Q-Slope at High Gradients ( Niobium Cavities ) Review about Experiments and Explanations

Q-Slope at High GradientsQ-Slope at High Gradients ( Niobium Cavities ) ( Niobium Cavities )

Review about ExperimentsReview about Experimentsand Explanationsand Explanations

Bernard VISENTIN CEA - SaclayBernard VISENTIN CEA - Saclay

SRF’2003 ( 11 SRF’2003 ( 11 thth Workshop ) Workshop ) Q-Slope at High GradientsQ-Slope at High Gradients Bernard VisentinBernard Visentin

2

IntroductionIntroduction

Q degradation at high accelerating fieldsQ degradation at high accelerating fields

Empirical Cure with cavity bakingEmpirical Cure with cavity baking

Problem only push away fartherProblem only push away farther

Understand Q-slope origin Understand Q-slope origin


3

OutlineOutline

Q-Q-Slope : Definition and FeaturesSlope : Definition and Features

Baking EffectBaking EffectExperimental Observations ( Q slope - RBCS - Rres ) Standard Chemistry ( BCP ) and Electropolishing ( EP )Consequences on Nb Surface ( diffusion process – oxides – BC )

Theoretical ModelsTheoretical ModelsDifferences between BCP & EPInterface OxideSuperconducting Parameters Change

Experiments Experiments Models Models

ConclusionConclusion


4

Q-Slope : Definition and FeaturesQ-Slope : Definition and Features

quality factor quality factor strong degradation strong degradation

EEaccacc > 20 MV/m> 20 MV/m TTF cavities ( B TTF cavities ( Bpp > 85 mT ) > 85 mT ) field emission not involved ( field emission not involved ( no e no e --, no X rays, no X rays ) ) T map : T map : global heatingglobal heating ( B ( Bpp max ) max ) limitation by RF power supply or quenchlimitation by RF power supply or quench seemingly a typical feature of seemingly a typical feature of BCPBCP cavities cavities

““European Headache”European Headache”

superiority of superiority of EPEP

without Q-slopewithout Q-slope

( E. Kako et al. - SRF ’99 - Santa Fe )

( L. Lilje et al. - SRF ’99 - Santa Fe )

K. Saïto et al.

SRF ’97

( Abano Terme )

( Nb 1-cell cavity )

C1-03 / S-3 ( EP cavity )KEK 3

1E+9

1E+10

1E+11

0 10 20 30Eacc ( MV/m )

Q0

quench

1E+09

1E+10

1E+11

0 10 20 30Eacc (MV/m)

Q0

C1-16 ( 1.3 GHz )

no electronsno X-rays

RFpower


5

Baking Effect on BCP Cavities Baking Effect on BCP Cavities ( Q ( Q slopeslope – R – RBCSBCS – R – Rresres ) )

““in-situ” baking discovered on in-situ” baking discovered on BCPBCP cavity cavity

slope improvement ( 90 < T < 120°C ) - degradation ( T > slope improvement ( 90 < T < 120°C ) - degradation ( T > 150°C ) 150°C )

C1-05 ( BCP cavity )

1E+08

1E+09

1E+10

1E+11

0 10 20 30Eacc ( MV/m )

Q0

no baking90°C - 48h110°C - 48h4.2 K (no baking)4.2 k ( 90°C )4.2 K ( 110°C )

quench

( B. Visentin et al. – EPAC ’1998 - Stockholm )


1

10

100

1000

0,2 0,3 0,4 0,5 0,6 0,7

1/T ( K -1 )

RS

(nW)

no baking

90°C - 48h

110°C - 48h


6

Baking Effect on EP CavitiesBaking Effect on EP Cavities

Same phenomenon on Same phenomenon on E.P.E.P. cavities cavities

before baking: Q-slope identical to BCP

after baking : Q-slope improvement

C1-03 / S-3 ( EP cavity )KEK 9 & 10

1E+09

1E+10

1E+11

0 10 20 30 40Eacc ( MV/m )

Q0

no baking

110°C / 30h

quenchRF powerlimitationapparent superiority of EP reported before ?

cleaning procedure at KEK

wet cavities ( High Power Rinsing )

directly pumped out and baked at 85°C/20h

to accelerate pumping speed ( Saclay cavity – EP & tested @ KEK )

1E+09

1E+10

1E+11

1E+12

0 10 20 30 40Eacc (MV/m)

Q0

C1-03 / S-3 ( EP - KEK 9 )D1-22 ( EP - Saclay A1 )C1-15 ( BCP - Saclay I1 )C1-16 ( BCP - Saclay P1 )C1-10 ( BCP - Saclay N1 )

Q-slopes before baking ( BCP and EP cavities )

RF PowerLimit

P. Kneisel. – TUP 044

K. Saïto. – TUP 031

L. Lilje et al. – TUA 001

B. Visentin et al. – TUP 015

SRF ’ 99

Santa Fe


7

Surface Re-Oxidation after Baking ?Surface Re-Oxidation after Baking ?

Unaltered Q-slopeUnaltered Q-slope

after after Air Air exposure ( 3 hours to 2 months ) followed by exposure ( 3 hours to 2 months ) followed by :

High PressureHigh Pressure Water Water Rinse + Drying ( laminar flow – 3 h ) Rinse + Drying ( laminar flow – 3 h )

- standard conditioning for RF tests -- standard conditioning for RF tests -

3 hours ( cavity closed )

8 hours ( cavity closed )

RF test bench

1 day ( cavity closed )

9 days ( cavity open )

( under laminar-flow : class 10 )

in clean-room

2 months ( cavity open )

left on the shelf

D1-22 ( EP cavity )

1E+08

1E+09

1E+10

1E+11

0 10 20 30 40Eacc ( MV/m )

Q0

A1 - no bakingA2 - baking in situ 100°C /48hA7 - air exposure 1day + HPRA10 - air exposure 2month + HPR

quench


8

Baking at the Atmospheric Pressure ?Baking at the Atmospheric Pressure ?

BCP + High Pressure RinseBCP + High Pressure Rinse

WetWet Cavity inside Drying Oven ( 110°C / 60 h ) Cavity inside Drying Oven ( 110°C / 60 h )

@ Atm. Pressure - no pumping @ Atm. Pressure - no pumping

new H.P.R. for RF testnew H.P.R. for RF test

BCP Cavity ( C1-10 )

Q-slope improvement

similar to “in-situ baking”

( B. Visentin et al. – this workshop )

1E+09

1E+10

1E+11

0 10 20 30Eacc (MV/m)

Q0

C1-10 O1 ( BCP )

C1-10 S1 ( BCP + baking @ Atm. Press. )

Quenchnon "in-situ" baking


9

Differences between BCP and EPDifferences between BCP and EP higher efficiency of baking on EP cavities ( from 85°C )higher efficiency of baking on EP cavities ( from 85°C ) residual slope on BCP cavities even with baking ( 120°C )residual slope on BCP cavities even with baking ( 120°C )

higher quench field for EP cavities ( 40 MV/m )higher quench field for EP cavities ( 40 MV/m )

surface roughnesssurface roughness

( R.L. Geng et al. - SRF ’99 – Santa Fe )

BCP ( 117 m ) EP ( 90 m )

5-9 m ( statistic on step height) 2-5 m

100 100 mm100 100 mm

C1-10 ( BCP cavity )N 1 & 2

1E+09

1E+10

1E+11

0 10 20 30 40Eacc ( MV/m )

Q0

no baking

120°C / 60h

quench

RF powerlimitation

C1-03 / S-3 ( EP cavity )KEK 9 & 10

1E+09

1E+10

1E+11

0 10 20 30 40Eacc ( MV/m )

Q0

no baking

110°C / 30h

quenchRF powerlimitation

BCP

EP


10

Some Exceptions ( ? )Some Exceptions ( ? )

TotalTotal removal of Q-slope after baking ( removal of Q-slope after baking ( BCPBCP cavities ) cavities )( with or without quench fields at 40 MV/m )

1E+09

1E+10

1E+11

1E+12

0 10 20 30 40Eacc (MV/m)

Q0

C1-03 / S-3 ( EP - KEK 10 )

C1-15 ( BCP - Saclay I2 )

C1-16 ( BCP - Saclay P2 ) Quench

( B. Visentin et al. – EPAC’2002 – Paris & this workshop )

Two Nb cavities : C1-15 & C1-16 ( BCP + 120°C/60h )

C1-15 ( inner surface )

not very smooth

large grains : 2-3 mm2

high steps : 4 to 8 m

( W. Singer et al. – SRF ’2001 - Tsukuba )

One NbCu clad cavity : 1NC2 ( BCP + 140°C/30h )

1 cm1 cm( P. Kneisel et al. – SRF ’1995 – Gif/Yvette )

Nb cavity “defect free” : ( BCP but no baking specified )


11

Baking Consequences on Nb Surface (1)Baking Consequences on Nb Surface (1)

RRBCSBCS ( T ( Tbakebake ) : ) : R RBCSBCS ( baking time ) ( baking time ) saturation

diffusion process

( 300 nm )

( P. Kneisel - SRF ’99 - Santa Fe )

kTFLBCS e

TAR

2

,,

L = 31 nm

F = 62 nm

= 1.46 meV

T = 4.2 K

RBCS @ T = 4.2 K

Tbake = 145°C

400

500

600

700

800

900

1000

1 10 100 1000 10000

( nm )

RBCS

( nW )


12


Influence of oxide layers on Nb surface resistanceInfluence of oxide layers on Nb surface resistance

( Nb( Nb22OO55 and NbO ) and NbO )

Oxygen can diffuse at low temperature Oxygen can diffuse at low temperature

Change Change

of the structure oxide of the structure oxide

after baking after baking

( Nb( Nb22OO55 and NbO - NbO and NbO - NbO0.20.2 ) )

( F. Palmer – IEEE Trans. Mag. - 1987 )

C. Antoine et al. - SRF ’99 - Santa Fe

A. Dacca et al. - Applied Surf. Science - 1998

Q. Ma et al. - SRF ’01 - Tsukuba ( A. Daccà - sample 4 - T=150°C )


13


Surface Magnetic Field : Surface Magnetic Field : ( B. Steffen - TTF Meeting - 2003 )

Susceptibility measurements ( on sample )

Surface field : BC3surf = 1.7 BC2

bulk

larger field for EP compare to BCP

All values are increased by baking

( interpreted by enhancement of impurities : O ? )


14

Experiments ModelsExperiments Models

Difference ( EP/BCP )Difference ( EP/BCP )

Surface RoughnessSurface Roughness

( grain boundaries )( grain boundaries )

Modification ofModification of

Interface Oxide / MetalInterface Oxide / Metal

( Oxygen Diffusion )( Oxygen Diffusion )

Change of Change of

Superconducting ParametersSuperconducting Parameters

( R( RBCSBCS , B , BCC … ) … )

Magnetic Field Enhancement Magnetic Field Enhancement

Interface Tunnel ExchangeInterface Tunnel Exchange

Thermal FeedbackThermal Feedback

Magnetic Field Dependence of Magnetic Field Dependence of

Granular Superconductivity Granular Superconductivity


15

Theoretical Models Theoretical Models Experiments Experiments

1E+09

1E+10

1E+11

1E+12

0 10 20 30 40Eacc (MV/m)

Q0

C1-03 / S-3 ( EP - KEK 10 )


C1-16 ( BCP - Saclay P2 ) Quench

1E+09

1E+10

1E+11

1E+12

0 10 20 30 40Eacc (MV/m)

Q0

C1-03 / S-3 ( EP - KEK 9 )D1-22 ( EP - Saclay A1 )C1-15 ( BCP - Saclay I1 )C1-16 ( BCP - Saclay P1 )C1-10 ( BCP - Saclay N1 )

Q-slopes before baking ( BCP and EP cavities )

RF PowerLimit

Q-Slope

Fit

Slope before baking ( EP BCP )

Slope Improvement after baking

No change after 2 m.

air exposure

Slope after baking ( EP < BCP )

Exceptional Results ( BCP )

Quench ( EP > BCP )

BCP Quench unchanged

after baking

D1-22 ( EP cavity )

1E+08

1E+09

1E+10

1E+11

0 10 20 30 40Eacc ( MV/m )

Q0

A1 - no bakingA2 - baking in situ 100°C /48hA7 - air exposure 1day + HPRA10 - air exposure 2month + HPR

quench

C1-03 / S-3 ( EP cavity )KEK 9 & 10

1E+09

1E+10

1E+11

0 10 20 30 40Eacc ( MV/m )

Q0

no baking

110°C / 30h

quenchRF power

limitation


1E+08

1E+09

1E+10

1E+11

0 10 20 30Eacc ( MV/m )

Q0

no baking

90°C - 48h

110°C - 48h quench


16

Magnetic Field Enhancement at G.B.Magnetic Field Enhancement at G.B.( J. Knobloch - SRF ’99 - Santa Fe ) microstructure on RF surface

( surface roughness - step height 10 m )

magnetic field enhancement

normal conducting region if

factor ( BCP )

Hm

Cm HH

5.26.1 m

( K. Saïto - PAC ’2003 - Portland )

EP : ( HC/m= 223 mT ) m=1

BCP : ( HC/m = 95 mT ) m=2.34electromagnetic code + thermal simulation Q0(Eacc)

Q-slope origin

the most dissipative G.B. quench (equator)


17

Comments ( H - enhancement )Comments ( H - enhancement )

Explanations :Explanations :

Q-slope for BCP before baking ( good simulation )

Q-slope improvement after baking ( HC )

better slope for EP after baking ( m lower ~ 1 )

Not consistent with :Not consistent with :

slope before baking for EP cavities

( same slope with m lower and HC higher than BCP )

flat slope ( and 40 MV/m ) on BCP cavities C1-15 & C1-16

( roughness : 4 to 8 m > 2 m high m )

quench value unchanged for BCP after baking ( in spite of HC )


18

Interface Tunnel ExchangeInterface Tunnel Exchange

( J. Halbritter - SRF ’01 – Tsukuba )

( IEEE Trans. on Appl. Supercond. 11, 2001 )

RF field on

metallic surface

metalcleanfornegligibleZemissionelectroncausesE

seriesTaylorHHRRZHE

CHH ...1 22*0

Dielectric oxide layer on metal enhancement of ZE by I.T.E.

( localized states of Nb2O5-y and density of state of Nb )

with electron diffusion at NbOx - Nb2O5-y interface

I.T.E. quantitative description of Q-slope

E

C

E eR*

80:

:* ERRbyfittednallyconvention

factortenhancemenfieldelectricE

ITE reduction by :

•smoothening surface ( EP )

( * and E° )

•baking : Nb2O5-y vanished - better interface

( reduction of localised states )

valueonsetEatstarting

1E+09

1E+10

1E+11

0 10 20 30Eacc (MV/m)

Q0

C1-16 ( 1.3 GHz )


RFpower

RH

RE

E°


19

Comments ( I.T.E. )Comments ( I.T.E. )

Explanations :Explanations :

Q-slope improvement after baking ( Nb2O5 )

better slope for EP after baking ( smooth surface - lower * )

Not consistent with :Not consistent with :

similar slopes ( before baking ) for EP and BCP cavities

( surface roughness and * are different )

unaltered slope after a surface re-oxidation ( Nb2O5 - 2 months later )

exceptional flat slopes on BCP cavities C1-15 & C1-16 ( in spite of roughness : 4 to 8 m - higher * )


20

Thermal FeedbackThermal Feedback

Temperature Dependence of Surface ResistanceTemperature Dependence of Surface Resistance

TT

RTRTRHRPRTH S

SSSSdissthermS

)()(2/ 02

( V. Kurakin - EPAC’94 - London )

( E. Haebel - TTF Meeting - 1998 )

).1( 2

0

acc

SS EC

TRTR

2

0 . accS EbaRGQ

T

RC

mVC

S8

215

10.2

/10.1fit parameter :

( B.V. et al. SRF’99 - Santa Fe )

T

R

h

eC S

KNb

Nb

9

2

0

9

10.2

110.4

2

1

baking effect :

kTFLBCS e

TAR

2

,,

AT

RS


21

Energy Gap DependenceEnergy Gap Dependence

Exponential variation Exponential variation

kTeT

ARQGR FLresS

2

0 ),,(

magnetic field dependence of

2210 CHHH

( A. Didenko - EPAC ’ 96 - Sitges )

( V. Mathur et al. - Phys. Rev. Let. 9, 374 - 1962 )

only rigorous and experimentally proved

for thin films

( normal state transition 2nd order if d/ < 51/2 )

for T/TC < 0.36

for bulk material ( d >> )

(H) : few % variation

BC = 180 mT BC = 195 mT

BC “fit factor”

Rres, A, (0) from RS(1/T) at low field

( B.V. et al. - EPAC ’ 98 - Stockholm )


22

Granular SuperconductivityGranular Superconductivity

( H. Safa et al. – SRF ’99 – Santa Fe )

Grain Boundaries contribution to surface resistance ?Grain Boundaries contribution to surface resistance ?

( polycrystalline nature of Nb ) - Grain Boundary weak link ( Josephson junction )

( B. Bonin and H. Safa - Superc. Sci. Tech. 4, 1991 )

Theory valid for sputtered thin films

effect negligible for bulk niobium ( grains ~ 10m ) :

exception :

segregation of impurities located at grain boundaries

Difficulties to apprehend the baking as a way to clean G.B.Difficulties to apprehend the baking as a way to clean G.B.

( low temperature - diffusion O )

Experiment on Grain Boundaries Specific Resistance


23

Similarities EP / Similarities EP / BCPBCP

Q-Slope

Fit

Slope before baking ( EP BCP )

Slope Improvement after baking

Slope after baking ( EP < BCP )

No change after 2 m.

air exposure

Exceptional Results ( BCP )

Quench ( EP > BCP )

BCP Quench unchanged

after baking Validity

Magnetic Field

Enhancement

YY

NN ( m et HC )

YY ( HC )

YY ( m < ; HC > )

-- NN ( high m )

YY ( m < ; HC > )

NN ( HC )

YY

Interface Tunnel

Exchange YY ( E8 )

NN ( )

YY ( Nb2O5-y )

YY ( low )

NN ( Nb2O5-y )

NN ( high )

-- --

YY

Thermal Feedback YY

( parab. )

YY

YY ( RBCS Rres )

NN

--

NN

-- -- NN ( coeff. C )

Magnetic Field

Dependence of

YY ( expon. )

NN ( HC )

YY ( HC )

YY ( HC > )

--

NN

-- -- NN ( thin film )

Segregation of Impurities -- NN

( segreg. )

NN ( only O )

-- -- YY ( cleaning )

-- --

YY


24

Experimental Program at J.Lab.Experimental Program at J.Lab.

“ “ H enhancement at grain bound. ” H enhancement at grain bound. ” “ Interface Tunnel “ Interface Tunnel Exchange ”Exchange ”

• Single cell cavity ( BCP - EP - w/o Baking ) excited in modes TM010 or TM011 : HS

• Two cell cavity TM010 ( 0- mode ) : scan the surface ( E, H )

• Q0 ( Bpeak ) - ( BCP - EP - w/o Baking )

• Preliminary results :( G. Ciovati et al. - PAC ’ 2003 - Portland )


25

ConclusionConclusion

Experiments and Models have to progress in the futureExperiments and Models have to progress in the futureto understand the phenomenon and to cure itto understand the phenomenon and to cure it

all the more so since Q-slope is not totally removed by baking Q-slope is not totally removed by baking ( even for EP cavities )( even for EP cavities )

if quench improvement possible ( > 40 MV/m ) Q-slope appearance

0,0

1,0

2,0

3,0

4,0

5,0

6,0

7,0

8,0

9,0

0 500 1000 1500 2000

E2acc

( MV/m )

R/R0

D1-22 ( EP - Saclay A2 )C1-03 ( EP - KEK 10 )C1-15 ( BCP - Saclay I2 )C1-16 ( BCP - Saclay P2 )C1-10 ( BCP - Saclay N2 )

High-Field Slopes after baking

( BCP and EP cavities )

0

1

2

3

4

5

6

7

8

9

0 500 1000 1500 2000

E2acc

( MV/m )2

R/R0

D1-22 ( EP - Saclay A1 )

C1-03 ( EP - KEK 9 )


C1-16 ( BCP - Saclay P1 )

C1-10 ( BCP - Saclay N1 )

High-Field Slopes before baking



26

Papers at this WorkshopPapers at this Workshop Q-slope

A Review of High-Field Q-Slope Studies at Cornell - H. Padamsee et al. ( Mo-P14 )Why does the Q-slope of a Nb cavity change…? - I.V. Bazarov et al. ( Th-P02 )Q-slope analysis of niobium SC RF cavities - K Saito ( Th-P19 )Q-Slope : Comparison BCP and EP - Modification by Plasma… - B. Visentin et al. ( Mo-P19 )

Baking

A Pleasant Surprise: Mild Baking Gives Large Improvement… - G. Eremeev et al. ( Mo-P18 )Low temperature heat treatment effect on high-field EP cavities - J. Hao et al. ( Mo-P16 )Effect of low temperature baking on niobium cavities - G. Ciovati et al. ( We-O14 )

Surface Analysis

In situ XPS investigation of the baking effect … - K Kowalski et al. ( Th-P09 ) Near-Surface Composition of Electropolished Niobium … - A.M. Valente et al. ( Mo-P15 )Grain boundary specific resistance and RRR measurements… - S. Berry et al. ( Th-P03 )


27

0

10

20

30

40

50

60

70

0 200 400 600 800 1000 1200 1400 1600 1800

E2acc ( MV/m )2

R/R0 D1-22 ( EP - Saclay A1 )

C1-03 ( EP - KEK 9 )






0

1

2

3

4

5

6

7

8

9

0 200 400 600 800 1000 1200 1400 1600 1800

E2acc ( MV/m )2

R/R0 D1-22 ( EP - Saclay A2 )C1-03 ( EP - KEK 10 )C1-15 ( BCP - Saclay I2 )C1-16 ( BCP - Saclay P2 )C1-10 ( BCP - Saclay N2 )Théorie

High-Field Slopesafter baking


0

1

2

3

4

5

6

7

8

9

0 200 400 600 800 1000 1200 1400 1600 1800

E2acc ( MV/m )2

R/R0 D1-22 ( EP - Saclay A1 )

C1-03 ( EP - KEK 9 )







28

HH22-slope ( Intermediate Fields )-slope ( Intermediate Fields )

0,0

1,0

2,0

3,0

4,0

5,0

6,0

7,0

8,0

9,0

0 200 400 600 800 1000 1200 1400 1600 1800

E2acc

( MV/m )2

R/R0

D1-22 ( EP - Saclay A2 )C1-03 ( EP - KEK 10 )C1-15 ( BCP - Saclay I2 )C1-16 ( BCP - Saclay P2 )C1-10 ( BCP - Saclay N2 )Théorie

High-Field Slopesafter baking


OeH

HHR

R

C

C

20003.3*

22*0

1E+09

1E+10

1E+11

1E+12

0 10 20 30 40Eacc (MV/m)

Q0

D1-22 ( EP - Saclay A2 )C1-03 / S-3 ( EP - KEK 10 )C1-15 ( BCP - Saclay I2 )C1-16 ( BCP - Saclay P2 )C1-10 ( BCP - Saclay N2 ) Quench

Q-slopes after baking ( BCP and EP cavities )

22*0 1 CH HHRR


29

Surface Treatment by PlasmaSurface Treatment by Plasma

Correlation between O and Q-slope Correlation between O and Q-slope

preliminary results of recent experiment

surface treatment of Nb cavity by oxygen plasma

( RCE discharge - E O+~50 eV - no sputtering )

ionic implantation & diffusion

XPS sample analysis show NB2O5

O2 : 5.10-3 mbar

f = 2.45 GHz

B = 875 G

PRF : 1500 W

time : 1/2 hour

Tsurface < 80°C

C1-17 O/P BCP Cavity

1,E+09

1,E+10

1,E+11

0 5 10 15 20 25 30

Eacc (MV/m )

Q0

Standard BCP

After O plasma

( B. Visentin et al. – this workshop )


30

Quench position on BCP cavitiesQuench position on BCP cavities

1

3

5

7

9

11

13

15

17

30

40

51

61

72

82

92

10

0

04008001200160020002400280032003600400044004800520056006000

T (mK)

Thermal SensorPosition

( degree )

C1-17 ( S1 )

181

199

215

231

1 2 3 4 5 6 7 8 91

01

11

21

31

41

51

61

7

0400800

12001600200024002800

3200

3600

4000

4400

4800

5200

5600

T (mK)

Position(degree )Thermal Sensor

C1-17 ( Q1 )

Quench Position

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

0 90 180 270 360 Position ( degree )

Th

erm

al s

en

so

r (

1:1

cm

) C1-10

C1-15

C1-17

upper iris

lower iris

equator - EB weld ( 5 mm )

11

10

9

EB weld


31

Frequency Dependence of Q-slope Frequency Dependence of Q-slope

1E+09

1E+10

1E+11

0 10 20 30Eacc (MV/m)

Q0

A1-02 ( 700 MHz )

C1-16 ( 1300 MHz )

L1-05 ( 1500 MHz )

quench


RFpower

RFpower

1E+09

1E+10

1E+11

0 20 40 60 80 100 120 140

Bp (mT)

Q0

A1-02 ( 700 MHz )

C1-16 ( 1300 MHz )


RFpower

Documents

Q-Slope at High Gradients ( Niobium Cavities ) Review about Experiments and Explanations