At 3 p.m. on Monday, 12 November, Frédérick Bordry, Director for Accelerators and technology, switched off Linac2 for the last time. The accelerator will not be restarted after Long Shutdown 2 and has passed the baton to Linac4, which will take over as the first accelerator in the proton acceleration chain.

Since 1978, Linac2 has supplied all of the thousands of billions of billions of protons needed for CERN’s experiments. No experiment requiring protons could have run without the 37-metre-long machine, the first link in the accelerator chain. Its availability, which exceeded 98% in recent years, was therefore more crucial than that of any other machine to the operation of the dozens of experiments supplied by the subsequent accelerators in the chain, the PS Booster, the PS, the SPS and the LHC.

As its name suggests, Linac2 replaced Linac1, which had a maximum beam intensity of 70 milliamps. Linac2 came into operation in 1978 and, like its predecessor, accelerated beams up to 50 MeV, but with a much greater intensity, ranging from 50 to 150 milliamps (mA).

The accelerator underwent a major upgrade in 1993, when its first acceleration stage, a Cockcroft-Walton generator, was replaced with a radiofrequency quadrupole (RFQ) in order to increase the beam intensity. The aim of this upgrade was to supply higher intensity beams for the future LHC. From 1998 onwards, the accelerator thus provided beam intensities of 180 mA, the highest ever achieved by a proton linac.

Linac2 also underwent other renovations, including the replacement of its control system. But the heart of the accelerator, the three DTL (drift tube linac) RF cavities and their 120 quadrupoles, remained in place until the very end. Linac2 played a role in CERN’s great triumphs, such as the discoveries of the W and Z bosons in 1984 and the Higgs boson in 2012 and the production of the first antihydrogen atoms in 1996.

Despite Linac2’s performance, its energy was limited and in 2007 the decision was taken to replace it with an accelerator that could meet the needs of the future, particularly those of the High-Luminosity LHC. Linac4, which can accelerate protons to energies of 160 MeV, more than three times higher than Linac2, was designed for that purpose. The new accelerator was inaugurated in 2017 and will be connected to the PS Booster in 2020, during Long Shutdown 2.

A more detailed article will appear in the December issue of the Courier.

For all those who won’t be able to attend the TEDxCERN event scheduled on Tuesday 20 November 2018 at Bâtiment de Forces Motrices in Geneva on the theme An Elephant in the room, two panel discussions will be held in the Globe of Science and Innovation on Monday 19 November from 17:00.

This event will feature key speakers from TEDxCERN who will address topics such as the digital human rights in a data driven world and  the ethics behind evolving humans - from DNA manipulation to human cyborgs.

The short presentations (in English with simultaneous interpretation into French) will be followed by a questions and answers session with the public and a cocktail reception.

Limited number of seats. Mandatory registration on voisins.cern/en/events

Can’t make it? Follow the evening on the live webcast!

TEDxCERN is in the starting blocks. Todayy, 19 November, and tomorrow, inspiring international scientists and world-renowned artists will gather in Geneva to discuss what evolution will bring us in the future. Even if you are not among the almost 1000 lucky holders of a ticket for the main TEDx show taking place at the Bâtiment des Forces Motrices in Geneva, keep reading. 

The organisers have planned various opportunities for people to take part in this year’s TEDxCERN event in person or online. This afternoon, the renowned TED speaker and author Juan Enriquez will give a CERN colloquium in the Council Chamber. The event is open to the CERN community and also available via a webcast. Enriquez will discuss how life sciences will become the single biggest driver of the global economy and why physicists may end up driving biology. Almost in parallel, the Globe will become the venue for panel discussions featuring the TEDxCERN 2018 speakers. They will involve the audience in active discussions about digital human rights in a data-driven world and the ethics behind evolving humans – from DNA manipulation to humanoid robots. Although registration for the event is now closed, anyone can take part via webcast.

The main TEDxCERN 2018 event will start at 2 p.m. (CET) on Tuesday. It will address the elephant in the room, exploring the transformative scientific innovation that is affecting the world we live in and tackling the uncertainty of humanity’s destiny as a species. The premiere of a TED-Ed animation on neutron stars and gravitational waves, as well as a video recreating the magic atmosphere of the “Poetic AI” exhibition by Ouchhh creative studio, will feed your thirst for inspiration and imagination. All events are available online – just follow the links.

Many institutes and various locations around the world, including the University of Geneva, will host parallel TEDxCERN events, screening the webcast feed live. There is still time to host your own local event, or simply connect to the main live feeds to enjoy the various events. For more details, see the TEDxCERN website.

Derived from developments in accelerators, detectors and computing, the state-of-the-art technologies behind particle physics have historically contributed to innovations in medical technologies. CERN’s latest addition to this is GaToroid, a novel superconducting and lightweight gantry that can surround a patient and potentially revolutionise the delivery of hadrons for therapies, including cancer treatment.

Hadron therapy is an advanced radiotherapy technique using proton or ion beams to deliver precision treatment of tumours, sparing the surrounding healthy tissues from unwanted radiation. The intrinsic precision of this technique makes it particularly suitable for treating tumours in children or close to organs at risk. Furthermore, using rotating gantries to move the beam around the patient, medical doctors can irradiate the tumours from different angles, sparing even more of the surrounding tissue.

Gantries are complex pieces of engineering, representing a considerable part of the installation costs and size, or footprint, in hadron therapy. Particularly for carbon ions, there are only two gantries in the world. The first one is at the Heidelberg Ion-Beam Therapy Center in Germany, measuring 25 metres in length and weighing more than 600 tonnes. The second one, in Chiba, Japan, is a superconducting gantry with a reduced size and weight, but with the added challenge of a rotating cryogenic system. While the therapeutic interest for carbon or other ions heavier than protons is increasing, the enormous size of today’s gantries, combined with the lack of viable standard technological solutions, poses relevant constraints on future hadron therapy facilities. 

Well aware of these challenges, CERN scientist and magnet expert Luca Bottura came up with a new, innovative gantry design based on a toroidal magnet concept, GaToroid, which bends the treatment beam without the need to rotate the structure. The gantry comprises a set of fixed, discrete superconducting coils constituting the toroidal magnet, and a bending device at the entrance of the structure to direct the beam at the right angle. Due to the use of superconductors, GaToroid will substantially reduce weight and footprint compared to conventional gantries, especially for ion beams. This invention was not the output of a dedicated research study, but a result of serendipity coming from Luca’s connection to other fields of applied science and his own professional experience.

Luca Bottura will present his idea at the next Knowledge Transfer Seminar, GaToroid: A Novel Superconducting Compact and Lightweight Gantry for Hadron Therapy, which will be held on 22 November at 4 p.m. CET in the Council Chamber at CERN and via webcast.

For previous features on hadron therapy, see the CERN Courier articles “Therapeutic Particles” and “The changing landscape of cancer therapy”.

The Jardin des Particules, the crèche and school run by the Staff Association, currently has a number of full- and part-time places available.

Places available immediately:

• Crèche: in the class for children aged 2-3 years
• School: in the class for children aged 4-6 years

Places available as of January 2019:

• Crèche: in the classes for children aged 2-4 years (mornings only) and 3-4 years

For further information, do not hesitate to contact us by e-mail: Staff.Kindergarten@cern.ch

The Jardin des Particules steering committee

Following on from Java, app programming, Raspberry Pi, cloud computing and machine learning, the latest trend for computer engineering students is blockchains. One particular application of blockchains is “crypto-currencies”, i.e. virtual money. The past year has seen the birth of a plethora of crypto-currencies. Bitcoin is the best known, but there are also Ethereum, Litecoin, Dogecoin and many more (see Wikipedia for an even longer list). Even some famous football players are considering creating their own currencies. All these currencies have one thing in common; in order to obtain coins, there are just two legal methods: you buy them or you “mine” them. The latter is based on a complex mathematical calculation, which eventually results in more coins being added to the total pool and to your digital purse. So here is the problem: what about crypto-mining at CERN?

In order to answer that question, one has to distinguish between crypto mining for professional or private purposes, and whether you’re using a CERN-owned computer or a private computer. CERN’s Operational Circular No. 5 (OC5) on the “Use of CERN Computing Facilities” stipulates that the private or personal use of those facilities is tolerated or allowed as long as “it does not constitute […] profit-making activity” (OC5 “Rules for personal usage” 3c). However, the fundamental nature of crypto-mining is exactly this: making money. Hence, OC5 and its “Rules for personal usage” do NOT allow any kind of crypto-currency mining. Any violation could have serious consequences (see our Bulletin article on "Computing power for professionals… only!").

When using CERN resources (computers, laptops, servers or virtual machines), mining for professional purposes lacks any reasonable professional justification. While the potential additional demand for electricity is debatable, crypto-mining blocks CERN resources from performing their professional tasks as it takes away CPU cycles, storage memory and network bandwidth. Given that, for Run 3 of the LHC, CERN’s computing needs will grow exponentially, our computing resources should be invested wisely and not wasted. Hence, as the “CERN computing facilities are intended for the attainment of the Organization's aims” (OC5 II 6.), crypto-currency mining on CERN owned hardware is completely forbidden. Exemptions are possible under the authorisation of CERN’s Computer Security Officer, e.g. for stress testing computing hardware or computing power benchmarking. However, experts would need to justify why globally-recognised tools like those provided by the HEPix benchmarking working group are not suitable. And in any event, any money generated in this way belongs to CERN and should be transferred to the appropriate CERN budget code.

_______

Do you want to learn more about computer security incidents and issues at CERN? Follow our Monthly Report. For further information, questions or help, check our website or contact us at Computer.Security@cern.ch.

Last week, at the 2018 Supercomputing Conference in Dallas, Texas, two new companies announced that they are joining CERN openlab. CERN openlab is a unique public-private partnership through which CERN collaborates with leading ICT companies to accelerate the development of the computing technologies needed by the high-energy physics research community.

On Monday 12 November, Micron Technology announced that they had joined CERN openlab. As part of the work with CERN, Micron will develop and introduce a specially designed Micron memory solution that will be tested by researchers at CERN to rapidly comb through the vast amounts of data generated by experiments. Specifically, the technology will be tested in the data-acquisition systems of the CMS experiment and the ProtoDUNE detectors.

“CERN collaborates openly with both the public and private sector, and working with technology partners like Micron helps ensure that members of the research community have access to the advanced computing technologies needed to carry out our groundbreaking work,” says Maria Girone, CTO at CERN openlab. “It is critical to the success of the Large Hadron Collider that we are able to examine the petabytes of data generated in a fast and intelligent manner that enables us to unlock new scientific discoveries.”

On Wednesday 14 November, Google published a blog post announcing that they had signed an initial agreement to collaborate with CERN through CERN openlab. Together, we are now exploring possibilities for joint research-and-development projects related to cloud computing, machine learning, and quantum computing. Google also participated in a quantum-computing workshop organised at CERN earlier this month.

“CERN has an ambitious upgrade programme for the Large Hadron Collider, which will result in a wide range of new computing challenges,” says Alberto Di Meglio, head of CERN openlab. “Overcoming these will play a key role in ensuring physicists are able to make new ground-breaking discoveries about our universe. We believe that working with Google can help us to successfully tackle some of these challenges, as well as producing technical breakthroughs that can have impact beyond our research community.”

With 2018 marking the start of a new three-year phase for CERN openlab, there are now around 20 ongoing research-and-development projects. E4 computer engineering also joined CERN openlab last month, bringing the total membership to 12 companies and nine research organisations. During this phase, the collaboration is working to address many of the ICT challenges laid out in its latest white paper.

- 18.00 CHF per person -

Three portions of raclette

Charcuterie

Potatoes

Complimentary limoncello

Book on 022 767 28 14 or at the tills in restaurant 1

French law does not authorise holders of a special residence permit issued by the Ministry for Europe and Foreign Affairs (MEAE) to exchange a driving licence issued by a country that does not belong to either the European Union (EU) or the European Economic Area (EEA) for a French driving licence (cf. http://international-relations.web.cern.ch/stakeholder-relations/hoststates/Vehicles/Foreign-driving-licenses-France).

Following problems encountered by several members of the personnel, CERN has asked the MEAE to investigate the possibility of authorising such an exchange in cases where the issuing country has signed a reciprocal agreement and refuses to replace a stolen, lost or expired driving licence. This would avoid those concerned being systematically required to pass a driving test in France.

In this context, you are reminded that people residing in Switzerland and holding a carte de légitimation issued by the Federal Department of Foreign Affairs (DFAE) may exchange their foreign driving licence for a Swiss licence without taking a test, provided that Switzerland and the country of origin have signed an agreement on this matter (cf. https://www.eda.admin.ch/missions/mission-onu-geneve/en/home/manual-regime-privileges-and-immunities/introduction/manual-vehicles/foreign-driving-license.html).

Host-States Relations Service
Tel.: 72848 / 75152
relations.secretariat@cern.ch
www.cern.ch/relations

As with each edition, this year’s TEDxCERN triggered a high dose of inspiration and raised a multitude of questions in terms of science, technology and the future of humankind. The “Elephant in the room” theme was matched by a carefully crafted script on burning issues and positive ways to address them. Never shying away from controversial questions and the risk aspects of each topic, the event highlighted the necessity for wise design and regulation of the technology we develop, rather than fearing progress.

The first session was themed around the question “Will we destroy ourselves?” and combined a number of talks on issues of the digital age. Sinan Aral opened the show by approaching political, economic and health impacts of social media on society. He raised questions around “fake news” and the way we consume information. "Who gets to decide in society what's true and what's false? And who's checking the fact-checkers?" he asked. Later on, documentary-makers Hans Block and Moritz Riesenwieck cross-examined content moderation and its moral implications. Shermin Voshmgir, blockchain expert and director of the Research Institute for Crypto Economics at the Vienna University of Economics, discussed how cryptocurrencies are revolutionising the digital world. Maja Pantic gave an overview of Emotional Artificial Intelligence and the promises and risks of machine learning. Joanna J. Bryson concluded the first session’s talks with a psychological framing of AI and its intimate relationship with the human mind.

Janice Chen, biologist and CRISPR pioneer from the University of California, Berkeley, opened the second session, with the question “Will we create new selves?” as its theme. She envisioned a future in which CRISPR, a genome editing technology, could provide real time diagnostics and potentially head off epidemics. The following speaker, Sanushka Naidoo discussed the potential of new biotechnology tools to address plant responses to pests and pathogens and possible solutions for the future of world-food production and sustainability. “Genetic Modification is a biotechnology that can benefit the hungry and the poor, but it is not accessible due to regulations based on fear and ignorance”, she said. Another topic at the heart of the session was the Anthropocene and the future of the Earth. Elena Bennett, a systems ecologist, provided a positive insight into the way humanity could pursue sustainable development by focusing on a conscious behaviour towards the environment. “It is time for us to start thinking about a radical and inspiring future", was her rallying call.

NASA astrophysicist, Dawn Gelino, explained the challenges linked to research on exoplanets. “There are more stars in our little galaxy than grains of sand in all of our beaches. We are small and insignificant in a vast universe,” she said in her mind-blowing talk on space exploration. Juan Enriquez, renowned TED speaker and life scientist, untangled some of the mysteries of today’s biology and genetics. “The new biology is proactive. Instead of looking for things, we are able to build them. What do we do with this stuff? Well, programmed life forms are going to change the world,” he claimed, adding that “we might only be one to two decades from generating life from scratch.”

To complete the futuristic charm of the show, Kevin Ramseier, Thomas Köppel and François Moncarey of CENC (Centre for numeric and corporal expression) engaged in a marvellous game with digital tools and the laws of physics, by creating a video dance performance where the dancer controls the visual and auditory matter, which they shaped into frequencies, oscillations and vibrations.

In conclusion, the 2018 edition of TEDxCERN was incontestably a success and reached an unprecedented audience – over 900 present in the room and around 3000 watching the webcast from 32 different locations around the world.

"TEDxCERN is a very powerful opportunity for putting across and engaging citizens in cutting-edge science, be it the science we do at CERN or research in other fields. It is very positive to see CERN taking a leading role in highlighting the “elephant in the room” aspects, promoting and mediating these discussions. It is strongly in line with the mission of the Lab of being a voice for fundamental research and its impact on society.” - Ana Godinho, CERN’s Head of Education, Communications & Outreach.

Stay tuned in the following weeks to watch the video recordings of each talk. In the meantime, enjoy the event in imageshere.

The World Scientific Publishing Book Fair will take place on the ground floor of the Main Building (500), near Restaurant 1, on Tuesday, 4 and Wednesday, 5 December 2018.

In the framework of the Book Fair, a presentation by Antonio Ereditato of the book The State of the Art of Neutrino Physics is scheduled for 3.30 p.m. on 5 December in the Library (52-1-052). After the book presentation, Antonio Ereditato will also present, as the editor-in-chief, the Open Access journal Instruments, published by MDPI: https://www.mdpi.com/journal/instruments.

The State of the Art of Neutrino Physics: A Tutorial for Graduate Students and Young Researchers, ed. Antonio Ereditato, World Scientific, 2018, ISBN 9789813226081 https://www.worldscientific.com/worldscibooks/10.1142/10600

Although the LHC is approaching the end of Run 2, a major milestone in its history, there is little sense of this in the CERN Control Centre, where the one-month 2018 heavy-ion run has just one week left to go. Much still has to be achieved before the start of Long Shutdown 2 (LS2) on the morning of 3 December and there is no let-up in the pace of activity.

The heavy-ion source has made a remarkable recovery from its emergency surgery at the start of the run. The chain of accelerators downstream, starting with LEIR, have cooled, bunched, stripped and accelerated the stream of ions emerging from Linac3. The single-bunch intensity quickly exceeded the target for the HL-LHC. Until 19 November, bunches were delivered from the PS to the SPS in batches of four separated by 100 ns. A new scheme with batches of three bunches separated by 75 ns is now in use. Besides allowing more bunches to be packed into the LHC rings, this is already delivering even higher intensities in each bunch.

Nevertheless, one should not get the impression that all is plain sailing. Taking the injectors and LHC into new domains of operation continually throws up surprises and the teams concerned are in permanent problem-solving mode. The unprecedented intensities cause collimation losses that are always close to limits that can cause the beam to be dumped to avoid magnet quenches (new installations during LS2 will help with that). An unexplained motion of the beam orbit at a frequency of 10 Hz has provoked a few premature dumps. It is now clear that this was present in the preceding proton run but it causes more trouble for lead beams.

Problem-solving is further complicated by the need to weigh the time taken for conclusive investigations against the potential gains in the remaining run time. Decisions are based on hard data, physical understanding and judgement, but are subject to the strictures of machine protection. Continual interaction with the LHC Programme Coordinators ensures that the priorities of the LHC experiments are best served.

For example, the beam size at the ALICE interaction point was found to be twice the size it should be and measures had to be taken to reduce the impact on the integrated luminosity. A textbook explanation for this is a shift of the beam waist (the place where the beam is smallest) away from the interaction point (see a picture of the beam optics in the ALICE experiment in the last LHC Report). An initial measurement (moving the collision point using the RF system) hinted that this was the case – just before it was aborted by an interlock. A later measurement was completed but refuted this hypothesis. Finally, based largely on theoretical considerations, Stéphane Fartoukh identified the cause as a strong, but highly localised, coupling of the horizontal and vertical betatron motions and proposed an elegant solution. This worked almost magically, restoring the proper beam sizes and luminosity for ALICE.

This was accomplished during the scheduled refill of the ion source. Then followed a rigorous re-validation of a new collision configuration with the polarity of the ALICE spectrometer magnet and crossing angle reversed, as requested for the second half of the data-taking. At the same time, the injectors have been switching to the new 75 ns injection scheme and the LHC has been learning to handle very high lead bunch intensities up to four times the original design value.

On 25 November, a new peak luminosity record of 6×10²⁷cm^-2s^-1 (i.e. six times the original LHC design value!) was set in both ATLAS and CMS. LHCb is also receiving far greater heavy-ion luminosity than ever before and ALICE is being held at its saturation value for 8 hours in typical fills.

Peak luminosities in ATLAS and CMS are being steadily increased from fill to fill, with the goal of demonstrating the nominal value for the HL-LHC. And a few special measurements are still to come…

Some of the activities at CERN can be rustic. More than 65 CERN people discovered in November the horse-logging technique during a series of visits organized by the Education and Communication Group and the French National Forestry Office (ONF). During maintenance work on the CERN wooded plots, horses are regularly used to remove the fallen trees, thus minimizing the impact on forest soils. The CERN site covers 625 hectares, of which 90 are woods and forests. There is particular interest in seeing how efficiently the system will work in cleaning the complex losses from heavy-ion beam halos. These wooded areas are maintained and valued by the National Forestry Office.

Last week’s snow reminded us that winter is on its way, with all its attendant possibilities. However, it is not all fun: winter also brings potential health and safety risks, most of which can be easily avoided by taking a few simple precautions.

Every year, seasonal influenza – the flu – takes its toll, but the seasonal flu vaccine can protect you and those around you. If you work on the CERN site, you can be vaccinated at CERN’s Medical Service. Just bring along your sealed dose of vaccine – no need for a prescription. Moreover, the flu virus is not the only one waiting to get us in the winter, so the Medical Service publishes a guide to the simple things we can do to avoid infection as the temperature drops.

The winter months also see an increase in road accidents due to shorter days and icy roads and footpaths. Make sure your car is equipped for winter weather conditions, make sure you wear appropriate clothing and allow more time for journeys. On dark winter nights, it is especially important to make sure you can be seen. Research shows that when we are wearing dark clothes on a dark evening, even with street lighting, drivers see us only when they are just 25 metres away. That is not enough for them to stop safely from a speed of 50km/h. Wearing light-coloured clothing increases this distance to 40 metres. But only if we are wearing something reflective can the driver see us in time to stop safely.

To help inform you of these risks, we will be running a short campaign on the importance of being visible in the dark, and will shortly be distributing reflectors outside CERN’s three main restaurants at lunchtime. Keep an eye on the Bulletin for the exact dates. Reflectors are proven lifesavers – make sure you get yours!

So, keep warm, keep healthy, keep safe… and enjoy the snow!

_________

Useful information:

• Advice on avoiding the flu from CERN’s Medical Service
• Road safety advice (in German, French and Italian)
• Winter safety guide (in English)
• Swiss Made Visible campaign (in German, French and Italian)
• Guide to safety in the mountains in winter (available in many languages)

Please note that, due to work under way to install a new gate, access to hall SM18 via the Route de l’Europe will not be possible on 17 and 18 December and from 14 to 18 January 2019. People requiring access to the site during these periods are invited to use the BA7 entrance.

The work will begin on 26 November 2018 and will last until 24 January 2019.

Thank you for your understanding.

This year, CERN will be closed from Saturday, 22 December 2018 to Sunday, 6 January 2019 inclusive. The first working day of the new year will be Monday, 7 January 2019.

As is the case every year, the only persons who will be entitled to enter the CERN site during the end-of-year closure are those who have received authorisation to do so for strictly professional reasons such as stand-by service and indispensable maintenance work.

Each department and, in particular, each experiment’s technical coordinator, is responsible for compiling a list of the people in receipt of such authorisation by Friday, 21 December 2018 at the latest.

Unlike in previous years, it is no longer necessary to include members of the personnel of outside companies in these lists. Any members of the personnel of outside companies who are required to work on the CERN site during the closure must have a valid AET (notice of work done outside normal working hours). Note that each AET will be limited to the time needed to perform the work in question.

During the period when the Laboratory is closed, i.e. after 21 December, anyone who needs to enter the CERN site for an urgent reason and without the prior authorisation of her/his department or her/his experiment’s technical coordinator will be obliged to submit an access request (select the “CERNXMAS” permission) that can be signed by the Security Service or the CCC (TI) after assessing its merits. The “CERNXMAS” permission option will not be available in the ADAMS system prior to 22 December. This provision does not apply to members of the personnel of outside companies since they must have a valid AET.

You are also kindly asked to note that all CERN services (including the restaurants and the library) will be closed during the end-of-year closure.

We thank you for your cooperation and wish you a very happy end-of-year holiday!

Beams travel inside the LHC at close to the speed of light and cleaning out particles that fly too far from the main path is not an easy feat. More than 100 collimators punctuate the ring at specific locations to make sure that the particles that stray – called beam halos – are cleaned or absorbed to protect delicate accelerator equipment. This October, an advanced technique using bent crystals was proven to increase the overall performance of the cleaning process.

Bent crystals, as the name suggests, are crystals bent mechanically to create a curve at a microscopic angle. The nature of crystalline structure means that halo particles, which would otherwise scatter at random angles, can be steered and channeled directly toward absorbers installed downstream, relaxing the need for the secondary and tertiary collimators used by the LHC’s existing system. This application for beam collimation was triggered by the pioneering work started by the UA9 collaboration in 2009, and is supported by funds from the High-Luminosity LHC project. Used in several scenarios, bent crystals were a tool for collimation studies in the LHC, but had never been used in a physics run until now.

“We have two bent crystals installed on each LHC beam pipe at Point 7 for crystal collimation studies,” says Stefano Redaelli, who is in charge of the LHC collimation system and its upgrade for the High-Luminosity LHC. “In these devices, halo particles are steered by the highly pure periodical lattice structure of the crystal. At 7 TeV, channeling in bent crystals can curve the particle trajectory by amounts that are beyond the reach of the LHC superconducting magnets. For instance, a 4mm long silicon crystal, with a bending angle of 50 micro radiant, produces about the same effect as that of 10 standard LHC dipoles together!”

Beam halos are a nuisance, as they can damage sensitive equipment like superconducting magnets and also affect the quality of physics data by creating more background noise. To reduce this effect, the LHC’s beam collimation team use many different techniques. One such technique is scraping, which requires interrupting the beam to clean and diffuse the halo, causing a significant time loss per fill before data-taking can resume. With bent crystals, beam halos are steered toward dedicated absorbers, reducing this time loss and increasing the quality of data by providing cleaner backgrounds.

“We decided to use crystals to control background particles on the TOTEM and ATLAS-ALFA experiments’ Roman pot detectors. Detailed simulations were carried out before the crystals were inserted and used as primary collimators for low-intensity beams,” says Redaelli. The results measured showed less background noise and frequent scraping was not needed. 

Tunnel view of the crystal goniometer that is used to adjust the crystal angle with respect to the beam, with sub-micro radiant precision. The design is developed by the EN/SMM group and installed in the LHC by the EN/STI group. (Image: courtesy of D. Mirarchi, CERN)

Tests of crystal collimation to clean beams will continue until the end of the year. Many teams have been involved in the development of crystal collimation systems installed in the LHC, including the Accelerator and Beam Physics (BE-ABP), Survey, Mechatronics and Measurements (EN-SMM), and Sources, Targets and Interactions (EN-STI) groups. There is particular interest in seeing how efficiently the system will work in cleaning the complex losses from heavy-ion beam halos.  These new results will provide important input to decide if crystal collimation can become part of the upgrade plans for the HL-LHC.

* The UA9 Collaboration consists of CERN, PNPI, INFN, LAL, JINR, IHEP, Imperial College London.

The Advisory Committee of CERN Users (ACCU) is the forum for discussion between the CERN Management and the representatives of CERN Users to review the practical means taken by CERN for the work of Users of the Laboratory. The mandate of ACCU is available on: http://accu.web.cern.ch/content/mandate

There are one or two Delegates from each Member State (two Delegates from the large Member States), one Delegate from each of the Associate Members, four Delegates from non-Member States (NMS), and two from CERN. The list of ACCU members is available on: http://accu.web.cern.ch/content/accu-members

ACCU meetings are attended by the Director General and members of the Directorate, other members of the CERN management and departmental representatives, the Head of the Users' Office and a representative of the CERN Staff Association. Other members of the CERN Staff attend as necessary for specific agenda items.

Chairperson: Dragoslav-Laza Lazic (Dragoslav.Lazic@cern.ch)
Secretary: Michael Hauschild (ACCU.Secretary@cern.ch)

Anyone wishing to raise any points under “Any Other Business” at the upcoming ACCU meeting is invited to contact the appropriate User representative, or the Chairperson or the Secretary.

Official holidays in 2019 (in addition to the special leave during the annual closure):

• Tuesday, 1 January (New Year)
• Friday, 19 April (Good Friday)
• Monday, 22 April (Easter Monday)
• Wednesday, 1 May (1st May)
• Thursday, 30 May (Ascension day)
• Monday, 10 June (Whit Monday)
• Thursday, 5 September ("Jeûne genevois")
• Tuesday, 24 December (Christmas Eve)
• Wednesday, 25 December (Christmas)
• Tuesday, 31 December (New Year’s Eve)

Annual closure of the site of the Organization during the Christmas holidays and days of special leave granted by the Director-General:

The Laboratory will be closed from Saturday, 21 December 2019 to Sunday, 5 January 2020 inclusive (without deduction of annual leave). The first working day in the New Year will be Monday, 6 January 2020.

Human Resources Department
Tel.: 62959