HESR bake-out test stand
To check whether the developed bake-out system reaches the required temperature of 180°C at every point and whether the maximum permissible temperature for the solenoid coils of approx. 80°C is not exceeded at the same time, a bake-out test stand with a special control system was to be developed and built.
Technical challenges
Simulations were made in advance to estimate the expected temperatures and possible critical points. The planned bake-out test stand had to replicate the subsequent operating conditions as accurately as possible and also enable as much relevant measurement data as possible to be recorded.
The realised bake-out test stand consists of a NEG-coated dipole chamber with original dimensions, an iron body to simulate the magnet iron, heating sleeves (22 pieces), vacuum pumps (Turbo, IZ, NEG), pressure sensors (7 pieces), UHV angle valve and temperature sensors (41 pieces) to control and precisely record the component temperatures.
A specific control system was developed and implemented to realise different temperature levels and monitor the temperature differences between the individual components as well as to store and visualise the measured values.
Detailed test programmes were carried out to measure the temperature distribution in the individual components for different bake-out temperatures (230°C-300°C) and different designs of heating jackets from different manufacturers.
The temperatures for the magnetic iron determined in advance by simulation calculations were confirmed and, at 52°C, are well below the maximum permissible temperature for the iron body scaled down in the test. Temperatures of only approx. 27°C are expected for the real dipole magnet due to the better heat conduction and the larger mass.
Based on the results, the shape and performance of the heating sleeves were optimized so that the temperatures for activating the NEG material could be achieved everywhere despite the difficult spatial conditions.