Response of hybrid photodiodes with scintillators under realistic conditions (original) (raw)

Magnetic field effects on Hybrid PhotoDiode single electron response

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2000

Hybrid PhotoDiodes (HPDs) are very simple photo detectors which cover the applicability "eld of Photo Multipliers but show some better features. In particular HPDs show a very good photon counting capability, due to their peculiar one-stage gain process. It was found that HPD's photoelectron spectrum has a low-energy continuum which could be attributed to a backscattering process from the diode surface. In order to clearly distinguish the exact role of backscattering, the single photoelectron response (SER) of a 61 pixel proximity focused HPD was measured in standard conditions and in a 5 kG axial magnetic "eld. The results clearly indicate that the backscattering process gives the greatest contribution to the low-energy continuum spectrum. Monte Carlo simulations, using the EGS4 code, supported the analysis and allowed some interpretation of the e!ect, which greatly depends on diode surface characteristics, such as contact layer thickness.

The X-HPD—conceptual study of a large spherical hybrid photodetector

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2007

We present the results of a conceptual study demonstrating the feasibility of a large spherical hybrid photodetector with central anode. A prototype tube with 208 mm diameter and an anode in form of a metallic cube has been fabricated. In the final version of the so-called X-HPD concept the anode will be a scintillator cube with plated faces and a small photodetector to read out the bottom. The bialkali photocathode covers three quarters of the sphere surface. Combined use of this cathode in transmissive and reflective mode leads to effective quantum efficiency values exceeding those obtained in conventional hemispherical PMT designs. Further features of the concept are a photoelectron collection efficiency approaching 100% and a photon amplification in the scintillator crystal leading to a distinct single photoelectron signal. Using a custom built electron accelerator based on a CsI transmissive photocathode, LSO and YAP block crystals in geometries adapted to the anode of an X-HPD have been tested with single photoelectrons in the 10-30 keV energy range. The scintillation light was read out with a conventional PMT or a Si-PM. More than 30 photoelectrons per incident electron could be detected with the PMT.

Scintillation light read-out by thin photodiodes in silicon wells

Several applications of X-ray and gamma ray imaging detectors, e.g. in medical diagnostics, require millimeter or sub-millimeter spatial resolution and good energy resolution. In order to achieve such features we have proposed a new type of camera, which takes advantage of micromachining technology. It consists of an array of scintillator crystals encapsulated in silicon wells with photodiodes at the bottom. Several parameters of the photodiode need to be optimised: uniformity and e$ciency of the light detection, gain, electronic noise and breakdown voltage. In order to evaluate these parameters we have processed 3;3 arrays of 1.8 mm, &10 m thick photodiodes using (1 0 0) wafers etched in a KOH solution. Their optical response at 675 nm wavelength is comparable to that of a 500 m thick silicon PIN diode. Their low light detection e$ciency is compensated by internal ampli"cation. Several scintillator materials have been positioned in the wells on top of the thin photodiodes, i.e. a 200 m thick "lm of structured CsI(Tl), single crystals of CsI(Tl) and Lu S (Ce>). First experiments of -ray detection have been performed.

Performance of silicon PIN photodiodes at low temperatures and in high magnetic fields

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2009

The performance of a Si PIN diode (type Hamamatsu S3590-06) as an energy sensitive detector operating at cryogenic temperatures (∼10 K) and in magnetic fields up to 11 T was investigated, using a 207 Bi conversion electron source. It was found that the detector still performs well under these conditions, with small changes in the response function being observed in high magnetic fields, e.g. a 30% to 50% decrease in energy resolution. A GEANT4 Monte Carlo simulation showed that the observed effects are mainly due to the modified trajectories of the electrons due to the influence of the magnetic field, which changes the scattering conditions, rather then to intrinsic changes of the performance of the detector itself.

Linearity of P–N junction photodiodes under pulsed irradiation

Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2002

The dependence of the sensitivity on the radiation pulse length for a P–N junction photodiode has been investigated over an extended range of pulse lengths, from 170 ns to 1.2 ms. The power incident on the diode surface was varied between 1.6 and 118 mW.A novel method was used to generate the light pulses with variable length, while keeping the temporal pulse shape and the intensity constant. The method consists of using a rotating mirror in combination with a DC light source, in our case at 633 and 532 nm. In this way, the pulse shape only depends on the geometry of the setup, with the pulse length solely determined by the rotation frequency of the mirror. No further calibration is needed for determination of the pulse intensity and shape. Accuracies obtained are better than 2%, mainly determined by instabilities in the setup.The sensitivity of an IRD AXUV-100 photodiode was studied, both with and without a reverse bias voltage applied. At unbiased conditions and irradiation levels well below the saturation intensity, the photodiode had a constant, frequency-independent sensitivity over the full range of pulse lengths investigated. The sensitivity decreased at irradiation levels approaching saturation, with the largest decrease at longer pulse lengths. This decrease was fully accounted for by electron–hole recombination at a typical time scale of 15±5 μs.Under biased conditions and pulse lengths below 5 μs, the diode sensitivity remained constant for all incident power levels investigated. At longer pulse lengths a decrease in sensitivity was observed, both at low and high power. This second type of decrease is attributed to the frequency response of the bias electronics.An extrapolation of the results to other wavelength ranges is given, including the extreme ultraviolet (EUV) and soft X-ray ranges.

The response of a CsI(Tl) scintillator with photodiode readout to light particles and heavy ions

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1986

The response of a small (1 cm3) CsI(TI) crystal coupled to a silicon photodiode to light particles and heavy ions has been investigated using proton, alpha and oxygen beams in the energy range 10-25 MeV/n. Pulse-height resolution of 1 .2 and 2 .9% [fwhm] have been measured for 98 MeV°He and 278 MeV 160. The use of CsI(TI)-photodiode assembly m nuclear physics experiments with intermediate energy heavy-ions beams is envisaged

Review of the hybrid photo diode tube (HPD) an advanced light detector for physics

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 1995

The HPD is a nonmultiplicative light detector with typical gain of 1000 to 5000. Its development project, mainly supported by the CERN LAA project and by the INFN group V, was originally intended to find a replacement for the photo multiplier (PM) tubes for scintillating fibre calorimeter readout. After five years of development the HPD has become a versatile light detector, commercially available for everyday use, that can outperform PM tubes in photon counting efficiency and resolution, multi tesla magnetic field operation, uniformity of response, fast pulse dynamic range, and gain stability. The HPD has also a wide edge on PMs on pixelization potential and it is getting more and more competitive on timing properties. A review of the HPD performances and its latest advances are reported. * Corresponding author. Now at INFN sezione di Pisa, ' Worldlab Fellow, Geneva, Switzerland. ' Partially supported by INFN Eloisatron project. 0168-9002/9.5/$09.50 0 1995 Elsevier Science B.V. Ah rights reserved SSDI 0168-9002(95)00486-6

Photodetectors for scintillator proportionality measurement

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2009

We evaluate photodetectors for use in a Compton Coincidence apparatus designed for measuring scintillator proportionality. There are many requirements placed on the photodetector in these systems, including active area, linearity, and the ability to accurately measure low light levels (which implies high quantum efficiency and high signal-to-noise ratio). Through a combination of measurement and Monte Carlo simulation, we evaluate a number of potential photodetectors, especially photomultiplier Page 2 tubes and hybrid photodetectors. Of these, we find that the most promising devices available are photomultiplier tubes with high (~50%) quantum efficiency, although hybrid photodetectors with high quantum efficiency would be preferable.