Multipactor Studies
Sergey Antipov1,2, C. Jing1,2, P. Schoessow1,
A. Kanareykin1, Bin Feng2,3, John Power2, Wei Gai2
1Euclid
Techlabs LLC
2Argonne Wakefield Accelerator Facility
3Illinois Institute of Technology
US High Gradient Research Collaboration Workshop 2011
2/9/2011
Multipactor
Normalized rf Power
Transmission (%)
Externally driven AWA structures tests at NRL
100
90
80
70
60
50
40
30
20
10
0
Non-coated Alumina DLA
TiN-coated Alumina DLA
MCT-20 DLA
Quartz tube_big ID
Quartz tube_small ID
0.1
1
Initial Accelerating Gradient (MV/m)
10
Outline

Multipactor suppression in HG
structures (simulations)

Grooved structures for
multipactor studies
2D simulation

University of Maryland
model: non-stationary
two-dimensional
simulation where DC field
is taken into account selfconsistently
O. V. Sinitsyn, G. S. Nusinovich
and T. M. Antonsen., Phys.
Plasmas, 16, 073102 (2009)

Benchmarked with ANL –
NRL dielectric loaded
accelerating structure
measurements
AAC 2010 O.V. Sinitsyn, G. S. Nusinovich
and T. M. Antonsen, Jr.
2D model implementation
PDF of energy distribution
0.2
0.15
0.1
0.05
0
0
5
10
15
Energy, eV
20
25
SEE energy distribution
+ θ - distribution
g  e  
1
sin  e 
2
C. Vicente, et al. MULCOPIM 2005
Modified Vaughan model
3
x 10
5
2
Ez=3MV/m, SEY=2.9
1
0
0
MP-induced power loss, %
number of particles
Multipactor. Power loss vs gradient
1
2
3
time, ns
4
5
6
Electron cloud at
different times
25
20
MAX SEY 2.4
MAX SEY 5
Multipactor power
loss decreases at HG
15
10
5
0
0
50
gradient, MV/m
100
150
Simplified representation
Ez = 10 MV/m
4
yield
3
2
1
0
0
2000
4000
6000
Energy, eV
8000
10000
We emit particles at different phases and monitor their
incidence energy and corresponding yield
High gradient case
Ez = 150 MV/m
4
yield
3
2
1
0
0
2000
4000
6000
Energy, eV
8000
10000
We are developing a Monte-Carlo simulation based on this idea
similar to L. Wu, L.K. Ang Physics of Plasmas 14, 013105 (2007)
Progress on grooved structure
development for multipactor studies
Grooved structure example:
Changing the surface profile
by periodically grooving has been
found to obviously increase the
transmitted power in S-band HPM
window breakdown experiment
C. Chang et al. J. Appl. Phys. 105, 123305 (2009)
Grooved structure design
number of particles
8
x 10
6
5
 grooves
no grooves
Ez = 6 MV/m
4
2
0
0
0.5
1
1.5
time, ns
2
2.5
* CST
Limited by machining capabilities
Quartz grooved tubes for MP studies
Longitudinal
Transverse
we are set to test
~ 10 different
configurations:
•
•
•
•
groove type
groove dimension
structure length
TiN coating
Matching sections are
designed and being
manufactured
summary


Multipactor simulation approach is being
developed for high gradient regimes
(100+ MV/m). It suggests a reduction
in MP power loss.
We designed and manufactured several
grooved structures and they are being
prepared for the high power tests