Feasibility of, and options for, the new MKE kicker concept M.J. Barnes, T. Kramer Acknowledgements: L. Ducimetière, B. Goddard, B. Salvant, J. Uythoven, G. Vanbavinckhove, C. Zannini M. BarnesFeasibility of new MKE system LIU-SPS Open ‘C’ Core MKE Extraction Kicker Review - 20th March

Outline Existing MKEs New MKE Concept – Length of magnet – Rise-time – Dependence of field quality and inductance, for the open-C, upon various magnet parameters – Does it fit in the existing vacuum tank? Ferrite temperature considerations for existing MKE Conclusions M. BarnesFeasibility of new MKE system2

Existing MKEs & Specifications M. BarnesFeasibility of new MKE system Two types of MKE are installed: – MKE-L: H ap =147.7mm, V ap =35mm – MKE-S: H ap =135mm, V ap =32mm MKEs are currently water-cooled. All but 1 are presently serigraphed: this one will be replaced during LS1. V ap H ap 3

New MKE Concept M. BarnesFeasibility of new MKE system Existing MKE New concept The new MKE concept is illustrated, in this presentation, for LSS4 - very similar considerations apply to LSS6. The return conductor could also be elsewhere (see following slides) 4

New MKE Concept M. BarnesFeasibility of new MKE system5  The existing MKE installations operate with a magnet current up to ~3.3kA.  The existing MKE4 maximum operating PFN voltage is ~51.2kV;  The existing MKE6 maximum operating PFN voltage is ~33.1kV.  It is assumed that the present system impedance, of 10Ω, is kept so that existing PFNs and generators can be re-used.  A resistively terminated magnet is preferred as experience shows that this is less likely to flashover than a magnet terminated in a short-circuit.  An operating PFN voltage below ~55kV is preferred, so that standard cables and connectors can be used. A PFN voltage of 50kV, with a 10Ω resistively terminated system, gives ~2.5kA: hence a total magnetic length of 4.5m or more is required for LSS4. Thus 3 or 4 magnets, each of length ~ m, would be used.  Subdividing a total magnetic length of 6m into 4 magnets, each of ~1.5m, each with its own generator, would give a field rise-time of less than 1µs. Assumes 3.6µH/m

45mm Schematic of new MKE concept M. BarnesFeasibility of new MKE system6 An electrically conducting box (not necessarily square – it could have bevelled corners) helps to decouple the beam from the MKE vacuum tank. The magnet return busbar could be either on the LHS of the conducting box, or on the RHS of the ferrite back-leg (as viewed above). Since the ferrite is at high-voltage, the box would not touch the ferrite. Ferrite build-up≈45mm (70mm for existing MKEs) Only DC EM simulations carried out to date. We still need to study (AC or transient) if return busbar should be connected to box or insulated from box.

Conducting Box Near Ferrite M. BarnesFeasibility of new MKE system7 Box “touching” ferrite. By at beam centre: 156mT. Field homogeneity is better than ±1% over a region of 30mm x 18mm. Inductance: 3.0 µH/m. Average flux-density in back leg: 160 mT. By at beam centre: 156mT. Field homogeneity is better than ±0.7% over a region of 30mm x 18mm. Inductance: 3.5 µH/m. Average flux-density in back leg: 191 mT. Box isolated from ferrite & box legs cut- back to be ~48mm from centre of circulating beam. Note: return current modelled in return busbar (not box). ~48mm For HV reasons, the conducting box will not touch the ferrite.

Position of Return Conductor M. BarnesFeasibility of new MKE system8 By at beam centre: 156mT. Field homogeneity is better than ±0.7% over a region of 30mm x 18mm. Inductance: 3.5 µH/m. Average flux-density in back leg: 191 mT. Return busbar behind box.Return busbar behind back-leg. By at beam centre: 156mT. Field homogeneity is better than ±0.7% over a region of 30mm x 18mm. Inductance: 4.9 µH/m. Average flux-density in back leg: 283 mT. From the magnet design perspective, it is advantageous to have the return busbar behind the box.

Effect of Ferrite Nose M. BarnesFeasibility of new MKE system9 By at beam centre: 156mT. Field homogeneity is better than ±1% over a region of 30mm x 18mm. Inductance: 3.0 µH/m. Average flux-density in back leg: 160 mT. No nose on ferrite. By at beam centre: 156mT. Field homogeneity is ±2.5% over a region of 30mm x 18mm. Inductance: 2.9 µH/m. Average flux-density in back leg: 160 mT. Noses, of ~0.5mm height, improve the field uniformity. The height of the aperture may need to be increased to 21mm to allow beam to be bumped past the nose: is this necessary? 2x0.5mm high noses on ferrite.

Existing MKE in Vacuum Tank M. BarnesFeasibility of new MKE system10 End flange of tank

Circulating beam Bumped beam New Concept MKE in Existing Vacuum Tank M. BarnesFeasibility of new MKE system11 Centring circulating beam in tank, with the present alignment of the existing tank, does not allow the beam to be bumped into the MKE aperture – because of the magnet flange. Could the distance between circulating and bumped beam be reduced (e.g. by 5mm)?

YokeYoke TankTank End flange of tank Circulating beam Bumped beam New Concept MKE in Existing Vacuum Tank M. BarnesFeasibility of new MKE system12 a)Move MKE to the right (by ≥ 5mm) in the vacuum tank; b)Move the whole vacuum tank, and contents, to the left (by the same amount). Is it a problem if beam is offset horizontally w.r.t. bellows etc of magnet interconnects?

Ferrite Temperature M. BarnesFeasibility of new MKE system13  MKEs are currently cooled with demineralised water (20-25˚C).  Water cooling allows the MKE to operate with ~twice the beam induced power deposition (ref: AB-Note BT (Rev.2)).  With the expected beam induced power deposition (~2kW/magnet – see Carlo’s talk), for HL-LHC, the estimated (actual) ferrite temperature (see Glenn’s talk) is:  ~110˚C for 25ns beam (uncomfortably close to the Curie temperature);  ~110˚C for 50ns beam (uncomfortably close to the Curie temperature).  Mixed (12˚C) or chilled (6˚C) water would give a reasonable reduction (up to 19˚C) in ferrite temperature.  Back of the envelope calculations indicate that increasing the emissivity of the inside of the MKE tanks (as per the MKIs) could result in a significant radiated power (15-25%), further improving cooling of the ferrite – but current tanks could be radioactive, thus difficult to treat.  Samples of CMD10 ferrite have been obtained for evaluation for possible future use in the MKIs: CMD10 has a Curie temperature of ~250˚C. The samples have been given to the vacuum group for testing. CMD5005 would give a large operating margin, for the MKEs, for HL-LHC. Equivalent to 8C11 CMD10 also has a saturation flux-density (Bs) greater than CMD5005 but has a lower u’ (acceptable for MKIs, but needs to be checked for MKEs)

Conclusions  It is assumed that the present system impedance, of 10Ω, is kept so that existing PFNs and generators can be re-used.  A resistively terminated magnet is preferred as experience shows that this is less likely to flashover than a magnet terminated in a short-circuit.  A total magnetic length of 4.5m or more is required for LSS4. Thus 3 or 4 magnets, each of length ~ m, would be used.  Subdividing a total magnetic length of 6m into 4 magnets, each of ~1.5m, each with its own generator, would give a field rise-time of less than 1µs. Or else a single generator can be used, will give a field rise-time of 3-4µs.  The aperture of the new MKE may need to be increased slightly to allow for a nose on the ferrite – to be discussed.  For the specified bump, the new MKE kicker concept would fit in the existing vacuum tank, but the magnet needs to be off-centre w.r.t. the tank, and the tank moved w.r.t. its present position – is this acceptable? Or can the bump be reduced?  With the existing MKE magnet design, the ferrite temperature would be borderline for HL-LHC, but using chilled water, increasing the emissivity of the inside of the vacuum tank, and/or using a high Curie temperature ferrite would help significantly.  So far new MKE concept looks feasible; studies are on-going…… M. BarnesFeasibility of new MKE system14

M. BarnesFeasibility of new MKE system15 Spare Slides

M. BarnesFeasibility of new MKE system16 Field Uniformity

Beam induced heating estimation cycle time = 21 sBeam-in time = 100 ms Courtesy: Carlo Zannini M. Barnes17Feasibility of new MKE system

Beam induced heating estimation cycle time = 21 sBeam-in time = 100 ms Courtesy: Carlo Zannini M. Barnes18Feasibility of new MKE system

43 C 28 C 23 C 25 April-26 April: 25 ns beam Ecloud studies Courtesy: Carlo Zannini M. BarnesFeasibility of new MKE system19

We assume a bunch length of about 18 cm with the 25 ns beam at flat bottom 25 April-26 April: 25 ns beam Ecloud studies G. Papotti In very good agreement with the measured heating Courtesy: Carlo Zannini M. BarnesFeasibility of new MKE system20

50 ns beam: statistics LHC Fill  T[MKE]/  T[MKEser] M. BarnesFeasibility of new MKE system21 Courtesy: Carlo Zannini