CALICE's Semi-Digital Hadronic Calorimeter prototype during April 2012 test beam at CERN. Image: IPNL

For the first time, a large-scale calorimeter prototype for the ILC, fully equipped with embedded power-pulsed electronics, successfully passed a test beam at CERN a few weeks ago. A prototype of more than one cubic metre in size of CALICE’s Semi-Digital Hadronic Calorimeter successfully recorded and tracked 1 million particles from CERN’s SPS accelerator beam (muons and pions). It was equipped with 48 chambers of glass resistive plate chambers (GRPC) and two Micro Mesh gaseous structure (MICROMEGAS). This module is pretty close to what a future ILC hadronic calorimeter could look like, totalling 460 000 electronic channels. Thanks to power pulsing, the detector front-end electronics was intermittently disabled and enabled, following the beam cycle. The SDHCAL team involved in the construction and test of this module are based in France (IPNL in Lyon, LAPP in Annecy, LAL in Orsay and LLR in Palaiseau), Spain (CIEMAT in Madrid) and the universities of Louvain and Ghent in Belgium.

Lowering power is key to reduce the detectors’ power budget of course, but also to reduce heat dissipation in the sub-detectors. It is also a key issue for particle physicists to solve to design the next generation of collider experiments.
Learn more about power pulsing in ILC NewsLine

100-GeV particle tracks recorded in CALICE's Semi-Digital Hadronic Calorimeter prototype during the April 2012 test beam at CERN. Image: IPNL

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IDAG at work during AFCA-KILC12 meeting in Daegu, Korea. Images: KEK/N. Kobayashi

During the past five years the physics and detector community has made much progress for establishing capable detector designs for the ILC. These achievements are to be summarised in the Detailed Baseline Design report (DBD) by the end of this year. The DBD will make a solid milestone, marking the end of the Letter-of-Intent period and the point for the community to proceed towards the next stage. We consider it a very important task to complete the DBD, and plans started already in 2010. As I wrote in January, discussions for a precise and detailed planning of the DBD started by the DBD format working group last year. The working group worked out basic structure of the volumes and a schedule towards completion. The minutes can be obtained in our web page.

The first step in the schedule was the preview of the planned outline of each chapter of the detector volume by the International Detector Advisory Group (IDAG). The detector groups prepared their plans of detector chapters last March, and they were handed to IDAG for advice together with the content of the introductory chapter. IDAG met during the ACFA KILC12 workshop in Daegu, Korea, last month. IDAG discussed with the management and the two detector groups SiD and ILD separately. It also heard from the software common task group about the status of the new simulations for 1-TeV benchmark reactions which are under way for the DBD, as well as from Michael Peskin about the studies for the physics volume.

IDAG gave me some recommendations in order to improve the content and style of the DBD and to make the drafting work smooth. They include points that help clarify the aim of DBD and make it more comprehensive. Also there were technically useful suggestions. I appreciate all the suggestions and adopt many of them since they strengthen our effort on DBD. I describe below some important points, backed up also by IDAG, which are meaningful to be known by the community.

First, IDAG confirmed that all contributors shared the basic stance that the expected audience of the document is high-energy physicists. We have been discussing the character of DBD with the concept groups for some time and agreed that the document should contain detailed enough information to convince our colleagues in the nearby fields about the feasibility and the capability of the designed detectors and about the clear discussions of physics reach. When the DBD is finished, however, it will also be desirable to address it towards wider communities including funding agencies. This will be made in collaboration with that of Global Design Effort by making separate volumes of an executive summary and an outreach document of both the Technical Design Report and the DBD combined.

The detector volume will have an introductory chapter, a common issue chapter and the two detector chapters. As suggested by IDAG, a common issue chapter will be made, in which common items will be moved from the introductory chapter and from each detector chapter. With the common issue chapter, the DBD can be organised in a clearer form, reducing duplications. Now detailed discussions are being continued by the DBD format working group on how to allocate the topics in order to make for smooth reading and comprehensive coverage.

An important recommendation about the common chapter was made regarding future R&D. It is always true that detectors can be improved as new technologies or studies develop. So the concept groups wish to continue further R&D, knowing where possible improvements can be expected. IDAG suggested a solution, which was the same as we had planned, that such future activities be placed in the common chapter, not in each detector chapter, so that we don’t give the impression that we are not ready. The detector part needs to present that capable detector systems can be realised based on the achieved technologies.

Taking the IDAG suggestion that the introduction be written earlier so that the detector authors know what has already been written in the introduction, we try to fix the contents and authors of the introductory and common issue chapters as soon as possible.

There were recommendations concerning the simulations. One of them is to put a summary of the existing simulation studies for 500-GeV reactions before presenting new benchmarks at 1 TeV. It is an important point in order not to confuse the readers. While the detector groups are now working in full swing to complete the new benchmarks, we should not forget that the primary focus of the TDR/DBD will be on achieving a robust design for 500-GeV physics and that a number of benchmarks were studied already for the Letters of Intent. This point was transmitted to the two detector groups.

The format working group will meet soon to finalise the plan so that we can go ahead soon with drafting. We will also consider making a short summary chapter after the individual detector chapters to bring a clear message to the readers. We wish to complete the DBD by stating in the summary chapter that the DBD describes the status of the ILC detector studies of the design groups, demonstrating that with the technology in hand we can conclude that the two baselines are feasible and capable of achieving the physics goals of the ILC, and that future work will now move us closer to realisation of these detector concepts.

Trân Thanh Vân celebrating at dinner with friends and colleagues following receiving the AIP Tate Medal at the APS 2011 Prize and Award Ceremony

I was thrilled to learn that the American Institute of Physics had awarded the Tate Medal for 2011 to Jean Trân Thanh Vân. Tran epitomises global science, and both physics (especially high-energy physics) and his native country of Vietnam are greatly indebted to him for his dedication to bringing leading physicists from around the world together, even when political realities created major obstacles. He was honoured at the annual award ceremony of the American Physical Society during their April meeting in Atlanta. I delivered my APS Past-President address in the same session, during which the 2011 APS Prize winners were also honoured.

The John Torrence Tate Medal for International Leadership in Physics is given every two years by the American Institute of Physics. The 2011 medal was awarded “in recognition of Trân Thanh Vân’s role spanning more than four decades in bringing together the community of physicists across national and cultural borders through the Rencontres de Moriond and Rencontres de Blois, and for his tireless efforts to build a modern scientific community in Vietnam.”

Yours truly, 2011 APS President and ILC Global Design Effort Director, caught wearing a tie for his Past-President address at the APS awards ceremony

As described in the CERN Courier:

In 1965, Jean Trân Thanh Vân, a young researcher at Orsay, decided to organise an unusual scientific meeting for January 1966. The subject itself – electromagnetic interactions – was not particularly unusual, but the organisation was. The meeting was held in the French Alps in a group of chalets, with no catering help or assistance, few of the visual aids one associates with such meetings and, most importantly, without any telephone contact with the outside world (…) This was not a conference or a school, but a gathering (“rencontre”) of minds. The name of what became a series of meetings reflects this original motivation.

These meetings have became an important centrepiece for high-energy physicists, being unique in that they are attended by young and established researchers and in that they have the singular distinction of being a “winter meeting” where important new results are presented.

Jean Trân Thanh Vân was born in Dong Hoi, Vietnam, just north of the 17^th parallel where the country was divided in 1954. He grew up in war-torn Vietnam, and as a thirteen-year-old left his family to study in Hué. Then, at the age of 17, he left Vietnam to attend university in France. But his identification always remained closely linked to Vietnam.

Map of Vietnam showing the location (Qui Nhon) of the International Center of Interdisciplinary Science Education, which is under construction.

Following the end of the Vietnam war and the opening of Vietnam, Trân organised the first “Rencontres du Vietnam” to renew contacts between the Vietnamese scientific community and scientists from the rest of the world. I had the privilege of going to Vietnam in 1995 to participate in one of the first meetings. Following the meeting, Trân took us on a tour of Vietnam. Most memorable was our visit to a local orphanage. It opened our eyes to a completely different side of Trân and his wife. In 1970, they had founded the association “Aide à l’Enfance du Vietnam” to help Vietnamese orphans, and following the end of the war, they were instrumental in creating several centres for orphaned or homeless children. The orphanage we visited with Trân was impressive, filling a great need in rebuilding a country destroyed by years of war.

In recent years, Trân has dedicated himself to creating an important new international interdisciplinary centre in the heart of Vietnam, a crossroads between north and south, on an area of 20 hectares at the edge of the East Sea. The International Center of Interdisciplinary Science Education (ICISE) is aimed at young research scientists and engineers from different fields, exchanging ideas and experiences, in an atmosphere to develop their knowledge and themselves, much in the spirit of Trân’s “rencontres.”

An architect’s rendering of ICISE

The ICISE facilities are under construction, with construction completion and a planned first conference in July 2013. Trân has invited me to participate in this inaugural event and I very much hope to go back to Vietnam to do so,  just one month after we formally submit our ILC Technical Design Report to ICFA.

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A heavy-duty crane on the surface will transport the assembled detector slices to the hall below. Graphic: Marco Oriunno

Sometimes big things have to move in the way of small things to find exciting things. The ILC detectors, for example. True to the scientific principle of reproducibility of results, two detectors, ILD and SiD, will one day record what happens when electrons and positrons collide so that one can verify (or not) what the other has observed, using different detection technologies. However, they will never be able to do this simultaneously as there will be only one interaction point. The detectors will have to move into and out of the beam in as short a time as possible for maximum data harvest, and this caused detector designers, machine experts and the guys who know all about shifting rock no end of headache. Now they have found a solution that addresses all problems (at least for an ILC that is not built in a mountainous region).

The final design for the non-mountain hall for the detectors is shaped like a Z. The downstroke, which actually is at right angles to the side bits, is where the beams come in, and the side bits are the garages for the detectors when they are not in use. Though rather compact compared to the LHC’s giant ATLAS detector, both ILD and SiD are heavyweights, and with dimensions up to 16 metres in length and up to 15,000 tonnes on the scales, they are not easily pulled around. The total surface area of the hall, therefore, also measures over 3300 square metres. This allows not only for smooth operation, but also for easier assembly and maintenance.

Assembly is the main argument for the final choice of shafts that are needed for the ILC’s collision point. There will be one big shaft, 18 metres in diameter, right above the central part of the Z for the lowering of the giant detector slices, magnet coils and endcaps. Like the CMS detector at CERN, the two ILC detectors will be assembled on the surface and then lowered underground in complete slices. Two smaller shafts – nine and ten metres in diameter – give access from above to the two garages for detector maintenance, and another two are for people only so that they can get down and up easily and also have an escape route in case of an evacuation.

Spot the Z shape – one detector in parking position, one taking data. The non-mountainous detector hall for the ILC could look like this. Graphic: Marco Oriunno

Now obviously things will not be as easy as they may sound here. “We faced the problem of how to make both detectors fit the space between the two tunnels. And it’s the first time in history that two detectors share one interaction space in a push-pull-configuration,” says Marco Oriunno of SLAC, a member of the common task group on machine-detector interface and responsible for the impressive 3-D graphics of the area.

How do you move a 15,000-tonne object from a garage into the beam and back some 15 times a year? How do you make sure none of the high-tech, mega-precise parts move during the transport? How do you keep the magnets cool? The answer is: concrete slabs that serve as platforms for the detectors and will be moved by either airpads or rollers, and flexible cryogenic lines that move with the moving detector. A set of compressors on the surface makes sure that enough coolant is around while two cold boxes, one for each detector, will be installed underground. The lines extend from the garage to the interaction point. And the detectors adapted their configurations to each other so that both reach the beampipe shielding that sticks out at both sides of the central hall. Both also had to be self-shielding with respect to ionising radiation and magnetic fields for hall safety.

The shielding around the beampipe and the detectors’ self-shielding material are the only protective screens needed for the hall design. Maintenance on one detector will be possible underground while the other is busy taking data. The group also thought about how to organise beam commissioning. Before you start colliding particles, the machine operators have to take a series of important steps to truly understand and control their machine. A stray beam can cause great damage in a sensitive detector, so commissioning will not happen with a detector in place. Instead, walls of shielding blocks will be erected around the beam pipe so that work can continue on both the assembly of the detectors and the commissioning of the accelerator.

All this will be very different if the ILC is built under a mountain range. Shafts will not be vertical, for example, and the transport of the detector parts will be different. The design of the hall for these conditions is still a work in progress. Similarly, a civil engineering company is currently working on detailed studies of what can be expected of the non-mountainous geology when five shafts of different diameters are dug within relatively close distance to each other, and a detailed design of the moving platforms. Stay tuned for future info!

The push-pull concept as illustrated from the CERN ARUP report, considering the scheme for both CLIC and ILC

Since the inception of the ILC design effort, we have been developing the concepts for detectors to do the science as an integral part of our work. The interactions between the accelerator and the detectors are complex and demanding. For that reason, we have a group of accelerator and detector experts working together on machine-detector interface (MDI) issues. The ILC physics programme is based on building two complementary detectors that will share beam time. The value of having two detectors with different designs, technologies, collaborations and emphasis has proven to be a very effective way to exploit the science, as evidenced through three generations of colliders.

The push-pull interaction region layout from the US study, including surface support buildings

In the ILC Reference Design Report (RDR), chapter 8 of the detector volume very effectively outlines the arguments for having two detectors. To quote the introduction to that chapter: “The ILC’s scientific productivity will be optimised with two complementary detectors operated by independent international collaborations, time-sharing the luminosity. This will ensure the greatest yield of science, guarantee that discoveries can be confirmed and precision results can be cross-checked, provide the efficiency of operations, reliability, and insurance against mishap demanded for a project of this magnitude, and enable the broadest support and participation in the ILC’s scientific programme.” The arguments for planning for two detectors are further discussed in the chapter.

However, in carrying out the early design work, it soon became apparent that designing two independent beam lines that alternately share the beam would be an expensive proposition. The problem is that the beam delivery system for the ILC is in itself a long, complex and demanding system and therefore the cost of building two such systems was forbidding. As a result, in the RDR, we proposed using a push-pull concept to cost-effectively share the beam between two detectors. Previous detectors have been built such that they can be moved on and off the beamline for servicing and upgrades, but the demands were far less than for the ILC, where we want to be able to change between the detectors on relatively short time scales and with little down time. At the time of the RDR, we were able to determine that there appeared to be no show stoppers in this scheme for the RDR, but were not able to develop a design that could accommodate the differences between detectors and meet the other ambitious requirements.

A study of the concrete slab deformation under the detectors in the Japanese interaction region study

For the Technical Design Report, we undertook to carry out engineering designs, and for rather different sites. Now we have completed concepts to accommodate two detectors on a common platform, and have defined access and staging areas and to meet the other demanding technical requirements. It is also interesting that the Compact Linear Collider (CLIC) Study has adopted the push-pull system as well, with some specific differences to meet their more severe requirements for the stability of the final focus.

The CERN ARUP (a civil engineering consultant company) study concluded that the displacement limits of plus or minus 2 millimetres can be achieved by moving ILD on a 2.2-metre slab and SiD on a 3.8-metre slab, both with pads or rollers. They recommend future work on the movement system and an evaluation of the slab final positioning systems. Their study of the overall cavern performance under load in the CERN geology is somewhat marginal and depends on the detailed geology, in situ stresses and the construction sequence.

We are now reviewing the facility costs for the ILC push-pull designs, in order to ensure that we maintain the same cost consciousness for these facilities as we are for the rest of the ILC complex. Overall, however, we have established the reality of employing a push-pull system for ILC (and CLIC) and have identified the issues needing further study.

Learn more about the relationship between vacuum and “virtual” particles, the Higgs boson, supersymmetry and dark energy

Vic Kuchler, Fermilab, Americas Conventional Facilities Leader

The fourth Baseline Technical Review, held at CERN on 22 and 23 March, focused on conventional facilities and siting. All significant changes to the 2007 Reference Design Report (RDR) baseline were reviewed and evaluated for impacts on performance, cost and related systems. This was the last of the formal reviews of the Technical Design Report baseline, so the main activity now officially moves to producing the TDR by the end of 2012. Some further changes may still be incorporated as costing information becomes available or because of other new considerations over the coming months. However, we now consider the TDR baseline as established. The main task now is now to produce the report.

John Osborne, European Conventional Facilities Leader

There has been a set of changes to the RDR baseline, many of which have impacts on the conventional facilities. For example, we have changed to a single excavated tunnel for all sites, changing the tunnelling requirements; the electrical and mechanical loads are changed; the damping rings have been reduced in size, reducing the amount of tunnel required; the interaction region configurations and requirements are better defined; and a detector platform and moving system has been defined. Other systems have been refined and the better information is being used for the TDR costing.

Atsushi Enomoto, KEK, Asian Conventional Facilities Leader

One change that became obvious sitting through these conventional facility TDR reviews is how the design and issues have become more refined and the ways in which the detailed solutions are site-dependent. At the time of the RDR, we expected to see differences between sites and, for that reason, we asked and received a sample site from each region (Europe, Asia and the Americas). But in fact, at that time our knowledge of technical details and sites was limited, so we presented one design that would be used in any of the three sites. For the TDR design, many technical features are site-dependent. That means both the technical solutions (for example, distribution of high-level radiofrequency (RF) power), and the tunnelling and other solutions are site-dependent, even the shape of the underground tunnels. This leaves us grappling with the dilemma of how to present the multiple schemes we have studied. I will discuss this issue further, as we decide how to best handle these variations in the design in the TDR.

The conventional facility designs as presented for each region are considerably more detailed, especially regarding the mechanical, electrical and safety systems. A very productive pre-meeting was held on 21 March, reviewing with industrial consultants the detailed electrical and mechanical systems, and taking advantage of the expertise and experience that exists at CERN. Representatives from the Asian region presented mechanical and electrical designs that have been developed using the Asian region high-level RF system that are suitable for a mountain site in Japan. Representatives from the Americas region presented mechanical and electrical designs that have been developed for the klystron cluster RF system for the Americas sample site.

In addition to the changes and refinements discussed above, there is a much better understanding of the interaction region and of how to compatibly incorporate the two detector groups’ “Letters of Intent” in a push-pull scheme to enable alternating which detector is on the beamline. I will address this whole region and the present concept and issues in a separate column.