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 tation an gle, 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

No

rma

lize

d m

icro

wa

ve p

ow

er,

arb

. un

its

Distance between mirrors, mm

openedclosed

Transmission calculation

i

2

2 21 p

2

2 2

p

2 2

2 21

1p

2

2 21

p

2

*0

ep

N e

m

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

Al

Si

Mirror test bench

MaterialTransmission coefficient

Experiment TheoryAluminized mirror 0 0Doped silicon 0.42 0.42Normal silicon 0.45 0.42

5mm

ope

ning

0 1 0 2 0 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 ilic o n p la te s

Tra

nsm

issi

on, %

M ir ro r p o s itio 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 mkmSi

1 2 3 4 5 6 7 8, mm

0 .02

0 .04

0 .06

0 .08

0 .10

0 .12

0 .14

Tos

h 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

ign

al t

ail

inte

gra

l, a

rb. u

nits

Number of bunches

Equation y = A1*exp(x/t1) + y0

Adj. R-Squar 0.9202

Value Standard Err

C y0 0 0

C A1 1.9685 0.16468

C t1 6.9106 0.20078

0 5 10 15 20 25

0

200

400

600

800

Inte

nsi

ty, a

rb.u

nits

number of bunches

Model ExpGro1

Equationy = A1*exp(x/t1) + y0

Reduced Chi-Sqr

70,85437

Adj. R-Squa 0,99887

Value Standard Er

B

y0 -108,382 9,35563

A1 82,11966 5,68071

t1 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

nsi

ty, a

rb.u

nits

number of bunches

Model ExpDec1

Equationy = A1*exp(-x/t1) + y0

Reduced Chi-Sqr

4,97298E-28

Adj. R-Square 1

Value Standard Error

Intensity, arb.units

y0 -5,58956E-14 6,70031E-14

A1 217,47945 5,62185E-14

t1 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)

-20.0

n

0.0

20.0

n

40.0

n

60.0

n

80.0

n

100.0

n

120.0

n

0.00

0.02

0.04

0.06

0.08

0.10

Equation y=y0+A*exp(-x*t)

Adj. R-Square 0.9778

Value Standard Error

peakY y0 -8.64E-4 1.28E-4

peakY A 0.09063 0.0029

peakY t 2.95327E7 1.14E6

SBD signal On resonance SBD signal Off resonance Cavity free run Peaks Exponential decay fit

SB

D s

ign

al,

V

Time, s

A. Aryshev, et. al., IPAC’10, June 2008, Kyoto, Japan, MOPEA053

Thank you for attention