Lhc transfer lines and injection systems

The status and commissioning plans of the transfer line and injection hardware are presented with focus on the injection dump and kickers. Modifications of the beam loss monitoring in the injection region, its readiness for the startup and commissioning strategy are shown. A new interlock strategy for the injection protection elements and the injection septum is introduced. The expected transfer line stability and possibilities to improve the turnaround with optimized SPS supercycles for LHC injection are discussed. TRAJECTORY STABILITY The trajectory stability in the transfer lines TI 2 and TI 8 is dominated by the stability of the SPS extraction septum (MSE) power converters. The low MSE inductance of 80 μH is the cause of having almost no filtering effect from the load side on the current. Three main frequency ranges of voltage instabilities can be distinguished for the MSE: • Asymmetries in the power converter: 100 -200 Hz • Measurements, stray fields: 50 Hz • Regulation: few Hz For the MSE power converter in BA6 the filter was further improved in LS1 which allowed to reduce the voltage ripple for the higher frequency ranges mentioned above. A reduction of the peak-to-peak ripple from 9 to 3.5 A is expected which has to be compared to the overall aim of having a ripple below 4 A. The MSE power converter in BB4 has a better topology than the one in BA6 but an asymmetric 18 kV ac distribution network which is considered to partly cause the ripple. The other contribution came from a problem in the DC current transformer (DCCT) which showed a 5 A peak-to-peak oscillation when the power converter had been switched off, Fig 1. This caused the closed feedback loop to correct for this non-existing oscillation and therefore disturbing the power converter performance. The DCCTs in BB4 were repaired, Fig. 2, and the ones in BA6 tested without detecting this problem. The filters in BB4 were improved, too. A total of 200 capacitors will be exchanged during LS1. FINAL TDI HARDWARE The main upgrades of the TDI during LS1 concerned the beam screen. The old copper screen was replaced by a reinforced 6 mm stainless steel screen on a new supporting Figure 1: DCCT in BB4 before the repair. A 5 A peaktopeak current oscillation is visible (PC switched off). Figure 2: DCCT in BB4 after the repair. Note the scale. A ±0.75 A peak-to-peak current oscillation is visible which corresponds to the expected noise level. frame. The sliding system was upgraded, the central RF fingers were replaced by mechanical connections and the RF extremities bolted instead of electron beam welded. In total 8 temperature sensors were installed. The gearboxes were replaced by new greased ones. The cooling circuits were not in the initial TDI design but added later. Even though measurements of the cooling water temperature gradients had shown that the cooling circuits are not very efficient the same design will be kept for after LS1. The coating of the different TDI blocks was tested during bake-out. As a result NEG coating is not compatible with hexagonal boron nitrite (hBN) outgassing after baking at 300oC, Figs. 3 and 4. In Table 1 the original proposal of coatings is compared with the final solution. The adjacent chambers to the TDI will be NEG-coated and baked to improve the vacuum level and thus reduce the background for the experiments.