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WP1 Collimators

The stored energy in the LHC beams is very large, 360 MJ for the nominal machine and a factor of 2 higher for HL-LHC, and the superconducting magnets are very vulnerable to heating from any beam losses. The operation of the machine has always depended on a sophisticated multi-stage collimation system to remove large amplitude halo particles, and the increased currents in the upgraded LHC mean that this critical system must receive a major upgrade and redesign.  

 The HL-LHC-UK team (Manchester, RHUL, Huddersfield) will build on the strong simulation and theoretical scattering expertise with a continued effort on simulation and participation in measurement of loss maps, wand extending the scattering models developed in HiLumi-LHC. The team will exploit the codes MERLIN and Sixtrack to study and optimize collimation system performance for HL-LHC, including simulation and measurement of the run 2 configurations and the simulation of the HL-LHC configurations. The team will work to develop and support the MERLIN code, exploiting it fully for the machine upgrade.

The simulation and halo control effort will be applied to the study of novel collimation schemes, which aim to control the HL-LHC halo with non-conventional control techniques. The conventional layout adopted  for the LHC might be extended in HL-LHC to these novel collimators, to provide enhanced levels of halo control and collimation performance. HL-LHC-UK will bring the university skills, expertise and codes to this challenging problem, studying the hollow electron lens system and crystal collimation system for the upgraded machine. This will include studies of the beam dynamics of the scheme and contribution to novel collimation experimental studies. 

HL-LHC-UK will also focus on two new hardware areas. The Manchester team will  explore the use of  coatings for collimators through simulation, and perform a measurement of impedance of a sprayed in the laboratory.  We will also develop a collimator with real-time integrated sensors and actuators, delivering a hardware prototype and drawing on the precision engineering expertise at the University of Huddersfield. The result will be a prototype collimator that can actively compensate for the effects of adverse heating on jaw geometry, such that the straightness and flatness of the jaw should be within the current target specification for TCS collimator. 


WP2 Crab Cavities

The LHC brings its beams into collision at a slight angle so they only cross at designated interaction points. When the beam size is reduced for HL-LHC the overlap of the beams when crossing at this angle causes a reduction in the number of collisions, as can be seen in Figure 1. To avoid this special “crab” cavities are used to rotate the beam before and after the two main interaction points. These are special electromagnetic cavities, operating at radio frequencies, that apply a time varying electric and magnetic field to kick the head and tail of the bunch causing it to rotate slightly. Due to the high fields required the cavity has to be superconducting so that the high surface currents in the walls do not generate excessive heat. Crab cavities have only been used once before, at KEKB in Japan. The cavities there are too big for the LHC as the beams are too close together so special compact crab cavities are needed for LHC. Three prototype designs were manufactured and tested at CERN, shown in Figure 2. Two of these have been selected for testing in the SPS accelerator, as the first test of crab cavities on proton beams.

The compact crab cavities are a collaboration between CERN, HL-LHC-UK and the US LHC American Research programme. HL-LHC-UK’s effort on the crab cavities involves Lancaster University, The University of Manchester, Liverpool University and the Science and Technology Research Council (STFC). The UK team are involved in the manufacture and assembly of the cryomodule prototype, testing of these structures in the CERN SPS accelerator, and simulating how these structures might behave in the LHC.


WP3 Diagnostics

The LHC is equipped with an extensive array of beam instrumentation that has played a major role in commissioning, rapid intensity ramp-up and safe and reliable operation of the accelerator. For the HL-LHC, new diagnostic techniques must be developed to meet key challenges presented by the high-intensity beams. The development of two new diagnostic technologies form the two tasks of this work package: electro-optic beam position monitor and gas jet beam monitor:

1) An critical change at the HL-LHC is that the bunches will be rotated by the crab-cavities before and after the interaction regions, so that the bunches collide head-on to reduce the overlap area and maximize the luminosity.  Optimising the performance of the crab-cavities at the HL-LHC requires new instrumentation that can perform intra-bunch measurements of transverse position of particles within each 1ns bunch and can detect intra-bunch instabilities on a turn by turn basis.
A novel, compact beam diagnostic to measure the bunch rotation is under development, based on electro- optic crystals, which have sufficient time resolution (<50ps) to monitor intra-bunch perturbations. The Electro-Optic-Beam Position Monitor (EO-BPM) uses two pairs of crystals, mounted on opposite sides of the beam pipe, whose birefringence is modified by the electric field of passing charged particle beam. The change of birefringence depends on the electric field which itself depends on the beam position, and is measured using polarized laser beams. The rapid optical response enables high bandwidths of 6-10 GHz.

A collaboration between Royal Holloway, University of London and CERN Beam Instrumentation group is developing a prototype EO-BPM, that is undergoing tests in the CERN SPS for validation of the concept.

2) The non-invasive measurement of both the beam size and the beam halo are also high priorities for the beam diagnostics work package of the HL-LHC project. A candidate for non-destructive monitoring is a gas monitor where the particle beam interacts with either residual gas particles or a dedicated supersonic gas jet target shaped into a pencil or curtain, causing either ionization or fluorescence. If no magnetic fields are present the ions can be collected by means of an electric field, imaged onto a position-sensitive detector and provide information on the beam profile; alternatively the light emitted by the gas particles can be detected with photon detectors providing a full 2D beam image. If a suitable design is chosen the number of particles from the primary beam interacting with the gas is negligible compared to the number of particles in the beam and the monitor can be considered as non-invasive.
A collaboration between the University of Liverpool and the CERN Beam Instrumentation group is developing a prototype gas-jet monitor, which has been installed at the Cockcroft Institute for test and optimisation of the performance.



WP4 Cold Powering

HL-LHC Cold Powering concerns with delivering up to 200kA to the upgraded magnets in the intersection regions and matching sections using novel DC superconducting links (SC-LINK) operating at temperatures above 4.2K. The WP4 of HL-LHC-UK is contributes to the CERN’s HL-LHC cold powering workpackage WP6a, primarily focusing on the “electrical transfer and cryostats”.

The tasks cover the study of the thermal and electrical performance of the multi-circuit superconducting long transfer line, cooled by supercritical helium, both in steady state and in transient conditions. Different types of advanced conductors are analyzed - MgB2, BSCCO 2223 and YBCO - as well as different types of coolants – liquid helium, supercritical helium in a variable temperature range and liquid nitrogen. The study of heat transfer in supercritical helium will be supported by experimental tests. The effect of the electrical insulation around the cables on the heat transfer is analyzed. Quench propagation in superconducting cable systems cooled by supercritical helium is studied with the final goal of identifying the requirements for the protection of long multi-circuit high-current cables. The aim is to propose quench protection and detection strategies to avoid any degradation. The study of the behaviour during restive transition includes the analysis of potential thermal and/or electrical interference between cables belonging to different circuits and incorporated in the same cryogenic envelope. Experimental work will be needed for the validation of the theoretical modelling. Modelling codes will be elaborated for the analysis of the thermo-electrical performance.

The task includes the conceptual design of a cryostat optimized for the operation of the current leads feeding via the superconducting transfer line the magnet system. SOTON will lead this activity, with contributions from CERN.

Reports, papers and talks

Milestone and Deliverable Reports
No. Work Package Description  
M1.1 WP1

HL-LHC loss optics with MERLIN
Setting up the optics for the low beta* HL-LHC configurations in MERLIN, and checking beta functions, dispersion, beta* and phase advances.

M1.2 WP1

First running of loss scenarios
Initial computing the loss maps in the machine for the HL-LHC machine, demonstrating the applicability and accuracy of the code to CERN.

M1.3 WP1

Study impact of scattering models
As a precursor to the project we developed vert accurate elastic and single diffractive differential cross-sections. The impact on loss maps, loss patterns in the arc and potential measurements to differentiate the models will be analyzed.

M1.4 WP1

Profile the MERLIN code for speed


M1.5 WP1

Initial run 2 loss map data-taking and analysis
The loss patterns taken during dedicated MDs in run 2 are crucial to benchmark computational models. Data from run 2 (6.5 TeV) will be analysed and compared to data to check the models work.

M1.6 WP1

Initiate development of novel collimation scheme tools and layout


M1.7 WP1

Contribute to novel collimation experimental programme


M1.8 WP1

Begin chromaticity and off-momentum loss studies


M1.9 WP1

Calculate the impedance reduction in CST Microwave studio with and without a realistic novel coating layer.


M1.10 WP1

Produce a test collimator and coat with a Graphene layer


M1.11 WP1

Measure the surface conductivity of the coated collimator (if relevant)


M1.12 WP1

Create accurate FE models based on existing LHC secondary collimator design.


M.13 WP1

Determine sensor and actuator functional specification based on simulations of jaw dis-tortion using agreed beam interactions.


M1.14 WP1

Building of standalone prototype and validation of positioning accuracy and repeatability


M1.15 WP1

Validation of novel collimator jaw straightness under various conditions.


M2.1 WP2

HOM coupler testing plan and construction of required infrastructure in order to test at low power. Plan will include low power coupler measurements, high power conditioning, vertical tests on the cavity, horizontal tests and SPS testing.


M2.2 WP2

SPS Cryomodule RF and cryogenic horizontal testing at high power in SM18 complete and cavity installed in SM18.


M2.3 WP2

SPS Cavity and Cryomodule beam testing complete. This includes testing of HOM couplers, impedance, detuning, crabbing and the LLRF system.


M2.4 WP2

Pre-series RFD cryomodule design review complete to ensure manufacturing readiness for of long lead items, which include OVC and some tooling. On completion this will allow drawings to be released.


M2.5 WP2

Simulate using RF system models and beam codes to report on beam and luminosity effects of the new half detuning LLRF scheme and effects that feedback to the Crab Cavity LLRF.


M3.1 WP3

Installation of a prototype EO-BPM in the SPS. Includes BPM body with opposing pick-ups containing LiNbO3 eo-crystals, illminated and readout via remote controlled fibre-coupled polarization optics.


M3.2 WP3

Design of an EO pick-up for LHC. Includes calculated electro-optic response of pick-ups to electro-magnetic simulation of passing LHC bunch.


M3.3 WP3

Installation of a prototype EO-BPM in the LHC. Dependent on results of SPS tests, a EO-BPM prototype with a modified opto-mechanical design would be installed suitable for measurements with LHC bunch parameters.


M3.4 WP3

Installation of a gas-jet monitor on the e-beam test stand. A gas-jet monitor established at the Cockcroft Insititute, with a new electron gun, and a BIF monitor for comparitive studies with the IPM, in terms of signal intensity, constrast and resolution.


M3.5 WP3

Design of a gas-beam monitor for HL-LHC. The mechanical design of the second prototype in collaboration with CERN and Liverpool. 


M3.6 WP3

Prototype gas-jet monitor available. The first two setups will address all questions linked to the final design. A third setup specified for integration with the HL-LHC will be commissionied in the final year of the project.


M4.1 WP4

Definitions of splice configurations and test plan: Define the splices between SC-Link and LTS/HTS in DFX/DFHX according to the finalised magnet circuit for HL-LHC. Establish accordingly a plan for testing the splice samples.


M4.2 WP4

Completion of splice tests: The test plan of M4.1 executed.


M4.3 WP4

DFX Concept designs completed: The conceptual design of DFX fulfilling the function requirements proposed and adopted by WP6a of CERN HL-LHC.


M4.4 WP4

DFX mock-up components manufactured: A crucial step towards DFX production, key components mock-ups of DFX will be manufactured for debugging their design, manufacturability and assembling tolerance. 


M4.5  WP4

Start of stability and distributed sensing tests: commencing the development of a novel quench protection using distributed optical sensing.


M4.6 WP4

Start of DFX components manufacturing


M4.7 WP4

Preseries FDX assembled: fulll mechanical assembly of DFX at SOTON, ready for initial cryogenic tests.


D1.1 WP1

HL-LHC loss map analysis using MERLIN and upgraded scattering physics.
A report on the impact of scattering models on the HL-LHC loss maps, with the new UK-produced elastic and single diffractive cross-sections.

D1.2 WP1

Analysis of loss map measurements in run 2 relevant for HL-LHC
The loss patterns taken during dedicated MDs in run 2 are crucial to benchmark computational models. Data from run 2 (6.5 TeV) will be analysed and compared to data to check the models work.

D1.3 WP1

Modeling of collimation system design for novel collimation concept, including experimental verification


D1.4 WP1 Release of MERLIN with hollow electron lens  
D1.5 WP1

Release of MERLIN with speed optimised on different architectures


D1.6 WP1

Release of MERLIN containing composite materials


D1.7 WP1

Impact of chromaticity and off-momentum particles on the collimation system


D1.8 WP1

Determination of the usefulness of novel material layers for collimator impedance reduction and dynamics through simulation


D1.9 WP1

Report on bench test of collimator impedance with novel material layers


D1.10 WP1

Functional specification of detection and actuation for adaptive control based on collimator FE simulations


D1.11 WP1

Design of sensors and actuators with bench test and radiation tolerance results. Design of associated collimator components.


D1.12 WP1

Manufacture prototype and validate jaw straightness for nominal and localised heating to represent beam impacts


D2.1 WP2

Report on HOM coupler testing including low power tests, and dresssed cavity tests


D2.2 WP2

Final report on SPS test results, as the ultimate project output of the task. Describing the SPS test results, beam dynamics with and without CC, the RF issues and conclusions for HL-LHC. 


D2.3 WP2

Manufacturing readiness review to approve drawings. Completion of final cryomodule drawings. Including all shields, OVC, tooling etc. Some tooling drawings will be completed ad hoc later on.


D2.4 WP2

Completion pre-series cryomodule for HL-LHC crab cavity, containing two RFD cavities suitable for either SPS or HL-LHC installation. Thermal and vacuum performance will be tested with LN2 at Daresbury. Doesn’t include transport to CERN.


D2.5 WP2

Documented and benchmarked module for modelling of RF multipole components of the crabbing fields for SIXTRACK created. 


D2.6 WP2

Specification for the maximum RF multipolar components, and amplitude and phase jitter during the quench, for the crab cavities from SIXTRACK simulations. These simulations can be subsequently bench-marked against the SPS measurements.


D2.7 WP2

Estimation and measurement of the effect of the crab cavities will have on the beam in the SPS. A set of crab cavity parameters/effects, how to measure them and their actual measurement. 


D2.8 WP2

Estimation of the stability limits, detuning with intensity, heat loads for HL-LHC with crab cavities. Identification of mitigation measures (if needed).
Note : this work is ongoing now outside HL-LHC-UK and will not form a direct part of the task work plan, but members will contribute as needed.

D2.9 WP2

Estimation of the observables in the SPS relevant for the SPS crab-cavity experiment, and sources of beam-blowup in the machine without crab cavities through simulation and experiment. Description of settings and tests that would allow benchmark the simulations in the SPS. 


D2.10 WP2

Summary of the beam dynamics observations in the test of the crab cavities on the SPS and the associated simulations.


D2.11 WP2

Use RF system model to identify control algorithms, filters or hardware modifications for the crab cavity that mitigate undesirable RF characteristics during normal operation or during cavity quench and prepare for test in SPS.


D3.1 WP3

Design report for a prototype EO-BPM for the SPS. Includes electromagnetic simulation for the SPS bunch parameters and and opto-mechanical design of the EO-BPM prototype pick-up.


D3.2 WP3

Full prototype adapted for testing in SPS. Improved EO-BPM prototype with longer, thinner LiNbO3 crystals and electrodes, adapted to enhance the signal at the SPS.


D3.3 WP3

Report on the test of the EO-monitor on the SPS machine. Optical response results of  bench tests and beam measurements using the prototype pick-up installed in the SPS. 


D3.4 WP3

Design report for a prototype EO-BPM in the LHC. Results of electromagnetic simulations for LHC bunch parameters, using an opto-mechanical design of the pick-up for the LHC.


D3.5 WP3

Full EO-BPM prototype adapted for testing in the LHC.  Dependent on SPS test results, delivery of a prototype EO-BPM with opposing electro-optic pick-ups suited to measurements of bunches in the LHC.


D3.6 WP3

Availability of a gas-jet monitor. First prototype gas jet monitor established at Cockcroft Institute for intital studies into IPM and BIF mode, resolution, gas dynamics and general system optimisation.


D3.7 WP3

Design report for a final gas-jet for HL-LHC. Based on results from prototype test platform at Cockcroft Institute.


D3.8 WP3

Full prototype adapted for testing in the LHC. Third prototype, specification for HL-LHC, based on first two setups at CI.


D4.1 WP4

Splice Tooling Manufactured: Reliable tooling for splice is an crucial elements for preparing reprodicible high quality splices in DFX in-situ. Theu are manufactured for splice tests to verify suitability.


D4.2 WP4

Report on splice tests: results of splice tests reported with recommendations for the final splice design and manufacture.


D4.3 WP4

Consolidated definitions of DFX interfaces: detailed specifications of cryogenic, electrical, cooling control and quench detection/protection for the DFX to ensure compatibility with the conceptual design and HL-LHC magnet circuit layout.


D4.4 WP4

Full mechanical drawing for FDR


D4.5 WP4

Report on SC-Link Transients: Thermal/electromagnetic transients as the result of a faster quench protection by CLIQ are analysed with experimental studied. Recommendations made to the HL-LHC magnet circuit review.


D4.6 WP4

Preseries FDX ready: fully assembled with initial cryogenic tests. Ready for delivery to CERN.


D4.7 WP4

Evaluation of distributed quench detection using optical fibres and recommendations with respect to HL-LHC adoption


D4.8 WP4 Specifications for DFMJ/DFXJ series