Characteristic measurements of a hybrid pixel detector

Abstract

Tässä tutkielmassa otan käyttöön ja karakterisoin fysiikan laitokselle hankitun ener- giasensitiivisen röntgenkameran Advacam WidePix L 1x10. Hankinnan tarkoituksena on mahdollistaa energiasensitiivinen kuvantaminen. Kameran karakterisoitavaksi om- inaisuuksiksi valitsin energiaresoluution, paikkaresoluution, kynnysten kohinareunan ja fotonien laskentanopeuden. Mittausten tulokset ovat lähellä valmistajan ilmoit- tamia arvoja, sekä aiemmin tehtyjä mittauksia Medipix 3RX -siruista. Kamerasta löytyi ongelma, sillä energiaresoluution määrityksessä huomasin pikseleiden välillä olevan huomattavia eroja amerikium-241 radioisotoopin 59.5409keV röntgenpiikin energiassa.

In this thesis, I commissioned and characterized a photon counting x-ray camera for the complex materials research group. The camera Advacam WidePix L 1x10 is a new device for the group and for the Physics Department of University of Jyväskylä. The intention for acquiring the new camera was to enable energy sensitive tomography. I chose energy resolution, spatial resolution, photon counting speed and the noise edge of the energy thresholds as characteristics to be measured and determined from the camera. The measured values agrees with the measurements done on the Medipix 3RX chip which is the base of the acquired camera. The measurements also agrees with the specificiations given by the manufacturer. However, I found out that the energy resolution varies from pixel to pixel. This discrepancy was when measuring the characteristic 59.5409keV X-ray peak of Americium-241. The ultimate reason for this discrepancy wasn’t found but it is likely due to imperfect pixel-wise energy calibration of the camera.