© 1969 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. ROUNDTAEZEONBOOsTER II\wEcTT)Rs REICH:

THE CERN SYNCHROTRONBOOSTER presented by K.H. Reich Cern, Geneva, Switzerland

quarter-wavelength push-pull coaxial resona- tors per ring. Tuning is accomplished by The main features of this 800 MeV injector means of two biasing loops around the ferrite are described. The design philosophy is rings. The four metal-seal vacuum systems are discussed. interconnected via 32 manifolds each fitted with a 500 l/s sputter pumpll. A control Introduction computer will be used for data acauisition and controls. The equipment rooms and the auxi- The CERN Proton Booster (PSB), liary circular tunnel have been designed for under construction since January 1968, is to permanent accessd. provide 10'3 per pulse for transfer into the CERN Proton Synchrotron (CPS). The For the standard twenty-bunch single-turn transferred intensity should not exceed the CPS filling of the CPS the five bunches of each of space charge limit, and beam emittance and the four rings are ejected sequentially by energy spread must be suitable for high energy means of kicker magnets with 50 ns rise timeI*, physics experiments with both external targets and brought to the CPS beam level by the and the CERN Intersecting Storage Rings (ISR). magnet system13,14 shown in Fig. 3. At a later stage bunches from two rings may be After studying a number of possible solu- ejected simultaneously, combined vertically in tiona' a four-ring slow-cycling 800 MeV syn- the transfer line and injected into the CPS as as finally chosen for the following shown in Fig. 4. Two-turn injection of these bunches into the ISR is expected to lead to higher interaction rates and to reduce the un- Four rings (i) fit the numerology re- certainty of the collision energyb. sulting from the CPS RF harmonic number (20) and the ISR beam stacking requirements4, (ii) Design philosophy should ensure a sufficiently high phase space density*, (iii) lead to a design intensity per The emphasis has been on reasonable risk ring only moderately higher than current and high reliability bearing in mind cost values, and (iv) make for an acceptable hard- efficiency and available resources. ware filling factor. With the sixteen focusing periods chosen Slow-cycling, besides saving CPS cycle there is no systematic resonance in the range time, permits one to stack conveniently the Q = 4 to 5. The auxiliary quadrupole supplies PSB beam in CPS phase space in various ways, provide a corresponding tuning range at in- as illustrated below. jection and less at 800 MeV. 800 MeV final energy puts one spfficien- tly above the CPS space charge limit for most The PSB design beam emittances have b#een stacking cases studied4. scaled from the CPS values for a tenfold in- crease of the 50 MeV space charge limit*. Main features ,293 Some extra aperture has been added, to allow for possible transverse beam blow-up due to The four rings of 25 m radius are super- various space charge effects15. Multipole posed vertically (Fig. 1). The beam from the lenses are planned for Landau danping and existing 50 MeV linac is distributed by an straight section space is reserved for other electrostatic deflector5 to the three addi- damping devices. tional levels6 and injected into the PSB in About 20 O/o of the design RF voltage either single-turn or multi-turn mode. The serve to offset the RF bucket reduction due to four beams are then accelerated simultaneously longitudinal space charge forces16. to 800 MeV, ejected, recombined, and trans- ferred to the CPS. High voltages, current densities, as sell as fabrication, stability and alignment tole- The separate function magnet system7 rances, though occasionally demanding, have consists of 32 four-gap C-type window-frame generally been kept at conservative values. bending magnet units-(Fig. 2) and 48 quadru- poles lens units arranged in triplets. In particular, the magnet lattice chosen Bending magnets and lenses will be powered in leads to ejection kicker voltages of 30 kV and series from a rectifier set8 connected direc- ejection magnet deflection angles of about tly to the alternating current power line9. 50 mrad (0.25 Tm at 800 MeV), which is only The single fourfold RF accelerating unitlo 25 times the maximum beam divergence angle. consists of two ferrite-loaded air-cooled

959 The resulting parameters are listed in the following Table.

LIST OF PSB PARAMETERS2"

Lain parameters Momentum compaction functionRap 1.06, 1.46 m Transition energy/rest energy ytr 4*4 injection 50 MeV Design kinetic energy Beam emittance at injection EH 13011 low6 radm transfer 800 MeV EV 4On 10s6 radm Total design intensity 10'3 p.p.p. Number of superposed rings 4 Magnet system Average radius R 25 m 8.3 m 3'2 bending magnets of Magnetic bending radius P 1.62 m Average energy gain per turn 1 keV magnetic length Design vacuum pressure 6 10-8 Torr "Gap" dimensions 70 high x lG?mm wide Minimum repetition time 1.2 e Magnetic field 0.13 to 0.6 T Rise time 0.6 s 32 lenses of magnetic length 0.52 m 16 lenses of magnetic length 0.92 m Orbit parameters Bore radius 60 mm Focal constant K 0.7 to 0.8 rnv2 Lattice: separate function, FOFDD Maximum gradient 4 Tin-2 triplet focusing Number of lattice cells 16 Raaio frequency accelerating system Tuning range of betatron wave 4 to 5 numbers Harmonic number 5 Phase advance (QH= 4.55,4~=4.7) -1040 Number of cavities per ring 1 Amplitude function $Hmin,max 3.6, 7.3 m Frequency 3 to 8 MHz Peak voltage per turn 12 kV 3.4,17.8 m Bvmin,max Synchronous phase angle 4.80

Status and conclusions 3. Study Group for CPS Improvements, CERN Int. Report, MPS/DL-B/67-19. Most of the PSB design is frozen. A proto- 4. E.D. Courant, E. Keil, A.M. Sessler, Proc. type bending magnet unit and a quadrupole unit 1967 Cambridge International Accele- are on order, a RF cavity prototype and a power rator Conference, p. A16j-167. amplifier are being developed, the connecting tunnels with the CPS have been constructed and 5. R.P. Featherstone, The Injection Electro- the ring tunnel is being built. Commissioning static Deflector (Vertical) for the CERN is soheduled for 1972. PS Booster, CERN Int. Report, MPS/SI-Lin/68-1. Besides its direct value for the CPS users 6. T.R. Sherwood, M. Weiss, private communi- as a high-intensity high-quality proton source, cation. the PSB shows some generally interesting fea- tures, in particular vertical stacking of rings, 7. A. Asner, M. Giesch, private communication. beam splitting and recombination, and pulsing 8. B. Godenzi, R. Mosig, J. Pahud, private from the electric power grid. communication. Acknowledgements 9. B. Godenzi, Essais de pulsation directe de l'aimant du PS, CERN Int. Report, Initiated by P. Germain, the design study MPS/SI-ED/68-2. for the PSB was under the direct responsability 10. G. Nassibian, D. Zanaschi, private commu- of the MPS Division, headed by P.H. Stsndley. nication. The newly created SI Division under G. Brianti is responsible for its construction. MAY 11. C. Gould, C. Rufer, F. Schittko, people in ISR, MPS and SB Divisions and in HP W. Unterlerchner, private communication. contributed to the design, in particular 12. A. BrUckner, CERN 68-25. W. Hardt and H.G. Hereward. 13. C. Bovet, Further Thoughts on the Transfer References from Booster to CPS, CERN Int. Note, SI/DL 68-6. 0. Bayard, R.H. Reich, Le Synchrotron du 1 . 14. E. Weisse, CERN Int.Report, to be published. CERN: Vers 10'3 protons par impulsion, Industries Atomiques (Geneva),No. 11-12, 15. P.L. Morton, Space Charge Effects for the 1968 et 1-2, 1969. PSB, CERN Int. Report, SI/DL 68-3. 2. C. Bovet, K.H. Reich, Proc. 1967 Cambridge 16. U. Bigliani, Systbme HF du Booster, capture International Accelerator Conference, dans l'espace de phase longitudinal, p. 315-319. CERN Int. Report, SI/EL 68-2.

960 ‘~ \ ’ I r _I I’ i i i !’ I’ --- ,I ,’ i

Fig. 1 : Artist's impression of the CERN Booster Synchrotron (PSB)

Fig. 2 : Bending magnet (all dimensions are in mm )

cw yB* mcm4p Q LIW wo I(

m w a

-,o9--P- q &-+JL- ...7’ AP - Q, z. n ~!+--;.I a $ dJ , g?m.a// ~-=wao-e9~ KmslER CPS

Pig. 7 : Fig. 4 : Optics of the recombination part of the A schematic representation of how the five transfer line between PSB and CPS, ope- bunches of protons circulating in each of rating in the "20 bunch" mode. 'the four rings (I to IV) in the Booster can ESM : ejection septum magnets (- 46 mrad) be transferred to the CPS. In the 20 bunch mode (a), they are put one Km : vertical bending mngnets(- Eo mad) after another to give the usual twenty VSM : vertical septum magnets (- 00 mrad) bunches orbiting the CPS. In (b), which is a possible future develop- DSM : $uble septum magnet (- 5 mrad) ment, 2 L 5 bunches are put in opposite or vertical bunch combination) positions in the CPS which has particular K : kicker magnets (- 7 mad) advantages to achieve higher interaction rates when the protons are later fed into 9 : qU&3dP.lFOk?S the intersecting storage rings (1%). D : vertical dipoles (UP to 6 mad)

961