Cavity Optimization for Compact Accelerator-based
Free-electron MaserDan Verigin
TPUIn collaboration with
A. Aryshev, S. Araki, M. Fukuda, N. Terunuma, J. UrakawaKEK: High Energy Accelerator Research Organization
P. KarataevJohn Adams Institute at Royal Holloway, University of London
G. Naumenko, A. Potylitsyn, L. SukhikhTomsk Polytechnic University
K. SakaueWaseda University
Compact Accelerator-based Free-Electron Maser
A.P. Potylitsyn, Phys. Rev. E 60 (1999) 2272.
LUCX, compact linear accelerator
Energy 30 MeV ( = 62)
Intensity 1 nC/bunch
Num. of Bunches 100
Bunch spacing 2.8 ns
Bunch length <10 ps
Repetition rate, nominal 3.13 Hz
Emittance (round) 5 π mm•mrad
σx σy in SCDR chamber 200 μm, 200 μm
S. Liu, M. Fukuda, S. Araki, N. Terunuma, J.Urakawa, K. Hirano, N. Sasao, Nuclear Instruments and Methods A 584 (2008) 1-8.
Diffraction Radiation
Diffraction radiation (DR) appears when a charged particle moves in the vicinity of a medium
IDR ~ Ne
-20 -10 0 10 200.0
0.2
0.4
0.6
0.8
1.0
Nor
mal
ized
mic
row
ave
pow
er,a
rb.u
nits
M irrror orien tatio n angle, deg
Coherent Diffraction Radiation
CDR is generated by sequence of charged bunches
ICDR ~ Ne2
CDR on LUCX
2 6-way crosses2 4D vacuum
manipulation systems
2 aluminum mirrors
CDR on LUCX: Cavity length scan
405 410 415 420 425 430 4350.02
0.03
0.04
0.05
0.06
0.07
0.08
Nor
mal
ized
mic
row
ave
pow
er, a
rb. u
nits
Distance between mirrors, mm
openedclosed
Transmission calculation
i
2
2 21 p
2
2 2
p
2 2
2 211
p
2
2 21p
2
*0
ep
N em
M.I. Markovic, A.D. Rakic. Determination of optical properties of aluminium including electron reradiation in the Lorentz-Drude model. Opt.and Laser Tech., v. 22, No. 6, 394-398, 1990.R.T. Kinasewitz, B.Senitzky. Investigation of complex permittivity of n-type silicon at millimeter wavelengths. J. Appl. Phys., v. 54, No. 6, 3394-3398, 1983.
2 2 Re( )n k 2 Im( )nk
22
2
1cos 1 sin
1cos 1 sin
i i
s
i i
nn
R
nn
1s sT R 2
0 2 2(1 2 cos )ATT
A R AR
AlSi
Mirror test bench
Material Transmission coefficientExperiment Theory
Aluminized mirror 0 0Doped silicon 0.42 0.42Normal silicon 0.45 0.42
5mm
ope
ning
0 1 0 20 3 0 4 0 5 0 6 0 7 0 8 0 9 0
0
2 0
4 0
6 0
8 0
1 0 01 0 0 m m , f la t m ir ro r 5 0 m m , S ig m a -K o k i
P M H -5 0C 0 5 -10 -6 /1 8 m ir ro rS il ic o n p la te s
Tran
smis
sion
, %
M ir ro r p o si tio n , m m
p u re S iD o p e d S i
1 5 m m h o le in A l la y e r
New mirror design
Aluminum, nm
Silicon, mkm
Transmission coefficient, %
2 100 6.5150 5.3300 4.0
3 100 3.4150 2.7300 2.1
4 50 2.7100 2.0150 1.6
1 2 3 4 5 6 7 8mm0.0
0 .2
0 .4
0 .6
0 .8
1 .0Tos
h 100 m kmSi
1 2 3 4 5 6 7 8, mm
0.0 2
0 .0 4
0 .0 6
0 .0 8
0 .1 0
0 .1 2
0 .1 4
Tosh 2 n m
Al
Mirrror diameter = 100 mmThickness of Si substrate should be more than 100 mkm for durability
Stimulation
ESCDR = a ECav – addition to electric field by stimulation (depends on electric field stored in cavity)
EDR – electric field generated by single bunch d – loss in resonator Etot,2 = d EDR + EDR + ad EDR = EDR (1 + d (1+a)) = EDR (1+b) – electric field
in resonator after second bunch Etot,i = EDR (1-bi)/(1-b) – electric field in resonator after i-th bunch
0 5 10 15 20 25
0
10
20
30
40
50
60
70
SB
D s
igna
l tai
l int
egra
l, ar
b. u
nits
Number of bunches
Equation y = A1*exp(x/t1) + y0
Adj. R-Squar 0.9202Value Standard Err
C y0 0 0C A1 1.9685 0.16468C t1 6.9106 0.20078
0 5 10 15 20 25
0
200
400
600
800
Inte
nsity
, arb
.uni
ts
number of bunches
Model ExpGro1
Equationy = A1*exp(x/t1) + y0
Reduced Chi-Sqr
70,85437
Adj. R-Squa 0,99887Value Standard Er
B
y0 -108,382 9,35563A1 82,11966 5,68071t1 9,49871 0,24892
Chitrlada Settakorn, Michael Hernandez, and Helmut WiedemannStanford Linear Accelerator Center, Stanford University, Stanford, CA 94309, SLAC-PUB-7587 August 1997
0 5 10 15 20 2540
60
80
100
120
140
160
180
200
220
Inte
nsity
, arb
.uni
ts
number of bunches
Model ExpDec1
Equationy = A1*exp(-x/t1) + y0
Reduced Chi-Sqr
4,97298E-28
Adj. R-Square 1Value Standard Error
Intensity, arb.units
y0 -5,58956E-14 6,70031E-14A1 217,47945 5,62185E-14t1 16,4154 9,8284E-15
Cavity decay
Etot,i = EDR (1-bN)/(1-b) di-N – where N is number of bunches in train (i>N)
-20.
0n 0.0
20.0
n
40.0
n
60.0
n
80.0
n
100.
0n
120.
0n
0.00
0.02
0.04
0.06
0.08
0.10
Equation y=y0+A*exp(-x*t)
Adj. R-Square 0.9778Value Standard Error
peakY y0 -8.64E-4 1.28E-4peakY A 0.09063 0.0029peakY t 2.95327E7 1.14E6
SBD signal On resonance SBD signal Off resonance Cavity free run Peaks Exponential decay fit
SB
D s
igna
l, V
Time, s
A. Aryshev, et. al., IPAC’10, June 2008, Kyoto, Japan, MOPEA053
Thank you for attention