Transcript Q-Slope at High Gradients: Review about Experiments and

Q-Slope at High Gradients
( Niobium Cavities )
Review about Experiments
and Explanations
Bernard VISENTIN
CEA - Saclay
2
Introduction
 Q degradation at high accelerating fields
 Empirical Cure with cavity baking
 Problem only push away farther
 Understand Q-slope origin
SRF’2003 ( 11 th Workshop )
Q-Slope at High Gradients
Bernard Visentin
3
Outline
 Q-Slope : Definition and Features
 Baking Effect
Experimental Observations ( Q slope - RBCS - Rres )
Standard Chemistry ( BCP ) and Electropolishing ( EP )
Consequences on Nb Surface ( diffusion process – oxides – BC )
 Theoretical Models
Differences between BCP & EP
Interface Oxide
Superconducting Parameters Change
 Experiments  Models

SRF’2003 ( 11 th Workshop )
Conclusion
Q-Slope at High Gradients
Bernard Visentin
4
Q-Slope : Definition and Features
quality factor  strong degradation





Eacc > 20 MV/m TTF cavities ( Bp > 85 mT )
field emission not involved ( no e -, no X rays )
T map : global heating ( Bp max )
limitation by RF power supply or quench
seemingly a typical feature of BCP cavities
( L. Lilje et al. - SRF ’99 - Santa Fe )
1E+11
C1-16 ( 1.3 GHz )
Q0
1E+10
“European Headache”
superiority of EP
without Q-slope
1E+11
Q0
no electrons
no X-rays
K. Saïto et al.
RF
power
10
20
Eacc (MV/m)
30
( Abano Terme )
que nch
1E+9
0
( Nb 1-cell cavity )
SRF’2003 ( 11 th Workshop )
C1-03 / S-3 ( EP cavity )
KEK 3
SRF ’97
1E+09
0
1E+10
10
20
Eacc ( MV/m )
30
( E. Kako et al. - SRF ’99 - Santa Fe )
Q-Slope at High Gradients
Bernard Visentin
5
Baking Effect on BCP Cavities
( Q slope – RBCS – Rres )
“in-situ” baking discovered on BCP cavity
slope improvement ( 90 < T < 120°C ) - degradation ( T > 150°C )
1E+11
Q0
C1-05 ( BCP cavity )
1000
RS
(nW)
1E+10
no baking
90°C - 48h
110°C - 48h
4.2 K (no baking)
4.2 k ( 90°C )
4.2 K ( 110°C )
1E+09
C1-05 ( BCP cavity )
100
quench
no baking
10
90°C - 48h
110°C - 48h
1E+08
0
10
20
30
Eacc ( MV/m )
1
0,2
( B. Visentin et al. – EPAC ’1998 - Stockholm )
SRF’2003 ( 11 th Workshop )
Q-Slope at High Gradients
0,3
0,4
1/T ( K
0,5
-1
0,6
0,7
)
Bernard Visentin
6
Baking Effect on EP Cavities
Same phenomenon on E.P. cavities
before baking: Q-slope identical to BCP
1E+12
Q-slopes before baking
( BCP and EP cavities )
Q0
P. Kneisel. – TUP 044
K. Saïto. – TUP 031
SRF ’ 99
Santa Fe
L. Lilje et al. – TUA 001
B. Visentin et al. – TUP 015
1E+11
after baking : Q-slope improvement
1E+10
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 )
1E+11
RF Power
Limit
Q0
1E+09
0
10
20
30
40
Eacc (MV/m)
C1-03 / S-3 ( EP cavity )
KEK 9 & 10
1E+10
quench
apparent 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
SRF’2003 ( 11 th Workshop )
RF power
limitation
no baking
110°C / 30h
1E+09
0
10
20
30
40
Eacc ( MV/m )
( Saclay cavity – EP & tested @ KEK )
Q-Slope at High Gradients
Bernard Visentin
7
Surface Re-Oxidation after Baking ?
Unaltered Q-slope
after Air exposure ( 3 hours to 2 months ) followed by :
High Pressure Water Rinse + Drying ( laminar flow – 3 h )
- standard conditioning for RF tests  3 hours ( cavity closed )
 8 hours ( cavity closed )
RF test bench
1E+11
D1-22 ( EP cavity )
Q0
1E+10
 1 day ( cavity closed )
 9 days ( cavity open )
( under laminar-flow : class 10 )
in clean-room
A1 - no baking
A2 - baking in situ 100°C /48h
A7 - air exposure 1day + HPR
A10 - air exposure 2month + HPR
1E+09
1E+08
0
 2 months ( cavity open )
left on the shelf
SRF’2003 ( 11 th Workshop )
quench
Q-Slope at High Gradients
10
20
Eacc ( MV/m )
30
40
Bernard Visentin
8
Baking at the Atmospheric Pressure ?
BCP + High Pressure Rinse
Wet Cavity inside Drying Oven ( 110°C / 60 h )
@ Atm. Pressure - no pumping
new H.P.R. for RF test
1E+11
Q0

BCP Cavity ( C1-10 )

Q-slope improvement

1E+10
non "in-situ" baking
similar to “in-situ baking”
Quench
C1-10 O1 ( BCP )
C1-10 S1 ( BCP + baking @ Atm. Press. )
1E+09
0
10
20
30
Eacc (MV/m)
( B. Visentin et al. – this workshop )
SRF’2003 ( 11 th Workshop )
Q-Slope at High Gradients
Bernard Visentin
9
Differences between BCP and EP
 higher efficiency of baking on EP cavities ( from 85°C )
 residual slope on BCP cavities even with baking ( 120°C )
1E+11
1E+11
Q0
Q0
C1-10 ( BCP cavity )
N1&2
 BCP
1E+10
C1-03 / S-3 ( EP cavity )
KEK 9 & 10
1E+10
quench
no baking
quench
120°C / 60h
RF power
limitation
110°C / 30h
EP 
1E+09
0
10
RF power
limitation
no baking
20
30
40
1E+09
0
10
20
Eacc ( MV/m )
30
40
Eacc ( MV/m )
 higher quench field for EP cavities ( 40 MV/m )
 surface roughness
100 mm
100 mm
( R.L. Geng et al. - SRF ’99 – Santa Fe )
 BCP ( 117 mm )
5-9 mm
SRF’2003 ( 11 th Workshop )
EP ( 90 mm ) 
( statistic on step height)
Q-Slope at High Gradients
2-5 mm
Bernard Visentin
10
Some Exceptions ( ? )
Total removal of Q-slope after baking ( BCP cavities )
( with or without quench fields at 40 MV/m )
Nb cavity “defect free” : ( BCP but no baking specified )
( P. Kneisel et al. – SRF ’1995 – Gif/Yvette )
C1-15 ( inner surface ) 
1 cm
not very smooth
large grains : 2-3 mm2
high steps : 4 to 8 mm
1E+12
Q0
1E+11
One NbCu clad cavity : 1NC2 ( BCP + 140°C/30h )
( W. Singer et al. – SRF ’2001 - Tsukuba )
1E+10
C1-03 / S-3 ( EP - KEK 10 )
C1-15 ( BCP - Saclay I2 )
C1-16 ( BCP - Saclay P2 )
Quench
1E+09
Two Nb cavities : C1-15 & C1-16 ( BCP + 120°C/60h )
0
10
20
30
40
Eacc (MV/m)
( B. Visentin et al. – EPAC’2002 – Paris & this workshop )
SRF’2003 ( 11 th Workshop )
Q-Slope at High Gradients
Bernard Visentin
11
Baking Consequences on Nb Surface (1)
RBCS ( Tbake ) : 
RBCS  ( baking time )  saturation
diffusion process
( 300 nm )
RBCS @ T = 4.2 K
Tbake = 145°C
1000
( P. Kneisel - SRF ’99 - Santa Fe )
RBCS
( nW900)
800
RBCS  AL , F ,  
2
T
e kT
700
L = 31 nm
600
F = 62 nm
500
 = 1.46 meV
400
1
10
100
1000
10000
T = 4.2 K
 ( nm )
SRF’2003 ( 11 th Workshop )
Q-Slope at High Gradients
Bernard Visentin
12
Baking Consequences on Nb Surface (2)
( F. Palmer – IEEE Trans. Mag. - 1987 )
Influence of oxide layers on Nb surface resistance
( Nb2O5 and NbO )
Oxygen can diffuse at low temperature
Change
of the structure oxide
after baking
( Nb2O5  and NbO - NbO0.2  )
A. Dacca et al. - Applied Surf. Science - 1998
C. Antoine et al. - SRF ’99 - Santa Fe
Q. Ma et al. - SRF ’01 - Tsukuba
SRF’2003 ( 11 th Workshop )
( A. Daccà - sample 4 - T=150°C )
Q-Slope at High Gradients
Bernard Visentin
13
Baking Consequences on Nb Surface (3)
Surface Magnetic Field :
( B. Steffen - TTF Meeting - 2003 )
Susceptibility measurements ( on sample )
Surface field :
BC3surf = 1.7 BC2bulk
larger field for EP compare to BCP
All values are increased by baking
( interpreted by enhancement of impurities : O ? )
SRF’2003 ( 11 th Workshop )
Q-Slope at High Gradients
Bernard Visentin
14
Experiments
 Difference ( EP/BCP )
Surface Roughness
( grain boundaries )
Models
Magnetic Field Enhancement
Interface Tunnel Exchange
 Modification of
Interface Oxide / Metal
( Oxygen Diffusion )
Thermal Feedback
 Change of
Superconducting Parameters
( RBCS , BC … )
SRF’2003 ( 11 th Workshop )
Magnetic Field Dependence of 
Granular Superconductivity
Q-Slope at High Gradients
Bernard Visentin
15
Theoretical Models  Experiments
Slope
Slope
No change
Slope
Exceptional
BCP Quench
Quench
Q-Slope
before baking Improvement after 2 m.
after baking
Results
unchanged
Fit
( EP > BCP )
( BCP )
after baking
( EP  BCP ) after baking air exposure ( EP < BCP )
1E+11
Q0
1E+11
Q0
C1-05 ( BCP cavity )
1E+10
C1-03 / S-3 ( EP cavity )
KEK 9 & 10
1E+10
no baking
90°C - 48h
110°C - 48h
1E+09
quench
quench
RF power
limitation
no baking
110°C / 30h
1E+08
1E+09
0
10
20
30
0
40
10
Eacc ( MV/m )
20
30
Eacc ( MV/m )
1E+12
Q-slopes before baking
( BCP and EP cavities )
Q0
1E+11
D1-22 ( EP cavity )
Q0
1E+11
1E+12
1E+10
1E+10
Q0
1E+11
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 )
A1 - no baking
A2 - baking in situ 100°C /48h
A7 - air exposure 1day + HPR
A10 - air exposure 2month + HPR
1E+09
RF Power
Limit
quench
1E+10
C1-03 / S-3 ( EP - KEK 10 )
1E+09
C1-15 ( BCP - Saclay I2 )
0
10
20
30
Eacc (MV/m)
SRF’2003 ( 11 th Workshop )
40
1E+08
C1-16 ( BCP - Saclay P2 )
0
10
20
Eacc ( MV/m )
30
Q-Slope at High Gradients
40
Quench
1E+09
0
10
20
30
40
Eacc (MV/m)
Bernard Visentin
16
Magnetic Field Enhancement at G.B.
microstructure on RF surface
( J. Knobloch - SRF ’99 - Santa Fe )
( surface roughness - step height 10 mm )
magnetic field enhancement
normal conducting region if
factor
1.6   m  2.5
m H
 m H  HC
( BCP )
Q-slope origin
the most dissipative G.B.  quench (equator)
( K. Saïto - PAC ’2003 - Portland )
EP : ( HC/m= 223 mT )
electromagnetic code + thermal simulation  Q0(Eacc)
SRF’2003 ( 11 th Workshop )
BCP : ( HC/m = 95 mT )
Q-Slope at High Gradients
m=1
m=2.34
Bernard Visentin
17
Comments ( H - enhancement )
 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 :
 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 mm > 2 mm  high m )
 quench value unchanged for BCP after baking ( in spite of HC  )
SRF’2003 ( 11 th Workshop )
Q-Slope at High Gradients
Bernard Visentin
18
Interface Tunnel Exchange
RF field on





metallic surface

 R H  R 0 1   * H 2 H C2  ...
H   Z H
E
 causes
electron em ission   Z E

 Taylor
 negligible
series 
for clean m etal 
Dielectric oxide layer on metal  enhancement of ZE by I.T.E.
 
conventionnally fitted by : R E  R 0 E 
8
I.T.E.  quantitative description of Q-slope
e
C
 E
*
starting at E onset value
with electron diffusion at NbOx - Nb2O5-y interface
 * : electric field enhancem en
t factor

RE
( localized states of Nb2O5-y and density of state of Nb )

RH
1E+11
C1-16 ( 1.3 GHz )
Q0
E°
1E+10
no electrons
no X-rays
ITE reduction by :
RE
• smoothening surface ( EP )
1E+09
0
( *  and E°  )
• baking : Nb2O5-y vanished - better interface
( reduction of localised states )
SRF’2003 ( 11 th Workshop )
RF
power
10
20
Eacc (MV/m)
30
( J. Halbritter - SRF ’01 – Tsukuba )
( IEEE Trans. on Appl. Supercond. 11, 2001 )
Q-Slope at High Gradients
Bernard Visentin
19
Comments ( I.T.E. )
 Explanations :
 Q-slope improvement after baking ( Nb2O5  )
 better slope for EP after baking ( smooth surface - lower * )
 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 mm - higher * )
SRF’2003 ( 11 th Workshop )
Q-Slope at High Gradients
Bernard Visentin
20
Thermal Feedback
( V. Kurakin - EPAC’94 - London )
Temperature Dependence of Surface Resistance
HS

T  Rtherm Pdiss  RS H S2 / 2
RS T0 
RS T  
2
( 1  C.Eacc
)
fit parameter :
baking effect :

( E. Haebel - TTF Meeting - 1998 )

RS (T )  RS (T0 ) 
 Q0  G RS  a  b.E
2
acc

RS
T
T
RBCS  AL , F ,  
2
T
e kT
 C  1.1015 V / m2


8 RS
 C  2.10
T

RS
A  
T
2
1  4.109   eNb
1  RS
 

C  

2
m    Nb hK  T
0

 2.109
SRF’2003 ( 11 th Workshop )
( B.V. et al. SRF’99 - Santa Fe )
Q-Slope at High Gradients
Bernard Visentin
21
Energy Gap Dependence
Exponential variation
RS  G Q0  Rres  A(L , F , )
2
T
e
only rigorous and experimentally proved
  kT
for thin films
magnetic field dependence of  ?

H   0 1  H 2 HC2

( normal state transition 2nd order if d/ < 51/2 )
for T/TC < 0.36
( A. Didenko - EPAC ’ 96 - Sitges )
( V. Mathur et al. - Phys. Rev. Let. 9, 374 - 1962 )
BC = 180 mT
BC = 195 mT
BC “fit factor”
for bulk material ( d >> )
Rres, A, (0) from RS(1/T) at low field
(H) : few % variation
( B.V. et al. - EPAC ’ 98 - Stockholm )
SRF’2003 ( 11 th Workshop )
Q-Slope at High Gradients
Bernard Visentin
22
Granular Superconductivity
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 ~ 10 mm ) :
exception :
segregation of impurities located at grain boundaries
Difficulties to apprehend the baking as a way to clean G.B.
( low temperature - diffusion O )
Experiment on Grain Boundaries Specific Resistance
SRF’2003 ( 11 th Workshop )
Q-Slope at High Gradients
( H. Safa et al. – SRF ’99 – Santa Fe )
Bernard Visentin
23
Similarities EP / BCP
Q-Slope
Fit
Magnetic
Field
Enhancement
Y
Interface
Tunnel
Exchange
Y
(E )
Thermal
Feedback
Y
Magnetic
Field
Dependence
of 
Segregation
of Impurities
8
Slope
Slope
before baking Improvement
( EP  BCP ) after baking
N
N
Y
Y
( parab. )
Y
N
-
Y
( RBCS Rres )
Y
( HC  )
( HC  )
N
N
(  segreg. )
SRF’2003 ( 11 th Workshop )
( only O )
N
( m < ; HC > )
N
( HC  )
Y
N
N
( m < ; HC > )
( Nb2O5-y  )
BCP Quench
unchanged
after baking
-
( HC  )
(   )
No change Exceptional
Quench
after 2 m.
Results
( EP > BCP )
air exposure
( BCP )
Y
( m et HC  )
Y
( expon. )
Y
Slope
after baking
( EP < BCP )
( high m )
Y
Validity
( low  )
( Nb2O5-y  )
( high  )
-
-
Y
N
-
N
-
-
N
Y
( HC > )
-
N
-
-
( thin film )
-
-
Y
-
-
Y
Q-Slope at High Gradients
( cleaning )
( coeff. C )
N
Bernard Visentin
24
Experimental Program at J.Lab.
“ H enhancement at grain bound. ”  “ Interface Tunnel Exchange ”
• Single cell cavity ( BCP - EP - w/o Baking ) excited in modes TM010 or TM011 : HS
• Two cell cavity TM010 ( 0-p mode ) : scan the surface ( E, H )
• Q0 ( Bpeak ) - ( BCP - EP - w/o Baking )
• Preliminary results :
( G. Ciovati et al. - PAC ’ 2003 - Portland )
SRF’2003 ( 11 th Workshop )
Q-Slope at High Gradients
Bernard Visentin
25
Conclusion
Experiments and Models have to progress in the future
to understand the phenomenon and to cure it
all the more so since
Q-slope is not totally removed by baking ( even for EP cavities )
9
9,0
R/R0
R/R0
8
7
D1-22
C1-03
C1-15
C1-16
C1-10
7,0
6
6,0
D1-22
C1-03
C1-15
C1-16
C1-10
5
High-Field Slopes after
baking
( BCP and EP cavities )
8,0
High-Field Slopes
before baking
( BCP and EP cavities )
( EP - Saclay A1 )
( EP - KEK 9 )
( BCP - Saclay I1 )
( BCP - Saclay P1 )
( BCP - Saclay N1 )
( EP - Saclay A2 )
( EP - KEK 10 )
( BCP - Saclay I2 )
( BCP - Saclay P2 )
( BCP - Saclay N2 )
5,0
4
4,0
3
3,0
2
2,0
2
E2acc
1
( MV/m )2
E acc
( MV/m )
1,0
0,0
0
0
500
1000
1500
2000
0
500
1000
1500
2000
if quench improvement possible ( > 40 MV/m )  Q-slope appearance
SRF’2003 ( 11 th Workshop )
Q-Slope at High Gradients
Bernard Visentin
26
Papers 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 )
SRF’2003 ( 11 th Workshop )
Q-Slope at High Gradients
Bernard Visentin
27
70
R/R0
D1-22
C1-03
C1-15
C1-16
C1-10
60
50
( EP - Saclay A1 )
( EP - KEK 9 )
( BCP - Saclay I1 )
( BCP - Saclay P1 )
( BCP - Saclay N1 )
40
High-Field Slopes before
baking
( BCP and EP cavities )
30
20
10
E2acc ( MV/m )2
0
0
9
200
400
600
800
1000
1200
1400
1600
1800
9
R/R0
D1-22
C1-03
C1-15
C1-16
C1-10
8
7
6
( EP - Saclay A1 )
( EP - KEK 9 )
( BCP - Saclay I1 )
( BCP - Saclay P1 )
( BCP - Saclay N1 )
R/R0
8
7
High-Field Slopes
after baking
( BCP and EP cavities )
6
5
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
5
High-Field Slopes before
baking
( BCP and EP cavities )
4
3
4
3
2
2
1
E2acc ( MV/m )2
0
0
200
400
600
800
1000
1200
1400
1600
1800
1
E2acc ( MV/m )2
0
0
SRF’2003 ( 11 th Workshop )
200
Q-Slope at High Gradients
400
600
800
1000
1200
1400
1600
1800
Bernard Visentin
28
H2-slope ( Intermediate Fields )
1E+12
Q-slopes after baking
( BCP and EP cavities )
Q0

RH  R0 1   * H 2 HC2
1E+11
1E+10
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 )

9,0
R/R0
Quench
1E+09
8,0
0
10
20
30
40
Eacc (MV/m)
High-Field Slopes
after baking
( BCP and EP cavities )
7,0
6,0
5,0
R
*
2
2


H
H
C
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
4,0
3,0
2,0
 *  3.3
H C  2000Oe
E2acc
1,0
( MV/m )2
0,0
0
SRF’2003 ( 11 th Workshop )
200
400
Q-Slope at High Gradients
600
800
1000
1200
1400
1600
1800
Bernard Visentin
29
Surface Treatment by Plasma
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 
1,E+11
Q0
O2 : 5.10-3 mbar
C1-17 O/P BCP Cavity
1,E+10
Standard BCP
After O plasma
1,E+09
0
5
10
15
20
25
30
f = 2.45 GHz
B = 875 G
PRF : 1500 W
Eacc (MV/m )
( B. Visentin et al. – this workshop )
SRF’2003 ( 11 th Workshop )
time : 1/2 hour
Tsurface < 80°C
Q-Slope at High Gradients
Bernard Visentin
30
Quench position on BCP cavities
6000
5600
5200
4800
4400
4000
3600
3200 T
2800 (mK)
2400
2000
1600
1200
800
400
0
upper
0
iris
Thermal sensor ( 1:1cm )
1
2
30
40
51
61
72
82
92
15
17
100
13
Thermal Sensor
11
9
7
5
3
1
C1-17 ( S1 )
Quench Position
3
4
C1-10
C1-15
5
6
C1-17
7
8
equator - EB weld ( 5 mm )
9
10
11
12
13
14
15
16
17
Position
( degree )
18
lower
iris
0
90
Position
180
( degree )
270
360
5600
9
EB
weld
10
C1-17 ( Q1 )
181
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
11
5200
4800
4400
4000
3600
3200
T (mK) 2800
2400
2000
1600
1200
800
400
0
Thermal Sensor
SRF’2003 ( 11 th Workshop )
Q-Slope at High Gradients
199
215
231
Position
(degree )
Bernard Visentin
31
Frequency Dependence of Q-slope
1E+11
no electrons
no X-rays
Q0
1E+10
quench
A1-02 ( 700 MHz )
C1-16 ( 1300 MHz )
L1-05 ( 1500 MHz )
RF
power
RF
power
1E+09
1E+11
0
10
20
Eacc (MV/m)
30
no electrons
no X-rays
Q0
1E+10
A1-02 ( 700 MHz )
C1-16 ( 1300 MHz )
RF
power
1E+09
0
20
40
60
80
100
120
140
Bp (mT)
SRF’2003 ( 11 th Workshop )
Q-Slope at High Gradients
Bernard Visentin