The goal of this project is to prove the potential of advanced diamond for large-area, radiation-hard, ultra-fast, and low-material budget detectors, capable of tracking and timing of minimum-ionizing particles. In recent years, it has been demonstrated by the NoRHDia Collaboration in the JRA of HadronPhysics in FP6 that diamond detectors, in particular Homo-epitaxial Single Crystal CVD-Diamond Detectors (HSC-DD) grown on best quality high-pressure high-temperature diamond substrates, combine radiation hardness with excellent energy- and time-resolution. The remarkable characteristics of HSC-DD are a complete homogeneous and fast charge collection, a high drift velocity of both charge carriers, and unique timing signals of a rise time ? 200ps and a thickness dependent FWHM on the order of nanoseconds. However, the limited size of HSC-D samples in conjunction with the actual cost of the material prevents the use of diamond for large-area tracking devices. Therefore, hetero-epitaxial CVD-diamond growth processes are being intensively investigated as means of obtaining wafer-scale Single Crystal Diamond (SC-D) material.

The key issue was to find a material with a similar lattice constant to that of diamond (dDia= 3.567Å), which allows epitaxial orientation of the diamond nuclei. While oriented diamond grains have been achieved on a variety of materials, only Iridium with dIr = 3.834Å combines an extremely high diamond-nucleation density with an excellent alignment of the grains. That has enabled the growth of quasi-single-crystal diamond films by hetero-epitaxy on Iridium. In the subsequent efforts towards SC-D wafers, a further milestone has been reached recently by the realization of large area Iridium films (4-inch diameter) based on the multilayer structure Ir/YSZ/Si(001). In the meantime, preparation of the 4-inch Ir/YSZ/Si(001) substrates is a routine job at the University of Augsburg. However, it turned out that the scaling-up of the diamond-nucleation areas over such large substrates requires substantial engineering efforts.

The project is focused on the growth and the post processing of the samples (removal of substrate and diamond material from the nucleation side, plane parallel polishing), as well as the structural and electrical characterization of the hetero-epitaxial Diamond on Iridium (Dia-on-Ir) plates with respect to detector applications. Using ?- and ⁹⁰Sr sources in the laboratory, we will study the charge collection efficiency (CCE) of the samples and the crucial transient-current (TC) signal shape. The results will be compared to those obtained from polycrystalline CVD-diamond detectors (PC-DD) and HSC-DD. The electronic parameters of Dia-on-Ir will be investigated with small-area (1x1 cm²) pad detectors and their spatial homogeneity over larger plates (2x2 cm²) with strip sensors. It is expected that the results obtained in CARAT can be extrapolated in the future to larger Dia-on-Ir detector devices.

The expertise gained during the FP6 period by the participants of the JRA NoRHDia (without exception included in the CARAT list of participants), guarantees efficient carrying out of the work. Characterization protocols and tools developed and tested in NoRHDia are ready for use.

The diamond work of the “Other Involved Institutions” is invaluable to the CARAT community and vice versa, stimulating a lively scientific discussion and exchange of the actual diamond expert knowledge. Both parties are involved in a variety of other important diamond-detector developments, promoting thereby the common and the individual interests. In addition, they provide the important access to home infrastructures (not included in the HadronPhysics2 Proposal) for beam tests and irradiations.

The operation of the next generation accelerator facilities like FAIR at GSI, the upgrade of the ESRF, the XFEL at DESY, the LHC at CERN and the ILC will require a new generation of detectors with unprecedented performance for beam diagnostics and experiments. In particular, large-area, radiation-hard, ultra-fast, low-material budget, and position sensitive detectors will be needed. The CARAT project aims to investigate and to prepare the way to a prototype for such detectors based on an innovative technology. The CARAT Collaboration attracts scientists from all around the world. The scientific results will be broadly communicated via international conferences and relevant journals.

Over the last decade, development efforts in the production of new CVD-diamond materials for electronic devices including radiation detectors, optical coatings, thermal management, electrochemistry, and bio-electronics, have led to an enormous improvement of the quality of diamond materials and diamond processing technologies. The fruitful cooperation between high-energy physicists, hadron- and nuclear physics researchers as well as the diamond academic and industrial producers, has made a significant contribution to the success of CVD-diamond science and technology in Europe.

Homo-epitaxial Single Crystal Diamond Detector material is at present commercially available from one supplier (Diamond Detector Ltd), acting as a distributor for the De Beers group Element Six, UK. As it is of high scientific and social/commercial importance to increase the number of diamond producers, CARAT supports diamond growth by non-commercial scientific groups. The Dia-on-Ir production and post processing at the University of Augsburg, as well as at MSU and CEA, enables in addition expertise transfer from Universities and Research Infrastructures to European industries.

The R&D activities performed within the CARAT project will provide valuable information for the European electronic industry working on diamond electronic devices. Various scientific groups and infrastructures involved in hadron physics research have already expressed considerable interest in the outcome of the CARAT project. Moreover, the versatility of Dia-on-Ir detectors allows their use in other fields such as radiotherapy, space applications, and the management of radioactive waste.

The CARAT results have the potential to be commercially exploited in two directions: the production of CVD diamonds on large iridium multi-buffer layers and the production of large-area diamond strip-sensors. Standard applications are expected to be tracking devices, time-zero detectors, beam- and beam-halo profile monitors, as well as beam-condition systems. No business agreements or commitments known until now hinder the foundation of new SME’s.