w.venturini / m.solfaroli

W.Venturini / M.Solfaroli

Preparation for Ions

in LHC

CONTENT:• Beam characteristics and MP concerns

• BI configuration• Operational settings

• Collimators• Planning

• Shift breakdown

Thanks to: P.Baudrenghien, G.Bellodi, B.Goddard, J.J.Gras, D.Jacquet, J.Jowett, M.Lamont, S.Redaelli, F.Roncarolo, M.Sapinsky, R.Steinhagen

Beam Characteristics

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• Bunch intensity = 7x107 ions (5.74 x109 charges/bunch)• Squeezed to 3.5m• Transverse normalized emittance ~1.5/0.8 μm

(nominal/used, for the same beam size as for protons)• First setup with 2 bunches/beam (still safe beam

@3.5TeV) and collisions in all IPs• Nominal filling scheme (128b) for luminosity production

being finalized (see J.Jowett’s slides)

• Energy of the nominal beam (128b) ~400kJ• Possibility of quench in the DSs negligible with this

intensity• SBF reduction factor still to be decided. Proposal for 2 or

2.5 as it’s the maximum we can do while keeping safe beam measurable (2b beam still safe @3.5TeV)

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W.Venturini - M.Solfaroli 3

Beam Instrumentation

SYSTEM RESPONSIBLE COMMENT

Wire Scanner Dehning – SapinskySafe beam for wire damage ~2.2e13 p and ~9.4e9 ions (including safety factor). Last estimation for p 2.8e13No quench at 3.5 TeV with 1e13 p.

BLM Dehning No change is foreseen on threshold

BPM Jones – Lefevre No problem – to be used on High sensitivityBCT – FBCT Ludwig OK

BSRA BoccardiIt should be OK IF the requested MD time for commissioning/check is allocated

BGI Dehning – Sapinsky To be commissioned during the MD

BSRT Roncarolo

Differences in light spectrum and intensity:• 3.5TeV: no problem• 450GeV: ~1/100 signal intensity w.r.t. protons pilot (close to limit of camera sensitivity). Some possible improvement of the setup could give enough signal

Q – Q’ Steinhagen

* Q depends only on 'frev' which supplied via the BST timing system.* Q' depends only on the Q measurement and the dp/p modulation amplitude.‘dp/p -> df’ differences are small but can be re-programmed online if necessary.* FBs operate based on the momentum, distributed by the slow timing system.

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Settings management

• Ramp and Squeeze functions are ready in a dedicated Hypercycle (EARLY-IONS_3.5TeV)

• Most settings identical to protons but:• RF ( functions are ready)• Xing angles in collisions• Collimation

• To minimize the changes, Xing settings maintained as for p throughout INJECTION, RAMP and SQUEEZE:

• Xing angle to be set at:• 0 μrad for IP1 and IP5• -140 μrad (external angle) for IP2. As ALICE wants to flip the

spectrometer polarity during the run the external angle will be later set at +140 μrad

• Same Xing angle as for protons and parallel separation for IP8 (no collision required)

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Collimation system (I)

• If possible, no changes to IP7 and IP3 settings all over the cycle – Cross calibration of orbit reading with protons:

• Inject high intensity p bunch (LOW BPM sensitivity)• Correct against reference orbit• Inject low intensity p bunch and record orbit (HIGH

BPM sensitivity)• Inject an Ions bunch and check that orbit is the same• Define it as Ions reference orbit

– Test ramp with safe Ions beam (2b), collimators at injection settings and OFB on to establish reference orbit up to high energy

– During squeeze use same orbit reference as for protons and measure the optics

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Collimation system (II)

• Subsequent ramp with the same collimator settings as for p till the end of the squeeze, then:

• Keep IP8 separation and Xing angle• Change Xing angles as required in IP1, IP2 and IP5• Set-up of TCTs around new collision orbit

– As a result only one collimator set-up to be done at top energy• Loss maps:

– done in 5 configuration for p– Suggested a minimum of 3 (~4 fills) for Ions @:

• Injection• End of squeeze• Collisions

• SHADOWING OF ZDC…OPEN PROBLEM – to MPP

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Planning

<<We’ll be starting with a machine that already does the equivalent with protons so we should be able to run through many procedures smoothly>>

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Shift Breakdownfrom start to first collisions

J.Jowet

BunchesTotal Time

[days]both rings

Comments

I0 Re-commission protons 1 1Following technical stop, establish orbit with low-intensity BPM settings.

I1 Injection and first turn 1 (0.25) Magnetically identical to protons; 1 bunch/beam.

I2 Circulating beam 1 0.25Magnetically identical to protons. Synchronisation of transfer lines and RF capture at -5 kHz frequency shift. Check lifetime in particular.

I3450 Z GeV initial commissioning

1 0.25Cross-calibration of BPMs from protons. Beam instrumentation setup. Wire-scanner, BGI.

I4450 Z GeV optics checks with two beams

2 (0.5)Magnetically identical to protons but do minimal check of energy matching, beta-beating. >0.4 nominal bunch intensity

I5 450 Z GeV - two beams 2 0.5 Otherwise magnetically identical to protons

I6 Collimation 2 0.5Set-up single stage collimation, loss map to compare with protons.

I7 Ramp 1 0.5Start with two beams, Magnetically identical to protons.Check beam dump at various energies.

I83.5 Z TeV flat top checks

1 0.5Performed following successful ramp. Collimation setup and loss map.

I9Setup for collisions - 3.5 Z TeV

1 0.5Squeeze and transition to zero real crossing angle in ALICE, CMS & ATLAS. LHCb separated, squeezed. Collimation setup.

I10 Loss maps 1 0.5Measure to verify hierarchy appropriate for ion beams. test predictions. Verify protection.

Stable beam 1 (0.1) See machine backgrounds ?

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Shift Breakdownfrom start to first collisions

J.Jowet

BunchesTotal Time

[days]both rings

Comments

TOTAL to prepare

5+(1)

I11First collisions+physics

2 1.5 Ramp with two beams, squeeze, checks

I12 Increase intensity 128 1Increase bunch number to 128 (Early++ Scheme).

Physics 128Parasitic measurements during physics (luminosity evolution, BFPP, etc, ...) to test our models and prepare future runs.

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Open questions

• Transverse emittance:• as low as possible? 0.8 μm?• ADT off?

• Longitudinal emittance:• start without blow-up (in case of need it should be

ready (Philippe B.))

• Re-steering of transfer lines?

• LBDS - special tests?

• Loss maps configuration to be decided

• Shadowing of ZDC…OPEN PROBLEM – to MPP

• LHCb dipole and compensator off?

w.venturini / m.solfaroli

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