CZT500S spec - BIC Technology

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LARGE VOLUME HEMISPHERICAL
NUCLEAR RADIATION DETECTOR
CZT/500(S)
Ganibu Dambis 26, P.O.Box 33
Riga, LV-1005, LATVIA
Tel. (+371)6738-3947
Fax:(+371)6738-2620
[email protected]
www.bsi.lv
CONTENTS
INTRODUCTION .......................................................................................................... 2
SPECIFICATION .......................................................................................................... 3
DESIGN FEATURES OF CZT/500(S) .......................................................................... 4
SAFETY AND PRECAUTION....................................................................................... 5
THEORY OF THE HEMISPHERICAL DETECTOR OPERATION................................ 5
DELIVERY SET PRICE .................................................Error! Bookmark not defined.
OTHER CONDITIONS.................................................................................................. 9
ILLUSTRATION
Fig. 1 - CZT/500.
Fig. 2 - Spectrum of Cs137 measured with CZT/500.
Fig. 3 - Design features of CZT/500(S).
Fig. 4 - Cross sectional view of a hemispherical detector showing the drift of electrons
toward a positive “point“ electrode and the resulting induced charge pulse. The
majority of the induced pulse arises from electrons originating in the cross-hatched
region of the hemisphere.
Fig. 5 - Appearance of a quasi-hemispherical detector.
Head Management:
Dr. Gostilo Vladimir
Dr. Sokolov Alexander
Mr. Moshak Vladimir
Bank details:
NORDEA Bank Finland Plc Latvian branch
Bank code: NDEALV2X
IBAN account: LV13NDEA0000080226011
Commercial registration number: 40003176361
VAT Registration No. LV40003176361
Place of registration: Riga, Latvia
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INTRODUCTION
The CZT/500(S) is a nuclear radiation detector based on CADMIUM ZINC
TELLURIDE -CdZnTe, a large bandgap semiconductor material having a high atomic
number and high density, which makes these detectors one of the most sensitive
small sized and room temperature detectors in operation.
The CZT/500(S) is a spectrometric detector intended for gamma radiation registration
in a range of an energy registered more then 60 keV.
Availability of the letter “S” in the detector's name means Super Grade (detector with
high spectroscopy performance) detector CZT/500S.
Outward appearance of the CZT/500 is shown in fig.1.
Fig. 1 - CZT/500.
Typical spectrum of Cs137 measured with CZT/500 is shown in fig. 2.
Fig. 2 - Spectrum of Cs137 measured with CZT/500.
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SPECIFICATION
Basic
Parameter
detector type
detector geometry
detector sensitive volume
Value
CdZnTe
quasi - hemispherical
500 mm3
Performance (at operation temperature +22 °C)
Parameter
energy resolution (FWHM) at 662 keV line
 for CZT/500
 for CZT/500S
peak-to-Compton ratio at 662 keV line
 for CZT/500
 for CZT/500S
Value
< 30 keV
< 18 keV
> 2.3
> 4.0
Bias voltage requirements
Parameter
detector high voltage polarity
Value
positive
Dimensions
Parameter
diameter
length (without connector)
distance between a top plane of the housing
cover and sensitive surface of the detector
Value
23 mm
33 mm
7 mm
Connector BNC type
Typical cable lengths: 0.2 m (available from 0.1 to 30 m)
Typical connectors: single 5-pin LEMO or 9-pin D type, BNC and SHV.
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DESIGN FEATURES OF CZT/500(S)
The CZT/500(S) design features are shown in fig. 3.
The detectors consist of a CdZnTe detector, watertight housing and connector.
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Fig. 3 - Design features of CZT/500(S).
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SAFETY AND PRECAUTION
Equipment Precautions:
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The CZT/500(S) must be connected to the POSITIVE high voltage supply.
The detector housing is fragile and should not be strongly squeezed.
When possible, use radiation shield and (or) collimator or maintain the
detectors a distance from strong neutron-gamma sources for prevention of
detector and connector’s insulator radiating damages.
Decontamination or cleaning of detectors can is carried out with water or other
non-corrosive liquids.
Radiation Dose Caution:
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The detector should be routinely checked for contamination and
decontaminated if necessary after use to avoid possibility of radioactive
contamination.
THEORY OF THE HEMISPHERICAL DETECTOR OPERATION
The resolution of the wide band semiconductor detectors, such as CT or CZT
detectors optimized by choosing a small hemispherical crystal geometry with a
positive contact at the center of the flat surface and the outer spherical surface
grounded (see fig. 4). The electric field is essentially radial and therefore much
stronger near the positive contact. Assume first that only electron charge collection
occurs with no appreciable electron carrier trapping. The pulse that is registered from
a photoelectric event with a constant number of electrons produced would arise mainly
from the induced charge from the electron carriers traversing the high field region.
Even so, gamma photoelectric interactions in the lower field region (cross hatched)
constitute the majority of the peak area (cross hatched) since this is where the majority
of the detector volume resides. The electron carriers from throughout the detector
volume drift toward the positive electrode reaching their highest velocity near the
positive electrode. The electron collection time is less then 0.5 ms.
Fig. 4 - Cross sectional view of a hemispherical detector showing the drift of electrons toward a
positive “point“ electrode and the resulting induced charge pulse. The majority of the induced
pulse arises from electrons originating in the cross-hatched region of the hemisphere.
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The pulse height from a gamma interaction does not appreciably depend on holes
collection due both to the hemispherical geometry and the short pulse shaping time.
This is fortunate since hole drift velocities are an order of magnitude smaller causing
hole collection time to be typically 5 ms and hole trapping to become important. The
hole pulse height contribution tends to be very small since few holes traverse the high
field region drifting rather toward the negative hemispherical surface electrode, thus a
far smaller pulse is induced and the pulse shaping time of about 1 ms “clips“ this pulse
contribution well before it reaches its full height. The 1 ms shaping time does no
clipping to the electron collection signal. The CZT or CT detector resolution is limited
primarily by trapping of holes due to impurities and inhomogeneities in the crystal.
Manufacturing of detectors with ideal hemispherical geometry is labor-consuming
process. Therefore in detection units are used quasi-hemispherical detectors. The
appearance of such detectors is shown in fig. 5. Researches have shown that the
replacement of ideal hemispherical geometry of the detector on quasi-hemispherical a
little bit worsens the spectrometer performance.
contacts
Fig. 5 - Appearance of a quasi-hemispherical detector.
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Digital Miniature Multi-channel Spectrometric Device MCA-527
The MCA527 is a battery powered high performance 8K Multi-Channel Analyzer/MultiChannel Scaler module with the performance of a laboratory grade MCA. High voltage
supply for detector and preamplifier power supply are integrated as well as an internal
coarse amplifier and digital filtering and analysis. Together with a detector it forms a
small-size gamma spectroscopy system, which is well suited to the demands of field
measurements for international safeguards, environmental monitoring, nuclear waste
treatment facilities, radioactive transport control and similar applications
Hardware specification
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Amplifier:
 Coarse amplifier prefilter with amplifications in steps of 1-2-5-10, corresponding
to a full scale ADC;
 Input signal positive or negative;
 linearity better than 0.1%.
ADC:
 14bit, 10 MSps;
 Integral Nonlinearity <0.05%;
 temperature stability TK 50.
Digital signal processing:
 double differential trigger filter, or single differential low energy low count rate
trigger filter;
 Pile-up-suppression, pulse pair resolution ~400ns, depending on trigger filter;
 Automated and manual adjustment of trigger threshold;
 Channel splitting 128, 256, 512, 1k, 2k, 4k or 8k;
 Differential nonlinearity <1% for 4k channels and 2µs peaking time;
 Automated PZC adjustment, detector decay time constants from 5µs to 1ms
can be compensated.
High voltage:
 Detector HV up to ±3.6kV, polarity depends on module inserted.
Power supply:
 Li-Ion batteries, operation time 10-25h, depending on detector connected (tbd).
Computer Interface:
 USB, RS-232 (38.4, 115.2, 307.2 kBd and 3MBd), Ethernet.
Mechanical:
 Housing 164 mm x 111 mm x 45 mm without connectors; weight 820g.
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Environmental:
 operational: at least 0 - 50 °C, eventual larger range;
humidity up to 90%, non condensing, IP42.
SpectraLineGP software package
Spectra processing of the SpectraLine software package includes calibration, peaks
parameters determination, nuclides identification, activities calculation and using the
true-coincident factors for the gamma-emission intensity correction. Non-parametric
model for pattern of the full energy peak provides a correct model for a line in any
energy range. SpectraLine software package enables to use external programs as an
additional instrument for user methodics realization of the specific spectrometric
problems.
Software for spectrometer emulation
Features:
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to execute spectra acquisition for the set time, to select interesting spectrum
sites and examine them on a separate plane, increasing or reducing scale on
horizontal and vertical;
to execute power calibration of spectra on two known energies;
to determine centroids and area of peaks with background deduction and
without background deduction;
to carry out an automatic serial spectra acquisition (not less than 100) with
automatic record on a disk;
to mark and select with color peaks or interesting spectrum areas;
to move a marker on a spectrum or interesting areas;
to make an estimation of energy resolution at one second and one tenth height
of full absorption peak;
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to print out spectrum window a on the matrix or laser printer;
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to transfer the spectrum to a software for identification of radio-nuclides and
calculation of their activity.
Gamma Analysis Software (SPECTRALINE Software)
Features:
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automatic peaks search with the required sensitivity level;
the energy, FWHM and peak pattern calibrations;
peaks parameters determination - position, FWHM, area; calculation results can
be saved to a text file;
efficiency “curves” can be obtain with the efficiency calibration;
activity calculation by various methods;
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use the true-coincident factors to correct the gamma-emission intensity;
the measured spectra and processing results saving to database for the
analysis of the specified criterions convergence of the repeated measurements;
simultaneous processing of any spectra number; the peak pattern calibration
with several spectrum peaks in different energy ranges;
numeric and visual control of the calibrations results;
any measurement tracts number;
simultaneous spectrum acquisition and visualization of all measurement tracts
attached to the computer;
adjustment of the ADC parameters;
independent control of all channels - start, stop, etc.;
support of the spectrometry devices of different developers.
Alexander Sokolov
Technical director
Baltic Scientific Instruments
Baltic Scientific Instruments

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