Pulse Height Resolution Research Articles

Investigation of Cerium-Doped Barium Fluoride

BaF2 doped with cerium in the 2.7-4.5 mol percent range has been shown to have a peak scintillation emission at 365 nm with a decay constant of approximately 50 nano-seconds. The relative light output decreases with increasing cerium content; in this work it ranged from 0.5 to 0.3 with respect to pure BaF2 and from 1.2 to 0.7 relative to CsF. Pulse height resolution for the BaF2(Ce) samples ranged from 1.7 to 2.0 times that for pure BaF2. Timing measurements show that coincident resolving times for BaF2(Ce) lie between those of pure BaF2 and CsF and those of BGO. The scintillation efficiency was found to be independent of temperature from room temperature to 70°C and to fall off moderately at higher temperatures.

New Mesh PMTS for High Magnetic Environments

A new type of Photo-multiplier Tube (PMT) has been developed that can be utilized in the field of high energy physics, especially in strong magnetic environments. The fine mesh configuration of the dynodes provides the PMT with such unique features as an outstanding energy pulse height resolution, a high current amplification ratio and excellent time response characteristics, even in strong magnetic fields. The position of incident light can also be detected. This report sums up the various characteristics and the results of tests.

The imaging pin detector: A simple and effective new imaging device for soft X-rays and soft beta emissions

The development of a new bidimensional imaging detector system for soft X- and beta radiations is reported. Based on the detection of the differential induction signals on pickup electrodes placed around a point anode (or pin) in a gas avalanche detector, the system described has achieved a spatial resolution of better than 1 mm fwhm over a field of 30 mm diameter while preserving excellent pulse height resolution (20% fwhm for 5.9 keV X-rays). While limited to applications in which fairly low counting rates are encountered ( < 5 kHz) the present device offers considerable potential as a cheap and robust imaging system for applications in X-ray diffraction and autoradiography.

The pin detector — A simple, robust, cheap and effective nuclear radiation detector

The development of a series of radiation detectors based on the point anode is reported. Using readily available preformed pins from a variety of electrical connectors as the anodes, a family of devices has been created with useful properties as X-ray detectors, radiation monitors and internal beta counters. A wide variety of gas fillings can be used, argon/CH 4 premix being the most convenient. The stuctures are robust and call for no precision alignments so keeping costs down. Peformance of the devices in respect of sensitivity and pulse height resolution is comparable to that of conventional wire counters.

Characteristics of the Newly Developed MCP and Its Assembly

Several types of MCP assemblies including 2-stage and 3-stage MCPs consist of 8μm and 12μm channel MCP having length to diameter ratio α of 40 and 60 are tested relating to the gain and pulse height resolution. The 2-stage assembly with α=60 MCPs was incorporated in the proximity type MCP-PMT and showed capability to separate triple photon event clearly. Furthermore, 6μm channel MCPs in 2-stage was tested in PMT configuration and showed drastic improvement of timing property. As for the life, new MCP showed residual gain of more than 50% at the accumulated output charge of 0.1 C/cm2.

Discrimination capability of avalanche counters detecting different ionizing particles

The discrimination capability of avalanche counters to detect different ionizing particles has been studied using a 252Cf source. Pulse height, pulse-height resolution and timing properties have been measured as a function of the reduced applied voltage for parallel-plate and parallel-grid avalanche counters. At the highest applied voltages, space charge effects shift the pulse-height signal of the avalanche counter away from being linearly proportional to the stopping power of the detected particles and cause the pulse-height resolution to deteriorate. To optimize the avalanche counter capability, without loss of time resolution, it appears better to operate the detector at voltages well below the breakdown threshold. Measurements with 32S ions are also reported.

Recent Development of Photomultiplier Tubes for Nuclear and Medical Applications

New type of photomultiplier tubes (PMTs) have been developed for the applications to high energy physics experiments, medical instruments and biophysics experiments. Remarkable features of these PMTs are fast time response and gating function, immunity to the magnetic field, position sensitivity, good pulse height resolution and so on. The performances and the test results of these PMTs are discussed in this paper.

Developments of heavy-ion gas detectors at LNL

The most important developments in gaseous detectors at LNL are reviewed. Some aspects of timing, pulse height and position resolutions of avalanche counters are reported. The experimental work on heavy-ion identification by Bragg curve spectroscopy is summarized.

A parallel plate 10B neutron detector

Parallel plate ionization chambers with vacuum deposited 10B electrodes have been constructed and tested for 10B plating thicknesses from 24 μg/cm 2 to 61 μg/cm 2. Pulse-height resolutions of the alpha particle and of the 7Li fragment from the 10B(n, α) reaction were measured using low-energy neutrons. The pulse-height resolutions of the chambers were found to be better than a theoretical analysis had indicated.

Test of Lead Glass Shower Counters

Lead glass counters made of wedge shaped blocks of SF6 were tested with positrons at SLAC. The beam energy ranged from 2-17.5 GeV. Energy dependence and beam position dependence of pulse height and energy resolution were studied with lead glass blocks of various lengths. The effect of a BK-7 light guide on pulse height was clearly observed. Degradation of the energy resolution due to aluminum absorbers of various lengths was investigated. A mesh type photomultiplier was also tested.

A thin multiwire chamber operating in the high multiplication mode

The idea of a thin multiwire chamber with thick wires as a possible sampling detector for calorimeters was checked out in practice. Two small test detectors with gas sample thickness of 2 and 3 mm were constructed and tested in the laboratory. Avoiding argon, several pure hydrocarbons or binary mixtures with CO 2 were found to quench photons efficiently enough to make it possible to have charge multiplication factors of the order of 10 7. Efficiency of operation in this probably limited streamer mode for minimum ionizing electrons and with a single avalanche (streamer) response was found to be higher than 98%, with pulse-height resolutions down to 60% fwhm. The effect of gap-length variation is quite small; a gap change of upto 25% results in less than a 20% change in the mean charge released in a streamer.

HIGH RESOLUTION POSITRON EMISSION TOMOGRAPHY USING SMALL BISMUTH GERMANATE CRYSTALS AND INDIVIDUAL PHOTOSENSORS

We describe and compare six detector approaches for coupling small bismuth germanate crystals to individual photosensors. 1) Partial coupling of individual crystals to small cylindrical phototubes. 2) Full coupling of individual crystals to small cylindrical phototubes via shaped lightpipes. 3) Coupling of cylindrical phototubes to individual crystals using three sides of the crystals. 4) Full coupling of individual crystals to small rectangular photomultiplier tubes. 5) Full coupling of groups of crystals to multipleanode phototubes. 6) Full coupling of groups of crystals to larger rectangular phototubes with either sense wires, solid state photosensors, or UV sensitive wire chambers for crystal identification. From experimental measurements and Monte Carlo computer simulations we conclude that approaches 5 and 6 are superior in pulse height and timing resolution and are also the best way to read out crystals narrower than 3 mm.

Light attenuation effects in small NE213 scintillation counters

The observed differences in pulse height and energy resolution from scintillations in cylindrical NE213 counters of 5 cm diameter and 5 cm, 10 cm and 15 cm length are shown to be due to light attenuation effects within the scintillation chamber. A simple analytical relationship is derived to relate the amount of light collected by the photomultiplier to the position of the scintillation in the chamber. This is tested by taking Compton electron spectra from localized irradiation by a 137Cs gamma source. The amount of attenuation is sensitive to the coefficient of reflection of the chamber walls, with NE562 reflector paint giving better performance than NE561. An analytical fit to the light attenuation curve is incorporated in Monte Carlo simulations of detector response to neutrons and gamma rays, which are compared with proton and electron recoil spectra taken with the forementioned scintillation counters.

Light collection systems for thin film scintillation detectors

Three different designs for light guides used with thin film scintillators employed as ΔE detectors are described. Each system was tested in nearly identical conditions and configurations except for the light-gathering mechanism, using NE102A and Pilot B films and alpha-particles. Light-collection efficiencies, as well as energy and time resolutions are compared. It was found that a simple hollow cylindrical reflector in which the reflective surface was produced by vacuum evaporation of aluminium on a thin plastic sheet, was an efficient light guide for large-area thin-film scintillation detectors. Coupled to two matched and selected RCA 8850 phototubes operated in coincidence mode, this system was capable of giving a pulse height resolution of 21% and time resolution of 0.4 ns for a 1.1 mg/cm 2 NE102A detector and alpha-particles of 5.48 MeV incident energy. The TFD mounting feature of this design allows a comparison of different detectors without disturbing any other parameter. It thus provides a very effective system for testing and comparing the properties of thin scintillator films on a very reliable basis.

High Resolution Positron Emission Tomography Using Small Bismuth Germanate Crystals and Individual Photosensors

We describe and compare six detector approaches for coupling small bismuth germanate crystals to individual photosensors. 1) Partial coupling of individual crystals to small cylindrical phototubes. 2) Full coupling of individual crystals to small cylindrical phototubes via shaped lightpipes. 3) Coupling of cylindrical phototubes to individual crystals using three sides of the crystals. 4) Full coupling of individual crystals to small rectangular photomultiplier tubes. 5) Full coupling of groups of crystals to multipleanode phototubes. 6) Full coupling of groups of crystals to larger rectangular phototubes with either sense wires, solid state photosensors, or UV sensitive wire chambers for crystal identification. From experimental measurements and Monte Carlo computer simulations we conclude that approaches 5 and 6 are superior in pulse height and timing resolution and are also the best way to read out crystals narrower than 3 mm.

Performance of 1.5 m long counters made of a new acrylic scintillator

We have made a brief test on the performance of 1.5 m long counters made of a new acrylic scintillator block (ALTSUTIPE BLUE 155). For 1.2 GeV/ c protons, we observed a rather long light attenuation length (nearly 5 m) and good pulse height resolution (6.4% r.m.s.). With a 2″ photomultiplier at each end of the block, 0.23 ns time-of-flight resolution and 3 cm position resolution along the counter length were obtained. Although the light yield is about 1 2 compared to standard plastic scintillators, the acrylic scintillator is now an economical alternative in various applications for high energy physics.

A high pressure photomultiplier tube for deep underwater study

A photomultiplier tube having a bialkali photocathode of 2″ area has been developed for use as a photon detector for deep underwater studies. The tube can withstand up to 600 atmospheres (60 MPA) pressure and is sensitive to light from 300 to 550 nm wavelength. Electrical tests have been done under hydrostatic pressure, and no adverse affect were seen on either gain or pulse height resolution which are 8.5×10 5 and 6.3% fwhm for NaI(TI) 137Cs, equivalent respectively. This tube will be applicable for the detection of Cherenkov radiation produced by extremely high energy cosmic ray muon and neutrino interaction deep underwater.

2-D Position-Sensitive Scintillation Detector for Neutrons

A 2-di mensional neutron-position scintillation detector, based on the well-proven principle of the Anger γ-ray camera, has been developed. A 6Li-loaded, Ce-activated glass scintilator is coupled via a unique 44 mm thick light guide to a closely spaced hexagonal array of nineteen 5 cm diameter photomultipliers. The 1 mm thick x 22 cm diameter glass scintillator is made up of four optically cemented quadrants. The location of a scintillation is determined by calculating the X and Y centroids using a resistor weighting scheme. A spatial FWHM resolution of 2-3 mm was obtained. At 0.025 eV (1.8 A) the efficiency of the glass is 80% and the FWHM pulse height resolution is 14%. These characteristics in combination with low γ-ray sensitivity in the thin scintillator provide for excellent background rejection. Drift in the photomultipliers' gain results in output change of <0.05 mm/°C. The detector was evaluated in experiments at the pulsed spallation neutron source ZING-P'. In an experiment with a single crystal diffractometer a Laue pattern from a NaCl crystal was obtained. In a resonance radiography experiment Au and in, contained in a test object, were graphically resolved. For these applications the scintillation detector has several inherent advantages over a gas proportional counter.

Performance Studies of High Gain Photomultiplier Having Z-Configuration of Microchannel Plates

The characteristics of a high gain type ITT F4129 photomultiplier having three microchannel plates in cascade for electron multiplications have been investigated. These plates are in the Z-configuration. Measurements are given of the gain, dark current, cathode quantum efficiency, anode pulse linearity, electron transit time, single and multiphoton time spreads, fatigue, and pulse height resolution. The gain as a function of transverse magnetic field has been measured and is discussed. Photomultiplier characteristics as a function of the input pulse repetition frequency have also been investigated and discussed.

An Evaluation of Some New Phototubes with High Gain First Dynodes

We have examined high gain first dynode phototubes for use in a multicell gas Cherenkov counter at Fermilab. Price and availability dictated a careful examination of the EMI9839KB. Preliminary laboratory tests followed by test beam evaluation indicated that these tubes were adequate. We report here how the best of more than sixty of these tubes were selected based on their quantum efficiency, single electron resolution, gain and noise. Using the same test procedures we then evaluated small samples of Hamamatsu R1332, Amperex PM2262 and RCA 8850 tubes. We also report pulse height resolution and pulse shape data on the Hamamatsu R1262X phototube. We conclude that all four manufacturers now produce tubes with useful single photoelectron resolution and fast time response.