Investigation of optimized e.m. fields in SRF cavities for the ILC

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Oct 18, 2013 (3 years and 7 months ago)

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CI Seminar
27
June
2011
NAWIN JUNTONG
Slide No.
1
of
17
http://www.hep.manchester.ac.uk/u/nawin
Investigation of optimized
e.m
. fields in SRF cavities
for the ILC
CI Seminar
27
June
2011
NAWIN JUNTONG
Slide No.
2
of
17
http://www.hep.manchester.ac.uk/u/nawin
Motivation
Nicholas Walker: PAC
2009
-
Accelerator section dominates ILC project cost.
-
High gradient cavity can help reduce cost.
Chris
Adolphsen
: Linear
Collider School
2006
Cost dominated by the
tunnel cost
Cost dominated by the
cooling cost
TESLA qualified
gradient
ILC qualified
gradient
63
% of project cost is on accelerator sections.
CI Seminar
27
June
2011
NAWIN JUNTONG
Slide No.
3
of
17
http://www.hep.manchester.ac.uk/u/nawin
-
First
, we need higher gradient cavity for reducing the cost of ILC project, which depends
mainly on the main
linac
section
.
-
Second
, the present high gradient cavities, LL, Ichiro and Re
-
entrant, are designed based
on minimizing the surface magnetic field which limits the cavity gradient by the quench
.
-
Third
, the electron field emission will become problem when we operate at a higher
gradient
.
-
The
NLSF
, New Low Surface Field, cavity is the new design shape which has both surface
e.m
. fields optimized whilst maximizing the fundamental mode bandwidth.
Why we need new design?
CI Seminar
27
June
2011
NAWIN JUNTONG
Slide No.
4
of
17
http://www.hep.manchester.ac.uk/u/nawin
Why fundamental mode bandwidth important?
CI Seminar
27
June
2011
NAWIN JUNTONG
Slide No.
5
of
17
http://www.hep.manchester.ac.uk/u/nawin
TDR
LL
NLSF
Where is the peak fields?
-
Peak electric field is located near the iris while the peak
magnetic field is located near the equator.
CI Seminar
27
June
2011
NAWIN JUNTONG
Slide No.
6
of
17
http://www.hep.manchester.ac.uk/u/nawin
Influence of cell geometries
-
Small aperture gives higher accelerating
field
R
i
=
35
mm
R
i
=
25
mm
CI Seminar
27
June
2011
NAWIN JUNTONG
Slide No.
7
of
17
http://www.hep.manchester.ac.uk/u/nawin
Influence of cell geometries
-
Small aperture gives lower surface
e.m
.
fields and also gives weaker
k
c
-
Small aperture gives
rise in geometric short
-
range
wakefields
.
CI Seminar
27
June
2011
NAWIN JUNTONG
Slide No.
8
of
17
http://www.hep.manchester.ac.uk/u/nawin
Influence of cell geometries
-
Large ellipse shape gives lower E field
CI Seminar
27
June
2011
NAWIN JUNTONG
Slide No.
9
of
17
http://www.hep.manchester.ac.uk/u/nawin
Influence of cell geometries
-
Large surface area gives lower B field
CI Seminar
27
June
2011
NAWIN JUNTONG
Slide No.
10
of
17
http://www.hep.manchester.ac.uk/u/nawin
Red
-
Bs/Ea
,
Blue
-
Es/Ea
, Black
-
k
c
NLSF shape
-
The parameter regions for the iris of
32
mm is shown.
Optimisation parameters regions
CI Seminar
27
June
2011
NAWIN JUNTONG
Slide No.
11
of
17
http://www.hep.manchester.ac.uk/u/nawin
TESLA
LL
NLSF
TESLA
LL
NLSF
TESLA
LL, ICHIRO
LSF
NLSF
-
This graphical comparison of NLSF cavity surface
e.m
. fields
with TESLA and LL shapes
.
Parameter
Unit
TESLA
LL
ICHIRO
NLSF
f
s
(f
π
)
GHz
1
.
30116
1
.
30008
1
.
30040
1
.
30023
Bandwidth
MHz
24
.
32
19
.
74
19
.
82
20
.
50
k
c
%
1
.
89
1
.
53
1
.
54
1
.
59
E
s
/E
a
-
2
.
18
2
.
42
2
.
37
2
.
11
B
s
/E
a
mT/(MV/m)
4
.
18
3
.
64
3
.
62
3
.
83
Single cell properties
CI Seminar
27
June
2011
NAWIN JUNTONG
Slide No.
12
of
17
http://www.hep.manchester.ac.uk/u/nawin
-
The end cells have been designed to maintain a good field flatness along the cavity
axis for accelerating mode.
-
The end cells shape is similar to the mid cell shape except the equator and the iris
elliptical parameters.
End cell
1
End cell
2
Mid cell
End cell design
CI Seminar
27
June
2011
NAWIN JUNTONG
Slide No.
13
of
17
http://www.hep.manchester.ac.uk/u/nawin
-
The surface
e.m
. fields is obtained from HFSS
simulation
on the half structure, taking
the benefit of symmetrical geometry.
-
The maximum surface
e.m
. fields is located at the regular cell not on the end cell.
This means that the end cell shapes don’t limit the performance of the
9
-
cell cavity.
9
-
cell surface
e.m
. fields
CI Seminar
27
June
2011
NAWIN JUNTONG
Slide No.
14
of
17
http://www.hep.manchester.ac.uk/u/nawin
Multi
-
pole mode distribution in NLSF cavity
-
Multi
-
pole mode
distribution in the
9
-
cell
NLSF cavity
has been investigated using
HFSS
on a complete tuned up cavity.
-
The largest R/Q is located at a

/
9
phase
advance per cell in the third dipole band.
CI Seminar
27
June
2011
NAWIN JUNTONG
Slide No.
15
of
17
http://www.hep.manchester.ac.uk/u/nawin
RF power coupler design
-
RF power input coupler has been designed, exploring the possibility of various designs.
-
TTF
-
III type coupler can be
utilised
with NLSF cavity.
Dista
nce
Std.
TTF
Disc
Curve
1
Curve
2
CI Seminar
27
June
2011
NAWIN JUNTONG
Slide No.
16
of
17
http://www.hep.manchester.ac.uk/u/nawin
HOM coupler design
old
red
-
MWS
,
blue
-
HFSS
new
HFSS results
CI Seminar
27
June
2011
NAWIN JUNTONG
Slide No.
17
of
17
http://www.hep.manchester.ac.uk/u/nawin
Closing remarks
-
A complete nine
-
cell design of my NLSF cavity is presented.
-
It has potential to achieve accelerating gradient of
47
MV/m (B
s
=
180
mT and E
s
=
99
MV/m).
-
It has
9
% larger R/Q compared to TESLA cavity.
-
The manufacturing of this cavity is realistic as it is similar to the TESLA cavity.
-
TTF
-
III type power coupler can be
utilised
with NLSF cavity to satisfy ILC requirement.
-
The TESLA HOM couplers are also
utilised
with this cavity with a
90
deg. configuration.
-
NLSF cavity can be used in various SRF L
-
band accelerators.
Thank
you