The development of new techniques for SRF cavity surface research at Fermilab Mingqi Ge Technical Division Fermi National Accelerator laboratory Sept 21, 2010 1
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Th
e d
eve
lop
me
nt o
f n
ew
te
ch
niq
ue
s
for
SR
F c
avity s
urf
ace
re
se
arc
h a
t
Fe
rmila
b
Mingqi Ge
Technical Division
Fermi National Accelerator laboratory
Sept 21, 2010
1
Outlin
e
�C
avity o
ptica
l in
sp
ectio
n
�S
urf
ace
re
plic
a t
ech
niq
ue
�L
ase
r re
-me
ltin
g t
ech
niq
ue
�L
ase
r w
eld
ing
stu
dy
La
se
r w
eld
ing
stu
dy
2
Cavity R
F p
erf
orm
ance s
tatistic
Image c
ourt
esy o
f C
am
ille G
insburg
1stpass y
ield
2n
dpass y
ield
�E
ven a
fter
2n
dpass,
less t
han 5
0%
cavitie
s y
ield
at
35M
V/m
.
�S
urf
ace s
tate
affects
SR
F c
avity s
uperc
onductivity d
ram
atically
.
�S
urf
ace r
esearc
h is a
n im
port
ant
assig
nm
ent
for
SR
F m
ate
rial gro
up in F
NA
L.
3
Op
tica
l in
sp
ectio
n te
ch
niq
ue
at F
erm
ilab
Kyoto system:
�1
.3G
Hz 9
-ce
ll ca
vity
�1
.3G
Hz s
ing
le-c
ell
ca
vity
Questarsystem:
�1
.3G
Hz 9
-ce
ll d
resse
d c
avity
�1
.3G
Hz s
ing
le-c
ell
ca
vity
�3
.9G
Hz 9
-ce
ll ca
vity
�3
.9G
Hz s
ing
le-c
ell
ca
vity
�1
.3G
Hz T
rave
ling
wa
ve
ca
vity
�S
po
ke
ca
vity
�6
50
MH
z S
RF
ca
vity
Kyo
to o
pti
cal
insp
ect
ion
syst
em
Qu
est
ar
insp
ect
ion
syst
em
Ky
oto
sy
ste
m
10
0%
cro
pp
ed
im
ag
e f
rom
ce
nte
r
Re
solu
tio
n c
om
pa
riso
n b
etw
ee
n K
yo
to a
nd
Qu
est
ar
syst
em
Qu
est
ar
syst
em
Resolution
(lp/mm)
Questa
r181
Kyoto
32
5
De
fects
ob
se
rve
d in
eq
ua
tor
reg
ion
TE
1C
AT
002
Pit in T
E1C
AT
002
TB
9A
CC
017
TB
9jl0
02
1 m
m
Oxid
e la
ye
r in
TB
9A
CC
01
7
TE
1A
ES
004
TE
1A
CC
004
TE
1A
CC
003 6
Gro
wth
of p
it o
bse
rve
d b
y o
ptica
l in
sp
ectio
n
De
fects
ob
se
rve
d in
iri
s r
eg
ion
Image c
ourt
esy o
f D
mitri S
erg
ats
kov
TB
9R
I026
TB
9jl0
02
TB
9jl0
02
1 m
m
Gro
wth
of p
it o
bse
rve
d b
y o
ptica
l in
sp
ectio
n
Bra
nd n
ew
cavity
Aft
er
70µ
m E
PA
fter
anoth
er
70µ
m
EP
(to
tal 140µ
m E
P )
TB
9R
I026
So
me
pits c
an
no
t b
e
rem
ove
d b
y b
ulk
EP
!
10
0µ
m
7
Surf
ace r
eplic
a techniq
ue a
t F
erm
ilab
Motivation
�T
o r
eveal th
e 3
-D p
rofile
of pits.
�T
o p
rovid
e t
opolo
gy info
rmation t
o e
sta
blis
h t
he m
echanis
m
of lo
cal quench a
t th
e fla
ws.
�T
o a
ssess s
urf
ace p
repara
tion e
ffectiveness b
y e
xtr
acting
surf
ace r
oughness
Technic
al challe
ng
es
�R
esolu
tion (
to r
esolv
e f
eatu
res~
>100
µm
in d
iam
ete
r; >
10
µm
in d
epth
) .
�P
ouring s
ilicone in a
nd p
eelin
g it out fr
om
deep 9
-cell
cavity.
�N
o d
egra
dation f
or
RF
perf
orm
ance.
8
Technic
al appro
achin
g
Cup
Sil
ico
ne
Ba
llo
on
He
ad
Ra
il
Sta
ge
Cup
Mold
ing e
quato
r re
gio
n
Mold
ing iris r
egio
n
Technic
al appro
achin
g
Str
ing
Sili
co
ne
Fe
atu
res o
n s
ilico
ne
Epoxy a
fter
casting o
n s
ilicone
µm
012345678910
11
12
13
14
15
16
17
18
19
20
Featu
re’s
3D
shape a
fter
pro
filo
metr
y s
cannin
g
Resolu
tion:
1 m
icro
n !
A m
an-m
ade p
itP
it r
eplic
aµ
m 0
20
40
60
80
10
0
12
0
14
0
16
0
18
0
20
0
00
.05
0.1
0.1
50
.20
.25
0.3
0.3
50
.40
.45
0.5
0.5
50
.60
.65
0.7
0.7
5 m
m
Le
ng
th =
0.8
mm
P
t =
12
8 µ
m
Sca
le =
20
0 µ
mµ
m 0
20
40
60
80
10
0
12
0
14
0
16
0
18
0
20
0
00
.05
0.1
0.1
50
.20
.25
0.3
0.3
50
.40
.45
0.5
0.5
50
.60
.65
0.7
0.7
5 m
m
Le
ng
th =
0.8
mm
P
t =
12
8 µ
m
Sca
le =
20
0 µ
m
pro
file
of
a p
it o
n t
he N
b c
oupon
pro
file
of
pit’s
replic
a
125µ
m d
eep,
300µ
m in d
iam
ete
r11
TE1AES004 - Q vs E
Comparison before and after applying molding material
1.E
+1
0
1.E
+1
1
Q0
Be
fore
mo
ldin
g
Aft
er
mo
ldin
g
No d
egra
dation o
f cavity R
F p
erf
orm
ance
1.E
+0
8
1.E
+0
9
01
02
03
04
0
Eacc [M
V/m
]
Q0
No lig
ht
EP, ju
st
HP
R a
fter
mold
ing
12
µm
010
20
30
40
50
60
70
80
90
10
0
11
0
12
0
13
0
14
0
15
0
16
0
1.3
GH
z 9
-cell
cavity T
B9A
CC
017
EB
-We
ldin
g s
ea
m
Y-Y
’
X-X
’
Surf
ace d
efe
ct
limits c
avity p
erf
orm
ance a
t lo
w f
ield
µm 0
20
40
60
80
10
0
12
0
14
0
16
0
00
.05
0.1
0.1
50
.20
.25
0.3
0.3
50
.40
.45
0.5
0.5
50
.6 m
m
Le
ng
th =
0.6
23
mm
P
t =
14
8 µ
m
Sca
le =
16
0 µ
m
µm 0
20
40
60
80
10
0
12
0
14
0
16
0
00
.05
0.1
0.1
50
.20
.25
0.3
0.3
50
.40
.45
0.5
0.5
50
.6 m
m
Le
ng
th =
0.6
45
mm
P
t =
14
3 µ
m
Sca
le =
16
0 µ
m
X-X
’
Y-Y
’
TB
9A
CC
017
quenched
at12.3
MV
/m,
Pit
was
found
atC
ell
#4
equato
r180
deg
regio
n(q
uench
location),
the
pit
is150
µm
deep
and
200
µm
wid
eon
the
top.
13
µm
010
20
30
40
50
60
70
80
90
10
0
11
0
12
0
13
0
14
0
15
0
16
0
17
0
18
0
Sp
ot
(a)
Sp
ot
(b)
µm 140
160
Leng
th =
0.7
56 m
m P
t = 1
59 µ
m S
cale
= 1
70 µ
m
Surf
ace d
efe
ct
limits c
avity p
erf
orm
ance a
t lo
w f
ield
020406080100
120
140
00.
050.
10.
150.
20.
250.
30.
350.
40.
450.
50.
550.
60.
650.
70.
75 m
m
µm
020406080100
120
140
160
00.
10.
20.
30.
40.
50.
60.
70.
80.
91
mm
Leng
th =
1 m
m P
t = 1
55 µ
m S
cale
= 1
60 µ
m
AE
S001
quenched
at15.6
~21M
V/m
,
Tw
inpeaks
were
found
atC
ell
#3
equato
r169
deg
regio
n(q
uench
location).
Sp
ot A
h
eig
ht 1
60
µm
, d
iam
ete
r 7
00
µm
on
bo
tto
m
Sp
ot B
h
eig
ht 1
55
µm
, d
iam
ete
r 1
00
0µ
m o
n b
ott
om
14
Dia
mete
r: 4
00µ
m,D
epth
: 60µ
m
µm 0
10
20
30
40
50
60
70
00
.05
0.1
0.1
50
.20
.25
0.3
0.3
50
.40
.45
0.5
mm
Le
ng
th =
0.5
mm
P
t =
63
.9 µ
m
Sca
le =
70
µm
µm 0102030405060708090100
110
120
130
140
36M
V/m
quenched
at pit r
egio
nT
E1A
CC
00
3
Eq
ua
tor
we
ldin
g s
ea
m
HA
Z
Surf
ace d
efe
ct
limits c
avity p
erf
orm
ance a
t hig
h f
ield
Sin
gle
-cell
cavity T
E1A
CC
003 &
TE
1A
ES
004
µm 0
10
20
30
40
50
60
70
80
90
10
0
00
.10
.20
.30
.40
.50
.60
.70
.80
.91
1.1
1.2
1.3
1.4
mm
Le
ng
th =
1.4
9 m
m
Pt
= 8
1.9
µm
S
ca
le =
10
0 µ
m
Dia
mete
r: 1
300µ
m, D
epth
: 70µ
m
A 1
5µ
m h
igh tin
y b
um
p in the c
ente
r.
µm
010
20
30
40
50
60
70
80
90
10
0
11
0
12
0
13
0
14
0
15
0
16
0
17
0
18
0
19
0
20
0
21
0
22
0
23
0
24
0
25
0
26
0
27
0
28
0
29
0
30
0
39M
V/m
quenched
at pit r
egio
nT
E1A
ES
00
4
Eq
ua
tor
we
ldin
g
sea
m
15
µm 0
10
20
30
40
50
60
70
00
.10
.20
.30
.40
.50
.60
.70
.80
.91
mm
Le
ng
th =
1 m
m
Pt
= 6
6.5
µm
S
cale
= 7
0 µ
m
µm
0510
15
20
25
30
35
40
45
50
55
60
65
70
µm
80
90
10
0
11
0
12
0
13
0
14
0
15
0
16
0
17
0
18
0
19
0
20
0
µm 20
40
60
80
10
0
12
0
14
0
16
0
18
0
20
0
Le
ng
th =
0.8
76
mm
P
t =
19
6 µ
m
Sca
le =
21
0 µ
m
Re
ve
al p
its p
rofile
on
iri
s r
eg
ion
TB
9R
I026
Dia
mete
r: 4
00µ
m,D
epth
: 70µ
m
Sp
ot B
Sp
ot A
Spot A
010
20
30
40
50
60
70 µ
m
010
20
30
40
50
60
70
80
90
10
0
11
0
12
0
0
20
00
.05
0.1
0.1
50
.20
.25
0.3
0.3
50
.40
.45
0.5
0.5
50
.60
.65
0.7
0.7
50
.80
.85
mm
µm 0
20
40
60
80
10
0
12
0
00
.05
0.1
0.1
50
.20
.25
0.3
0.3
50
.40
.45
0.5
0.5
5 m
m
Le
ng
th =
0.5
81
mm
P
t =
11
6 µ
m
Sca
le =
12
0 µ
m
TB
9jl0
02
Spot A
: D
iam
ete
r: 8
00µ
m,D
epth
: 180µ
m
Spot B
: D
iam
ete
r: 5
50µ
m,D
epth
: 110µ
m
A 2
0µ
m d
eep c
revic
e in c
ente
r
Spot B
16
A-A
’ Join
t of gra
in
boundary
Join
t of gra
in
boundary
Weld
ing s
eam
The m
easure
ment
of
gra
in b
oundary
ste
p
A-A
’
B-B
’
Pro
file
on A
-A’
The im
age d
epic
ts t
he join
t of
gra
in b
oundary
.Eacc reached 43MV/m
The h
eig
ht
of
ste
p o
n A
-A’: 6
0µ
m
The h
eig
ht
of
ste
p o
n B
-B’: 2
5µ
m
Pro
file
on B
-B’
B-B
’
17
Ro
ug
hn
ess c
om
pa
riso
n b
etw
ee
n la
rge
gra
in B
CP
’d c
avity a
nd
fin
e g
rain
EP
’d a
nd
BC
P’d
ca
vity.
µm
012345678910
11
12
13
14
15
16
17
18
µm
0510
15
20
25
30
35
40
45
50
55
60
65
70
75
µm
012345678910
11
12
13
14
15
16
17
La
rge
gra
in B
CP
’d c
avity
Ere
ach
ed
43
MV
/m!
Fin
e g
rain
EP
’d c
avity
Ea
cc
rea
ch
ed
40
MV
/m!
Fin
e g
rain
BC
P’d
ca
vity
Ea
cc
rea
ch
ed
26
MV
/m!
Ea
cc
rea
ch
ed
43
MV
/m!
Ea
cc
rea
ch
ed
40
MV
/m!
Ea
cc
rea
ch
ed
26
MV
/m! 18
Larg
e g
rain
BC
P’d
cavity
Fin
e g
rain
EP
’d c
avity
Fin
e g
rain
BC
P’d
cavity
Ra (
µm
)0.0
516
0.0
53
0.2
57
Rz (
µm
)0.2
83
0.2
75
1.2
1
Rq (
µm
)0.0
648
0.0
665
0.3
33
Tra
ckin
g s
urf
ace r
oughness f
rom
each p
repara
tion s
tep
Aft
er
50
µm
tu
mb
ling
su
rfa
ce
Fin
e g
rain
EP
’d c
avity
Aft
er
fin
al tu
mb
ling
su
rfa
ce
µm
012345678910
11
12
13
14
15
16
µm
012345678910
11
12
13
14
15
16
17
µm
012345678910
11
12
13
19
Aft
er
50µ
m
tum
blin
g
Aft
er
final
tum
blin
g
Fin
e g
rain
EP
’d c
avity
Ra (
µm
)0.5
12
0.0
527
0.0
53
Rz (
µm
)2.6
80.2
53
0.2
75
Rq (
µm
)0.6
33
0.0
669
0.0
665
Ca
vity s
urf
ace
ro
ug
hn
ess
µm
012345678910
11
12
13
14
15
16
17
18
19
20
21
µm
012345678910
11
12
13
14
15
16
17
18
Brand new
TE1ACC006
Weld
ing
seam
HA
ZO
uts
ide H
AZ
µm
012345678910
11
12
13
14
15
16
17
18
19
Brand new
TE1PAV001
µm
0246810
12
14
16
18
20
22
24
26
28
30
32
34
36
38
µm
012345678910
11
12
13
µm
012345678910
11
12
13
PKU single crystal
µm
17
18
µm
13
14
µm
12
13
BCP'd 70
µm
NR-6
EP'd 40
µm
TE1ACC005
µm
0246810
12
14
16
18
20
22
24
26
28
30
32
34
36
38
40
42
44
µm
012345678910
11
12
13
14
15
16
17
18
19
20
21
22
µm
0510
15
20
25
30
35
40
45
50
55
60
65
70
75
µm
012345678910
11
12
13
14
15
16
17
µm
012345678910
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12
13
14
15
µm
012345678910
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12
13
14
15
16
PKU single crystal
BCP‘d cavity
012345678910
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12
13
14
15
16
17
012345678910
11
12
13
012345678910
11
20
Ca
vity s
urf
ace
ro
ug
hn
ess
Weld
ing
seam
HA
ZO
uts
ide H
AZ
EP'd 120
µm
TE1ACC003
EP'd 150
µm
TB9ACC017
µm
012345678910
µm
012345678910
11
12
13
µm
012345678910
11
12
13
14
µm
12345678910
µm
12345678910
11
12
13
14
15
16
µm
0.5
11.5
22.5
33.5
44.5
55.5
66.5
77.5
88.5
9
Tumbling
100-120
µm
TE1ACC004
001
00.5
µm
012345678910
11
12
13
14
15
16
µm
012345678910
11
12
13
µm
012345678910
11
12
13
PKU Large grain
BCP‘d cavity
µm
0246810
12
14
16
18
20
22
24
26
28
30
32
34
36
38
40
42
µm
012345678910
11
12
13
14
15
16
17
18
µm
0246810
12
14
16
18
20
22
24
26
28
30
32
34
36
21
Su
rfa
ce
ro
ug
hn
ess v
s. G
rad
ien
tT
ES
LA
shape ,
quenched b
ut
no
obvio
us d
efe
cts
22
Su
mm
ary
of su
rfa
ce
re
plic
a t
ech
niq
ue
�S
urf
ace r
eplic
a t
echniq
ue h
as h
igh r
esolu
tion (
the s
ubstr
uctu
re
insid
e p
its),
and n
o d
egra
dation o
f cavity R
F p
erf
orm
ance.
�R
eveale
d p
it’s
3-D
shape f
rom
9-c
ell
cavity e
quato
r and iri
s
regio
n.
�E
xtr
acte
d s
urf
ace r
oughness f
rom
six
majo
r cate
gories o
f S
RF
cavitie
s, re
pre
senting t
he m
odern
SR
F c
avity technolo
gie
s.
�T
opolo
gy info
rmation e
nable
s u
s t
o e
stim
ate
the f
ield
�
Topolo
gy info
rmation e
nable
s u
s t
o e
stim
ate
the f
ield
enhancem
ent
facto
r, a
nd t
o a
ssess t
he e
ffectiveness o
f
surf
ace p
repara
tion.
23
La
se
r re
-me
ltin
g te
ch
niq
ue
at
FN
AL
Motivation
�R
em
ove s
urf
ace d
efe
cts
lim
itin
g c
avity g
radie
nt
belo
w
20M
V/m
and im
pro
ve g
radie
nt
> 3
5M
V/m
.
Technic
al challe
ng
es
�Laser
spot
should
be v
ery
sm
ooth
and f
lat.
�F
ocus L
aser
beam
on p
it a
ccura
tely
. (P
it ~
100µ
m)
�F
ocus L
aser
beam
on p
it a
ccura
tely
. (P
it ~
100µ
m)
�H
igh r
esolu
tion c
am
era
and s
heet
lighting a
re n
eeded f
or
trackin
g p
it.
�M
olten r
egio
n s
hould
be p
rote
cte
d b
y p
ure
Ar
gas.
24
La
se
r re
-me
ltin
g s
yste
m fo
r sin
gle
-ce
ll ca
vity
Mir
ror
Lase
r b
ea
m
Ca
vit
y
Lase
r h
ea
d
No
zzle
25
CC
D c
am
era
Laser
beam
deliv
er
line
Monitor
Gas n
ozzle
hold
er
Ro
tatio
n s
tag
e
26
Laser
sourc
eA
r gas c
ylin
der
Laser
focus
pla
tform
X-Y
sta
ge
V-b
lock w
ith
rolle
rs
Ro
tatio
n s
tag
e
26
µm 05
10
15
20
25
30
35
40
45
50
00
.10
.20
.30
.40
.50
.60
.70
.80
.91
mm
Le
ng
th =
1 m
m
Pt
= 4
5.6
µm
S
ca
le =
50
µm
µm
0510
15
20
25
30
35
40
45
µm
15
0
20
0
25
0
Le
ng
th =
1.8
4 m
m
Pt
= 2
40
µm
S
ca
le =
25
0 µ
m
µm
12
0
14
0
16
0
18
0
20
0
22
0
24
0
Laser
para
mete
rs a
nd g
as
pre
ssure
optim
ize v
ia N
b c
oupon
0
50
10
0
00
.10
.20
.30
.40
.50
.60
.70
.80
.91
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
mm
µm 0
20
40
60
80
10
0
12
0
14
0
16
0
00
.10
.20
.30
.40
.50
.60
.70
.80
.91
1.1
1.2
mm
Le
ng
th =
1.2
1 m
m
Pt
= 1
59
µm
S
ca
le =
16
5 µ
m
020
40
60
80
10
0
12
0
µm
020
40
60
80
10
0
12
0
14
0
27
µm 0
20
40
60
80
10
0
12
0
14
0
00
.10
.20
.30
.40
.50
.60
.70
.80
.91
mm
Le
ng
th =
1 m
m
Pt
= 1
25
µm
S
ca
le =
14
0 µ
m
Man-m
ade p
it
µm
010
20
30
40
50
60
70
80
90
10
0
11
0
12
0
13
0
Pro
file
Co
mp
ariso
n b
efo
re a
nd
aft
er
lase
r re
-me
ltin
g
Aft
er
re-m
eltin
g t
he p
it p
rofile
changed f
rom
120µ
mdeep t
o 3
0µ
mflat
µm 0
20
40
60
80
10
0
12
0
14
0
00
.05
0.1
0.1
50
.20
.25
0.3
0.3
50
.40
.45
0.5
0.5
50
.60
.65
0.7
0.7
5 m
m
Le
ng
th =
0.8
mm
P
t =
29
.6 µ
m
Sca
le =
14
0 µ
m
µm
0510
15
20
25
30
28
La
se
r p
roce
ssin
g o
f 1
.3G
Hz s
ing
le-c
ell
ca
vity
TE
1A
CC
00
3
Scre
en
sh
ot o
f th
e m
on
ito
r b
efo
re a
nd
aft
er
lase
r re
-me
ltin
g
The P
it b
efo
re r
e-m
eltin
gA
fter
re-m
eltin
g
Images w
as t
aken f
rom
Kyoto
Optical In
spection m
achin
e29
µm
010
20
30
40
50
60
70
80
90
10
0
11
0
12
0
13
0
14
0
Pro
file
co
mp
ari
so
n b
efo
re a
nd
afte
r
La
se
r p
roce
ssin
g
Befo
re laser
re-m
eltin
g: 400µ
min
dia
mete
r, 6
0 µ
min
depth
The p
it p
rofile
changed f
rom
60µ
m d
eep t
o 3
0µ
m f
lat
aft
er
re-m
eltin
g a
nd 5
0µ
m lig
ht
EPA
fter
laser
re-m
eltin
g: 700µ
min
dia
mete
r,
30 µ
min
depth
30
Cavity vert
ical te
st re
sults
befo
re a
nd a
fter
laser
pro
cessin
g
1.E
+1
0
1.E
+11
Q0
1.3GHz single-cell cavity TE1ACC003
RF perform
ance comparison
Before and after laser re-melting
Aft
er
lase
r re
-m
eltin
g
Aft
er
La
se
r p
roce
ssin
g: E
P 5
0µ
m+
HP
R+
12
0C
ba
kin
g;
Ea
cc a
ch
ieve
d 4
0.3
MV
/m,
qu
en
ch
ed
at
mo
lte
n r
eg
ion
.31
1.E
+0
8
1.E
+0
9
01
02
03
04
0Eacc[MV/m]
Th
e n
ext ste
pTo
de
ve
lop
9-c
ell
syste
m.
Pit in 1
.3G
Hz 9
-cell
cavity T
B9A
CC
017
Quenched a
t 12.3
MV
/m.
32
Sum
mary
Laser
re-m
eltin
g techniq
ue
�C
hanged p
it’s
pro
file
to fla
t surf
ace b
y h
igh p
ow
er
lase
r
puls
e.
�S
uccessfu
lly r
e-m
elted a
pit insid
e 1
.3G
Hz s
ingle
-cell
cavity.
�Im
pro
ved c
avity g
radie
nt
to 4
0.3
MV
/m a
fter
50µ
m E
P.
�N
ext
ste
p is t
o d
evelo
p a
syste
m for
9-c
ell
cavity.
�N
ext
ste
p is t
o d
evelo
p a
syste
m for
9-c
ell
cavity.
33
La
se
r w
eld
ing
stu
dy
Motivation a
nd B
enefits
�D
ram
atically
decre
ase H
AZ
are
a.
1.T
he
la
se
r p
uls
e h
as v
ery
sh
ort
du
ratio
n ~
10
ms;
2.T
he
po
ten
tia
l b
en
efit is
to
de
cre
ase
th
e p
rob
ab
ility
of w
eld
ing
pit
ge
ne
ratio
n.
�T
he w
eld
could
be v
ery
sm
ooth
and n
arr
ow
.
1.P
rove
d b
y la
se
r re
-me
ltin
g te
ch
niq
ue
(4
0M
V/m
);1
.Pro
ve
d b
y la
se
r re
-me
ltin
g te
ch
niq
ue
(4
0M
V/m
);
2.B
y c
ha
ng
ing
diffe
ren
t p
uls
e fo
rm, w
e c
an
ch
an
ge
th
e r
atio
of w
eld
wid
th
an
d d
ep
th.
�W
eld
ing c
avity in A
ir just w
ith A
r gas p
rote
ction
Pro
ve
d b
y la
se
r re
-me
ltin
g te
ch
niq
ue
�W
eld
ing v
ery
com
plic
ate
d s
tructu
re.
La
se
r b
ea
m c
an
be
re
fle
cte
d a
nd
fo
cu
se
d b
y o
ptics a
s w
ell
as c
on
du
cte
d
by la
se
r fib
ers
with
ou
t so
mu
ch
po
we
r lo
ss.
34
Fro
nt sid
e
10cm
Back s
ide
35
RR
R te
st
resu
lts
13
45
Sa
mp
le N
o.
RR
R
13
26
33
48
42
86
52
34
, 2
52
Weld
ing s
eam
52
34
, 2
52
RR
R v
alu
e d
oes n
ot decre
ase s
o m
uch! 3
6
Co
nclu
sio
n
�S
evera
l new
techniq
ues h
ave b
een d
evelo
ped a
t F
erm
ilab
surr
oundin
g a
topic
: S
urf
ace.
�O
ptical In
spection locate
s t
he d
efe
cts
and lin
ks t
hem
to
quench location v
ia T
-mappin
g.
�S
urf
ace r
eplic
a t
echniq
ue e
xhib
its 3
-D s
hape o
f pit, and
extr
acts
surf
ace r
oughness f
rom
SR
F c
avity.
�H
igh p
ow
er
laser
puls
e is a
ble
to r
e-m
elt p
it a
nd r
esto
re
cavity g
radie
nt
up t
o 4
0M
V/m
.
�Laser
weld
ing h
as p
ote
ntial to
avoid
weld
ing p
its g
enera
tion.
37
Thanks for
your
att
ention
Thanks for
your
att
ention
38
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