background: in conventional radiation therapy, regarding normal tissue tolerance, the treatment of bulk tumors is one of the remaining challenges. grid radiation therapy (grt) is a technique to deliver high doses, approximately 15 – 20 gy per fraction, to several small volumes located in a large radiation field. this can be performed using a grid block. the current work has concentrated on the ...

We present a fully integrated InGaAs/InP negative feedback avalanche diode (NFAD) based free-running single-photon detector (SPD) designed for accurate lidar applications. A free-piston Stirling cooler is used to cool down the NFAD with a large temperature range, and an active hold-off circuit implemented in a field programmable gate array is applied to further suppress the afterpulsing contrib...

The application of small photon fields in modern radiotherapy requires the determination of total scatter factors Scp or field factors Ω(f(clin), f(msr))(Q(clin), Q(msr)) with high precision. Both quantities require the knowledge of the field-size-dependent and detector-dependent correction factor k(f(clin), f(msr))(Q(clin), Q(msr)). The aim of this study is the determination of the correction ...

We have measured the efficiencies and time responses of several largearea (200 and 80 mm2) beveled-edge avalanche photodiodes to x-rays of energy 6–20 keV in a photon counting mode. The diodes were used with avalanche gains of 102 to 103. Detector efficiency varied from ∼50% at 8 keV to ∼5% at 20 keV, while the time resolution was ∼1/2 ns with a tail out to longer times (∼5 ns). The duration of...

By harnessing the properties of photonic quantum states and their interaction with environment, imaging promises to go beyond limits classical imaging. However, inherent weakness detected signals fragility make difficult measure in practice. In recent years, emergence single-photon sensitive cameras enabled field take a step closer practical applications. this respect, singlephoton avalanche di...

We have developed calibration and data processing techniques optimized specifically for photon-integrating pixel array detectors (PADs). Primary effects to be calibrated are pixel gain variation and pixel area variation. Gain variations originate in pixel electronics and may be corrected for via a multiplicative factor. In contrast, area variations result from doping inhomogeneities in the sens...

Single-photon avalanche diode (SPAD) imagers typically have a relatively low fill factor, i.e. a low proportion of the pixel's surface is light sensitive, due to in-pixel circuitry. We present a microlens array fabricated on a 128×128 single-photon avalanche diode (SPAD) imager to enhance its sensitivity. The benefits and limitations of these light concentrators are studied for low light imagin...

A compact source of polarization-entangled photon pairs at a wavelength of 856 nm is realized using a frequency-doubled laser diode as the pump source for cavity-enhanced type-II spontaneous parametric down-conversion. Our setup generates photon pairs with entanglement visibility of >95% and with count rates comparable to those of standard experiments based on large-frame ion lasers. © 2001 Ame...