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独立 独立2 2 空胴型熱陰極高周波 空胴型熱陰極高周波 電子銃の開発 電子銃の開発

Toshiya Muto, Takumi Tanaka, Toshiya Muto, Takumi Tanaka, Fujio Fujio Hinode Hinode, Masayuki Kawai, Kenichi , Masayuki Kawai, Kenichi Nanbu Nanbu, , Kittipong Kittipong Kasamsook Kasamsook, Kazushi Akiyama, , Kazushi Akiyama, Mafuyu Mafuyu Yasuda, Yasuda, Yoshinosuke Yoshinosuke Mori, Mori, Hiroyuki Hiroyuki Hama Hama Laboratory of Nuclear Science, Tohoku University Laboratory of Nuclear Science, Tohoku University

1.

• 1. Coherent Terahertz Light Source

Coherent Terahertz Light Source 2.

• 2. 極短バンチ生成入射器

極短バンチ生成入射器 3.

• 3. ITC

ITC-

• rf

rf電子銃 電子銃 4.

• 4. バンチ圧縮器

バンチ圧縮器 5.

• 5. 今後の予定

今後の予定 6.

• 6. まとめ

まとめ

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

• 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

ITC RFgun

3m 2m

LINAC

bunch compressor

beam dump B+QF B+QD

• Using

Using undulator undulator radiation radiation

• The injector is the completely

The injector is the completely same same one of the isochronous

• ne of the isochronous

ring. ring.

ITC rf gun bunch compressor accelerating structure undulator THz light beam 1m

Coherent THz Light Coherent THz Light Coherent THz Light Coherent THz Light Demonstrator Demonstrator Demonstrator Demonstrator

Coherent Radiation from Coherent Radiation from Coherent Radiation from Coherent Radiation from the the the the undulator undulator undulator undulator

Beam parameter Beam parameter Energy Energy 12MeV 12MeV Bunch charge 20pC Bunch charge 20pC =1.25 x 10 =1.25 x 108

8 electrons

electrons Bunch length Bunch length σ σt t=100fs =100fs Norm.

• Norm. emittance

emittance 1 1π πmmmrad mmmrad Undulator Undulator Period length Period length λω λω=8cm =8cm # 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)

• Higher harmonics mode were suppressed.

Higher harmonics mode were suppressed.

1 2 3 4 5 50 100 150 200 250 300 350 400

From single electron

wave length [ m] λ µ dN/d d ω Ω wave length [ m] λ µ

From N =1.25x10 with =100fs

e 8 t

σ

dN/d d ω Ω

5 10

16

1 10

17

1.5 10

17

2 10

17

2.5 10

17

0.2 0.4 0.6 0.8 1 50 100 150 200 250 300 350 400

form factor

Coherent radiation (III) Coherent radiation (III) Coherent radiation (III) Coherent radiation (III)

Integrated intensity Integrated intensity

integration range integration range − −1/γ < θ <1/γ 1/γ < θ <1/γ

Peak power Peak power ~ 45kW ~ 45kW

macro pulse length ~ 1 macro pulse length ~ 1µ µs s

5 10

14

1 10

15

1.5 10

15

2 10

15

2.5 10

15

3 10

15

200 250 300 350 400

wave length [ m] λ µ N/0.1%bandwidth[photons]

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 (Independent Tunable Cell thermionic thermionic rf rf gun) gun) + + 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 六極電磁石付き Triple Triple-

• bend lattice)

bend lattice)

ITC ITC ITC ITC rf rf rf rf gun gun gun gun

• 1. Independent 2
• 1. Independent 2-
• cell

cell structure structure => manipulate 6 => manipulate 6-

• demensional phase

demensional phase space space

• 2. Small single crystal
• 2. Small single crystal

LaB LaB6

6 cathode

cathode => very low => very low emittance emittance (1 (1 π π mm mm mrad mrad) achieved ) achieved

beam 1st cell RF port 2nd cell RF port Prototype ITCRFgun

FDTD Simulation for ITC FDTD Simulation for ITC-

• RF

RF 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

• f the beam train
• f 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

1st 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

• f the ITC
• f the ITC
• f the ITC
• f the ITC rf

rf rf rf gun gun gun gun

initial condition initial condition Electric field 1 Electric field 1st

st cell E1=25MV/m

cell E1=25MV/m 2 2nd

nd cell E2 = 50MV/m

cell E2 = 50MV/m Phase difference between cells Phase difference between cells ∆φ ∆φ=180+18deg =180+18deg Extracted beam Extracted beam maximum momentum maximum momentum Pmax Pmax= 1.77MeV/c = 1.77MeV/c momentum spread momentum spread ∆ ∆p/p p/p=0.02 =0.02

* Whole beam has 100% energy spread. * Whole beam has 100% energy spread.

• > beam is collimated by a slit.

> beam is collimated by a slit.

norm.

• norm. emittance

emittance ε εn=0.77pmm n=0.77pmm mrad mrad bunch charge bunch charge Ie Ie= 30pC = 30pC bunch length bunch length σ σt t = 5ps (Full width) = 5ps (Full width) Twiss Twiss parameter ( parameter (α, α,β β,γ ,γ)=(1.11,1.21,2.22) )=(1.11,1.21,2.22)

Measurements of the ITC Measurements of the ITC Measurements of the ITC Measurements of the ITC rf rf rf rf gun prototype gun prototype gun prototype gun prototype

• 2

2 4 6 8 10 12 2 4 6 8 10

1st cell measured 2nd cell measured 1st cell SUPERFISH 2nd cell SUPERFISH

Ez[ A . U . ] z[cm]

Electric Field Distribution

From 3D electromagnetic calculation, it was found that the shift

• f resonant frequencies is caused by the effect of rf input ports

129 129Ω Ω 114.6 114.6Ω Ω R/Q R/Q2nd

2nd

117 117Ω Ω 98.2 98.2Ω Ω R/Q R/Q1st

1st

12000 12000 12500 12500 Q Q0_2nd

0_2nd

7900 7900 13000 13000 Q Q0_1st

0_1st

4.4 4.4

• β

β2nd

2nd

3.5 3.5

• β

β1st

1st

2825.76MHz 2825.76MHz 2856MHz 2856MHz f f2nd

2nd

2810.81MHz 2810.81MHz 2856MHz 2856MHz f f1st

1st

Measured Measured SUPERFISH SUPERFISH

Q Q低下 低下

One Example of One Example of One Example of One Example of calculation calculation calculation calculation

Q0 = 12038 Qext = 2748.27 β2=12038/2748.27-1=3.38 coupling of 2nd cell : β2 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 In case of a thermionic thermionic rf rf gun, gun, usually an usually an α α-

• magnet is used for bunch compression...

magnet is used for bunch compression... Triple Triple-

• Bend lattice with

Bend lattice with sextupoles sextupoles 1) to fit various ( 1) to fit various (∆ ∆p/p)/dt p/p)/dt Typically Typically ∆ ∆p/p p/p=2% and =2% and σ σt t=5ps =5ps -

• > ~ 100fs

> ~ 100fs 2) to compensate 2nd order dispersion 2) to compensate 2nd order dispersion Use Use sextupoles sextupoles between bends < between bends <-

• Difficult for

Difficult for α α-

• magnet!!

magnet!! Problems Problems Since low energy, Since low energy, ∆β ∆β/( /(∆ ∆p/p p/p) is not neglect. ) is not neglect.

• > p=1.77MeV/c,

> p=1.77MeV/c, ∆ ∆p/p 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 β function must be small. function must be small.

• > to reduce the effect of pass length difference(R51) by

> to reduce the effect of pass length difference(R51) by β β-

• function

function amplitude amplitude

Bunch Compressor (II): Bunch Compressor (II): Bunch Compressor (II): Bunch Compressor (II): Optics Optics Optics Optics

0.5 1 1.5 2 2.5 3 3.5 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.8 1.2 1.6 2 2.4

bunch compressor

s[m]

QF1 QF1 QD1 QD1 QD2 QD2 QF2 QF2 B B B SD SD

βx βy ηx

• 1. Low βx to minimize

R51.

• 2. Control R56 by

quadrupoles inside.

• 3. Sextupole controls

higher order dispersion.

あくまで仮デザインである ・空間電荷効果 ・CSRの影響 ・磁石の端部効果 ・アライメント精度 を考えなきゃいけない

Without sextupoles With sextupoles

Bunch Compressor (III): Bunch Compressor (III): Bunch Compressor (III): Bunch Compressor (III):

Beam tracking (Longitudinal phase Beam tracking (Longitudinal phase Beam tracking (Longitudinal phase Beam tracking (Longitudinal phase space) space) space) space)

Bunch Compressor (IV): Bunch Compressor (IV): Bunch Compressor (IV): Bunch Compressor (IV):

Beam tracking (transverse phase Beam tracking (transverse phase Beam tracking (transverse phase Beam tracking (transverse phase space) space) space) space)

Without Sextupoles With Sextupoles

六極電磁石によって垂直方向の位相空間は乱されない ＜－ 現状ではものすごく弱いのであたりまえか？

Comparison w ith Comparison w ith Comparison w ith Comparison w ith α α-

• magnet

magnet magnet magnet and TBA and TBA and TBA and TBA

• 15 10
• 3
• 10 10
• 3
• 5 10
• 3

0 10 5 10

• 3

10 10

• 3
• 6 10
• 5
• 4 10
• 5
• 2 10
• 5

2 10

• 5

4 10

• 5

6 10

• 5

set2_tracking_real z[m]

red : α-magnet blue : TBA

2 2nd

nd order dispersion correction by

• rder dispersion correction by α

α-

• magnet

magnet

0.000 50.00 100.0 150.0 200.0

• 6 10
• 5
• 4 10
• 5
• 2 10
• 5

2 10

• 5

4 10

• 5

6 10

• 5

data_alpha0_2mod2

z[m]

z[m] σz=12.93µm =44.9fs

beam trajectory Bunch length

Huge a-magnet and drift space!!

Bohr radius : 22mm pole length :40mm # of turn: 21 T/pole Max. magnetomotive force : 80 AT/pole

バンチ圧縮機用四極電磁石 バンチ圧縮機用四極電磁石

他の磁石も設計中 少なくても今年度中に双極は製作する

ITC ITC ITC ITC rf rf rf rf gun gun gun gun製作 製作

ITC ITC ITC ITC rf rf rf rf gun gun gun gun製作 製作(II) (II) (II) (II)

ITC ITC ITC ITC rf rf rf rf gun gun gun gun

12月3日

2007/11/15

モジュレータ室建設 モジュレータ室建設

2007/12/3 2007/11/28

今後の予定 今後の予定

• ITC

ITC rf rf gun gun 12 12月中 月中 性能測定 性能測定

• Klystron +

Klystron + modulator modulator 電源室（プレハブ） 電源室（プレハブ） 11 11月着工 月着工 2 2月末 月末 完成 完成 搬入 搬入 3 3月初 月初 クライストロン試運転 クライストロン試運転 年度内 年度内 立体回路構築 立体回路構築 4 4月～ 月～5 5月 月

• ビームライン

ビームライン ITC ITC rf rf gun aging gun aging 6~7 6~7月 月

まとめ まとめ

• コヒーレントテラヘルツ光源の開発を行っている。

コヒーレントテラヘルツ光源の開発を行っている。

• シュミレーションから

シュミレーションからITC ITC rf rf gun gunとバンチ圧縮器を とバンチ圧縮器を 組み合わせた入射器でバンチ長 組み合わせた入射器でバンチ長100fs 100fs以下の超 以下の超 短バンチ電子ビーム生成の可能性を得た。 短バンチ電子ビーム生成の可能性を得た。

• 現在

現在ITC ITC rf rf gun gunを製作中。 を製作中。

• 今年度中に電源とクライストロンを立ち上げる予定

今年度中に電源とクライストロンを立ち上げる予定 である。 である。