Upgrades for the CERN PSB-to-PS Transfer at 2 GeV

The CERN PS Booster extraction energy will be upgraded from 1.4 to 2.0 GeV to alleviate the direct space charge tune shift in the PS. The focussing structure of the transfer line will be modified in order to better match the optics between the PSB and the PS. The optics of the PS at injection and, with it, of the transfer line can be adapted to reduce the continuous losses from the already injected and circulating beam bumped towards the septum. Experimental results of the optics optimisation and probing the injection kicker flat top are shown. Modifications of the recombination septa and the main horizontal bending magnet in the measurement line are presented. INTRODUCTION Within the upgrade of the PSB extraction energy the transfer line quadrupoles in the PS access zone will be exchanged to allow for pulse-to-pulse modulated optics settings. The present mismatch at PS injection shall be overcome by a new design of the focussing structure. The following paragraphs present measurements of the injection kicker flat top ripple, injection losses for a dedicated PS injection optics and foreseen hardware changes of the recombination septa and the main horizontal bend in the measurement line (BTM.BHZ10). PS INJECTION KICKER RIPPLE Besides the classical LHC-beam production scheme based on injection on the 7 harmonic and triple splittings, an alternative one is based on batch compression and batch merging of 8 bunches injected on the 9 harmonic [1]. Figure 1: Horizontal emittance measurements for the injection kicker in terminated and short-circuit mode. Since the relative emittance increase for this small emittance beam due to the injection kicker ripple could be important, measurements of the emittance in the PS on the full kicker pulse length for short-circuit and terminated mode have been performed on June 28, 2012. Figure 1 shows the resulting emittance measured for the injected beam for different kicker timing delays. Taking into account the error bars, there is little difference in emittance for short-circuit and terminated mode. In general, the flat-top ripple is small, the bunch at t=0 is close to the edge of the kicker pulse and slight fluctuations in the kicker timing or bunch phase change the emittance significantly. This measurement point was repeated several times and observations of the direct analog signal of the kicker discharge with respect to the bunch show that different parts of the bunch were indeed kicked differently. Figure 2: For the kicker timing t=0 only part of the bunch (red curve) is kicked due to slight fluctuations of the kicker delay and bunch phase. PS INJECTION LOSS MEASUREMENTS The proton injection region in straight section 42 in the PS tunnel marks a critical position with respect to ambient dose rates on the road passing above outside the tunnel. Losses at injection appear due to single passage losses in the injection channel of septum SMH42 and due to continuous losses from the bumped circulating beam being scraped off by aperture bottlenecks in the injection region for about 500 turns [2]. In order to reduce these losses, a dedicated optics which optimises the beam sizes in the PS injection region was calculated deploying the special quadrupoles used to change the optics at extraction (QKE16). Using these quadrupoles, the optics of about the full PS ring is distorted. Depending on the results of these tests, new dedicated quadrupoles could be installed to allow for the optics changes to be only locally in the injection region. The optics in the PSB-to-PS transfer line was rematched using a quadrupole which is not used in normal operation due to its inaccessible and thus unmaintainable location in the separation wall between PSB and PS. 0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.85 0.9 0 50