2.3. The isotope 165 Er is a candidate for potential medical applications (Auger Therapy). To obtain it from the decay of its precursor 165Tm, 165Tm is collected for 1 hour at the ISAC Implantation Station. The yield of 165Tm was measured as 2.78.10 10 isotopes/s. The Equivalent gamma dose rate in tissue at 0.5 m of 165Tm is 3.272-10-13 Sv/h/Bq. (a) Calculate the activity of the collected 165Tm. Hint: If the half-life of the collected isotope is much larger than the collection time, it is reasonable to assume that the decay of 165Tm during the collection period is negligible. It makes the calculation a little easier. (2P) (b) Assume that the gamma photons emitted from 165Tm have an energy of 1 MeV(*). Calculate the thickness of lead shielding required to attenuate the Equivalent gamma dose rate in tissue at 0.5 m of the collected activity below 10 Sv/h. The required mass attenuation coefficients (not to be confused with energy absorption coefficients) can be found here: https://physics.nist.gov/PhysRefData/XrayMassCoef/tab3.html (6P) (c) Compare the thickness of lead with the thickness of tungsten required to achieve the same effect. (*) This is an extreme simplification but it can be justified as an upper limit for safety considerations. (2P)