S S - - PowerPoint PPT Presentation
S S FEL FEL
京 京都大学・ 都大学・S Sバンド熱陰極高周波電子銃の現状 バンド熱陰極高周波電子銃の現状
～ ～FEL FEL発振のための入射電力 発振のための入射電力振幅 振幅・ ・位相 位相制御 制御～ ～ Toshiteru Toshiteru Kii Kii
Institute of Advanced Energy, Kyoto University Institute of Advanced Energy, Kyoto University Hideaki Hideaki Ohgaki Ohgaki Kai Masuda Kai Masuda Heisyun Heisyun Zen Zen Satoshi Sasaki Satoshi Sasaki Takumi Takumi Shiiyama Shiiyama
第 第5 5回 回高周波電子銃研究会 高周波電子銃研究会
Purpose of KU-FEL :
“Compact and Economical MIR-FEL Facility for Energy Science”
bio / chemical / material research with advanced photon Purpose of KU Purpose of KU-
FEL :
“ “Compact and Economical Compact and Economical MIR MIR-
FEL Facility for Energy Science” ”
bio / chemical / material research with advanced photon bio / chemical / material research with advanced photon
H 2O
(水) H 2 (
水素)
C O 2 (
二酸化炭素)
C H 3O H (
メタノール)
脱酸素触媒
（安価な金属／金属酸化物触媒）
酸素付加触媒
クリーン燃料 クリーン燃料
C O H 2 FEL FEL FEL FEL
①自由電子レーザ ②自由電子レーザ ③自由電子レーザ
FEL
FEL
H2O clean fuel
CH3OH
clean fuel H2 CO2
FEL
generation of clean energy source from H2O and CO2
Recycling accelerant Example of applications using FEL Example of applications using FEL Example of applications using FEL Generation of sustainable energy source
Basic study of high-efficiency solar cells Separation of DNA and/or RNA … … … Fingerprint region of molecular = MIR ( 2.5 ~ 10 µm ) Fingerprint region of molecular Fingerprint region of molecular = MIR ( 2.5 ~ 10 = MIR ( 2.5 ~ 10 µ µm ) m ) CO2
clean fuel
H2
20 25 30 35 40 2 4 6 8 10 12 14 16 18 20
K = 0.17 K = 0.95 Wavelength (µm) Beam Energy (M eV)
4.7µm
19.0µm 3.3µm
13.2µm
⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ + ≈ 2 1 2
2 2
K
u r
γ λ λ
λR : FEL radiation λu : undulator period [m] B0 : undulator field [T] γ : Lorenz factor
u u
B c m B e K λ π λ ⋅ ≈ ⋅ ⋅ ⋅ = 36 . 93 2 e : charge of the electron m : mass of electron c : velocity of light
0.26 0.26-
0.045 T Peak Magnetic Field Peak Magnetic Field 25.5 25.5-
45 mm Gap Gap 40 mm 40 mm Period Period 0.99 0.99-
0.17 K K-
value 40 40 Period Number Period Number 1.6 m 1.6 m Length Length Halbach Halbach Type Type ~5 ~5 µ µsec sec Macropulse Macropulse 4.5 cells 4.5 cells Structure Structure S S-
band Frequency Frequency
Cathode LaB6 ~1900 ºC (since Sep. 2007)
Why therminonic RF gun?
Compact, Easy to operate, inexpensive…..
What is the demerits?
Back-Bombardment problem
RF RF power power cathode cathode
Problem in thermionic RF gun (1) Problem in thermionic RF gun (1)
thermionic thermionic cathode cathode Beam loading increases and then Beam loading increases and then resonant frequency of cavity changes. resonant frequency of cavity changes. Beam current becomes Beam current becomes unstable. unstable. Maximum pulse duration is limited to Maximum pulse duration is limited to at most several at most several µ µ sec. (at the gun exit)
Time evolution of electron beam and input/reflected RF power Time evolution of electron Time evolution of electron beam and input/reflected beam and input/reflected RF power RF power Back Back-
streaming electrons hit cathode. hit cathode. Cathode Cathode temperature increases. temperature increases. Current density on cathode surface Current density on cathode surface increases. increases.
Problem in thermionic RF gun (2) Problem in thermionic RF gun (2) Macro pulse duration after the bending Macro pulse duration after the bending magnet was less than 500 ns. magnet was less than 500 ns.
Cathode φ 6 mm T surface = 1000 ℃
2 4 6
0.00 0.02 0.04 0.06 0.08
CT3における電流量 (A) Sw eep (A T)
B e a m c u r r e n t ( A )
Time (µsec)
Beam current after the bending magnet
cathode
heater
1st cavity
electrons
Evaluation of the back streaming electrons (1) Evaluation of the back streaming electrons (1)
RF RF power power cathode cathode
Measure the Measure the surface temp. surface temp. by using IR by using IR thermometer thermometer modeling modeling
Evaluating Method Evaluating Method
0-dimensional model
Heater power, Ph Pｂ BT AT4 Cathode surface temperature, T
1999~2001 1999~2001
45sec
ΔTav ~ 20°C
without beam
with beam
without beam
P Pheater
heater +
+P Pbeam
beam
P Pheater
heater
P Pheater
heater
1 2 3 4 5 6 7 8 0.0 0.4 0.8 1.2 1.6 2.0
<P b> [W] RF input [MW] experimental evaluation (i) experimental evaluation (ii) simulation
Comparison with PIC simulation KUBLAI Back Back-
streaming beam power was not negligible.
1 1 pps pps operation
Heater power : about 10 W Heater power : about 10 W
Evaluation of the back streaming electrons (2) Evaluation of the back streaming electrons (2)
1 dimensional model 1 dimensional model
Q Qh
h
Back Back-
streaming electros electros
Q Qb
b(
(x, x,t t) ) x x
[ ]
[ ]
[ ]
⎜ ⎜ ⎜ ⎜ ⎝ ⎛ = = × =
−
K kg J m kg m J C / / 155 / 19000 sec/ / 10 67 . 5
3 8
λ ρ
) , (
2 2
τ λ τ ρ x Q x T T V C
b
+ ∂ ∂ = ∂ ∂
heater heater
To estimate the time evolution of the cathode surface including To estimate the time evolution of the cathode surface including the effect the effect
cathde, 1 dimensional model was developed. , 1 dimensional model was developed.
Cathode Cathode
2002 ~ present 2002 ~ present
Why therminonic RF gun?
Compact, Easy to operate, inexpensive…..
What is the demerits?
Back-Bombardment problem Back-streaming electrons hit the cathode Surface temperature rises Beam current increases Beam loading increases Beam energy decreases Macropulse duration decreases Input modulated RF power Beam energy is kept constant Macropulse duration increases
1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10
Time [µsec] Power [MW]
Flat RF Modulated RF
RF amplitude modulation for beam energy compensation
14% modulation
Macropulse duration was improved Beam energy was kept constant. Results
1 2 3 4 5 6 7 8 9 10 20 40 60 80 100
Flat RF Modulated RF
Current [mA] Time [µsec]
3 4 5 6 7 6.0 6.5 7.0 7.5 8.0 8.5 9.0
Energy [MeV] Time [µsec]
Flat RF Modulated RF
But phase advance was observed.
Input rf Output rf Vk =148 kV Vk =158 kV
Amplitude modulation Klystron voltage increases Electron velocity changes Schematic view of Klystron
Origin of the phase advance
5 10 15 200 400 600 2 4 6 8
Current [mA] Time [µs]
Igun Pref Pin Beam Power [MW] Klystron Voltage / 20 [kV]
2 4 280 300 320 340 360 380 400 420
Phase [deg.] Time [µs]
~40 deg.
Vk =148 kV 330 degree Vk =158 kV 370 degree
Phase advance in the macro pulse
S.G.
PS PS
Kly#2 Kly#1
29dB
FG
Phase Compensation
ch.1 ch.2
Phase Detector PC Acc
~103dBm
Gun
~100dBm
Block diagram of the Phase Compensation
SG : Signal Generator PS : Phase Shifter FG : Function Generator PC : (Computer) ADC & DAC
2 4 280 300 320 340 360 380 400 420
Phase [deg.] Time [µs]
~40 deg.
2 4 136 138 140 142 144
Phase [deg.] Time [µs]
~2 deg.
Results (Amplitude & Phase modulation) Phase stability : < 2 deg.
Without Phase compensation With Phase compensation
Time [µs] Current [A] AM on, PM on AM off, PM off 2 4 0.02 0.04 0.06
Results (Amplitude & Phase modulation) Macro pulse duration@ FC2
830 ns 4.0 µs
Results (Amplitude & Phase modulation) Energy distribution @FC2
AM = off, PM = off AM = on, PM = on
Results (Amplitude & Phase modulation) Energy distribution @ACC out
1 2 3 4 5 21 22 23 24 25 26 27
Time [µs] Energy [MeV]
40 80 120 160
Current [mA]
1 2 3 4 5 21 22 23 24 25 26 27
Time [µs] Energy [MeV]
40 80 120 160
Current [mA]
Acc AM = off, Acc PM = off Acc AM = on, Acc PM = on
23 24 25 26 50 100 150 200
w/o Acc BL comp.
with Acc BL comp.
Results (Amplitude & Phase modulation) Energy distribution @ACC out
Thermionic RF gun : ☠back-bombardment☠ Beam loading increases during macro pulse. Amplitude modulated RF was tested. Beam energy was successfully compensated. But… phase advance was observed. Phase advance was compensated by phase modulation