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1- Short pulse neutron source

1- Short pulse neutron source. Pulse length: ~ 1 s. Repetition rate: 50 – 60 Hz. Average beam power: ~ 1.5 MW. Spallation Neutron Source (ORNL). Beam energy: 1 – 8 GeV. Particle type: protons or H -. 3 MeV. 90 MeV. 200 MeV. 1 GeV. H- source. LEBT. RFQ. MEBT. DTL. CCL. SCL.

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1- Short pulse neutron source

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  1. 1- Short pulse neutron source Pulse length: ~ 1s Repetition rate: 50 – 60 Hz Average beam power: ~1.5 MW Spallation Neutron Source (ORNL) Beam energy: 1 – 8 GeV Particle type: protons or H-

  2. 3 MeV 90 MeV 200 MeV 1 GeV H- source LEBT RFQ MEBT DTL CCL SCL HEBT Storage Ring 352.2 MHz 704.4 MHz 15 m 400 m Target Overview • Wf = 1 GeV, If = 1.5 mA (average), then P = 1.5 MW. • Average ion source current estimated to be Is = 2-2.5 mA (in order to account for transverse and longitudinal losses along the LINAC, as well as chopped portions of the beam). • Repetition rate = 50 Hz, Duty Factor = 6%, then Is = 33-42 mA (peak).

  3. WARM PART OF THE LINAC (H-) (3 solenoids) (4-vane, 352 MHz) (Quads, rebuncher, chopper) Ion source LEBT RFQ MEBT 50 keV 50 keV 3 MeV 5 m 3 m 4 m 4 m (Álvarez, 6 tanks, 352 MHz) (4 modules, 704 MHz) DTL CCL SCL 90 MeV 200 MeV 3 MeV 40 m 60 m Normalized transverse emittances estimated to grow from 0.2 pi mm mrad (ion source) to less than 0.5 pi mm mrad (end of warm linac).

  4. RFQ OUTPUT ENERGY The power loss at energies above the neutron production threshold in Cu (~2.6 MeV) is very low (ESS Bilbao RFQ design).

  5. The superconducting Linac • Two kinds of cavities depending on the beam energy • b = 0.6 cavities up to 400 MeV • b = 0.9 cavities for energy up to 1 GeV • Construction of about 10 medium beta cryomodules and 15 high beta cryomodules • Use of 15 bars He system for the 70K thermal shield -> no need of LN2 = only one coolant (helium) Saclay design of a 5-cells high beta 704 MHz cavity Medium beta Saclay cavity withits helium tank and tuning system

  6. Storage ring Beam rigidity: 8 GeV 1 GeV Magnetic field Circumference Radius  = 9.168 m → B = 0.617 T → Circ. = 57.6 m Only dipoles! We need more space for other elements. Arc section: 90 m, Straight section: 90 m, Total circumference: 180 m Arc section Cells: 12 → Cell length: 7.5 m, Dipoles/cell: 2 → Total dipoles: 24 → dipole length = 2.4 m angle = 360/24 = 15° sector dipole Arc section - 3 FODO cells

  7. FODO FODO/Doublet

  8. kD = -0.589 m-2 kF = 0.573 m-2 FODO bx (max) = 12 m by (max) = 11 m D (max) = 3.6 m D (rms) = 1.4 m Qx = 5.29 Qy = 5.21 gtr = 3.2 g1GeV = 2.1 kD = -0.498 m-2 kF = 0.501 m-2 FODO/Doublet bx (max) = 45 m by (max) = 25 m D (max) = 3.4 m D (rms) = 2.7 m Qx = 3.29 Qy = 3.17 gtr = 3.3 g1GeV = 2.1

  9. kD = -0.637 m-2 kF = 0.778 m-2 FODO/Doublet bx (max) = 24 m by (max) = 17 m D (max) = 3.8 m D (rms) = 1.4 m Qx = 6.29 Qy = 5.22 gtr = 5.1 g1GeV = 2.1 Parameters of the storage ring at SNS: bx (max) = 16 m by (max) = 28 m D (max) = 4 m Qx = 6.23 Qy = 6.20 gtr = 5.23

  10. Many materials can be used: lead, tantalum, tungsten • But mercury was chosen: • not damaged by radiation • high atomic number, making a source of numerous neutrons • liquid at room temperature -> dissipate the temperature rise better than a solid Proton beam 1 GeV: 35 Neutrons/Proton 8 GeV: 207 Neutrons/Proton

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