Beam extraction - 50th anniversary of the CERN Proton Synchrotron

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Fig. 32: Measured gradient of the three octupoles available for installation (left). Picture of the SS39 (right). The two yellow sextupoles are interleaved by the violet octupole. 7.2.4 Optimization of the aperture A crucial issue for the implementation of MTE is the available mechanical aperture. On account of the principle, once the beam is split, there will be five beamlets circulating in the ring with different closed orbits. This increases the required aperture, in particular in the extraction region. The changes implemented during the installation of MTE are concentrated in straight sections in the neighbourhood of SS16 and they are aimed at accommodating the five beamlets without any beam losses. As an example, the original and the new layout of the vacuum chamber installed in the magnet unit 16 are shown in Fig. 33. The main improvement refers to the increase of the cross-section for the part of the vacuum chamber dedicated to the circulating beam. Furthermore, the longitudinal extension of the region where circulating and extracted beams share the same aperture was increased. Fig. 33: Layout of the new vacuum chamber in magnet unit 16 (lower part). The chamber originally installed is also shown (upper part). The available aperture in the extraction region is shown in Fig. 34. In the upper part the cross section of the new vacuum chamber in magnet unit 15 is shown together with the beam envelope at 3 σ, represented by the rectangles, with the slow and fast bumps switched on. In the lower part the same situation is represented as a function of beam trajectory. 28
Fig. 34: Upper: Cross-section of the new vacuum chamber in magnet unit 15 together with the transverse sections of the beamlets at extraction. The units for both axes are millimetres. Lower: Superposition of the horizontal beam envelope for the five beamlets at extraction, i.e., when both the slow and fast bumps are switched on. Only a subset of the PS circumference in the neighbourhood of the extraction point is shown. The main magnet identification numbers are shown on the top. 8 MTE beam commissioning in 2008 and 2009 After the completion of the installation phase during the winter shutdown 2007/2008, the hardware and beam commissioning started in the 2008 PS run. Here, the milestones will be recorded, the details being available in Refs. [45–47]. The first half of 2008 was devoted to the hardware commissioning and the setting up of the beam splitting with the new hardware [45]. The first MTE extraction was performed on 1 August 2008, when a single-bunch beam of about 3×10 12 protons was sent to an external dump in the PS–SPS transfer line. Figure 35 (left) shows the measured horizontal beam profile of the beamlets in the PS at the end of the splitting process and prior to extraction. A fit of the five beamlets is also superimposed. Figure 35 (right) shows the intensity signal of a pick-up in the PS–SPS transfer line of the extracted beam. Each of the five peaks corresponds to a beamlet extracted over a single turn. The distance between them corresponds to the PS revolution time of 2.1 µs. As expected, the five peaks feature about the same intensity, a clear sign that the equally populated islands were correctly extracted. 29
Page 1 and 2: Beam extraction 1 Introduction In t
Page 3 and 4: high-quality cable used for the PFN
Page 5 and 6: 3.1 Integer resonance extraction 3.
Page 7 and 8: A last improvement came in 1971 wit
Page 9 and 10: the semi-quadrupole began to raise
Page 11 and 12: Fig. 11: Left: electrostatic septum
Page 13 and 14: 3.3.3 Performance of the SE61 extra
Page 15 and 16: After the proposal, an experimental
Page 17 and 18: 80 70 60 β x β y D x SS31 50 40 S
Page 19 and 20: 3.3×10 13 protons per PS batch. Am
Page 21 and 22: Fig. 25: 3D view of the beamlets al
Page 23 and 24: Fig. 27: Sequence of beam profile d
Page 25 and 26: they were done over two consecutive
Page 27: Fast pulsed magnets (kickers), to b
Page 31 and 32: Fig. 36: Intensity of a MTE de-bunc
Page 33 and 34: [16] F. Galluccio, T. Risselada, Ch

Beam extraction - 50th anniversary of the CERN Proton Synchrotron

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