Commissioning and First Operation of the Low-Beta Triplets and Their Electrical Feed Boxes at the Large Hadron Collider

Abstract

The insertion regions located around the four interaction points of the Large Hadron Collider (LHC) are mainly composed of the low-triplets, the separation dipoles and their respective electrical feed-boxes (DFBX). The low-triplets are Nb-Ti superconductor quadrupole magnets, which operate at 215 T/m in superfluid helium at a temperature of 1.9 K. The commissioning and the first operation of these components have been performed. The thermo-mechanical behavior of the low-triplets and DFBX were studied. Cooling and control systems were tuned to optimize the cryogenic operation of the insertion regions. Hardware commissioning also permitted to test the system response. This paper summarizes the performance results and the lessons learned.

Commissioning of the Cryogenics of the LHC Long Straight Sections

“…From the cryogenic point of view, the specificity of these magnets is the very high beam induced heat load that can be seen at 1.9 K in the high luminosity IR1 and IR5: when the beam collide at nominal luminosity, the beam induced heat load, 200 W, on the three FFMs is expected to be nearly the same as in the 2.8 km of the arc section. As described in [8] it was possible to demonstrate during the commissioning that the cryogenic system could extract such power in a reliable and stable way.…”

“…The superconducting magnets operate at 1.9 K in pressurized superfluid helium. After having solved several difficulties with the electrical feedboxes, in particular a redesign of the control system of the resistive gas cooled leads [8], most circuits of the FFMs could be powered to their nominal current values.…”

“…The commissioning phase was therefore the first time that the feedboxes were cooled. A more detailed description of their cryogenic commissioning is given in [4] for the CERN supplied ones and in [8] for the US supplied ones.…”

“…Two different approaches were applied to the CERN supplied DFBs and to the US supplied DFBs. For the US-supplied DFBs, a special coating was applied on the cold insulating parts to avoid the creation of a continuous path able to damage the insulation properties [8]. For the CERN-supplied DFBs, the problem was solved with two measures: the temperature of the top part of the current leads was increased to 30°C and copper bridges (in the form of multiple flexible sheets) were added to bring heat to the insulating flange (see FIGURE 3).…”

Upgrade of the gas flow control system of the resistive current leads of the LHC inner triplet magnets: Simulation and experimental validation

“…The 600 A and 120 A circuits of the inner triplet magnets of the Large Hadron Collider are powered by resistive gas cooled current leads [1,2].The gas flow through theses leads is controlled by an indirect temperature measurement which induce severe limitations in the operating parameters of these circuits, in particular during the current variation phases. In addition to these limitations, the temperature sensors used for the regulation are located in a difficult to access and irradiated area.…”