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PRIMEX Targets
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Transcript of PRIMEX Targets
PRIMEX Targets
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.
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%
• Measuring T for the carbon target:
measured using water displacement technique.
Thickness measurements using a ±.05 mil accuracy micrometer.
Average the first 5 measurements, and use the error from the 3rd measurement:
= 2.1979 ± .0006 g/cm3
Block II:
380.40
380.50
380.55
380.50
380.50
380.40
380.35
(mils)
Target thickness (mil) = 380.4 ± 0.1
Target impurities
Define an effective carbon areal density
)q(F6
)q(F)Z(NZ
)6Z(N 2imPr
26z
21Z
2imPr
2Z
2
eff
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.
Beam absorption in the target
Include this effect in the “effective” target thickness
Te1
T
)T( Teff
The NIST XCOM data base gives =56.5 g/cm2 at 5.2 GeV. The estimated error in is ±1.5%.
Neff(Z=6) = 1.04606 x 1023 atoms/cm2
Do we need to worry about magnetic scattering from 13C in the target?
7
2
22
22
2E
2M22
2
103eargCh
Magnetic
ZcM4
Q
G
GcM4
Q
eargChMagnetic
Conclusion: for our purposes 13C is equivalent to 12C
Neff(Z=6) = 1.0461 x 1023 atoms/cm2 ± 0.05%
The errors in each experimental parameter were propagated to find the total error in Neff.