Beam extraction - 50th anniversary of the CERN Proton Synchrotron

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shortening of the usable flat top in the septum currents. Therefore half the choke inductance was sometimes used. Fig. 5: Left: the extraction area. Right: beam and septum magnet positions. The efficiency of extraction during the first tests was of the order of 50%, limited by the thickness of the septum of the extractor magnet. However, the resonant extraction was shown to be possible and it was decided to implement it towards the East Hall. The time structure of the burst was still poor owing to the imperfect regulation of power supplies at that time. The oscillogram of the spill and other relevant parameters is shown on Fig. 6. Fig. 6: Oscillogram of beam burst for SS01 integer extraction In 1965 an integer resonance extraction was installed with an extraction septum in SS58, shared with the fast extraction. One year after, the system was overhauled and the extraction septum was installed in SS62. The efficiency had improved but was still lower than 80%, causing heavy losses on the septum. The external target 64 soon disappeared and physicists received their particles from external targets. In 1967, the efficiency was further improved by means of the installation of a thin septum magnetic lens, 0.2 mm thick, in SS79. 6
A last improvement came in 1971 with the use of a first-stage separation of the extracted beam through an electrostatic septum. Efficiency could now reach values exceeding 90%. 3.2 Third-integer resonance ‘Square’ extraction 3.2.1 Choice of the resonance In the late 1960s it was decided to build the West Hall. A new extraction scheme had to be developed to provide for East or West area extractions whilst sharing with internal targets. The choice of the thirdorder resonance was made for several reasons. Three separatrices allow the possibility for three times more extraction straight sections [12]. Moreover, efficiency when sharing with an internal target is better than with integer resonance extraction. The final proposal was made in 1971. 3.2.2 Implementation Commissioning of the Square, Semi QUAdrupole Resonant Extraction, from SS16 or SS62 took place in 1972 (see the layout in Fig. 7) [13, 14]. Sharing was possible with internal targets 1 or 8, and later on with 1 alone. Three septa were used for each extraction: an electrostatic in SS83 for the first step (0.1 mm width), a thin magnetic septum in SS85 for the second stage (1.5 mm width), and thick magnetic septum (6 mm width) for the final extractions in SS16 or SS62 (in this last case there were even two extraction magnets in SS61 and SS62). Fig. 7: Layout of the equipments for the Square extraction in the late 1980s The resonance was driven by a standard quadrupole in SS23 and a non-linear magnet called semiquadrupole, located in SS53. A cross-section of this magnet, which is essentially one half of a Panofsky quadrupole, is shown in Fig. 8. The main coils create the non-uniform field and dipole coils compensate the dipole component of the field at the centre. 7
Page 1 and 2: Beam extraction 1 Introduction In t
Page 3 and 4: high-quality cable used for the PFN
Page 5: 3.1 Integer resonance extraction 3.
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 and 28: Fast pulsed magnets (kickers), to b
Page 29 and 30: Fig. 34: Upper: Cross-section of th
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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