12,000

We have over 12,000 students, from over 100 countries, within one of the safest campuses in the UK

93%

93% of Lancaster students go into work or further study within six months of graduating

Home > Research > Publications & Outputs > Imaging spectroscopy with Ta/Al DROIDs: Perform...
View graph of relations

Text available via DOI:

« Back

Imaging spectroscopy with Ta/Al DROIDs: Performance for different Al trapping layer thicknesses

Research output: Contribution to journalJournal article

Published

Journal publication date04/2006
JournalNuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Journal number2
Volume559
Number of pages3
Pages689-691
Original languageEnglish

Abstract

To overcome the limited field of view, which can be achieved with single superconducting tunneling junction (STJ) arrays, distributed read-out imaging devices (DROIDs) are being developed. DROIDs consist of a superconducting absorber strip with proximized STJs on either end. The ratio of the two signals from the STJs provides information on the absorption position, and the sum signal is a measure for the energy of the absorbed photon. In our devices, the absorber is an epitaxial Ta strip that extends underneath the Ta/Al read-out STJs. Thus, the bottom electrode of the STJs is an integral part of the absorber. Due to the proximity effect, the STJs have a lower energy gap than the absorber, causing trapping of quasiparticles (QPs) in the STJs. The trapping will change with thicker Al layers because the energy gap of the devices will decrease. A series of 50×200 μm2 and 20×200 μm2 absorbers (including 50×50 μm2 STJs) and different Al trapping layer thicknesses, ranging from 65 to 130 nm, have been tested. The devices have been illuminated with 6 keV 55Fe photons. The position resolution is found to improve with increasing Al thickness. It is found that the current model needs to be adapted for DROIDs to account for different injection of QPs into the STJ and extra losses to the absorber.