HL-LHC alternatives R. Tom as, O. Dominguez and S. White Many - - PowerPoint PPT Presentation

HL-LHC alternatives

• R. Tom´

as, O. Dominguez and S. White Many thanks to G. Arduini, P . Baudrenghien,

• H. Bartosik, O. Br¨

uning, X. Buffat, R. Calaga,

• E. Shapochnikova, H. Damerau, S. Fartoukh,
• R. Garoby, G. Iadarola, R. de Maria,
• V. Litvinenko, G. Rumolo and B. Salvant

Review of LHC & Injector Upgrade Plans Workshop October 2013

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Contents

⋆ Assumptions ⋆ Alternatives and merits ⋆ US1 performance ⋆ US2 performance ⋆ Exotic ⋆ Summary & Outlook

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Assumptions

⋆ Efficiency is 50% and it is defined as Nfills Tfill + Tturn−around Trun ⋆ Average fill length is either optimum or 6 hours. ⋆ Turn-around of 3 hours. ⋆ US1 and US2 crossing angles are 10 σ and 12 σ, respectively ⋆ US1 and US2 goals are 170 fb−1y−1 and 270 fb−1y−1, respectively

Rogelio Tom´ as Garc´ ıa HL-LHC alternatives – p.3/25

Alternative 1: 8b+4e

• R. Garoby, H. Damerau

⋆ Double splitting instead of triple splitting in the PS for more bunch charge and 2/3

• bunches. A PSB bunch becomes:

⋆ In the LHC: 1840 bunches with 2.4×1011 ppb ⋆ Details in Heiko’s talk ⋆ First beam tests in injectors in 2014 ⋆ Merits: Significantly lower e-cloud, no cost

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Alternative 1: 8b+4e, lower e-cloud

0.1 1 10 1.3 1.4 1.5 1.6 1.7 1.8 1.9 Heat load (W/m) δmax

25ns (LHC post LS1) 25ns (LHC post LS1 with 4-bunch gaps) Measured HL at LHC (Fill #3429)

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Alternative 2: 200 MHz in LHC

• R. Garoby,
• E. Shapochnikova,
• R. Calaga

⋆ 200 MHz (3 MV) allows to inject more intense longer bunches into the LHC and to have bunch length leveling ⋆ Potential first design of the 200 MHz SC cavities that would work from injection to store.

http://cern.ch/rcalaga/LHCRF/PrelimDraft.pdf

⋆ Merits: 2.5×1011 ppb, σz=15 cm, lower e-cloud, bunch length leveling and significantly lower heating for most LHC devices.

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Alternative 2: SC 200 MHz in LHC

• R. Calaga

The 200 MHz SC quarter-wave cavity is even smaller than the current 400 MHz.

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200 MHz (σz=15 cm) has lower e-cloud

0.1 1 10 1.3 1.4 1.5 1.6 1.7 1.8 1.9 Heat load (W/m) δmax

25ns (US2 baseline) 25ns (US2 with fRF=200 MHz) Measured HL at LHC (Fill #3429)

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US1 performance

N ǫ β∗

x,y

Lyear[fb−1] fill Pile-up 1011 [µm] [cm] Opt. 6h [h] [

1 mm]

US1 1.9 2.62 20,40 181 181 6.1 140 1.5 flatter 1.9 2.62 20,80 169 168 6.6 128 1.1 8b4e 2.4 2.62 20,80 153 150 7.3 141 1.2 50ns 3.5 3.0 20,80 142 118 12 143 1.1 200MHz 2.56 3.0 20,80 232 224 8.1 138 1.1 200MHz 2.56 3.0 20,40 240 228 8.5 138 1.4 8b4e still better than 50ns. 200 MHz has excellent perfor- mance also with lower e-cloud than nominal.

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US1 fill comparison I

1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 0 2 4 6 8 10 ppb [1011] Time [h] 1.8 2 2.2 2.4 2.6 2.8 3 0 2 4 6 8 10 εx [10-6m] Time [h] 1.8 2 2.2 2.4 2.6 2.8 3 0 2 4 6 8 10 εy [10-6m] Time [h] 0.7 0.8 0.9 1 1.1 1.2 1.3 0 2 4 6 8 10 σz [dm] Time [h] 0.2 0.3 0.4 0.5 0.6 0 2 4 6 8 10 βx [m] Time [h] 0.4 0.5 0.6 0.7 0.8 0 2 4 6 8 10 βy [m] Time [h] US1 8b4e 200

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US1 fill comparison II

2 2.5 3 3.5 4 4.5 5 5.5 0 2 4 6 8 10 L [1034cm-2s-1] Time [h] 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 0 2 4 6 8 10 µ [100] Time [h] 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 0 2 4 6 8 10 µpeak [mm-1] Time [h] 0.5 1 1.5 2 2.5 0 2 4 6 8 10 Lint [100fb-1y-1] Time [h] 1.5 2 2.5 3 3.5 0 2 4 6 8 10 ξx [0.01] Time [h] US1 8b4e 200 1.5 2 2.5 3 3.5 0 2 4 6 8 10 ξy [0.01] Time [h] US1 8b4e 200

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US2: CC with 200 MHz?

σz = 15 cm 200 MHz

• 0.6
• 0.4
• 0.2

0.2 0.4 0.6 Longitudinal location [m]

• 40
• 20

20 40 x [µm] σz = 7.5 cm 400 MHz

• 0.6
• 0.4
• 0.2

0.2 0.4 0.6 Longitudinal location [m]

• 40
• 20

20 40 x [µm]

2σ envelopes with β∗=15 cm. CC RF curvature reduces overlap above 1σ for 200 MHz.

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US2 performance

N ǫ β∗

x,y

Lyear[fb−1] fill Pile-up 1011 [µm] [cm] Opt. 6h [h] [

1 mm]

US2 2.2 2.5 15,15 261 232 9.3 140 1.2 200MHz 2.56 3.0 15,15 276 234 11 140 1.3 200MHz (no CC) 2.56 3.0 10,50 255 233 10 139 1.6 200 MHz with CC gives the best performance with lower e-cloud and it is robust against non-working CCs. Can we improve the pile-up density?

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US2 fill comparison I

0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 0 2 4 6 8 10 ppb [1011] Time [h] 1.8 2 2.2 2.4 2.6 2.8 3 0 2 4 6 8 10 εx [10-6m] Time [h] 1.8 2 2.2 2.4 2.6 2.8 3 0 2 4 6 8 10 εy [10-6m] Time [h] 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 0 2 4 6 8 10 σz [dm] Time [h] 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0 2 4 6 8 10 βx [m] Time [h] 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0 2 4 6 8 10 βy [m] Time [h] US2 200 noCC

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US2 fill comparison II

3.4 3.6 3.8 4 4.2 4.4 4.6 4.8 5 5.2 0 2 4 6 8 10 L [1034cm-2s-1] Time [h] 0.9 1 1.1 1.2 1.3 1.4 1.5 0 2 4 6 8 10 µ [100] Time [h] 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6 0 2 4 6 8 10 µpeak [mm-1] Time [h] 0.5 1 1.5 2 2.5 3 0 2 4 6 8 10 Lint [100fb-1y-1] Time [h] 1.5 2 2.5 3 3.5 0 2 4 6 8 10 ξx [0.01] Time [h] US2 200 noCC 1.5 2 2.5 3 3.5 0 2 4 6 8 10 ξy [0.01] Time [h] US2 200 noCC

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Pile-up density leveling?

⋆ The 1st proposal for pile-up density leveling was crab kissing (S. Fartoukh) ⋆ In general, we can level at constant pile-up density rather than at constant luminosity ⋆ This implies lower integrated luminosity ⋆ There are four options:

• β∗ levling with σz=10 cm
• 800MHz + β∗ leveling
• Crab kissing
• 800MHz + Crab kissing

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800 MHz - bunch profile

0.01 0.02 0.03 0.04

• 30
• 20
• 10

10 20 30 density [cm-1] s [cm] Nominal 800 MHz

Assuming 8 MV 800 MHz system to provide 10- 12.5 cm rms bunch length.

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Pile-up leveling in US2 nominal

N ǫ β∗

x,y

Lyear[fb−1] fill Pile-up 1011 [µm] [cm] Opt. 6h [h] [

1 mm]

US2 2.2 2.5 15,15 261 232 9.3 140 1.2 β∗-level 2.2 2.5 15,15 250 232 9.5 142 1.0 800MHz 2.2 2.5 15,15 252 232 9.1 141 0.9 Peak pile-up density can be leveled to 1.0 mm−1 without any new hardware and with little loss in performance. A new 8 MV 800 MHz system can slightly help to reduce the pile-up density.

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Pile-up leveling in US2 with 200 MHz

The first step in 200 MHz is to have a minimum bunch length of 10 cm with flat β∗=7.5, 30 cm, then leveling pile-up density with β∗ is also possible.

N ǫ β∗

x,y

Lyear[fb−1] fill Pile-up 1011 [µm] [cm] Opt. 6h [h] [

1 mm]

200MHz 2.56 3.0 15,15 276 234 11 140 1.3 σz10cm 2.56 3.0 7.5,30 272 233 11 140 1.1 β∗-level 2.56 3.0 7.5,30 272 233 10 141 1.0 Pile-up density can also be leveled to 1 mm−1 with the 200 MHz.

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US2 β∗ Leveling comparison I

0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 0 2 4 6 8 10 ppb [1011] Time [h] 1.8 2 2.2 2.4 2.6 2.8 3 0 2 4 6 8 10 εx [10-6m] Time [h] 1.8 2 2.2 2.4 2.6 2.8 3 0 2 4 6 8 10 εy [10-6m] Time [h] 0.9 1 1.1 1.2 1.3 0 2 4 6 8 10 σz [dm] Time [h] 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 2 4 6 8 10 βx [m] Time [h] 0.1 0.2 0.3 0.4 0.5 0.6 0 2 4 6 8 10 βy [m] Time [h] US2 200

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US2 β∗ Leveling comparison II

3.4 3.6 3.8 4 4.2 4.4 4.6 4.8 5 5.2 0 2 4 6 8 10 L [1034cm-2s-1] Time [h] 0.9 1 1.1 1.2 1.3 1.4 1.5 0 2 4 6 8 10 µ [100] Time [h] 0.7 0.8 0.9 1 1.1 0 2 4 6 8 10 µpeak [mm-1] Time [h] 0.5 1 1.5 2 2.5 3 0 2 4 6 8 10 Lint [100fb-1y-1] Time [h] 1.5 2 2.5 3 3.5 0 2 4 6 8 10 ξx [0.01] Time [h] US2 200 1.5 2 2.5 3 3.5 0 2 4 6 8 10 ξy [0.01] Time [h] US2 200

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Crab kissing

Luminosity Pile-up density

• S. Fartoukh

✄ ✄ ✄ ✄ ✄ ✄ ✄ ✄ ✄ ✗

Using CCs also in the separation plane + 800 MHz pile-up density can be leveled down to 0.65 mm−1.

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Exotic alternatives for US2

Coherent Electron Cooling

• V. Litvinenko

Optical Stochastic Cooling

• V. Lebedev

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Exotic alternatives for US2

⋆ CEC or OSC at store:

• Promising performance
• Challenging hardware, 3 GeV e- for CEC,

60 m undulators for both CEC and OSC

• Never demonstrated

⋆ Coherent electron cooling at injection:

• 1 hour cooling at injection to halve ǫ
• LHeC ERL test facility as cooler
• Never demonstrated, IBS still there
• Performance improvement is marginal

⋆ Experimental tests planned in BNL and FNAL

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Summary & Outlook

⋆ 200 MHz gives the best performance and robustness with lower e-cloud than nominal. ⋆ 8b4e still better than 50ns. ⋆ Pile-up density leveling with β∗ in US2 1 mm−1 possible without any extra hardware (similar for 200 MHz alternative) ⋆ 800 MHz system can slightly reduce pile-up to ≈0.9 mm−1 ⋆ Crab kissing levels pile-up density to 0.65 mm−1 (uses CCs also in separation plane and 800 MHz system)

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