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Electrical measurements of a multi-mode hybrid pixel detector ASIC for radiation detection
ECAP, Erlangen Centre for Astroparticle Physics, Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany.
Medipix Team, PH-ESE-ME, CERN, Geneva, Switzerland.
Medipix Team, PH-ESE-ME, CERN, Geneva, Switzerland.
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2012 (English)In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 7, no 1, p. Art. no. C01056-Article in journal (Refereed) Published
Abstract [en]

We present the first electrical measurements of an application-specific integrated circuit (ASIC) to be used in a hybrid pixel detector intended for dosimetry and radiation detection. The dosimeter has three programmable modes of operation: photon counting mode, energy integration mode, and dosimetry mode. The ASIC comprises a matrix of 16 by 16 (256 total) square pixels of 220 ÎŒm pitch, providing 12.4 mm 2 of segmented active area. Each pixel can be configured to operate in one of the three radiation measurement modes, with programmable-depth counters and shift registers to tailor the data word size and optimise the readout frame-rate in a given mode. The individual energies of impinging photons are determined through programmable analogue energy threshold discrimination, time over threshold measurement, or a combination thereof. Furthermore, the dosimetry mode contains 16 digital energy thresholds and automatically sorts data into 16 corresponding energy bin registers. The chip's output is therefore pre-processed charge spectra of the radiation field. This paper discusses results from measurements taken using programmable test-pulses to inject controlled stimuli into the pixel circuits.

Place, publisher, year, edition, pages
2012. Vol. 7, no 1, p. Art. no. C01056-
Keywords [en]
Data reduction methods; Front-end electronics for detector readout; Radiation calculations; Radiation monitoring
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:miun:diva-15829DOI: 10.1088/1748-0221/7/01/C01056ISI: 000303806200056Scopus ID: 84856860883OAI: oai:DiVA.org:miun-15829DiVA, id: diva2:488896
Available from: 2012-02-02 Created: 2012-02-02 Last updated: 2017-12-08Bibliographically approved
In thesis
1. A Hybrid Pixel Detector ASIC with Energy Binning for Real-Time, Spectroscopic Dose Measurements
Open this publication in new window or tab >>A Hybrid Pixel Detector ASIC with Energy Binning for Real-Time, Spectroscopic Dose Measurements
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Hybrid pixel detectors have been demonstrated to provide excellent quality detection of ionising photon radiation, particularly in X-ray imaging. Recently, there has been interest in developing a hybrid pixel detector specifically for photon dosimetry. This thesis is on the design, implementation, and preliminary characterisation of the Dosepix readout chip.

Dosepix has 256 square pixels of 220 mm side-length, constituting 12.4 mm2 of photo-sensitive area per detector. The combination of multiple pixels provides many parallel processors with limited input flux, resulting in a radiation dose monitor which can continuously record data and provide a real-time report on personal dose equivalent. Energy measurements are obtained by measuring the time over threshold of each photon and a state machine in the pixel sorts the detected photon event into appropriate energy bins. Each pixel contains 16 digital thresholds with 16 registers to store the associated energy bins. Preliminary measurements of Dosepix chips bump bonded to silicon sensors show very promising results. The pixel has a frontend noise of 120 e-. In low power mode, each chip consumes 15 mW, permitting its use in a portable, battery-powered system. Direct time over threshold output from the hybrid pixel detector assembly reveal distinctive photo-peaks correctly identifying the nature of incident photons, and verification measurements indicate that the pixel binning state machines accurately categorise charge spectra. Personal dose equivalent reconstruction using this data has a flat response for a large range of photon energies and personal dose equivalent rates.

Place, publisher, year, edition, pages
Mid Sweden University, 2012. p. 238
Series
Mid Sweden University doctoral thesis, ISSN 1652-893X ; 128
Keywords
Hybrid pixel detector, low power readout chip, photon counting, time over threshold (ToT), energy binning, active personal dosimeter (APD)
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:miun:diva-16171 (URN)978-91-87103-20-9 (ISBN)
Public defence
2012-05-30, O102, Mittuniversitetet, Campus Sundsvall, Sundsvall, 13:00 (English)
Opponent
Supervisors
Available from: 2012-06-07 Created: 2012-05-03 Last updated: 2012-08-01Bibliographically approved

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