HEP Accelerators II M. Cobal

1. HEP Accelerators II M. Cobal

3. Classical calculations cannot be used anymore for γ ≈ 1.04, relativistic mass increase of 4% about, that is` β≈ 0.27 ( v = 0.27 c ). Orbital stability equation M v ² ––– = q v B r Lorentz force Centripetal force The maximum kinetic energy reachable can be calculated in a classical way; Ecin = ½ mv² = q² B² r² / 2m The cyclotron frequency does not depend from r or from the Voltage difference between the Dees!

4. Betatron Variant to cyclotron, keep beam trajectory fixed, ramp magnetic fields instead. 25 MeV protons in 1940s. First fixed circular orbit device...

5. Main cyclotron problem: relativistic mass increase • Frequencyfcannotremainconstant: • f = q B / 2π mγ • Either: • B isincreased for biggerradius or • the frequencyisproperlymodulated to stay tuned with the particle’spassagewhentheyhave a higherenergy. Berkeley Sinchrociclotron

6. Synchrocyclotron • Fixed “classic” cyclotron problem by adjusting “Dee” frequency. • No longer constant beams, but rather injection+acceleration • Up to 700 MeV eventually achieved

7. SC at CERN 600 MeV Electromagnets became bigger and bigger, while energies were still too low..

8. At the heart of the CERN SC

9. Sincrotrone La soluzione per le alte energie Raggio dell’ orbita costante Con magneti dipolari disposti solo lungo l’orbita del fascio. Protoni o elettroni mantenuti all’interno di un tubo a vuoto. Accelerazione effettuata solo in alcuni punti dell’anello Valore di B all’i+1-esimo giro Bi+1 = √ (Ei + T)2 – mc2 c q r Intensità di B variabile nei magneti bipolari Frequenza variabile nelle cavità acceleratrici

11. Synchrotrons Use smaller magnets in a ring + accelerating station 3 GeV protons BNL 1950s Basis of all circular machines built since Fixed-target mode severely limiting energy reach

12. FERMILAB FNAL CERN LBL BROOKHAVEN

13. Synchrotrons: Magnets

14. Storage Rings One or two beams counter-circulating in same beam-pipe Collisions occur at specially designed Interaction Points RF station to replenish synchrotron losses

15. Beamline Elements Dipole (bend) magnets Quadrupole (focusing) magnets Also Sextupoles and beyond

16. In cyclic accelerators, protons make typically 105 revolutions, • receiving an RF kick of the order of a few Mev per turn • To provide focussing, two types of magnets • bending magnets: produce a uniform vertical dipole field over the width of the beam pipe and constrain protons in a circular path • focussing magnets: produce a quadrupole field. Used with alternatively reversed pole so that, both in vertical and horizontal directions one obtains alternate focussing and defocussing effects. • Like for a serie of diverging and converging lenses: • net effect is focussing in both planes

17. Cosmotron – BNL 1953 - 1968 Il primo acceleratore a superare la barriera del GeV e il primo ad avere una estrazione del fascio per esperimenti all’esterno.

18. Colliders - La via per le altissime energie ● ● √s è data dalla somma delle due energie dei fasci. Aumenta linearmente con E , mentre nel bersaglio fisso era proporzionale a √ E . Esistevano già anelli a fasci incrociati per protoni (e antiprotoni), ISR, ma l’energia era bassa, max. √s = 63 GeV, peraltro la più alta mai raggiunta √s = √2mE √s = 2 E

19. Super Proto Sincrotrone del CERN (SPS) E = 450 GeV Tunnel di 7 Km Alla fine degli anni ’70 viene convertito in un collider protone – antiprotone con √s = 540 – 900 GeV !! Accumulatore di antiprotoni Carlo Rubbia Premio Nobel 1984 per la scoperta dei mediatori della forza debole W+ W- Zo Simon Van Der Meer

20. Ma la storia ha inizio qui, a Frascati Colliders e+ e- Bruno Touscheck ADA – LNF 1961 Il primo collider materia-antimateria √s = 400 MeV

22. ADONE – LNF 1967 Some discoveriesmissed … for a lack of energy!

23. SPEAR – SLAC 1972 Burton Richter (with Ting) Nobel Prize 1976 Martin Perl – Premio Nobel 1995

24. Fermilab Tevatron Highest Energy collider: 1.96 TeV top quark, Higgs search, new physics

25. SLAC - SLC and PEPII SLAC Linear Collider (1990-1998) Z-pole, EW physics, B-physics, polarized beams PEPII Asymmetric Storage Ring (1999-2008) 3 GeV e+ on 9 GeV e- Very high luminosity, CP Violation, B-physics, rare decays

26. LEP Accelerator (CERN 1990-2000) • 27 km circumference • 4 detectors • e+e- collisions • LEPI: 91 GeV • 125 MeV/turn • 120 Cu RF cavities • LEPII: < 208 GeV • ~3 GeV/turn • 288 SC RF cavities

27. CERN Large Hadron Collider Collide pp at 14 TeV Higgs, EW symmetry breaking, new physics up to some TeV

28. CERN Complex Old rings still in use Many different programs

29. Proposed 1 TeV e+e- collider Similar energy reach as LHC, higher precision

30. Proton beams production • Gaseous H2 is ionised to have H+ ions • This is done by putting gaseous H2 in a cylinder where a strong electrical field is applied. • First the H2 molecule is broken and then electrons are stripped off. Duoplasmatron

31. Proton beams production @ LHC • Protons should arrive in LHC at 450 GeV. To do this: • LINAC2 (1978, 36 m di lunghezza). From the bottle to 50 MeV • PSB (Proton Syncrotron Booster, 1972, 157 m circunference). Up to 1.4 GeV. • PS: Proton syncrotron (1959, 628 m circunference). From 1.4 to 25 GeV. • SPS (Super Proton Synchrotron, 1976, 7 km • LHC (Large Hadron Collider, 2008, 27 km). Da 450 GeV fino a 7 (0ppure solo 3.5) TeV.

32. Anti-proton beam production • A fraction of protons in the Main Ring (Tevatron, Chigago, USA) , when they are at 120 GeV, are extracted and sent against a target to produce antiprotons • Goal: produce and accumulate large number of anti-protons, reducing momentum spread and angular divergency. In this way, can be transferred with high efficiency into the Main Ring, and after into the Tevatron • To this purpose, antiprotons are focalized through a parabolic magnetic lithium lens, and then transferred to the Debuncher, where the monocromaticity in longitudinal momentum is improved. • Antiprotons are then transferred to the Main Ring and stored there for thousands of pulses. A stochastic cooling system reduces the momentum spread in all 3 directions • When about 6x1011 antiprotons are accumulated, 6 bunches of 4x1010 antiprotons are transferred to the Tevatron

33. Stochastic cooling • Made of several “pickups”, amplifiers and “kickers” • Pickups detect locally a deviation of the Antiproton bunches from main orbit in the Accumulator • Signal coming from the pickups is amplified and sent to kickers located at opposite azimuthal angles along the ring • Kickers produce an electromagnetic field, which corrects the deviation detected by the pickups