Update 22 July 2016
Over the past week a number of milestones were passed in the commissioning of the superconducting magnets.
The focus coil has been in routine operation in solenoid mode for data-taking. Data has been taken to validate the magnetic alignment of the module. Analysis is underway.
The end and centre coils of both solenoids have been operated at a current of 140A. Transients were observed on the quench-detection signals of both the upstream and the downstream solenoids. The upstream solenoid (SSU) exhibits a higher rate of such transients than the downstream solenoid (SSD), the absolute size of the excursions is small. After a number of investigations were carried out, including the study of the movement of the partial return yoke, the relative movement of the yoke and the solenoids and the movement of the solenoids themselves. When all of these investigations failed to identify clearly the source of the transients, it was decided to increase the trip threshold to 200mV and run the magnets individually for a period to observe the rate of transients and whether there was any trend for the transients to grow. These tests were successful in that the transients never exceeded the 200mV threshold and were observed to be of relatively constant amplitude.
Having run both magnets individually to allow data taking for magnetic alignment, on Wednesday 20Jul16, both SSU and SSD were brought to 140A. In the combined combination SSU + SSD, the solenoids were observed to behave just as they did in stand-alone running. Stable operation was established and data was taken with more than one superconducting solenoid in operation for the first time.
The attached slides show a selection of plots from the data taking on Wednesday 20Jul16; I hope the slides are self explanatory. The distribution of space points in the upstream and downstream trackers appears to follow the beam envelope predicted by Chris Roger’s linear-optics calculation. The phase-space distributions obtained using the reconstructed tracks are also shown. The result of a MAUS simulation of the conditions under which data was taken on the 20Jun16 is shown in the slides for comparison. The simulation gives a fair, qualitative, description of the data. There is, of course, more work to do to understand the differences in detail.
The results presented in the slides are the result of the hard work of all; a really important step has been made!
Moving forward, the magnet and operations teams are discussing how best to approach the goal of taking data with all superconducting magnets—in the configuration SSU+FC+SSD before the end of the present User Cycle.
Looking forward to discussing the progress and results at CM45!