1- Short pulse neutron source Pulse length: ~ 1s Repetition rate: 50 – 60 Hz Average beam power: ~ 1.5 MW Beam energy: 1 – 8 GeV Spallation Neutron Source (ORNL) Particle type: protons or H-
Overview Wf = 1 GeV, If = 1.5 mA (average), then P = 1.5 MW. H- source LEBT RFQ CCL SCL HEBT MEBT DTL Storage Ring Target 90 MeV 200 MeV 1 GeV 352.2 MHz 704.4 MHz 15 m 400 m 3 MeV 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).
(Quads, rebuncher, chopper) 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 3 MeV 90 MeV 200 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).
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).
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
Storage ring Beam rigidity: Arc section 1 GeV 8 GeV Magnetic field Radius Circumference B = 0.617 T → = 9.168 m → 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 angle = 360/24 = 15° → dipole length = 2.4 m sector dipole Arc section - 3 FODO cells
FODO FODO/Doublet
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 FODO/Doublet kD = -0.498 m-2 kF = 0.501 m-2 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
Parameters of the storage ring at SNS: 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
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