Oleksiy Dolinskyy May 22, 2013
Outline • Tasks of the CR • Requirements to the ring • Optics solutions • Corrections • Injection / extraction • Overview
FAIR layout
Collector Ring Magnetic rigidity 13 Tm Circumference 221.45 m Structure of a period FODO Number of periods 20 Number of superperiods 2 Number of dipoles 24 of quadrupoles 40 of sextupoles 24 of inj.kickers 3 of extr.kickers 1 of RF cavities 5 (10) of S.C. tanks 5 (2)
The main task of the CR Fast pre-cooling of the hot ion beams coming from separators at the maximum magnetic rigidity of BR=13 Tm. Produced beams on the targets have the large momentum spread and transverse emittance. The CR needs large aperture magnet to collect the maximum possible beam intensity.
Beams from separators 740 MeV/u RIBs 740 MeV/u RIBs 740 MeV/u RIBs 740 MeV/u RIBs 29 GeV protons from SIS100 target station 3 GeV antiprotons CR
Production yield of antiprotons pbars in the ellipse 150 yield = p = 3.82 GeV/c primary protons ∆ p/p = ± 3% 100 2 × 10 -5 Simulations give a yield of pbar/p (only target/horn): For 10 13 proton one gets 2x10 8 pbars 50 240 mm mrad 11 cm Ni target (d = 3 mm) in a graphite container, 0.62 x' [mrad] mm (rms) beam spot. A dramatic improvement of this 0 yield is not possible (without increasing the momentum -50 -40 -30 -20 -10 0 10 20 30 40 50 acceptance of separator/CR). -50 E(p), E(pbar) 29 GeV, 3 GeV -100 acceptance 240 mm mrad, 6% after target protons / pulse ≥ 2 × 10 13 after horn acceptance of separator -150 pulse length single bunch (50 ns) x [mm] Less then 7 % of produced particles on cycle time 10 s the target can be accepted by the pbar separator and the CR
Tasks of the CR Cooling of antiproton beams . From antiproton separator CR ε ⊥ = 240 mm mrad ε ⊥ ≤ 5 mm mrad � 10 sec to the HESR ∆ p/p = 6 % ∆ p/p ≤ 0.1 % Cooling of secondary beams of radioactive ions . From Super-FRS CR ε ⊥ = 200 mm mrad ε ⊥ ≤ 0.5 mm mrad to the RESR � 1.5 sec ∆ p/p = 3 % ∆ p/p ≤ 0.05 % Mass spectrometer of radioactive ions (TOF) . From Super-FRS CR ε ⊥ = 100 mm mrad ∆ ∆ m f � few turns 2 = γ ∆ p/p = 1 % tr m f
First step of cooling- RF bunch rotation Using bunch rotation RF cavity the momentum spread is reduced by factor of 3 Using bunch rotation RF cavity the momentum spread is reduced by factor of 3 Using bunch rotation RF cavity the momentum spread is reduced by factor of 3 Using bunch rotation RF cavity the momentum spread is reduced by factor of 3 P P P- P - - -bars (from 6% to less than 2%) bars (from 6% to less than 2%) bars (from 6% to less than 2%) bars (from 6% to less than 2%) RIBs (from 3% to less then 1 %) RIBs (from 3% to less then 1 %) RIBs (from 3% to less then 1 %) RIBs (from 3% to less then 1 %) Time of such cooling is about 3 Time of such cooling is about 3 Time of such cooling is about 3 Time of such cooling is about 3 ms ms ms ms � p/p=2% � p/p=6% �������������������������� ������ ����������������������� ����� �������������������������� ������ ������������������������������������������ ������ �������������������� �������
Second step of cooling- Stochastic cooling After bunch rotation Stochastic cooling is applied to reduce both the beam emittance and momentum spread X‘ Stochastic cooling X‘ X X ε ε ε ε h,V =240 ε h,V ε ε ε =240 =240 mm mrad =240 ≤ ≤ ≤ ≤ 5 5 5 mm mrad 5 ∆ p/p < ± ∆ ∆ ∆ ± ± 0.05% ± Pbar Pbar Pbar Pbar : Momentum spread : Momentum spread - : Momentum spread : Momentum spread - - - from 2% to 0.1% from 2% to 0.1% from 2% to 0.1% from 2% to 0.1% Emittance Emittance Emittance Emittance - - - - from 240 to 5 mm from 240 to 5 mm mrad from 240 to 5 mm from 240 to 5 mm mrad mrad mrad Cooling time Cooling time Cooling time Cooling time - - - - 10 10 10 10 seconds seconds seconds seconds RIBs: RIBs: RIBs: RIBs: RIB momentum spread from 1 % to 0.05 % RIB momentum spread from 1 % to 0.05 % RIB momentum spread from 1 % to 0.05 % RIB momentum spread from 1 % to 0.05 % mrad (time 1.5 seconds) (time 1.5 seconds) (time 1.5 seconds) (time 1.5 seconds) Emittance from 200 to 0.5 mm Emittance Emittance Emittance from 200 to 0.5 mm from 200 to 0.5 mm mrad from 200 to 0.5 mm mrad mrad Cooling time Cooling time Cooling time Cooling time – – – – 1.5 sec 1.5 sec 1.5 sec 1.5 sec
Requirements to the ring - Three optics must be prepared - Efficient Stochastic Cooling for two optics - High power RF systems for Debuncher - Large acceptances for all 3 optics - Injection / extraction should guarantee large ring acceptance
Stochastic cooling requires: - - - High frequency RF system for signal - High frequency RF system for signal High frequency RF system for signal High frequency RF system for signal processing processing processing processing - High impedance and sensitivity electrodes High impedance and sensitivity electrodes High impedance and sensitivity electrodes High impedance and sensitivity electrodes for Pick- for Pick -Up system Up system for Pick for Pick - - Up system Up system - - - - Dispersion free drift spaces (10 Dispersion free drift spaces (10 Dispersion free drift spaces (10 Dispersion free drift spaces (10- -14 m) - - 14 m) 14 m) 14 m) - - - - Mixing conditions must be close to the Mixing conditions must be close to the Mixing conditions must be close to the Mixing conditions must be close to the ideal (this depends on the ring optics) ideal (this depends on the ring optics) ideal (this depends on the ring optics) ideal (this depends on the ring optics)
Stochastic cooling: Mixing (M) 1 = M ( ) − η δ n n p / p 2 1 M PK ≈ ∞ These are ideal conditions These are ideal conditions These are ideal conditions These are ideal conditions M KP ≈ 1 for mixing for mixing for mixing for mixing 1 1 η = − 2 2 γ γ tr Energy Energy Energy Energy (for pbar γ (for pbar γ=4.2 (3000 GeV) =4.2 (3000 GeV) (for pbar (for pbar γ γ =4.2 (3000 GeV) =4.2 (3000 GeV) Ring parameter depends on Ring parameter depends on Ring parameter depends on Ring parameter depends on For RIB γ For RIB γ=1.86 (740 MeV/u =1.86 (740 MeV/u ) ) For RIB For RIB γ γ =1.86 (740 MeV/u =1.86 (740 MeV/u ) ) the ring optics the ring optics the ring optics the ring optics
Requirements to the ring optics ΔL – path length ∆ L 1 1 D ( s ) ∫ = ρ – bending radius of dipole ds 2 γ ∆ ρ L ( s ) tr PK , KP 0 dispersion function over a half of the ring 0 10 20 25 Isochronous mode (gamma6 γ = 1 . 8 tr tr=1.8) D x (m) Rib mode (gamma6tr=2.9) γ = 2 . 9 tr Pbar mode (gamma6tr=3.8) γ = 3 . 8 tr path length s (m) 0 106 pick-up kicker The arcs are optimased to have a flexible dispersion variation in arcs (D(arc). At least 4 families of quadrupole magnets are required. (D(arc), D‘(arc), D(drift)=D‘(drift)=0)
Stochastic Cooling requires: Phase advance control between PU and KU The quantum number of a phase between Pick-Up and Kicker is required. Phase advance must be 90 0 or plus a multiple of 180 0 . π ( ) ∆ θ = + 2 n 1 PK 2 n=0,1,2… It must be performed both for p-bar and RIB optics i
Stochastic cooling in the CR The The CR The The CR CR CR is is is is designed designed designed to designed to to have to have have required have required required required η η η parameter η parameter parameter parameter both both for both both for antiproton for for antiproton and antiproton antiproton and and RIB and RIB RIB beams RIB beams beams beams. . . . Optic and Optic and positions positions of of PU PU and and KI KI are are optimised optimised to to have have required required phase phase advances advances Optic Optic and and positions positions of of PU PU and and KI KI are are optimised optimised to to have have required required phase phase advances advances between between all between between all pairs all all pairs pairs pairs of of of PU of PU- PU PU - -KI - KI KI KI. . . . 2 Pickup tanks (1-2 GHz) Good mixing 2 Kicker tanks (1-2 GHz) Bad mixing 1 Palmer Pickup tanks 1 – Pickup tank (2-4 GHz) 1 – Kicker tank (2-4 GHz) Palmer cooling PU Pick-Up (1-2 GHz)
Optics solutions
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