WP3: IR Magnets

Objectives

Task 3.1. Coordination and Communication

  • To coordinate and schedule work package tasks 

  • To monitor work progress and inform the project management and work package participants 

  • To follow up the WP budget and use of resources 

  • To prepare internal and deliverable reports

Task 3.2. Nb3Sn quadrupoles for the inner triplet

  • Analyze the performance of existing Nb3Sn models, in particular LARP HQ quadrupoles 

  • Conceptual design studies of a very large aperture option (150 mm) 

  • Finalize the requirements for the HL-LHC inner triplet Nb3Sn quadrupole

Task 3.3: Separation dipoles

  • Conceptual design of separation dipoles according to the specifications given by WP2 using either Nb3Al or Nb-Ti. If a model is built, specify and follow-up the tests needed for assessing the design.

  • Explore the possibility of using separation dipoles to create doglegs to increase the beam separation, thus allowing the installation of non-compact crab cavities.

Task 3.4: Cooling

  • Choose the operational temperature of the inner triplet quadrupoles and of the separation dipoles. Consider and compare both the superfuid and supercritical He options.

Task 3.5: Special Magnet Studies

  • Design a two-in-one quadrupole for the outer triplet (Q4-Q6) with nominal beam separation (192 mm) and aperture as large as possible (80-100 mm), satisfying the electromagnetic and mechanical requirements. Design of a two-in-one quadrupole for the inner triplet in the case of a dipole first option. 

  • Review the Nb-Ti option for the inner triplet considering the new targets in luminosity, and follow-up the tests of the short model built within the SLHC-PP project. 

  • Analysis of the expected lifetime of resistive quadrupoles in IR3 and IR7. Study of possible solutions, both resistive and superconductive, for the time scale of 2030 with a total integrated luminosity of 3000 fb-1.

Description of work

Task 3.1. Coordination and Communication

The activities of this task are for the work package coordinators [CERN and LBNL] to oversee and co-ordinate the work of all other work package tasks, to ensure the consistency of the work according to the project plan and to coordinate the WP technical and scientific tasks with tasks carried out by the other work packages when relevant. The coordination duties also include the organization of WP internal steering meetings, the setting up of proper reviewing, the reporting to the project management and the distribution of the information within the WP as well as to the other work packages running in parallel.

The task also covers the organization of and support to the annual meetings dedicated to the WP activity review and possible activity workshops or specialized working sessions, implying the attendance of invited participants from inside and outside the consortium.

Task 3.2. Nb3Sn quadrupoles for the inner triplet

This task is intended to give a final assessment of the possibility of using Nb3Sn quadrupoles for the LHC inner triplet and the performance parameters that can be achieved. A tentative layout with a 120 mm aperture quadrupole is given from WP2, and the necessary full list of requirements (field quality, radiation resistance, integration in the machine) should be worked out. A comparison with the present performance of the 120 mm aperture short model (HQ) magnets of LARP should be done, and iterations on the design if needed should be carried out. In particular we plan to analyze the following issues: (i) radiation resistance of all components (ii) magnet field quality and the possibility to apply corrections using magnetic shims (iii) option of splitting the magnet into two coils, with a related estimate of the loss in performance, possibly complemented by a hardware test, (iv) design of a helium containment vessel compatible with a magnet structure based on aluminum shrinking cylinder (v) magnet protection).

This task will be mainly driven by LARP collaboration (BNL, FNAL and LBNL). INFN will lead the quench protection study. CERN will participate in the studies and coordinate the efforts.

Task 3.3: Separation dipoles

The input necessary from WP2 is the needed integrated strength, a tentative lay-out, and an aperture requirement for the separation dipoles D1 and D2 used in the ATLAS and CMS interaction regions. Then, the first step is the conceptual designs of a separation dipole considering Nb3Al or Nb-Ti conductor. Main issues as (i) field quality, (ii) peak stresses at operational field, (iii) integration in the machine, (iv) radiation resistance (v) magnet protection will be analysed. If both options are viable, the second step would be the proposal of a short model to assess the Nb3Al technology. The third step would then be the follow-up the construction of the model, contributing to the test definition and to the analysis of the test results.

A similar type of technology would allow to further separate the LHC beams from the nominal distance of 194 mm to a wider one (400 to 500 mm). This “dogleg” is the plan B if the option of compact crab cavities is not viable. The inputs from the WP4 (crab cavities) and WP2 (beam dynamics) are the integrated field and the aperture. The task outcome is the conceptual design of a dogleg, and should strongly rely on the results of the D1-D2 programme.

This task is lead by KEK for the Nb3Al part and by BNL for the Nb-Ti option. INFN will steer the studies on protection. CERN will participate in the studies and coordinate the efforts.

Task 3.4: Cooling

The cooling system of the Nb3Sn inner triplet can operate either in superfluid (i.e., below 2.17 K) or in supercritical helium (i.e., above 2.17 K). Contrary to Nb-Ti magnets, Nb3Sn can operate in supercritical helium at around 4.5 K with a limited loss in field gradient w.r.t. the superfluid option (about 10%). This would also solve the Nb3Sn conductor instability issues that have been found by the US colleagues during the last decade.

As the heat loads envisaged today are more than one and a half order of magnitude above what is prevalent in the previous accelerators magnets designed for operation at supercritical helium (RHIC, HERA, Tevatron), it is mandatory to address the problem of cooling from the very beginning of the design of future quadrupoles.

Both the supercritical and the superfluid options should be analysed and compared. The programme can be divided into different phases: (i) analysis of heat loads and status of the different cooling scenarios (ii) principle of heat removal system, thermohydraulic simulations and first experiments (iii) validation of the system. A similar study should be carried out for the separation dipoles.

This task is steered by CERN for the superfluid part and by CEA-Grenoble for the supercritical part.

Task 3.5: Special Magnet Studies

This task includes three different studies: 
• The conceptual design of a large aperture two-in-one quadrupole for the outer triplet. The present baseline of the LHC involves 70 mm aperture magnets (MQY) whose aperture could be a bottleneck. One should explore the possibility of having two-in-one quadrupoles with apertures in the range 80-100 mm, with the same constraint of the 194 mm beam separation. Electromagnetic and mechanical aspects should be analysed. This design also applies to the option of a two-in-one inner triplet in the option of a dipole first option. This subtask is steered by CEA-Saclay. 
• The analysis of the expected lifetime of the resistive quadrupoles used in the cleaning insertion (MQWA and MQWB). The first step is to have an estimate of the radiation load, together with the lifetime of the present hardware. Then solutions to extend the lifetime of present hardware up to 2030 or options to replace them will be analysed. This subtask is steered by CERN. 
• The Nb-Ti option for the inner triplet is the plan B in case that experience shows that the Nb3Sn technology is not suitable. A considerable work has been done in the SLHC-PP framework, i.e. the so-called phase I, which aimed at a peak luminosity of 2.3×1034 cm-2 s-1. A short model is being built. One has to check that the Phase I scenario and lay-out is compatible with the new targets of the HL-LHC. This subtask is steered by CERN.

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