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
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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)
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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
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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).
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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).
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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)
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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
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FODO FODO/Doublet
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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
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x,
y,D
[m]
D
x
y
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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
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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
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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
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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