XP2020 Photomultiplier Research Articles

Temperature dependences of LaBr 3(Ce), LaCl 3(Ce) and NaI(Tl) scintillators

The temperature dependence of light output, energy resolution and decay time constants of the light pulses of NaI(Tl), LaCl 3(Ce) (LaCl 3) and LaBr 3(Ce) (LaBr 3) crystals were measured over the temperature range of −30 to 60 °C. In the study of the light output, the number of photoelectrons produced by the scintillators in the XP2020 photomultiplier was measured and corrected for by the temperature dependence of the quantum efficiency determined for 360 and 420 nm, respectively. It showed a high stability of the light output of LaBr 3 of about 0.01%/°C and a comparable uniformity of LaCl 3 at a long peaking time of 12 μs. The well-known thermal instability of NaI(Tl) was confirmed at a short peaking time of 2 μs. However, a much better stability of NaI(Tl) at low temperatures was observed for a long peaking time. The study of the decay of light pulses from LaCl 3 and LaBr 3 crystals confirmed earlier measurements, while NaI(Tl) showed a complex behavior at different temperatures. At low temperatures a strong contribution of a slow component of up to 60% of the total light was observed, while at elevated temperatures a well-known initial slow decay was replaced by a delayed maximum and the slow component became insignificant. The results of the study of energy resolution seem to be correlated with the variation of both the light output and a dependence of the decay time constants of the light pulses at changing temperature. This is particularly interesting in the case of NaI(Tl), where different dependencies of the energy resolution as a function of temperature for different peaking times in the spectroscopy amplifier were found. Tests of the XP2020 PMT itself showed that the thermal instability of the gain of the dynode structure of about−0.4%/°C is a dominating effect. The opposite effect on an increasing quantum efficiency, partly compensating for the gain instability, was observed above 10 °C for the longer wavelength of 420 nm.

Detection of Light Pulses Using an Avalanche-Photodiode Array with a Metal-Resistor-Semiconductor Structure

The results from tests of avalanche-photodiode (APD) arrays with a metal-resistor-semiconductor (MRS) structure are presented. The photodiodes, having a working area of 1 × 1 mm2, operated in the Geiger mode. MRS APD arrays were tested using light-emitting diodes and as components of scintillation counters with dimensions of the plastic of 50 × 50 × 5 mm, in which light was collected with the help of a wavelength-shifting fiber. Tests of scintillation counters on particle beams of minimum ionizing particles have confirmed the high efficiency (∼13 photoelectrons) of the MRS APD. Their basic characteristics are compared to those of an XP2020 photomultiplier.

Ion Feedback Afterpulses in ФЭУ-130 and XP2020 Photomultipliers

Intensities and time distribution spectra of ion feedback afterpulses were studied as a function of the potential differences between the photocathode and first dynodes in ФЭУ-130 photomultipliers with the aim of using this type of photomultiplier in autocorrelation delayed-coincidence spectrometers. The intensities and amplitudes of the afterpulses in an ФЭУ-130 are found to be substantially larger than those in XP2020 photomultipliers, which are usually used in delayed-coincidence spectrometers.

Characteristics of the TOF counters for GlueX experiment

Timing characteristics of two time-of-flight scintillation counters were studied using particle beams at the IHEP (Protvino) accelerator. The bars were 2m long and had a cross-section of 2.5×6.0cm2. Each bar was viewed from both ends by XP2020 photomultipliers. A time resolution better than 40ps was achieved.

An Effect of Interelectrode Potentials on an Afterpulse Formation in a Photomultiplier Tube

An effect of the interelectrode potential difference on the intensity of the afterpulse formation in a XP2020 photomultiplier tube is studied; the afterpulses are caused by an ion feedback. It is shown that the photocathode–accelerating-electrode gap plays a decisive role in the process, while the dynode system is of minor importance at pulse currents below a few dozens of milliamperes.

Absolute light output of scintillators

The absolute light outputs of BGO, CsI(Tl) and some new Ce-doped crystals have been measured to an accuracy of about /spl plusmn/5% using calibrated XP2020Q photomultipliers and standard S3590.03 and S2740.03 photodiodes. The use of small crystals, 9 mm in diameter and 1 mm thick, reduces the corrections for imperfections in the light collection process and in the photoelectron collection by the photomultipliers. The measured light-output of 8500/spl plusmn/350 ph/MeV (photons/MeV) for the BGO crystals agree well with the earlier measurement done by Holl et al. (1988). The carried out study highlighted the importances of the spread in the published emission spectra of the crystals which seems to limit measurement accuracy. Finally, a simple comparative method of measuring light output to an accuracy of /spl plusmn/10%, is proposed using an uncalibrated XP2020 photomultiplier and a 1 mm thick BGO crystal as a standard.

Comparison of the timing properties of the new Philips components (Amperex) XP2020/UR photomultiplier and the XP2020 photomultiplier

Timing characteristics are measured for the Philips Components (Amperex) XP2020/UR photomultiplier. The transit time jitter is significantly better than that of previously available XP2020 tubes. In a study of the transit time jitter, a single photoelectron resolution of 286+or-3 ps was obtained for the XP2020 and 190+or-2 ps for the XP2020/UR. >

Properties of BaF 2 scintillator working with p-terphenyl wavelength shifter

Properties of a 4 cm diameter × 0.5 cm BaF 2 crystal coated with a 2 mg/cm 2 thick layer of p-terphenyl wavelength shifter were studied in comparison to a pure BaF 2 scintillator of the same dimensions. The light yield (expressed in the number of photoelectrons), the energy and time resolutions and the light pulse shape were determined for crystals coupled to the XP2020Q and XP2020 photomultipliers. This study shows an efficient shifting of the UV light by p-terphenyl, confirmed by the light yield comparable to that of the pure BaF 2 crystal, as well as a slightly better energy resolution. However, the time resolution measured for 60Co γ-rays, ( E γ > 1 MeV), was degraded by a factor of 2, from 108 to 224 ps. This is associated with the slowing down of the light pulse caused by the energy transfer process from the BaF 2 emission to that of p-terphenyl. A light pulse with decay time constant equal to 2.5 ns and FWHM equal to 3.7 ns confirms the above conclusion.

Timing study with R 1294 U microchannel plate photomultipliers

Timing properties of scintillation counters consisting of NE 111 plastic scintillators 15 mm in diameter and 10 mm thick coupled to R 1294 U MCP photomultiplier were studied. Special attention was directed towards: time jitter measurement of the R 1294 photomultiplier, determination of photoelectron yield of this photomultiplier for NE 111 scintillator and finally time resolution study with 60Co and 22Na sources in comparison to that performed with classical XP2020 photomultiplier. Time resolution for γ-rays from 60Co source measured with the R 1294 U photomultiplier and NE 111 scintillator equal to 105 ps is still inferior compared to that observed with the XP2020 photomultiplier because of much lower photoelectron yield. For the same number of photoelectrons, however, it becomes better by a factor 1.7. It shows that microchannel plate photomultipliers with improved photocathode would be very attractive in timing with fast scintillators of small volume.

Properties of CsF, a fast inorganic scintillator in energy and time spectroscopy

Energy resolution, linearity of the response versus energy of γ-rays, peak-to-total ratio, photoelectron yield, light pulse shape and time resolution for different ranges of energy lost by γ-rays in CsF scintillators were determined for several samples coupled to XP2020 photomultipliers. A time resolution equal to 230 ps for 60Co was measured. It is therefore comparable to that of plastic scintillators. A light pulse with rise and decay time equal to 0.35 ns respectively was observed for a 6 mm thick clear sample of CsF crystal. The 25% energy resolution for 662 keV γ-rays from a 137Cs source and a light yield equivalent to about 500 photoelectrons per 1 MeV were determined. The investigations show that CsF crystals seem to be powerful scintillators for several applications.

Influence of incident light wavelength on time jitter of fast photomultipliers

The study of the single photoelectron time resolution as a function of the wavelength of the incident light was performed for a 56 CVP photomultiplier having an S-1 photocathode. The light flash from the XP22 light emitting diode generator was passed through passband filters and illuminated the 5 mm diameter central part of the photocathode. A significant increase of the time resolution above 30% was observed when the wavelength of the incident light was changed from 790 nm to 580 nm. This gives experimental evidence that the time jitter resulting from the spread of the initial velocity of photoelectrons is proportional to the square root of the maximal initial energy of photoelectrons. Based on this conclusion the measured time jitter of C31024, RCA8850 and XP2020 photomultipliers with the use of the XP22 light emitting diode at 560 nm light wavelength was recalculated to estimate the time jitter at 400 nm near the maximum of the photocathode sensitivity. It shows an almost twice larger time spread at 400 nm for the C31024 and RCA8850 with a high gain first dynode and an about 1.5 times larger time spread for the XP2020 photomultiplier, than those measured at 560 nm.