Marco Pezzetti

First assessment of reliability data for the LHC accelerator and detector cryogenic system components

The Large Hadron Collider (LHC) cryogenic system comprises eight independent refrigeration and distribution systems that supply the eight 3.3 km long accelerator sectors with cryogenic refrigeration power as well as four refrigeration systems for the needs of the detectors ATLAS and CMS. In order to ensure the highest possible reliability of the installations, it is important to apply a reliability centred approach for the maintenance. Even though large scale cryogenic refrigeration exists since the mid 20th century, very little third party reliability data is available today. CERN has started to collect data with its computer aided maintenance management system (CAMMS) in 2009, when the accelerator has gone into normal operation. This paper presents the reliability observations from the operation and the maintenance side, as well as statistical data collected by the means of the CAMMS system.

The CERN revamping project of the obsolete cryogenic control systems: Strategy and results

The cryogenic infrastructure at CERN was originated in the 1960s with the era of bubble chambers and the associated superconducting solenoids. Since then and especially with the construction of the LHC accelerator and its detectors, large and complex cryogenics plants have been installed to provide cooling power from 800 W to 18 kW at different temperatures down to 1.9 K, demanding high and distributed technical capabilities from the control systems. The size and the complexity of the dedicated cryogenics has required the adoption of the CERN standard control framework UNICOS in order to enhance ease of operation and maintenance, and to provide long-term availability. After the completion of the LHC construction, exploiting the gained experience, CERN has started the upgrade of several obsolete cryogenic control systems. This paper describes (i) the overall project challenges, (ii) the technical procedure used in order to meet the technological operational requirements in terms of installation constraints...

Commissioning and First Operation of the Cryogenics for the CERN Axion Solar Telescope (CAST)

A new experiment, the CERN Axion Solar Telescope (CAST) was installed and commissioned in 2002. Its aim is to experimentally prove the existence of an as yet hypothetical particle predicted by theory as a solution of the strong CP problem and possible candidate for galactic dark matter. The heart of the detector consists of a decommissioned 10‐m long LHC superconducting dipole prototype magnet, providing a magnetic field of up to 9.5 T. The whole telescope assembly is aligned with high precision to the core of the sun. If they exist, axions could be copiously produced in the core of the sun and converted into photons within the transverse magnetic field of the telescope. The converted low‐energy solar axion spectrum, peaked around a mean energy of 4.4 keV, can then be focused by a special x‐ray mirror system and detected by low‐background photon detectors, installed on each end of the telescopes twin beam pipes. This paper describes the external and proximity cryogenic system and magnet commissioning as w...

JACoW : Automation of the software production process for multiple cryogenic control applications

The development of process control systems for the cryogenic infrastructure at CERN is based on an automatic software generation approach. The overall complexity of the systems, their frequent evolution as well as the extensive use of databases, repositories, commercial engineering software and CERN frameworks have led to further efforts towards improving the existing automation based software production methodology. A large number of process control system upgrades have been successfully performed for the Cryogenics in the LHC accelerator, applying the Continuous Integration practice integrating all software production tasks, tools and technologies. The production and maintenance of the control software for multiple cryogenic applications have become more reliable while significantly reducing the required time and effort. This concept has become a guideline for development of process control software for new cryogenic systems at CERN. This publication presents the software production methodology, as well as the summary of several years of experience with the enhanced automated control software production, already implemented for the Cryogenics of the LHC accelerator and the CERN cryogenic test facilities.

submitter : Commissioning results of CERN HIE-ISOLDE and INFN ALPI cryogenic control systems

The cryogenic systems of both accelerators, namely HIE ISOLDE (High Intensity and Energy Isotope Separator On Line DEvice) at CERN and ALPI (Acceleratore Lineare Per Ioni) at LNL, have been refurbished. HIE ISOLDE is a major upgrade of the existing ISOLDE facilities, which required the construction of a superconducting linear accelerator consisting of six cryomodules, each containing five superconductive RF cavities and superconducting solenoids. The ALPI linear accelerator, similar to HIE ISOLDE, is located at Legnaro National Laboratories (LNL) and became operational in the early 90s. It is composed of 74 superconducting RF cavities, assembled inside 22 cryostats. The new control systems are equipped with PLC, developed on the CERN UNICOS framework, which include Schneider and Siemens PLCs and various fieldbuses (Profibus DP and PA, WorldFIP). The control systems were developed in synergy between CERN and LNL in order to build, effectively and with an optimized use of resources, control systems allowing to enhance ease of operation, maintainability, and long-term availability. This paper describes (i) the cryogenic systems, with special focus on the design of the control systems hardware and software, (ii) the strategy adopted in order to achieve a synergic approach, and (iii) the commissioning results after the cool-down to 4.5 K of the cryomodules.

Overview of different control strategies for a typical cryogenic warm compressor station at CERN

Helium cryogenic systems are extensively used at CERN under several configurations for accelerators and detectors. The Warm Compressor Station (WCS) is the primary component of the helium cryogenic systems. The basic controls structure mainly depends on the bypass, charge and discharge valves configuration ensuring the nominal flow and compression ratio. This paper presents three studied methods for the WCS process control systems covering all transient and operational requirements: the proportional-integral-derivative (PID) control approach, the Fuzzy Logic Control approach (FLC) and the Internal Model Control approach (IMC). The paper emphasizes on simulation results of the different control strategies using Ecosimpro software associated to the CERN CryoLib library. Advantages and limitations of each method are presented.