Diamond sensors for future high energy experiments Bachmair, Felix
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2016, Letnik:
831, Številka:
C
Journal Article
Recenzirano
Odprti dostop
With the planned upgrade of the LHC to High-Luminosity-LHC 1, the general purpose experiments ATLAS and CMS are planning to upgrade their innermost tracking layers with more radiation tolerant ...technologies. Chemical Vapor Deposition CVD diamond is one such technology. CVD diamond sensors are an established technology as beam condition monitors in the highest radiation areas of all LHC experiments. The RD42-collaboration at CERN is leading the effort to use CVD diamond as a material for tracking detectors operating in extreme radiation environments. An overview of the latest developments from RD42 is presented including the present status of diamond sensor production, a study of pulse height dependencies on incident particle flux and the development of 3D diamond sensors.
Thick (∼100μm) undoped diamond films were grown homoepitaxially on single crystal (SC) diamond substrates by microwave plasma chemical vapor deposition (CVD). To form a freestanding SC diamond film ...(plate), the substrate was pre-ion-implanted with high-energy ion beams before the film growth, and after the thick-film deposition, the substrate was eliminated using a lift-off method, resulting in fabrication of a SC CVD diamond plate. Two samples were prepared; sample 1 was grown on a (001) oriented, nitrogen doped CVD SC diamond at ∼900°C with the input microwave power of 1.7kW, while sample 2 was grown on a (001) oriented, high-pressure high-temperature synthesized type-Ib SC diamond at ∼900°C with the input microwave power of 1.25kW. The formed SC plates have high optical transparencies, indicating no remarkable optical absorptions seen in the wavelength from ultraviolet to near infrared. The photoluminescence (PL) spectra of both samples show strong free exciton FE peaks, while in sample 2 relatively strong optical emissions corresponding to nitrogen related centers were observed in the visible region. After the metal electrodes were formed on both faces of the SC diamond plate to fabricate a sandwich-type diamond particle detector, the energy spectra of 5.486MeV α-particles from 241Am were measured. The charge collection efficiencies (CCEs) of sample 1 were CCE=98% for a hole transport and CCE=89% for an electron transport, respectively, while CCEs of sample 2 were CCE=80% for a hole transport and CCE=78% for an electron transport, respectively. These results indicate that both holes and electrons in sample 2 were trapped much more than those in sample 1. Possible candidates of carrier capture centers are nitrogen and/or nitrogen-vacancy centers observed in PL, nonradiative defect (complex) centers, extended defects such as threading dislocations observed in micrographs taken with polarizers. The different growth conditions most likely affected crystallinity and responses to α-particles of the samples.
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