1. Comments to the Report of the Community Review of EIC Accelerator R&D for the Office of Nuclear Physics, February 13, 2017 (60 pages) By
Haipeng Wang, Jiquan Guo, Shaoheng Wang, Frank Marhauser
In the absent of Robert Rimmer and Jean Delayen
JLEIC Accelerator R&D Meeting, Feb. 23, 2017

2. Bunched-beam cooling of the hadron beams in the collider rings
Bunched-beam cooling of the hadron beams in the collider rings. The coolers will all require high average current energy-recovery linacs.
The JLAB design requires a high-average-current magnetized beam source. They are
proposing a novel multi-turn accumulator ring to “recycle” the ERL beam, which to date has not been tested. The alternate approach requires a much higher average current magnetized source.
Test harmonic RF kicker with recirculated beam is key technology demonstration for CCR-ERL design
Crab cavities with large integrated shearing voltages. Given the fact that these cavities have not been demonstrated in a hadron machine, it is important to study an alternative option for an interaction region design with bent electron beams and without the use of crab cavities to evaluate methods to address synchrotron light inside the detector and the need for synchrotron light absorbers to minimize the background inside the experiment.
Would like Slava’s comment on his recent this week to remove/replace the crab cavity option. Difference of global crabbing, dispersion change and Slava’s suggestion? How are those alternative colliding schemes to avoid the head-on beamstrahlung induced luminosity loss which was original Palmer’s proposal for the crab cavity?
The panel identified the following technologies and/or design concepts that
present technical risks common to all concepts and that should be demonstrated:
• Crab cavity operation in a hadron ring
• High current single-pass ERL for hadron cooling
First crab cavity test with proton beam will be at LHC-HLU at CERN
We have changed our baseline cooling into CCR, which high current single-pass ERL is opted out.

3. High power fast kickers for high bandwidth (2ns bunch spacing) feedback,
This is a broadband strip-line type kicker like SLAC used for PEP-II and BNL used for RHIC stochastic cooling. For the JLEIC proton ring, we have not considered and designed them yet
Integrated magnetized beam/kicker circulation test using the existing ERL infrastructure
Current Injector/FEL/SRF/CASA team is working on this approach.
Operate the JLAB Continuous Electron Beam Accelerator Facility (CEBAF) in the JLEIC injector mode
Jiquan’s LDRD 2015 proposal was not funded, not in LDRD scope? New LDRD needed? Or new funding from operation or no new funding needed? Hardware change is minimum for the Feed Forward control to minimize the beam loading/RF voltage droop for C50/C100 cryomodules.

4. See above comments
SRF systems for ERL, Ion Ring and Crab are all high current SRF cavities and cryomodules
It is what we doing now and next step for the harmonic RF kicker system to be tested at the UITF at 499MHz.
Whose proposal?

5. Bob’s proposal, long term goal to reduce SRF cryomodule cost and for different SRF projects
SRF is the part of CCR-ERL cooler and EIC rings R&D
We (SRF at JLab) are not part of USLARP (but as contractor) , as we know CERN wants to do the crab cavity tests (DQW and RFD, 400MHz crab cavities) with beam at SPS in 2018.

6. See comments above, not sure that beam loading compensation scheme proposed by Jiquan has been fully demonstrated by presenters.
Would like to work with Cornell and BNL teams on the electron cooling experiments?
Fully agree with
IMP experiment is non-coasting or long pulsed beam but electron bunch length is comparable to the ion bunch length.
Need to go to higher ion energy, bunched e-beam cooling experiment like at BNL or COSY?

7. Agree. CASA/ODU’s tasks.
Who is doing this simulation at ODU?
Test 499/476MHz crab cavities (DQW or RFD) at LERF+CCR facility with high beam current of 3A? BNL is the best US based high energy, high current proton machine. Proposal?

8. Crab cavity beam test should be also performed at SPS
Crab cavity beam test should be also performed at SPS? Beam kicking/crabbing at LERF is not desired?
For it! Last bullet is the problem for alternative (non-crabbing) solution, need to be studied.

9. Our RF/SRF exports can work on this feedback on both strip-line kicker and high R/Q
but low Qload device, HOM damping scheme and suitable RF power source to drive them.

10. CCR-ERL optic and careful matching design is required
CCR-ERL optic and careful matching design is required. Our CASA/FEL team is working on this.
New LDRD proposal?
Test plan and hardware/software modification needed to be identified by Operation/Engineering/SRF teams.

11. It is top-off for electron polarization loss and stack-up mode for injection operation. The life time of polarization has been considered for this injection scheme.
That should be half ring up, half ring down polarization scheme for the e-ring. It is not clear to us what the risk is for the top-off from the reviewer point of view. Fanglei’s task
Yes.

12. Has ODU studied that or JLab should be responsible?

13. We are doing that but study results were not presented to this DOE review.
We are not sure about truly benefit of nitrogen doping technique on the ERL, since high
loaded Q SRF cavity operation with nearly no beam loading and microphonics is still a problem for the stability control. Dynamic loss reduction in the SRF efficiency on the Q0 is nearly neglectable comparing to the beam power to SRF efficiency particularly when ERL requires relative low voltage but high current (~100MeV).

14. We need to kick off the last bullet item’s effort
We need to kick off the last bullet item’s effort. That means TW, stripline structure? RF source, feedthrough, cooling are bottle necks?
No comment, they are our own proposals.