Test of heat exchanger in line N

2007

The line N is a special superconducting line in the LHC, which is external to the

cold mass. The line is connected to the cold mass every half cell, and due to this

it will have the same operating pressure and temperature as the magnets. In the

dispersion suppressor zones the cool down of the line N is slightly delayed with

respect to the magnets, due to its geometrical design.

As this delay may affect the readiness of the accelerator for operating, it is

desired that it is reduced to less than two hours. In a test called String 2 a full

scale model of the LHC cell was built to validate the LHC systems in working

condition, and to investigate the collective behavior under various conditions.

During this test, there was installed a copper plug in line N. The result showed

that the cool down time of the line was delayed by more than two hours.

After this test there has been designed a new copper heat exchanger that is used

in the line N to make additional lambda fronts, and by this lower the cool down

time of the line. The design of this heat exchanger has been chosen by

mathematical models that were compared to the String 2. The finished heat

exchanger has never been tested, but it is presumably that it will reduce the cool

down time in line N to less than two hours.

The goal of this project is to follow up a test of the heat exchanger at the

cryogenic laboratory at CERN. I will also try to make a computer model of the

heat exchanger, which can be verified by the result of the test. The results from

this computer model can later be used to calculate the cool down time of line N,

and then see if the target for the cool down time is reached.