-LNS SINPHOS SINGLE PHOTON SPECTROMETER FOR BIOMEDICAL APPLICATION Salvatore Tudisco 9th Topical Seminar on Innovative Particle and Radiation Detectors 23-26 May 2004 Siena, Italy
Delayed Luminescence In the last decades several experiments have clearly demonstrated that, once illuminated, all biological system emit for a quite long range (up to seconds) a very weak flux of photons, called DL Firstly observed from plant by Arnold and Strehler in 1950 10 3?10 5 times lower in intensity than the fluorescence Delayed luminescence is less popular than fluorescence: Delayed Luminescence is by nature extremely polyphasic; ; the lifetime spectrum extends from 10-7 to more than 10 s Delayed Luminescence is inherently a low-level level signal Arnold, Academic Press, New York (1986) p 29
Delayed Luminescence DL kinetics correspond to the hyperbolic trend I(t)? ( 1? m = Slope I 0 t/t 0 ) m ( ) yeast culture, ( ) Acetabularia acetabulum, ( ) soya seeds, ( ) pepper seeds, ( ) tomatoes 400 <? ill.< 450 nm.
Delayed Luminescence DL is a sensitive indicator of the biological state of the system DL can be a powerful tool for medical investigations, food and water quality control,, etc Acetabularia acetabulum and atrazine S = m/m 0 Biological detector for water pollution A. Scordino et al. J. Photo. Photobiol. B 32 (1996) 11
Biomedical Application of DL Recent experimental results: normal human fibroblasts human melanoma human fibroblasts at 32 C human melanoma at 32 C human fibroblasts at 10 C human melanoma a 10 C. DL time trend of human cells at several temperatures Total DL photons as a function of the cell density Detection system: Single photon counting Low background noise S.Tudisco et al. Rev. Sci. Inst. 74 (2003) 4485
Biomedical Application of DL 0,40 emission spectrum (a.u.) 0,35 0,30 0,25 0,20 0,15 0,10 0,05 human melanoma normal fibroblasts S.Tudisco et al. NIM A 518 (2004) 463 0,00 350 400 450 500 550 600 650 700 750 800 wavelenght (nm)
Partner: SINPHOS: SINgle gle PHOton Spectrometer Activity supported by INFN - V national committee ST- Microelectronics Applied Physics and Photonics Department of Bruxelles University (VUB) Input light signal Microprism Focusing lens 3 cm Array of SPAD sensors
DLP: Deep Lithography with Particles beam Particle beam irradiation Ion interactions modify the material properties Continuous irradiation Selective etching Precision cutting and drilling result in accurate microstructures with optical surfaces Point irradiation Selective swelling 2D spherical micro-lens arrays Solvent MMA vapor Spherical micro-lenses 2D fiber holders optical fibers precision conical micro-holes alignment pins The fabrication process consists of three basic procedure: ion irradiation of a PMMA substrate followed by a development of the irradiated regions with a selective solvent or by volume expansion of the bombarded zones caused by a diffusion of an organic monomer vapor. L.Cosentino et al., NIM B 209(2003)340.
DLP: Preliminary Results input fiber micro-lens micro-prism wavelength spread micro-photosensors
DLP: Preliminary Results
SPAD - Single Photon Avalanche Detector - Microelectronics Developed by ST Microelectronics Compact (10-100?m) and reliable 100 ps timing High quantum efficiency Can be built in form of arrays Can be coupled to micro-optical devices built by means of DLP E.Sciacca et al, IEEE Trans. on Ele. vol. 50 (2003) 918
SPAD p-n n junction remaining quiescent above breakdown voltage until a photon is absorbed in the depletion volume The event is detected through an avalanche current pulse Low operating voltage 30 Volts Average gain for each photocarrier is about 10 6 Dark counting rates at room temperature: 10c/s for 10µm m device and 1kc/s for 50 µm E.Sciacca et al, IEEE Trans. on Ele. vol. 50 (2003) 918
SPAD: Readout Passive quenching circuit Active quenching circuit In the passive mode the spad is reversed biased trough a resistor of 100 k ohm or more. One can obtain an output pulse from a PQC, by inserting a low value resistor Rs in series on the ground of the circuit. When the avalanche is generated it discharges the junction capacitance and the diode voltage fall down exponentially restoring the quiescent state In the active mode a circuit senses the rise of avalanche pulse and react back on the spad forcing with e controlled bias source the quenching and the reset transitions in short times S.Cova et al, Appl. Optics vol. 35 (1996) 1956
Time Correlated Single Photon Counting measurement Optical pulses: 820 nm FWHM 20 ps 10 khz repetition rate 10 µm diameter Photons absorbed in the depletion region Minority carriers photogenereted in the neutral p region that reach the junction by duffusion FWHM= 70 ps E.Sciacca et al, IEEE Trans. on Ele. vol. 50 (2003) 918
Scintillator readout with SPAD Optical pulses: 700 nm FWHM 2 ns 30 Hz repetition rate SPAD PMT FWHM? 3 ns BC408 scintillator Laser light
Scintillator readout with SPAD BC408: 420 nm mean life 2.1 ns FWHM? 2.4 ns Counts SPAD PMT?or? source PMT BC408 scintillators Time [ns]
Summary DLP first results confirms the possibility to use such a technique to develop an optical custom device for the SINPHOS spectrometer. SPAD - the measurement performed by using e passive quenching read-out have confirmed the results obtained with an active read-out system. Time resolution as expected is a little worst but fully sufficient for biomedical application purpose. Linear array starting from the concrete possibility to use passive quenching, a read-out system for a whole linear array has been studied and should be tested soon.
Collaboration INFN-LNS Catania University S. Tudisco G. Cosentino P.Finocchiaro F. Musumeci A.Scordino G. Privitera S. Privitera