Optics change requests for Run IIand possible options for 2015

S. Fartoukh Many thanks to

G. Arduini, B. Dehning, M. Giovannozzi, W. Hofle, M. Lamont, E. Métral, S. Redaelli, R. Tomas, J. Wenninger

LBOC 29/04/2015

Just a reminder of some goodies of ATS optics before starting

... for b* levelling from 5 km to 10 cm(... if we had enough aperture and

nothing else to do)

Content

• LHC Optics change requests for Run II• Possible options for 2015• New IR4 optics• Conclusions

LHC Optics change request for Run IIIR Request for post-LS1/2 What is possible? When

?Implications for the optics

IR3IR7

Extract from the tunnel some MQW spares Seems only feasible in IR7 (MQWA module on the IP-side of Q5, provided the MQWB of Q5 is re-wired as an MQWA)

Post-LS2 None till LS2 (except eventual IR re-phasing via the DS only)

IR4 Increase b in D3 (emittance measurement at 7 TeV with BSRT)

Solutions exist in V (350 m), mitigation in H (200 m) but with new phase advance only

Post-LS1 Preferably New IR4 injection optics with new phase to be compensated elsewhere

IR6 90o phase between MKD and TCDQ Solutions exist (with some aperture loss of Dn1~0.5 in Q5) at cst IR phase (or new phase if needed)

Post-LS1 Preferably New IR6 optics (at cst phase or not)

IR2 - 50 cm collision optics with IT @205 T/m - VdM to b*=20 m

- Solutions exist limited at 6.78 TeV with nominal phase, and up to 7.0 TeV but with new phase only - VdM optics is a non-issue whatever the phase

Post-LS1 New collision optics and squeeze sequence in all cases (and possibly new injection optics with new phase)

IR8 - 3 m collision optics with IT @ 205 T/m - New X-scheme for 25 ns- VdM to b*=30-40 m

- Solutions exist at cst IR phase (or new phase if needed)- The New X-scheme is a non-issue (see LMC-167)- VdM optics OK (40 m at the limit)

Post-LS1 New X-scheme in all cases

IR1IR5

- 40 cm collision optics, or even smaller b* for flat optics (e.g. 20 cm) for LHC performance with longer than nominal bunch length or higher than nominal (9.5 )s Xing-angle.- VdM to b*=20 m

- VdM optics is non issue - 40 cm reachable with nominal squeeze sequence, but beyond the limit at 7 TeV (OK for 6.5 TeV). The usage of all MCBXs is needed for X-angle generation at 6.5+TeV- 20 cm not reachable, except with ATS

Post-LS1 None (but crossing scheme),or new OVERALL LHC optics (all IRs and arc optics) both for ATS and fulfilling all the above requests

For the benefits of a new IR4 optics, both for the profile monitors (WS, BSRT, BGI) and ADT, see G. Trad and G. Kotsian @ LS1-LBOC17

Possible options for 2015 (1/2)• Option-min: no optics change w.r.t. 2012 unless absolutely

necessary (25 ns, 6.5 TeV vs. 4 TeV) New Xing scheme in IR1/5 (MCBX) and IR8 (see LMC-167) New IR2 squeeze sequence and collision optics (at cst phase), even for moderate b* reach.

• Option-med: idem as option-min, with New IR4 optics (BGI/BSRT/ADT) with new phase for beam2 compensated by a new IR8-b2 injection optics Eventually new IR6 optics (MKD-TCDQ phase)

• Option-max: overall new injection and collision optics, and crossing scheme, ATS-compatible

Note that the new IR4 optics is not the same for the med and max options, but leading to similar improvements for the BSRT/BGI/ADT...

New injection, collision and VdM optics following option-max are available under /afs/cern.ch/eng/lhc/optics/ATS_2015 Also available is a new LHC injection optics following Option-med

Possible options for 2015 (2/2)

As soon as a decision is taken, a validation period of a few weeks till 2-3 months should be needed

1. For tracking studies (dynamic aperture)2. Collimation (loss maps)3. Failure scenario (in particular new X-scheme in IR8, new MKD-TCT phase)

4. Collective effects (essentially b-b with new IP1/5 phase advance)

Bad surprises are however very unlikely for any of these 3 options. That is why it would be counter-productive not starting with option-max, and then iterate (or downgrade our ambition) in case ...

The deadline for complete optics production and validation (inc. knobs, X-scheme, squeeze and un-squeeze,...) is Oct-Nov 2014.

New IR4 optics for option-max (1/2)• Beam1 • Beam2

D3.R4 D3.L4

Equipment bx old new by old new

D3.L4 173 200 215300BGI 312323 95214

BGI

Equipment bx old new by old new

D3.R4 127 200 334360BGI 271317 213259

BGI

... The beta’s are also increased at the ADT, and within specification at the BPMC’s

New IR4 optics for option-max (2/2)• Beam1 aperture • Beam2 aperture

New n1 (in black) and n1 change (in red) from the nominal to the new optics When dn1<0, the new n1 is always within MEB specification (n1=7 @ QF and n1=6.7 @ QD)

(Biased) Discussions Implementing ATS-compatible optics*) in 2015 has no obvious cons, • both on paper (TBC, the post-LS1 ATS optics proposed being slightly

different from the one for HL-LHC already heavily studied),• for commissioning time (based on ATS MD experience in 2011/12) Pros are • all the known goodies, in particular flat optics for performance with

longer than nominal bunch length, BUT also very large beta*, clean chromatic properties of collision optics including spurious dispersion

• the possibilities to maximize here and there the functionalities of ALL insertions

• (a priori) no other optics changes requested till LS3 & a demonstration (hopefully!) of one of the main HL-LHC concepts.

*) An “ATS-compatible optics” means an optics with specific phasing properties, which is compatible if needed with a telescopic (un-)squeeze to reach very low (or large) b* at IP1 & 5.

Reserve

New IR4 optics for option-med (1/2)• Beam1 • Beam2

D3.R4 D3.L4

Equipment bx old new by old new

D3.L4 173 200 215330BGI 312314 95243

BGI

Equipment bx old new by old new

D3.R4 127 200 334330BGI 271320 213188

BGI

... The beta’s are also increased at the ADT, and within specification at the BPMC’s

New IR4 optics for option-med(2/2)• B1 aperture @ 450 GeV • B2 aperture @450 GeV

New n1 (in black) and n1 change (in red) from the nominal to the new optics When dn1<0, the new n1 is always within MEB specification (n1=7 @ QF and n1=6.7 @ QD)

New IR8 optics for option-med (1/2) For the new X-scheme in IR8, see LMC-167

While IR4-b1 can be re-matched at constant phase, the H phase advance of IR4-b2 shall be reduced by Dmx - 0.08 which is then recovered by using IR8

As a result the beam1/2 phase split between IP1 and IP5 changes by the same amount: is there any impact on beam-beam effect?

New IR8 optics for option-med (2/2)

IT, Q4.R8 & Q5.R8 kept constant No impact on TL optics matching No impact on MKI-TDI phase

Q4.L8 & Q5.L8 modified but at cst Dmy between MKI and TCLIB