1. Study on IFMIF Beam-Target Interface
Jing-Yu Tang, Zheng Yang, IHEP, China
P.A.Phi. Nghiem, Alban Mosnier, CEA-Saclay/IRFU, France
FCPPL-2011 Workshop, Jinan
April 7-9, 2011

2. Topics Introduction to IFMIF accelerators
Introduction to IHEP high power accelerators
Beam-target interface issues
Beam spot uniformization
Back-streaming neutrons
Collaboration

3. Introduction to IFMIF accelerator
IFMIF (International Fusion Material Irradiation Facility) is a sister project of ITER (International Thermonuclear Experimental Reactor), provides the most intense neutron source for material irradiation study
First phase - EVEDA (Engineering Validation Engineering Design Activity): 9MeV-125mA D+ CW beam
Second phase – IFMIF: two 40MeV-125mA D+ CW beams

4. IFMIF-EVEDA is studied and constructed in Europe, and to be installed in Japan.
The highest average current linac under development in the world, raises many challenges
Based on CW RFQ and superconducting HWR linac

6. CSNS high power proton accelerator
CSNS (China Spallation Neutron Source) is a high-power proton accelerator based multi-disciplinary facility for research, mainly relying on neutron scattering techniques.
Construction:
Site: Dongguan, Guangdong
IHEP and IOP
Phase I II
II’ or III
Beam power on target [kW]
100
200
500
Beam energy on target [GeV]
1.6
Ave. beam current [A] 63
125
315
Pulse repetition rate [Hz] 25
Protons per pulse [1013]
3.1
7.8
Linac energy [MeV] 80
132
250
Linac type
DTL
+SCL

7. China ADS high power proton accelerator
China is pursuing an ADS (Accelerator-Driven Subcritical System) program strongly, under CAS (IHEP, IMP, IPP and USTC)
Accelerator: 10mA, CW proton beam
RFQ+CH
RFQ+Spoke
2013
~5 MeV
2015
25~50 MeV
201X
50/150 MeV
~2022
0.6~1 GeV
~2032
1.2~1.5 GeV
5~10 MWt
100 MWt
≥1 GWt
Verification of two ways
Integration
Integral test
Phase II target
Phase III target
10 MeV
Phase I
R&D Facility
Phase II
Experiment Facility
Phase III
DEMO. Facility

8. Beam-target interface
There are four critical issues concerning the interface between a high-power beam and its irradiation target:
Spot uniformity to reduce the peak current density at the target
Beam window separating the vacuum for the accelerator and the target environment (e.g. helium atmosphere)
Back-streaming neutrons from the target, which are harmful to the accelerator devices
Beam monitoring in the radiation-hard region

9. Interface at IFMIF Irradiation spot Beam window
Beam footprint in rectangular shape: 20 cm (H) x 5 cm (V)
Current density across the flat top is uniform (±5%)
Current density: < 0.5 A/cm2 (for |x|>11 cm)
Beam window
No vacuum window
Backscattering neutrons
Bending (perhaps not sufficient, collimation)
Beam monitoring
Profile monitoring using residual gas
What kind of beam window is foreseen to be used at IFMIF? Vessel of the liquid lithium? I know that no vacuum window at EVEDA beam dump.

10. Beam spot uniformization
Nonlinear magnets are needed for the beam spot uniformization at target
More conventional: single octupole or pair of octupole and dodecapole for each plane (horizontal or vertical)
New concept-1: step-like field magnets, initially proposed for ESS and CSNS
New concept-2: simplified multipole magnets including different combinations of anti-symmetric second-order, third-order, fourth-order and fifth-order field magnets, recently proposed at IHEP

11. Preliminary studies at CEA-Saclay:
Using octupoles and dodecapoles for spot uniformization at IFMIF

12. Studies at IHEP:
Using step-like field magnets (SFM) for spot uniformization at CSNS

13. Step-like field magnet prototyping

14. Simplified high-order field magnets
Used for a flat good field region
Available for any order of anti-symmetric field or symmetric field
Right: simplified 3rd order field magnet (model and relative difference to theoretical distribution)
Work to be published

15. Tests with beam for spot uniformization
A test beam line using the ADS-RFQ is being set up for studies on both halo development and spot uniformization
NLM can be step-like field magnets or simplified high-order magnets

16. Simulation results at ADS RFQ beam test line:
Left: step-like field magnets; Right: simplified 2nd order and 4rd order magnets

17. Collaboration
Both IHEP and CEA-Saclay/IRFU are involved in developing high-power hadron accelerators. Both sides are much interested in collaboration in this domain.
Beam dynamics, superconducting RF system and other accelerator technologies, beam-target interface, simulation codes, etc.
As the first step of collaboration, we plan to investigate the beam-target interface problems together.
We also expect to establish collaboration on ADS accelerator between IHEP and IN2P3(IPN-Orsay) within the frame of FCPPL.

18. Thank you for attention!