A Study of the Radiation Tolerance of CVD Diamond to 70 MeV Protons, Fast Neutrons and 200 MeV Pions

Abstract

We measured the radiation tolerance of commercially available diamonds grown by the Chemical Vapor Deposition process by measuring the charge created by a 120 GeV hadron beam in a 50 μm pitch strip detector fabricated on each diamond sample before and after irradiation. We irradiated one group of samples with 70 MeV protons, a second group of samples with fast reactor neutrons (defined as energy greater than 0.1 MeV), and a third group of samples with 200 MeV pions, in steps, to (8.8±0.9) × 1015 protons/cm2, (1.43±0.14) × 1016 neutrons/cm2, and (6.5±1.4) × 1014 pions/cm2, respectively. By observing the charge induced due to the separation of electron–hole pairs created by the passage of the hadron beam through each sample, on an event-by-event basis, as a function of irradiation fluence, we conclude all datasets can be described by a first-order damage equation and independently calculate the damage constant for 70 MeV protons, fast reactor neutrons, and 200 MeV pions. We find the damage constant for diamond irradiated with 70 MeV protons to be 1.62±0.07(stat)±0.16(syst)× 10−18 cm2/(p μm), the damage constant for diamond irradiated with fast reactor neutrons to be 2.65±0.13(stat)±0.18(syst)× 10−18 cm2/(n μm), and the damage constant for diamond irradiated with 200 MeV pions to be 2.0±0.2(stat)±0.5(syst)× 10−18 cm2/(π μm). The damage constants from this measurement were analyzed together with our previously published 24 GeV proton irradiation and 800 MeV proton irradiation damage constant data to derive the first comprehensive set of relative damage constants for Chemical Vapor Deposition diamond. We find 70 MeV protons are 2.60 ± 0.29 times more damaging than 24 GeV protons, fast reactor neutrons are 4.3 ± 0.4 times more damaging than 24 GeV protons, and 200 MeV pions are 3.2 ± 0.8 more damaging than 24 GeV protons. We also observe the measured data can be described by a universal damage curve for all proton, neutron, and pion irradiations we performed of Chemical Vapor Deposition diamond. Finally, we confirm the spatial uniformity of the collected charge increases with fluence for polycrystalline Chemical Vapor Deposition diamond, and this effect can also be described by a universal curve.

Radiation tolerance of diamond detectors

“…The RD42 collaboration irradiated a series of single-crystalline CVD (scCVD) and poly-crystalline CVD (pCVD) diamond samples with protons, pions, and neutrons to characterize the radiation tolerance of CVD diamond [8,9]. After each irradiation the samples were metallized to fabricate strip detectors with a 50 µm pitch.…”

“…The one-parameter description of the data lends itself to a universal damage curve. To combine the data, the fluences were normalized by [9] ϕ 24 GeV p eq = κ i × ϕ i…”

“…The RD42 collaboration has measured the radiation tolerance of CVD diamond against protons, pions, and neutrons of various energies [8,9]. These results are summarized in section 2.…”

“…Figure 1. The 1/λ for scCVD (solid markers)and pCVD (open markers) diamond as a function of particle fluence[9]. Data points of sample j are shifted by 1/λ 0,j to account for the initial collection distance of the sample.…”

“…Relative damage constants for 24 GeV protons, 800 MeV protons, 70 MeV protons, 200 MeV pions, and fast reactor neutrons[8,9].…”