Group photo during the PAC meeting at LAL, Orsay, France in April 2015. Image: ©CNRS/LAL, Dominique Longerias.
“April in Paris, chestnuts in blossom
Holiday tables under the trees
April in Paris, this is a feeling
That no one can ever reprise”
Thus run the lyrics of the famous song, composed by Vernon Duke in 1932. Indeed the first Programme Advisory Committee (PAC) meeting of the LCC era was held in idyllic weather in the French capital at the start of the week. Reviewers from all over the world, chaired by Norbert Holtkamp of SLAC National Accelerator Laboratory, gathered at LAL, Orsay to review the status of the LCC and progress since the completion of the Technical Design Report (TDR) in 2013.
Although the format of the review was fairly standard, the context was perhaps not. Many of the reviewers had previously taken part in similar exercises under the Global Design Effort (GDE). However, the general feeling of “a good job, well done” that swept the world’s funding agencies after the delivery of the TDR meant that almost all of the resources employed by the GDE were reassigned to other activities. The LCC, therefore, has a much reduced scope and ability to carry out R&D than had its predecessor organisation. Thus the latest PAC review was not faced with a long list of R&D activities to consider. Rather it was presented with an LCC effort that concentrates on facilitating the consideration currently going on in Japan as to whether Japan wishes to propose to host the ILC.
This isn’t to say that there was no technical content to consider – far from it. Indeed it is remarkable just how much progress has been made, given the effort available, since the LCC started operation under the direction of Lyn Evans. Lyn himself set the tone of the review with his introductory talk, in which he highlighted the main mission of the LCC as facilitating the decision-making process in Japan. This was reinforced by Sachio Komamiya (University of Tokyo), the chair of the Linear Collider Board (LCB), which gives the PAC its charge, when he summarised the status of the ILC inside Japan. He concentrated on the work of the review committees set up by the Japanese funding agency MEXT which are looking at both the technical aspects and costing of the TDR and the physics case and scientific “value for money” of the project. These should give interim reports at the end of this month; so far the discussions seem to have been very positive. The committee reviewing the physics case is almost exclusively from outside particle physics; indeed Sachio is the only particle physicist member. He also presented the current status of discussions with other governments and funding authorities. A one-sentence summary is that this is gaining momentum in the US but still needs work inside Europe.
Mike Harrison, associate director for the ILC in the Linear Collider Collaboration, summarised the technical work on the ILC that has taken place in the last two years. Some highlights are the demonstration of an ILC-specification cryomodule at Fermilab and the achievement of beam sizes and reproducibility at the ATF2 facility at KEK which approach those required for ILC, albeit at small beam currents. He also showed a slide from Jim Siegrist at the recent HEPAP meeting in the US which emphasised the advances being made in the performance of superconducting niobium cavities by techniques such as nitrogen doping and baking. Mike finished by looking at the change-control management process and the requests for modification of the baseline TDR design that are currently working their way through the system. The progress with the ILC superconducting acceleration system was further summarised by my Asian counterpart Akira Yamamoto, with emphasis on the basic science of the surface of niobium.
Undoubtedly the greatest progress on understanding the ILC has come from our sister project, the European XFEL currently under construction at DESY. The technology is virtually identical and more than 600 superconducting cavities have already been received at DESY, from where, after testing, they travel to Saclay to be assembled into cryomodules. Olivier Napoly (CEA-Saclay) showed the results from the cryomodule assembly and Nick Walker (DESY) summarised what we have learnt from the cavity tests. There is a wealth of information available as well as a great accumulation of expertise as to what are the critical areas in the production process. To summarise such an enormous amount of knowledge is difficult but basically the cavity performance is almost at that required for ILC while the basic techniques of building the cryostats are established. There is still work to be done in understanding the drop in performance between the vertical cavity tests and that once built into the cryostats but significant progress is being made.
As noted above, the LCC organisation sees its primary goal as facilitating a decision to host the ILC in Japan. One important aspect of this is the governance of an ILC Laboratory. I reported on the work of the committee I chaired, set up by the LCB, to revise and update the Project Implementation Planning (PIP) document published in advance of the TDR. Many of the chapters have been completely rewritten with new information from projects such as ITER and ESS as well as emphasising the requirements that follow if Japan does indeed become the host state. No doubt I shall write more about this in a future NewsLine when the final document is agreed by the LCB.
The final talk on Monday was by Jim Brau (University of Oregon), who summarised the discussions on running scenarios for the ILC. The day came to a close with a very pleasant buffet supper in the LAL coffee area in which the participants could enjoy the sunshine that they had missed during a long day of talks.
Steinar Stapnes, associate director for CLIC in the LCC, presented the status of CLIC and the plans leading up to the next European Strategy exercise, by when a project plan for staged implementation will be prepared, aiming at a decision on future energy-frontier projects in 2018-19. Hitoshi Yamamoto described the work of the LCC Physics and Detector Directorate, which he leads. As well as a broad summary of detector progress, details of which were left for Marcel Stanitzki (SiD) and Henri Videau (ILD) to amplify, he also discussed the physics prospects for circular electron-positron colliders which are currently being discussed both in Europe and China. The physics case for ILC was covered in a masterly summary by Christophe Grojean; gratifyingly, he concluded that the physics case for the ILC is stronger than ever. Finally Karsten Büßer summarised the work of the Infrastructure and Planning Group, chaired by Sakue Yamada. Much of this feeds into the PIP update that I referred to above.
The PAC, heroically missing their lunch, worked through the early afternoon to produce conclusions that were presented by Norbert Holtkamp. Since these are still preliminary and will be the subject of a written document it would not be appropriate, neither do I have the space, to go into detail here. In summary, the PAC recognised that in many ways the ILC was a project “on hold” waiting for a Japanese decision on hosting. As time goes on there is a clear danger that experts will leak away from the project, making a timely decision from Japan on the currently foreseen time scale of the greatest importance. The committee was extremely impressed by the progress both on the machine and particularly on the detectors given the very limited resources available.
To conclude, I return to the beginning. “April in Paris” was written for a Broadway musical entitled “Walk a Little Faster”. As we progress towards the ILC, we can take our cue from this.
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