11T: Decision to install the collimator package in MB9 and update on the latest prototype test results and test plans

Since Issue 2 of the Newsletter, it was decided to change the installation position of the dispersion suppressor collimators (TCLD) of IR7 from cell 8 to cell 9 in order to provide a much better cleaning in cell 11 for both protons and ions operation. Although this implies a higher power density deposited in the superconducting coils of the 11T dipole magnet, it remains below their quench limit. Significant progress was made on the side of the magnet development and production, as follows. The full-length prototype was tested at cold in July 2018, unfortunately with unsatisfactory results. One of the four coils was limiting the performance of the magnet slightly above 8 kA, well below the nominal current, 11.85 kA. Thereafter, two first coils of the series production were put together in a hybrid assembly made with the structure of the prototype in order to be tested at cold quickly. The performance of these coils was outstanding during the first run, as they surpassed the nominal current after only one quench, and reached ultimate after only five quenches, without detraining. Unexpectedly, degradation of the performance was observed after a thermal cycle with indications of local damage of the conductor in the lead-end head of one of the two coils. Further investigations indicate that a too fast warm-up / cool-down (WUCD) process is likely the cause of the loss of performance, as it may generate excessive thermal stresses leading to conductor degradations. A slower WUCD process will be applied for the series magnets. The first one is being installed on the test bench, and the tests at cold will start by middle of July. The construction of the second magnet is well advanced, and the coil production is close to mid-way. In parallel with the production, the two models MBHSP107, and SP109, were tested at cold with very good results, even if SP109 has shown marginal degradation after high MIITs tests, and successive thermal cycles. The training of all the 11T dipole models, and of the hybrid assembly, in their first run, is shown in Figure 1.

fig1
Fig. 1: Training behaviour of the 11T dipole models and of the full-length hybrid assembly at their first run at cold