The prime novelty of large-area CVD Diamond-on-Iridium (Dia-on-Ir) detectors is the combination of hitherto unobserved timing properties with an almost homogeneous crystal structure. The proposed HP3-WP15 ADAMAS focuses on the continuous improvement of quality and post-processing of Dia-on-Ir materials grown at the University of Augsburg (UA, GSI, ESRF, IAF, DM, and UJohannesburg) and on the design and development of new state of the art detectors with appropriate RF electronics for advanced diamond assemblies (ADAMAS) (sensors + front-end electronics (FEE)) (GSI, INFN, DESY, European XFEL, UGlasgow, VERA, CEA, PTW, Kurchatov, RBI, UHuelva, and USurrey). The main applications foreseen are the tracking and the ToF of relativistic heavy ions and protons in FAIR experiments as well as similar applications at LHC and future colliders, for which the results are already very promising. Analytical calculations and computer simulations are ongoing in order to develop a standard code/model to optimize the design parameters of the assemblies. For radiation hardness studies, a well-established quantum kinetic theory based on a generalized Boltzmann-type equation for describing the microscopic laser damage mechanisms in materials will be adapted to obtain a theoretical approach for the interaction of intense charged beams with diamond materials (INRNE Sofia, KIT Karlsruhe). In the framework of the HadronPhysics2 WP15 CARAT, samples with unrivalled structural properties for heteroepitaxial diamond have been generated (for the first time) on areas as large as 2 x 2 cm2 (target size ˜ 4 inch wafers). The original signal response of the ‘early’ Dia-on-Ir sensors to ionizing radiation turned out to be unexpectedly fast (trise < 200 ps, FWHM < 300ps) and with rather high amplitudes, comparable to the amplitudes of homoepitaxial single-crystal CVD-Diamond (scCVDD) sensors. However, the charge-collection efficiency (CCE) of these ‘early’ crystals was measured to be approximately 20% for sensors of thickness dD ˜ 300µm. This result was in good agreement with the data published for Dia-on-Ir detectors produced and installed at MSU for heavy-ion beam tracking but far from the anticipated target efficiency of CCE = 80 %. Chemical impurities could be excluded as the origin of this disadvantageous property. The extremely low dark current of Idark ˜ 5 x 10-14 A measured up to very high electric fields of ED > 4V/µm showed an Ohmic I vs. ED characteristic that indicates that these are high-quality sensors with ‘non-blocking’ contacts. Concerning the low CCE, the most probable hypothesis was the high dislocation density observed in birefringence images of the crystals. Nevertheless, these controversial observations could not be understood with a simple model of a defective charge-trapping diamond material. It turned out that none of the FEE used to characterize pc and scCVDD detectors was capable of processing properly the ultrafast Dia-on-Ir signals. The amplifiers exhibit high ballistic deficits, which were obvious for both readout methods applied: (i) the charge-sensitive signal processing and (ii) the broadband readout. In both type of measurements, ion spectroscopy and transient current technique (TCT), respectively, the collected charge and the corresponding CCE were strongly underestimated. It was in particular the shape of the ‘original’ ?-signals measured with Diamond Broadband Amplifiers (DBA; Ri = 50 ?, BW = 2.3 GHz) and recorded with a Digital Sampling Oscilloscope (DSO) of 3 GHz BW and of 20GS/s sampling rate, which underlined these findings: the short pulses revealed a ?-like increase followed by a damped oscillation. According to present simulations, an optimized assembly is a low-capacitance setup of accurately minimized detector and parasitic capacitances. It consists of a micro-patterned diamond sensor (channel CD << 1pF); a low-noise broadband amplifier of low input- transistor capacitance Ci ˜ 0.2 pF; and a relatively high impedance of Ri ˜ 500 ? and bandwidth BW >> 2 GHz. We partially realized and tested these parameters using a special assembly consisting of a Dia-on-Ir sensor with a thickness of 12 ?m and a DBA modified for BW = 3.4 GHz. The detector signals induced by 241Am-?-particles were recorded with a 6 GHz DSO of 20 GS/s sampling rate. The ‘original’ signal appeared much better reproduced, showing a smooth exponential decay and a CCE which was higher by a factor of two. Note that this appreciable improvement is still dominated by the 50 ? impedance of the modified DBA (limiting the signal amplitude) and by the high parasitic capacitances of the modular setup. The development of assemblies accounting in addition to a higher BW to higher amplifier impedance and low capacitances (LCBBA) is one main issue in ADAMAS. The essential prerequisite for advanced diamond assemblies is clearly a high-quality sensor material. Recently, a significant milestone has been achieved in the University of Augsburg: the CCE of the latest Dia-on-Ir samples of thickness dD ˜ 300 µm delivered is almost 60 % when measured with the modified DBA. The intrinsic time resolution, which has been tested for the first time in a recent experiment with 40Ar ions of E = 200 AMeV, was ?i = 25 ps, which corresponds to the resolution of the Philips TDC used. In fact, Dia-on-Ir crystals grown with a thickness of 1mm now approach the quality of non- highly selected IIa type natural diamonds, for which a dislocation density of 109 /cm2 has been also reported. As found in former work for homoepitaxial scCVDD plates, crystal dislocations significantly deteriorate the CCE. In that sense, the present Dia-on-Ir materials can be classified as ‘ultrafast, defective, single-crystal diamond’. The ADAMAS work sub- packages include a focus on further reduction of the dislocation density of the heteroepitaxial Dia-on-Ir layers. Epitaxial Lateral Overgrowth (ELO) is a powerful concept that successfully has been applied for dislocation reduction in alternative heteroepitaxial material systems like GaN. The technique involves the deposition of a patterned mask containing windows of a specific geometry. The subjacent functional material (here diamond) grows first through the windows and then spreads laterally. Dislocations within the window area of the mask are perpetuated while those below the mask are stopped. The efficiency in dislocation reduction is essentially controlled by the fill factor, which is given by the ratio of the open to the covered areas. We will apply various geometries, mask materials, and growth conditions to explore the ELO potential for diamond. The samples will be comprehensively characterized with respect to structural and chemical defects as well as for their electrical properties which are of paramount interest for detector applications. The HP3-WP15 ADAMAS is indispensable to enlighten us about the real potential of Dia-on-Ir for detector applications. Moreover, it is of high scientific interest to clarify if there are different dark-current mechanisms and/or charge-generation and transport processes, hitherto unobserved in standard pcCVDD and scCVDD sensors. It will also provide a global understanding of ultra-fast signal readout, which can be adapted to many other RF applications. The theoretical approach to the radiation hardness of diamond sensors is an urgently missing part of the theory and of general importance for all diamond detectors. .


Engineering of Dia-on-Ir plates of minimized dislocation density
Development of pad assemblies with new single-channel amplifiers
Development of one-dimensional microstrip assemblies with PADI-4
UA, UGlasgow

Test of ELO concept on Dia-on-Ir films. Characterization of structural and electronic properties. Production and post processing of 3 x 3 cm² samples for detector applications.


Evaluation of a new low capacitance broadband amplifier (LCBBA). Masks and metallization of pad motifs. Assembly tests and optimization using ?- and ?-sources. Beam tests with relativistic ions and protons: rate capability (RC), time (T) and energy (E) resolution.


Masks and metallization of strip motifs on 3 x 3 cm2 Dia-on-Ir samples for differential readout with PADI-4 ASICs. Assembly tests and optimization using ? and ? sources. Beam tests with relativistic ions and protons: RC, T, E, and position (POS) resolution.



Delivery month from start date

Pad assemblies with new single-channel LCBBA signal readout


3 x 3 cm2 Dia-on-Ir samples of low dislocation density


Microstrip assemblies with PADI-4 signal readout and CBM DAQ



Single-crystal or quasi single-crystal CVD diamond is a unique engineering material. Its application as active detector medium makes the highest demands on the structural and electronic quality of the diamond crystals. Nuclear and high-energy physicists involved in the development of CVD-diamond detectors are contributing significantly to the electrical characterization of high-quality diamond materials and, due to this, to the improvement of the growth processes both in industrial and in non-profit research institutions. Furthermore, they are developing the FEE for diamond detectors, which is most important as such needed FEE is still not available on the market. In the last years, a considerable increase of demand on radiation hard advanced diamond assemblies has been noticed. At GSI, a variety of applications have been pursued and different scientific groups (Atomic Physics (AP), Plasma Physics (PP), HADES, FOPI, FRS, ESR) are using the devices in physics experiments, or they have implemented them for the study and the commissioning of accelerator components (UNILAC and SIS bunch and spill structure monitors) and decelerating structures (HITRAP facility). More diamond devices are in preparation for FAIR experiments: HADES; CBM; FLAIR; SPARC; R3B; HISPEC; DISPEC; the measurements of Kaons and Double Hypernuclei; BIOMAT purposes, and more. At CERN, all LHC experiments have installed diamond detector systems for beam condition monitoring. Diamond X-ray monitors are being developed for the light sources for research with photons at DESY (PETRAIII; FLASH), the European XFEL as well as for the European Synchrotron Radiation Facility (ESRF) in Grenoble. For the ILC, several prototypes (BeamCal; Forward Calorimeter) developed at DESY Zeuthen are already in an advanced R&D status. Joint research has led to the development of advanced diamond materials and detectors for adjacent areas for which the most important are nuclear medicine (radiotherapy, radioisotopes production, radioprotection), energy management (inertial fusion, environmental and radioactive waste investigations), photovoltaic (solar cells), electrochemistry (diamond electrodes), biosensors on functionalized diamond surfaces (DNA sensing), and the development of high power, high voltage, high frequency electronic devices and diamond based MEMS and NEMS (i.e. micro- and nanoelectromechanical systems, respectively). Electronic devices have been commonly quoted in the past as an argument to push the engineering of electronic grade CVD-diamond; however, this high-technology field is still waiting for large-area single-crystal diamond wafers, which would give a base for economic, large scale production. ADAMAS is clearly adapted to this goal. We expect a significant impact of the HP3-WP15 on all of the projects described above. Dia-on-Ir material is preferable for large-area detector systems that have been projected to date with pcCVDD sensors lacking reasonable energy resolution. In radiotherapy, optimized Dia-on-Ir crystals may replace expensive natural diamond dosimeters lacking reproducible properties. The R&D on advanced diamond detectors triggers in addition the development of diamond broadband amplifiers and ASICs adapted to the characteristics of each of the novel materials appearing on the market. It is expected that the electronic subtasks proposed in ADAMAS will be ground-breaking for the signal processing of fast sensors and other RF applications in general. After completion, the technology will be transferred to European SMEs, which will produce and distribute the units. The last important impact is via the networking with our OII (Other Involved Institutions). The integration of new scientific groups (NINRE Sofia, RBI Zagreb, the University of Huelva, and the European XFEL GmbH) as well as European SMEs (DM, PTW) in the discussions of the ADAMAS consortium will strengthen synergy bringing rapid progress in this new and exciting interdisciplinary field. The scientific groups of ADAMAS expect professional technical support from the SMEs to the benefit of the ever expanding diamond detector user community.