1. 1- Short pulse neutron source
Pulse length: ~ 1s
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-

2. 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 = 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 = mA (peak).

3. (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).

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: Arc section 1 GeV 8 GeV Magnetic field
Radius
Circumference
B = T →
 = 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

7. FODO
FODO/Doublet

8. kD = m-2
kF = 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 = m-2
kF = 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

9. Parameters of the storage ring at SNS:
kD = m-2
kF = 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