Technologies for the manufacture of materials and structures for X-ray and gamma-ray detection, using low-defect homogeneous crystals (Cd, Mn) Te with high resistance to defect generation from irradiation. Acronym: INNDEX

The INNDEX project is a response to the national strategic research and development programme 'Advanced Materials Technologies' - TECHMATSTRATEG.

The aim of the project is to obtain detector plates for X-ray and gamma-ray operation that are innovative in relation to those existing on the world market. For this purpose, crystals of (Cd, Mn) Te are being grown. This material is not commercially available on the market. In X-ray and gamma-ray detectors, the detector plate is the basic and most important detector element complemented by electronics for signal recording and processing. The material from which the plate is made determines the detector's detection performance. The most important shortcoming of commercially available crystals (Cd, Zn) Te is the tendency to form grains and close-ups during crystallisation, which prevents sufficiently large monocrystalline detector plates from being obtained. The monocrystallinity of the wafers is crucial for an efficient detector, as any grain boundaries or twinnings play the role of traps or recombination centres interfering with the transport of electrical charges (electrons and holes) generated by X-rays and gamma rays. Forty years of work by the world's laboratories, exploring different crystallisation technologies, have resulted in maximum plate sizes of 20×20×3-5 mm³ or exceptionally 25×25×2-3 mm³.

The work in the INNDEX project will be directed towards obtaining large detection plates with dimensions of 40×40×2-3 mm³, 50×50×2-3 mm³ even up to 60×60×2-3 mm³, covered with different types of electrical contacts.

The leader of the INNDEX project is a team from IFPAN headed by Professor Andrzej Mycielski, with extensive experience in growing (Cd, Mn) Te and developing suitable electrical contacts. The consortium includes a group from the NCBJ's TJ3 facility, with experience and research facilities in testing X-ray and gamma-ray detection systems, and a team from the WIM of the Warsaw University of Technology, which studies selected material properties, such as grain boundaries and twinnings, using Scanning Electron Microscopy. The final goal of the project is to commercialise and market the detector plates with (Cd, Mn) Te obtained at PUREMAT Technologies Sp. z o.o., a company cooperating with the Institute of Physics of the Polish Academy of Sciences in Warsaw.

The role of the NCBJ team within the INNDEX project is to characterise samples grown in the laboratory of IF PAN in order to determine the optimum operating parameters and measure the detector response to X- and gamma-rays, and then to design, build and test an electronic system for recording pulses from a strip detector based on the developed material (Cd, Mn) Te.

An example of the outcome of the research conducted at NCBJ:

Fig. 1 Energy spectra of alpha particles measured for sample 5259_8B_1

Figure 1 shows the energy spectra of alpha particles emitted by a radioactive source composed of the isotopes 241Am, 244Cm and 239Pu. The spectra were recorded for sample 5259_8B_1. Measurements were taken at -20^oC for different detector supply voltages. Peaks derived from the absorption of alpha particles emitted by the individual isotopes can be seen. An improvement in charge collection as a function of the applied voltage was observed (increase in signal amplitude for higher voltage values).

Figure 2 Energy spectrum of X-rays and gamma rays from a 57-Co source

Figure 2 shows the energy spectrum from the 57-Co source. X-ray lines with energies of 6 keV and 14 keV are visible, as well as slightly outlined gamma-ray lines with energies of 122 keV and 136 keV. The line on the right-hand side of the spectrum is a comparison pulse, coming from a pulser simulating the output signal from the detector.

Project leader at NCBJ: Dr Joanna Iwanowska-Hanke J.Iwanowska@ncbj.gov.pl

Project budget: PLN 12.42 million (including NCBJ budget: PLN 1.84 million)

Implementation start date: 2018.02.05

Consortium members:

Institute of Physics of the Polish Academy of Sciences (Project Leader)
National Centre for Nuclear Research
Warsaw University of Technology
Puremat Technologies Sp. z o. o.