Introduction to the effort on C-ADS accelerator physics and review charges Jingyu Tang For the Joint IHEP-IMP group on the C-ADS Accelerator Physics International Review Meeting on Accelerator Physics Design of C-ADS, September 19-20, 2011

Main topics Special features and design goals of the C-ADS linac Phased R&D and construction milestones Organization of the C-ADS accelerator physics Key parameters, physics schemes and technical schemes Charges to the review committee

Special features and design goals of the C- ADS linac Medium-energy, very high beam power, very high reliability, CW beam  RAMI principles  Superconducting structure as possible Reliability and availability much higher than actual accelerators in operations  Very strict on beam trips  Installed tolerance: over-design, redundancy, fault-tolerance  Local compensation method for key device failures ParticleProton Energy (GeV)1.5 Current (mA)10 Beam power (MW)15 Duty factor (%)100 Beam Loss (W/m)<1 Beam trips/year 1s 5m <25000 <2500 <25

Roadmap of C-ADS program RFQ + HWR RFQ + Spoke 2013 ~5 MeV ~50 MeV 201X 50/150 MeV ~ ~1 GeV ~ ~1.5 GeV 5~10 MW t 100 MW t ≥1 GW t Development of injectors Individual Integrations Integral testPhase II target/reactor Phase III target/reactor 10 MeV Phase I R&D Facility Phase II Experiment Facility Phase III DEMO. Facility

Main check-points for the C-ADS linac Phased development on C-ADS linac should follow the check-points  Phase 1 – first step (2013)  Accomplish two different schemes for the major part of the injector by IHEP and IMP: an RFQ + 5-MeV superconducting section, CW operation but no beam current requirement.  Phase 1 – second step (2015)  Accomplish two injectors by IHEP and IMP, and the main linac of 25 MeV, CW operation but no beam current requirement  Phase 1 – third step (2016)  Accomplish the linac of 50 MeV, CW and 10 mA beam (?)  Phase 2 (2022)  Accomplish the linac of not lower than 600 MeV, CW and 10 mA beam  Phase 3 (2032)  Accomplish the linac of GeV, CW and 10 mA beam

Organization of the C-ADS accelerator physics studies A joint IHEP-IMP group of the accelerator physics was formed in March This is important for the two labs collaborating on the project.  General design of the accelerator scheme  Interface definition  Better for organizing reviews  Mutual benefit from exchanging experience on design method, tool utilization etc. The joint group is also helpful for the training of young staff and students. (training by work, seminars, schools) Frequent exchanges, discussions by video meeting etc.

Resources for the C-ADS accelerator physics IHEP and IMP have allocated sizable resources for the C-ADS accelerator physics  9 staff: 6 from IHEP (5 full time), 3 from IMP (1 full time)  9 students: 5 from IHEP, 4 from IMP Non-official collaboration from USTC: on HEBT- target interface Lacking of experience  Most staff are very young and new comers in the high- intensity proton linac  Almost all the students have entered the field recently (less than one year).  Intensive training is absolutely necessary. Recently IMP began to send young guys to IHEP for training

Key design features Beam energy for phased C-ADS development  5 MeV (RFQ + one SC cryomodule)  50 MeV (injector + one Spoke section)  150 MeV (full spoke section, for injection into T/R)  600 MeV (minimum energy for spallation)  MeV RF frequency  RF frequency for the main linac has been determined to be 325/650 MHz (same as Project-X)  RF frequency for the injectors follows two options: one is with 325 MHz and the other with MHz. IHEP and IMP are developing the injector in different schemes in parallel.

Superconducting acceleration structures  For main linac, single-cell spoke cavities and 5-cell elliptical cavities  For Injector-I, IHEP is pursuing spoke cavities (half and three-half wavelength)  For Injector-II, IMP is pursing HWR or CH cavities De-rated performance, redundancy and compensation methods to increase the overall linac reliability  De-rated parameters for operating key elements  Two injectors (hot-spare)  Redundancy in RF sources, power supplies and controls  Compensation methods for cavity and focusing element failures

Warm transitions between cryomodules to facilitate quick replacement of failed cryomodules, beam loss collimation and beam diagnostics Less types of SC cavities  Solution 1: 3 spoke cavities, 2 elliptical cavities  Solution 2: 1 HWR cavity, 2 spoke cavities, 2 elliptical cavities Space-charge dominant regime?  With 325-MHz injector, tune depression about 0.75, close to the regime  With MHz injector, tune depression about 0.64 (main linac), inside the regime

Main linac Layout of the C-ADS linac ‘ Hot stand-by ’ Local compensation Two identical injectors on line, either with scheme injector-1 or with scheme injector-2

Strategy for the first step At IHEP, we have studied different lattice schemes for the injector-I, and proposed the following strategy for the first 5-MeV section by end 2013 (if one long cryomodule of <11 m is acceptable)  Just building a full-scale RFQ (3.2 MeV) and a short cryomodule housing six cavities (~5.5 m). It accelerates the beam of MeV in nominal operation voltage.  It will accelerate beam to 5 MeV with reduced cavity performance or one cavity not working  It will accelerate beam to 5 MeV with half nominal operation voltage but an increased synchronous phase (no current requirement at this stage) For Injector-II at IMP, similar strategy can apply

It is helpful to ease the development requirement in the first step (number of cavities, cryomodule, infrastructure etc ) In the future, the six cavities will be reused in the full length cryostat (12 cavities) by discarding the short one.

Overall commissioning strategy This needs to be studied in the future Just some thoughts listed here  For Phase I – first step (5 MeV, no current requirement): CW RF, low-current pulsed beam  verify technical development of the RFQ, low-beta SC cavities and cryomodule  For Phase I – second step (25 MeV, no current requirement): CW RF, high-current pulsed beam  verify technical development of the MEBT and long cryomodules, performance of RFQ at nominal operation, performance of low-beta SC cavities with long-pulse beam, main linac test with at least one injector, beam characterization, deciding on future injector scheme based on the R&D performance)

A question to the review committee  If we commission the SC linac with pulsed beam, there are two options: one is to operate the linac in pulsed mode, there might be a problem concerning Lorentz-detuning; the other is just to extract the beam from the ion source in pulsed mode by keeping CW RF.  Should we design the linac being able to work in both CW and pulsed mode?

Review charges Reviewing the physics design what have been presented by the C-ADS accelerator physics group. Evaluating the profoundness, entirety and quality of the work of the AP group. Judging if the actual physics design is at the least level sufficient to help the C-ADS managers to make the decision: either that we can pursue the design scheme and particularly provide inputs for hardware R&D or technical designs, or that very important changes in the design scheme must be taken before going into hardware development.

Helping in choosing the most appropriate design solution among the more-than-one solutions for different subjects proposed by the AP group, or even suggesting a different approach. Suggestions to the accelerator physics work in the near future and in a longer term. Comments on if the actual manpower allocated for the physics design is appropriate. Comments on the collaboration both international and domestic.

Suggestions to the C-ADS management how to best pursue the C-ADS R&D phase (or Phase 0). What about technology development? There may be some additional specific questions to the committee.