Diamond Detectors for Ionizing Radiation - HEPHY

CHAPTER 7. RADIATION HARDNESS 45
2
1.5
d/do
1
0.5
0
0 20 40 60 80 100 120
Dose (MRad)
Figure 7.7: The d c development with electron irradiation, normalized to the initial unpumped
value. (100 MRad = 1 MGy)
corresponds to ten times the expected LHC uence over 10 years at a radius of 7 cm from
the vertex.
7.3.6 Alpha Irradiation
Some diamond samples were also exposed to an intense 5 MeV alpha beam at the Los
Alamos National Laboratory [36]. The range of these particles in diamond is less than
15 m, thus aecting the surface region only. In order to measure the charge collection
in this region, the two electrodes have been applied to the irradiated area on the same
side of the diamond lm. With this geometry, the electric drift eld is restricted to the
surface.
The charge collection distance normalized to the pumped value before irradiation is
shown vs. the uence in g. 7.11. The d c decreases above a uence of the order of
10 12 cm ,2 .
In contrast to the various types of particles mentioned in the previous sections, alpha
radiation will not be signicant attheLHC.
7.4 Comparison
Tab. 7.1 summarizes the collection distance damage introduced by hadronic particles.
The d c values are normalized to the pumped values before irradiation.
Among the hadronic particles, pions showed the worst eect on the charge collection
distance. Comparing the nuclear interaction cross sections of protons and pions with
protons (shown for pions in g. 7.2), it turns out that the 300 MeV c ,1 + have an approximately
ve times higher cross section than 500 MeV c ,1 or 24 GeV c ,1 protons [38].