pagani 39 Status as on February 1st, 2005

New INFN Blade-Tuner

• Integration of piezos for Lorentz forces and microphonics completed.

• Final Drawing delivered for fabrication.

• Two prototype, including the modified helium tank, were expected by end of June 2005

• Cold tests results by fall 2005 (DESY, BESSY, Cornell?)


CryHoLab at Saclay/Orsay


HIPPI for SPL


HIPPI for SPL


SRF TESLA Technology for ADS

Spallation target & Spallation target & subsub--critical corecritical core

∼5 MeV100 keV

~ 100 MeV ~ 500 MeV~ 200 MeV

β = 0.65β = 0.47 β = 0.85

600 MeV

SC elliptical cavities (700 MHz, 3 sections)SC elliptical cavities (700 MHz, 3 sections)

RFQRFQ

Sour

ceSo

urce

β = 0.35SC or warm CH

SC or warm CH--DTL DTL

structure ? structure ?

RFQRFQ

Sour

ceSo

urce

« X MeV » (between 5 &

50 MeV)

SC or warm CH

SC or warm CH--DTL DTL structure ? structure ?

SC spoke cavities SC spoke cavities (350 MHz, 1 or 2 sections)(350 MHz, 1 or 2 sections)

Beam Beam dumpdump

17

12

13

27

4

825

1

2

26

22

20

28

3

24

9

16

7

6

5

15

23

1831

30

10

19

29

8

1110

21

1411

29

High Energy SectionHigh Energy Section

EU Program named PDS-XADS now moving to EuroTrans

0 2 4 6 8 10 12 14 16 18 20

109

1010

start of electron emission

Test #1 limited by strong field emission

Q0

Eacc [MV/m]

Z501 Z502 - before conditioning Z502 - after conditioning Design Value

multipacting barriers

The accelerator design has been developed for Nuclear WasteTransmutation by an INFN-CEA-CNRS collaboration.

The high energy section is now used by HIPPI and SPL too


A Few Remarks

The interest for the SRF Technology is wide and growing in Europe like in the other two Regions

The TESLA Collaboration achievements with TTF were sufficient to convince ITRP to recommend cold for ILC

EU is plying a positive role in coordinating some SRF activities in different labs and for different projects

That’s fine, but not enough

Documents

SC RF Studies in Europe - · – Final cleaning and drying (UV for bacteria and on line ... from G. Geschonke’s Poster for the ITRP visit to DESY. HIF05 Carlo Pagani 9 31 May 2005