FCC – injector complex features…

…with a view to possible Fixed-Target beams

B.Goddard 15/7/14

Outline

• Initial assumptions– Requirements, pre-injector performance, constraints

• HEB tunnel options and features– SPS– LHC– FHC

• Comparison of idealised FT beam performance reach

• Potential issues

Basic assumptions for FCC injectors

• Maximise CERN facility reuse– Add High Energy Booster (HEB) to present LHC injector complex– Not considering an “SPL/PS2-like” option to rebuild full complex

• Take HL-LHC injector chain output for granted– 2.5e11 p+/bunch in 2 mm exy at 25 ns, maximum reach

• FHC: 100 km collider length, 50 TeV/beam– 1e11 p+ per bunch, 25 ns spacing, need to fill ~11’000 bunches

• Evaluate all HEB designs with 2-in-1 magnets, for filling times– May not be realistic for all options– Only one ring assumed for FT beams!

• Filling times calculated assuming present injector complex cycle times (but with increased PS batches in SPS from 4 to 8…)

FHC injection considerations

• Minimum FCC filling time (on paper) should be of order of 10 minutes– Aim to keep this ‘in the shadow’ of FHC cycle time– To note: present LHC could fill both rings in under 10 minutes –

on paper• Injection energy considered around 4 TeV

– 3.2 TeV would give same field ratio (collision/injection) as present LHC

– 1.8 TeV gives same minimum field in T as present LHC– Lower than 4 TeV may penalise FCC (magnet aperture,

instabilities, …)

An FHC injector chain

LINAC40-160 MeV (H-)

PSB0.16 – 2 GeV (x13)

PS2 – 26 GeV (x13)SPS

26 – 450 GeV (x17)

HEB0.450 – 4 TeV (x8)

To FHC4 - 50 TeV (x13)

HEB magnet technology options

Type      Bmax (T) Bdotmax (T/s)  Bmax/Bmin                                 NormCond 2.0 4 40Superferric 2.5 2 40SC (Nb-Ti) low field 5.0 1.4 15SC (Nb-Ti) high field 9.0 0.2 15SC (Nb3Sn) 16.0 0.025 15

SPS (NC) 2.0 1 28.6LHC (Nb-Ti high field) 8.4 0.007 15.6

Existing tunnels and lengths

Parameter unit SPS LHC FHCCircumference m 6912 26659 100000Number dipoles 744 1232Number dipoles 744 1232 4400dipole length (iron) m 6.2 14.3 15bend angle per dipole mrad 8.445 5.100 1.428beam rigidity Tm 1503.17 23337.2Field at injection T 0.117 0.534 1.024Field at top energy T 2.03 8.3 16Magnetic length m 6.253 14.34 15Total dipole length m 4612.8 17617.6 66000Dipole filling factor 0.67 0.66 0.66Ramp time s 10.8 1100Ramp rate T/s 0.1771 0.0071

Options…• Plenty of them….• Starting point for injectors assumes re-use of existing LHC

chain, up to and including SPS– New HEB: should reach 4 TeV and fill FHC in around 10 minutes

• Initial options for evaluation:– 7 km SC machine in SPS:

• High-field 9 T NbTi (only if FHC injection at 2 TeV)• Very high field 18 T Nb3Sn (to reach 4 TeV)

– 27 km existing LHC reuse• Ramp rate to increase by as much as possible: x5 reasonable target?• New 2-quadrant higher voltage powering, new QPS, remove low-b, …• Decommissioning of highly activated zones to study• ..or replacing LHC with low-cost SC or SF machine….?

– 100 km NC/SF machine• 30-60 km of 2-in-1 iron dipole magnets, at least 1000 quadrupoles

Some specific topics for studies• Minimum injection energy (field) in FHC

– 1.8 TeV would open other options for HEB...but probably need 4 TeV• Maximum ‘flat-bottom’ time for FHC

– Need to know if target of ~10 minutes is adequate• Feasibility of HEB in SPS tunnel (if 1.1/2.0 TeV is OK….)

– Integration, ramp rate, 1 or 2 apertures…• Feasibility of LHC reuse for HEB

– Lattice design for simplified 4 TeV synchrotron– Key question of ramping at ~50 A/s. Tests??– Availability (how often were there 4 consecutive LHC ramps??)– Decommissioning feasibility

• Feasibility of HEB in 100 km tunnel– Beam dynamics at 450 GeV injection energy (space charge,

impedance, IBS, …)– Basic lattice needed

• Preliminary cost scaling for magnet systems for all options• Beam transfer, machine protection (both of these get difficult!)

HEB options – SPS tunnelSPS tunnel: SC low-field can reach 1.1 TeV, but 3.2 TeV is tough100 km FHC version

Parameter UnitSC very high 

field SC high field SC low fieldHEB injection energy TeV 0.45 0.45 0.45HEB extraction energy TeV 4.0 2.0 1.1FHC injection dipole field T 1.28 0.64 0.35Ring filling-factor 0.67 0.67 0.67Circumference m 6912 6912 6912Brho at extraction Tm 13365 6698 3698Number of beams accelerated 2 2 2Total magnetic dipole length m 4610 4610 4610HEB Injection dipole field T 2.09 2.09 2.09HEB Extraction dipole field T 18.2 9.1 5.0Dipole technology Nb3Sn NbTi NbTiDipole ramp rate T/s 0.025 0.20 1.40SPS extractions to fill HEB 1 1 1Bunches in HEB 720 720 720HEB extractions to fill FHC 14 14 14FHC bunches 10080 10080 10080HEB stored beam energy MJ 46.1 23.0 12.7HEB stored beam energy / LHC nominal 0.13 0.06 0.04Minimum HEB ramp up+down time s 1290 70 4Minimum FHC filling time (both rings) min 308 23 8

SPS tunnel

HEB options – LHC tunnelLHC tunnel: wide range of possibilities – including reuse of LHC100 km FHC version

Parameter Unit

Reuse existing LHC (SC high 

field) SC low field SF NCHEB injection energy TeV 0.45 0.45 0.45 0.45HEB extraction energy TeV 4.0 4.0 2.1 1.7FHC injection dipole field T 1.28 1.28 0.67 0.54Ring filling-factor 0.67 0.67 0.67 0.67Circumference m 26659 26659 26659 26659Brho at extraction Tm 13365 13365 7031 5698Number of beams accelerated 2 2 2 2Total magnetic dipole length m 17781 17781 17781 17781HEB Injection dipole field T 0.54 0.54 0.54 0.54HEB Extraction dipole field T 4.7 4.7 2.5 2.0Dipole technology NbTi NbTi SF NCDipole ramp rate T/s 0.007 1.40 2.00 4.00SPS extractions to fill HEB 4 4 4 4Bunches in HEB 2560 2560 2560 2560HEB extractions to fill FHC 4 4 4 4FHC bunches 10240 10240 10240 10240HEB stored beam energy MJ 163.8 163.8 86.0 69.6HEB stored beam energy / LHC nominal 0.46 0.46 0.24 0.19Minimum HEB ramp up+down time s 1195 6 1.9 0.7Minimum FHC filling time (both rings) min 89 9 9 9

LHC tunnel

HEB options – FCC collider tunnelFCC tunnel: 2.0/2.5 T NC/SF with 0.33/0.27 filling-factor100 km FHC version

Parameter Unit SF NCHEB injection energy TeV 0.45 0.45HEB extraction energy TeV 4.0 4.0FHC injection dipole field T 1.28 1.28Ring filling-factor 0.27 0.33Circumference m 100000 100000Brho at extraction Tm 13365 13365Number of beams accelerated 2 2Total magnetic dipole length m 27000 33000HEB Injection dipole field T 0.36 0.29HEB Extraction dipole field T 3.1 2.5Dipole technology SF NCDipole ramp rate T/s 2.00 4.00SPS extractions to fill HEB 15 15Bunches in HEB 10800 10800HEB extractions to fill FHC 1 1FHC bunches 10800 10800HEB stored beam energy MJ 691.2 691.2HEB stored beam energy / LHC nominal 1.92 1.92Minimum HEB ramp up+down time s 2.8 1.1Minimum FHC filling time (both rings) min 10 10

FHC tunnel

Baseline option?

• Not yet defined…….but reuse of existing LHC machine has strong “naturalness” arguments in favour, if technically feasible and cost competitive

….so, a digression on reuse of LHC….

Reusing LHC: From this…

Dump

CleaningCleaning

RF/Xing

InjectionB2

InjectionB1

ExtractionTo FCC

P1

P5

P3 P7

P8

P6

P2

P4

To this…?Empty?

RF: need to keep ring 1 and ring2 same length! Min. of 2 crossings

Changes per IR (1-4)

• P1: extraction to collider: – removal of low-beta insertion, ATLAS, construction of floor

through ATLAS cavern, civil engineering for junctions to new TLs to collider, installation of extraction system

• P2: injection of B1 (no crossing)– removal of low-beta and ALICE, modification of injection system

to inject into INNER ring (presently outer!)• P3: collimation – unchanged• P4: RF and new crossing

– Addition of D2 magnets, plus required matching quadrupoles for crossing (not at IP…)

Changes per IR (5-8)

• P5: FODO transport, no crossing– removal of low-beta and CMS, construction of floor through CMS

cavern, installation of FODO quads– Possible location for FT extraction system

• P6: beam dump – unchanged• P7: collimation – unchanged• P8: Injection beam 2 (crossing)

– removal/modification of low-beta and LHCb (2 options still open for crossing – medium beta, or with D2s only)

FT extraction insertion in LHC

• Depends on where transfer to FCC takes place, but would be either P1 or P5

• Not yet looked at any details of extraction system requirements or possible layout

• Likely to be not particularly straightforward to design conceptually….

PoT estimates

• Simple methodology to compare options….• Limit peak power on targets to 2.0 MW

– Maybe slightly pessimistic at this stage (or maybe not!)• Stored energy in beam given by FCC filling constraints• Adjust spill lengths to give 2.0 MW power • Subtract FCC filling time• 80% efficiency for FT physics• Total cycle length and protons per spill then give

maximum PoT per year (if no other limitations)

PoT from cycle length etc.

HEB@ FCC Tunnel16T 9T LHC 5x faster SF SF

Beam energy TeV 4.0 2.0 4.0 4.0 2.1 4.0Total intensity p+ 7.2E+13 7.2E+13 2.6E+14 2.6E+14 2.6E+14 1.1E+15Ramp up/down time s 1290 70 1195 239 2 3Flat top time s 23 12 82 82 43 345HEB filling time min 616 46 89 25 18 20Fraction of time filling FCC (2 per day) 0.85 0.06 0.12 0.03 0.03 0.03Operation days per year 250 250 250 250 250 250FT effi ciency 0.8 0.8 0.8 0.8 0.8 0.8FT cycles per year 2E+03 2E+05 1E+04 5E+04 4E+05 5E+04FT PoT per year 1E+17 1E+19 3E+18 1E+19 1E+20 5E+19FT average power MW 0.004 0.21 0.09 0.4 1.5 1.5Peak power on target during spill MW 2.0 2.0 2.0 2.0 2.0 2.0

LHC tunnelSPS tunnel

e18-e19 p+/year at 4 TeV might be envisaged, in this respect at least….

Extraction of FT beams from HEB

• Slow extraction assumed essential– For experiments (digesting ~e14 p+ in ~100 us…?)– For targets (20-700 MJ on target in ~100 us…?)

• Will be technologically “challenging” for a machine at 4.0 TeV!

1/3 order slow extraction

• Transverse losses typically 0.5 – 1.0 %• Sparking of Electrostatic septa and damage to wires is possible• Spill of 0.1 – 10 sec possible (longer if machine duty-cycle allows)

Stable area in H phase space defined with 6-polesShrink area by approaching tune to 1/3 integerParticles follow separatrices out across septum wireSpiral step at (60 um) wire ~15 mm determines losses

Anodes made of 2080x 60 um W/Re wires

ZS septa in SPS

5 individual anodes, aligned together over ~20 mFor ~300 kW average power, get >10 mSV/h activation…

Possible limitations - i

• Extraction system for 4 TeV– SPS works at 450 GeV– Space in lattice is ~100 m– Beam losses will be 10-20 kW in extraction region

• Equipment performance, activation, radiation damage– Limiting elements are

• Thin electrostatic septa (E field 100 kV/cm, 50 um diameter wires, 15 m active septum length)

• Thin magnetic septa (5 mm thick, 7.5 kA current)

Possible limitations - ii

• Distributed beam losses in SC magnet system– For re-use of present LHC, would appear *very*

challenging to incorporate an insertion with 1% beamloss, while maintaining sufficient cleaning efficiency elsewhere

– For HEB@FCC tunnel, even if HEB is NC or SF, would be sharing a tunnel with 16-20T dipoles….• Maybe need separate parallel extraction straight for HEB for

some 2-10 km, for extraction plus beam cleaning….cost, layout, …

– For HEB@SPS, looks even more difficult to manage extraction losses, as the existing LSS are only 120 m long

Other challenges…

• 4 TeV beam transfer for slow-extracted beams– Losses may make SC magnets difficult, but huge bending radius

with 2 T NC magnets!• Targetry for 4 TeV, 2 MW beams

– 4 TeV beam likely to pose different difficulties compared to typical ~GeV energy of spallation sources

• Shielding and experimental area design• Secondary beamlines• Very long spills…

– Spill quality– Resonance and ripple control– POWER CONSUMPTION (HEB running most of time at top

energy!)– Crystal extraction studies to look at

Conclusions

• Too early for any real conclusions!• e18-e19 PoT/year at 4 TeV ‘could be envisaged’ from time-

sharing arguments, depending on which HEB option• Need to look at feasibility of 4 TeV slow extraction from

these HEB machines– Extraction concept, layout, technology– Losses, collimation, quenches, collider cross-talk– Spill quality and control– Targets– Beam transport – Experimental area– Power consumption, operability

fin

LHC ramp-rate and cycling limitsFactors which could limit the ramp rate for the LHC main dipoles and quadrupoles, between 0.5 and 3.8 T: • Maximum voltage per magnet (and insulation to ground)?

– “900 V for dipoles” (presently ~150 V for ramp-up)• Ramp-induced quench?

– “LHC dipoles could probably work up to 100 A/s (10 times the nominal) from the dB/dt capacity”

• Effects on field quality?– “negligible at 10 A/s, the interstrand resistance is about 5 times larger

than lower acceptable limit. I would expect visible effects (requiring compensation) at 5 times the present ramp-rate, say 50 A/s”

• QPS sensitivity?– “this would be a real bugger. At present thresholds are around 100 to

200 mV, but we have magnets for which aperture compensation does not work well, not really clear why. It may be possible to double the detection threshold, but not much more (i.e. ramps at 20 A/s). Doing better will require new detection architecture”

LHC ramp-rate and cycling limits• Limitation on mechanical lifetime from cycling?

– “Not that I know, but I guess that it should be analysed”• Power loss into cryo system?• Power drawn from network?• Eddy currents in beamscreen?

Additional factors:• Two-quadrants power converters will be needed for all circuits• Compensation rate for the corrector circuits. Higher dB/dt will imply larger

band for the correction controls, higher voltage power supplies. The QPS of the correctors is not compensated, and already at the limit

• Electrical lifetime at higher dielectric stress, not known• No need for the complication of IR's, should be better to change the layout

in those areas

LHC ramp-rate and cycling limitsWhat improvement could be gained by realistic upgrades and what is the associated cost, for example:• Extra powering sectorisation of the arcs (plus SC links etc.)?

– “Additional components required (feedboxes, shuffling modules) will have to fit in the space”

• Cryo power upgrade?– “will be required, but some limits are "built-in" the system (e.g. pipe

diameters and lengths, heat transfer surfaces, flow conditions)”• Replacement of beamscreen e.g. with additional cryo capacity;

– “means removing the complete LHC from its feet”• Additional correction circuits/capacity?• New QPS?

LHC ramp-rate and cycling limitsWhat also limits the overall cycle time for LHC, between 0.5 and 3.8 T, and what could be done about these:• Minimum essential pre-cycle?

– “can be removed”• Persistent current decay times?• Limits on d/dt(dI/dt) or d/dt(dB/dt)?  Could we be limited by the dipole/quadrupole lifetime?• What is the design lifetime of the dipoles/quadrupole?• Can we extrapolate already from the first years' operation to validate

or refine this?• How many 'healthy' dipoles/quadrupoles would we expect to have at

the end of HL-LHC operation?• Could we conceive of a new 3.2 TeV lattice running at e.g. 4.2 T with

10% fewer dipoles, to be used as spares/replacements,?• Can a refurbishment be foreseen?