Crab-waist collisions. From lepton to hadron colliders Jos L. - PowerPoint PPT Presentation

John Adams Institute for Accelerator Science Lecture Series Oxford, 21 st March 2013 Crab-waist collisions. From lepton to hadron colliders José L. Abelleira, PhD candidate. École Polytechnique Fédérale de Lausanne (EPFL) Thanks to: R. de Maria, S.Russenschuck, F. Zimmermann (CERN), D.Shatilov (BINP SB RAS,Novosibirsk), C. Milardi, M. Zobov (INFN/LNF, Frascati (Roma))

Contents • The LHC • Flat beams • Crab-waists collisions concept • Crab-waist in DA Φ NE • A new IR for LHC José L. Abelleira 2

The Large Hadron Collider collimators experiments José L. Abelleira 3

LHC final focus system Beam 1 Beam2 Antisymmetric optics due to the opposite direction of the beams José L. Abelleira 4

Luminosity The event rate for a process (number of collisions) is given by the cross section of the process times the luminosity. 𝑒𝑒 𝑒𝑒 = 𝑀σ 𝑞 Luminosity depends on by the beam parameters as follows. 𝑂 2 𝑜 𝑐 𝑔 1 Φ = θσ 𝑨 𝑀 = Piwinski angle 1 + Φ 2 2 σ 𝑦∗ 4 πσ ∗𝑦 σ ∗𝑧 The values for nominal LHC are given 𝑂 1.15x10 11 Particles per bunch. 𝑜 𝑐 Number of bunches. 2808 𝑔 Revolution frequency 11.245 kHz σ 𝑦 , 𝑧∗ Hor/vert beam size at IP* 16.7 μ m σ 𝑨∗ bunch length 7.55 cm 𝜄 Crossing angle* 285 μ m Φ Piwinski angle* 0.64 𝑀 10 34 cm -2 s -1 Luminosity* *For the experiments at IP1 and IP5. José L. Abelleira 5

Normalized separation A crossing angle is introduced to avoid parasitic collisions Even thought there are collisions only in the IP, there are long range interactions between the two beams. A measure of the interaction between the beams is the normalized separation. Δ 𝑡𝑡𝑞 = 𝑒 𝑡𝑡𝑞 ≈ θ σ 𝑦 ′ σ 𝑦 José L. Abelleira 6

Flat beams 3.5 θ θ f=1 Δ 𝑡𝑡𝑞 ≈ σ 𝑦 ′ = 𝑦 f=1.2 3 ε / β ∗ f=1.4 f=1.6 f=1.8 2.5 L (10 34 cm -2 s -1 ) For the same section area σ 𝑦 σ 𝑧 2 Flat beams increase Δ 𝑡𝑡𝑞 , for a given θ 1.5 Less θ for the same Δ 𝑡𝑡𝑞 1 0.5 0 0 5 10 15 20 25 30 35 ( σ x σ y ) 1/2 ( µ m) β 𝑦 = 1.20 m β 𝑦 = 0.60 m β 𝑦 = 1.20 m β 𝑧 = 1.20 m β 𝑧 = 1.20 m β 𝑧 = 0.60 m R. De Maria José L. Abelleira 7

Hourglass effect Beam size is given as σ = εβ . β ( 𝑡 ) = β ∗ + 𝑡 2 β ∗ Especially important when the β function at the IP approaches the bunch length. What is important is the length of the collision section. With Head-on collisions or small φ Length of the Collision section 𝑚 𝑃𝑃 ≈ σ 𝑨 But in Large Piwikinsi Angle (LPA) regime θ 𝑚 𝑃𝑃 ≈ 2σ 𝑦 θ José L. Abelleira 8

Crab-waist collisions An important limitation in hadron machines is beam-beam tune shift β N θσ ξ N ξ ∝ y N φ = ; ξ ∝ ∝ y z ; L ; y σ σ + φ ε + φ σ β 2 x 2 1 ( 1 ) 2 x y x y x A Large Piwinski Angle Φ (LPA) reduces tune shift, allowing N↑ More luminosity reduces the length of the collision section, allowing β 𝑧 ↓ On the other hand, a LPA induces strong X-Y resonances Suppressed by crab-waist scheme José L. Abelleira 9

M. Zobov x β Y With LPA. The Collision Point (CP) for each particle ≠ Interaction Point (IP), (minimum of β 𝑧 ). 4 σ x /θ CP θ σ z * θ z 2 σ z 2 σ x José L. Abelleira 10

M. Zobov x β Y C-W scheme corrects this effect and brings for each particle the IP to the CP. 4 σ x /θ CP θ σ z * θ z 2 σ z 2 σ x José L. Abelleira 11

Crab-waist collisions José L. Abelleira 12

Crab-waist collisions Conditions for the crab-waist sextupole * / β β Δ𝜈 𝑦 = π𝑛 = x x kl Sextupole π θβ β s * Δ𝜈 𝑧 = 2 ( 2𝑜 + 1) strength y y * / σ y * ≥10 * / β y * ≥100 σ x β x 𝜁 𝑦 = 𝜁 𝑧 Suitable for lepton machines ( ε 𝑦 ≠ ε 𝑧 ) More challenging for hadron colliders José L. Abelleira 13

Crab waist collisions in DA Φ NE 900 mA x 500 mA Start of switching off the CW sextupoles in both rings: 200 A  0 A C. Milardi M. Zobov José L. Abelleira 14

Crab waist collisions in DA Φ NE OFF ON Minimum luminosity, highest background when the sextupoles are OFF KLOE background KLOE luminosity monitor DAFNE luminosity monitor C. Milardi M. Zobov José L. Abelleira 15

C-W collisions for hadron colliders There are several facts that make difficult the implementation of crab-waist collisions in LHC: • Same charge of particles • Large L* • Large energy • Same emittance in the two planes A new IR for HL-LHC is presented with the following ingredients: • Large Piwinski Angle • Flat beams • Local chromatic correction ? • Crab-waists José L. Abelleira 16

A new IR for LHC * =1.5 m β x Phase advance from IP * =1.5 cm β y Local chromatic correction in both Δμ x Δμ y planes + crab-waist collisions π /2 π /2 sext1 π /2 π /2 sext2 Chromatic correction CRAB-WAIST SEXTUPOLE sext3 3 π /2 3 π /2 sext1 sext3 sext4 3 π /2 3 π /2 sext4 sext2 sext5 2 π 5 π /2 sext5 Separation magnets The extremely low 𝜸 𝒛 asks for a symmetric optics in the IR José L. Abelleira 17

A new IR for LHC s=0.01 0.5 0.4 0.3 0.2 0.1 mm 0 -0.1 -0.2 -0.3 -0.4 -0.5 -0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5 mm José L. Abelleira 18

A new IR for LHC s=0.01 s=0.05 0.5 0.5 0.4 0.4 0.3 0.3 0.2 0.2 0.1 0.1 mm mm 0 0 -0.1 -0.1 -0.2 -0.2 -0.3 -0.3 -0.4 -0.4 -0.5 -0.5 -0.5 -0.5 -0.4 -0.4 -0.3 -0.3 -0.2 -0.2 -0.1 -0.1 0 0 0.1 0.1 0.2 0.2 0.3 0.3 0.4 0.4 0.5 0.5 mm mm José L. Abelleira 18

A new IR for LHC s=0.01 s=0.05 s=0.1 0.5 0.5 0.5 0.4 0.4 0.4 0.3 0.3 0.3 0.2 0.2 0.2 0.1 0.1 0.1 mm mm mm 0 0 0 -0.1 -0.1 -0.1 -0.2 -0.2 -0.2 -0.3 -0.3 -0.3 -0.4 -0.4 -0.4 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.4 -0.4 -0.4 -0.3 -0.3 -0.3 -0.2 -0.2 -0.2 -0.1 -0.1 -0.1 0 0 0 0.1 0.1 0.1 0.2 0.2 0.2 0.3 0.3 0.3 0.4 0.4 0.4 0.5 0.5 0.5 mm mm mm José L. Abelleira 18

A new IR for LHC s=0.01 s=0.05 s=0.2 s=0.1 0.5 0.5 0.5 0.5 0.4 0.4 0.4 0.4 0.3 0.3 0.3 0.3 0.2 0.2 0.2 0.2 0.1 0.1 0.1 0.1 mm mm mm mm 0 0 0 0 -0.1 -0.1 -0.1 -0.1 -0.2 -0.2 -0.2 -0.2 -0.3 -0.3 -0.3 -0.3 -0.4 -0.4 -0.4 -0.4 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.5 -0.4 -0.4 -0.4 -0.4 -0.3 -0.3 -0.3 -0.3 -0.2 -0.2 -0.2 -0.2 -0.1 -0.1 -0.1 -0.1 0 0 0 0 0.1 0.1 0.1 0.1 0.2 0.2 0.2 0.2 0.3 0.3 0.3 0.3 0.4 0.4 0.4 0.4 0.5 0.5 0.5 0.5 mm mm mm mm José L. Abelleira 18

A new IR for LHC s=0.05 s=0.01 s=0.2 s=0.2 s=0.1 60 0.5 0.5 0.5 0.5 0.4 0.4 0.4 0.4 40 0.3 0.3 0.3 0.3 0.2 0.2 0.2 0.2 20 0.1 0.1 0.1 0.1 mm mm mm mm mm 0 0 0 0 0 -0.1 -0.1 -0.1 -0.1 -0.2 -0.2 -0.2 -0.2 -20 -0.3 -0.3 -0.3 -0.3 -0.4 -0.4 -0.4 -0.4 -40 -0.5 -0.5 -0.5 -0.5 -60 -60 -0.5 -0.5 -0.5 -0.5 -0.4 -0.4 -0.4 -0.4 -40 -0.3 -0.3 -0.3 -0.3 -0.2 -0.2 -0.2 -0.2 -20 -0.1 -0.1 -0.1 -0.1 0 0 0 0 0 0.1 0.1 0.1 0.1 0.2 0.2 0.2 0.2 20 0.3 0.3 0.3 0.3 0.4 0.4 0.4 0.4 40 0.5 0.5 0.5 0.5 60 mm mm mm mm mm José L. Abelleira 18

A new IR for LHC s=0.01 s=0.05 s=0.5 s=0.2 s=0.1 s=0.2 60 60 0.5 0.5 0.5 0.5 0.4 0.4 0.4 0.4 40 40 0.3 0.3 0.3 0.3 0.2 0.2 0.2 0.2 20 20 0.1 0.1 0.1 0.1 mm mm mm mm mm mm 0 0 0 0 0 0 -0.1 -0.1 -0.1 -0.1 -0.2 -0.2 -0.2 -0.2 -20 -20 -0.3 -0.3 -0.3 -0.3 -0.4 -0.4 -0.4 -0.4 -40 -40 -0.5 -0.5 -0.5 -0.5 -60 -60 -60 -60 -0.5 -0.5 -0.5 -0.5 -0.4 -0.4 -0.4 -0.4 -40 -40 -0.3 -0.3 -0.3 -0.3 -0.2 -0.2 -0.2 -0.2 -20 -20 -0.1 -0.1 -0.1 -0.1 0 0 0 0 0 0 0.1 0.1 0.1 0.1 0.2 0.2 0.2 0.2 20 20 0.3 0.3 0.3 0.3 0.4 0.4 0.4 0.4 40 40 0.5 0.5 0.5 0.5 60 60 mm mm mm mm mm mm José L. Abelleira 18

A new IR for LHC s=0.05 s=0.01 s=0.1 s=0.5 s=0.2 s=0.2 s=1 60 60 60 0.5 0.5 0.5 0.5 0.4 0.4 0.4 0.4 40 40 40 0.3 0.3 0.3 0.3 0.2 0.2 0.2 0.2 20 20 20 0.1 0.1 0.1 0.1 mm mm mm mm mm mm mm 0 0 0 0 0 0 0 -0.1 -0.1 -0.1 -0.1 -0.2 -0.2 -0.2 -0.2 -20 -20 -20 -0.3 -0.3 -0.3 -0.3 -0.4 -0.4 -0.4 -0.4 -40 -40 -40 -0.5 -0.5 -0.5 -0.5 -60 -60 -60 -60 -60 -60 -0.5 -0.5 -0.5 -0.5 -0.4 -0.4 -0.4 -0.4 -40 -40 -40 -0.3 -0.3 -0.3 -0.3 -0.2 -0.2 -0.2 -0.2 -20 -20 -20 -0.1 -0.1 -0.1 -0.1 0 0 0 0 0 0 0 0.1 0.1 0.1 0.1 0.2 0.2 0.2 0.2 20 20 20 0.3 0.3 0.3 0.3 0.4 0.4 0.4 0.4 40 40 40 0.5 0.5 0.5 0.5 60 60 60 mm mm mm mm mm mm mm José L. Abelleira 18