CERN Accelerating science

Electron Lens Test Stand at CERN

Header Image: Electron Test Stand gun and collector magnet. (Courtesy of Giulio Stancari, Fermilab)

Due to the high stored energy in the HL-LHC beam tails (estimated to be in the order of 34 MJ above 3.5 beam σ with beam emittance of 3.5E-6 rad m [1]), it is desirable to have active halo control providing more margin during all the operational phases of HL-LHC.

Hollow Electron Lenses [2], [3], give a means of depleting the tails without using intercepting material, avoiding the risk of damage and not contributing to machine impedance. Halo particles that migrate into the electric field generated by a hollow electron column travelling concentrically around the circulating proton beam over a short distance, will be ‘kicked’ to larger oscillation amplitudes (a slow, continuous process) and be pushed towards the collimators. This leads to a cleaning of the tails.

At CERN, an option of installing Hollow Electron Lenses [4], [5] for HL-LHC is being studied; one per beam line (~ 40 m left and right from IP4). Each will provide a 5 A ‘tube’ of electrons, confined with a solenoid magnetic field, counter-propagating concentrically around the circulating high energy proton beams over 3 m of interaction length, see Figure 1. In order to accelerate halo depletion, the electron beam can be modulated On/Off at 35 kHz, with 200 ns rise-time, thereby adding a non-linear effect to the kicks given to the halo particles [6]. This way one can switch the e-beam on and off between trains, and target trains at random or a fixed number of turns.

The degree to which the electron and proton beams overlap as well as the electron beam profile will be measured with a new device being developed in collaboration between CERN and Cockcroft Institute [7], [8]. This so-called Beam Gas Curtain (BGC) monitor, is based on imaging beam induced gas fluorescence from a supersonic gas curtain.

 

Figure 1: Hollow Electron Beam around the circulated beam (left hand side) and schematics of the Collimation Scheme for HL-LHC (right hand side). (Courtesy of Stefano Redaelli, CERN)

Electron Lens for Space Charge Compensation

Space Charge Compensation of intense ion beams (in SIS18, GSI [9], [10]) by non-neutral plasma columns is being studied within the European ARIES project, a collaboration between GSI (Darmstadt), IAP (Frankfurt), RTU (Riga) and CERN. The Joint Research Activity will develop and build a gun prototype capable of providing electron beams currents of up to 20 A in an oval of 70x50, and able to be modulated with changing transverse and longitudinal profile at a bandwidth of 2 to 5 MHz.

An electron lens test stand is required at CERN for:

  • Acquiring operational experience with electron beams of high intensity and high space charge density (5A in a few mm for the Hollow Electron Lens)
  • Testing components for HL-LHC Hollow Electron Lens (HEL), in particular:
    • characterizing the electron gun current emission yield as a function of cathode temperature (800 to 1000 oC) and extraction voltage (0 to 10kV), and measuring the transverse profile of the electron beam to check uniformity and cathode material quality
    • testing the HV modulator working at 10 kV and 5A, 35 kHz repetition rate
    • testing HV power converters pulsing at 35 kHz
    • designing and testing the HEL control system
    • testing the HEL collector repellers and diagnostics
    • testing the Beam Gas Curtain diagnostics for high-density, hollow electron beams
    • testing the Beam Position Monitor response with the available e-beam modulation
  • Testing components for SIS18 SCC, in particular
    • characterizing the electron gun current emission field and transverse profile of the electron beam
    • testing the HV modulators.

The E-lens Test Stand is being constructed using a staged approach, to commission its main components separately, and validate the measurement techniques.

Stage 1 (see Figure 3) is composed of:

  • A gun solenoid of 180 mm aperture, 300 mm length, and up to 0.3T magnetic field
  • A collector solenoid of 135mm aperture, 300 mm length, and up to 0.5T magnetic field
  • A diagnostic box with a Pin Hole Faraday Cup and a YAG screen (see more details later)
  • A bake-out and pumping system to guarantee pressures of the order of 10-10 mbar
  • A collector chamber with passively cooled “Faraday Cup” with viewport.
  • A pulsing device (10 msec 10 Hz, corresponding to a duty cycle of 10-4)
  • Measurement of current with the current transformer in the cathode power converter with 200 MHz bandwidth.

Measurements that can be carried out with Stage 1 are the following:

  • Gun characterization, i.e. measurement of the current emission yield as a function of cathode temperature (typically of the order of 1000 oC) and as a function of the extraction voltage (typically 0 – 10 kV for the HEL gun and up to 25 kV for the SCC gun).
  • Measurements of the beam profile and current with varying magnetic field at the gun.
  • The transverse profile of the electron beam and its energy distribution.
  • Test of auxiliary equipment (e.g. rise time of the anode modulator).

Schematics of the hollow electron gun are shown in Figure 2. 

Figure 2. Layout of a hollow electron gun  (as scaled for the from Fermilab design – Tevatron): Left hand side: mechanical assembly (courtesy of D. Perini, CERN). Right hand side: cathode and shaping electrode (in red), control electrode (in blue) and anode (in green). (Image: CERN)

References for this type of gun and the results of similar measurements can be found in [11], [12], [13], [14].

Measurements of the beam profile as a function of the accelerating voltage (at constant extraction voltage), will require an additional power supply (upgrade A). Testing of the HEL HV modulator will need biasing of the collector to reduce the energy dissipated, adding another power supply (upgrade B).

Figure 3. Layout of the Electron Lens Test Stand, Stage 1: composed of a gun and collector solenoid plus a diagnostic box. (Image: CERN)

Figure 4. Electron Test Stand gun and collector magnet as from today’s installation. (Image: CERN)

The installation of a drift solenoid (Stage 2, shown in Figure 5) is necessary to study electron beam dynamics, develop the beam position monitor, test the BGC with different electron beam sizes, and full testing of the HV modulator performance (frequency of switching and longitudinal modulation for the ARIES application).

In the current plans, the Stage 2 drift solenoid will be a dry, superconducting solenoid, 1 m long, with a magnetic field up to 4 T. Such a solenoid will allow compression of the electron beam by up to a factor of 3 and greatly increase the span of beam dynamics studies possible.

Figure 5. Layout of the Electron Lens Test Stand. Stage 2: derived from Stage 1, adding a drift solenoid between the gun solenoid and the diagnostic box, and upgrading the collector to take more deposited power. (Image: CERN)

Diagnostic box

The Electron Lens Test Stand diagnostic box (Figure 6) hosts the instrumentation able to measure electron current and transverse profile, namely a Pinhole Faraday Cup and a YAG Screen, and possibly a Langmuir probe to measure the electron temperature, electron density, and electric potential. The diagnostic box vacuum chamber (depicted in Figure 7) has several arms for the insertion of the instrumentation, a turbo-pump and a vacuum gauge. The arms have an hippodrome-like shape to minimize the space between the gun and collector solenoid (so that the magnetic field drop at the box itself is minimal) while guaranteeing that the Pinhole Faraday Cup can be swept laterally to cover the transverse size of the electron beam, and leaving enough conductance for the turbo-pump.

Figure 6. Diagnostic box showing the actuators of the Pinhole Faraday Cup and the YAG Screen, a pump and a vacuum gauge. (Image: CERN)

Figure 7. Diagnostic box vacuum chamber. (Image: CERN)

With respect to existing test stands (for example at Fermilab, US, or IAP, Frankfurt), the CERN test stand offers the big advantage of providing diagnostics that sweep through the beam (rather than moving the beam through a fixed diagnostic set-up), a larger accelerating field and a larger drift magnetic field.

The fact of moving the diagnostics rather than the beam will give a more accurate measurement of the transverse beam profile, since the electron beam dynamics for such a non-relativistic beam also depends on the beam position relative to the vacuum chamber walls. For HEL applications, it is very important to accurately establish the shape of the electron beam and its dynamics (i.e. that it stays round along the whole interaction length) since the presence of a residual electric field in the center of the electron beam could perturb the circulating proton beam, especially if pulsed.

The CERN test stand also allows for a comparison between measurements with the Pinhole Faraday Cup, the YAG screen and an eventual beam gas curtain monitor.


References

[1] G. Valentino, presentation at the Review on the needs for a Hollow Electron Lens for the HL-LHC, CERN, 06.10.2016, https://indico.cern.ch/event/567839/contributions/2295258/attachments/1349453/2036619/Halo_MDs_operation_HEL_Review_20161006.pdf
[2] V. Shiltsev, in Proceedings of the CARE-HHH-APD Workshop (BEAM07), CERN-2008-005 (2008) https://care-hhh.web.cern.ch/CARE-HHH/BEAM07/Proceedings/Proceedings/Session%204/S14-Shiltsev-a4.pdf
[3] G. Stancari et al, Phys. Rev. Lett. 107, 084802, https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.107.084802
[4] G. Stancari et al, Conceptual design of hollow electron lenses for beam halo control in the Large Hadron Collider, FERMILAB-TM-2572-APC, CERN-ACC-2014-0248, https://arxiv.org/abs/1405.2033
[5] D. Perini and C. Zanoni, Preliminary Design Study of the Hollow Electron Lens for LHC, CERN-ACC-NOTE-2017-0004  https://cds.cern.ch/record/2242211
[6[ M. Fitterer et al., in Proceedings of IPAC2017, Copenhagen, Denmark, http://accelconf.web.cern.ch/AccelConf/ipac2017/papers/thpab041.pdf
[7] V. Tzoganis, in Proceedings of IPAC2014, Dresden, Germany
[8] H.D. Zhang, in Proceedings of IPAC2017, Copenhagen, Denmark, http://accelconf.web.cern.ch/AccelConf/ipac2017/papers/mopab139.pdf
[9] W.D. Stem at al., in Procedeengs of HB2016, Malmö, Sweden, http://accelconf.web.cern.ch/AccelConf/hb2016/papers/thpm5x01.pdf .
[10] D. Ondreka et al., in Proceedings of IPAC2017, Copenhagen, Denmark, http://accelconf.web.cern.ch/AccelConf/ipac2017/papers/tupva059.pdf
[11] A. Sharapa et al., Nucl. Instrum. Methods Phys. Research A, 406, 169 (1998), https://www.sciencedirect.com/science/article/pii/S0168900297011911?via%3Dihub .
[12] A. Ivanov and M. Tiunov, in Proceedings of the 2002 European Particle Accelerator Conference (EPAC02), Paris, France, June 2002, p. 1634, http://accelconf.web.cern.ch/AccelConf/e02/PAPERS/WEPRI050.pdf .
[13] S. Li and G. Stancari, FERMILAB-TM-2542-APC (August 2012), http://inspirehep.net/record/1181720 .
[14] V. Moens, Masters Thesis, École Polytechnique Fédérale de Lausanne (EPFL), Switzerland, FERMILAB-MASTERS-2013-02 and CERN-THESIS-2013-126 (August 2013) http://cds.cern.ch/record/1599475 .

 

 

Isabel Bejar Alonso (CERN) , Panagiotis Charitos (CERN)
A bright future for HL-LHC
7 Dec 2017

A bright future for HL-LHC

The 7th HL-LHC annual collaboration meeting in Madrid reviewed the current progress and set the goals for next year.

Claire Murray (Diamond), Daniela Antonio (CERN)
Project M: Diamond Light Source engages students in citizen science
28 Mar 2019

Project M: Diamond Light Source engages students in citizen science

How to prepare a set of 1000 samples to be analysed at a beamline in the shortest time possible?

Mauro Taborelli (CERN)
EVC-15 conference held in Geneva
8 Oct 2018

EVC-15 conference held in Geneva

The European Vacuum Conference (EVC) assembled experts from all over the world to discuss the latest developments in the field.

A new JTT shielding adapting ATLAS to Hilumi configuration

Header Image: ATLAS detector (Image: CERN)

For the HL-LHC Collider-Experiment Interface Work Package, their LS3 started last January with the manoeuvres to remove the ATLAS end cup toroid (JTT) shielding.

Why start in LS2 something planned for LS3?

Mainly because the activation of the components in the JTT shielding region will be 25 times higher during LS3 than was during LS1 and so we should try to advance any work that is feasible to reduce future doses to personnel.

The transition between the LHC tunnel and the experimental caverns is the most difficult region in terms of accessibility of the full ring. Currently, there are a number of machine components belonging to the vacuum and beam instrumentation systems located at that precise place, just behind the Target Absorber for Secondaries.  Moving them to the experimental caverns (in the IP side of the TAS) would offer a safer environment for interventions, adding the possibility to operated them remotely and so reduce the workers exposition to radiation.

However, space in the experimental caverns is rare. Every millimetre is  taken when opening of the detectors for routine maintenance tasks . After more than one year of collaborative effort and some compromises, a solution was found to relocate the VAX. In the case of ATLAS, the first of the implications foreseen to host the future VAX being compatible with detector openings was the modification of the JTT shielding.

From the 14th to the 31st January the ATLAS JTT was removed thanks to the ATLAS and CERN Engineering department teams. The transport procedure had to be completely rethink as we did not had any more a not yet completely installed experiment as was the case in 2006. A new support structure and a crab system was installed to allow the removal of the 13 Tones casted iron and boride polyethylene shielding that today is already stored in CERN ISRs waiting for its final treatment.

The new JTT units are today under construction in Pakistan. HMC3, that already contributed to the ATLAS experiment under the supervision of PAEC, should deliver them before the end of LS2. The new pieces have an innovative design compatible with the VAX.

Always having in mind personnel safety, the ATLAS forward shielding blocks will be machined during LS2. This operation requires handling of close to 100T pieces.

From the CMS side work is also frenetic. The new support for the VAX will be already installed during LS2 allowing the relocation of other vacuum equipment, while the forward shielding will also be modified in prevision of the new VAX modules.

The new VAX for ATLAS and CMS is nowadays in its prototyping phase. A new vacuum chamber handling and support compatible with remote operations and the new layout is under construction, and will be thoroughly tested with the collaboration of different CERN groups: Experimental Areas, Vacuum, Transport, Survey and Mechatronics.

Ch. Bracco, D. Carbajo Perez and A. Perillo Marcone
Ensuring safer operation at higher luminosities
12 Mar 2018

Ensuring safer operation at higher luminosities

The higher bunch intensities and smaller beam emittances expected in HL-LHC call for a novel design of the Target Dump Injection (TDI)

Romain Muller (CERN)
And the winners of the ARIES Proof-of-Concept fund are…
3 Jul 2018

And the winners of the ARIES Proof-of-Concept fund are…

Take a closer look at the potential of the selected projects

Jim Clarke (STFC)
CLARA Update: First Accelerated Beam
8 Dec 2017

CLARA Update: First Accelerated Beam

UK’s Free Electron Laser Test Facility reached another significant milestone.

A new step for High-Luminosity LHC

HL-LHC civil engineering works at Point1, Meyrin, Switzerland. (Image: CERN)

Last October took place in Geneva the 8th HL-LHC Collaboration Meeting, the annual gathering of the project community to measure progress and to discuss the latest design and production objectives. A growing community, that has seen during this year the arrival of Triumf (Canada) and IHEP (China) and the increase of contribution from existent collaboration members such as PAEC (Pakistan), Uppsala University (Sweden) or the UK STFC and Universities contributing to HL-LHC.

8thmeeting_HL-LHC.jpg
Members of the collaboration. (Image: CERN)

Plenty of successful milestones were reached in 2018. This year saw the installation of the first crab cavities cryomodules in the SPS, the starting of the civil engineering works and the brilliant results of the fourth short model of the Nb3Sn quadrupole and of the seventh short model of the 11 T. Moreover,the long prototypes of the 11T dipole and the Nb3Sn quadrupole were tested and the first results don’t match those from  the short models, thus demonstrating that the industrialization of magnets is a long path without shortcuts. The 8th annual meeting put together the key actors to analyse what worked and what any deviations from the original plan to ensure that the project is completed on time.

The 8th HL-LHC meeting brought more news for HL-LHC magnets. It gave the opportunity to discuss the advancement of the last tests of the second D1 model produced in KEK in Japan and the development of the corrector magnets at CERN and in Spain (CIEMAT), Italy (INFN) and China (IHEP), with several prototypes already tested.

Furthermore, there were many/ lessons learnt from the installation in the SPS of the test bench housing the DQW (double-quarter wave) crab cavities cryomodule. The construction of the associated infrastructure showed that the objective was reached only because all operations were studied and planned in detail. Without precise planning and a fully devoted team we wouldn’t meet the tight schedule. The cryomodule has showed an  excellent behaviour and all data obtained has been discussed and will be used to improve the design of the LHC cavities.

There was also the occasion to discuss on the first results of the magnesium diboride superconducting link demonstrator (Demo 1) that contains the first 20 kA wires cabled in industry. Meanwhile, as this article is written. Demo 1 has been powered, though in a non-final configuration,with excellent croiygenic and electrical performance confirming the choice illustrated in  the annual meeting that  was focused  to discuss the redesign of the Distribution feedboxes another key element of the cold powering.

The gathering was also the occasion to evaluate if new systems have to be added to the baseline. When discussing on the evolution of the LHC bean dumping system, (LBDS) it was decided the need of a technical review as today looks like a real need. Other options such as the electron lenses of the crystal collimation presented their latest results but will continue to be pursued with the expectation to find the necessary external funding as in-kind contribution

Several decisions were also presented such as the revamping of the existing cryogenic system that  allows to avoid a new cryoplant in point 4 or the optimization of the matching sections and the new remote alignment system that will induce savings in the project while increasing avaibility in operation and reducing the dose to personnel.

There was also time to discuss the advancement of the warm powering and the latest news from the cold diodes that have shown to survive the the  radiation test with HiLumi dose and the results on the shielded beam screen or the LS2 plans for the TANB and the shielding round the experiments.

Finally during a public visit, the HL-LHC collaborators sawthe progress on the civil engineering works, where in that moment the excavations had reached 30 metres at Point 1 and 25 metres at Point 5. The two 80-metre shafts should be fully excavated by the beginning of 2019.

Four days, some 180 presentations to push the technologies developed for the High-Luminosity LHC and beyond.

Maurizio Vretenar (CERN)
Accelerator-Industry Co-Innovation Workshop
15 Mar 2018

Accelerator-Industry Co-Innovation Workshop

Tools and strategies to enhance industry-academia cooperation in the particle accelerator community

Isabel Bejar Alonso (CERN) , Rama Calaga (CERN), Ofelia Capatina (CERN)
From first concept to the SPS: the challenge of the HL-LHC crab cavities cryomodules
13 Dec 2017

From first concept to the SPS: the challenge of the HL-LHC crab cavities cryomodules

Crab cavities will help increase the luminosity of collisions in the High-Luminosity upgrade of the LHC.

Ricardo Torres (University of Liverpool)
How fundamental science is changing our world
27 Mar 2019

How fundamental science is changing our world

Global FCC study discussed benefits of discovery science to society and industry at Symposium “Particle Colliders – Accelerating Innovation”

A new generation of beam screens

When HL-LHC was approved, the vacuum team faced a huge challenge, to create a new generation of beam screens. The LHC has already a beam screen that is already quite unique in its kind, but HL required far more strict characteristics. From one side, tungsten absorbers are integrated to intercept collisions debris leading to  heat load requirements of a factor 50 higher compared with the one for LHC and for another they have much larger aperture, optimized for beam optics, inducing huge Lorentz forces during a magnet quench of around 33 tons per meter per quadrant. A breakthrough was needed.

The shielded beam screen is  a complex octagonal shaped assembly made out of a co-laminated and perforated copper and stainless steel sheet. It is equipped with tungsten blocks laid on the tube and kept in place by means of elastic rings and pins, cooling tubes and thermal links. The design is based on a thermal decoupling between the internal beam screen tube and the absorbers to keep the temperature in a thermodynamically efficient range and on a flexible assembly to ensure the transfer of the Lorentz forces induced in the absorbers to the cold bore tube. To develop the new beam screens, the team had to consider not just the 2D modelling but a full 3D modelling as the beam screen was shielded by tungsten blocks equipped with local copper thermal links.

They also had to use advanced simulation techniques considering all the factors such as the combined thermal and electromechanical behaviour. Several aspects had to be studied in detail as the transfer of heat between the beam screens and the absorber blocks in Tungsten, the cooling circuits or the thermal transfer with the cold bore. "Thermal aspects are extremely challenging points," says Cedric Garion, responsible of the beam screen design, as in this case we are working at 60-80 K and not as for the LHC at the range of 4-20 K.

Since two years the CERN vacuum group has done a systematic campaign to validate its innovative design starting with an 80 cm model to the present 2m long prototype. This campaign has not been easy as during the 6th Annual meeting in 2016 a new requirement was added: the magnet protection scheme was complemented with a novel Coupling-Loss Induced Quench (CLIQ) system which became part of the baseline in addition to the standard quench heaters. From one day to another the new beam screen had to be able to withstand a new type of oscillatory load induced by CLIQ and work in a completely different mechanical regime.

The team reviewed in few months the consequences for the design and reworked the holding systems and the geometry of the Tungsten blocks. In a record time they were ready to test the new prototype able to resist to the new configuration with the new quench protection system.

"This summer was a really exciting moment," says Marco Morrone, one of the engineers involved in the design and in charge of the tests, as we submitted the new beam screen to extreme conditions. In fact, the prototype of the Q1 beam screen was cool down to 1.9k and subjected to currents beyond the ultimate current. The beam screen prototypes withstand magnet quenches and the results obtained were compared with the models giving a perfect fit between the simulations and what was observed.

On the other hand, thermal tests of a beam screen prototype have been carried out and have shown excellent thermal performance of this complex assembly.  A very good decoupling is observed between the absorbers and the beam screen tube, whose temperature is perfectly defined by the helium temperature. In addition, a low heat leak, below 0.5 W/m, has been measured from the massive shielded beam screen to the 1.9 K cold bore tube. These outstanding results are in very good agreement with the estimations obtained by simulations.

To obtain such good results the vacuum group had to innovate in a lot of aspects. For example, the springs on the holding system are done in additive printing. Another real challenge has been the design of the thermal links that at the same time transfer heat, warranty flexibility will resist to extreme forces. Finally the tungsten blocks are just hold to transfer forces to the cold bore. Definitively the beam screen has become a new technological jewel of HL-LHC.

Linn Tvede, Giovanni Porcellana (CERN)
Using CERN magnet technology in innovative cancer treatment
10 Dec 2018

Using CERN magnet technology in innovative cancer treatment

The enormous size of today’s gantries poses constraints on future hadron-therapy facilities.

Chris Edmonds (University of Liverpool)
Tactile Collider
13 Mar 2018

Tactile Collider

Sensory exploration of LHC science for children with visual impairment

Graeme Burt (Lancaster University), Donna Pittaway (STFC), Trevor Hartnett (STFC) and Peter Corlett (STFC)
Daresbury security linac achieves 3.5 MeV
26 Jun 2018

Daresbury security linac achieves 3.5 MeV

Compact aviation cargo scanning linac successfully commissioned at STFC Daresbury Laboratory.

Power tests of HL-LHC quadrupole

Fig. 1:

In July, the fourth short model of the Nb3Sn quadrupole for the HL-LHC interaction regions was tested in SM18. This is the first magnet with the final Bruker-OST Restacked Rod Process (RRP®) conductor, with 108/127 layout, which shall be used for eight out of ten magnets of this series. As the third model tested one year ago, this was fully manufactured and assembled in CERN’s laboratory 927.

The magnet reached nominal current (7 TeV operation) with one quench, and ultimate current (7.5 TeV operation) after five quenches. “It has been the fastest training of the short models tested so far, approaching the performance of HQ, the magnet developed in the 2000’s by LARP that is the father of MQXF” – says J. Carlos Perez, in charge of the 927 magnet laboratory. The most relevant parameter for operation is the training after thermal cycle, since it provides an indication of the magnet behavior after installation. For this model no quench was required to reach 7.5 TeV operation, proving a perfect memory of the training.

Fig.2:

Magnetic measurements confirmed a low value of the first order harmonics, already observed in the US prototype and in the third short model. This dodecapole component is 0.05% of the main field, whereas it should be not larger than 0.01%. A fine-tuning, foreseen in the initial design shall be carried out to recenter this unwanted harmonic around zero.  This will be done through a modification of shims around the coil by a mere 0.125 mm.

The coils of the fifth and last short model have been manufactured, and the magnet, named MQXSF6, will be assembled in autumn. These coils are made with the final Bruker-EAS Powder-In-Tube (PIT) conductor, which will be used for one prototype and for two series magnet. “The MQXFS6 magnet will complete the short model programme of the HL-LHC Nb3Sn quadrupoles” – says G. de Rijk, in charge of the MSC/MDT section leading the short models and the correctors of HL-LHC – “but we remain ready to continue further work on short models, should we need additional information to be fed in the full size magnets”. The construction of the first full size CERN prototype MQXFBP1 is ongoing, and the second US prototype MQXFAP2 is undergoing cool-down for a test to start in a few weeks in BNL.

James Robert Henderson (ASTeC)
Intelligent Control Systems for Particle Accelerators
9 Mar 2018

Intelligent Control Systems for Particle Accelerators

Artificial Intelligence paves way for entirely new ways to operate big science facilities

Philippe Lebrun, JUAS Director
25th edition of Joint Universities Accelerator School
13 Mar 2018

25th edition of Joint Universities Accelerator School

Twenty-five years of training accelerator scientists and going from strength to strength

Outi Heloma (CERN), Isabel Bejar Alonso (CERN)
Education for innovation in Hilumi and FCC
6 Mar 2018

Education for innovation in Hilumi and FCC

What’s in it for innovators in Hilumi and FCC? Twenty young researchers interested in innovation and entrepreneurship participated in this two-day course.

A big step towards the superconducting magnets of the future

Last April, the FRESCA2 dipole magnet reached a field of 14.6T. This field value sets a new world record for dipole magnets with a free aperture, and breaks the old record established in 2008 of 13.8T by LBNL with the HD2 dipole magnet.

The development of magnets with fields beyond 10T started in Europe in 2004 with the FP6-CARE-NED project where the basic technologies were developed and specifically the Nb3Sn conductor which is the workhorse for the HL-LHC 11 T magnet, the LHC luminosity upgrade programme and baseline option for the more powerful 16T magnets for the Future Circular Collider study.

“FRESCA2 has already played an important role in the development of the new magnets for the High Luminosity LHC and will soon help develop the next generation of magnets." says Gijs de Rijk, head of the FRESCA2 programme.

The FRESCA2 dipole magnet design and construction was started in the framework of the FP7-EuCARD-HFM project in 2009 and has been co-financed by HL-LHC. The FRESCA2 magnet is much larger than a LHC magnet, measuring 1.5 m in length and 1 m in diameter. This allows the magnet to have a large aperture, measuring 10 centimetres, so that it can house the cables being tested, as well the sensors to monitor their behaviour. 

The FRESCA2 magnet before the start of the tests. (Image: Maximilien Brice/CERN). 

The magnet is the outcome of a successful collaborative effort between CERN and CEA-Saclay. The technology developments for FRESCA2 were essential for the new Nb3Sn magnets of HL-LHC. Formed by the superconducting niobium-tin compound and cooled to 1.9 kelvin (-271°C), it had already reached a field of 13.3 teslas in August 2017. Then, with a modification of the mechanical pre-stressing, it started a new series of tests in April before reaching its record intensity.

FRESCA2 will also be used to test coils formed from high-temperature superconductors. The goal is to test not only the maximum electrical current but also study in depth the effects of so high magnetic fields and the behaviour of the coil. Results from these measurements feed current efforts to design high-field magnets for future energy-frontier colliders. 

The magnet was tested to the nominal operating field, and achieved 13.3T in August 2017 after a very rapid training of 5 quenches. As a second step, the mechanical preload was increased and the magnet was retested in April 2018 to explore the ultimate operating limit. In this configuration FRESCA2 reached a maximum bore field of 14.6T at a temperature of 1.9K with additional 6 training quenches. The tests are currently being performed in the new purposely built test cryostat of the SM18 cryogenic test station at CERN.

This result is a major milestone in the progression towards high field accelerator magnets beyond HL-LHC. The future of FRESCA2 is to provide background fields for tests of cables and small coils, a new facility that will provide unique test capabilities.

Isabel Bejar Alonso (CERN)
A new step for High-Luminosity LHC
10 Dec 2018

A new step for High-Luminosity LHC

...a worldwide project to enhance LHC potential to discover. The 8th HL-LHC Collaboration Meeting took place last October, in Geneva.

Romain Muller (CERN)
ARIES first annual meeting in Riga
3 Jul 2018

ARIES first annual meeting in Riga

One year after the Kick-off, where does the project stand?

Livia Lapadatescu
Simon van der Meer Award
24 Mar 2019

Simon van der Meer Award

Apply now to Simon van der Meer Early Career Award in Novel Accelerators! Deadline: 27 May 2019

Groundbreaking for the HL-LHC civil engineering work

The groundbreaking ceremony for the launch of the civil engineering works took place on Friday 15 June 2018 with the presence of the CERN management, the French and Swiss Authorities and the CERN Council.

"The High-Luminosity LHC will extend the LHC's reach beyond its initial mission, bringing new opportunities for discovery, measuring the properties of particles such as the Higgs boson with greater precision and exploring the fundamental constituents of the universe ever more profoundly," mentioned CERN's Director-General Fabiola Gianotti during the ceremony.

The increase in the number of collisions in HL-LHC, means more observations of rare phenomena and more chances for discovery. As an example, the upgrade will increase the number of Higgs bosons that can be produced by the LHC from 1.2 million to 15 million.  The HL-LHC data will enable the improvement of the precision on Higgs boson couplings by a factor of 2 to 3 with respect to the previous LHC running. 

Two contracts for the civil engineering works have been adjudicated in March 2018 to a consortium MARTI TUNNELBAU, MARTI ÖSTERREICH and MARTI DEUTSCHLAND for the Point 1 works and to IMPLENIA SCHWEIZ, BARESEL and IMPLENIA CONSTRUCTION consortium for Point 5. At each point, the work consist of the construction of an access shaft, a service cavern and underground galleries as well as five new surface buildings. The site mobilization has started on both Points. The shaft excavations will start end of June 2018 and will be completed before the end of the year.

The excavations will be performed with electrical road-headers to minimize the vibration level on the LHC machine and its detectors, which will be in operation with beams during this period. In parallel, the two consultants are progressing in the detailed design of underground structures. The underground excavation works will be completed by mid 2020 during the next long shut-down and the works, including surface buildings, will be completed by Autumn 2022.

The effect of the first Civil Engineering work on the site surface on the proton losses in the LHC. One can clearly recognize the 22Hz perturbation of the excavation equipment

After completion of this major upgrade, the LHC is expected to produce data in high-luminosity mode from 2026 onwards. By pushing the frontiers of accelerator and detector technology, it will also pave the way for future higher-energy accelerators. “Audacity underpins the history of CERN and the High-Luminosity LHC writes a new chapter, building a bridge to the future,” said CERN’s Director for Accelerators and Technology, Frédérick Bordry. “It will allow new research and with its new innovative technologies, it is also a window to the accelerators of the future and to new applications for society.

 

Isabel Bejar Alonso (CERN) , Rama Calaga (CERN), Ofelia Capatina (CERN)
From first concept to the SPS: the challenge of the HL-LHC crab cavities cryomodules
13 Dec 2017

From first concept to the SPS: the challenge of the HL-LHC crab cavities cryomodules

Crab cavities will help increase the luminosity of collisions in the High-Luminosity upgrade of the LHC.

Jim Clarke (STFC)
CLARA Update: First Accelerated Beam
8 Dec 2017

CLARA Update: First Accelerated Beam

UK’s Free Electron Laser Test Facility reached another significant milestone.

Nicholas Sammut (University of Malta)
Setting up a South-East Europe International Institute for Sustainable Technologies
2 Mar 2018

Setting up a South-East Europe International Institute for Sustainable Technologies

CERN’s model of ‘science for peace’ is being adopted in the set up of a new research infrastructure: The South-East Europe International Institute for Sustainable Technologies (SEEIIST).

World’s first crabbing of a proton beam

The first test of superconducting crab cavities to rotate a beam of protons was performed on 23 May using a beam from CERN’s Super Proton Synchrotron (SPS) accelerator. These cavities are a key component of the High-Luminosity Large Hadron Collider (HL-LHC). A total of 16 such cavities will be installed in the HL-LHC – eight near ATLAS and eight near CMS.

Figure 1: DQW Crab Cavity Prototype being assembled at CERN.

In the LHC and HL-LHC, the two counter-rotating bunches collide at an angle at each collision point of the experiments. When installed at each side of the ATLAS and CMS experiments, the crab cavities will “tilt” bunches of protons in each beam to maximise their overlap at the collision point thus increasing the luminosity. The crab cavities are expected to increase the overall luminosity by 15 to 20% and improve the quality of data collected by the experiments. Crab cavities were already used in the KEKB collider in Japan for electrons and positrons, but never with protons, which are more massive and at significantly higher energies.

Figure 2: The Crab Cavity Cryostat installed on a movable table in the CERN SPS.

The first crab cavity prototypes were manufactured at CERN in 2017 in collaboration with STFC and USLARP. The cavities were assembled in a cryostat and tested at CERN-SM18 facility prior to its installation into the SPS. The cavities were installed in the SPS accelerator during the last winter technical stop for machine development studies in the SPS.

Figure 3: Images a bunch in the CERN SPS for 2 different voltage settings in the Crab Cavities. Left without voltage and deflection. Right with 1MV voltage and deflection.

 

The first beam tests were performed on 23 May at 4.5 K with a single proton bunch accelerated to 26 GeV and with a bunch intensity of 0.2-1×1011 p/b. The crab cavities were powered to about 10% of their nominal voltage in the first tests and later increased to up to 50% limited mainly due to vacuum rise. The “crabbing” was observed using head-tail monitor with large enough bandwidth and resolution to observe the intra-bunch orbit induced by the crab cavities. These tests mark the start-up of a unique facility for testing superconducting cavities on a high-current, high-energy proton beam. The results mark an important milestone to prove the feasibility of using such cavities with long proton bunches for increasing the luminosity in the HL-LHC.

In the coming months, the cavities will be commissioned to their nominal temperature of 2K and slowly ramp the kick voltage to their nominal voltage of 3.4 MV. During the rest of the year, the cavities will undergo a series of tests to fully validate their operation for a robust operation in the HL-LHC era.  

Shane Koscielniak (TRIUMF), Tor Raubenheimer (SLAC)
Highlights from IPAC ’18
28 Jun 2018

Highlights from IPAC ’18

A selection of highlights from the results presented during IPAC18

Alexandra Welsch (University of Liverpool) , Panagiotis Charitos (CERN)
Marie Skłodowska-Curie's legacy inspires young scientists
11 Dec 2017

Marie Skłodowska-Curie's legacy inspires young scientists

A multi-site event to celebrate twice Nobel Prize winner’s 150th birth anniversary held in Geneva, Munich and Liverpool

Ricardo Torres (University of Liverpool)
The Tale of Two Tunnels
10 Dec 2018

The Tale of Two Tunnels

Liverpool will be turned into a particle accelerator exhibition.

Ensuring safer operation at higher luminosities

The TDI (Target Dump Injection) is a beam-intercepting device installed on the two injection lines of the LHC (Large Hadron Collider) to protect the superconducting elements of the machine during injection in case of a malfunction of the injection kickers.

Due to the higher bunch intensities and smaller beam emittances expected in the HiLumi-LHC phase, and following the operational experiences of the TDI, a complete revision of the design has been performed. The result of this reengineering work is the TDIS (Target Dump Injection Segmented),a key element for the safe operation of LHC at high luminosity.   

The major changes that can improve the reliability of this component are:  

  • A more efficient cooling circuit better integrated in the jaw, in order to dissipate the beam induced Radio Frequency (RF) heating.
  • A more robust and reliable motorization system and fixation points to contain and guide any possible deformation.
  • A new geometry with smaller cavities, better contacts and RF fingers to damp as much as possible the HOM.

Several other aspects were taken in consideration while reengineering the TDIS and as the letter “s” indicates, the new design is segmented! The new modular design will simplify the assembly procedure, the installation, the maintenance and will improve the robustness, setup accuracy and operational reliability of the system.

The new injection dump consists of three modules, independently movable, of equal length (each ~1.6 m long) hosting different absorber materials: two modules with low-Z absorbers blocks (graphite R4550) and one with a sandwich of higher-Z materials (Ti6Al4V and CuCr1Zr). A careful choice of the material ensures that no damage occurs in the machine as well as that the TDIS will cope with all direct beam impact conditions. Impedance, e-cloud and radiological aspects were also taken into account in the final design.

After several years of engineering and specification work, the efforts now move to the procurement of materials and components for the assembly of the TDIS prototype. As of today, most of the components required to build-up one TDIS prototype (plus one module for validation purposes at CERN’s HiRadMat testing facilities) are in the manufacturing phase, although some key elements have already been produced. Amongst them, the absorbing blocks and one back-stiffener of a jaw to be installed in the HiRadMat module. This stiffener is a structural component intended to ensure the requested flatness of the jaw’s surface exposed to the beam and is produced out of TZM (Molybdenum alloy) in order to withstand the high thermomechanical loads induced in case of beam impact.

3D view of the HiRadMat module that will be assembled in 2018 along with a full TDIS prototype (Image credit: Luca Gentini). 

Finally, it should be noted that the aforementioned manufactured parts are currently going through the qualification process at CERN. Ultrasonic inspection and metrology analysis are so far completed and the next stage is vacuum testing to confirm the compatibility of the graphite blocks and the TZM back-stiffener with an ultra-high vacuum environment.

The start date for the assembly process of the prototype and the HiRadMat module is planned for early June, right after the arrival of the vacuum vessels.

James Robert Henderson (ASTeC)
Intelligent Control Systems for Particle Accelerators
9 Mar 2018

Intelligent Control Systems for Particle Accelerators

Artificial Intelligence paves way for entirely new ways to operate big science facilities

Rama Calaga (CERN)
World’s first crabbing of a proton beam
26 Jun 2018

World’s first crabbing of a proton beam

The first test of the HL-LHC crab cavities to rotate a beam of protons was performed last month at CERN.

Alexandra Welsch (University of Liverpool) , Panagiotis Charitos (CERN)
Marie Skłodowska-Curie's legacy inspires young scientists
11 Dec 2017

Marie Skłodowska-Curie's legacy inspires young scientists

A multi-site event to celebrate twice Nobel Prize winner’s 150th birth anniversary held in Geneva, Munich and Liverpool

A new step towards successful MgB2 superconducting coils

On 7th March the INFN-LASA laboratory completed the construction and successfully tested a superconducting coil in MgB2 (Magnesium di-Boride based conductor) to be used in a high order corrector magnet. Development of MgB2 coils for a Round Coil Superferric Magnet corrector was launched in the framework of the HL-LHC project IR magnets. This design, proposed in the 70s by Russian scientists, allows to create any multipole with the same round coil through a three dimensional shaping of the iron; the low curvature radius of the coil allows using MgB2 superconductor. 

Application of this design to the HL-LHC high order correctors started in 2014 by our late lamented Giovanni Volpini with CERN support. Computations showed that this option had a lower efficiency in terms of longitudinal space, and therefore the classical superferric option with Nb-Ti and standard two dimensional iron shaping was retained; INFN-LASA built three correctors based on this design in the past two years, and two more types are being built in collaboration with industry. Nonetheless, the MgB2 RCSM prototype magnet has remained in the development line to explore the manufacturing aspects of this design, and to have a MgB2 corrector available for high energy accelerators, a prima for this technology.

A single coil, wound with conductor produced by Columbus Superconductors (Genova), was tested in LASA without the iron yoke; this coil is the active part of the RCSM magnet, which will be assembled and tested in September 2019. The coil, cooled at 4.2 K with liquid helium, reached without any training quench the specification current (“ultimate current”, 160 A), passing also the stability test of one hour at the ultimate current. The coil was then energized to larger currents to investigate the limiting current, which resulted in 243 A; this is 73% of the intersection of the load line with the critical current for virgin, not-degraded, conductor. It should be noted that this current limit was reached without intermediate quench (no training).


Image Credit: INFN/LASA

“The test result is beyond our expectations,” says Massimo Sorbi from INFN-LASA. “MgB2 virgin conductors are very prone to degradation when they are wound and manipulated with even better procedures used for the other common superconductor magnets based on NbTi. Our cryogenic test was also complemented with the measurement of the thermal contraction of coil (literature is lacking of this data regarding MgB2 coils), which will enable a better design of the mechanical structure for the final magnet.” “This is a relevant technological spin-off of the HL LHC project”, says Ezio Todesco, in charge of HL-LHC IR magnets, “enabled by the synergy between INFN-LASA and CERN”.


Image Credit: INFN/LASA

Joseph Piergrossi (European XFEL)
New solutions for challenges among complementary light sources
8 Oct 2018

New solutions for challenges among complementary light sources

EUCALL developed strategies for laser-based and accelerator-based sources of UV/X-ray light.

Romain Muller (CERN)
ARIES first annual meeting in Riga
3 Jul 2018

ARIES first annual meeting in Riga

One year after the Kick-off, where does the project stand?

Panagiotis Charitos
FCC collaboration publishes its Conceptual Design Report
28 Mar 2019

FCC collaboration publishes its Conceptual Design Report

FCC study publishes a conceptual design report demonstrating the feasibility of the different options explored for post-LHC circular colliders.

From first concept to the SPS: the challenge of the HL-LHC crab cavities cryomodules

The first concepts of the HL-LHC crab cavities started more than 10 years ago. They were the fruit of the discussions of a young physicist at BNL and a beam dynamics expert at CERN. The concept was not new but using it for the LHC implied a long journey of technological challenges.

The distance between the LHC beams required a new RF concept for particle deflection with a novel shapes and significantly smaller in size than conventional RF cavities. The challenge was taken with enthusiasm by the RF community resulting no less than 10 concurrent designs from RF experts across three continents. In 2013, three designs were considered to be the most adapted to the LHC and became ready for the development of a proof of principle. While this may sounds like a moment of fierce competition, in reality it showed the spirit of cooperation towards a common goal among the members of our community. The results of the RF tests of the Double Quarter Wave (DQW), the RF Dipole (RFD), and the four Rod (4R) were highly promising and analysed by an international panel in 2014 that recommended to focus the efforts on the first two designs to make a full validation of the cryomodule in the CERN’s SPS.

One of the crab cavities that will be used in the HL-LHC (Image Credit: CERN)

The entire community concentrated on the two designs and on the development of the concept of all the other required components of the cryomodule that should host the cavities. The effort that had already started in 2013 by CERN required the knowledge, experience and imagination of the collaboration.

In fact, 2015 became a decisive year that started with a collaborative design thinking of the most innovative components. Among them we can highlight the frequency tuning system, the helium tank and the RF lines, all of which required inspiration beyond the conventional wisdom to adhere to the strict needs of HL-LHC. There is a global consensus on the fond memories of the design phase in 2015, wild enthusiasm and collaboration. Effectively, during this extremely critical period every team contributed to the design before concentrating on the detail development of the different components. The result was as harmonic as the sound of a good symphonic orchestra. A robust design that was flexible to be used for the test of the cryomodule at the SPS, easily adaptable for the LHC and that could be transferred to the industry for the series production.

Today the first cryomodule is finished and under cold test without any delay on the manufacturing plan that was prepared more than two years ago. A plan that at that moment was considered almost impossible. Today, the infrastructure in the SPS is ready and just waiting for the cryomodule installation. The hard work of these last 5 years of engineers and physicists from US, UK and CERN will reap the benefits of their hard efforts.

In the meantime, the team is thinking about the future. In December the industrial contract for the series production of the cavities under CERN’s responsibility will be adjudicated. The global collaboration will be further enlarged with discussions with laboratories in Canada and in Japan willing to contribute to the construction of the cryomodule.

A global effort and we hope a global success!

Daniela Antonio (CERN)
The future of communication and outreach for accelerators
10 Dec 2018

The future of communication and outreach for accelerators

Members from the accelerator communication community gathered at CERN for a workshop.

Alexandra Welsch, Samantha Colosimo, Javier Resta López (University of Liverpool)
Accelerating Learning
8 Oct 2018

Accelerating Learning

Summer events held at CERN boost knowledge and collaboration. The events were coordinated by the QUASAR Group.

Miguel Fernandes (University of Liverpool/CERN)
Measuring AD beam intensity with a Cryogenic Current Comparator
8 Oct 2018

Measuring AD beam intensity with a Cryogenic Current Comparator

New system can measure the average current of bunched and coasting beams.

A bright future for HL-LHC

The 7th HL-LHC Annual meeting in Madrid took place in November. An intensive week to review the progress done during 2017 and the objectives for 2018. The HL-LHC project is moving to construction phase. The hardware models as well as the prototypes of the equipment in their final configuration are under construction or currently tested. 

In 2017, the HL-LHC project achieved a number of key milestones. The first crab cavity prototypes built in the US were successfully tested by LARP collaboration that is transforming into US-HL-LHC AUP (Accelerator Upgrade Programme) and the full cryomodule containing the crab cavities built at CERN was successfully tested at 2K; just in time to be integrated in the SPS during the winter where their performance will be studied next year by using a beam from the SPS.

The first low impedance collimators were tested and characterized in the LHC machine together with the crystal collimation concept (not in HL-LHC baseline). The test of the first long prototype of the MQXF quadrupole, manufactured by US-LARP-AUP for the new low-b HL-LHC insertions has just started in BNL. The first results are expected in February. Moreover, the construction of the first 11 T magnet and DS collimator and the test of the first long SC link, all manufactured at CERN, were among the highlights of the HL-LHC week.

In addition, the successful implementation of the ATS optics (devised for the LHC upgrade) and the tests of the full detuning operation mode of the LHC RF system during the LHC operations: are two key ingredients that increased the performance of the LHC in 2017 and pave the way for its high-luminosity upgrade.

This year we had an international review that validated technically the e-lenses and equipment that could be part of the HL-LHC baseline. Finally, we have concluded on the interface between the machine and the experiments. These above developments in all these different fields show how the HL-LHC project is making progress towards final implementation.

There are several other relevant milestones achieved by the HL-LHC collaborations. The short model of the D1 reached ultimate current in KEK. The first octupole and decapole prototypes also went beyond the ultimate current in INFN LASA. The D2 model construction in the industry is well advance, a collaboration led by INFN. Finally the short mechanical model of the nested orbit corrector and the first coil were also accomplished this year in CIEMAT

Procurement for HL-LHC

2017 was also the year for the preparation and adjudication of some of the bigger contracts of HL-LHC. The tender for civil engineering works for Point 1 and Point 5 (including large excavation and construction work) was announced in July and is presently under final evaluation. The contract adjudication will be done in March and the first civil works for HL-LHC are expected to start in summer 2018.

This year has also seen the first tender for the collimators that will be installed during the next Long shutdown 2 (LS2). The adjudication in December will ensure their delivery on time for their installation before mid-2020. In parallel to the construction of the crab cavities cryomodule to be tested in the SPS in 2019, the tendering of the Jacketed Crab Cavities DQW type has been placed. The contract will be adjudicated this December and will be complemented by the work done by AUP on the RFD type crab cavities. Also in the field of the 11T magnets, HL-LHC adjudicated the tender for the construction on CERN site of the coils for the 11T dipole. An industrial service contract where skilled employees will use the facilities built at CERN and that were used to build the first models and prototypes of the 11T dipole.

The next challenge for HL-LHC is to ensure a coherent integration lay-out that will meet the constraints imposed by the lay-out of the civil engineering and the preparation of a first version of the installation plan. Meanwhile, the optimization of the design and construction of the components is in progress. “As the window to keep various options in the planning narrows we need to work hard to make final choices for the implementation of an industrial construction roadmap” says Lucio Rossi HL-LHC Project Leader.  

The second HL-LHC Collaboration Board also took place during the HL-LHC week. HL-LHC steadily becomes a global project. 18 HL-LHC Collaboration Board members and 11 collaboration partners with R&D contributions work together with CERN to make possible HL-LHC. The gathering in Madrid showed the interest of the community on the development of the HL-LHC technologies with multiple proposals for in-kind contributions.

To learn more about the HL-LHC Project read the Technical Design Report (TDR) https://e-publishing.cern.ch/index.php/CYRM/issue/view/40 and or brand new website .

 

*AUP HL-LHC Accelerator Upgrade Project (BNL, FNAL, LBNL and SLAC)

Ruben Garcia Alia (CERN)
RADECS 2017: radiation resistance for electronics
7 Dec 2017

RADECS 2017: radiation resistance for electronics

Addressing radiation effects with RADECS and RADSAGA

Isabel Bejar Alonso (CERN)
QUACO Phase-3 starts now
10 Dec 2018

QUACO Phase-3 starts now

Following the competitive tender for phase-3, only two solutions could be awarded a work order. Three were evaluated and considered promising.

Panos Charitos (CERN)
Interview with Mariana Mazzucato: Bridging Research with Innovation
25 Mar 2019

Interview with Mariana Mazzucato: Bridging Research with Innovation

Prof. Mariana Mazzucato on innovation and the concept of "missions".