独立 2 2 空胴型熱陰極高周波 空胴型熱陰極高周波 独立 電子銃の開発 電子銃の開発 Toshiya Muto, Takumi Tanaka, Fujio Fujio Hinode Hinode, Masayuki Kawai, Kenichi , Masayuki Kawai, Kenichi Nanbu Nanbu, , Toshiya Muto, Takumi Tanaka, Kittipong Kasamsook Kasamsook, Kazushi Akiyama, , Kazushi Akiyama, Mafuyu Mafuyu Yasuda, Yasuda, Yoshinosuke Yoshinosuke Mori, Mori, Kittipong Hiroyuki Hama Hama Hiroyuki Laboratory of Nuclear Science, Tohoku University Laboratory of Nuclear Science, Tohoku University 1. Coherent Terahertz Light Source Coherent Terahertz Light Source 1. 2. 極短バンチ生成入射器 極短バンチ生成入射器 2. 電子銃 rf 電子銃 3. ITC ITC- -rf 3. バンチ圧縮器 4. バンチ圧縮器 4. 5. 今後の予定 今後の予定 5. 6. まとめ まとめ 6.
Coherent THz Light Source Coherent THz Light Source Coherent THz Light Source Coherent THz Light Source using Isochronous Ring using Isochronous Ring using Isochronous Ring using Isochronous Ring B+QD 2m 3m B+QF bunch compressor LINAC beam dump ITC RFgun � Ring type multi port facility � Ring type multi port facility � Quasi CW source � Quasi CW source � Isochronous lattice to keep bunch length � Isochronous lattice to keep bunch length � Combined function magnet (B+Q+S, Q+S) � Combined function magnet (B+Q+S, Q+S) � E ~ 200MeV, C ~ 50m � E ~ 200MeV, C ~ 50m
Coherent THz Light Coherent THz Light Coherent THz Light Coherent THz Light Demonstrator Demonstrator Demonstrator Demonstrator undulator bunch compressor accelerating structure THz light beam 1m ITC rf gun � Using � Using undulator undulator radiation radiation � The injector is the completely � The injector is the completely same one of the isochronous one of the isochronous same ring. ring.
Coherent Radiation from Coherent Radiation from Coherent Radiation from Coherent Radiation from the undulator the undulator undulator the the undulator Beam parameter Beam parameter Energy 12MeV Energy 12MeV Bunch charge 20pC Bunch charge 20pC 8 electrons =1.25 x 10 8 electrons =1.25 x 10 σ t Bunch length σ t=100fs =100fs Bunch length π mmmrad 1 π Norm. emittance emittance 1 mmmrad Norm. Undulator Undulator λω =8cm Period length λω =8cm Period length # of period = 15 cycle # of period = 15 cycle Peak magnetic field 0.3T Peak magnetic field 0.3T
Coherent Radiation (II) Coherent Radiation (II) Coherent Radiation (II) Coherent Radiation (II) σ 8 From N =1.25x10 with =100fs From single electron e t 5 ω Ω ω Ω 17 2.5 10 1 dN/d d form factor d dN/d 4 17 2 10 0.8 3 17 1.5 10 0.6 2 17 1 10 0.4 1 16 5 10 0.2 0 0 0 0 50 100 150 200 250 300 350 400 0 50 100 150 200 250 300 350 400 λ µ wave length [ m] λ µ wave length [ m] � Higher harmonics mode were suppressed. � Higher harmonics mode were suppressed.
Coherent radiation (III) Coherent radiation (III) Coherent radiation (III) Coherent radiation (III) 15 3 10 N/0.1%bandwidth[photons] Integrated intensity Integrated intensity 15 2.5 10 integration range integration range −1/γ < θ <1/γ 1/γ < θ <1/γ − 15 2 10 Peak power Peak power 15 1.5 10 ~ 45kW ~ 45kW 15 1 10 µ s macro pulse length ~ 1 µ s macro pulse length ~ 1 14 5 10 0 200 250 300 350 400 λ µ wave length [ m]
極短バンチ入射器 極短バンチ入射器 独立空胴型熱陰極高周波電子銃 独立空胴型熱陰極高周波電子銃 (Independent Tunable Cell thermionic thermionic rf rf gun) gun) (Independent Tunable Cell + + 磁場型バンチ圧縮器 磁場型バンチ圧縮器 六極電磁石付き Triple ( 六極電磁石付き Triple- -bend lattice) bend lattice) (
ITC ITC rf rf rf gun gun gun ITC ITC rf gun 1. Independent 2- -cell cell 1. Independent 2 2nd cell structure structure RF port => manipulate 6- - => manipulate 6 demensional phase demensional phase space space 2. Small single crystal 2. Small single crystal beam LaB 6 cathode LaB 6 cathode 1st cell => very low => very low RF port π mm (1 π emittance (1 mm emittance Prototype ITCRFgun mrad) achieved ) achieved mrad
FDTD Simulation for ITC- -RF RF FDTD Simulation for ITC gun gun 1. Reduced back- - 1. Reduced back bombardment bombardment effect due to small effect due to small cathode cathode 2. High electron 2. High electron density at the head density at the head of the beam train of the beam train (velocity bunching) (velocity bunching)
FDTD simulation (II) : FDTD simulation (II) : FDTD simulation (II) : FDTD simulation (II) : Longitudinal distribution Longitudinal distribution Longitudinal distribution Longitudinal distribution 1 st cell Electric field E1 = 25MV/m E1= 30MV/m
FDTD simulation (III): FDTD simulation (III): FDTD simulation (III): FDTD simulation (III): Transverse phase space distribution Transverse phase space distribution Transverse phase space distribution Transverse phase space distribution E1=25MV/m E2=50MV/m E1=25MV/m E2=50MV/m E1=25MV/m E2=50MV/m E1=25MV/m E2=50MV/m
Beam parameter at the exit Beam parameter at the exit Beam parameter at the exit Beam parameter at the exit of the ITC rf of the ITC rf gun rf gun gun of the ITC of the ITC rf gun initial condition initial condition st cell E1=25MV/m Electric field 1 st cell E1=25MV/m Electric field 1 nd cell E2 = 50MV/m 2 nd cell E2 = 50MV/m 2 Phase difference between cells ∆φ ∆φ =180+18deg =180+18deg Phase difference between cells Extracted beam Extracted beam maximum momentum Pmax maximum momentum Pmax= 1.77MeV/c = 1.77MeV/c ∆ p/p momentum spread ∆ p/p=0.02 =0.02 momentum spread * Whole beam has 100% energy spread. * Whole beam has 100% energy spread. -> beam is collimated by a slit. > beam is collimated by a slit. - emittance ε ε n=0.77pmm norm. emittance n=0.77pmm mrad mrad norm. bunch charge Ie Ie= 30pC = 30pC bunch charge σ t bunch length σ t = 5ps (Full width) = 5ps (Full width) bunch length α,β β,γ ,γ )=(1.11,1.21,2.22) parameter ( α, Twiss parameter ( )=(1.11,1.21,2.22) Twiss
Measurements of the ITC Measurements of the ITC rf rf rf Measurements of the ITC Measurements of the ITC rf gun prototype gun prototype gun prototype gun prototype Electric Field Distribution 12 ] U . SUPERFISH Measured SUPERFISH Measured A . 1st cell measured 10 2nd cell measured Ez[ f 1st 2856MHz 2810.81MHz f 2856MHz 2810.81MHz 1st cell SUPERFISH 1st 2nd cell SUPERFISH f 2nd 2856MHz 2825.76MHz f 2856MHz 2825.76MHz 8 2nd β 1st β - 3.5 - 3.5 1st 6 β 2nd β - 4.4 - 4.4 2nd 4 Q 0_1st Q 13000 13000 7900 7900 0_1st Q 0_2nd Q 12500 12500 12000 12000 0_2nd 2 Ω Ω 98.2 Ω 117 Ω R/Q 1st R/Q 98.2 117 1st Ω Ω 114.6 Ω 129 Ω 0 R/Q 2nd R/Q 114.6 129 2nd -2 0 2 4 6 8 10 z[cm] From 3D electromagnetic calculation, it was found that the shift of resonant frequencies is caused by the effect of rf input ports
Q 低下 低下 Q
One Example of One Example of One Example of One Example of calculation calculation calculation calculation coupling of 2 nd cell : β 2 Q 0 = 12038 Q ext = 2748.27 β 2 =12038/2748.27-1=3.38 CST-STUDIO による 3 次元電磁場計算
Bunch Compressor Bunch Compressor Bunch Compressor Bunch Compressor In case of a thermionic thermionic rf rf gun, gun, In case of a α - usually an α -magnet is used for bunch compression... magnet is used for bunch compression... usually an Triple- -Bend lattice with Bend lattice with sextupoles sextupoles Triple ∆ p/p)/dt 1) to fit various ( ∆ p/p)/dt 1) to fit various ( ∆ p/p σ t Typically ∆ =2% and σ p/p=2% and t=5ps =5ps - -> ~ 100fs > ~ 100fs Typically 2) to compensate 2nd order dispersion 2) to compensate 2nd order dispersion α - Difficult for α Use sextupoles sextupoles between bends < between bends <- - Difficult for -magnet!! magnet!! Use Problems Problems ∆β /( ∆ p/p Since low energy, ∆β /( ∆ p/p) is not neglect. ) is not neglect. Since low energy, ∆ p/p > p=1.77MeV/c, ∆ -> p=1.77MeV/c, p/p=2%, pass length= 1m =2%, pass length= 1m - -> time difference is 5ps!! - > time difference is 5ps!! -> limit for the length of the bunch compressor > limit for the length of the bunch compressor - β function must be small. β function must be small. β - > to reduce the effect of pass length difference(R51) by β -> to reduce the effect of pass length difference(R51) by -function function - amplitude amplitude
Bunch Compressor (II): Bunch Compressor (II): Bunch Compressor (II): Bunch Compressor (II): Optics Optics Optics Optics 1. Low β x to minimize bunch compressor 3.5 0.35 R51. QF1 QF1 QF2 QF2 2. Control R56 by 3 0.3 B B SD B SD quadrupoles inside. 2.5 0.25 3. Sextupole controls QD2 QD2 QD1 QD1 higher order 2 0.2 dispersion. η x β y 1.5 0.15 あくまで仮デザインである 1 0.1 ・空間電荷効果 ・ CSR の影響 0.5 0.05 β x ・磁石の端部効果 ・アライメント精度 0 0 0 0.4 0.8 1.2 1.6 2 2.4 を考えなきゃいけない s[m]
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