1- short pulse neutron source
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
1- Short pulse neutron sourcePulse length: ~ 1s
Repetition rate: 50 – 60 Hz
Average beam power: ~ 1.5 MW
Beam energy: 1 – 8 GeV
Particle type: protons or H-
Spallation Neutron Source (ORNL)
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).
H- source LEBT RFQ CCL SCL HEBTMEBT DTL
StorageRing
Target
90 MeV 200 MeV 1 GeV
352.2 MHz 704.4 MHz
15 m 400 m
3 MeV
WARM PART OF THE LINAC
Ion source LEBT RFQ MEBT
(H-) (3 solenoids) (4-vane, 352 MHz) (Quads, rebuncher, chopper)
5 m 3 m 4 m 4 m
DTL CCL
(Álvarez, 6 tanks, 352 MHz) (4 modules, 704 MHz)
40 m 60 m
SCL
50 keV 50 keV 3 MeV
3 MeV 90 MeV 200 MeV
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
Saclay design of a 5-cells high beta 704 MHz cavity
Medium beta Saclay cavity withits helium tank and tuning system
• Two kinds of cavities depending on the beam energy• = 0.6 cavities up to 400 MeV• = 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)
e
pB
Beam rigidity:
657.5B 651.29B 1 GeV 8 GeV
B = 0.617 T → = 9.168 m → Circ. = 57.6 mMagnetic field Radius Circumference
Only dipoles! We need more space for other elements.
Arc section: 90 m, Straight section: 90 m, Total circumference: 180 m
Storage ring
Cells: 12 → Cell length: 7.5 m, Dipoles/cell: 2 → Total dipoles: 24
angle = 360/24 = 15°r
→ dipole length = 2.4 m sector dipole
Arc section - 3 FODO cells
Arc section
B
gk
k
1f
f4
L
2sin
FODO FODO/Doublet
x (max) = 12 my (max) = 11 m
D (max) = 3.6 mD (rms) = 1.4 m
Qx = 5.29Qy = 5.21
tr = 3.21GeV = 2.1
-10
0
10
20
30
40
50
0 20 40 60 80 100 120 140 160 180s [m]
x,
y,D
[m]
D
x
y
-10
0
10
20
30
40
50
0 20 40 60 80 100 120 140 160 180s [m]
x,
y,D
[m]
D
x
y
x (max) = 45 my (max) = 25 m
D (max) = 3.4 mD (rms) = 2.7 m
Qx = 3.29Qy = 3.17
tr = 3.31GeV = 2.1
kD = -0.589 m-2
kF = 0.573 m-2
kD = -0.498 m-2
kF = 0.501 m-2
FODO
FODO/Doublet
x (max) = 24 my (max) = 17 m
D (max) = 3.8 mD (rms) = 1.4 m
Qx = 6.29Qy = 5.22
tr = 5.11GeV = 2.1
-10
0
10
20
30
40
50
0 20 40 60 80 100 120 140 160 180s [m]
x,
y,D
[m]
D
x
y
x (max) = 16 my (max) = 28 m
D (max) = 4 m
Qx = 6.23Qy = 6.20
tr = 5.23
Parameters of the storage ring at SNS:
kD = -0.637 m-2
kF = 0.778 m-2FODO/Doublet
1 GeV: 35 Neutrons/Proton
8 GeV: 207 Neutrons/Proton
10-9 10-8 10-7 10-6 10-5 10-4 10-3 10-2 10-1 100 10110-7
10-6
10-5
10-4
10-3
10-2
10-1
100
101
Ne
utr
on
s/P
roto
n
Neutron energy [GeV]
1 GeV 8 GeV
Proton beam
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