development of s-band rf gun and advanced diagnostics in pal
DESCRIPTION
Development of S-band RF gun and advanced diagnostics in PAL. 박용운 (Yong Woon Park, Ph.D.) 포항 가속기 연구소 (Pohang Accelerator Laboratory, PAL) 포항공과대학교 물리학과 (Physics department) (Pohang University of Science and Technology, POSTECH). Contents. Facilities in PAL - PowerPoint PPT PresentationTRANSCRIPT
POSTECHPAL
Development of S-band RF gun and
advanced diagnostics in PAL박용운
(Yong Woon Park, Ph.D.)
포항 가속기 연구소 (Pohang Accelerator Laboratory, PAL)
포항공과대학교 물리학과(Physics department)
(Pohang University of Science and Technology, POSTECH)
March 16, 2010 SLAC National Accelerator Laboratory
POSTECHPAL
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Contents
1. Facilities in PAL
2. S-band RF gun development in PAL
3. A study of electron beam measurement by using electro-optic crystal
4. Transverse size measurement of electron beam by using interferometer
March 16, 2010 SLAC National Accelerator Laboratory
POSTECHPAL
Pohang Accelerator Laboratory (PAL), Korea
Fs-THz beam lineTest facility of injector for XFEL
Gun Test facility for XFEL
160-m long 2.5-GeV S-band PLS Linac2.5-GeV 3rd generation Pohang Light Source (PLS)
3/57SLAC National Accelerator LaboratoryMarch 16, 2010
POSTECHPAL
Contents
1. Facilities in PAL
2. S-band RF gun development in PAL
3. A study of electron beam measurement by using electro-optic crystal
4. Transverse size measurement of electron beam by using interferometer
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POSTECHPAL1st - RF gun in PAL, 2005
RF Gun Bellows Goniometer Motion Stages
Slit & Pinhole Screen
View A
View A
RF Gun Bellows Goniometer Motion Stages
Slit & Pinhole Screen
View A
View A
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POSTECHPALEmittance Evolution measurement
JJAP. Vol. 46, p.1751 (2007)
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1st RF gun in PAL, 2005
2005 2008
fs-THz beam line
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OTR FIR Undulator Radiation(future option) Beam energy : 60 MeV max.
Beam Charge : 0.1 – 0.5 nC Beam Emittance: < 5 mm-mrad Beam Pulse Repetition rate: 30 Hz max. Bunch Length
Before chicane: 0.15 - 2 ps After chicane: 20 - 200 fs
Beam Charge
Bunch Length after RF-gun
Bunch Length after Chicane 2
0.2 nC 0.3 ps < 50 fs
0.5 nC 1 – 2 ps < 150 fs
fs-THz Linac Layout
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POSTECHPAL1st RF gun in PAL, 2005
2005 2009
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POSTECHPAL
2nd RF gun in PAL
March 16, 2010 3rd ILC Asian R&D Seminar, SAMEER, MUMBAI
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POSTECHPAL
3rd ILC Asian R&D Seminar, SAMEER, MUM-BAI
March 9-10, 2010
Cavity and Cathode
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Cavity surface – after machining
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30 nm
RMS~4nm
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Cavity surface
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100 nm40 nm, after cleaning
RMS~7nm
RMS~12nm
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Cavity surface
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100 nm40 nm
RMS~10nm RMS~10nm
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before brazing
after brazing
Cathode
E-gun after braz-ing
2nd - RF gun in PAL, 2008
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RF property of 2nd Gun without tuning pin in wave guide
modes π-mode 0-modeResonant frequency 2856.975 2853.600
Coupling β = 1.853 (Over ) β = 0.869 (Under )
Q0 12698 10119
QL 4450 4717
π-mode0-mode
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POSTECHPAL
RF property of 2nd Gun with tuning pin in wave guide
modes π-mode 0-modeResonant frequency 2856.975 2853.600
Coupling β = 1.853 (Over ) β = 0.869 (Under )
Q0 12698 10119
QL 4450 471717/57
POSTECHPAL Gun Test Facility in PAL-2009
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POSTECHPAL Experiment in February 2009
Measured energy spread (squares). The electron beam energy is measured as 2.5 MeV. Solid line is Gaussian fit. Axis on the top is the expression of energy spread in terms of the wavelength from 0.0042 Å. The Laser radius at the cathode is 400um. The electron charge is 1pC. The longitudinal shape of laser is Gaussian. The pulse length of laser is 3ps (FWHM). The laser injection phase is 32.5o.
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POSTECHPAL Low energy case with FED condition
(a) Measured energy (filled dot) vs injection phase. (b) Measured energy spread (filled dot) vs injection phase. Electron beam energy is measured as 2.5 MeV. Theory (solid line), PARMELA simulation (diamond).
(a) (b)
20 1 sin sin sin
2 f fW m c kL kL kL 00
1W dWW W d
0
0
1 2152sin
6
f
20 0/qE m c k
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POSTECHPAL Energy spread effect on FED
(a) Diffraction pattern of polycrys-talline Al without the energy disper-sion
(a) (b)
1/ 22 2 20/ ,r k l m L a
where a0 = 4.05 Å is the lattice constant, L is the distance from the sample to the detector, λ is De Broglie wavelength of the electron, and (k, l, m) are Miller indices for the diffraction plane in the alu-
minum.
J. Korean. Phys. Soc. Vol. 54, p. 2247.
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(b) Blurred image of the diffraction pattern with 200 keV energy dispersion. Beam energy is 2.5 MeV.
POSTECHPAL High energy cases
March 16, 2010 3rd ILC Asian R&D Seminar, SAMEER, MUMBAI
Measured energy spread . The electron beam energy is measured as 4.8, 5.0, 5.2 MeV. The Laser radius at the cathode is 400um. The electron charge is ~100 pC. The longitudinal shape of laser is Gaussian. The pulse length of laser is 3ps (FWHM).
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POSTECHPAL
RF Gun development project2008~2012
Budget: 1 M$ (0.2 M$/year)
March 16, 2010 3rd ILC Asian R&D Seminar, SAMEER, MUMBAI
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Cavity + 1 PortCavity Cavity + 2 Ports
Cavity + 4 Ports
y
x
zE
Basic Concept of Four Ports method
By SLAC
By POSTECH
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POSTECHPALImprovement of RF gun
Quadrupole mode elimi-nation by adding two side cavities
By POSTECH
Emittance reduction by four ports in full cell
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POSTECHPALTest cavity design: four ports RF gun for low power test• Test cavity type: BNL/SLAC/UCLA 1.6-cell photocathode RF gun with input wave-
guide and three symmetric vacuum ports.
March 9-10, 2010 3rd ILC Asian R&D Seminar, SAMEER, MUM-BAI
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POSTECHPALField measurement set up
cathode
xy
z
θ xρ = 10 mm
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POSTECHPALLow power test result: |Ez|
Case 1: Cavity + 1 waveguide Case 2: Cavity + 1 waveguide + 1 vacuum port
Case 3: Cavity + 1 waveguide + 3 vacuum ports
θ xρ=10 mm
y
Coordinates system
Simulation result
Experimental resultRed fitting line
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3rd RF gun for fs-THz Facility
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Requirements:
Vacuum : < 5x10-10 torr
Emittance: < 1 mm mrad
Operating frequency: 2.856 GHz
Field balance(*Eh/**Ef)of π mode: ~1
Mode separation(fπ-f0): ~10 MHz
Coupling factor : ~1
Pulse repetition rate: >30 Hz
*Eh: Maximum E-field in half cell**Ef: Maximum E-field in full cell
Cold model
In real gun, the tuners will be removed and the ports will be used as vacuum ports.
3rd RF Gun for fs-THz Facility at PAL
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POSTECHPAL
3rd ILC Asian R&D Seminar, SAMEER, MUM-BAI
March 9-10, 2010
Cavity and Cathode
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POSTECHPALThermal analysis
heat generation by the rounded port
temperature distribution 59.172 ℃ ~ 107. 406 ℃
temperature distribution 31.408 ℃ ~ 63.149℃
ΔT ~ 48 ℃ ΔT ~ 21 ℃
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POSTECHPAL
Brazing of RF Gun and Wave guide
brazed at February 2010
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Yesterday
SLAC National Accelerator LaboratoryMarch 16, 2010
POSTECHPAL
Contents
1. Facilities in PAL
2. S-band RF gun development in PAL
3. A study of electron beam measurement by using electro-optic crystal
4. Transverse size measurement of electron beam by using interferometer
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POSTECHPAL
Electro-Optic crystal
March 16, 2010 SLAC National Accelerator Laboratory
The refractive indices of the Electro-optic crystal are changed by the electric field from the electron beam.
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POSTECHPAL
E
Coordinates
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POSTECHPAL
Principal refractive indices
30 41
1 0
30 41
2 0
2
2
n r En n
n r En n
31 2 0 41
0
3 12
9
9 6
2( )
2 *200( ) *(2.7) *4.0*10 *800( )
2 *19.68*10 *
360 *20*10 *10
7.2
d dn n n r Ec
m Enm
E
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320 41
1 0
320 41
2 0
sin 1 3cos2
sin 1 3cos2
n r En n
n r En n
POSTECHPAL
150m
in Tunnel
TEO
Courtesy from A. Azima
Timing EO setup
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POSTECHPAL
SNR enhancement with wave plates
/ 2
/ 2
/ 4
/ 4
/ 2
/ 2
cos sinsin cos
00
00
00
i
i
i
i
i
i
R
eEO
e
eQ
e
eH
e
1, , 1 sin sin 2 4 cos cos 2 cos 2 42
1, , 0 1 cos 2 cos 2 42
I
I
10 1 . . . . . . . / 4 . . / 4 .
0vE R H R R Q R R EO R
, ,I
, , 0I
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POSTECHPAL
=0 , 1
NIMA 586 (2008) p.452
SNR enhancement
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POSTECHPAL
Analysis of the electro-optic measure-ment at FLASH
44660 , 2 , 1 sin sin 2 ( 2 ) cos cos 2 ( 2 ) cos 2 ( 2 )2
47.6
I
With Electron beam
0
= 2
7.13
=800 MeV2
GaP d = 180 =0.8 nC
100
Er mm
mQFWHM fs
0, , 1 sin sin 2 4 cos cos 2 cos 2 42II
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POSTECHPAL
laser
electron beam
E
X = [-1,1,0]Y = [0,0,1]
yor
o
o
cos
tan
R ryr
R
y EO crystal
electron beamX
(a) (b)
polarization
polarization
Experimental setup
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Change of laser delay
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laser
X = [-1,1,0]Y = [0,0,1]
y
E
laser
X = [-1,1,0]Y = [0,0,1]
y
E
POSTECHPAL
2 21 2
2 21 2
21 sin(2 ) 1 sin(2 )
21 sin(2 ) 1 sin(2 )
A
B
n
n n
n
n n
An
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( )A Bd n nc
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A
B
45
A
X
Quantification of polarization change
POSTECHPAL
Quantification of polarization change
J. Opt. A:Pure Appl. Opt., vol. 11, p.105704 (2009)
or 2mm
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0A B
dn n
c
POSTECHPAL
Origin of low signal
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laser
E
laser
E
POSTECHPAL
Contents
1. Facilities in PAL
2. S-band RF gun development in PAL
3. A study of electron beam measurement by using electro-optic crystal
4. Transverse size measurement of electron beam by using interferometer
March 16, 2010 SLAC National Accelerator Laboratory 47/57
POSTECHPAL
Source
Slit
Screen
LD
P
RdO
x
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POSTECHPAL
Simulated interferogram
212sin( )2 1 cosJ vuI
u v
/u kax R
max /v k d L
/kdx R
March 16, 2010 SLAC National Accelerator Laboratory
max min
max min
I IVisibility
I I
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POSTECHPAL 1B1 diagnostics beam line in PAL
J. Sync. Rad. Vol. 16, p. 642March 16, 2010 SLAC National Accelerator Laboratory
Uniform distribution
Gaussian distribution
Experimental result
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POSTECHPAL Fourier transform and visibility
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max min
max min
I IVisibilityI I
POSTECHPAL Inverse Fourier transformation
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POSTECHPAL Reconstruction of transverse distribution
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POSTECHPAL
2 2
2sin( )( ) 2 1 exp cos2
uI P vu
/u kax R
/v kd L
/kdx R
2sin( )2 1 cosA BxI E Cx D
x
A = 2.281,B = 0.4145, C = 7.995, D = 1.817, E = 0.7943.
Measurement result in February 2010
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POSTECHPAL Reconstruction of transverse distribution
Reconstructed shape of electron beam
Measured phasesMeasured visibilities
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Experimental pattern
Theoretical calculation with point source
Theoretical calculation with finite size source
31m10m100 m
s
d
rra
35 m
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Study on the visibility
2
0 2/ exp8 tc
aV Vl
20
0 20
4 3cos4
a aVa a
Eq. (8) Eq. (9)
20
4 d s
s d
r ra
r r
31m10 m
s
d
rr
18keV
Theoretical calculation with point source
Theoretical calculation with finite size source
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POSTECHPAL Summary1. RF gun development - I have many experiences on development of RF electron gun for the XFEL. To design the RF gun, I used the POISSON code and PARMELA also. For the three dimensional analysis of the field distribution in the cavity, I used CST Microwave Studio. As postdoctoral position in Pohang Accelerator Laboratory, I carried out a big Project for the development of RF gun for 4th generation light source XFEL, as you can see in the Ref. [3]. I worked with three Ph.D. candidates whom work under my supervisor. I believe that I can lead a group to carry out a project. I fully understand the emittance compensation process in the injector part of the XFEL.
2. Electron beam diagnostics- I have also many experiences on the diagnostics of electron beam using electro-optic crystal. To measure very short electron beam such as 100 fs bunch length and measuring the arrival timing for the pump and probeexperiment in XFEL, this technique is very promising method. I made myself simulation code to simulate many situations of electron beam diagnostics in accelerator such as bunch charge, bunch length, beam energy, etc. I also have experience working on FLASH machine in DESY during 5 months. I made a contribution to upgrade the EO diagnostics setup with my simulation code. I found the origin of low signal in the EO setup. Many papers are published with this subject as you can see in the list of publications, as you can see in the Ref. [1, 5, 7, 8].
3. XFEL design experience-In my Ph.D. course, I am involved also to the design of the 4th generation light source XFEL. This XFEL is called PAL-XFEL as you can see in the Ref. [13, 15] in the publication list. I can simulate the electron beam dynamics with PARMELA, ELEGANT.
4. Storage ring experience- I also have many experiences on the machine study of Pohang Accelerator Laboratory such as transverse beam size measurement with interferometer in diagnostics beam line, as you can see in the Ref. [2]. I also have many interesting on the dynamics of electron beam in the 3rd generation storage ring.
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POSTECHPAL
Thank you for your attention
March 16, 2010 SLAC National Accelerator Laboratory
POSTECHPAL
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Bunching part of the electron beam
Charge distribution
Gaussian-Bunching Part
2
20
exp2 22 2 to t
t q tE tr r c
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POSTECHPAL
3D Refractive indices
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Refractive indices
2 2 2 2 2
2 2 21 2 3
2 2 2 2 2
2 2 21 2 3
2sin 1 cos cos 1 cos sin
2cos 1 cos sin 1 cos sin
AL L L L L
BL L L L L
n
n n n
n
n n n
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Analysis and simulation
or 3mm
or 2.5mm
or 2mm
Simulation resultExperimental result
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