the carbon-11 gas target design with cooling fins at the cavity for high production yield · ·...
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The Carbon-11 Gas target Design The Carbon-11 Gas target Design with Cooling Fins at the Cavity with Cooling Fins at the Cavity
for High Production Yieldfor High Production Yield
2010. 9. .
Hur, Min Goo
Korea Atomic Energy Research Institute
[18F]FDG 11C-Acetate
[11C]Acetate
Brain tumor Liver cancer
22
Use of C-11
* Image from National Cancer Center[18F]FDG 11C-Acetate
Physical Properties
Half-life 20.4 min.
Decay mode β+(99.76), EC( 0.24)
Emax of β+ 960 keV
Range of β+ in water ~ 4 mm
Principal γ-rays 511(199.6%) keV
20.4 minC-11
β + (99.76%) EC (0.24%)
B-11
33
Properties of C-11
44
Nuclear Reaction of C-11 Production
Nuclear ReactionParticle Energy
(MeV)Theoretical
Yield (mCi/ ¤ h)14N(p,α)11C 12 → 3 9311B(p,n)11C 10 → 0 9210B(d,n)11C 10 → 0 67
Recommended Cross Sections for 14N(p,α)11C Reaction
Considerations in the Gas Target55
Proton Beam
Density Reduction in Gas Target
The major problem in gas target
Unbalance distribution of the target molecules in the cavity
It gives an influence to a production yield
Depend on Power : P (W) = ∆E (MeV) × I (µA)
Methods to Minimize this effect
–Increase cooling efficiency : Conduction, Convection, Radiation
–Increase target pressure
66
Formal Research about Density Reduction77
Beam center Beam center
Beam
reported by D.J. Schlyer & Heselius
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Cylindrical type
• Commercially used
• Simple design and easy to machining
• Clean inner surface
• Occasionally, in case of long target, proton beam loss can be occurred due
to beam scattering
Conical type
• Based on beam scattering
• High production yields
• Basically, it doesn’t suppress density reduction completely
Conventional Gas Target
99
Original object : Increase heat transfer area from metal to fluid
Example : Radiator (Automobile), Chiller, CPU cooler, etc.
Hot temperature
Forced convection
Low temp. fluid High temp. fluid
What is Cooling Fin ?
1010
Object of target cooling : Reduced target gas temperature
The convective heat transfer increased by the added surface area
Best position of cooling fin : Inside of target cavity with θ -direction
hgas << hwater
Target Gas Low Temp
High TempHigh Temp
Cooling Water
Best Position for Gas Target Cooling ?
(cylindrical coordinates)
1111
New Target with Cooling Fin
Grid
Cooling water inlet
Cooling jacket
Ti foil
He gas & Target gas inlet
RI & Vacuum outlet
Cooling wateroutlet
Inside cooling fin
Outside cooling fin
Target length : 150 mm
1212
Target without Cooling Fin : Conical type
Grid
Cooling water inlet
Cooling jacket
Ti foil
Target gas in & out
Cooling water outlet
1313
Target without Cooling Fin : Cylindrical type
Grid
Cooling water inlet
Cooling jacket
Ti foil
He gas & Target gas inlet
RI & Vacuumoutlet
Cooling wateroutlet
Target length : 150 and 250 mm
1414
Targetry for C-11 Production
(Liquid Nitrogen Trap)
Cyclotron, Target and Targetry
KIRAMS-13
• Installed at Chosun University
• 13 MeV Proton, Max 60µA
C-11 Gas Target
1515
1616
Pressure rising of fin target : 2 + 0.2 bar at 10 µA irradiation (1/2 of straight one)
The conical shape shows same pressure development with cylindrical target
Result : Pressure Development
1717
Result : Production Yield
Fin target shows more stable production yield
The fluctuation of conical target yield depend on irradiation condition like unstable
current and cooling
1818
Result : Activity (10µA irradiation)
The production yield of fin target is close to theoretical yield below half life
This result show same result of Dr. Ruth’s experiment using Nb target
Theoretical yield (92mCi/µA)
1919
Conclusion
Cooling fin at the cavity is effective for suppressed target pressure rising and
density reduction effect
These result shows that the production yield depend on target gas cooling
Fin target make it possible to high current irradiation
The heat transfer area is one of the important factor to target design
Above all , cooling fin at the cavity is very useful design for C-11 production
ARTI, KAERI
Thank you for your attention