We have been selling radiation detectors since 1975 and in that time have built up an industry leading portfolio of products and product knowledge.

Our comprehensive range of scintillation detectors covers applications ranging from industrial (thickness gauging in the steel industry, plutonium assay for safe-guards) to medical (blood flow monitors) & research (pulsed shaped discrimination for neutron / gamma detection, anti-neutrino detection arrays).

 


Types of scintillation detectors we sell:

  • Liquid Scintillators
  • Plastic Organic Detectors
  • Novel Detector Materials
  • Standard Scintillation Crystals
  • Integrated or demountable electronics
  • Various Window Options
  • Analytical Electronics & Software

Common detector uses:

  • Thickness Gauging
  • Plutonium Assay
  • Nuclear Medicine
  • Anti-Neutrio detection
  • Portal Monitors
  • Oil Exploration

Materials Table

Click on a material link below for more information.

Materials Properties Applications
Nal(TI) Very high light output, good energy resolution General scintillation counting, Medical, Security, Industrial, Environmental monitoring, Oil & gas - core logging, Nuclear physics
CeBr3 Very high light output, very good energy resolution, low background High-resolution spectroscopy, low background applications
CLYC Good absorber with good stopping powers - density 3.31 g/cm³ and an Effective Z of 54. Fast with a decay time of 1ns Emitting with a 370nm peak. Widespread IR application as spectroscopic windows, prisms and lenses. Security, Medical physics, Eximer laser windows, High energy Physics, Space
Csl(Na) High light output, High density, High γ-ray stopping power Suitable for standard PMT readout, Good for harsh environment applications Environmental, Geophysical, Oil & Gas, General, Space research, Rugged environmental
Csl(TI) Non-hygroscopic, rugged Particle and high energy physics, general radiation detection, photo diode readout, phoswiches
LaCl3 Good energy resolution, Fast emission, Excellent linearity response, High count rate capabilities, High Light Output Medical SPECT, Security, Oil & Gas Exploration - core logging, Industrial, Physics
6LiI(Eu) High neutron cross-section, high light output, rugged Thermal neutron detection and spectroscopy, Oil & Gas, neutron/gamma discrimination

Scintillator Reference Material

The table below presents an overview of the most commonly used scintillation materials with some of their specific applications.

The choice of the best scintillation crystal to use in your radiation detector depends strongly on the application. Important questions to ask to determine the optimum choice are:

  • What is the energy of the radiation to measure?
  • What is the expected count rate?
  • What are the experimental conditions (temperature, shock)?
Material Density (g/cm3) Emission Maximum (nm) Decay Constant (1) Refractive Index (2) Conversion Efficiency (3) Hygroscopic
Nal(TI) 3.67 415 0,23 us 1.85 100 Yes
Csl(TI) 4.51 550 0,6/3.4 us 1.79 45 No
Csl(Na) 4.51 420 0.63 us 1.84 85 Slightly
Csl(Undoped) 4.51 315 16 ns 1.95 4-6 No
CeBr3 5.23 380 18-20 ns 1.9 130 Yes
CaF2(Eu) 3.18 435 0.84 us 1.47 50 No
LaCI3:Ce(0.9) 3.79 350 70 ns 1.9 95-100 Yes
6Li-glass 2.6 390/430 60 ns 1.56 4-6 No
6Li(Eu) 4.08 470 1.4 us 1.96 35 Yes
BaF2 4.88 315 220 0.63 |as/ 0.8 ns 150 1.54 16 5 No
YAP(Ce) 5.55 350 27 ns 1.94 35-40 No
LYSO:Ce 7.2 420 50 ns 1.82 70-80 No
BGO 7.13 480 0.3 |as 2.15 15-20 No
CdW04 7.9 470/540 20/5 us 2.3 25-30 No
PbW04 8.28 420 7 ns 2.16 0.2 No
Plastics 1.03 375-600 ns range 1.023 25-30 No

The table below presents an overview of the most commonly used scintillation materials with some of their specific applications.

When we observe the “Scintillator Properties” table carefully, it is clear that none of presently known scintillation crystals possesses all the ideal characteristics such as high density, fast decay etc. The choice of a certain scintillation crystal in a radiation detector depends strongly on the application. Important questions to ask to determine the optimum choice are:

  • What is the energy of the radiation to measure?
  • What is the expected count rate?
  • What are the experimental conditions (temperature, shock)?

Scintillation detectors usually employ a Voltage Divider (VD) network to operate the PMT. This sometimes called “bleeder network” defines a potential (voltage) difference between the cathode, dynodes and anode of the PMT. The exact design of this network is of influence for proper working of the scintillation detector. Some details of voltage divider networks are discussed below. The descriptions below are not exhaustive; for more details we refer to the photomultiplier manufacturer’s literature.

Positive or Negative High Voltage?

It is possible to operate a photomultiplier tube in two ways:

  • A. anode at positive potential (cathode at ground)
  • B. anode at ground (cathode at negative potential)

For measurements of DC anode current such as in some X-ray applications, option B is the only choice since in the first option the anode must be separated from the follow-up electronics by means of a high voltage capacitor.

On the other hand, option A is used for most standard applications since the m -metal shield should be preferably at cathode potential. Option A implies that cathode, detector mass (ground) and shield are all connected together. In option B, the shield must be very well insulated from the detector mass and special construction requirements apply.

Negative high voltage is required for some fast timing applications where the possibility of discharges between the cathode of the PMT and the m -shield are to be avoided. These PMTs are operated at more than 2 kV for fast response.

Voltage dividers for detectors operated at positive high voltage can be wired with a single connector for signal and HV. At the electronic side, these can be separated using a simple splitter, as illustrated in fig. 8.2

The design of the voltage divider influences the performance of a detector. At high count rates, the voltage across dynodes may drop and the average bleeder current should always be defined as at least 10 times larger than the average anode current in the detector. A standard resistor value between dynodes is 470kW. This is a compromise between bleeder current and gain stability which is sufficient for count rates up to approximately 50.000 c/s.

Voltage dividers may be linear (most common), tapered or specially stabilized with Zener dynodes or transistors.

The number of possibilities is large. A very important aspect is the potential (electric field) between the cathode and the first dynode of the PMT. In any case, this potential should be sufficient to ensure a good photoelectron collection efficiency. Usually, this voltage is prescribed by the PMT manufacturer.

The gain of a scintillation detector varies with each PMT and is also strongly influenced by the exact design of the voltage divider. If the absolute detector gain is of Importance, it can be defined as: the output voltage (in e.g. 1MW ) at a specific operating voltage of the PMT for a certain energy absorbed in the detector.

PMTs can be selected on gain but adjustment of the gain of the detector by varying the voltage in the VD by means of a precision potentiometer is much more convenient. Extra options on voltage dividers are e.g. a gain potentiometer, an extra dynode output or a focus potentiometer.

SCIONIX can design the voltage divider best suited for your application without any additional cost.

Plug-on or Integrated?

Voltage Dividers and other electronics can be incorporated into the scintillation detector. In this case, the resistor network is directly soldered onto the pins of the PMT which implies a minimal length of the assembly. For low background applications this is the preferable option.

The connector(s) for high voltage and signal are located at the back of the assembly. Also, flying leads are an option. When it is expected that detectors have to be interchanged often it may be preferable to use a so-called “plug-on” option in which case the voltage divider and associated electronics are mounted in a small housing with the same diameter as the detector which is plugged on the pins of the base of the PMT. Most frequently used PMT bases in this respect are the 12 pin JEDEC B12-43 base for 38 mm diameter PMTs and the 14 pin JEDEC B14-38 base for 51, 76 and 127 mm diameter PMTs. These are also the standard bases for scintillation detectors supplied without voltage divider. Below some examples are presented.

Voltage Dividers and Preamplifiers

A PMT signal will be attenuated in a long cable and when signals have to be transported over more than say 10 m of cable this effect cannot be neglected. Signals even may become deformed and signal differences between a set of detectors having different cable lengths can be a problem.

Furthermore, the signal that is to be fed into a main amplifier (also called shaping amplifier or spectroscopic amplifier) needs to have a certain pulse fall time (typically 50 m s) in order to allow proper pole-zero and base-line correction. This effect is especially important at high count rates.

To solve the above problems, scintillation detectors can be supplied with a built-in (or plug-on) voltage divider/ preamplifier. This amplifier has an output impedance of 50 W for proper matching to the most frequently used cable impedance (reflections). Usually, the end stage of this amplifier is based on the principle of an emitter follower.

The standard SCIONIX voltage divider/ preamplifier the VD (12) 14 / E2 is an example of this suited for a wide variety of PMTs. This amplifier operates with a wide variety of voltages, is very fast (rise time < 50 ns) and can drive cable lengths of 100 m or more. Varieties for ultra low power consumption exist. The amplifier is very small so that it will fit in almost every scintillation detector. Please consult JCS for your specific requirements regarding signal shape, power consumption etc.

Connectors

Often, high voltage, signal and preamplifier power are fed in via separate connectors. The SCIONIX standard connector for high voltage is the SHV(Super High Voltage) connector, the most frequently used standard in nuclear electronics. For signals, BNC connectors are the standard and for preamplifier power signals, the dual LEMO type 0 and the 9 pin sub-D connector are normally used.

Other possibilities are e.g. flying leads options, water tight connectors, MHV, TNC, PET-100 and different types of LEMO or FISHER connectors.

Power HV and signal can also be fed in (out) via a single large multipole connector

Built-in High Voltage Generators and Other Electronics

Recent developments in hybrid circuitry have allowed to incorporate a number of other electronic components into the scintillation detector assembly which eliminates in some applications the necessity of NIM based electronics.

An example of the above is the scintillation detector with a built-in High /oltage Generator( – HV option, see section 6). This is a small Cockroft – Walton generator which produces the high voltage required to operate a PMT. This unit only requires a DC voltage of + 5 V or + 12 V and uses only 100 mW of power. The unit is fully integrated with the PMT so there are no high voltage leads anywhere in the assembly. The gain of the PMT is maintained even at high anode currents (up to 100 m A) and the unit adds only 50 mm to the length of the PMT. The high voltage can be factory set, precision potentiometer adjustable or set by a 0 – 1 V regulating voltage. Below the advantages are summarized.

Advantages built-in high voltage generators:

  • Compact
  • Low power consumption
  • Sealed
  • High gain stability versus count rate

Besides the above mentioned preamplifiers it is also possible to incorporate e.g. shaping amplifiers (spectroscopic amplifiers) or Single Channel Analyzers (SCAs) into a detector assembly. All these components, constructed as small SMD or hybrid circuits, are very small in dimension. Specific parameters of these devices can be defined by the user since the standard models can be easily adapted. Please consult JCS for more details.

fig. 8.1

fig. 8.2

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