1. Laser and alpha particle characterization of floating-base BJT detector.
Vladyslav Tyzhnevyia, Giovanni Batignanib, Luciano Bosisioc,Gian-Franco Dalla Bettaa,Giovanni Verzellesid, Nicola Zorzie
a Universita di Trento and INFN Trento, Trento, Italy , b Universita di Pisa and INFN Pisa, Pisa, Italy, c Universita di Trieste and INFN Trieste, Trieste, Italy, d Universita di Modena e Reggio Emilia and INFN Trento, Reggio Emilia, Italy, e Fondazione Bruno Kessler, Trento, Italy
Abstract – In this work we investigate the detection properties of existing prototypes of BJT detectors operated with floating base. We report about results of two functional tests. The charge-collection properties of BJT-detectors were evaluated by means of laser pulse. The results of functional test by a-particles emitted from radioactive Am-241 source are also presented here. Experimental results have shown that current gains of about 450 with response times in the order of 50 ms are preserved even in this non standard operation mode, in spite of a non optimized layout.
BJT detector - concept
BJT detector under test
Single BJT pixel
Emitter layout
BJT detectors are able to measure different types of ionizing radiation: a-particles (!), b-particles, X- and g-photons.
Matrix
20 um
32 um
BJT’s active area – 1.4x1.4 mm,
Emitter size– 32x32 mm
Base size – 200x60 mm
Substrate thickness – 600 mm,
Depletion voltage ~70 V
Functional test by laser
Detector with floating base is low power consuming! It turns on only when particle comes.
System with battery power supply can be implemented.
Light calibration
Detector – D400FC;
Amplifier – THS4303
Electrical characterization
Gummel plots (gain vs. current);
leakage current;
Bias voltage
10V
30V
50V
70V
Gain
130
140
Functional test by a-source Am241
Single DPIX pixel
Vb = 70 V
Gain ~450
Am241 - source of a-particles;
Ea = MeV;
Alpha surface emission rate in 2p steradian;
Matrix of DPIX pixels
Single DPIX pixel
Shows high gain of the detector even for 20 nAmp current;
Comparably low power consumption in idle state of BJT (0.5e-6 W at 10 V);
X I Pisa Meeting on Advanced Detectors May 25-29, 2009 La Biodola, Isola d'Elba (Italy)