Summary Minutes from the Meeting at KEK July 2‐3, 2012, of theInternational Advisory Committee of the 3‐GeV ERL Project.

Question 1 – Are the scope and strategies of the 3GeV‐ERL project including
the further upgrade of XFEL‐O satisfactory as the future light source inKEK?
The ERL, with the XFEL‐O, is a logical step in the development of next generation
accelerator‐based photon sources. It will have unprecedented characteristics,
and will be complementary to high‐gain FELs and ultimate storage rings. Going
far beyond present state‐of‐the‐art, and ERL will open up major new researchareas. The ERL is therefore an exceedingly strong and logical candidate as a
future light source at KEK, and is better than “satisfactory”.
KEK/JAEA with its advanced capability in accelerator physics and, specifically,
superconducting rf technology, is uniquely positioned worldwide for the successful
construction of an ERL. KEK can play a leading role in establishing the necessary
technology and extensive collaborations with international partners can beanticipated, within existing frameworks and/or within the recently proposed
International Institute for Future Accelerators.
The XFEL‐O, with a planned average flux of ~10^15 photons/second/meV has truly
revolutionary potential: to the best of the review committee's knowledge, it is notmatched by any device planned on a 10 or even 20 year time scale. This is anextremely exciting and un‐paralleled game‐changing instrument for nearly all areas
investigating dynamics ‐ electronic, atomic and perhaps even magnetic ‐ on timescales of ps or faster.

Question 2 – The Science Case for the 3GeV‐ERL project.
A. Is the scope of the science case of the 3GeV‐ERL reasonable and alsosatisfactory?
B. Is the effort to brush up the science case enough?
C. Further recommendation for this item
A. Yes. The IAC is of the opinion that the scientific case for a 3GeV‐ERL is matureand is solidly anchored in both the Japanese and the international scientificcommunity. The Conceptual Design Report provided to the IAC before the July
2‐3 meeting has an impressive expose of the breadth of novel scientificopportunities an ERL source offers. This was substantiated by the excellent
review of Dr. Adachi and the three equally excellent talks on more specializedtopics by Drs. Nakao, Amemiya and Ishii. The IAC takes note that PF was a co‐sponser of a series of six workshops held at Cornell in June 2011 providing acomprehensive coverage of future scientific directions with the next generationof coherent, high rep. rate, short‐pulse sources. The workshops were attended byclose to 500 participants.
B. As has been the case so far, the IAC recommends that PF/ERL‐team play anactive role in promoting the evolution of the scientific case with workshops,
symposia, etc.
C. The ERL team should continue to pursue further advanced capabilities, suchas sub‐femtosecond pulse generation via echo‐enhanced harmonic generation,and fold these into the scientific case.
Question 3 – Development for accelerator technologies
A. Is the technical development for the accelerator components for thecERL sufficient?
B. Is there anything to check the technical problem in cERL before
construction of the 3GeV‐ERL?
A. The IAC was very impressed by the advanced status and the rapid progress ofthe cERL project. The IAC commends the entire ERL team for these remarkableaccomplishments. The progress is consistent for all subsystems: high brightness
CW gun, high‐Q HOM–damped superconducting cavities, rf sources, 2K cryogenicsystem, and re‐circulating loop. The IAC noted that the achieved 526 keV for thegun is a world record. The cERL is well‐positioned to be completed as scheduledwith the first beam at the end of 2012.
B. The strategy to construct the cERL as a precursor to the 3GeV‐ERL is criticalsince the cERL has the main technology components required for the 3GeV‐ERL.
In addition to the needed improvements covered within the presentations, theIAC recommends attention focus on beam stability issues.
Question 4 – Construction of 3GeV‐ERL
A. Is the construction of the 3GeV.ERL feasible under the R&D planningof accelerator development?
B. Further recommendations for this item.
A. The IAC spent considerable time on the ”3GeV‐ERL construction plan”. It is
the understanding of the IAC that the cERL is expected to be operational/commissioned at the end of 2012 and that the experience from this endeavor
will be the basis for a design plan to be largely finalized in 2014. The IAC fully
supports this approach. The IAC stresses the importance that this plan must bescrutinized by outside review committees with appropriate technicalbackground.
A detailed list of topics was presented (e.g. during the talk by Prof. Kawata)
where it was expected that additional R&D would be required for either partial
or complete operation of the ERL. The IAC strongly recommends that this list be
prioritized with, if possible, some indication of the resources expected to benecessary for appropriate progress in each area. The IAC also fully supports thata continuous R&D effort of the gun/laser is necessary and in parallel with theERL construction, extending into the commissioning/operational phase .
The IAC finds the proposed construction time, with completion of the 3 GeV ERL
in 2021, is timely and feasible, given sufficient resources. Notably, based on theinformation provided in the talks, this will require additional support in both
manpower and funding, and should be discussed in detail with KEK management.
B. The IAC was presented with a possible layout of the ERL facility on the KEK
site. The IAC recommends that a careful study is done to make sure that thechosen layout is optimal, with particular care that there is enough space forfuture expansion.
The XFEL‐O requires major developments of x‐ray optics. The IAC recommends
that the ERL team initiates collaboration with Japanese and foreign universities
or institutions with expertise in this area. This will also impact x‐ray opticaldevelopment for general SR advancement/usage.

The Committee expresses its appreciation to the ERL‐team for providing it with theConceptual Design Report and copies of all presentation well ahead of the meeting.
The Committee wants to thank KEK/ERL management and staff for a well‐planned
meeting with a set of informative presentations and constructive discussions, andfor the great hospitality throughout the meeting. The efficient administrative staff
took exceptionally good care of all logistic manners.
Committee Members:

Dr. Alfred Baron (Riken SPring‐8)Prof. Masahiro Katoh (UVSOR)
Prof. Kwang‐Je Kim (The University of Chicago and APS/ANL)
Prof. Ingolf Lindau, Chair (SLAC/Stanford)
Prof. Jun‐ichiro Mizuki (Kwansei Gakuin Univ.)
Dr. Thomas Tschentscher (European XFEL), absent from meeting
Prof. Zhao Zhentang (Shanghai Institute of Applied Physics)

Stanford, July 7, 2012.
Ingolf Lindau (Chair, on behalf of the IAC)