Search

Operation of the LHC during 2010 and 2011 with 3.5 TeV beam energy and luminosity up to 3.65x1033 cm-2 s-1, led to radiation-induced failures of micro-electronic devices used in the cryogenic control system. Mitigating actions addressed equipment relocation and corrective patches on electronics and software. Driven by the technical requirements and by feedback from the cryogenic operation team, numerous consolidations and improvements were implemented on-the-fly, enhancing availability and operability of the LHC cryogenics. Furthermore, additional diagnostic tools, test benches, technical procedures and trainings have been provided to strengthen first line support services.

The cernox™ sensor is delivered with a 3-point resistance versus temperature cal-ibration that permits the construction of an individual interpolation table by using the data in the CERN thermometer database. For instance at the 4.2 K point, the individual calibration and the manufacturer data are within +/-0.1 K for 99.39% of a sample population of about 5700 sensors. Preliminary results also indicate that accuracies of 0.1 K and 1 K can be obtained below respectively 5 K and 77 K.

Within the ITER-CERN collaboration agreement, task “PROCUREMENT OF CRYOGENIC THERMOMETERS TO MONITOR ITER MAGNETS AND FEEDER TEMPERATURES”, CERN is investigating what would be the expected accuracy when using non-calibrated Cernox™ temperature sensors at 4.2 K. The cernox™ is a resistive type temperature sensor that is capable of measuring the full temperature range of interest for ITER, it is 4.2 K to 300 K. Non-calibrated cernox™ sensors are delivered with a table listing the resistance at the following temperatures: 4.2 K, 77 K and 300 K. CERN has deployed several thousands of individually calibrated cernox™ sensors and they are used to compare the manufacturer data at 4.2 K with their individual calibration performed by CERN. Within a sample size of 5’941 sensors, 99.39% of the population is able to provide a measurement within +/-0.1 K at 4.2 well within the requirements at low temperature specified by ITER.

The operation and monitoring of the LHC requires a cryogenic instrumentation system of an unprecedented size (800 instrumentation crates, holding 15000 sensors and actuators), with strict constraints on temperature measurement uncertainty and radiation hardness for all sensors and actuators. This paper presents the applied procedures of quality assurance and the specific hard- & software tools used to meet and track the mentioned requirements during its lifetime (fabrication, installation, commissioning, operation and maintenance); within the given constraints of time schedule, accessibility and coordination with other teams.

The Large Hadron Collider makes extensive use of superconductors, in magnets for bending and focusing the particles, and in RF cavities for accelerating them, which are operated at 1.9 K and 4.5 K. The process automation for the cryogenic distribution around the accelerator circumference is based on 16 Programmable Logic Controllers, each running 250 control loops, 500 alarms and interlocks, and a phase sequencer. Spread along 27 km and under ionizing radiation, 15 000 cryogenic sensors and actuators are accessed through industrial field networks. We describe the main hardware and software components of the control system, their deployment and commissioning, together with the project organization, challenges faced, and solutions found.

The Large Hadron Collider (LHC) at CERN is a superconducting accelerator and proton-proton collider of circumference of 27 km, lying about 100 m underground. Its operation relies on 1232 superconducting dipoles with a field of 8.3 T and 392 superconducting quadrupoles with a field gradient of 223 T/m powered at 11.8 kA and operating in superfluid helium at 1.9 K. This paper describes the cryogenic instrumentation commissioning, the challenges and the project organization based on our 2.5 years experience.

CERN is now setting up String 2, a full-size prototype of a regular cell of the LHC arc. It is composed of two quadrupole, six dipole magnets, and a separate cryogenic distribution line (QRL) for the supply and recovery of the cryogen. An electrical feed box (DFB), with up to 38 High Temperature Superconducting (HTS) leads, powers the magnets. About 700 sensors and actuators are distributed along four Profibus DP and two Profibus PA field buses. The process automation is handled by two controllers, running 126 Closed Control Loops (CCL). This paper describes the cryogenic control system, associated instrumentation, and their commissioning., Poster paper (TUAP065) presented at ICALEPCS 2001 conference, San Jose, USA, 3 pages in PDF format, comprising 2 figures and 2 tables