Muons, Inc. 14 Jan 2010 S. Kahn--IR Quads 1 IR Quadrupoles with Exotic Materials Steve Kahn, Muons Inc. Bob Palmer, BNL Don Summers, Ole Miss
14 Jan 2010S. Kahn--IR Quads2 Final Focus Region of E. Gianfelice-Wendt’s New Lattice a (cm)z (m) 5y5y 5x5x QLB1 Note the relatively small quench margin
14 Jan 2010S. Kahn--IR Quads3 Requirements of IR Quads Magnets need to be shielded from EM debris from muon decays. Magnets need to be shielded from EM debris from muon decays. This includes off-momentum decay electrons and synchrotron radiation. This includes off-momentum decay electrons and synchrotron radiation. Tight spacial constraints. Tight spacial constraints. Radial extent of quadrupoles is limited by the detector shielding. Radial extent of quadrupoles is limited by the detector shielding. Quadrupole magnets need to be isolated magnetically from detector solenoid (which could have 4-8 T field). Quadrupole magnets need to be isolated magnetically from detector solenoid (which could have 4-8 T field). Need to prevent the detector solenoid saturating the quadrupole ferromagnetic material. Need to prevent the detector solenoid saturating the quadrupole ferromagnetic material. Space must be allowed for bucking solenoid to cancel detector field. Space must be allowed for bucking solenoid to cancel detector field.
14 Jan 2010S. Kahn--IR Quads4 Further Guidelines for IR Quads Radial aperture of quads should be A=5 max + 1 cm. (From Yuri Alexahin’s talk at the Muon Collider workshop) Radial aperture of quads should be A=5 max + 1 cm. (From Yuri Alexahin’s talk at the Muon Collider workshop) Is this based on field dynamic aperature or losses? We have only ~1000 turns in a muon collider. Is this based on field dynamic aperature or losses? We have only ~1000 turns in a muon collider. Maximum pole tip field is 10 T for Nb 3 Sn coils. Maximum pole tip field is 10 T for Nb 3 Sn coils. YBCO conductor may not be practical because it may not be possible to orient the anisotropic conductor in a quadrupole field. YBCO conductor may not be practical because it may not be possible to orient the anisotropic conductor in a quadrupole field. A study by Bob Palmer shows that the ratio of the coil thickness R to the inner coil radius R is optimized when R/R 2. A study by Bob Palmer shows that the ratio of the coil thickness R to the inner coil radius R is optimized when R/R 2.
14 Jan 2010S. Kahn--IR Quads5 Preliminary G4BL Simulation of Collider Ring IR Magnets Using G4BL to simulate the IR region of Eliana’s New Lattice. Using G4BL to simulate the IR region of Eliana’s New Lattice. e from 750 GeV decays uniformly along the beam line. Muons decay distributions using Michel description. e from 750 GeV decays uniformly along the beam line. Muons decay distributions using Michel description. No synchrotron radiation currently included. No synchrotron radiation currently included. These are included in Geant4, but have not been able to activate them. These are included in Geant4, but have not been able to activate them. Fields are generic multipole fields without fringing end fields. Fields are generic multipole fields without fringing end fields. Preliminary result shows that ~40% of the electron tracks that hit QLB1 hit the magnet face, not the inner aperture. Preliminary result shows that ~40% of the electron tracks that hit QLB1 hit the magnet face, not the inner aperture. These tracks can be removed collimator shields. These tracks can be removed collimator shields.
14 Jan 2010S. Kahn--IR Quads6 Energy Deposition Studies Figure shows MARS simulation (by Vadim Alexakhin) of electron tracks in vicinity of IR quads. Figure shows MARS simulation (by Vadim Alexakhin) of electron tracks in vicinity of IR quads. This should provide the basis of a thermal analysis to determine a temperature profile of these magnets.
14 Jan 2010S. Kahn--IR Quads7 Exotic Pole-tip Materials Certain rare-earth elements have a high magnetization ferromagnetic phase below the Curie temperature. Certain rare-earth elements have a high magnetization ferromagnetic phase below the Curie temperature. As shown in the figure, even above the Curie temperature (20 K) holium has significant magnetization up to 40 K As shown in the figure, even above the Curie temperature (20 K) holium has significant magnetization up to 40 K Note that the very high magnetization exists for the field aligned with one of the crystal directions. Note that the very high magnetization exists for the field aligned with one of the crystal directions. One will not achieve those values by merely driving the metal into saturation with fields that are likely to be achieved in the magnet. One will not achieve those values by merely driving the metal into saturation with fields that are likely to be achieved in the magnet.
14 Jan 2010S. Kahn--IR Quads8 BH Tables Taken from Measured Data Holmium Data Holmium Data Rhodes et al., Phys. Rev. 109, p1547 (1958). Rhodes et al., Phys. Rev. 109, p1547 (1958). Dysprosium Data Dysprosium Data Elliott et al., Phys. Rev. 94, p 1143 (1954). Elliott et al., Phys. Rev. 94, p 1143 (1954). Gadolinium Data Gadolinium Data Elliott et al., Phys. Rev. 91, p 28, (1953). Elliott et al., Phys. Rev. 91, p 28, (1953). These materials may not have been fully saturated since the were limited to about 5 T. These materials may not have been fully saturated since the were limited to about 5 T.
14 Jan 2010S. Kahn--IR Quads9
14 Jan 2010S. Kahn--IR Quads10 Ho Gd Fe yoke Nb 3 Sn W T 4.5 K T 60 K
14 Jan 2010S. Kahn--IR Quads11 Field Along 45° Symmetry Line Aperture Gd Pole Ho Pole
14 Jan 2010S. Kahn--IR Quads12 Permeability of the Rare-Earth Pole Materials
14 Jan 2010S. Kahn--IR Quads13 Saturated Flux Return Yoke
14 Jan 2010S. Kahn--IR Quads14 How Effective are the Rare Earth Poles? As shown the exotic material poles are highly saturated. Are they useful? As shown the exotic material poles are highly saturated. Are they useful? Figure shows a comparison with and without the exotic materials and return yokes Figure shows a comparison with and without the exotic materials and return yokes Model 1: Exotic materials and flux return Model 2: Exotic materials without flux return Model 3:Iron poles with flux return Model 4:No ferromagnetic material
14 Jan 2010S. Kahn--IR Quads15 It is Important to Know the Field at the Coils. This Determines the Coil Technology
14 Jan 2010S. Kahn--IR Quads16 Comments on Conductor Choice In order to achieve the 250 T/m gradient required, we need an effective current density of 240 A/mm 2. In order to achieve the 250 T/m gradient required, we need an effective current density of 240 A/mm 2. This is easily achievable with Nb 3 Sn. This is easily achievable with Nb 3 Sn. This is marginally achievable with NbTi, but because of the high field there is no margin. Also there is no possibility of operating high than 4.5 K. This is marginally achievable with NbTi, but because of the high field there is no margin. Also there is no possibility of operating high than 4.5 K. The J E of YBCO at 4.5 K would be possible in the favorable orientation. It would not be possible in direction. The J E of YBCO at 4.5 K would be possible in the favorable orientation. It would not be possible in direction. Bi-2212 is not possible. Bi-2212 is not possible.
14 Jan 2010S. Kahn--IR Quads17 More Coil Comments Reducing the radial extent of the coils would be advantageous. Reducing the radial extent of the coils would be advantageous. We would like to investigate improving the coil design by taking advantage of the large current density capability of Nb 3 Sn to reduce radial size of the coils. We would like to investigate improving the coil design by taking advantage of the large current density capability of Nb 3 Sn to reduce radial size of the coils. However we must concern ourselves with the quench margin of the conductor. However we must concern ourselves with the quench margin of the conductor. We would like to layout the conductor in a more traditional quadrupole layout as shown. We would like to layout the conductor in a more traditional quadrupole layout as shown. Typical Quadrupole Cross Section with Rutherford style cable
14 Jan 2010S. Kahn--IR Quads18 Conclusions We have examined a single model of a high gradient quadrupole to be used in the IR region using exotic magnetic materials. We have examined a single model of a high gradient quadrupole to be used in the IR region using exotic magnetic materials. Although the gain by using these exotic magnetic materials may seem modest (~7% difference in current density), this could be important in increasing the quench margin. Although the gain by using these exotic magnetic materials may seem modest (~7% difference in current density), this could be important in increasing the quench margin. Although the concept appears to work we need to optimize the design further. Although the concept appears to work we need to optimize the design further.