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PRIMEX Targets

PRIMEX Targets. 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. Carbon target: Pyrolytic graphite, 9mm thick (5% RL)

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PRIMEX Targets

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  1. PRIMEX Targets

  2. Objective: To obtain the “effective” number of 12C atoms/cm2 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 rT for the carbon target: • r measured using water displacement technique. • Thickness measurements using a ±.05 mil accuracy micrometer.

  5. Average the first 5 measurements, and use the error from the 3rd measurement: r = 2.1979 ± .0006 g/cm3

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

  7. Target thickness (mil) = 380.4 ± 0.1

  8. Target impurities Define an effective carbon areal density Neff(Z=6) = 1.06585 x 1023 atoms/cm2 This is about 0.1% higher than what you obtain by assuming everything in the target is carbon.

  9. Beam absorption in the target Include this effect in the “effective” target thickness The NIST XCOM data base gives l=56.5 g/cm2 at 5.2 GeV. The estimated error in l is ±1.5%. Neff(Z=6) = 1.04606 x 1023 atoms/cm2

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

  11. The errors in each experimental parameter were propagated to find the total error in Neff. Neff(Z=6) = 1.0461 x 1023 atoms/cm2 ± 0.05%

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