1. PRIMEX Targets

2. Objective: To obtain the “effective” number of 12 C atoms/cm 2 for the Primakoff analysis See Primex Note 28, “Analysis of Primex Targets”, Philippe Martel and Rory Miskimen, for experimental details.

3. Carbon target: Pyrolytic graphite, 9mm thick (5% RL) Low porosity compared to graphite (1% versus 10%) Doesn’t fragment, easier to machine than graphite Natural isotopic abundance, 98.89% Elemental analysis: Proton induced x-ray emission (72 elements) and Combustion (CHNO) Carbon 99.63%Aluminum.006% Hydrogen <.10%Silicon.006% Nitrogen <.05%Chlorine.003% Oxygen 0.19%Calcium.003%

4. Measuring  T for the carbon target:  measured using water displacement technique. Thickness measurements using a ±.05 mil accuracy micrometer.

6. Average the first 5 measurements, and use the error from the 3 rd measurement:  = 2.1979 ±.0006 g/cm 3

7. Block II: 380.40 380.50 380.55 380.50 380.40 380.35 (mils)

8. Target thickness (mil) = 380.4 ± 0.1

9. Target impurities Define an effective carbon areal density N eff (Z=6) = 1.06585 x 10 23 atoms/cm 2 This is about 0.1% higher than what you obtain by assuming everything in the target is carbon.

10. Beam absorption in the target Include this effect in the “effective” target thickness The NIST XCOM data base gives =56.5 g/cm 2 at 5.2 GeV. The estimated error in is ±1.5%. N eff (Z=6) = 1.04606 x 10 23 atoms/cm 2

11. Do we need to worry about magnetic scattering from 13 C in the target? Conclusion: for our purposes 13 C is equivalent to 12 C

12. N eff (Z=6) = 1.0461 x 10 23 atoms/cm 2 ± 0.05% The errors in each experimental parameter were propagated to find the total error in N eff.