1. 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 , 2015

2. 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

3. 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

4. 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.

5. Typical On-axial Swap-out Injection Process

6. 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

7. 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.

8. Injection System Design

9. 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

10. 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)

11. 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

12. 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

13. 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

14. 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

15. 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

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

17. 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

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

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

20. 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.

21. 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.

22. 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

23. 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

24. 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

25. 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

26. Inductive Adder R&D for HEPS Strip-line Kicker
HEPS requirement:
Vp=±10~15kV into 50Ω，Tr/Tf<5ns，Ttop=5-12ns
MOSFETs: DE N12A (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 DE N12A）

27. 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)

28. DSRD PFL Modulator Study

29. 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

30. 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 /