1. LER Workshop, CERN, October 11-12, 2006LER Accelerator Major Components - Henryk Piekarz1 LHC Accelerator Research Program bnl-fnal-lbnl-slac Outline: - Arc magnets - LER-LHC transfer line magnets at IP1 and IP5 - LER RF system at IP4 - LER beam dump system at IP6 - Cost estimate - Tentative schedule - Summary/conclusions LER Accelerator Major Components

2. LER Workshop, CERN, October 11-12, 2006LER Accelerator Major Components - Henryk Piekarz2 Arc main dipole - Super-ferric, combined function dipole based on the VLHC design (Fermilab-TM-2149 6/04/2001) - Four 12 m magnets form the half-cell with interchanging focusing and defocusing units - Two 30 mm gaps for the clock-wise and the counter-clock circulating beams - Full dipole field 1.6 T, and 0.5 T at injection - Gradient +/- 3% - Single superconductor line (53.3 km long) with current of 72 KA (full field) and 15 kA (injection) - Conductor coolant is supercritical liquid helium (4 K, 3 bar, 60 g/s flow) tapped from QRL at few locations

3. LER Workshop, CERN, October 11-12, 2006LER Accelerator Major Components - Henryk Piekarz3 Arc main dipole Lamination is slightly modified from VLHC design to account for a smaller magnetic flux (1.6 T vs 2 T). As measured for the VLHC magnet the sextupole effect is expected to be very small (single units at 10 mm) for the LER operations in (0.5 - 1.6) T. The gap of LER magnet is expanded to 30 mm in order to help minimize beam impedance (Vladimir Shiltsev) and to facilitate batch slipping and bunch coalescing processes (Tanaji Sen) in LER. Arc magnet count: Main dipole 1.6 T 12 m 1640 Dispersion suppressers 1.6 T 8 m 128

4. LER Workshop, CERN, October 11-12, 2006LER Accelerator Major Components - Henryk Piekarz4 Arc magnet conductor A transmission line superconductor energizes all arc combined function dipoles from a single power supply (Steve Hays) with a single pair of leads (Yuenian Huang). The return conductor is used to cancel magnetic field at far distances. Conductor line spans continually for 53.3 km. The critical temperature is 7.2 K for 72 kA full-field current. The quench detection system turns- off all arc magnets in the ring. When by-passing detectors the drive and return conductors pair is assembled into a common cryostat of ~ 25 cm diameter. A coaxial super-conducting cable can also be considered for by-passing detectors.

5. LER Workshop, CERN, October 11-12, 2006LER Accelerator Major Components - Henryk Piekarz5 Arc magnet correctors Every half-cell will have set of corrector magnets. To place them the drive conductor is moved 230 mm up, next to the return conductor thus creating a field-free zone below. Arc magnet correctors and their count (based on the VLHC design): Dipole (Horiz. or Vert.) 0.8T 0.5 m 410 Quadrupole 20 T/m 0.5 m 410 Sextupole 1400 T/m2 0.8 m 410

6. LER Workshop, CERN, October 11-12, 2006LER Accelerator Major Components - Henryk Piekarz6 Transfer line magnets Goals: - Move beams up/down 1350 mm between LHC and LER rings at IP1 and IP5 - Allow LER beams to pass through ATLAS and CMS detector beam pipes - After completion of beam stacking and energy increase to 1.5 TeV enforce circulation in LHC only using a 3 μsec gap between tail and head of bunch train Basic concept of LER-LHC transfer lines (John Johnstone): - In the D1-D2 drift space lift the LER beam to pass over the D2-Q4, and continue lifting to pass over the Q5,6,7 triplet at 1350 mm level above the LHC ring The first step consists of low-field ( < 2 Tesla) and high field ( 8 Tesla) magnets, while the second step consists of 8 Tesla magnets only. The low-field magnets facilitate the LER-LHC beam pipe separation, and are used to enforce beams circulation in the LHC rings only.

7. LER Workshop, CERN, October 11-12, 2006LER Accelerator Major Components - Henryk Piekarz7 Transfer line magnets A sketch of the LER-LHC transfer line magnet arrangement in the IP1 and IP5. The split D1 dipole allows for the horizontal separation of > 110 mm. The fast switching magnets V 1-5 help to separate the LER and LHC beam pipes. The V 6 magnets move the LER beam up enough so the high-field dipoles V 7-10 can be installed (these last magnets do most of the LER beam lifting to its nominal level of 1350 mm above the LHC ring).

8. LER Workshop, CERN, October 11-12, 2006LER Accelerator Major Components - Henryk Piekarz8 Fast switching dipoles Boundaries for magnetic design: 1.Use a single conductor of ~ 1 μH - condition for a 50 kA fast switching power supply (Steve Hays) peak voltage < 50 kV 2.A high-quality B-field (Vadim Kashikhin) of 1.5 T is needed to accommodate magnet string within a beam path of 18 m 3.With half of the field from the core, the supply current for 1.5 T field in a 40 mm magnet gap is ~ 50 kA. Such current can only be sustained by using a low-conductivity copper for conductors using cryogenic cooling (Yuenian Huang) 4.Magnet core must use laminated (< 100 μm) Fe3%Si steel to make magnet operations in a 3 μsec time scale possible Fast switching dipole magnets are the most challenging as they must: (i) Completely switch-off within 3 μsec time frame (ii) Have enough bending power to lift the LER beam by a minimum of 45 mm on more than 18 m path (iii) Provide accelerator quality magnetic field for the LER operations A sketch of magnet, current leads and power supply arrangement

9. LER Workshop, CERN, October 11-12, 2006LER Accelerator Major Components - Henryk Piekarz9 Fast switching dipoles – base option Thorough lamination design is needed to produce high-quality field, but a simple copper bar can be used as conductor (as e.g. in the CERN kicker magnets). B(I) curve for the parallel plate conductor magnet with a 40 mm gap. The core is modeled with Fe3%Si, 100 μm thick laminations. There is no field saturation up to 1.5 Tesla, and a “correctable” saturation up to 2 Tesla.

10. LER Workshop, CERN, October 11-12, 2006LER Accelerator Major Components - Henryk Piekarz10 Fast switching dipoles- base option A conceptual view of a possible fast switching dipole pair mechanical design. Conductor bars are wrapped in 10 layers of 0.3 mm Nomex insulation. The G11 pegs provide support for the conductors and also provide thermal insulation for the magnetic core. A common cryostat (not shown) houses assembly of two magnets, for clock-wise and counter-clock beams.

11. LER Workshop, CERN, October 11-12, 2006LER Accelerator Major Components - Henryk Piekarz11 Fast switching dipoles – option 2 This magnet has simple core design with a conductor of Cos θ type providing excellent field quality. The field lines, however, are heavily crossing conductor. Consequently, conductor must be composed of multiple laminated wires. R&D effort is required to prove performance.

12. LER Workshop, CERN, October 11-12, 2006LER Accelerator Major Components - Henryk Piekarz12 Other possible LER-LHC beam separating dipoles The Lambertson type magnet can be used when the LER-LHC beams are separated enough so the LHC beam will pass through a field-free zone. This magnet could possibly be used to replace the last stage of the fast switching magnets (before the beam pipes separation), and help in this way to minimize required number of switching power supplies. This magnet requires considerable magnetic design effort, and its mechanical design with 3 conductors is challenging as well. But as the fast switching magnet supply strongly dominates the cost it may be worthy an effort.

13. LER Workshop, CERN, October 11-12, 2006LER Accelerator Major Components - Henryk Piekarz13 Other transfer line dipoles After a 75 mm separation between LHC and LER beams is achieved a single-conductor dipoles will be used to increase this separation to 170 mm, so the LER and LHC beam pipes will be outside the magnet cores. Then two-bore, 8 T, superconducting dipoles will be used to lift LER beam to 1350 mm above LHC ring.

14. LER Workshop, CERN, October 11-12, 2006LER Accelerator Major Components - Henryk Piekarz14 Transfer line magnets list Magnet and power supply count of vertical dipoles for one side of the IP region using the squared conductor magnet and the John Johnstone’s transfer line design as a model. For all single conductor magnets the operational current is 55 kA. Magnet size [mm x mm] LER beam vertical lift [mm] Magnet length [m] Field [T] Inductance [μH] Peak Voltage [kV] Number of magnets Number of supplies 40 x 40 0 – 5.5 1.6 1.46 1.3 40 4 4 40 x 50 5.5 – 16.2 1.4 1.46 1.5 43 3 3 40 x 60 16.2 – 27.6 1.3 1.46 1.6 46 2 2 40 x 70 27.6 – 36.6 0.9 1.46 1.3 40 2 2 40 x 8036.6 – 46.2 0.8 1.46 1.3 40 2 2 30 x 3075.0 – 170.0 2.0 1.95 - - 6 1 30 x 30170.0 – 1350.0 1.5 8.00 - - 10 1

15. LER Workshop, CERN, October 11-12, 2006LER Accelerator Major Components - Henryk Piekarz15 Large bore D1 dipole As in the first pair of fast switching dipoles in the LER-LHC transfer line the separation of the clock -wise and counter-clock beams is 110 mm, the D1 dipole bore width must be no less than 140 mm. So, we consider D1 dipole aperture 140 mm, central field 8 T and length ~ 9 m. We asses the feasibility of such a dipole by comparing to MFRESCA large aperture dipole (10 T, 88 mm bore). Feasibility analysis by Giorgio Ambrosio using magnetic design scaling laws (E.Todesco, L.Rossi) which agree within few % with existing dipoles. - As shown in figure on the left the 8 Tesla dipole of inner radius of 70 mm is feasible with a 2-layer conductor design using 15-16 mm wide cables (assuming reality factor of 85% ) - Force ratio MFRESCA/D1 = 0.982, so using the same mechanical design is adequate - Quench energy ratio MFRESAC/D1 = 0.617, so quench protection may be challenging. But as the ratio of energy density = 0.982, using a fast quench detection system, large heater coverage and selecting properly cable strand thickness, the quench protection can be made adequate.

16. LER Workshop, CERN, October 11-12, 2006LER Accelerator Major Components - Henryk Piekarz16 RF system for LER at IP4 To ease a combined LER-LHC operations during the beam transfer the LER will have its own RF system. We propose to use the LHC RF system design. With modifications the LER cryostats could be placed above the LHC ones, but better in the space between LHC D3 dipole and LHC RF cryostat. The D3 and D4, LER dipoles, will provide the 420 mm beams separation at IP4 required for the RF cavities operation.

17. LER Workshop, CERN, October 11-12, 2006LER Accelerator Major Components - Henryk Piekarz17 Beam dump for LER at IP6 As the LER maximum beam energy is 1.5 TeV a 5 times scaled down version of the LHC kicker magnet system is needed to allow the aborted beam to clear the Q4 and Q5 quads on its way to the beam dump. Some adjustment in horizontal plane may also be needed to hit the center of the beam dump.

18. LER Workshop, CERN, October 11-12, 2006LER Accelerator Major Components - Henryk Piekarz18 LER component cost estimate Cost estimate is based on an extensive cost studies for the VLHC in 2001, but corrected for increase of cost of basic raw materials between 2001 and 2006 (e.g. steel by 30%, Cu 500%). System [$M] Main arc magnets 64 Arc corrector magnets 4 Fast switching magnets 28 Other transfer line magnets (including D1) 14 Beam dump magnets 8 RF system 10 Beam pipe vacuum system 16 Cryogenic support 8 Total 152

19. LER Workshop, CERN, October 11-12, 2006LER Accelerator Major Components - Henryk Piekarz19 Tentative schedule Activity Time [Y] Lapsed time [Y] LER accelerator design 1 1 Prototyping & testing transfer line magnets 2 2 Preparation of arc magnet industrial production 1 2 Magnet production 3 5 Magnet installation in the tunnel 2 5 LER commissioning 1 6 The schedule shown below is based on VLHC studies, and experience with fabrication of two arc magnet core prototypes (12 m length) and testing a 1.5 m long prototype.

20. LER Workshop, CERN, October 11-12, 2006LER Accelerator Major Components - Henryk Piekarz20 Summary and conclusions  We have shown that main components of the LER accelerator can be prototyped and prepared for industrial fabrication without additional R&D effort, though some R&D may help reduce cost  The estimated cost of main LER accelerator components is within a range of 50% of yearly cost of Tevatron operation, and likewise probably about 25% of LHC one  The time scale for component fabrication and LER installation in the tunnel is probably consistent with the physics program during first 5-6 years of LHC operations