preliminary design on the 5 mev injector and 500 kv dc gun in ihep · 2013. 7. 28. · 1 yunlong...

China-Korea-Japan Joint Workshop on electron/photon sources and applications @ Shanghai Light source

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Yunlong Chi, Guangwei Wang, Jinqiang Xu Zusheng Zhou, Xiaoping Li

Shuhong Wang2~3, Dec. 2010

Preliminary design on the 5 MeV injector and 500 kV DC gun in IHEP

Shengguang Liuon behalf of our group

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プレゼンテーションのノート

Preliminary .[pri'liminəri]


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Outline

1. Introduction

2. Preliminary Design on the 5 MeV Injector

3. Design on the 500 kV DC Gun

4. Summary


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1. Size： Loop’s circumference ~ 50 m;Square area : ~ 50 m x 12 m = 600 m2

2. Beam energy is 35MeV3. Beam energy out of the injector is 5MeV,10mA

Introduction

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Circumference səˈkʌmfərəns


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Our technological strategyThe first option: Photocathode DC gun

The backup option: 217MHz photocathode RF gun

Introduction


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DC Gun+ solenoid1+NRF buncher+solenoid2+ two 2-cell SRF cavity as energy booster

Normal ERL mode: 77pC1. 500KV 2. 300KV

Preliminary Design on the 5 MeV Injector


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1.3GHz NRF buncher Solenoid

Q：25411.5； We set the maximum field gradient along z axis to 5MV/m, the required CW RF power is about 15KW. Taking account of the 10mA beam energy gain 230KV in the buncher, 2.3KW is needed. The total RF power for buncher is about 17.3KW.



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450 mm 649.2 mm 649.2 mm 450 mm200 mm

2.3984 m4 Main couplers3 HOM dampers 2 Gate valves2 2-cell cavities



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E-Field B-Field

Emittance

Beam size Energy

Bunch length

500KV 77pC



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Simulation conditions：（1）Charge/bunch 77pC；（2）Laser RMS beam size 1.2mm； flat top laser, flat top 20ps，rise time

2ps；（3）initial kinetic energy is assumed to 0.2eV (GaAs cathode driven by 532nm)；（4）High voltage of the DC gun 500kV, maximum field gradient on z-axie is

6.45MV/m； maximum field gradient on the cathode surface 5.48MV/m；（5）Maximum B-field of solenoid 1 is 430Gauss； Maximum B-field of

solenoid 2 is 400Gauss；（6）Buncher 1.3GHz, Maximum e-field is 5MV/m；（7）two 2-cell SRF cavity，maximum e-field is 20MV/m ；

Simulation results：Beam energy is 5MeV，RMS energy spread is 0.72%，RMS normalized emittance is 1.49mm.mrad,RMS bunch length is 0.67mm.

500KV 77pC


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Initial kinetic energy of the photon-electron


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Simulation conditions：（1）Charge/bunch 77pC；（2）Laser RMS beam size 1.6mm； flat top laser, flat top 30ps，rise time

2ps；（3）initial kinetic energy is assumed to 0.2eV；（4）High voltage of the DC gun 300kV, maximum field gradient on z-axie is

6.45*0.6MV/m； maximum field gradient on the cathode surface 5.48 * 0.6MV/m；

（5）Maximum B-field of solenoid 1 is 320Gauss； Maximum B-field of solenoid 2 is 320Gauss；

（6）Normal conducting buncher 1.3GHz, Maximum e-field is 5MV/m；（7）two 2-cell SRF cavity，maximum e-field is 20MV/m ；

Simulation results：Beam energy is 5.0MeV，RMS energy spread is 24KeV，RMS normalized emittance is 2.3mm.mrad,RMS bunch length is 0.8mm.

300KV 77pC


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Initial kinetic energy of the photon-electron


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ERL photo-injector based on 217MHz NRF Gun



Superfish model CST model

Model Code Frequency (MHz)

Q P_total (kW)

Pd_max (w/cm^2)

R (Mohm)

R/Q Stored energy (J)

Vc (kV)

Superfish 216.49 29989 41.96 13.65 5.96 198.7 0.93 500 Model1 MWS 216.42 29622 42.4 14.75 5.90 199.1 0.92 500

Superfish 216.06 27888 48.67 16.56 5.14 184.2 1.00 500 Model2 MWS 215.96 27602 49.65 18.60 5.03 182.4 1.01 500

1300MHz ÷6 = 216.7MHz



3D simple RF model 3D complicated RF model

Code Frequency

(MHz)

Q0 Total loss

(kW)

R

(MOhm)

R/Q Vc

(kV)

Max power

density(W/cm^2)

Total energy

(J)

Superfish(1) 216.49 29989 41.96 5.96 198.7 500 13.7 0.925

MWS-simple(2) 216.42 29622 42.39 5.90 199.1 500 14.7 0.923

MWS- complicated(3) 216.64 30379 35.54 7.03 231.5 500 18.1 0.793

500KV 38KW RF power750KV 85KW RF power



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E-Field

B-Field


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Emittance Beam size

EnergyEnergy spread



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Simulation conditions：（1)Charge/bunch 77pC；（2)Laser RMS beam size 0.6mm； flat top laser, flat top 20ps，rise

time 2ps；（3)initial kinetic energy is assumed to 0.2eV；

（4)In the gun, maximum field gradient on z-axie is 13MV/m(~500kV);(5)Maximum B-field of solenoid 1 is 430Gauss；

Maximum B-field of solenoid 2 is 400Gauss；（6) Buncher 1.3GHz, Maximum e-field is 5MV/m；

（7)two 2-cell SRF cavity，maximum e-field is 20MV/m ；

Simulation results：Beam energy is 5.1MeV，RMS energy spread is 0.45%，

RMS normalized emittance is 0.85mm.mrad,RMS bunch length is 0.73mm



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JLAB Gun (Older version)

Design on the 500 kV DC Gun

Jlab has good records on DC Gun:

Demonstrated ~ 10 mA CW operation,

Has operated 3 years

Good vacuum condition ~10-11

torr

Long cathode life time:

(30 hours operation at 5 mA CW)

JLAB Gun (new version) Large electrode area to reduce surface gradient, higher

operating voltage Niobium electrodes (take advantage of SRF processing

techniques) Bulk resistivity ceramic Load lock (various cathode types) Massive pumping for good vacuum Focusing geometry Light-box free operation Isolated anode for bias

500 KeV DC gun for JLAMP VUV/Soft X-ray User Facility


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HV terminal

support rod

cathode

anode

e-beam

gun chamber

500-kV gun with a segmented insulator

Segmented insulator with guard rings

guard ring against field emission

field emission

ceramicguard ring

segmented insulator

500 kV for 8 hours without any discharge



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Cornell[8] JLab-FEL[9] KEK/JAEA[10-11] IHEP

HV 750kV 350kV 500kV 500kV

cathode GaAs:Cs GaAs:Cs GaAs:Cs GaAs:Cs

QE 12-15%（ initial ）1%

5-7%（initial）1%

5-7%（ initial ）1%

5-7%（ initial ）1%

lifetime 100h 30h 20h 20h

laser 20W, 520 nm 4W，526.5nm 1.5W-15W，530nm 2.3W，530nm

Repetition rate

1.3GHz 74.85MHz 130MHz-1.3GHz 130MHz，1.3GHz*

Transverse emit.

0.3mm.mrad 7.0mm.mrad 1.0mm.mrad 0.1mm.mrad（7.7pC）

< 2.0mm.mrad 0.1mm.mrad（7.7pC）

Bunch charge

77pC 150pC 77pC 77pC

Average current

100mA 9.1mA 10-100mA 10mA

* Two operation modes：（1）130MHz，10mA，77pC；（2）1300MHz，10mA，7.7pC。



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Gun chamber

Stock chamber

Multiple cathode cleaning

Multiple activated photocathode preservations

Cs & O2

Loading Chamber

PreparationChamber

10-8 Pa 10-9 Pa

10-10 Pa < 10-10 Pa

Installation of PlugQuick exchanges of Plug

Long-term gun operation is guaranteed by multiple plug system.

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Multiple NEA-surfaces are formed simultaneously.


プレゼンター


This figure shows a brief the 2nd gun system. Vacuum condition of each chamber about 1E-8 to 1E-10 or less. Several cathodes fixed on a puck revolver and installed in the loading chamber. In the loading chamber, the cathodes are cleaned by atomic hydrogen and heating. Then transferred to the activation chamber, and create NEA surface by Cs and oxygen deposition. Then transferred to the stock chamber. In the stock chamber, the cathodes are preserved in extreme high vacuum to maintain high cathode QE condition. Then, one cathode is transferred to the gun. If the cathode QE is decreased, we can exchange the extra fresh cathode quickly. This is our multi-puck system concept. （補足）カソードの寿命の問題（10mAでは最良の結果でも1日程度しか持たない現状）がすぐに解決できない場合、カソードを効率よく準備できるシステムの開発は重要と思われる。 NEA表面をさ


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由进样室、制备室、储存室组成，利用磁力传递杆将样品在各个真空室之间传递。一、进样室：

1、真空获得：200L/S的SAES泵（意大利）+200L/S的离子泵（三井+Hipace700全无油分子泵机组（德国普发，四个真空室共用）。2、真空测量：数显复合冷阴极规（真空计TPG262,高真空规IKR270,低真空规TPR280；德国普发）3、极限真空：2x10-9Torr4、系统真空检漏漏率：≤5.0x10-8 Pa.l/S5、真空室：材料为无磁不锈钢，表面喷丸后电解处理；

内部尺寸：Ø100×H210（mm），二个CF35法兰（接规管和全金属角阀），二个CF100法兰（一个接CF100封接观察窗，一个接离子泵口过渡接管），一个CF16法兰（接放气阀），二个CF63 法兰（一个接CF63进口闸板阀，一个接进口磁力传递杆800mm）。6、样品库：可放置4个样品。7、磁力送样杆：1套。

二、制备室1、真空获得：1300L/S的SAES泵（意大利）+400L/S的离子泵（三井）+Hipace700全无油分子泵机组（德国普发，四个真空室共用）。2、真空测量：数显复合冷阴极规（真空计TPG262,高真空规IKR270,低真空规TPR280；德国普发）3、极限真空：2x10-10Torr4、系统真空检漏漏率：≤5.0x10-8 Pa.l/S5、真空室：材料为无磁不锈钢，表面喷丸后电解处理；内部尺寸：Ø200×H410（mm），三个CF35法兰（接规管、銫源、氧气源），一个CF35法兰（接全金属角阀），四个CF63法兰（一个接进口磁力传递400mm，一个CF63观察窗，二个CF63进口闸板阀），三个CF100法兰（接普通封接观察窗、加热炉、吸附泵口）；一个CF150法兰（接离子泵）；二个CF200法兰｛后端的CF200法兰上加一个CF35石英封接观察窗（透紫外线），二个CF16单心陶封高压电极（1000V）连接收集极；前端的CF200法兰加CF63过渡，接进口磁力传递杆｝。6、銫源：需要用户提供銫条，通过CF35法兰连接；四套。

氧气源管路：抽气管路一个三通+一套波纹管路 +一个过渡接头；氧气需通过管路输送到接近銫源的位置；氧气管路需要单独抽真空。7、氧源：具有一路充氧气气体管路（管路漏率＜10-6Pa.L/S），手动微调阀调节气体流量；8、样品台：加热体温度：800℃，可控可调；

三、存储室：1、真空获得：400L/S的SAES泵（意大利）+200L/S的离子泵（三井）+Hipace700全无油分子泵机组（德国普发，四个真空室共用）。2、真空测量：数显复合冷阴极规（真空计TPG262,高真空规IKR270,低真空规TPR280；德国普发）3、极限真空：2x10-11torr4、系统真空检漏漏率：≤5.0x10-8 Pa.l/S5、真空室： Ø150×H330（mm），二个CF35法兰（接规管和 CD-J35全金属角阀）,四个CF63法兰（接进口磁力传递800mm、进口磁力传递1200mm，进口CF63闸板阀、CF63盲板），一个CF100法兰（吸附泵口），二个CF150法兰（上端CF150法兰封接Φ100普通玻璃观察窗，下端CF150法兰接离子泵）。二个CF63--CF35过渡波纹管（用于连接磁力传递杆和进样室）。

6、样品库：可放置4个样品.7、磁力送样杆：2套

四、安装台架：优质方钢型材（50mmX50mmX4mm）焊接成，快卸围板表面喷塑处理；机台表面用不锈钢蒙皮装饰；四只脚轮，可固定，可移动；



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We design the gun cavity and do some simulations on the field distribution, based on KEK DC gun.



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Field distribution of the 500-kV gun

This is the field distribution in the gun cavity simulated by CST, the maximum field is at the edge of the cathode.

This is the field distribution nearby the support rod without the cathode ball by Poission. The result is the almost same as calculation result given by KEK



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Ceramic insulator breaking (punch-through problem due to the field emission from the surface of the support rod and the cathode ball).(1) to design the cavity and cathode ball and the electronic anode. Try to decrease the field gradient when the HV is fixed.(2) try to use the special material at those points of the maximum field. For example, Mo or Ni, try to decrease the electron number from these points due to the field emission(3) to use the guard-ring to block the electrons from the support rod and cathode surface and to protect the Ceramic insulator

Extreme high vacuum (<1E-10Pa) in the gun. Cathode lifetime depends on the vacuum. In order to operate the DC gun stable in a long term, we should

（1) the gun cavity and fringes would be made of special material to decrease outgassing rate. titanium or titanium alloy 。

（2) to apply the inseam welding art and sealed nipples to decrease the leak rate.

（3) Combination of NEG pumps and a bakeable pump to increase the pumping ability.



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1. An 1.3GHz active mode-locked laser oscillator (optical clock from pritel) is used to produce 12ps pulse at 1060nm wavelength.

2. A pulse compressor then compress laser pulses from 12ps to about 2ps for the pulse staking downstream.3. The insertion lose of the compressor is too high, so an optical amplifier has to be used after it.4. An high speed waveguide modulator can pick up one pulse from every ten pulses to decrease rep. rate into 130MHz

5. By two cascaded polarization maintenance optical amplifiers, the laser power can be up to 20w6. 1060nm laser is focused to an SHG crystal with I type match to get 530nm green light7. After transverse and longitudinal shaping, “beer-can” shaped pulses can be transmitted on the photocathode



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Key technologies on the drive laser system should be pre-researched

1. 1.3GHz active mode-locked laser oscillator, pulse rep. rate is 1.3GHz.

2. Two cascaded polarization maintenance fiber amplifiers, the laser power be amplified to 20W

3. 1060nm laser is focused on an SHG crystal with type1 match-mode to generate green light @530nm

4. Laser pulse shaping, including the transverse and longitudinal shaping. In the end,laser pulse with the beer-can shape transmit to the photocathode surface



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Cockcroft-Walton HV technology is mature technology, some companies in china can produce the HV power system. using LC filter circuit to suppress the ripple.

Requirements on HV power system:

1. Output HV 550kV、10mA, Operate at 500kV stably for a long time.

2. HV ripple is better than 1.0×10-4。



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1. ERL test facility is proposed in IHEP. The task at the first step is to build the photo-injector with 5MeV energy and 10mA average current.

2. We have done the preliminary design on the photo-injector, including DC gun injector and 217MHz VHF gun injector.We designed all components of the injector system and optimized the beam dynamics.

3. We focus our efforts on the photocathode DC gun. We have finished the design of all the subsystem of the gun: preparation system of the GaAs:Cs cathode, driving laser system, gun and HV system.

4. We are trying to get funding and begin to build the DC gun in the next year.

5. We hope to collaborate with the experienced Lab on the DC gun issues

Summary


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preliminary design on the 5 mev injector and 500 kv dc gun in ihep · 2013. 7. 28. · 1 yunlong...

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