Vittorio Parma

New vertical cryostat for the high field superconducting magnet test station at CERN

In the framework of the R&D program for new superconducting magnets for the Large Hadron Collider accelerator upgrades, CERN is building a new vertical test station to test high field superconducting magnets of unprecedented large size. This facility will allow testing of magnets by vertical insertion in a pressurized liquid helium bath, cooled to a controlled temperature between 4.2 K and 1.9 K. The dimensions of the cryostat will allow testing magnets of up to 2.5 m in length with a maximum diameter of 1.5 m and a mass of 15 tons. To allow for a faster insertion and removal of the magnets and reducing the risk of helium leaks, all cryogenics supply lines are foreseen to remain permanently connected to the cryostat. A specifically designed 100 W heat exchanger is integrated in the cryostat helium vessel for a controlled cooling of the magnet from 4.2 K down to 1.9 K in a 3 m3 helium bath. This paper describes the cryostat and its main functions, focusing on features specifically developed for this project. The status of the construction and the plans for assembly and installation at CERN are also presented.In the framework of the R&D program for new superconducting magnets for the Large Hadron Collider accelerator upgrades, CERN is building a new vertical test station to test high field superconducting magnets of unprecedented large size. This facility will allow testing of magnets by vertical insertion in a pressurized liquid helium bath, cooled to a controlled temperature between 4.2 K and 1.9 K. The dimensions of the cryostat will allow testing magnets of up to 2.5 m in length with a maximum diameter of 1.5 m and a mass of 15 tons. To allow for a faster insertion and removal of the magnets and reducing the risk of helium leaks, all cryogenics supply lines are foreseen to remain permanently connected to the cryostat. A specifically designed 100 W heat exchanger is integrated in the cryostat helium vessel for a controlled cooling of the magnet from 4.2 K down to 1.9 K in a 3 m3 helium bath. This paper describes the cryostat and its main functions, focusing on features specifically developed for this projec...

The design of the new LHC connection cryostats

In the frame of the High Luminosity upgrade of the LHC, improved collimation schemes are needed to cope with the superconducting magnet quench limitations due to the increasing beam intensities and particle debris produced in the collision points. Two new TCLD collimators have to be installed on either side of the ALICE experiment to intercept heavy-ion particle debris. Beam optics solutions were found to place these collimators in the continuous cryostat of the machine, in the locations where connection cryostats, bridging a gap of about 13 m between adjacent magnets, are already present. It is therefore planned to replace these connection cryostats with two new shorter ones separated by a bypass cryostat allowing the collimators to be placed close to the beam pipes. The connection cryostats, of a new design when compared to the existing ones, will still have to ensure the continuity of the technical systems of the machine cryostat (i.e. beam lines, cryogenic and electrical circuits, insulation vacuum). This paper describes the functionalities and the design solutions implemented, as well as the plans for their construction. Structural studies Thermal studies Case A : operational conditions Loading • Nominal pressure (1.3 bar) • Self weight Requirement • Maximum deformation ≤ 0.1 mm Result • 0.08 mm deformation at magnet end side Case B : quench conditions Loading • Design pressure (20 bar) • Self weight Requirement • Stress ≤ requirement of EN 13445-3 Annex C Result • Within requirement of standards 2.2 safety factor on membrane stress 4.6 safety factor on membrane + bending stress Case A : Maximum cooling Loading: • 50 K at end of copper braids Requirement : • No plastic deformation • No large deformation (< 1 mm) Results • Negligible deformation • Maximum stress = 100 MPa (240 MPa allowed) Case B : Real conditions Loading • Calculated heat transfer coefficient between helium gas and pipe wall • Linear temperature/time gradient Requirement • 24 h maximum delay between gas temperature and cold mass temperature Results • 24 h delay to reach uniform stable conditions • Install collimators in LHC IR2 (Alice experiment) left and right • Bypass cryostat to create room temperature space for installation of collimator • Replace one existing connection cryostat (12.7 m) with two shorter ones and a bypass cryostat • Ensure continuity of the cryogenic, vacuum and powering systems Supporting structure • Ease access during assembly • Machined stainless steel plates • Bolted, no welds to avoid stress/deformation • Stress relieved for geometrical stability V’ cooling tube Requirements • Beam line heat load = 0.65 W/m • Cold bore below 2.7 K Solution • Cold bore inside concentric tube • Interspace filled with superfluid helium • Helium cooled by shuffling module Beam line to V’ supporting Requirements • Vertical positioning : +/0.5 over full length • Horizontal positioning: +/0.8 mm over full length Solution • Guide cold bore to V’ cooling tube every 750 mm • Indenting V’ line in three positions spaced at 120 degrees • Radial gap < 0.1 mm Thermalisation Requirements • Homogeneous cool-down of the support structure • Cool-down to 80 K in one week Solution • 1200 mm2 copper braids between bus-bars line and support structure every 833 mm Shuffling module • Composed of two dished ends welded back to back • Create space for bus-bars flexible sections • Houses copper bayonet heat exchanger • Transition between standard LHC interconnect layout and bypass cryostat layout Flexible busbars lines Reduce interconnection transversal forces from 2920 N to 300 N Negligible deformation of cold mass (<< 0.1 mm deformation due to weight) > 90% due to M lines bellows C1PoM-03 Vertical deformation of cold mass under operational conditions Membrane stress in shuffling module in quench conditions Membrane + bending stress in shuffling module in quench conditions Maximum thermal stress in the support structure (after 4 hours of cooldown) Temperature in the cold mass after 4 days of cooldown 0 25 50 75 100 125 150 175 200 225 250 275 300 0 1 2 3 4 5 6 7 Te m pe ra tu re (K ) Time (days) He gas T

IOP : Cryogenic safety in helium cryostats at CERN

Cryostats contain large cold surfaces, cryogenic fluids, and sometimes large stored energy (e.g. energized magnets), with the potential risk of sudden liberation of energy through thermodynamic transformations of the fluids, which can be uncontrolled and lead to a dangerous increase of pressure inside the cryostat envelopes. The consequence, in the case of a rupture of the envelopes, may be serious for personnel (injuries from deflagration, burns, and oxygen deficiency hazard) as well as for the equipment. Performing a thorough risk analysis is an essential step to identify and understand risk hazards that may cause a pressure increase and in order to assess consequences, define mitigation actions, and design adequate safety relief devices to limit pressure accordingly. Lessons learnt from real cases are essential for improving safety awareness for future projects. We cover in this paper our experience on cryostats at CERN and the design-for-safety rules in place.

First HIE-ISOLDE cryo-module assembly at CERN

The first phase of the HIE-ISOLDE project aims to increase the energy of the existing REX ISOLDE facilities from 3 MeV/m to 5 MeV/m. It involves the assembly of two superconducting cryo-modules based on quarter wave resonators made by niobium sputtered on copper. The first cryo-module was installed in the linac in May 2015 followed by the commissioning. The first beam is expected for September 2015. In parallel the second cryo-module assembly started. In this paper, we present the different aspects of these two cryo-modules including the assembly facilities and procedures, the quality assurance and the RF parameters (cavity performances, cavity tuning and coupling).

Fast cycled superconducting magnets for the upgrade of the LHC injector complex

An upgrade of the LHC injection chain, and especially the sequence of PS and SPS, up to an extraction energy of 1 TeV, is one of the steps considered to improve the performance of the whole LHC accelerator complex. The magnets for this upgrade require central magnetic field from 2 T (for a PS upgrade) to 4.5 T (for an SPS upgrade), and field ramp rate ranging from 1.5 to 2.5 T/s. In this paper we discuss under which conditions superconducting magnets are attractive in this range of operating field and field ramp-rate, and we list the outstanding issues to be adddressed by a dedicated R&D. MAGNET NEEDS AND R&D TARGETS