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IR with compensating and screening solenoids in FCC-ee

IR with compensating and screening solenoids in FCC-ee. S. Sinyatkin Budker Institute of Nuclear Physics 30 October 2015, CERN. What was done. The solenoid fringe field effect is estimated for various solenoid models:

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IR with compensating and screening solenoids in FCC-ee

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  1. IR with compensating and screening solenoids in FCC-ee S. Sinyatkin Budker Institute of Nuclear Physics 30 October 2015, CERN

  2. What was done • The solenoid fringe field effect is estimated for various solenoid models: • - compensating and main solenoid lengths are varied, the sum is kept unchanged; • - compensating solenoid length is varied, the main solenoid length is kept unchanged. • Optimized positions of compensating and screening solenoids. • Checked MAD calculations (EMIT module) of emittance.

  3. L_main/2 L_comp Compensating solenoid is located between IP and QD0 Radius of: - compensating solenoid R = 0.1 m - screening solenoid R = 0.2 m

  4. Variation of main and compensating solenoids lengths Geom. length: 1 – L_comp = 0.5 m 2 – L_comp = 0.6 m 3 – L_comp = 0.7 m 4 – L_comp = 0.8 m 5 – L_comp = 0.9 m 6 – L_comp = 1 m Area of residual field ~ 0.5 m B_comp_max ~1/L_comp Conditions: B_main*L_main+2*B_comp*L_comp=0 L_total=L_main+2*L_comp=const=4 m(geometric length)

  5. Variation of main and compensating solenoids lengths Geom. length: 1 – L_comp = 0.5 m 2 – L_comp = 0.6 m 3 – L_comp = 0.7 m 4 – L_comp = 0.8 m 5 – L_comp = 0.9 m 6 – L_comp = 1 m Bx ~ (L_total_h-L_comp)2/L_comp Conditions: B_sol*L_main+2*B_comp*L_comp=0 L_main+L_comp=const=2 m (geometric length) Bx~ (L_total_h-L_comp)2/L_comp

  6. Estimation of vertical emittance dependence on compensating solenoid length*. Conditions: B_sol*L_main+2*B_comp*L_comp=0 L_main+L_comp=const=2 m (geometric length) I5,y ~ hy5 ~ Bx5 *-Equivalent model is used for MAD simulation

  7. Variation of main and compensating solenoids lengths* *-Equivalent model is used for MAD simulation

  8. Variation of compensating solenoids length Geom. length: 1 – L_comp = 0.5 m 2 – L_comp = 0.6 m 3 – L_comp = 0.7 m 4 – L_comp = 0.8 m 5 – L_comp = 0.9 m 6 – L_comp = 1 m B_comp_max ~1/L_comp Conditions: B_sol*L_main+2*B_comp*L_comp=0 L_main+L_comp is variable L_main=±1 m (geometric length)

  9. Variation of compensating solenoids length Geom. length: 1 – L_comp = 0.5 m 2 – L_comp = 0.6 m 3 – L_comp = 0.7 m 4 – L_comp = 0.8 m 5 – L_comp = 0.9 m 6 – L_comp = 1 m Conditions: B_sol*L_main+2*B_comp*L_comp=0 L_main+L_comp=var. L_main=2 m (geometric length)

  10. Variation of compensating solenoids length* Conditions: B_sol*L_main+2*B_comp*L_comp=0 L_main/2+L_comp=const=2 m I5,y ~ hy5 ~ Bx5 *-Equivalent model is used for MAD simulation

  11. Variation of compensating solenoid length* *-Equivalent model is used for MAD simulation

  12. Optimisation of edge field area Final quads Main detector solenoid 2 Quad screening solenoid 1 4 3 Compensating solenoid 1 – Half of main solenoid length ( 1 m) 2 – Length of compensating solenoid (0.7 m) 3 – Overlap of compensating and screening solenoids (5 cm) 4 – Length of screening solenoid ( 3.95 m) Transverse half size: - compensating solenoid - R = 0.1 m - screening solenoid - R = 0.15 m

  13. Field distribution versus overlap length Overlap length: 1 – 0 cm 2 – 5 cm 3 – 15 cm 4 – 20 cm With overlap length of 5 – 10 cm Edge field Bs<0.01 T in the 10 cm area after end of compensating solenoid Transverse half size: - main solenoidfield - Lgeom = 1 m, Bs = 2 T - compensating solenoid - R = 0.1 m, Lgeom = 0.7 m, Bs~ 2.8 T - screening solenoid - R = 0.15 m , Lgeom = 3.95 m

  14. Beam parameters (E = 45 GeV)

  15. Optic model of solenoids • Piecewise elements have been inserted into 2 m (distance from IP to QD0) • Solenoids are presented by thick elements. • Skew components are thin elements. • Radial and vertical fields are presented by thin elements with nonzero length to carry out emittance calculation by EMIT module (Lrad = 2/N, N – slices number).

  16. Beam Orbit at IR Critical photon energy (E=175 GeV): εc up to 4.9 MeV Radiation angle ~ ± 0.2 mrad Bx_max = 0.24 T

  17. Check of emittance calculation • Formula I2 = 6.07*10-4 m-1 • MAD calculation (EMIT module) Ey = 0.259 pm*rad • Deviation between MAD calculation and formulas increases at short comp. solenoid (strongcomp. field)

  18. Tilt of eigen oscillation modes degree

  19. Summary • Vertical emittancelightly increases when compensating solenoid length decreases with unchanged main solenoid length(2 m). • Slicing allows to take into account fringe fields of the solenoids more precisely. • To exclude leakage of the edge magnetic field into the quadrupole area the length of the compensating solenoid must be reduced to 0.7 m. • For design luminosity the length of the main solenoid should be 1 m, compensating – 0.7 m, the screening solenoid should be overlapped with the compensating solenoid by 5 -10 cm. • The distance between the compensating solenoid end and QD0 quadrupole should be more than 30 cm.

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