[Isotope-prod] Comments on Ga activation rates

[George Kharashvili]

Dear collaboration members,

I did some modeling to include activation rates of various targets mentioned yesterday. Here are some conclusions:
- There is no good reason to increase radiator thickness - 1 to 1.5 mm tungsten is optimal.
- Activation rates presented in the proposal (17 mCi/h/kW at 40 MeV) were calculated for what can be assumed an infinite natural Ga target. Replacing it with other targets results in the following:
3cm diameter, 5 cm long cylinder (m=210g) - 10 mCi/h/50kW
3cm diameter, 10 cm long cylinder (m=420g) - 12 mCi/h/50kW
Truncated cone D1=1.5cm D2=10.6cm H=6.5cm (m=1310g) (currently in the proposal) - 13 mCi/h/50kW
Truncated cone D1=2cm D2=6cm H=10cm (m=800g) - 12 mCi/h/50kW
Truncated cone D1=1.5cm D2=15.5cm H=10cm (m=4110g) - 15 mCi/h/50kW

If we take the smallest of these targets (~200g) and assume 20 hours of 50 kW beam (ignoring decay of Cu-67), we should produce ~200 mCi of Cu-67. This is roughly 260 nanograms, or 1.3 ppb of Cu-67 in our 200 g natural Ga target, which is greater than the 0.5 ppb of Cu content of 99.9999% Ga sample.

I hope this information is useful for the proposal.

--
George Kharashvili
Jefferson Lab Radiation Control
757-269-6435