x and gamma ray photoconversion

X-ray photocurrent


The study of the X-ray photo-conversion processes is fundamental for the characterization of innovative materials to be employed as ionizing radiation detectors.  We have two different apparatus for X-ray photocurrent experiments. One equipped with a lead-screened X-ray radiation source, a Mo target X-ray tube, with peak energy at 17.5 keV and maximum photon energy up to 35keV (same energy used in mammography). The calibrated dose rates span from 1 mGy/s to 60 mGy/s. Thus, strong exposures for radiation hardness validation can be performed. The second setup uses as radiation source a very compact W target X-ray tube. With this source we are able to tune the accelerating voltage thus the maximum energy of the photons in a range between 40 up to 150keV. A precise control of the dose rate is also possible. With this system the dose range is between few mGy/s down to fraction of μG/s without any filters. This allow us to measure the Limit of Detection (LoD) of the devices under test. To evaluate the dynamic response of new detectors, in both the setup, the X-ray beam is switched on/off by an automated mechanical shutter (low frequency, up to 1Hz) or a programmable lead-covered chopper (higher frequency, up to 400Hz). Electrical characterizations are performed in real-time during the X-ray exposure on photoresistors, photodiodes or phototransistors. The measurements can be performed in controlled atmosphere (air, nitrogen, argon or oxygen) and at controlled temperature. The two system are also equipped with three micromanipulators for fast electrical contacts of microelectronic devices.

Beta and Gamma Spectroscopy


We have access to a list of radioactive portable sources, supplied by the Department of Physics and Astronomy.

241Am (main emission α@5486keV)

226Ra (main emission α@4871keV)

137Cs (main emission γ@662keV and β-@512keV)

60Co (main emission γ@1173keV, 1332keV)

90Sr (main emission β-@546keV)

207Bi (main emission β+@2398keV)

We can investigate the effects of irradiation on the electrical characteristic of organic and inorganic materials (e.g. induced photocurrent and/or voltages, resistance and capacitance variation).  Dedicated amplification chain for charge counting and spectroscopy is currently under construction. Manage to acquire a single pulse of charges generated inside our material under study is of extreme importance. In this way is possible to study the interaction of a single particle with the material itself and how this charges are then transported across the material.