Injection System and Hardware Design For The HEPS R&D Jinhui Chen Power Supply Group, Accelerator Research Center, IHEP, CAS, Beijing, China LER2015, ESRF, September 15-17, 2015 www.ihep.ac.cn

Outline Introduce of HEPS Physics Design LER top-up injection scheme review Conception design of HEPS injection system Strip-line kicker design for HEPS on-axial swap-out injection Fast pulser design for HEPS injection strip-line kicker Potential technologies for ns fast pulser MOSFET-based Inductive Adder R&D DSRD-based PFL modulator R&D

High Energy Photon Source (HEPS) A future project in Beijing ,China before 2022 6GeV/60pm·rad/1296m LER Similar to APS-U　 Parameters Unit HEPS APS-U Lattice - 7BA Beam Energy GeV 6 Beam Current mA 200 Horizontal Emmitance pm·rad 60 65 RF Frequency MHz 500 352 Circumference of Storage Ring m 1296 1104 Number of Sections 48 40 Bucket Spacing ns 2 2.841 Total Number of Buckets 2160 Number of Injected Bunch(in Single Bunch Filling Mode) 432 (1/5) 324(1/4) Minimum Bunch Spacing 10 11.36 Length of Straight Section for Injection & Extraction 6×2 5.8×2

LER Top-up Injection Scheme Review Top-up injection schemes for low emittance rings: Off-axial injection (need larger DA) Pulsed local bump injection Pulsed multi-pole magnet injection On-axial injection (for smaller DA) Transverse swap-out injection Longitudinal injection The HEPS, as a LER with small dynamic aperture , will take on-axial swap-out injection scheme.

Typical On-axial Swap-out Injection Process

Conception Design of HEPS Injection System Recycling Scheme for on-axial swap-out injection Dumping Scheme for on-axial swap-out injection 1296m, 6GeV, 60pmrad Storage Ring

Injection & Extraction Section Layout 7BA Curved Section Injection & Extraction respective in two 6m long straight sections Vertical on-axial swap-out injection by 2 sets of strip-line kicker Lambertson Septum with horizontal mounted is to deflect injection beam by θH in horizontal. Strip-line kickers with parallel electrodes vertical alignment is to deflect injection beam by θV in Vertical.

Injection System Design

Strip-line kicker Design Injection beam position at septum outlet Length of drift straight section Electrode distance of strip-line kicker Kick angle θV ≥ 3mrad (1mrad/m) Distance of strip-line electrodes:ｄ≥ 10mm Allow first kicker shift in vertical offset: 1~2mm Add another strip-line kicker with tapered transition electrodes; It’s good to transit to standard vaccum pipe (Di=20mm) smoothly, lower beam coupling impedance Vertical Offset scheme Tapered Strip-line kicker scheme

Strip-line kicker Design Total kicker angle: θ=3mrad E=6GeV, d=10mm, g=1 =>U*L>90kV∙m Total strip-line kicker electrode length L=3m =>U>30kV(or ±15kV)

Strip-line kicker Design Minimum bunch spacing τ=10ns Strip-line kicker electrode length l<1.5m => l= 0.75m (4 strip-line kickers L=4*l= 3m) Pulse Width tp <15ns, Flat-top ttop >5ns, Rise/fall Time tr/tf <5ns

Strip-line kicker Design Two bunch-filling modes to be considered Single bunch mode (1 bunch/5 buckets, 432 bunches) 4-bunch train mode (4 bunches/8 buckets, 1080 bunches/270 trains) Single bunch mode 4-bunch train mode

Strip-line kicker Design Strip-line kicker electrode cross-section geometry 30mm strip-line Dual strip-lines TESLA-DR strip-line kicker KEK ATF-SR strip-line kicker 54.8mm 9mm INFN DAΦNE-SR strip-line kicker ALS-U SR strip-line kicker APS-U SR strip-line kicker

Strip-line kicker Design Be to design 2 kinds of strip-line kickers “D” type electrodes in an ellipse cavity (like APS-U design) Close slim electrodes: d<10mm “D” electrodes have better uniform field and mechanical strength than “C” type Sleek geometry is good to improve local E-field Vane design is to decouple 2 close strip-lines Longitudinal tapered electrodes (like DAΦNE or ALS-U) Be good to lower beam coupling impedance Larger aperture for injection beam More detail design is on going Tapered Strip-line kicker scheme ALS-U APS-U

Strip-line kicker Pulser Design The potential technologies for ns-fast pulser: RF-MOSFET based inductive adder RF-MOSFET based transmission line adder RF-MOSFET based Marx generator RF-MOFSET series stacking Co-axial magnetic switch compressor (shock wave transmission line) DSRD based PFL modulator Other switch: FID , SOS

Strip-line kicker Pulser Design Scheme 1 for HEPS: inductive adder Inductive adder topology Inductive adder structure

Topology of inductive adder It is a most simplest transformer series stacking topology for fast pulse applications. For ideal 1:1 transformer: Vout= N*Vchg, , Ip = Is The whole transformer stack can be seen as a fraction transformer with turn rate: Tp:Ts=(1/N):1=1:N Simplified Schematic of Adder Circuit

Equivalent circuit for single stage of adder Switch off mode Switch on mode UL UC (If Ls’ is small enough)

Topology study by PSPICE 10-stage inductive adder schematics in PSPICE

Pros & cons to the inductive adder All solid-state technology, long life time, low jitter and time drift Easy to adjust pulse width for hard solid-state ON/OFF switch Easy to get a long rectangle pulse Do not need HV charge PS and HV pulse Capacitor bank The coaxial transformer provide a HV isolation between primary and secondary. HV is confined to within the coaxial structure. Easy to change the polarity of pulsed source. Do not need floating driver and isolated PS for primary switching circuits by taking advantage of ground planes. The pulse power ground and the drive circuit ground have a common point at the switch source lead but otherwise do not share common current paths thereby reducing switching transients being coupled into the low level gate drive circuits The each stage is relative independent so one failure stage does not affect the whole inductive adder operation.

Pros & cons to the inductive adder For 15kV or higher application, the volume of inductive adder should be large; the number of MOSFET and its driver should be great. Increase in stages of inductive adder should lead to slow down front edge of output pulse because of transmission line effect. Structure of inductive adder is complex.

Inductive Adder R&D in IHEP We have some experiences from R&D on ILC-DR kicker pulser, from 2009 to 2011 2-stage inductive adder 10-stage inductive adder

10-stage inductive adder test result Conditions：U=610V，PRF=1kHz，RL=50Ω，30dB attenuation Result： Front edge of pulse(10%-90%）=2.58ns Width of pulse(FWHM) ≈10ns Pulse amplitude ≈4kV

Single stage into 7.7 Ω @ 1MHz Conditions：U=250V，PRF=1MHz，RL=7.7Ω，10X attenuation Result： Front edge of pulse(10%-90%）=1.9ns Width of pulse(FWHM) ≈10ns PRF=1MHz

Single stage into 4 Ω Conditions：U=220V，PRF=1kHz，RL=4Ω，10X attenuation Result： Front edge of pulse(10%-90%）=2.15ns, Rear edge(10%-90%)=2.8ns Width of pulse(FWHM) ≈8.2ns PRF=1kHz

Inductive Adder R&D for HEPS Strip-line Kicker HEPS requirement: Vp=±10~15kV into 50Ω，Tr/Tf<5ns，Ttop=5-12ns MOSFETs: 150-180 DE375-102N12A (or IXZ4DF12N100)，25-30 stages, 6 MOSFETs in parallel each stage, Vout >700V for each stage。 25-stage inductive adder simulation(Vout by one stage with 6x25 DE375-102N12A）

Strip-line kicker Pulser Design Scheme 2 for HEPS: DSRD based PFL modulator Drift Step Recovery Diode(DSRD）: Special semiconductor diode, a new technology for us Opening in sub-ns Got a sample: K005 from the vender in china(i p≥300A/ Vp=15kV) (A. Benwell1 , SLAC, A 5KV, 3MHz Solid-state Modulator Based on theDSRD Switch for an Ultra-fast Beam Kicker)

DSRD PFL Modulator Study

DSRD PFL Modulator R&D for HEPS A 6-stage inductive adder for DSRD pumper circuit 4 DSRDs(2 parallel, 2 series) switching 300A into 50 Ω 1.5m long PFL(TL1) for pw=15ns and 2m long for 20ns

Thanks！ 联系方式 北京市 / 石景山区 / 玉泉路19号乙院 高能物理研究所 / 加速器中心5号厅 / 100049